NR10 – Safety in Electrical Installations and Services

NR-10 Safety in Electrical Installations and Services (Annotated)
(Version 2019, with comments and explanations)

(The following text is from December 2004 version)

10.1 Objective and Scope


10.1.1 This Regulatory Standard (NR10) establishes the minimum requirements and conditions aiming the implementation of control measures and preventive systems in order to ensure the safety and health of workers who directly or indirectly interact with electrical installations and services.

10.1.2 This NR applies to generation, transmission, distribution and consumption, including the stages of project, construction, assembly, operation, maintenance of the electrical installations and any work performed in the surrounding area in compliance with the official technical standards established by the competent bodies and, in the absence or omission of these, the applicable international standards.


10.2.1 For all the interventions in electrical installations preventive measures to control the electrical hazard and other additional risks through risk analysis techniques in order to ensure the safety and health at work shall be adopted.

10.2.2 The control measures shall be integrated with the other company initiatives within the framework of preservation of the occupational health, safety and environment.

10.2.3 The companies are obliged to keep single-line diagrams of the electrical installations in their establishments with the specifications of the grounding system and other equipments and protective devices up-to-date.

10.2.4 The establishments with installed load greater than 75 kW shall establish and maintain a Electrical Installation Log Book containing at least followings, in addition to the provisions of the sub-item 10.2.3:

a) set of procedures and administrative and technical guidelines for safety and health, implemented and related to this NR and description of existing control measures;

b) documentation of inspections and measurements of the protection system against lightning and electrical grounding;

c) specification of the collective and individual protective equipments and the tools, as applicable according to this NR;

d) support documentation of qualification, habilitation, capacity building, authorization of the employees and the trainings conducted;

e) results of electrical insulation tests performed on individual and collective protective equipments;

f) certification of the equipments and materials in hazardous areas;

g) technical report on updated inspections with recommendations, schedule of adjustments, contemplating the paragraphs from “a” to “f”.

10.2.5 The companies that operate in installations and equipments part of electrical power system shall constitute records with the content of item 10.2.4 and add the documents listed below to the record:

a) description of emergency procedures;

b) certification of the collective and personal protective equipments. Companies that perform works in the proximity of the Electrical Power System shall constitute a record contemplating the paragraphs “a”, “c”, “d” and “e” of item 10.2.4 and the paragrphs “a” and “b” of item 10.2.5.

10.2.6 Electrical Installation Log Book shall be organized and kept updated by the employer or by a person formally appointed by the company, and shall remain at the disposal of the employees involved in the electrical installations and services.

10.2.7 The technical documents provided in the Electrical Installation Log Book shall be prepared by a legally qualified professional.

10.2.8 – COLLECTIVE PROTECTIVE MEASURES For all services undertaken on electrical installations, above all, the applicable collective protective measures shall be planned and adopted, by means of procedures, for the activities to be undertaken in order to ensure the safety and health of the workers. The collective protective measures primarily comprise of de-energizing as provided in this NR, and when this is not possible, the use of safe voltage. If it is not possible to implement the provisions of sub-item, other collective protective measures shall be used, such as: insulation of live parts, obstacles, barriers, signs, automatic isolation system, blocking of auto recloser system. The grounding of electrical installations shall be implemented in accordance with the regulations by the competent bodies, in the absence of such regulations, existing International Standards shall be met.

10.2.9 – INDIVIDUAL PROTECTIVE MEASURES When the collective protective measures are not technically feasible or insufficient to control hazards in electrical installation works, individual protective equipments appropriate to the activities to be performed shall be adopted in compliance with the provisions in the NR6. The clothings shall be adequate to the activities, considering the conductivity, inflammability and electromagnetic influences. It is forbidden to use personal adornments in the work with electrical installations or in its vicinity.


10.3.1 It is mandatory that the electrical installation designs specify the circuit breakers which have features to prevent re-energizing towards warning signs with an indication of operative conditions.

10.3.2 The electrical designs, to the extent possible, shall provide the installation of isolation devices that allow to prevent re-energizing the circuit.

10.3.3 The electrical installation designs shall consider a safe space, as to the dimension and location of its components and external influences, with respect to the operation and realization of construction and maintenance services. The electrical circuits with different purposes, such as: communication, signalization, electric traction and control shall be identified and installed separately, except when the technological development enables sharing, respecting the design settings.

10.3.4 The design shall define the configuration of the grounding scheme, the need for interconnection between neutral conductor and that of protection and the grounding of conductive parts that are not intended for the conduction of electricity.

10.3.5 Where technically feasible and necessary, the sectioning devices which incorporate equipotentialization and grounding of switched circuit shall be designed.

10.3.6 Every design shall provide conditions for the adoption of temporary grounding.

10.3.7 The electrical installation designs shall be made available to the authorized employees, the competent authorities and others authorized by the company and shall be kept updated.

10.3.8 The electrical projects shall meet the Regulatory Standards on Health and Safety at Work, the official technical regulations, and be signed by a legally qualified professional.

10.3.9 The description of the project shall include at least the following safety items:

a) specification of the characteristics relating to the design against electric shock, burns and other additional risks;

b) indication of the position of switching devices: (Green – “D” (Off/Disconnected) and Red – “L” (On/Connected);

c) description of identification system of electrical circuits and equipments, including switching, control, protection, interlocking devices, conductors and their own equipments and structures, defining how such information shall be physically applied on the components of the installations.

d) recommendations for restrictions and warnings regarding the access of persons to the components of the installations;

e) applicable precautions in case of external influences;

f) functional principles of the protective devices in the projects, intended for the safety of people;

g) description of the compatibility of protective devices with the electric installation.

10.3.10 The designs shall ensure that adequate lighting and a safe working position is provided to the workers according to NR17 – Ergonomics.


10.4.1 The electrical installations shall be constructed, assembled, operated, renovated, expanded, repaired and inspected so as to ensure the safety and health of workers and users, and are supervised by an authorized professional according to this NR.

10.4.2 Preventive measures intended to control additional risks shall be adopted in such works and activities, especially performed at height, confined spaces, electrical and magnetic fields, explosives, humidity, dust, plants and animals and other aggravating agents, with the adoption of safety signs.

10.4.3 Equipments, devices and power tools compatible with the existing electrical installation shall  be used in the workplaces, preserving the protective characteristics according to manufacturer’s recommendations and external influences. The equipments, tools and devices that have electrical insulation shall be appropriate to the voltages involved, and be inspected and tested in accordance with the existing regulations or the manufacturers’ recommendations.

10.4.4 The electrical installations shall be maintained in safe operating condition and their protection systems shall be inspected and checked periodically in accordance with the existing regulations and design definitions. The locations of the electrical services, the compartments and the enclosures of the electrical equipments and installations are exclusive for that purpose and it is expressly forbidden to use them for either storage or safekeeping of any objects.

10.4.5 Adequate lighting and a safe working position shall be provided to the workers who work on electrical installations in accordance wit NR17 – Ergonomics so as to allow them to perform their tasks without any restrictions for upper limbs.

10.4.6 The laboratory and field tests or commissioning of the electrical installations shall comply with the regulations established in items 10.6 and 10.7, and can only be performed by workers who meet the qualifications, skills, training and authorization established in this NR.


10.5.1 The electrical installations shall only be considered as de-energized, by means of the appropriate procedures, in accordance with the following sequence:

a) segregation;

b) prevention of re-energizaton;

c) verification the lack of voltage;

d) the installation of temporary grounding with equipotential of the conductors of the circuits;

e) protection of existing energized elements in the controlled area (Annex II);

f) tag out for the prevention of re-energizing.

10.5.2 The state of the de-energized installation shall be maintained until the authorization for re-energization, and shall be re-energized respecting the following sequence of procedures:

a) withdrawal of tools, utensils and equipment;

b) withdrawal of all workers not involved in the re-energization process from the controlled area;

c) removal of temporary grounding, of equipotentialization and additional protection;

d) removal of signs for the prevention of re-energizing.

e) unlocking, if locked, and rewiring of the sectioning devices.

10.5.3 The measures set out in the paragraphs presented in items 10.5.1 and 10.5.2 may be altered, substituted, expanded or eliminated as a function of the peculiarities of each situation, by an authorized and legally qualified professional and by means of a prior formal technical justification, provided that the same level of safety as originally established is maintained.

10.5.4 The services to be performed on disconnected electrical installations, but with the possibility of energization, by any means or reason, shall comply with the provisions in item 10.6.


10.6.1 The interventions on electrical installations with voltages equal or higher than 50 volts on alternating current or higher than 120 volts on direct current can only be performed by workers who meet item 10.8 of this standard. The workers mentioned in the previous paragraph shall receive safety training to work with electrical installations, with minimum curriculum, workload and other criteria established in Annex III of this NR. The elementary operations such as connecting and disconnecting electrical circuits performed at low voltage with electrical materials and equipments in perfect condition and suitable to task can be performed by any non-warned person.

10.6.2 The jobs that require entry into the controlled area shall be performed by means of specific procedures respecting the distances provided in Annex II.

10.6.3 The services on energized installations, or in their vicinity shall be suspended immediately in case of any occurrence that may put workers in danger.

10.6.4 Whenever technological innovations are implemented or for the entry into operations of new electrical installations or equipments, risk analyzes on de-energized circuits and work procedures shall be developed previously.

10.6.5 The person responsible for performing the service shall suspend his/her activities while checking situation or condition of the unforeseen risk whose immediate elimination or neutralization is not possible.


10.7.1 The workers involved in energized high voltage electrical installations, who perform their activities within the limits established as controlled areas and risk zones, according to Annex II, shall meet the requirements of item 10.8 of this NR.

10.7.2 The workers mentioned in item 10.7.1 shall receive safety training, particularly on safety in Electric Power System (SEP) and in its proximity, with minimum curriculum, workload and other provisions provided in Annex III of this NR.

10.7.3 The services in energized high voltage electrical installations, as well as those running on Electric Power System, cannot be carried out individually.

10.7.4 All work in energized high voltage electrical installations, as well as those that interact with the SEP, can only be carried out by means of specific work order for date and location, signed by responsible supervisor for the area.

10.7.5 Before starting work on energized high voltage circuits, the the immediate superior and the staff responsible for the execution of the service shall perform a preliminary evaluation, study and plan the activities and actions to be developed in order to meet the basic technical principles and the best practices for electrical safety applicable to the service.

10.7.6 The services in energized electrical installations may only be carried out when there is specific and detailed procedures signed by an authorized professional.

10.7.7 The intervention in energized high voltage electrical installations within the limits established as a risk zone, according to Annex II of this NR, can be performed only through deactivation of, also known as locking out, the joint devices and auto recloser of the circuit, system or equipment. Disabled equipments and devices shall be marked to identify them as disactivated according to job-specific standardized procedures.

10.7.8 The equipments, tools and devices insulated or equipped with insulating materials, designed to work with high voltage, shall undergo periodic laboratory or electrical tests complying with the manufacturer specifications, company procedures and in the absence of these, annually.

10.7.9 Everyone who works on energized high voltage electrical installations, as well as those involved in activities on the SEP shall have equipments that allow continuous communication with other team members or with the operation center while performing the service.


10.8.1 A qualified worker is considered as a person who proves the conclusion of a specific course in the electrical area acknowledged by the Official Education System.

10.8.2 A legally qualified professional is considered as a qualified worker who is registered in a relevant professional council.

10.8.3 A skilled worker is considered as a person who meets the following conditions simultaneously:

a) receive training under the supervision and responsibility of an authorized and qualified professional, and;

b) work under the supervision of an authorized and qualified professional. The capability of a worker will only be valid for the companies that trained the workers and under the conditions established by an authorized and qualified professional responsible for capacity development.

10.8.4 The capable or qualified workers and qualified professionals with formal agreement of the company are considered authorized.

10.8.5 The company shall establish an identification system to know the comprehensiveness of authorization of each worker, according to item 10.8.4.

10.8.6 The workers authorized to work on electrical installations shall have such authorization  recorded in the employee record system of the company.

10.8.7 The workers authorized to intervene in electrical installations shall undergo a medical examination compatible with the activities to be undertaken, which shall be conducted in accordance with the NR7 and registered in workers’ medical records.

10.8.8 The workers authorized to intervene in electrical systems shall have a specific training about the risks arising from the use of electricity and major accident prevention measures in electrical installations, in accordance with the provisions of Annex III of this NR. The company shall grant permission in the form of this NR to the trained or qualified workers and qualified professionals who have taken part in assessment and satisfactory use of the courses listed in Annex III of this NR. A refresher training shall be conducted every two years and whenever any of the following situations occur:

a) functional change or change of company;

b) return to work from leave or inactivity for more than three months;

c) significant changes in the electrical installation or change of methods, processes and work organization. The workload and the program content of refresher training aimed to meet the paragraphs “a”, “b” and “c” of item shall meet the needs of the situation that motivated. The works in hazardous areas shall be preceded by a specific training in accordance with the risk involved.

10.8.9 The workers with activities not related to electrical installations in zone of clearance or in the vicinity of controlled area, as defined in this NR, shall be formally instructed with knowledge to identify and assess the possible risks and to adopt reasonable precautions.


10.9.1 The areas where there are electrical installations and equipments shall be provided with fire and explosion protection in accordance with the NR23 – Fire Protection.

10.9.2 The materials, parts, devices, equipments and systems designed for use in electrical installations in potentially explosive atmospheres shall be evaluated for compliance within the framework of Brazilian Certification System.

10.9.3 The processes or equipments which may generate or create static electricity shall have specific protection and electrical discharge devices.

10.9.4 Protective devices, such as alarms and automatic sectioning to prevent over-voltage, over-current, failures of isolation, heating or other abnormal operating conditions shall be adopted for electrical installations in hazardous areas or those subject to fire and explosion risks.

10.9.5 The services on electrical installations in hazardous areas may only be performed by means of permit to work in accordance with item 10.5 or the suppression of risk agent that determines the classification of the area.


10.10.1 Adequate safety signs intended to warn and identification shall be adopted in electrical installations and services, as provided in NR26 – Safety Signs, in order to meet, among others, the following situations:

a) identification of electrical circuits;

b) lock out and blockage of operating and control devices and systems;

c) restriction and prevention of access;

d) delimitation of areas;

e) signs in circulation areas, public roads, vehicles and cargo handling;

f) tag out to prevent of energization;

g) identification of equipment or impeded circuit.


10.11.1 The services in electrical installations shall be planned and performed in accordance with specific standardized work procedures with detailed description of each work, step by step, signed by a professional who meets requirements in item 10.8 of this NR.

10.11.2 The services in electrical installations shall be preceded by specific service orders, approved by an authorized worker, containing at least the type, date, location and referrals to the work procedures to be adopted.

10.11.3 The work procedures shall contain at least objective, scope, technical basis, competencies and responsibilities, general provisions, control measures and final guidelines.

10.11.4 The work procedures, health and safety training and the authorization referred in item 10.8 shall have a participation in the entire development process of the Specialized Services in Occupational Health and Safety Training (SESMT), if any.

10.11.5 The authorization referred in item 10.8 shall be given in compliance with the training provided in Annex III of this NR.

10.11.6 Every team shall have an appointed worker who is able to supervise and conduct the work.

10.11.7 Before starting to work in a team, the team members, in conjunction with responsible for the execution of the service, shall carry out a preliminary assessment, study and plan the activities and actions to be undertaken in the work site, in order to meet the basic technical principles and the best safety practices applicable to the service.

10.11.8 The alternation of activities shall consider the risk analysis of the tasks and the competency of the employees involved, in order to ensure the health and safety at work.


10.12.1 Emergency actions involving electrical installations and services shall be included in company emergency plan.

10.12.2 The authorized workers shall be able to rescue and perform first aid to the injured, especially through cardiopulmonary resuscitation.

10.12.3 The company shall have adequate and standardized rescue methods, providing the means for their implementation.

10.12.4 The authorized workers shall be able to handle and operate the fire protection and fighting equipments in electrical installations.


10.13.1 Responsibilities regarding to compliance with this NR are jointly liable to contracting and contracted companies involved.

10.13.2 It is the responsibility of contracting company to keep workers informed about the risks they are exposed, instructing them on procedures and control measures to be adopted against electrical hazards.

10.13.3 It is up to the company, upon the occurrence of accidents involving electrical installations and services, to propose and adopt preventive and corrective measures.

10.13.4 It is workers’ responsibility to:

a) take care their own health and safety and that of others who may be affected by their actions or omissions at work;

b) be responsible along with the company for compliance with legal and regulatory provisions, including internal procedures regarding health and safety; and

c) report the situations that may pose risk to their own health and safety and of others immediately.


10.14.1 The workers shall stop their tasks by using their right to refuse to work, whenever they find evidence of serious and imminent danger to their health and safety or that of others, and immediately report the fact to their hierarchical superiors who shall take reasonable measures.

10.14.2 Companies shall promote actions to control risks arising from others in their electrical installations and offer complaints to the competent bodies immediately, when appropriate.

10.14.3 In the event of non-compliance with the standards of this NR, the MTE shall take the measures set out in NR3.

10.14.4 The documentation referred in this NR shall be permanently available to the workers who work in electrical installations and services, complied with comprehensions, limitations and interferences in the tasks.

10.14.5 The documentation referred in this NR shall permanently be available to the competent authorities.

10.14.6 This NR is not applied to electrical installations powered by extra-low voltage.


Annex II – Risk Zone and Controlled Area

Annex III – Training