WHEREAS
That on 9 August 2011, in compliance with article 46, section I, of the Federal Act on Metrology and Standardisation, the Ministry of Labour and Social Welfare submitted to the National Consultative Committee for Standardisation on Occupational Safety and Health the Preliminary Draft Amendment to this Official Mexican Standard, and that the aforementioned Committee considered it correct and agreed that it be published as a Draft in the Official Journal of the Federation; That to comply with articles 69-E and 69-H of the Federal Act on Administrative Procedure, the corresponding Preliminary Draft was submitted for the consideration of the Federal Commission for Regulatory Improvement, which issued a favourable opinion on it; That on 21 September 2011, in compliance with the Agreement establishing the organisation and Operating Rules of the National Consultative Committee for Standardisation on Occupational Safety and Health, and with article 47, section I, of the Federal Act on Metrology and Standardisation, the Draft amendment to Official Mexican Standard NOM-029-STPS-2005, Maintenance of electrical installations in workplaces - Safety conditions, to become PROY-NOM-029-STPS-2011, Operation and maintenance of electrical installations in workplaces - Safety conditions, was published in the Official Journal of the Federation so that, within the 60 calendar days following that publication, interested parties could submit their comments to the Committee; That having received comments from 14 petitioners, the Committee proceeded to study them and resolved upon them in due course, this department publishing the respective responses in the Official Journal of the Federation of 13 December 2011, in compliance with article 47, section III, of the Federal Act on Metrology and Standardisation; That as a result of incorporating the comments submitted on the Draft amendment to Official Mexican Standard NOM-029-STPS-2005, Maintenance of electrical installations in workplaces-Safety conditions, to become PROY-NOM-029-STPS-2011, Operation and maintenance of electrical installations in workplaces-Safety conditions, as well as of the final review of the draft itself, various amendments were made to provide clarity, consistency and legal certainty as regards the provisions applying in workplaces, and That in view of the foregoing considerations, and since the National Consultative Committee for Standardisation on Occupational Safety and Health granted its approval, the following is issued: OFFICIAL MEXICAN STANDARD NOM-029-STPS-2011, MAINTENANCE OF ELECTRICAL INSTALLATIONS IN WORKPLACES-SAFETY CONDITIONS
CONTENTS
TRANSITIONAL PROVISIONS
Reference Guide I Safety measures for basic maintenance activities on electrical installations at voltages below 600 V
1. Purpose
To establish the safety conditions for carrying out maintenance activities on electrical installations in workplaces, so as to prevent accidents to the personnel responsible for carrying them out and to persons unconnected with those activities who could be exposed.
2. Scope
This Standard applies in all workplaces in the national territory where maintenance activities are carried out on permanent or temporary electrical installations, those carried out on overhead and underground electrical lines, and those carried out on live lines.
3. References
For the correct interpretation of this Standard, the following Official Mexican Standards in force, or those superseding them, shall be consulted:
3.1 NOM-001-SEDE-2005, Electrical Installations (utilisation).
3.2 NOM-017-STPS-2008, Personal protective equipment - Selection, use and management in workplaces.
3.3 NOM-026-STPS-2008, Safety and hygiene colours and signs, and identification of hazards from fluids conveyed in pipework.
4. Definitions
For the purposes of this Standard, the following definitions are established:
4.1 Labour authority; employment authority: The competent administrative units of the Ministry of Labour and Social Welfare that carry out inspection functions in occupational safety and health matters, and the corresponding units of the federal states and the Federal District acting in support of them.
4.2 Authorisation: The act by which the employer, or a person responsible for the maintenance of electrical installations appointed by the employer, approves in writing that trained workers carry out such work at height, in confined spaces or in substations, as well as those who handle live electrical installations.
4.3 Workplaces: All those places, such as buildings, premises, installations and areas, where activities of production, marketing, transport and storage, or provision of services, are carried out, or in which persons who are subject to an employment relationship work.
4.4 Close the circuit: The restoration of the electrical connections that energise an electrical installation.
4.5 Verification of the absence of electrical voltage: The check carried out to determine whether an electrical installation or part of it has been de-energised.
4.6 Control centre; switching centre: The place from which permanent control of the state of the electrical network or installation is exercised and from which the switching operations that shall be carried out are ordered so that operation is as safe as possible.
4.7 Elements under electrical voltage: Those that have electrical potential, that is, that are energised.
4.8 Personal protective equipment (PPE): The set of elements and devices for personal use to protect the worker from accidents and diseases that could be caused by agents or factors generated by the performance of their work activities. Where the risk analysis establishes the need to use working clothing with specific protective characteristics, this shall be considered personal protective equipment.
4.9 Confined space: A place large enough, with deficient natural ventilation, configured in such a way that a person can carry out a given task inside it, that has limited or restricted means of access or exit, that is not designed to be occupied by a person continuously and in which specific work is carried out occasionally.
4.10 Safety tag; lockout: The mechanical, electrical or visual means that prohibits switching operations being carried out on an electrical installation or on an element of it.
4.11 Present: The action of producing the records and/or documents, by any means, electronic or printed, to the labour authority that requests them, so as to establish compliance with the requirements laid down by this Standard.
4.12 Electrical installation: The set of devices such as conductors, transformers, protective devices and other fittings intended to generate, transmit or distribute electrical energy.
4.13 Work supervisor: The person who directs maintenance work on electrical installations by appointment or delegation from their superiors, being responsible for that work.
4.14 Electrical lines: All those conductors, materials and equipment making up the overhead and underground electrical installations that conduct electrical energy.
4.15 Maintenance of electrical installations: All those activities relating to the inspection, installation, removal, handling and servicing provided to electrical installations for the safe and reliable preservation of their operating and design characteristics.
4.16 Remotely operable: The element capable of being actuated without the operator being exposed to contact with the energised parts.
4.17 Live parts: The electrical components, such as busbars, terminals, conductors, among others, that are exposed, uninsulated and energised.
4.18 Employer: The natural or legal person who uses the services of one or more workers, in whose workplace there are permanent or temporary electrical installations, and who is responsible for their safety conditions.
4.19 Trained person: That worker whose training and instruction have been evidenced under the legislation in force or by means of a certification process, so as to take part in the design, calculation, construction or maintenance of a given electrical installation.
4.20 Authorised personnel: The person or persons who know and apply the safety procedures in the maintenance of electrical installations and who hold the employer's written authorisation to carry out these activities.
4.21 Exposed personnel: The person or persons who, when carrying out maintenance work on an electrical installation, may receive an electric shock or its effects as a consequence of contact with, a fault in, or approach to energised elements.
4.22 Safety procedure: The detailed and sequential way of carrying out an activity. It is set out in documents containing the purpose and scope of the activity; the way in which it shall be carried out; the identification of hazards, potential risks, possible injuries, as well as the protective equipment to be used; the functions and/or responsibilities of the workers taking part, along with the materials, equipment or work implements to be used, controlled and recorded.
4.23 Effective earthing: The intentional physical contact with the ground, through a connection or connections of conductors of sufficiently low impedance and of adequate current-carrying capacity, so as to eliminate the build-up of electrical overvoltages and conduct to earth the fault, induced or lightning currents, thereby preventing harm to persons or to the connected equipment.
4.24 Serious risk: That which compromises the physical integrity and/or the life of the workers carrying out maintenance work on electrical installations, since it may entail an electric shock and/or burns from an electric arc, by reason of failure to comply with the safety conditions provided for in this Standard, and which requires urgent attention.
4.25 Potential risk: That which may be produced by the effects of the worker's exposure to electric current, such as electric shock and burns from an electric arc.
4.26 Work zone: The place where maintenance activities on electrical installations are carried out by the workers.
5. Employer's duties
5.1 Prohibit persons under 16 years of age and pregnant women from carrying out maintenance activities on electrical installations.
5.2 Have the work plan for the workers who carry out maintenance activities on electrical installations, in accordance with Chapter 7 of this Standard.
5.3 Have the up-to-date single-line diagram of the workplace's electrical installation, based on NOM-001-SEDE-2005, or those superseding it, and the general schedule of loads installed per branch circuit, which shall be available to the personnel carrying out the maintenance of those installations.
5.4 Have the safety procedures for maintenance activities on electrical installations; for the selection and use of work equipment, machinery, tools and insulating protective implements, and for the fitting of the temporary earthing system, in accordance with Chapter 8 of this Standard.
5.5 Carry out maintenance activities on electrical installations only with trained personnel.
5.6 Provide the personnel who carry out maintenance activities on electrical installations with the work equipment, machinery, tools and insulating protective implements that guarantee their safety, according to the voltage level or supply current of the electrical installation.
5.7 Draw up and follow up a programme for the inspection and upkeep of the work equipment, machinery, tools and insulating protective implements used in maintenance activities on electrical installations, which shall contain at least the dates of performance, the person responsible for compliance and the result of its execution.
5.8 Have procedures for the inspection, upkeep, storage and replacement of the work equipment, machinery, tools and insulating protective implements used to carry out maintenance activities on electrical installations.
5.9 Provide the workers who carry out maintenance activities on electrical installations with personal protective equipment, in accordance with NOM-017-STPS-2008, or those superseding it.
5.10 Have procedures for the use, inspection, replacement, cleaning, limitations, safekeeping and final disposal of personal protective equipment, based on the manufacturer's information and in accordance with NOM-017-STPS-2008, or those superseding it.
5.11 Comply, as applicable, with the safety measures and conditions established in Chapters 9 to 12 of this Standard, so as to carry out maintenance activities on electrical installations.
5.12 Have in the work zones at least one fire extinguisher, accessible at all times, of the capacity and fire type that may arise, according to the determination of potential risks referred to in paragraph 7.2 of this Standard.
5.13 Authorise in writing trained workers to carry out maintenance activities on electrical installations at height, in confined spaces or in substations, as well as those who handle live parts.
5.14 Inform the workers who carry out maintenance activities on electrical installations about the risks to which they are exposed and about the safety measures they shall adopt for the activity to be carried out in the work zone.
5.15 Have an emergency response plan, available for consultation and application, based on Chapter 13 of this Standard.
5.16 Have a first-aid kit containing the manual and the dressing materials needed to deal with the possible emergency cases identified according to the risks to which the workers are exposed, and to attend to those injured or involved in accidents caused by electrical energy.
5.17 Provide training and instruction to the workers who carry out maintenance activities on the workplace's electrical installations, based on the safety procedures drawn up for that purpose, in accordance with Chapter 14 of this Standard.
5.18 Supervise that contractors comply with this Standard, where the employer agrees services with them to carry out maintenance work on electrical installations.
5.19 Have records of the results of the maintenance carried out on the electrical installations, which at least cover the name of the person responsible for carrying out the work; the activities performed and their results, as well as the dates on which that work was carried out.
5.20 Present the documents that this Standard requires the employer to draw up or hold.
6. Workers' duties
6.1 Check, before starting their activities, that the work equipment, machinery, tools and insulating protective implements used in maintenance activities on electrical installations are in safe and serviceable condition, and immediately report to the employer or to the safety and hygiene committee any anomaly detected that puts them at risk during their use.
6.2 Comply with the safety procedures established for carrying out their activities.
6.3 Take part in the training and instruction provided to them by the employer.
6.4 Take part in the activities in which they are informed about the risks to which they are exposed and the safety measures they shall adopt for carrying out their work.
6.5 Use the personal protective equipment provided by the employer, in accordance with the procedures for use, inspection, replacement, cleaning, maintenance, safekeeping and final disposal.
6.6 Refrain from carrying out activities that could result in accidents and/or material damage, that contravene this Standard and what the employer has established.
6.7 Notify the employer and the safety and hygiene committee in writing of incidents, accidents, unsafe conditions and acts, or of emergency situations, whether actual or potential, detected while carrying out their activities.
6.8 Follow the instructions established by the employer in the event of an emergency, in accordance with the emergency response plan.
6.9 Take part in the interviews conducted by the labour authority or, where applicable, by the verification unit.
7. Work plan and determination of potential risks
7.1 For each maintenance activity on electrical installations there shall be a work plan covering: a) The description of the activity to be carried out; b) The name of the work supervisor; c) The names of the workers taking part in the activity; d) The estimated time for carrying out the activity; e) The place where the activity will be carried out; f) Where applicable, the authorisation, which shall contain at least: 1) The name of the authorised worker; 2) The name and signature of the employer or of the person designated by the employer to grant the authorisation; 3) The type of work to be carried out; 4) The area or place where the activity will be carried out; 5) The date and time of the start of the activities, and 6) The estimated time of completion; g) The potential risks determined on the basis of paragraph 7.2; h) The personal protective equipment and the work equipment, machinery, tools and insulating protective implements required to carry out the activity; i) The safety measures required, according to the risks that may arise while carrying out the work, and j) The safety procedures for carrying out the activities.
7.2 For the determination of potential risks the following shall be taken into account, as applicable: a) The worker's exposure to the hazards relating to: 1) The installations immediately adjacent to the work zone; 2) The hazards identified outside the work zone, and 3) The hazards arising from other types of activity in the vicinity of the place where the work will be carried out; b) The consequences of the activities to be carried out in the vicinity of the place where the work will be carried out; c) The location of the electrical equipment, the safety zone and distances, according to the electrical voltage and the probable faults; d) The characteristics of the work equipment, machinery, tools and insulating protective implements to be used, and the movements to be made so as to avoid unsafe acts or conditions; e) The parts of the equipment requiring physical protection to prevent contact with live parts, such as energised lines and capacitor banks, among others; f) The switching operations to be carried out before and after the maintenance of the electrical installations, in particular those relating to the opening or closing of the protective devices and/or of the means of connection and disconnection; g) The personal protective equipment and the work equipment, machinery, tools and insulating protective implements held and those required for the type of electrical installations to be maintained; h) The safety procedures held for carrying out the activities; i) The temporary installations and their impact on the operations and activities to be carried out, where applicable, and j) The frequency with which the activity is performed.
7.3 The work plan shall: a) Be provided to the worker who will carry out the activity, and b) Be approved by the employer or by the person responsible for the occupational safety and health preventive services or by the work supervisor.
7.4 The work plan shall be reviewed and, where applicable, updated when the safety procedures are modified, or when any change is made to its content that alters the conditions under which the maintenance of the electrical installations is carried out.
8. Safety procedures for carrying out maintenance activities on installations
electrical
8.1 The safety procedures for carrying out maintenance activities on electrical installations shall provide for, as applicable, the following: a) The instruction that every electrical installation be considered energised until the absence of electrical voltage is verified by means of measuring equipment or instruments intended for that purpose; earthing is carried out to release stored energy, and the electrical installation is effectively earthed; b) The instructions for safely checking the presence or absence of electrical voltage in the equipment or electrical installations to be inspected, by means of the measuring equipment or instruments required; c) The instruction for the review and adjustment of protection coordination; d) The instructions for locking out equipment or fitting signage, padlocks or any other device, so as to ensure that the circuit remains de-energised while maintenance activities are carried out; e) The instructions for verifying, before carrying out maintenance activities, that the protective devices, where applicable, are in working condition; f) The instructions for verifying that the fixed earthing fulfils its function, or for fitting temporary earthing, before carrying out maintenance activities; g) The safety measures to be applied, where applicable, when the maintenance activities on the electrical installations are not completed within the working shift, so as to prevent injury to personnel; h) The instructions for carrying out an inspection of the work area where the maintenance was performed, after the work has been carried out, so as to make sure that it has been left clear of work equipment, machinery, tools and insulating protective implements, and i) The instructions for removing, at the end of that inspection and where applicable, the padlocks, signs or any other device used to lock out the energy and, finally, closing the circuit.
8.2 The safety procedures for carrying out maintenance activities on electrical installations shall contain the following: a) The single-line diagram with the general load schedule corresponding to the zone where the maintenance will be carried out, and b) The written authorisation granted to the workers, where applicable.
8.3 The procedures for the selection and use of work equipment, machinery, tools and insulating protective implements shall provide for the following: a) The selection according to the operating electrical voltages of the circuit, where working on live parts; b) The way of issuing them to the workers and/or of making them available for consultation; c) The instructions for their safe use; d) The instructions for their storage, transport or replacement, and e) The instructions for their inspection and maintenance.
8.4 The procedure for fitting the temporary earthing system shall provide for, at least, that: a) Conductors, elements and devices specifically designed for this purpose and of adequate conducting capacity are used; b) The earthing is connected as close as possible to the place of work and on both sides of it so that it is more effective; c) The sequence for connecting and disconnecting the earthing is observed as follows: 1) Connection: the earthing conductors are connected to the earthing system and then to the installation to be protected, by means of insulating poles or special devices, such as line conductors, busways, among others, and 2) Disconnection: the reverse is followed, that is, the earthing conductors are first removed from the installation and then disconnected from the earth electrode; d) It is ensured that all the blades of earthing disconnectors are in the closed position, where the earthing is made by means of that equipment; e) It is verified that the temporary earthing has electrical contact both with the metal parts to be earthed and with the earthing system; f) It is prevented that, while the earthing connection activities are being carried out, the worker is in simultaneous contact with two earthing circuits that are not electrically bonded, since these may be at different potentials; g) It is verified that the non-conducting metal parts of machines, equipment and apparatus with which the worker may accidentally come into contact are earthed, especially mobile ones; h) An earthed bonding jumper is fitted in the work zone before the in-service earthing is disconnected. The worker who carries out this activity shall be insulated so as to avoid becoming part of the electrical circuit, and i) Work is suspended for the duration of thunderstorms and line tests, where work is carried out on the earthing system of an installation.
9. General safety measures for carrying out maintenance work on installations
electrical
9.1 Carry out with authorised and trained personnel the maintenance work on electrical installations in hazardous places, such as at height, in confined spaces, in substations and on energised lines.
9.2 Demarcate the work zone for carrying out maintenance activities on electrical installations, or their vicinity, and fit safety signs that: a) Indicate to unauthorised persons the prohibition on: 1) Entering the substation or energising the electrical equipment or machines, and 2) Operating, handling or touching the electrical devices; b) Identify the interlocking devices from one to four padlocks, and c) Define the area under maintenance by fitting: 1) Red or orange plastic tapes, ropes or chains and snap hooks for attaching them; 2) Extendable red or orange barriers fitted with ropes at their ends for securing them; 3) Pennants; 4) Banners; 5) Red markers for the marking of the work zone, or 6) Work-clearance tags with information on who is carrying out the work, who authorises it, when it started and when the work to be carried out will finish.
9.3 Use for the maintenance of electrical installations, according to the work to be carried out and as applicable, work equipment, machinery, tools and insulating protective implements and, where necessary, one or more of the following items of equipment or materials: a) Insulating platforms or mats; b) Insulating sleeves and caps; c) Voltage detectors or discriminators of the class and voltage suited to the system; d) Insulated tools; e) Signage material, such as discs, barriers or flags, among others; f) Portable lamps, or g) Isolating transformers.
9.4 Verify, for carrying out maintenance work on electrical installations, at least that: a) The electrical installations are in accordance with the single-line diagram and the work plan; b) Working with energised conductors or equipment is avoided and, should it be strictly necessary, it is carried out where the personal protective equipment and the tools or work implements required are available; c) Workers are prohibited from wearing jewellery or metal items while carrying out the activities; d) The procedure corresponding to energised conductors or equipment is applied before carrying out any operation, so as to: 1) Interrupt the flow of electric current; 2) Verify with measuring equipment the absence of electrical voltage in the conductors or electrical equipment; 3) Earth and short-circuit the conductors and electrical equipment; 4) Apply other necessary preventive measures, such as fitting padlocks or notices, that prevent the restoration of the electric current, and 5) Protect the elements under voltage situated in the vicinity against accidental contact; e) The identification of boards, cabinets, switches, transformers, among others, as well as their electrical characteristics, is kept legible; f) The tools and personal protective equipment suited to each task are available, such as: dielectric gloves, insulating mats and blankets, in sufficient number and according to the electrical potential at which the work will be carried out; g) Portable electrical apparatus is prevented from being moved while connected to the power source; h) The use of portable electrical tools and apparatus in flammable or explosive atmospheres is avoided, unless they meet the specifications for explosion-proof equipment; i) The safety procedures required are applied, based on Chapter 8 of this Standard; j) Where open-type switchgear is used outdoors, the following is complied with: 1) Protect all elements under electrical voltage against accidental contact, by means of covers or by placing them at a height such that it does not present a risk of accidental contact; 2) Maintain the safety distances of the working space around the elements under voltage or energised, as laid down by NOM-001-SEDE-2005, or those superseding it, and 3) Protect the switchgear, transformers and other energised electrical apparatus with metal fencing that is earthed; k) The frames of the tools and of hand-held and portable apparatus are earthed, except those of double-insulated tools; l) The earthing system of the entire electrical installation is subjected to the earth resistance and continuity test at least once a year, and its values are recorded; m) An inspection is carried out of the whole circuit or electrical network on which the maintenance was performed, after the work has been carried out; n) The circuits, conductors or equipment are energised, after any work has been carried out, only on the order of the work supervisor, and o) An earth-fault protection switch is provided to protect the workers when they carry out maintenance activities.
9.5 Comply, where portable tools or lamps are used in the maintenance of low-voltage electrical installations, with the following safety conditions: a) The supply cables of the portable tools or lamps are perfectly insulated and in good condition; b) Supply voltages of 24 volts or less are used, in the case of portable tools and lamps for work in trenches, pits, galleries and boilers, among others; c) Portable lamps are provided with an insulating handle, a device protecting the bulb and a heavy-duty or extra-heavy-duty insulated conductor, and d) At least one of the following conditions is met in those cases where the portable tool has to operate at an electrical voltage above 24 volts: 1) Use insulating dielectric gloves; 2) Have double insulation in the portable tool; 3) Have an earthing connection; 4) Have protection against insulation defects of the tool by means of residual-current devices, or 5) Use isolating transformers.
10. Safety conditions in the maintenance of electrical installations
10.1 On the electrical equipment being maintained, the following shall be complied with, as applicable: a) The switches are contained in enclosures that make accidental contact by persons and objects impossible in any case; b) The opening and closing of switch blades, disconnectors, fuse-switches and other similar devices is carried out by authorised personnel, using personal protective and safety equipment, according to the potential risks identified. Examples of personal protective equipment are: dielectric gloves, according to the class and to the electrical voltage; eye protection; safety helmet; working clothing, and dielectric boots, among others, and c) The connection of any electrical installation - new or temporary - or of equipment to energised lines or circuits is invariably carried out with the circuit de-energised. Where the circuit cannot be de-energised, the procedure for live-line work drawn up for that purpose shall be applied.
10.2 In electrical installations it shall be verified, as applicable, that: a) All equipment intended for the use and distribution of electrical energy has information identifying the electrical characteristics and the safety distance for the electrical voltages present, whether on a plate, on adhesive labels or marked on the equipment; b) In places where contact with electrical equipment or proximity to it may entail danger to the workers, safety signage is provided, in accordance with NOM-026-STPS-2008, or those superseding it, so as to indicate the risks and the use of personal protective equipment; c) The energised elements are out of the workers' reach; d) The work zone is demarcated by using, among others, the following means: 1) Protective barriers; 2) Guards; 3) Demarcation tapes, and 4) Access control; e) Energised conductors are handled with dielectric gloves or with insulated tools designed for the electrical voltage level handled; f) All cables are protected against damage, especially those exposed to loads from vehicles or heavy mechanical equipment; g) It is complied with, on the covers of equipment or of fixed devices, that their opening interrupts the electrical voltage, by means of a special tool or key; h) Bare cables and other exposed energised elements are effectively protected, when they are installed, by means of fencing or protective screens, or the safety distances referred to in NOM-001-SEDE-2005, or those superseding it, are complied with; i) The use of metal items such as tape measures, rods, tubes, sections, as well as radiocommunication equipment with an aerial, is prohibited in the vicinity of energised electrical installations; j) Storing materials of any kind on electrical installations is avoided, and k) Access to the boards or to the connection or disconnection points of the electrical installation is kept clear of obstacles.
10.3 In electrical substations, at least the following safety measures shall be adopted: a) The authorisation to carry out work in the substation is obtained; b) The personal protective equipment needed to carry out the work in the substation is used; c) The maintenance activities in the electrical substation are carried out with at least two workers; d) All equipment located in the electrical substation is considered energised until the absence of electrical voltage is verified and it is effectively earthed, before starting the maintenance; e) The safety procedures established for the maintenance and those required are applied, in accordance with Chapter 8 of this Standard; f) The safety notices are observed; g) Calibration and test equipment holding a calibration certificate in force is used; h) The manual operating levers, access doors, control equipment cabinets, among others, as the case may be, are kept with a padlock or with a safety tag indicating that they are being operated or that some work is being carried out on them; i) It is ensured that the live parts of the electrical substation are out of the personnel's reach or protected by screens, grilles, mesh or other similar means, and j) The emergency exit is identified and it is ensured that the doors open: 1) Outwards or are sliding; 2) Easily from the inside, and that they are clear of obstacles, and 3) From the outside only with a special or controlled key.
10.4 On the equipment or devices of the temporary electrical installations being maintained, it shall be verified that: a) The safety measures are applied, where there are uninsulated energised lines close to walls; b) It is checked that they are de-energised and earthed; c) It is verified that there is no damage to the insulation of the conductors; d) The joints have the mechanical strength to maintain the continuity of the circuit, and e) Electrical continuity is maintained in all welds or joints.
10.5 For carrying out work within the perimeter of the electrical installations, it shall be verified that: a) The safety distance corresponding to the electrical voltage of the installation is maintained before carrying out any maintenance operation on the conductors or electrical installations. To establish the safety distance, NOM-001-SEDE-2005, or those superseding it, shall be applied; b) Maintenance operations at less than the working distance on a conductor or electrical installation are prevented while that conductor or electrical installation has not been de-energised, or while the safety measures indicated in this Standard have not been applied, and c) The safety measures are adopted and the specific instructions given for preventing occupational risks, where it is not possible to disconnect a conductor or item of equipment of an electrical installation in whose vicinity maintenance operations are to be carried out. Those measures shall include at least the following: 1) Fit insulating protection, padlocks or safety tags on the energised conductors and installations, as appropriate, and 2) Control, where applicable, the movement of the mobile equipment used for maintenance in the vicinity of conductors or equipment of an electrical installation that cannot be disconnected, so as to avoid the risk of contact.
10.6 For temporary electrical installations, at least the following safety measures shall be followed: a) Request in writing from the work supervisor of the switching centre or control centre the authorisation to fit temporary electrical installations; b) Inform the work supervisor of the switching centre or control centre in writing of all the temporary modifications made and tags fitted, so that they may be removed or converted into permanent installations; c) Use the temporary electrical installations only for the purpose for which they were designed; d) Remove the temporary installations once the purpose for which they were fitted has ended, in accordance with NOM-001-SEDE-2005, or those superseding it, and e) Remove the earthing in accordance with NOM-001-SEDE-2005, or those superseding it.
11. Safety measures for carrying out maintenance work on electrical installations
overhead and underground
11.1 Apply the corresponding procedures based on Chapter 8 of this Standard.
11.2 Verify that, in addition to the general safety measures established in Chapter 9 of this Standard, the following is complied with: a) The maintenance activities on the electrical installations are carried out only with personnel authorised and trained for that purpose; b) The disconnection of lines or equipment from the electrical power source is carried out by first opening the equipment designed to operate under load; c) For the opening or closing of energised gang-operated switch blades, the following is carried out: 1) Verify that the operating handle is switched to earth; 2) Use personal protective equipment suited to the activity, and 3) Use insulating mats, blankets or covers, where there is excessive damp on the ground; d) The absence of electrical voltage is verified before starting the work; both sides of the lines are short-circuited and earthed as close as possible to the place of work, and it is ensured that the earthing is of adequate size to carry an earth fault safely, maintains electrical continuity and a sufficiently low impedance; e) Protective barriers and safety signs or notices are fitted in the work zone where the connection/disconnection and/or protective devices are located; f) A warning notice bearing the wording "Danger, do not energise" and physical locks such as padlocks are fitted at the level of the sectionalising device or on the handle of the device, where switches, reclosers and switch blades located on the public highway are opened or where the equipment is remotely operable; g) It is verified that all the possible supply sources in the work zone are open; h) Protective covers are fitted for the pole and/or for the conductor, according to the corresponding electrical voltage level, where a pole is installed or removed between energised lines or near them. The workers shall use dielectric gloves for the electrical voltage required, as well as rawhide or leather gloves for handling the pole; i) The metal structure of the lorry used to place or remove a pole between energised lines or near them is earthed. The workers shall not touch the vehicle while standing on the ground, unless the operations have been completed or the activity is stopped; j) For replacing fuses in high-voltage lines, the following is carried out: 1) The absence of electrical voltage is verified before starting the work and, where applicable, both sides of the lines are short-circuited and earthed as close as possible to the place of work; 2) It is verified that the fault has been corrected; 3) The safety distance is maintained. Fuse cut-outs, when open on the load side, are considered energised and, to replace them, they must be earthed; 4) The head is inclined slightly downwards at the moment of closing a fuse cut-out, so as to be protected from the electric arc and possible ejection of particles that may occur. For this activity a safety helmet with chin strap for electrical use, safety boots without a metal toe cap, dielectric gloves, cotton working clothing and safety spectacles shall be used, and 5) The continuity of the earthing connections and of the earthing conductors is verified; k) The drum supplying the conductor has an earthing connection, where a conductor is run near another energised conductor or conductors. The worker attending the drum shall work on an insulated platform and use insulating gloves, according to the voltage level; l) It is verified, on lines mounted on the same supports, along all or part of their run, that: 1) Carrying out work and operations on a line by the procedure known as "agreed time" is prohibited; 2) Carrying out work is avoided, or work is suspended, when there are thunderstorms, and 3) Carrying out work on a line with two or more circuits while one of them is under electrical voltage is prevented, if performing it requires moving the conductors, insulators or mechanical supports in such a way that contact could be made with the other circuit, and m) It is ensured that no worker remains on the line, and that no tools are left at the place of work, on completing the activities and before removing the earthing connections. The earthing connections shall then be removed, in the reverse order to that followed in fitting them.
11.3 For maintenance work on underground lines, the safety measures provided for in paragraph 11.2 of this Standard shall be adopted, as applicable, as well as the following: a) Identify the location of the equipment as indicated by the drawings; b) Locate the routes, supply circuits, transformers, disconnectors and switches; c) Determine the preventive measures for carrying out the tasks according to the risks present at the time of carrying out the work, and d) Verify the condition and the electrical continuity of the earthing connections and of the earthing conductors.
12. Safety measures for carrying out maintenance work on electrical installations
live
12.1 Comply with the safety procedures referred to in paragraphs 8.1 to
8.3 of this Standard, for carrying out maintenance work on energised electrical installations, as well as with the following safety instructions: a) Carry out the activity with authorised and trained workers; b) Comply with the technique described in the procedures of the work plan and use the tools and implements needed to carry out the activity, as well as the personal protective equipment suited to the risk; c) Follow the sequence for carrying out the switching operations, such as the connection and/or disconnection of sectionalising and protective devices, the transfer of lines, the fitting of temporary jumpers, the isolation of networks, among others; d) Use the means of communication, where applicable, with the substation, the switching centre or the work supervisor; e) Carry out the handover and acceptance of the work zone for the start and completion of the activities, respectively, and f) Have permanent supervision while the work is carried out.
12.2 Comply, for carrying out maintenance work on energised electrical installations, with the following: a) Hold a meeting before the start of the activities, in the work zone, so as to carry out an analysis of the conditions of the place, taking into account at least the following: 1) The networks close to the work zone; 2) The correct positioning of the vehicle, and 3) The earthing of the vehicle; b) Prohibit live-line work on faulted circuits, on rainy days or where the material and equipment needed are not available; c) Have a programme for the inspection and maintenance of vehicles, equipment and tools, so as to verify that they meet the insulation level required; d) Verify that the protective and/or automatic sectionalising equipment, or the remotely operable equipment, is in such a state that live-line work can be carried out; e) Always use the personal protective equipment and the live-line working equipment of the class corresponding to the electrical voltage level of the installation where the work will be carried out, and f) Carry out the work on one phase at a time, keeping the others away and/or covered.
13. Emergency response plan
13.1 The emergency response plan shall contain, at least, the following: a) The person responsible for implementing the plan; b) The equipment or apparatus needed to carry out the plan; c) The procedures for: 1) Communicating the emergency, together with the directory of the assistance services for the emergency, rescue and hospitals, among others; 2) Suspending the activities, including the immediate actions for disconnecting the energy source; 3) Eliminating the risks during and after the emergency; 4) Using the rescue systems and equipment, where applicable; 5) Attending to and transferring the casualties to places of medical care, which shall at least indicate: i) The specific instructions, in a visible place, on what to do in the event of an accident; ii) The instructions for removing the injured person from immediate danger; placing the casualty in a safe place; giving first aid, where applicable; applying cardiopulmonary resuscitation (CPR) techniques, and those for calling the assistance services, and iii) The nearest hospitals or medical units for transferring the casualty, and 6) Resuming activities, where applicable, and d) The training and instruction of the workers in relation to the content of the emergency response plan.
14. Training
14.1 The workers who carry out the maintenance of the workplace's electrical installations shall be provided with training, instruction and information, according to the tasks assigned and the emergency response plan.
14.2 The training of the workers who carry out the maintenance of electrical installations shall take into account at least the following: a) The information on the occupational risks relating to the maintenance of electrical installations; b) The general description of the effects on the body caused by an electric shock or its effects, as a consequence of contact with, a fault in, or approach to energised elements, with emphasis on the conditions that shall be avoided so as to prevent injury or harm to health; c) The safety procedures for carrying out the maintenance of electrical installations referred to in Chapter 8 of this Standard; d) The safety measures established in this Standard, applicable to the activities to be carried out, and which shall be adopted while carrying out the activities or work of maintenance of the electrical installations; e) The use, maintenance, upkeep, storage and replacement of personal protective equipment, in accordance with NOM-017-STPS-2008, or those superseding it; f) The theoretical and practical topics on the safe way of handling, maintaining, inspecting and storing the machinery, equipment, tools, materials and work implements; g) The conditions under which the machinery, equipment, tools, materials and work implements shall be taken out of service for repair or replacement; h) The weather conditions or other unfavourable factors that would make it necessary to interrupt the work, and i) The content of the emergency response plan and other actions arising from the emergency situations that could arise while the maintenance work on the electrical installations is carried out.
15. Verification units
15.1 The employer shall have the option of engaging an accredited and approved verification unit, under the Federal Act on Metrology and Standardisation and its Regulations, to verify the degree of compliance with this Standard.
15.2 Verification units assessing conformity with this Standard shall apply the compliance criteria established in the conformity assessment procedure of Chapter 16 of this Standard.
15.3 Accredited and approved verification units assessing compliance with this Standard shall issue a report, which shall contain: a) Employer data: 1) The name, denomination or business name; 2) The full address, and 3) The name and signature of the employer and, where applicable, of the legal representative, and b) Verification unit data: 1) The name, denomination or business name; 2) The registration number granted by the accreditation body; 3) The approval number granted by the Ministry of Labour and Social Welfare; 4) The dates on which the accreditation and approval were granted; 5) The result of the verification; 6) The name and signature of the person responsible for issuing the report; 7) The place and date of signature of the report; 8) The period of validity of the report, and 9) The registration number of the report granted by the Ministry of Labour and Social Welfare when the respective return is filed.
15.4 The reports issued by verification units shall be valid for one year, provided that the conditions on which they were issued are not modified.
16. Conformity assessment procedure
16.1 This conformity assessment procedure applies both to inspection visits carried out by the labour authority and to verification visits carried out by verification units.
16.2 The verification report in force shall be available to the labour authority when it so requests.
16.3 The aspects to be verified during the conformity assessment of this Standard shall be examined, as applicable, by physical inspection, documentary review, records or interviews, as follows: Type of
Provision Acceptance criterion Observations Risk
assessment
5.1 (conformity) Interview The employer complies when, on interviewing the Serious workers selected according to the sampling criterion of Table 1 of paragraph 16.4, it is established that in the workplace persons under 16 years of age and pregnant women are prohibited from carrying out maintenance activities on electrical installations.
Physical The employer complies when, on carrying out a Serious
walk-through of the workplace, it is established that there are no persons under 16 years of age or pregnant women carrying out maintenance activities on electrical installations.
5.2 (conformity, 7.1) and 7.1 Documentary The employer complies when: ¾ It presents documentary evidence that it has a work plan for each maintenance activity on electrical installations for the workers who carry out that work; ¾ The work plan covers: 9 The description of the activity to be carried out; 9 The name of the work supervisor; 9 The names of the workers taking part in the activity; 9 The estimated time for carrying out the activity; 9 The place where the activity will be carried out; 9 Where applicable, the authorisation, which contains at least:
o The name of the authorised
worker; o The name and signature of the employer or of the person designated by the employer to grant the authorisation;
o The type of work to be
carried out; o The area or place where the activity will be carried out; o The date and time of the start of the activities, and
o The estimated time of
completion; Type of
Provision Acceptance criterion Observations Risk
assessment
9 The potential risks
determined on the basis of paragraph 7.2; 9 The personal protective equipment and
insulating implements required to carry out the activity; 9 The safety measures required, according to the risks that may arise while carrying out the work, and 9 The safety procedures for carrying out the activities.
| the equipment | of work, |
| machinery, | tools and |
| implements | of protection |
5.2 (conformity, 7.2) and 7.2 Documentary The employer complies when it presents documentary evidence that for the determination of potential risks it takes into account, as applicable, the following: ¾ The worker's exposure to the hazards relating to: 9 The installations immediately adjacent to the work zone; 9 The hazards identified outside the work zone, and 9 The hazards arising from other
types of activity in the
vicinity of the place where the work is carried out; ¾ The consequences of the activities to be carried out in the vicinity of the place where the work is carried out; ¾ The location of the electrical equipment, the safety zone and distances, according to the electrical voltage and the probable faults; ¾ The characteristics of the work equipment, machinery, tools and insulating protective implements to be used, and the movements to be made
so as to avoid unsafe acts or
conditions; ¾ The parts of the equipment requiring
physical protection to prevent
contact with live parts, such as
energised lines and capacitor
banks, among others; ¾ The switching operations to be carried out before and after the maintenance of
the electrical installations, in particular those relating to the
opening or closing of the protective devices and/or of the means of connection and disconnection; ¾ The personal protective equipment and the
work equipment, machinery, tools and insulating protective
implements held and those required for the type of electrical installations to be maintained; ¾ The safety procedures held for carrying out the activities; ¾ The temporary installations and their
impact on the operations and
activities to be carried out, where applicable, and ¾ The frequency with which the activity is performed.
5.2, 7.3 a) Interview The employer complies when, on interviewing the
workers selected according to the sampling criterion of Table 1 of paragraph 16.4, it is established that the work plan is provided to the worker who carries out the activity. Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that the work plan is provided to the worker who carries out the activity.
5.2, 7.3 b) and 7.4 Documentary The employer complies when it presents
documentary evidence that the work plan: ¾ Is approved by the employer or by the
person responsible for the
preventive occupational safety and health services or by the work supervisor, and ¾ Is reviewed and, where applicable, updated
when the safety procedures are
modified, or when any change is
made to its content that alters the
conditions under which the
maintenance of the electrical installations is carried out.
| the electrical installations, | in |
| particular those relating to | the |
equipment of work, machinery,
tools and implements of5.3 (conformity) Documentary The employer complies when: ¾ It presents documentary evidence that it has the up-to-date single-line diagram of the workplace's electrical installation, based on NOM-001-SEDE- 2005, or those superseding it, and the general schedule of loads installed per branch circuit, and
¾ The single-line diagram contains the
following: 9 The area in square metres of the building or other structure supplied by each feeder; 9 The total connected load before applying the demand factors;
9 The demand factors
applied; 9 The calculated load after applying the demand factors; 9 The type, nominal size and length of the conductors used, and 9 The voltage drop of each branch circuit and feeder circuit. Interview The employer complies when, on interviewing the workers selected according to the sampling criterion of Table 1 of paragraph 16.4, it is established that the single-line diagram is available to the personnel who carry out the maintenance of the electrical installations.
5.4 (conformity) and 8 Documentary The employer complies when it presents documentary evidence that: ¾ It has the safety procedures for: 9 The maintenance activities on the electrical installations; 9 The selection and use of the work equipment, machinery, tools and insulating protective implements, and 9 The fitting of the temporary earthing system; ¾ The safety procedures for
carrying out the maintenance
activities on the electrical installations provide for, as applicable, the following:
9 The instruction that every
electrical installation is considered energised until the verification of the absence of
that purpose; earthing is carried out to release stored
energy, and the electrical
installation is effectively earthed; 9 The instructions for safely checking the presence or absence of electrical voltage in the equipment or electrical installations to be inspected, by means of the measuring equipment or instruments required; 9 The instruction for the review
and adjustment of protection
coordination; 9 The instructions for locking out equipment or fitting signage,
padlocks or any other
device, so as to ensure
that the circuit remains
de-energised while maintenance activities are carried out; 9 The instructions for verifying, before carrying out activities of
maintenance, that the
protective devices, where applicable, are in working condition; 9 The instructions for verifying that the fixed earthing fulfils its function, or for fitting temporary earthing, before
carrying out activities of
maintenance; 9 The safety measures to be applied, where applicable, when the activities are not completed within the
working shift, so as to prevent injury to personnel; 9 The instructions for carrying out an inspection of the work area
where the maintenance was
performed, after the work has been carried out, so as to make sure that it has been
left clear of work equipment,
machinery, tools
and insulating protective
implements, and 9 The instructions for removing, at the end of that inspection and where applicable, the padlocks,
signs or any other
device used to lock out the energy and, finally, closing the circuit; ¾ The safety procedures for carrying out the maintenance activities on the electrical installations contain the following: 9 The single-line diagram with the
general load schedule
corresponding to the zone where the maintenance is carried out, and
9 The written authorisation
granted to the workers, where applicable; ¾ The procedures for the selection
and use of the work equipment, machinery, tools and
protective insulating implements provide for the following: 9 The selection according to the operating electrical voltages of the circuit, where working on live parts; 9 The way of issuing them to the
workers and/or that they are
available for consultation; 9 The instructions for their safe use;
9 The instructions for their storage, transport or
replacement, and 9 The instructions for their inspection and maintenance, and ¾ The procedure for fitting the temporary earthing system provides for, at least, that:
9 Conductors, elements and devices
specifically designed for this purpose and of adequate conducting capacity are used; 9 The earthing is connected as close as possible to the place of work and on both sides of it so that it is more effective; 9 The sequence for connecting and disconnecting the earthing is observed as follows: o Connection: the earthing conductors are connected to the earthing system and then to the installation
to be protected, by means of insulating poles or
special devices to the installation to be
protected, such as
line conductors or busways, among others, and o Disconnection: the reverse is followed,
that is,
the earthing conductors are first removed from the installation and then disconnected from the earth electrode; 9 It is ensured that all the blades of earthing disconnectors are in the closed position, where the earthing is made by means of that equipment; 9 It is verified that the temporary earthing has electrical contact both with the metal parts to be earthed and with the earthing system; 9 It is prevented that, while the earthing connection activities are being carried out, the worker is in simultaneous contact with two earthing circuits that are not electrically bonded, since these may be at different potentials; 9 It is verified that the non-conducting metal parts of machines, equipment and apparatus with which the worker may accidentally come into contact
are earthed,
especially mobile ones;
9 An earthed bonding The worker who
jumper is fitted in the carries out this activity
work zone before the is insulated so as to avoid
disconnection of the in-service becoming part of the earthing, and electrical circuit. 9 Work is suspended for the duration of thunderstorms and line tests, where work is carried out on the earthing system of an installation.
| voltage | electrical, | by means of |
| equipment | or instruments | of |
| measurement | intended | for that |
| to be protected, | by means of |
| insulating poles or | devices |
are completed the activities of
maintenance of the
installations electrical in the and use of the equipment of work,
machinery, tools and 9 The instructions for their
storage, transport or 9 Conductors, elements
and devices are used5.5 (conformity) Documentary The employer complies when it presents evidence Serious documentary that it carries out the activities
of maintenance of the electrical
installations only with trained personnel.
5.6 (conformity) The employer complies when:
Physical ¾ On carrying out a walk-through of the Serious workplace, it is established that it
provides the personnel who carry out the maintenance activities on the electrical installations with the work equipment, machinery, tools and insulating protective implements that guarantee their safety, according to the
voltage level or supply current of the electrical
installation, or
Interview ¾ On interviewing the workers Serious
selected according to the sampling criterion of Table 1 of
paragraph 16.4, it is established that
it provides the personnel who carry out the maintenance activities on the electrical installations with the work equipment, machinery, tools and insulating protective implements that guarantee their safety, according to the
voltage level or supply current of the electrical
installation.
| level of | voltage | or | current of |
| supply | of | the | installation |
| level of | voltage | or | current of |
| supply | of | the | installation |
Physical ¾ On carrying out a walk-through of the workplace Serious
, it is established that5.7 (conformity) Documentary The employer complies when it presents documentary evidence that:
¾ It draws up and follows up a
programme for the inspection and upkeep of the work equipment, machinery,
tools and insulating protective
implements used in the maintenance activities on the electrical installations, and
¾ The programme for the inspection and
upkeep of the work equipment,
machinery, tools and
insulating protective implements contains at least: 9 The dates of performance,
9 The person responsible for its
compliance, and 9 The result of its execution.
5.8 (conformity) Documentary The employer complies when it presents evidence
documentary that it has
procedures for the inspection, upkeep, storage and replacement of the work
equipment, machinery, tools and
insulating protective implements, so as to carry out the maintenance activities on the electrical installations.
5.9 (conformity) The employer complies when: It is valid for the employer to present another
Physical ¾ On carrying out a walk-through of the Serious
methodology, different
workplace, it is established that it is
from that contained in provided to the workers who NOM-017-STPS-2008, carry out maintenance activities
for selecting the
on the electrical installations, the personal protective
equipment of personal protection, equipment of the
in accordance with NOM- workers who
017-STPS-2008, or those
carry out activities of superseding it, or maintenance of the
Interview ¾ On interviewing the workers, electrical installations Serious
selected according to the , for example that contained in the sampling criterion of Table 1 of the NFPA-70E, Standard
paragraph 16.4, it is established that for electrical safety in
it provides the workers who the workplace, 2010 carry out maintenance activities edition. on the electrical installations with the
personal protective equipment
in accordance with NOM-
017-STPS-2008, or those
superseding it.
equipment of protection personal,
personnel of the5.10 (conformity) Documentary The employer complies when it presents evidence
documentary that it has procedures for the use, inspection,
replacement, cleaning, limitations, safekeeping and final disposal of the personal protective equipment, based on the manufacturer's information, and in accordance with NOM-017-STPS-2008, or those superseding it.
| documentary | that | it | has | the |
| procedures | for | the | use, | inspection, |
5.11 (conformity, 9) and 9 Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that for carrying out activities of
maintenance of the electrical
installations the following safety measures are adopted, as applicable
¾ It carries out with authorised and Serious trained personnel the work of
maintenance of the electrical installations in hazardous places, such as at height, in confined spaces, substations and energised lines;
¾ It demarcates the work zone for Serious
carrying out maintenance activities on the electrical installations, or in their vicinity, and fits safety signs that: 9 Indicate to unauthorised persons the prohibition on: o Entering the substation or
energising the electrical
equipment or machines, and o Operating, handling or touching the electrical devices;
9 Identify the interlocking
devices from one to four padlocks, and 9 Define the area under maintenance by fitting: o Red or orange plastic
tapes, ropes or chains and snap hooks
for attaching them; o Extendable red or orange barriers fitted with ropes at their ends for securing them; o Pennants; o Banners; o Red markers for the marking of the work zone, or 9 o Work-clearance tags with
information on who is carrying out the work,
who authorises it, when it started and when the work to be carried out will finish;
¾ It uses for the maintenance of the Serious
electrical installations, according to the work to be carried out and as applicable,
where necessary, one or more of the following items of equipment or materials: 9 Insulating platforms or mats; 9 Insulating sleeves and caps; 9 Voltage detectors or discriminators of the class and voltage suited to the system; 9 Insulated tools; 9 Signage material, such
as discs, barriers or
flags, among others; 9 Portable lamps, or 9 Isolating transformers; ¾ It verifies, for carrying out maintenance work on the electrical installations, at least that: 9 The electrical installations are in accordance with the single-line diagram and the work plan; 9 Working with energised conductors Serious or equipment is avoided and, should
it be strictly
necessary, it is carried out where
the personal protective
equipment and the tools or work
implements required
are available; 9 Workers are prohibited from Serious
wearing jewellery or metal
items while carrying out the activities;
9 The corresponding procedure
is applied to energised conductors or equipment, before carrying out any operation, so as to: o Interrupt the flow of electric current; o Verify with measuring equipment the absence of electrical voltage in the
conductors or electrical
equipment;
o Earth and short-circuit
the conductors and electrical equipment;
o Apply other necessary
preventive measures, such as fitting padlocks or
notices, that prevent the restoration of the
electric current, and o Protect the elements under voltage situated in the vicinity against accidental contact;
transformers, among others, as
well as their electrical
characteristics; 9 The tools and personal protective Serious equipment suited to each task are available, such
as: dielectric gloves,
insulating mats and blankets, in sufficient number and according to the electrical potential at which the work will be carried out; 9 Portable electrical apparatus is Serious prevented from being moved while connected to the power source; 9 The use of portable electrical Serious tools and apparatus in
flammable or explosive
atmospheres is avoided, unless they meet the specifications for explosion-proof equipment; 9 The safety procedures required are applied, based on Chapter 8 of this Standard; 9 It is complied with, where Serious
open-type switchgear is used
outdoors, with the following: o All elements under electrical voltage are protected
against accidental contact, by means of covers or by placing them at a height such that it does not present a risk of accidental contact; o The safety distances of the working space are maintained around the elements under voltage or
energised, as laid down
by NOM-001- SEDE-2005, or those superseding it, and o The switchgear, transformers and other energised electrical apparatus are protected with metal
fencing that is
earthed; 9 The frames of the tools and of Serious hand-held and portable apparatus are earthed, except those of double-insulated tools;
9 The earthing system of the Serious
entire electrical installation
is subjected to the earth resistance and
continuity test at least once a year, and its values are recorded; 9 An inspection is carried out of the whole circuit or electrical network on which the maintenance was performed, after the work has been carried out;
9 The circuits, conductors or
equipment are energised, after any work has been carried out, only on the order of the work supervisor, and 9 An earth-fault protection switch is provided to protect the workers when they carry out maintenance activities, and
¾ It complies, where portable tools or
lamps are used in the maintenance of low-voltage electrical installations, with the following safety conditions: 9 The supply cables of the portable tools
or lamps are
perfectly insulated and in good condition;
9 Supply voltages of
24 volts or less are used, in the case of portable tools and lamps for
work in trenches, pits,
galleries and boilers, among others; 9 Portable lamps are provided with an insulating handle, a device protecting the bulb and a heavy-duty or extra-heavy-duty insulated conductor, and 9 At least one of the following conditions is met in those cases where the portable tool has to
operate at an electrical
voltage above 24 volts:
o Use insulating dielectric
gloves; o Have double insulation in the portable tool;
o Have an earthing
connection; o Have protection against insulation defects of the tool by means of residual-current devices, or
9 o Use isolating
transformers.
| equipment of | work, | machinery, |
| tools | and implements | of |
| protection | insulating and, | where |
| notices, that | prevent | the |
| restoration | of | the |
| electrical to the test | of |
| earth resistance and | of |
¾ It carries out with authorised and Serious
trained personnel the work of plastic of colour red or
orange and snap hooks 9 The identification of boards is
kept legible,
cabinets, switches, o All the elements under
voltage are protected5.11 (conformity, 10) and 10 Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that for carrying out activities of
maintenance of the electrical
installations the following safety conditions are in place: ¾ On the electrical equipment being maintained, as applicable: 9 The switches are contained in enclosures that make accidental contact by persons and objects impossible in any case; 9 The opening and closing is carried out of Example of the Serious
others.
electrical installation - new or
temporary - or of equipment to energised lines or circuits, invariably with the circuit de-energised. Where the circuit cannot be de-energised,
the procedure for
live-line work drawn up for that purpose is applied; ¾ In the electrical installations it is verified, as applicable, that: 9 All equipment intended for the use and distribution of electrical energy has information identifying the electrical characteristics
and the safety distance for the electrical voltages
present, on a
plate, on adhesive labels or marked on the equipment; 9 The places where contact
workers, safety signage is
provided, in accordance
with NOM-026-STPS-2008, or those superseding it, so as to indicate the risks and the use of personal protective equipment; 9 The energised elements are out of the workers' reach; 9 The work zone is demarcated
by using, among
others, the following means: o Protective barriers; o Guards; o Demarcation tapes, and o Access control; 9 Energised conductors are handled
with dielectric gloves
or with insulated tools designed for the electrical voltage level handled; 9 All cables are protected against damage,
especially those
exposed to loads from vehicles or heavy mechanical equipment; 9 It is complied with, on the covers of equipment or of fixed devices, that their opening interrupts the electrical voltage, by means of a special tool or key;
energised, when they are installed, by means of fencing or protective screens, or the safety distances referred to in NOM-001-SEDE-2005, or those superseding it, are complied with;
9 The use of metal items such Serious
as tape measures, rods, tubes, sections, as well as radiocommunication equipment with an aerial, is prohibited in the vicinity of energised electrical installations; 9 Storing materials of
any kind on the
electrical installations is avoided, and 9 Access to the boards or to the connection or disconnection points of the electrical installation is kept clear of obstacles;
¾ In the electrical substations it Serious
adopts at least the following safety measures: 9 The authorisation is obtained to
carry out work in the
substation; 9 The personal protective equipment needed to carry out the work in the substation is used; 9 The maintenance activities are carried out in the electrical
substation with at least two
workers; 9 All equipment located in the electrical substation is considered energised until the absence of electrical voltage is verified and it is
effectively earthed,
before starting the maintenance; 9 The safety procedures established for the
maintenance and those
required are applied, in accordance with Chapter 8 of this Standard;
9 The safety notices are
observed;
9 Calibration and test
equipment holding
a calibration certificate in force
is used; 9 The manual operating levers,
access doors,
control equipment cabinets, among others, as the case may be, are kept with a padlock or with a safety tag indicating that they are being operated or that some work is being carried out on them; 9 It is ensured that the live parts of the electrical substation are out of the personnel's reach or
protected by screens,
grilles, mesh or other similar means, and
9 The emergency exit is
identified and it is ensured that the doors open: o Outwards or are sliding; o Easily from the inside, and that they are clear of obstacles, and o From the outside only
with a special or
controlled key;
¾ On the equipment or devices of the Serious
temporary electrical installations being maintained, it verifies that: 9 The safety measures are applied, where there are uninsulated energised lines close to walls;
9 It is checked that they are
de-energised and earthed; 9 It is verified that there is no damage to the insulation of the conductors; 9 The joints have the mechanical strength to maintain the continuity of the circuit, and 9 Electrical continuity is maintained in all welds or joints; ¾ For carrying out work within the perimeter of the electrical installations, it verifies that:
9 The safety distance Serious
corresponding to the electrical voltage of the installation is maintained before carrying out any maintenance operation on the
conductors or electrical
installations. To establish the safety distance, it applies NOM-001- SEDE-2005, or those superseding it;
9 Maintenance operations at Serious
less than the working distance on a conductor or electrical installation are prevented while that conductor or electrical installation has not been de-energised, or while the safety measures indicated in this Standard have not been applied, and 9 The safety measures are adopted
and the specific
instructions given for preventing occupational risks,
where it is not possible to
disconnect a conductor or
item of equipment of an electrical
installation in whose vicinity maintenance operations are to be carried out. Those measures include at least the following:
o Fit insulating protection, padlocks or
safety tags on the energised conductors and installations, as appropriate, and o Control, where applicable, the
vicinity of conductors or equipment of an electrical installation that cannot be disconnected, so as to avoid the risk of contact, and
¾ For temporary electrical
installations, it follows at least the following safety measures: 9 Authorisation is requested in writing from the work supervisor of the switching centre or
control centre to fit temporary electrical
installations; 9 The work supervisor of the switching centre or
control centre is informed in writing of all those temporary modifications
| electrical | and the | distance of |
| safety | for | the voltages |
| with equipment | electrical | or the |
| proximity of | these | may |
| control centre, | authorisation | to |
| fit | installations | electrical |
switch blades, disconnectors, protection personal
fuse-switches and other are: gloves
devices similar, by dielectric, according to the
personnel authorised, using class and to
personal protective equipment and the voltage electrical;
safety equipment, according to the protection eye;
potential risks identified, helmet of safety;
and working clothing and boots
dielectric, among
9 The connection is made of some Serious 9 Are effectively protected the Serious
cables bare and other
elements exposed o Fit protection
insulating, padlocks or movement of the equipment
mobile used for giving
maintenance in the control centre, of all those
modifications temporary 9 It uses the installations
electrical temporary 9 It removes the installations
temporary at the end of the5.11 (conformity, 11.1) and 11.1 Physical The employer complies when it demonstrates that for carrying out maintenance work on
the overhead and underground electrical
installations the corresponding procedures are applied based on Chapter 8 of this Standard.
5.11 (conformity, 11.2) and 11.2 Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that for carrying out maintenance work on the overhead and underground electrical installations the following safety measures are complied with: ¾ It is verified that, in addition to the general safety measures established in Chapter 9 of this Standard, the following is complied with:
authorised and trained for that purpose;
9 The disconnection of lines Serious
or equipment from the electrical power source is carried out by first opening the equipment designed to operate under load;
9 For the opening or closing Serious
of energised gang-operated switch blades, the following is carried out: o It is verified that the operating handle is switched to earth; o Personal protective equipment suited to the activity is used, and o Insulating mats, blankets or covers are used, where there is excessive damp on the ground;
9 The absence of electrical Serious
voltage is verified before starting the work; both sides of the lines are short-circuited and earthed as close as possible to the place of work, and it is ensured that the earthing is of adequate size to carry an earth fault safely, maintains electrical continuity and a sufficiently low impedance; 9 Protective barriers and safety signs or notices are fitted in the work zone where the
connection/disconnection and/or
protective devices are located;
9 A warning notice bearing the Serious
wording "Danger, do not energise" and physical locks such as padlocks are fitted at the level of the sectionalising device or on the handle of the device, where switches, reclosers and switch blades located on the public highway are opened or where the equipment is remotely operable;
9 It is verified that all the Serious
possible supply sources in the work zone are open;
corresponds, where a pole is installed or as well as rawhide or removed between energised leather gloves for lines or near them; handling the pole.
9 The metal structure of the The workers do not Serious lorry used to place or remove a touch the vehicle
pole between energised lines while standing
or near them is earthed; on the ground, unless
fuses in high-voltage the activity is stopped. lines, the following: o The absence of
electrical voltage is
verified before starting the work and, where applicable, both sides of the lines are short-circuited and earthed as close as possible to the place of work;
o It is verified that the
fault has been corrected; o The safety distance is maintained. Fuse cut-outs, when open on
the load side, are considered energised and
to replace them they are earthed;
cotton working clothing and o The continuity of the safety spectacles. earthing connections and of the earthing conductors is verified;
9 The drum supplying the The worker attending Serious
conductor has an earthing connection, the drum must Serious
according to the voltage level 9 It is verified, on lines mounted . on the same supports, along all or part of their run, that: o Carrying out work and operations on a line by the
procedure known as
"agreed time" is prohibited; o Carrying out work is avoided, or work is suspended, when there are thunderstorms, and o Carrying out work on a line with two or more circuits while one of them is under electrical voltage is prevented, if performing it requires
moving the conductors, insulators or
mechanical supports in such a way that contact could be made with the other circuit, and
9 It is ensured that no worker Serious remains on the line, and that no
tools are left at the place of work, on completing the activities and before removing the earthing connections, and that the earthing connections are then
removed, in the reverse order
to that followed in fitting them.
| earthing, where a conductor is run to work | on an |
| near another conductor or platform | insulated and |
| conductors energised; | use insulating gloves, |
9 They carry out the activities of Serious
maintenance of the
installations electrical
only with personnel are located the devices of
connection/disconnection, and/or 9 They fit covers protective The workers use Serious
for the pole and/or for the gloves dielectric
conductor, according to the level for the voltage
of voltage electrical that electrical required, 9 It earths the structure The workers do not Serious
metal of the lorry used for touch the vehicle them; that they have
finished the
9 It carries out to replace the Serious
operations or it is side of the load are
considered energised and o The head is inclined For this
slightly downwards at the activity a helmet of
moment of closing a safety with
fuse cut-out, to chin strap for uses
be protected from the electric arc and electrical, boots of
possible ejections of safety without a toe cap
particles that may metal, gloves
occur, and dielectric, clothing of moving the conductors,
insulators or supports 9 It ensures that no worker remains Serious
on the line, nor5.11 (conformity, 11.3) and 11.3 Physical The employer complies when it demonstrates that for maintenance work on underground lines the following safety measures are complied with:
¾ As applicable, those provided for in
paragraph 11.2 of this Standard are used; ¾ The location of the equipment is identified as indicated by the
drawings; ¾ The routes, supply circuits, transformers, disconnectors and switches are located;
¾ The preventive measures for
carrying out the tasks are determined according to the risks present at the time of carrying out the work, and ¾ The condition and the electrical continuity of the earthing connections and of the earthing conductors are verified.
5.11 (conformity, 12) and 12 Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that the maintenance work on the
energised electrical installations is
carried out with the following safety measures: ¾ Compliance with the safety procedures referred to in paragraphs 8.1 to 8.3 of this Standard; ¾ Compliance with the following safety instructions:
9 The activity is carried out by Serious authorised and trained
workers;
9 The technique described Serious
in the procedures of the work plan is complied with and the tools and implements needed to carry out the activity are used, as well as the personal protective equipment suited to the risk;
9 The sequence for carrying out
the switching operations is followed, such as the connection and/or disconnection of sectionalising and protective devices, the transfer of lines,
the fitting of temporary
jumpers, the isolation of networks, among others;
9 The means of
communication are used, where applicable, with the
substation, the switching
centre or the work supervisor; 9 The handover and acceptance of the work zone is carried out for the start and completion of the activities, respectively, and
9 There is permanent
supervision while the work is carried out; ¾ A meeting is held before the start of the activities in the work zone, so as to carry out an analysis
of the conditions of the place,
taking into account at least the following: 9 The networks close to the work zone;
9 The correct positioning of the
vehicle, and 9 The earthing of the vehicle; ¾ Live-line work on faulted circuits, on rainy days or where the material and equipment needed are not available, is prohibited; ¾ There is a programme for the
inspection and maintenance of
vehicles, equipment and tools, so as to verify that they meet the insulation level required;
¾ It is verified that the protective and/or automatic sectionalising
equipment or the remotely operable equipment is in such a state that live-line work can be carried out;
¾ The personal protective equipment Serious
and the live-line working equipment of the class corresponding to the electrical voltage level of the
installation where the work is
carried out is always used, and ¾ The work is carried out on one phase at a time, keeping the others away and/or covered.
9 The activity is carried out by Serious
workers authorised and ¾ It is verified that the equipment of
protection and/or sectionalising5.12 (conformity) The employer complies when:
Physical ¾ On carrying out a walk-through of the Serious
workplace, it is established that it has in the work zones at least one fire extinguisher, accessible at all times, or
Documentary ¾ It presents evidence that the fire extinguisher
corresponds to the capacity and fire type that may arise in the work zone, according to the determination of potential risks referred to in paragraph 7.2 of this Standard.
5.13 (conformity) Documentary The employer complies when it presents evidence Serious documentary that it authorises in writing
trained workers to carry out maintenance activities on the
electrical installations at height, in confined spaces or in substations, as well as those
who handle live parts of those
installations.
workers trained to carry out
activities of maintenance of the5.14 (conformity) Documentary The employer complies when it presents evidence
documentary that it informs the
workers who carry out activities of
maintenance of the electrical
installations about the risks to which they are exposed and about the safety measures they must adopt for the activity to be carried out in the work zone.
5.15 (conformity) and 13 Documentary The employer complies when: ¾ It presents documentary evidence that it has an emergency response plan,
available for its consultation
and application; ¾ The emergency response plan contains at least the following: 9 The person responsible for implementing the plan;
9 The equipment or apparatus
needed to carry out the plan; 9 The procedures for:
o Communicating the emergency, together with the
directory of the assistance services for the emergency, rescue and hospitals, among others;
o Suspending the
activities, including the immediate actions for disconnecting the energy source; o Eliminating the risks
during and after the
emergency; o Using the rescue systems and equipment, where applicable; o Attending to and transferring the casualties to places of care
visible, on what to do in the event
of an accident; the
instructions for removing the
injured person from immediate
danger; placing the casualty in a safe place; giving first aid,
where applicable; applying
cardiopulmonary resuscitation (CPR) techniques, and those for calling the assistance services, and the nearest hospitals or
medical units
for transferring the casualty, and o Resuming activities, where applicable, and 9 The training and instruction of the workers in relation to the content of the emergency response plan.
| medical, | which | at least |
| indicate: | the | instructions |
| specific | in | a place |
o The communication of the
emergency, together with the5.16 (conformity) Physical The employer complies when, on carrying out a walk-through of the workplace, it is established that it has a first-aid kit containing the manual and the dressing materials needed to deal with the possible emergency cases identified according to the risks to which the workers are exposed, and to attend to those injured or involved in accidents caused by electrical energy.
5.17 (conformity) and 14 Documentary The employer complies when it presents documentary evidence that:
¾ It provides training and
instruction to the workers who carry out maintenance activities on the workplace's electrical installations, based on the safety procedures drawn up for that purpose;
¾ It provides training,
instruction and information, according to the tasks assigned and the emergency response plan, and ¾ The training takes into account at least the following: 9 The information on the occupational risks relating to the
maintenance of the
electrical installations; 9 The general description of the
effects on the body
caused by an electric shock or its effects, as a consequence of contact with, a fault in, or approach to energised elements, with emphasis on the conditions that shall be avoided so as to prevent injury or harm to health; 9 The safety procedures for carrying out the maintenance of the electrical installations referred to in Chapter 8 of this Standard; 9 The safety measures established in this Standard applicable to the activities to be carried out, and while carrying out the maintenance work on the electrical installations;
9 The use, maintenance,
upkeep, storage and
replacement of the
personal protective equipment, in accordance with NOM- 017-STPS-2008, or those superseding it; 9 The theoretical and practical topics on the safe way of handling,
maintaining, inspecting and
storing the machinery, equipment,
tools, materials and work
implements; 9 The conditions under which the machinery, equipment, tools,
materials and work
implements will be taken out of service for repair or replacement; 9 The weather conditions or other
unfavourable factors that would make it necessary to interrupt the
work, and 9 The content of the emergency response plan and other actions
arising from the
emergency situations that could arise while the maintenance work on the
electrical installations is
carried out.
| factors | unfavourable | that |
| would make it necessary | to interrupt | the |
5.18 (conformity) Physical The employer complies when, on carrying out a Serious walk-through of the workplace, it is established that, where it has agreed services with contractors to carry out maintenance work on the
electrical installations, it supervises
that they comply with this Standard.
5.19 (conformity) Records The employer complies when it has the
which cover the name of the person responsible for
carrying out the work; the activities
performed and their results, as well as the dates on which that work was carried out.
records of the results of the
maintenance carried out on the
installations electrical, which at least16.4 For the selection of the workers to be interviewed so as to establish compliance with the provisions laid down in this conformity assessment procedure, the sampling criterion contained in Table 1 below shall be applied: Table 1 Random selection sampling Number of workers to be Total number of workers interviewed 1-15 1 16-50 2 51-105 3 1 for every 35 workers up to a More than 105 maximum of 15
16.5 The documentary evidence or the records held in the workplace may be presented in printed form or on magnetic media, and shall be kept for at least one year.
17. Enforcement
Enforcement of compliance with this Official Mexican Standard is the responsibility of the Ministry of Labour and Social Welfare.
18. Bibliography
18.1 NFPA 70E Standard for electrical safety in the workplace, 2010 edition.
18.2 Elementos de diseño de instalaciones eléctricas industriales (Design elements of industrial electrical installations). Gilberto Enríquez Harper. Editorial Limusa, S.A. de C.V.
18.3 Fundamentos de instalaciones eléctricas de media y alta tensión (Fundamentals of medium- and high-voltage electrical installations). Gilberto Enríquez Harper. Editorial Limusa, S.A. de C.V. 10 External cleaning
| 2 | Replace fuses | x | x | x | x |
| 3 | Change a | x | x | x | x |
| 2 | Replace fuses | x | x | x |
| 3 | Change a lamp or | x | x | x |
Have Have of De-energise Verify the Have of Use equipment
an instructions or or disconnect absence equipment of of protection
order or procedures the circuit of work, personal
No. Activity plan of of safety potential machinery, suitable
work tools and 4 Replace a
ballast of a x x x x x 6 Replace a
x x x x x 7 Relocate a
x x x x x x 8 Check the
x x x connection of x x x x
sockets and 11 Work on
boards of x x x x x calibration, x x x
location of13 Replace a
x x x x x Use Use Maintain the Do not touch Carry out the
instruments of tools distances of the part activities only
No. Activity
measurement suitable safety conducting with personnel
according to the of energy trained 1 Carry out inspections of
the installations x X x x 5 Check voltage
x x x 6 Replace a
x x x 7 Relocate a switch x x x
8 Check the earthing
x x x x12 Electrical measurements,
calibration, location x x x x19. Concordance with International Standards
This Official Mexican Standard does not concord with any international standard, as no reference existed at the time of its drafting.
TRANSITIONAL PROVISIONS
FIRST. This Official Mexican Standard shall enter into force three months after its publication in the Official Journal of the Federation. SECOND. During the period indicated in the preceding article, employers shall comply with Official Mexican Standard NOM-029-STPS-2005, Maintenance of electrical installations in workplaces- Safety conditions, or shall make the adaptations needed to observe the provisions of Official Mexican Standard NOM-029-STPS-2011, Maintenance of electrical installations in workplaces-Safety conditions. In the latter case, the labour authorities shall provide, at the request of interested employers, advice and guidance for implementing compliance, without the employers becoming liable to penalties for non-compliance with the Standard in force. THIRD. From the date on which this Standard enters into force, Official Mexican Standard NOM-029-STPS-2005, Maintenance of electrical installations in workplaces- Safety conditions, published in the Official Journal of the Federation of 31 May 2005, shall cease to have effect. Given in Mexico City, Federal District, on the twenty-ninth day of the month of December of the year two thousand and eleven.- The Minister of Labour and Social Welfare, Rosalinda Vélez Juárez.- Signature.
Reference Guide I
Safety measures for basic maintenance activities on electrical installations at voltages below 600 V The content of this guide is a supplement for a better understanding of this Standard and is not mandatory. Table I.1 indicates the safety measures that may be adopted when basic maintenance activities are carried out on electrical installations at voltages below 600V. Table I.1 Safety measures for basic maintenance activities on electrical installations at voltages below 600 V Safety measure insulating protective implements 1 Carry out electrical inspections lamp or bulb lamp 5 Check voltage socket switch switch earthing 9 Replace condition of switch boxes distribution 12 Electrical measurements, faults motor or pump 14 Make joints in lines or circuits 15 Opening and inspection protection Cont…Table I.1 Safety measures for basic maintenance activities on electrical installations at voltages below 600 V Safety measure voltage level handled electrical bulb 4 Replace a ballast of an electrical lamp of a socket switch earth 9 Replace conductors in poor condition 10 External cleaning of sockets and switches 11 Work on distribution boards of faults 13 Replace a motor or pump 14 Make joints in lines or circuits 15 Opening and inspection of protective elements _____________________