Contents Page

European foreword 4

1 Modification to 3.2 “Personnel, organization and communication” 4

2 Modification to 3.6 “Voltages” 5

3 Modification to 3.7 “Distances” 5

4 Modification to 4.3.2, “The installation manager (IM)” 6

5 Modification to 4.3.4, “The work controller (WC)” 6

6 Modification to 4.4 “Communication (transmission of information)” 6

7 Modification to 4.11.2.1 “General” 7

8 Modification to 4.11.2.2 “Explanations of determination of the values of D_L and D_V” 7

9 Modification to 6.2.3.1 “General” 7

10 Modification to 6.2.5.1 “General” 7

11 Modification to 6.2.5.3 “Requirements for high voltage installations” 8

12 Modification to 6.2.6 “Protection against adjacent live parts” 8

13 Modification to 6.2.7 “Permission to start work” 8

14 Modification to 6.2.8 “Re-energizing after work” 8

15 Modification to 6.3 “Live working” 8

16 Modification to 6.3.4.2 “Hot stick working – Safe clearance working” 8

17 Modification to 6.4 “Working within the vicinity zone” 8

18 Modification to Annex A “Guidance for distances in air for working procedures“ 9

19 Modification to B.1.4 “Large or industrial company” 13

20 Modification to B.3.2 “Thick fog” 13

21 Modification to B.6 “Arc hazard” 13

22 Modification to B.7 “Emergency arrangements” 15

23 Modification to C.2 “French” 15

24 Modification to C.3 “German” 17

25 Modification to the Bibliography 18

European foreword

This document (EN 50110-1:2023/prA1:2026) has been prepared by CLC/BTTF 62‑3 “Operation of electrical installations”.

The following dates are proposed:

This document amends EN 50110‑1:2023 on the following items:

— adding a new standard in Clause 2 – Normative references;

— improvement of some definitions in Clause 3 – Terms and definitions;

— editorial improvements and corrections of some parts of the Text in Clause 4 – Basic principles and Clause 6 – Working procedures;

— corrections of some parts of the Text in Annex A – Guidance for distances in air for
working procedures;

— improvement of some parts of the Text in Annex B – Additional information for safe working;

— improvement of the Text in B.6 – Arc hazard;

— corrections of some parts of the Text in C.2 – French and C.3 – German;

— update of the Clause “Bibliography”.

Replace term and definition 3.2.6 with the following:

“3.2.6

instructed person, <electricity>

person adequately advised by a skilled person to enable them to understand the risks as instructed and to avoid hazards which electricity can create

[SOURCE: IEC 60050-651:2014, 651-26-12 modified, the term “supervised” was deleted, “electrically” was deleted “danger” was replaced by “hazard”, “perceive” was replaced by “understand” and added “as instructed”]”

Replace term and definition 3.6.1 with the following:

“3.6.1

extra-low voltage

ELV

nominal voltage not exceeding 50 V alternating current AC or 120 V ripple free direct current DC whether between conductors or to earth

Note 1 to entry: This definition includes SELV, PELV and FELV (see HD 60364-4–41).”

Replace term and definition 3.6.2 with the following:

“3.6.2

low voltage

L_V

nominal voltage not exceeding 1 000 V AC or 1 500 V DC”

Replace term and definition 3.6.3 with the following:

“3.6.3

high voltage

H_V

nominal voltage exceeding 1 kV AC or 1,5 kV DC”

Replace term and definition 3.7.1 with the following:

“3.7.1

live working limit distance

D_L

distance in air defining the outer limit of the live working zone”

Replace term and definition 3.7.2 with the following:

“3.7.2

vicinity limit distance

D_V

distance in air defining the outer limit of the vicinity zone”

Replace term and definition 3.7.3 with the following:

“3.7.3

minimum approach distance for live working

D_A

minimum distance in air for live working to be maintained between any part of the body of a worker (W), including any object (except tools appropriate for live working) being handled directly, and any part(s) at different electric potential(s)

Note 1 to entry: The minimum approach distance for live working is the sum of the electrical distance D_U appropriate for the maximum nominal voltage and of the selected ergonomic distance D_E.

[SOURCE: IEC 60050-651: 2014, 651-21-11 modified by adding: for live working”]”

Replace term and definition 3.7.4 with the following:

“3.7.4

minimum working distance

D_W

minimum distance in air (including tools, objects and equipment) to be maintained between any part of the body of a worker and bare live parts during work activities within or outside the vicinity zone

Note 1 to entry: For minimum working distance for working within the vicinity zone the symbol is D_WL.

Note 2 to entry: For minimum working distance for working outside the vicinity zone the symbol is D_WV.”

Replace term and definition 3.7.7 with the following:

“3.7.7

ergonomic distance, <vicinity>

E

distance in air, to take account of normal and unintentional movements and errors in judgement of distances during work activities within or outside the vicinity zone

Note 1 to entry: This distance is not fixed because it is necessary to make an evaluation for different situations of work.”

Replace subclause 4.3.2 with the following:

“The installation manager (IM) is in charge of the overall responsibility to ensure the safe operation of the electrical installation by setting rules and organization or framework

The installation manager (IM) can be a natural person from the own organization or a third-party organization. In the case of a person from another organization, it is recommended to document the nomination, the part of the installation the person is responsible for and the timescale of nomination in writing

The installation manager (IM) can delegate a part of their duties to other persons. This should be documented

Where two or more electrical installations or organizations come together, it is essential that there are formal arrangements for consultation and cooperation between the installation manager (IM) of each of those installations or organizations to ensure safety

Access to all places where ordinary persons are exposed to electrical hazards shall be regulated. The method of regulation and control of access shall be the responsibility of the installation manager (IM)

NOTE National requirements can apply to the method of regulation and control of access.”

Replace subclause 4.3.4 with the following:

“The work controller (WC) has the responsibility for the work activity

Where the work activity is subdivided, it may be necessary to nominate a person for each subdivision to be responsible for the safety, all under the responsibility of the work controller (WC) as the coordinating person

The work controller (WC) and the operation controller (OC) shall agree both the arrangements of the electrical system to allow the work to take place and a description of the work activity on, with or near the electrical installation before any changes to the arrangements of the electrical installation are made or work takes place.”

Replace the 1^st paragraph with the following:

“This includes every way in which information is passed or exchanged between persons i.e. by spoken word (including telephone, personal radio, and face to face), in writing (including, e.g. fax or e-mail), and visually (including visual display units, warning panels, lights etc.).”

Replace the last paragraph with the following:

“In the case of personnel in a work location speaking different languages, to ensure understanding and comprehensibility, the agreed language that relevant parties understand shall be granted in advance.”

Replace the three list items with the following:

— the live working zone: the inner limit is the bare live part, the outer limit is the live working limit distance D_L;

— the vicinity zone: the inner limit is the live working limit distance D_L, the outer limit is the vicinity limit distance D_V;

— the surrounding outside the vicinity zone. (beyond the vicinity limit distance D_V).

Replace the 2nd paragraph with the following:

“The minimum values of D_L are determined by the calculation of the electrical distance D_U plus a safety margin. As a result, the minimum values given in Table 1 are estimated or rounded and represent the lowest value among the set of European values. Explanations are given in Annex A.

NOTE The values of the distance in air defining the outer limit of the live working zone D_L, are based on the lowest values of N (minimum clearance in air phase to earth and phase to phase given in Tables 2 and 3 of EN IEC 61936‑1:2021).”

Replace the 4th paragraph with the following:

In the absence of computation methods for DC-systems, the values for distance D_L and D_V for AC-systems may also be used for DC-systems up to and including 70 kV. (see Table 1). For low voltage (either 0 to 1 000 V AC or 0 to 1 500 V DC) the respective distances are the same.

Replace the title of the 2nd and 3rd column in Table 1 with the following:

Table 1 — Estimated values for distances D_L and D_V

Replace the 1st paragraph with the following:

“All relevant devices, e.g. fuses, switches, jumpers that have been used or removed to disconnect the electrical installation for the work activity shall be secured against re-connection.

Other relevant devices, e.g. fuses, switches, jumpers, that can be used to energize the electrical installation, shall also be secured against re-connection.”

Replace the 5th paragraph with the following:

“Earthing and short-circuiting equipment or devices shall comply with EN 61219 or EN 61230.”

Replace the 7th paragraph with the following:

“Precautions shall be taken to ensure that the earthing and short-circuiting equipment or devices remain in place as long as the work is in progress. If, during measurement or testing, the earthing and short-circuiting connections are removed, additional or alternative special precautions to prevent electrical danger shall be taken.”

Replace the text of the first two list items with the following:

“

— for a specific work activity, where there is no interruption in conductors during work, the installation of a single earthing and short-circuiting equipment or device at the work location is acceptable;

— If no earthing and short-circuiting devices or equipment can be seen within the limits of the work location, locally applied earthing and short-circuiting devices or equipment or additional signalling devices or other equivalent markings shall be provided to ensure that there is no significantly increased risk to the person working on the bare live part or that the bare live part is energized during the work activity.”

Replace the paragraph with the following

“If the work location is in the vicinity of parts of an electrical installation which cannot be made dead, then special additional precautions are necessary and shall be applied before work starts as detailed in working within the vicinity zone (see 6.4) or working outside the vicinity zone (see 6.5).”

Replace the 3rd paragraph with the following:

“For work activities on, with or near high voltage installations, formal written details of disconnections and earthing and/or short-circuiting, where appropriate, should be used to avoid misunderstandings.”

Replace the 2nd paragraph with the following:

“All earthing, short-circuiting and safety equipment and/or devices at the work location shall be removed. Starting from the work location and progressing outwards, the earthing, short-circuiting equipment and/or devices that were applied to the electrical installation shall be removed and all the locks or other devices, which were used to prevent re-connection shall also be removed. All signs used for the work activity shall be removed.”"

Replace paragraph 6.3.1.2 with the following:

“6.3.1.2 The requirements of 6.3 might not apply to activities such as voltage detection and the application of earthing and short-circuiting equipment or devices, etc.”

Replace subclause 6.3.4.2 with the following:

“The method of live working by which the worker (W) remains at a specified distance (see A.2.5) from the live parts and carries out their work by means of insulating sticks.”

Replace paragraph 6.4.1.4 with the following:

“6.4.1.4 For working within the vicinity zone, the minimum working distance D_WL according to the type of work planned should be determined and maintained at all time and situations.”

Replace Annex A with the following:

“

Annex A
(informative)

Guidance for distances in air for working procedures

A.1   Limit distances

Limit distances D_L and D_V define zones in which the safety rules should be applied for electrical and non-electrical work.

The explanation and determination of those distances is pointed out in 4.11.2.2.

A.2   Working distances

A.2.1   General

In the presence of an electrical hazard, regardless of the work to be carried out, working distances should be determined during the work preparation, taking into account the following items:

— the type of work to be carried out;

— the value of the operating voltage;

— the tools or objects used;

— the possibility of normal and unintentional movements towards the electrical hazard (ergonomic considerations).

This annex provides a method to determine:

— D_A for live working;

— D_W for working within or outside the vicinity zone.

A.2.2   Determination of the distance value related to the voltage level

The formulas to determine the working distance differ according to the type of work:

— For live working, the basic value is the electrical distance given in the EN IEC 61472-2 for the voltage up to 72,5 kV or in the EN 61472 for the voltage above 72,5 kV. This electrical distance is written as D_U in the formula for the minimum approach distance for live working.

— For working within and outside the vicinity zone, the basic values are the minimum acceptable distances in air given in the Table 1 (D_L and D_V) which are used in the minimum working distance formulas for D_WL and D_WV.

A.2.3   Considerations of tools, devices or equipment

To determine the working distance, the length of tools, objects or equipment should be taken into account:

— In case of live working, the consequence of the application of tools, devices or equipment is a reduction of the isolation distance in air. Thus, the length of the conductive part should be taken into consideration. In the formula, the conductive length of a tool, device or equipment is determined as “F” (see formulas in EN IEC 61472-2 and EN 61472).

— In case of working within or outside the vicinity zone, electrical, non-electrical work or construction work, the total length of the tools, objects or equipment should be taken into consideration as the outer limit of the corresponding zone should not be encroached. In the formulas, the total length of a tool, objects, or equipment is given as distance of the equipment “L” (see Formulae (4) and (5)).

A.2.4   Ergonomic considerations

A.2.4.1   General

Ergonomic considerations should take into account the normal and unintentional movements of personnel and equipment. Those ergonomic considerations will be applied in the determination of the ergonomic distances

A.2.4.2   Personnel

Ergonomic considerations for personnel are dependent on the working method, level of training, skill of the worker’s (W), type of construction, and such contingencies as normal and unintentional movement, and errors in appraising distances.

The possibility of errors being committed during the work depends on the working method being applied, human factors, effects of the environment and the extent to which the worker’s (W) actions are monitored.

Different work positions and methods will require different allowances for normal an unintentional movement, e.g. working beneath a conductor is less hazardous than working alongside it. The stability of the worker’s (W) position can also vary from task to task, e.g. working above the ground, compared with working on the ground. A complex or strenuous job is also more likely to divert the worker’s (W) attention away from observing the minimum approach distance for live working D_A or minimum working distance D_W.

A worker’s (W) physical, mental and emotional states are also possible causes for normal and unintentional movement. These factors are, in turn, influenced by the duration and strenuousness of the job, for instance, electrotechnical works require constant attention, both to the procedures and the minimum approach distance or minimum working distance, attention which can be distracted by other personnel.

A.2.4.3   Equipment

Ergonomic considerations of equipment should take account of normal and unintentional movements, displacement, swinging out, whipping or fall of conductors and/or equipment including but not limited to swinging out loads, carrying and lifting equipment, platforms etc.

A.2.4.4   Determination of minimum working distances

The minimum working distances D_WL and D_WV include an additional safety factor which as well takes typical normal and unintentional movements into account. Thus, additional safety is provided.

In the distance’s formulas, the ergonomic distance parameter is given:

— as D_E for the live working (see A.2.5)

— as E for working within and outside the vicinity zone (see A.2.6 and A.2.7).

A.2.5   Working distance for live working

During live working the working distance should be the one given in EN IEC 61472-2 and EN 61472 and maintained at all time and situations.

To calculate the minimum approach distance for live working D_A the following formulas may be used according to the voltage level

For low voltage, the distance D_U is 0 mm and the formula is:

D_A = D_E (1)

For voltage up to 72,5 kV, the floating conductive distance F is added if any and the formula is:

D_A = D_U + D_E + F (2)

For the voltages higher than 72,5 kV, the floating conductive distance F is included in D_U and the formula is:

D_A = D_U + D_E (3)

where

DA is the minimum approach distance for live working

DU is the electrical distance

DE is the ergonomic distance < live working > 

F is the floating conductive distance

A.2.6   Working distance for working within the vicinity zone

The formula below can be used to determine the working distance for working within the vicinity zone (see 6.4).

The minimum working distance within the vicinity zone D_WL should be established based on the distances in air and should be derived from D_L

When the work is carried out within the vicinity zone, an ergonomic distance should be taken into account.

For minimum working distance within the vicinity zone D_WL, the following Formula (4) may be used.
Depending on the respective system-related withstand voltage level for nominal voltages of the electrical installation, the Installation manager (IM) can decide to use a higher value than D_L.

D_WL = D_L + E + L (4)

where

DWL is the minimum working distance for working within the vicinity zone

DL is the live working limit distance

E is the ergonomic distance

L is the total dimension of the equipment, objects and tools to be used

NOTE The minimum working distance determined on the basis of D_L already covers some ergonomic aspects, which provides an inherent extra safety margin for D_WL.

An illustration is given in Figure A.1.

Key

DWL minimum working distance for working within the vicinity zone

DL live working limit distance

DV vicinity limit distance

E ergonomic distance (optional depends of the type of work)

L total dimension of the equipment, objects and tools to be used

Figure A.1 — Example for determination of the minimum working distance for working within the vicinity zone D_WL

A.2.7   Working distance for working outside the vicinity zone

The formula below can be used to determine the working distance for working outside the vicinity zone (see 6.5).

The minimum working distance outside the vicinity zone D_WV should be established based on the minimal acceptable distances in air and should be derived from D_V.

For this distance, the following Formula (5) may be used:

For the minimum working distance when the work is carried out beyond the distance D_V, as the distance with the bare live part is large, in most cases the ergonomic distance E may be neglected.

D_WV = D_V + E + L (5)

where

DWV minimum working distance for working outside the vicinity zone

DV vicinity limit distance

E ergonomic distance (optional depends of the type of work)

L total dimension of the equipment, objects and tools to be used

NOTE The minimum working distance determined on the basis of D_V already covers some ergonomic aspects, which provides an inherent extra safety margin for D_WV.

An illustration is given in Figure A.2.

Key

DWV minimum working distance for working outside the vicinity zone

DL live working limit distance

DV vicinity limit distance

E ergonomic distance (optional depends of the type of work)

L total dimension of the equipment, objects and tools to be used

Figure A.2 — Example for determination of the minimum working distance for working outside the vicinity zone D_WV

Replace the item “Classification c)” with the following:

Replace subclause B.3.2 with the following:

“Fog is considered thick where visibility is reduced to a level that endangers safety, particularly when the work controller (WC) does not have clear visibility of the workers (W) and the live parts on which, or in the vicinity of which, they should be working. Work should be interrupted in these conditions.”

Replace Clause B.6 with the following:

“B.6.1   General

Persons who work on or near electrical installations, and persons who are in the vicinity during work activities, are exposed to the risk of electric arc hazards. Electrical arcs are a rare event. Nevertheless, comprehensive mitigation of the risks associated with electrical arcs is required as their occurrence cannot be excluded, particularly during work activity. Electric arcs are not only caused by short circuits, but also when two live parts are being disconnected from each other (e.g. when installing/removing fuses or opening or switching a disconnector or circuit breaker) or flash-over due to insufficient isolation distance between live parts.

B.6.2   Hazards

The arc hazard is the potential harm from an energy release from an electric arc. The result of an arc can include thermal-, noise-, pressure wave-, ejected parts-, molten metal-, and optical effects.

The thermal impact of an electric arc depends on:

— the short-circuit capacity of the electrical installation, which determines the energy produced in the arc;

— the arc voltage;

— the arc current;

— the arc duration; and

— the heat flux transmission conditions including the exposure conditions and the distance to the arc.

The mode and intensity of heat transfer is not specific for certain voltage levels (low or high voltage).

Besides the thermal impact, the following hazards should be considered:

— shock wave and shrapnel which are released by the explosive force of the electrical arc;

— high intensities of an electromagnetic radiation particularly in the range of ultraviolet (UV) radiation and infrared (IR) radiation but also in the range of visible light which can lead to irreversible damages to skin and eye;

— acoustic shock which can lead to irreversible damages to hearing;

— toxic gases and particles that are caused by melting and vaporizing of materials within or in the environment of the electrical arc.

B.6.3   Risk assessment

Where personnel are present near a live electrical installation (including working in the vicinity or under live conditions) or if workers and other persons inside or outside the work location may be exposed to the hazards from an electrical arc, arc flash risk assessment should be carried out.

The risk assessment should consider all contributary factors and situations including but not limited to:

— the hazards including their causes and effects as described in B.6.2 above;

— the safe working distance and defined work location;

— the performances of the protective devices;

— the internal arc mitigation system, when present in the electrical installation;

— particular conditions during maintenance and repair work;

— particular conditions for work or inspection where parts of the electrical installation which provide protection against the effects of electric arcs, e.g. plates and doors of electrical switchgear, may be opened or even removed for a certain period of time.

If the arc flash risk assessment cannot be comprehensively completed or insufficient mitigation measures.

can be taken, all work should be carried out using the dead working procedures.

It is recommended as good practice that arc flash is considered as part of the design risk assessment process during the design phase so as to avoid invasive interventions on the installation at a later stage.

B.6.4   Personal Protective Equipment

Suitable personal protective equipment (PPE) can reduce the severity of the harm from electrical arc hazards and so contribute to the protection of personnel. However, it is important to note that there is no PPE available which provides one hundred per cent protection against the hazards of an electric arc. In certain circumstances however, the hazards of an electric arc can be significantly reduced or eliminated.

Only by calculating the electric arc energy can the thermal performance of the PPE necessary to mitigate the arc flash risk can be determined.

In the following cases the incident energy can be considered so low that arc flash PPE equipment is not required:

— the voltage is ≤ 400 V AC and the short circuit current is ≤ 1 kA;

— the voltage is ≤ 400 V AC or DC and the upstream fuse rating of the circuit is ≤ 63 A;

— the voltage is ≤ 50 V AC or DC.

However, even with very low incident energy, precautions against thermal effects and fragments should be applied, including protective eyewear and work clothing, consisting of long-sleeved outerwear and long pants, is recommended.

B.6.7   Guidance

Guidance for developing the arc flash risk assessment procedure, the calculation of the incident energy and/or the electric arc energy the use of PPE and assessing the arc flash hazard is available in, DGUV Information 203-077 or NFPA 70E (Annex D) or CSA Z462 (Annex D) or IEEE 1584 or IEC TC 78 guidelines documents listed in the Bibliography.

Internationally there are currently two different methods for arc flash testing and PPE clothing selection which are optionally applicable:

— Risk assessment and PPE selection for its arc rating (ATPV, EBT, ELIM) according to Open Arc Test method (IEC 61482‑1‑1);

— Risk assessment and PPE selection for its arc protection class (APC) according to Box Test method (IEC 61482‑1‑2).

The first method is based on the incident energy to be determined (see IEEE 1584, NFPA 70E etc.). The second method is based on the electric arc energy to be determined (see DGUV Information 203-077). DGUV Information 203-077 contains calculation procedures for both AC and DC systems, and for risk assessments as well. More detail is given also in the drafts of IEC standards TR 63375 and TR 63491.

A useful CENELEC reference for the arc flash risk assessment is under preparation. This document with the title “Arc Flash Risk Assessment” will consider different simplified calculation methods and data sheet examples that summarize the results considering various electrodes configurations inside a cubicle and in the air depending on the position of the electrodes (horizontal or vertical).”

Replace the 9th list item with the following

— Following an incident, the operation controller (OC) should take appropriate actions to secure a safe site and preserve, as far as is reasonably practicable, the site conditions intact. This is to ensure a robust accident investigation can be conducted either internally, or, in an extreme case, by external authorities e.g. police or safety regulators;

Replace the Table with the following:

“

“

Replace the Table with the following:

“

“

Add the following two documents:

“

IEC/TR 63375, Ed.1: Live Working - Technical report - Guidance for risk assessment, selection, use, care and maintenance or personal protective Equipment against the hazards of an electric arc - Part 1: Protection against thermal hazards of an AC electric fault arc

NOTE Document is under consideration.

IEC/TR 63491, Ed.1: Live Working - Technical report - Guidance for the selection, use and maintenance of electrical arc flash personal protective equipment”