GUIDE FOR IMPLEMENTING

DIRECTIVE 2013/35/EU
ON ELECTROMAGNETIC FIELDS
Implementation of the Directive 2013/35/EU on the minimum health and safety requirements
regarding the exposure of workers to the risks arising from physical agents (electromagnetic fields)

Asset Implementation 4/13/2016

This document is intended to help the European Transmission System Operators

(TSOs)/ ENTSO-E members implement the Directive. The objective is to explain how
to assess exposure and to evaluate compliance, and to indicate the most critical
­situations for transmission activities and formulate possible measures to be taken. 
 CONTENTS
1 EXECUTIVE SUMMARY........................................................................................3
2 INTRODUCTION................................................................................................4
2.1 Objective of the report ..................................................................................................................................................................4
2.2 Background of the Directive .........................................................................................................................................................4

3 DIRECTIVE 2013 / 35 / EU.......................................................................................5
3.1 Scope ...........................................................................................................................................................................................5
3.2 Effects of exposure to electric and magnetic fields ......................................................................................................................6
3.2.1 Direct effects ......................................................................................................................................................................6
3.2.2 Indirect effects....................................................................................................................................................................6
3.3 Exposure limit values and Action levels ........................................................................................................................................7
3.4 Exposure Limit Equivalent Field ...................................................................................................................................................7
3.5 Overview of the limits ..................................................................................................................................................................8
3.6 Limits for static fields ..................................................................................................................................................................9

4 EMPLOYERS’ OBLIGATIONS UNDER THE DIRECTIVE....................................................9

4.1 Assessment of risks and determination of exposure ....................................................................................................................9
4.2 Provisions aimed at avoiding or reducing risks ..........................................................................................................................10
4.3 Worker information and training ................................................................................................................................................10
4.4 Consultation and participation of workers ..................................................................................................................................10
4.5 Health surveillance .....................................................................................................................................................................10
4.6 Actions required for workers at particular risk ...........................................................................................................................11
4.7 Actions required to control contact currents and spark discharge ............................................................................................11
5 EXPOSURE SITUATIONS.................................................................................... 12
5.1 Substations ................................................................................................................................................................................12
5.1.1 Work at ground level in high-voltage areas........................................................................................................................12
5.1.2 Work above ground level in high-voltage areas..................................................................................................................13
5.1.3 Work outside high-voltage areas.......................................................................................................................................13
5.2 Insulated conductors .................................................................................................................................................................14
5.3 Towers .......................................................................................................................................................................................14
5.3.1 Climbing opposite side to live conductors........................................................................................................................14
5.3.2 Climbing past live conductors...........................................................................................................................................14
5.4 Live-line work on towers and in substations ..............................................................................................................................15
5.5 Cable tunnels or vaults ...............................................................................................................................................................16
5.6 Short-duration events (faults, switching transients etc) .............................................................................................................16
5.7 HVDC and other exposures to static fields .................................................................................................................................16
5.8 Summary of exposure situations ...............................................................................................................................................17

6 BIBLIOGRAPHY.............................................................................................. 18

ANNEX A : WORKERS AT PARTICULAR RISK................................................................. 18

A.1 Pregnant staff ..............................................................................................................................................................................18
A.2 Workers with Active Implantable Medical Devices .......................................................................................................................19

ANNEX B : “CONTACT CURRENT” METHOD FOR ASSESSING ELECTRIC FIELD EXPOSURES................................ 20
ANNEX C : ASSESSMENT METHODS FOR ELECTRIC FIELD EXPOSURES ON TOWERS WITH LIVE CIRCUITS................... 21
ABBREVIATIONS................................................................................................. 22
UNITS ............................................................................................................. 22
AUTHORS ......................................................................................................... 23

2 | ENTSO-E – EMF report

 1 EXECUTIVE SUMMARY
The European Union Directive 2013 / 35 / EU of 26 June 2013 on the minimum health and safety
requirements regarding the exposure of workers to the risks arising from physical agents
­(electromagnetic fields [EMF]) has to be transposed by EU Member States by 1 July 2016.

This document is intended to help the European Transmission System Operators (TSOs) /  ENTSO-E
members implement the Directive. The objective is to explain how to assess exposure and to
evaluate compliance, and to indicate the most critical situations for transmission activities and
formulate possible measures to be taken.

The Directive requires various administrative arrangements certain specific, more complicated, exposure situations. In
relating to worker information and training, maintaining for- addition to the exposure limits applying to staff in general,
mal exposure and risk assessments, health surveillance, etc. extra provisions apply to “workers at particular risk”, in par-
This report explains how a TSO can implement these with ticular pregnant staff and staff with active implanted medical
minimum extra work. devices, e. g., pacemakers, defibrillators etc. TSOs need to im-
plement appropriate measures in respect of these staff, if they
TSO exposure situations involve close approach to high volt- do not already do so, and this report suggests what measures
ages and currents, and therefore involve the potential for high are appropriate.
exposures to EMFs. This report considers the various TSO
exposure situations and either concludes that they are com- A simple summary table is provided at the end of the report,
pliant or suggests various methods a TSO could use to bring listing all exposure situations considered, and stating, for
them into compliance. In most cases, assessment can be by each one, whether they are compliant and what actions if
means of relatively straightforward calculations or measure- any are needed.
ments, but this report also suggests methods appropriate to

ENTSO-E – EMF report | 3

 2 INTRODUCTION
2.1 OBJECTIVE OF THE REPORT
The European Union Directive 2013 / 35 / EU of 26 June 2013 on The Directive covers frequencies from static (i. e. 0 Hz) to
the minimum health and safety requirements regarding the 300 GHz. Within this range, TSOs are most concerned with
exposure of workers to the risks arising from physical agents the power frequency (50 Hz in Europe), harmonics of the
(electromagnetic fields (EMF)) (EU, 2013) has to be trans- power frequency, and static fields (because of HVDC). TSOs
posed by the member states by 1 July 2016. It replaces and also have equipment that operate at radiofrequencies (com-
repeals Directive 2004 / 4 0 / EC of 29 April 2004 which never munications devices), but such equipment is general to any
actually took effect. industry and not specific to TSOs, so is not covered in this
report. Likewise, TSOs may use welding techniques that
This document is intended to help the European Transmission involve high exposures, but these are general to any industry
System Operators (TSOs) / ENTSO-E members implement the and are not covered here.
Directive. The objective is to explain how to assess exposure
and to evaluate compliance, and to indicate the most critical This Report presents the structure and scientific rationale
situations for transmission activities and formulate possible of the Directive in section 3. It then explains the obligations
measures to be taken. Some of the material is also relevant to placed on employers in section 4, then considers the various
distribution networks, but this Report does not systematical- work activities likely to be undertaken by TSOs and what
ly cover distribution operations. actions might be necessary under the Directive for each one
in section 5.
This guide deals specifically with assessment of risks for
workers concerning EMF. However, it is vital when assessing
these risks and when proposing different measures that other
risks do not increase and that the total risk level remains the
same or decreases.

2.2 BACKGROUND OF THE DIRECTIVE

Directive 2004 / 4 0 / EC, sometimes also referred to as the The Directive is mainly focused on prevention and is based on
“EMF Directive”, was published on 24 May 2004 and had to be the same principles as the Framework Directive 89 / 391 / EEC
transposed into national law by 30 April 2008. However, this on “the introduction of measures to encourage improvements
directive caused quite some commotion, in particular in the in the safety and health of workers at work”, namely the re-
medical world, by seriously calling into question the applica- sponsibility of employers for their workers’ health and safety,
tion of certain medical imaging-based procedures, prompting for risk analysis, for risk limitation measures, for information
the Commission to ask the European Parliament to repeal the and training and so on (EU, 1989).
directive. The updating of the scientific basis covering the low
frequency range (new ICNIRP guidelines were published in
2010) (ICNIRP, 2010) (ICNIRP, 2009) resulted in the withdraw-
al of the 2004 Directive and its replacing with Directive
2013 / 35 / EU (hereafter “the Directive”) (EU, 2013).

4 | ENTSO-E – EMF report

 3 DIRECTIVE 2013 / 35 / EU
3.1 SCOPE
In terms of the frequency range, the Directive concerns Besides these direct effects, some indirect effects are also cov-
electromagnetic fields from 0 to 300 GHz and applies to all ered. “Indirect effects” mean effects caused by the presence
occupational sectors. It defines exposure limit values (ELVs) of an object in an electromagnetic field, which may be cause
and action levels (ALs) equivalent to, respectively, the Basic of a safety or health risk, such as interference with medical
Restrictions and Reference Levels of the ICNIRP guidelines devices / implants, electric shocks and contact currents.
(ICNIRP, 2010) (ICNIRP, 2009).
Workers with medical implants, along with pregnant workers,
Potential long-term effects are excluded from the scope are considered as persons at particular risk and require
as there is insufficient scientific evidence in this regard. appropriate precautions and protective measures. This is
considered more in detail in section 4.6
Unlike the 2004 directive, but consistently with the updated
scientific basis, the new Directive introduces two distinct The Directive applies solely to occupational exposure. For the
thresholds for both the exposure limit value and the action protection of the general public, the Council Recommendation
level. 1999 / 519 / EC represents the framework at European level
(EU, 1999). According to the Directive, workplaces accessible
The first (lower) level has to do with sensory effects. At low to general public which meet the reference levels specified in
frequencies, these relate to transient problems with sensory the Recommendation do not require further exposure assess-
perceptions and to minor temporary changes ( for the dura- ment. Also, workers at particular risk will normally be ade-
tion of the exposure only) in brain functions. The most sensi- quately protected by compliance with the reference levels
tive such effect, for magnetic fields, is magnetophosphenes specified in the Council Recommendation.
(the appearance of light flashes in the vision). The safety mar-
gins included in the limits in the Directive are such that these All the requirements in the Directive are deemed minimum
phenomena should never be experienced during normal TSO requirements that guarantee a sufficiently high level of pro-
work activities. These effects are produced by exposure of the tection in relation to the considered effects. Member States
central nervous system (CNS), in other words exposure of the are given the licence to adopt these requirements at national
head (brain, retina). level or promulgate stricter requirements for the protection
of workers.
The second (higher) level has to do with health effects. At low
frequencies these relate to adverse effects mainly attributable
to stimulation of nerve and muscle tissue. The thresholds for
these effects are even higher than for sensory effects, and
again, they should never be experienced during normal TSO
work activities. This mainly affects the peripheral nervous
system (PNS), in other words the whole body.

ENTSO-E – EMF report | 5

 3.2 EFFECTS OF EXPOSURE TO ELECTRIC AND MAGNETIC FIELDS
3.2.1 DIRECT EFFECTS 3.2.2 INDIRECT EFFECTS
The only direct interaction between low-frequency electric Indirect effects occur where the presence of an object within
and magnetic fields and living tissues takes place through in- an electromagnetic field may cause a safety or health hazard.
duced electric quantities (currents and voltages). A cur- Examples of indirect effects are interference with worn medi-
rent that is induced in living tissue is characterised by its den- cal devices (see section 4.6 and Annex A), electric shocks, or
sity (J, expressed in ampere per square metre A / m²), which burns from contact currents.
corresponds to the current that passes through a unit surface
perpendicular to the direction of the current. However, to es- Microshocks
tablish the exposure limit values, the internal electric field When a person and a close conducting object or structure
(mV / m) is used instead of current density as it is considered are both exposed to a high electric field, they may be at differ-
as the relevant biophysical parameter to characterise the ent potentials depending on their respective sizes, positions
excitation of nerves (ICNIRP, 2010). in space, and grounding conditions. This can cause spark dis-
charges (also known as microshocks) at the instant when
The currents and electric fields induced in the body are at contact is made by a person to a conducting object, if the per-
their maximum in the case of homogeneous external fields son and the object are at different potentials. This commonly
running, for electric fields, parallel to the body, and, for mag- arises when one out of the person and the object is grounded
netic fields, perpendicular to the body. In other words, all the and the other is not. The peak value of the current during a
models that are used to establish the limit values are based microshock can be several orders higher than the subsequent
on the use of homogeneous fields which are regarded as the continuous contact current, but the duration is very short
most critical exposure situation. and the total energy low, comparable to the energy in a static
shock when touching a metal object after walking across a
Electric field inside Magnetic field inside synthetic carpet.
body Ei « E outside body same as outside
This indirect effect of electric fields does not generally have
any lasting effect on the body. However, spark discharges can
be painful, which in turn creates the risk of a startle reaction
(particularly hazardous when working at height). Only excep-
tionally, if a spark discharge occurs multiple times to the
Ei, J
same point of the skin, would damage, e. g. small burns to the
Ei, J skin, occur.

Contact currents
Once the contact is established, the spark discharge is re-
placed by a continuous contact current. The Directive limits
contact currents to 1 mA. This could be exceeded on touching
a large ungrounded object such as a vehicle or fence, and
steps should be taken to ground all such objects in areas of
high electric field.

The typical working

situations where con-
tact currents occur
Electric field lines Magnetic field lines
E V/m H A/m
are (i) an insulated
person (e. g. a worker
Induced current density J mA/m 2 and internal electric field Ei V/m wearing security
shoes) exposed to an
The figures illustrate the induction mechanism for an individ- electric field and
ual who is exposed to a vertical electric field and to a horizon- touching a grounded
tal magnetic field, such as may occur at ground level under a object and (ii) an insulated object (e. g. a vehicle) touched by a
high-voltage line. In the first case (E-field) a current passes grounded person (see figure).
through the body and is then taken away by the ground, in
the second case (H-field) the current forms a closed loop in Furthermore, any contact with any lengthy structure that is
the individual’s body. under the magnetic influence of a live high-voltage line may
also result in an electric shock and a contact current. This
magnetic induction effect is a well-known safety issue for
maintenance tasks of HV lines and it is normally covered by
existing safety / security rules. Actions to prevent contact cur-
rents and spark discharges are presented in section 4.7.

6 | ENTSO-E – EMF report

 3.3 EXPOSURE LIMIT VALUES AND ACTION LEVELS
If the occupational exposure conditions comply with the pro- In general, when the ALs are not exceeded, the exposure is
visions on the limitation of exposure of the general public deemed to comply with the ELVs and further assessment is
(1999 / 519 / EU), they will also comply with the action levels not needed. However, the article 3 of the Directive states
set in this Directive and therefore it is not necessary to carry that, when justified by the practice or process, exposure may
out an assessment. exceed the ALs provided that the relevant ELVs are not ex-
ceeded. More specifically regarding electric or magnetic field
As mentioned in section 3.1 a distinction is made between exposure :
sensory (CNS) and health (PNS) effects, and accordingly two
levels of exposure limit values (ELVs) are introduced. The first For electric fields the Low and High ALs may be exceeded if :
(lower) level applies to the head (CNS) and the second (high-
er) level applies to whole body (PNS), at power frequency i. spark discharges are limited or measures for limiting
respectively 100 and 800 mV / m. Since the ELVs are internal spark discharges have been taken;
body quantities (mV / m) which cannot be measured straight- ii. the contact currents are not excessive;
forwardly or simply calculated, the Directive introduces iii. the workers have been properly informed;
action levels (ALs) in term of external field quantities which iv. the health effects ELVs are not exceeded 1).
can be measured or calculated much more easily.
For magnetic fields the Low AL may be exceeded :
The basic idea is that employers must ensure that they limit
any risk to their workers. This is achieved by limiting expo- a) if the ELV for sensory effects are not exceeded,
sures below the relevant exposure limits, but there is no re- b) or if :
quirement to reduce exposures further below the exposure
limits. For general workers it is sufficient to ensure that the i. the sensory effects ELVs are exceeded only temporarily;
field or contact current levels remain below the ALs (except ii. appropriate action is taken in the case of transient symp-
for workers at particular risk). If the ALs are exceeded, em- toms;
ployers must either demonstrate that the ELVs have not been iii. the workers have been properly informed.
exceeded or take appropriate action to limit the exposures.
For magnetic fields the High AL may be exceeded if :

LAL HAL i. the above conditions are met

ii. the health effects ELVs are not exceeded
Electric field 10 kV/m 20 kV/m
1) In ICNIRP Guidelines from 2010 (ICNIRP, 2010) different spans of conversion fac-
6,000 µT
Magnetic field 1,000 µT tors are given between external electric fields and induced internal electric fields for
(18,000 µT for limbs)
sensory effects (CNS) and health effects (PNS). The worst case conversion factor for
CNS which gives the lowest external electric field yields ~38 kV/m. Hence at the pow-
Contact current 1 mA
er frequency the level of sensory effects can never be subjected to comparison with
Low or High AL. In reasonable cases the level of the external electric field that corre-
Table 1 : Overview of action levels at 50 Hz (RMS) sponds to sensory effects is higher than the corresponding field for health
effects, therefore are the sensory effects omitted in the text concerning electric fields.

3.4 EXPOSURE LIMIT EQUIVALENT FIELD

When ALs are exceeded, it is necessary to assess compliance ELVs for sensory or health effects. When this Standard is pub-
against the ELV. The assessment of the electric field induced lished, which is expected in 2016, TSOs are recommended to
inside the body requires the use of dosimetric studies, i. e. adopt the values of the LEFs given in it, although alternative
sophisticated models of human bodies and electromagnetic scientifically based values are equally acceptable. One possi-
computation software. The result of such studies is to estab- ble alternative way of deriving the LEFs would be to use the
lish an equivalence relation between the external field and dosimetric values stated by ICNIRP (ICNIRP, 2010), which
the induced electric field (or induced current) inside the body. would result in a LEF for the health ELV of 24–66 kV/m and
This relation depends on the model, on the orientation and 13–40 mT. The corresponding LEF for sensory effects based
the coupling of the external field to the body. on ICNIRP would be 1–3 mT. The fact that ICNIRP give only
a range, not a single value, makes practical use of values de-
The Exposure-Limit-Equivalent-Field (LEF), as defined in a rived from ICNIRP difficult, and TSOs are likely to prefer the
draft CENELEC standard 2) (CENELEC, 201X), is the lowest single values in the CENELEC standard when these become
homogeneous (i. e. uniform) external field value, derived on available.
the basis of scientific literature, which induces internal elec-
tric field values equivalent to the ELVs. Different LEFs can be 2) Pr EN 50647, dealing with occupational exposures in electrical companies
defined for electric and magnetic fields and regarding the

ENTSO-E – EMF report | 7

 3.5 OVERVIEW OF THE LIMITS
The following diagrams indicate the Action levels and Exposure-Limit-Equivalent-Fields explained in the previous sections.
The diagrams also summarise the actions required at these different levels. These actions are discussed in more detail in section 4.

ELECTRIC FIELDS ACTIONS REQUIRED REFERENCE ARTICLES OF THE DIRECTIVE

Immediate measures to reduce fields and amend procedures to

prevent repeat [5(8)] or
Derogation under 10(1)(c) or
NOT PERMITTED Temporarily exceed:
Unless granted derogation Specific cases and duly justified circumstances, take action to
return to compliance as soon as possible (recital 22)
24 –66 kV/m LEF
PERMITTED
If compliance to exposure limit
Values is demonstrated
20 kV/m High AL

Excessive spark discharges and

contact currents prevented
PERMITTED [3(3)(a)] and
Subject to administrative provisions Special protection measures Signs unless access limited
[5(6)] for other reasons [5(5)] and
signs / information / consultation /
Information for workers [6]
health surveillance and
Permitted under Consultations [7] and
3(3)a and 3(3)b with Appropriate health
Action Plan under [5(2)] surveillance [8]
10 kV/m Low AL

PERMITTED
Exposure assessment required Exposure assessment [4]
By competent persons at Action Plan for workers at
suitable intervals [4(6)] particular risk [5(3)]
5 kV/m Public exposure limit

PERMITTED No exposure assessment needed [4(6)]

No exposure assessment needed

MAGNETIC FIELDS ACTIONS REQUIRED REFERENCE ARTICLES OF THE DIRECTIVE

Immediate measures to reduce fields and amend procedures to

prevent repeat [5(8)] or
Derogation under 10(1)(c) or
NOT PERMITTED Temporarily exceed:
Unless granted derogation Specific cases and duly justified circumstances, take action to
return to compliance as soon as possible (recital 22)
13–40 mT LEF
PERMITTED
If compliance to exposure limit
values is demonstrated
6 mT (18 mT) High AL
Permitted under 3(3)(b):
If temporary;
Preventive measures; if
PERMITTED workers report symptoms, if
Subject to administrative provisions necessary [5(9)] Signs unless access limited
information provided for other reasons [5(5)] and
signs / information / consultation /
Information for workers [6]
health surveillance and
Permitted under Consultations [7] and
3(3)a and 3(3)b with Appropriate health
Action Plan under [5(2)] surveillance [8]
1 mT Low AL

PERMITTED
Exposure assessment required Exposure assessment [4]
By competent persons at Action Plan for workers at
suitable intervals [4(6)] particular risk [5(3)]
0.1 mT Public exposure limit

PERMITTED No exposure assessment needed [4(6)]

No exposure assessment needed

8 | ENTSO-E – EMF report

 3.6 LIMITS FOR STATIC FIELDS
The preceding discussion relates to exposures at power fre-
ELVs ALs quencies. The Directive also gives limits for static fields (note
that for static fields, unlike alternating fields, the ELVs are ex-
Normal working conditions, sensory effects 2T pressed in terms of the external field) :

Localised limb exposure, sensory effects 8T These limits cover both the direct effect of the magnetic field
on the body, and also effects caused by motion of the body
Controlled exposure, health effects 8T through a static field.

Workers with active implanted medical No limits are given for static electric fields.
500 µT
devices

Attraction and projectile risk in the fringe

3 mT
field of highfield strength sources (> 100 mT)

Table 2 : Overview of exposure and action levels for static fields

4 EMPLOYERS’ OBLIGATIONS UNDER THE

DIRECTIVE
4.1 ASSESSMENT OF RISKS AND DETERMINATION OF EXPOSURE
Employers are required to “assess and, if necessary, measure formed 1 m above ground; if other heights are used, the actual
or calculate” the levels of electromagnetic fields to which height should be recorded. Measurements of electric fields
workers are exposed. If they determine that the action levels should keep to a minimum distance from metallic structures
have been exceeded, they will either evaluate if provisions to of 20 cm to avoid proximity effects.
reduce exposure under action levels can be taken (ref. 4.2), or,
alternatively, they will assess and, if necessary, calculate, the In some circumstances, e. g. for work on towers or above
actual exposure levels to check whether the limit values ground in substations, electric field measurements are prob-
themselves have been exceeded, as described in 3.3 above. lematic because the electric field is highly non-uniform.
The assessment must be carried out by competent ser­vices or An alternative technique in these situations is to measure
person. If no action is required, this too should be document- contact currents as a proxy for electric field. It is described
ed. in Annex B, and its application to work on towers is described
in Annex C.
When measurements are used either a broadband or a 50-Hz-
only measurement should be taken; harmonics should be Section 5 of this Guide lists those exposure scenarios that a
ignored. Measurements protocols should be according to IEC TSO is likely to need to assess, and indicates what the find-
measurement standards (IEC, 2009) (IEC, 2013) (IEC, 2014). ings of the assessment are likely to be.
Measurements ( for activities at ground level) should be per-

ENTSO-E – EMF report | 9

 4.2 PROVISIONS AIMED AT AVOIDING OR REDUCING RISKS
When assessment shows that the limit values have been be limited where technically possible; however this is not re-
exceeded, employers must take any appropriate measures quired if access is already restricted for other reasons, which
to reduce the exposure below the permitted levels (e. g. other is always the case at substations and towers, so no signpost-
alternative working methods, measures to reduce the emis- ing should be necessary for TSOs.
sions of electromagnetic fields, use of the appropriate person-
al protection equipment, etc.). Employers must also tailor the measures to the requirements
for workers at particular risk. Section 5 of this Guide indicates,
Locations where there is a risk of exceeding the action levels for each exposure scenario, what actions, if any, are likely to
must be appropriately signposted, and access to them must be necessary.

4.3 WORKER INFORMATION AND TRAINING

Employers must ensure that workers (and their representa- these risks. It will be necessary to explain the measures
tives) receive any necessary information and training relating implemented to reduce the risks, particularly where these
to the outcome of the risk assessment (e. g. plans, limit values, require action by workers.
action levels, assessment results, action taken, safe working
methods, health surveillance, etc.). Convenient practice is to Workers should be informed of their responsibility to inform
combine it with the existing safety training. It is important, in their employer if they have an implanted medical device or if
any case, that any training should put EMF risks into perspec- they are pregnant (these are discussed in more detail in 4.6)
tive with other risks in the workplace.
Information and training of workers, as well as health sur­
Where staff exceeds the Sensory Effects ELV, there is the the- veillance, must be weighted and tailored according to their
oretical possibility of them experiencing transient symptoms specific tasks and duties. Measures identified to reduce expo-
of sensory effects. The effects that would be expected to be sures under specific tasks must be clearly explained.
the first to be noticed are “phosphenes”, a flickering sensation
round the periphery of the vision, followed, at even higher In case of presence of visitors and external workers in work-
fields, by giddiness or nausea. TSOs need to inform workers places which don’t meet limits for general public, basic infor-
of these possibilities, and to have a system for workers to mation must be provided by an appropriate method (e. g.
report these symptoms if they occur. Note, however, that distributing sheets or verbally).
because of the safety margins included in the exposure limits,
these symptoms are very unlikely in practice. The provision of information and training should be docu-
mented. Contractors and subcontractors should be required
Where there are risks of spark discharges or contact currents, to operate equivalent systems for their own staff.
information and training will need to specifically identify

4.4 CONSULTATION AND PARTICIPATION OF WORKERS

Provision must be made for the consultation and participation of workers or of their representatives.

4.5 HEALTH SURVEILLANCE

Long-term or routine surveillance is not required by the When a health examination is required, there are no specific
Directive. signs of over-exposure to look for, so the examination can be
general in nature.
An appropriate health examination is required when workers
report health effects or when the health ELV is exceeded. The In addition to normal national requirements, the Directive
Directive also provides for a health examination if the sensory requires that the results of health surveillance shall be pre-
effects ELV is exceeded and transient sensory symptoms are served in a suitable form that allows them to be consulted
reported. These symptoms are permitted by the Directive, but at a later date, subject to compliance with confidentiality
are unlikely to occur in practice at exposure levels occurring requirements; that individual workers shall, at their request,
within TSOs. have access to their own personal health records; that such
examinations or surveillance shall be made available during
hours chosen by the worker, and that any costs arising shall
not be borne by the worker.

10 | ENTSO-E – EMF report

 4.6 ACTIONS REQUIRED FOR WORKERS AT PARTICULAR RISK
The Directive recognizes a category of “workers at particular For pregnant workers, a simple and sufficient approach is to
risk”. These workers may not be adequately protected by the allow or to require them to be subject to the public limits
ALs and ELVs that protect staff in general, and TSOs should instead of the occupational limits for the duration of their
perform separate assessments where appropriate. pregnancy.

The Directive considers two categories of workers at particu- For staff with active implanted medical devices, TSOs should
lar risk : workers with active implanted medical devices take adequate steps to ensure that staff with these devices
(AIMDs), and pregnant workers. Further information on the does not enter areas where there are fields high enough po-
issues affecting these workers is given in Annex A. tentially to cause interference. This can be achieved through
various combinations of identifying the workers affected and
In both cases, the public exposure limits are normally consid- marking the areas, as described in Annex A.
ered to provide adequate protection. So no further assess-
ment is needed for these staff in areas that comply with the
public exposure limits, e. g. offices.

4.7 ACTIONS REQUIRED TO CONTROL CONTACT CURRENTS

AND SPARK DISCHARGE
The Directive does not give any quantitative limit regarding »» wearing conducting boots and socks (this is advisable on
transient spark discharges or microshocks, but as they can be towers but not in substations as step-potential may raise
painful, it is required to take adequate protective measures to during faults)
prevent their occurring. For continuous contact currents it »» use of conducting harnesses for work above ground with
gives an Action level of 1 mA. The Directive requires steps to suitable grounding straps or clips.
control these indirect effects of electric fields when the LAL »» If workers cannot be at the same potential as the object
(10 kV/m) is exceeded. This is, in practice, comparable to the they are about to touch, making contact in a way that
field level at which workers would often start reporting spark minimizes pain :
discharges, and therefore at which a TSO would already be »» by making firm and rapid contact;
taking appropriate measures, separately from the Directive. »» by making contact with the forearm (or some other less
sensitive part of the body) rather than the fingers;
Typical steps that a TSO can take to control these indirect »» by making contact with a metal tool that is itself grasped
effects include : firmly with the whole area of the hand.

»» Ensuring that workers are well grounded, and thus at the

same potential as towers, substation structures, etc, all of »» If neither of those is possible, by screening of the field.
which are usually also well grounded. Measures to ground
workers include : »» Ensuring that workers are informed of the origins and
­consequences of spark discharges, which can increase
their acceptance of them by removing the element of the
unknown.

ENTSO-E – EMF report | 11

 5 EXPOSURE SITUATIONS
Here are described the typical exposure situation for a worker these exposure situations trigger the need for worker infor-
in a TSO, distinguished for workplaces and equipment, possi- mation as described in 4.3. Where measurements are re-
ble critical point and necessary actions. In addition to the quired, they should follow the provisions of section 4.1.
specific actions identified for each exposure situation, all

5.1 SUBSTATIONS
5.1.1 WORK AT GROUND LEVEL IN HIGH-VOLTAGE AREAS
ii. Individual items of equipment (transformers, circuit
breakers, current transformers etc)

Both Magnetic and Electric fields : Except where air-cored

reactors or air-cored transformers are involved, there is no in-
dividual item of equipment in substations that produces any
higher fields than the busbars connecting it.

»» Assessment : no further specific assessment of individual

items of equipment is needed beyond the general assess-
ment of the substation.
»» Action : no action needed.

The controls put in place for workers at particular risk

or substations in general will cover transformers, circuit
breakers etc.
i. Busbars

Magnetic fields are almost certain to be below the Low AL

(and most often below the reference level for the public :
100 µT) except where air-cored reactors are present or where
close approach to insulated conductors is possible, both of
which are considered separately below.

»» Assessment : the fields are likely to be so far below the

Action level that no further assessment is needed.
»» Action : No further action should be necessary.

Electric fields in substations below 380 / 4 00 kV will be lower

than the HAL (20 kV/m) and no further action is necessary. In
400 kV substations electric fields can be as high as 20 kV/m
(or even higher at higher voltages). If fields exceed the HAL, iii. Air-cored reactors
assessment shall be done with ELVs, deriving an Exposure
Limit Equivalent Field (LEF). Magnetic fields : Equipment with large air-cored reactors
(Static Var Compensators, Series Capacitor installations, filter
»» Assessment : measurements should be performed to con- coils for HVDC Convertors etc) produce high magnetic fields,
firm that the fields are below the HAL or LEF. The highest which can be capable of exceeding the HAL and the Limit
fields will be found where two adjacent busbars are of the Equivalent Field as well.
same phase.
»» Action : Avoidance of excessive microshocks and contact »» Assessment : Fields can be calculated if the geometry and
currents is necessary, but existing rules and practices rating of the coils is known. Manufacturers are able to sup-
should already address these issues (as detailed above in ply these calculations for new installations and requiring
4.7). No further action should be necessary. this should become standard practice when the Directive
will be in force. Calculation results can be presented as
Electric fields will almost certainly exceed the public levels contour lines of either the Low and High AL and any other
relevant for workers at particular risk, requiring a separate relevant threshold, such as the LEF.
assessment. Fields can also be measured, either at the point of highest
field or at the closest accessible point. In both cases, the

12 | ENTSO-E – EMF report

 highest field will normally correspond to the maximum lows walking up to and underneath the coils. In this case,
load; at maximum load the waveform is likely to be a a barrier may need to be erected purely for the purposes of
reasonably pure 50 Hz sinewave and the harmonics can restricting magnetic fields. If a barrier is needed, it should
be ignored, while at lower loads, harmonics cannot be be clearly distinguished from barriers used for high-voltage
ignored. safety clearances, so that staff do not confuse. The existing
Scaling to maximum load measurements taken with designation of a “hazard zone” may be suitable.
harmonics is not trivial and requires expert knowledge.
»» Action : The layout of such coils varies. Sometimes the coils Electric fields : Such coils do not produce any higher
are mounted above ground on insulators at a height de- electric fields than busbars in substations in general.
signed only to provide flashover clearance above ground.
Approach to these coils will already be restricted for volt- »» Assessment : no further assessment needed.
age safety reasons. It is likely that the barrier already erect- »» Action : no further action needed.
ed for this purpose will be sufficient to keep staff out of the
area where high magnetic fields are found, in which case Magnetic fields are highly likely to exceed the public levels
no further action will be needed. relevant for workers at particular risk, at distances well be-
An alternative design has the ground potential end of the yond the contour calculated for the Action Level or Limit
insulators mounted on grounded posts of a height that al- Equivalent Field, requiring a separate assessment.

5.1.2 WORK ABOVE GROUND LEVEL IN HIGH-VOLTAGE AREAS

Magnetic fields : Except for live working at bare hand or for »» Assessment : When making electric fields measurements it
insulated conductors, which are considered separately, high- is therefore recommended to keep a minimum distance to
voltage safety clearance distances will ensure that busbars the metallic structure (20 cm recommended) and to average
cannot be approached closely enough to exceed the low AL. the measurements over the workers body. Alternatively,
measurements of the total contact current between the
»» Assessment : the justification comes from calculations worker and the grounded structure can be used as a proxy
as set out for example in the CENELEC Standard. for electric fields measurements as detailed in Annex B.
»» Action : no action needed. »» Action : Many situations will be found to be compliant, but
if these assessments show that the ELVs are exceeded, ac-
Electric fields : When working above ground level in substa- tion to reduce the exposure should be taken, by screening
tions (e. g. close to switchgear equipment), electric fields sig- the field or by providing conducting suits for workers.
nificantly higher than HAL can be measured, but these fields
are highly non homogeneous and the highest values are Fields are highly likely to exceed the public levels relevant for
linked to the peak effect which can be observed close to workers at particular risk, requiring a separate assessment.
metallic structures. Therefore, these high values are deemed
to overestimate the actual exposure of workers.

5.1.3 WORK OUTSIDE HIGH-VOLTAGE AREAS

High-voltage substations sometimes have an outer perimeter
fence, enclosing car parks, offices, stores, etc. Within this is a
separate high-voltage area enclosed by a separate fence with CAR PARK OFFICE
access controls. All high-voltage equipment is within this in-
ner area, and any busbars or lines passing over the outer area
GARAGE

are at higher clearance.

This subsection addresses exposures outside the high voltage

area but still within substation perimeter.

»» Exposures outside the high-voltage area are very unlikely to

STORE

exceed the Action Levels.

»» It is possible for the fields to exceed the public levels rele-

vant for workers at particular risk, requiring a separate High-voltage safety fence
assessment. This could happen, for magnetic fields, if an
air-cored reactor is located close to the perimeter of the
high-voltage area, if underground cables cross an accessi-
ble area and, for electric fields, if there are unusually low-
clearance conductors or busbars immediately outside
the high-voltage area. Site-specific assessments may be
needed.

ENTSO-E – EMF report | 13

 5.2 INSULATED CONDUCTORS
Radius Magnetic field Magnetic field Magnetic field
Cable Current rating of the cable at contact at contact + 1 cm at contact + 4 cm

90 kV 1,000 A 4,2 cm 4.8 mT 3.8 mT 2.4 mT

220 kV 1,500 A 6,0 cm 5.0 mT 4.3 mT 3.0 mT

400 kV 1,800 A 7,5 cm 4.8 mT 4.2 mT 3.1 mT

Table 3 : The magnetic fields generated by typical cables at current rating

Magnetic fields : Insulated cables, for example where an un- ing) after taking account of these separations for typical
derground circuit enters a substation and leaves the ground, largest cables in use at various voltages are shown in this
or where transformer tails enter the ground, can carry typi- table 3.
cally up to 1.8 kA and are typically of outer radius 7.5 cm and The field is always below the HAL and hence the health
can therefore be approached so closely. This potentially gives ELV. The calculated values of field exceed the LAL, but this
rise to magnetic fields on their surface of several mT. Howev- is a worst case calculation, because it takes no account
er, the field falls with distance quite rapidly, approximately of the cancelling effect of the other currents making up
with factor of 1 / d. the circuit nor of the variation of field across the tissue in
question.
»» Assessment : Measurements can be performed, but are dif- »» Action : no action needed.
ficult to interpret, because of the issue of the size of the
measuring probe in relation to the distance over which the Electric fields : Such cables always have a conducting
field falls off. Calculations are preferable. Only the 50 Hz outer layer that screens the electric field.
component should be considered; harmonics should be ig-
nored. For the LAL and sensory ELV, it should be assumed »» Assessment : no further assessment needed.
that the thickness of the skull and helmet ensure the brain »» Action : no further action needed.
is a minimum of 4 cm from the surface of the cable; for the
HAL and health ELV, it should be assumed that the thick- Magnetic fields very close to such conductors are highly likely
ness of clothing means the skin is a minimum of 1 cm from to exceed the public levels relevant for workers at particular
the surface of the cable. The field calculated (current rat- risk, requiring a separate assessment.

5.3 TOWERS
5.3.1 CLIMBING OPPOSITE SIDE TO LIVE CONDUCTORS Electric fields : Electric fields can be high, and clearly above
the High Action level and Limit Equivalent Field. Measure-
»» Both electric and magnetic fields : it is unlikely that any
ments in the vicinity of tower steelwork are unreliable, but
exposures exceeding the Action Levels will be experienced
fields of 30 kV/m or even higher have been measured on
when climbing a tower either on the opposite side to the
400 kV towers. However, the field is aligned, broadly speaking,
live conductors or inside the body of the tower.
horizontally through a linesman’s vertical body (see figure in
annex C), an orientation where the coupling is less strong
»» For workers at particular risk, requiring a separate
then the reference one (person standing at ground level and
assessment
exposed to a vertical field). So the field measurements in
excess of the Action levels does not necessarily indicate ex-
5.3.2 CLIMBING PAST LIVE CONDUCTORS ceeding of the exposure limits values.
Magnetic fields : If climbing on the body of the tower past live
»» Assessment : alternative assessment methods are
conductors is permitted at all, high-voltage safety clearance
available, and are detailed in Annex C.
distances will ensure that conductor cannot be approached
»» Action : It is likely that, using one of the above alternative
closely enough to exceed the High / Low Action Levels.
methods, this activity will be demonstrated to be compliant,
and therefore no further action is needed.
»» Assessment : No further assessment needed. Calculations
can be used to confirm if necessary.
The electric field in this exposure situation is highly likely to
Action : no action needed.
exceed the public levels relevant for workers at particular
risk, and the magnetic field may do so as well, requiring for
both a separate assessment.

14 | ENTSO-E – EMF report

 5.4 LIVE-LINE WORK ON TOWERS AND IN SUBSTATIONS
All maintenance performed on electrical equipment executed This simple approach can be adapted to other situations (e. g.
while the equipment is energised is designated as live-line bundles of conductors, bigger conductors such as busbars).
work. At present, two basic techniques of live-line work are
used by TSOs for work on overhead lines or in substations : the »» Assessment : for all the work situations where the simpli-
“distance technique” (or “hot stick” working) and the “contact fied assumption of the straight conductor is applicable,
technique” (or “bare hand” working or “hot glove” working). the simple assessment method described previously can be
applied. For more complex exposure situations the most
The “hot stick” technique requires that the workers directly appropriate assessment method is numerical dosimetry.
involved be kept at ground potential and operate from the Several such calculations for geometries specific to live-line
tower on live parts by using special insulating tools. work have been published.
»» Action : basically, applying the Directive will consist in
The “contact technique”, which is the more common technique translating the field limits into current and distance rules :
used for 220 and 380 kV lines, requires that the operators, who whatever the assessment method (simplified calculation
wear suitable protective conductive overalls, reach the same or dosimetric study) it finally results in calculating the con-
potential as the live parts on which they must operate and uti- ditions of current and distance at which the considered
lize hand-held metal tools. The conductive overalls provide a limit (AL or LEF or any other applicable limit resulting from
screen from electric fields (but not from magnetic fields). specific dosimetric studies) is met. If the risk assessment
shows that the limits can be exceeded then further actions
will have to be defined for managing the two action param-
HOT GLOVE OR BARE HAND
eters : current and distance.
Magnetic fields : Live-line works, like close approach to For example, permanent monitoring of the current can be
insulated conductors in substations considered above, in- required if the estimated current during the live-line opera-
volve close approach to high currents, and hence to high tion is in the order of the “Action Level” for the current
magnetic fields that fall rapidly with distance. It should also (500 A for a single conductor). Alternatively, if such moni-
be considered that live-line working situations imply close toring is not possible, safety equipment ( for example a tube
proximity (in fact, contact) to one conductor and safety dis- 5 cm thick) can be positioned around the conductor to in-
tance to the other phases; exposure from the other phases crease the contact distance so that the exposure limit will
can therefore be neglected. not be reached whatever the current.

Considering a single conductor for simplification, this close Electric fields : bare-hand live-line work is only undertaken
proximity to the conductor also means that the conductor when wearing a conducting suit or some other method
can most often be modelled by a straight wire. The modelling of providing a Faraday cage, and standard designs of such
of such exposure situations is simple, and Ampere’s law can suits also ensure that the electric fields are below the
legitimately be applied : B(µT) = 0.2 I / d Action Levels, even around the opening for the face.

As a consequence, the previous statement on the minimum »» Assessment : no further assessment needed
distance between the brain or the skin and the surface of a »» Action : no further action needed
conductor also applies here, but the radius of line conductors
are in the order of 1–2 cm, smaller than for insulated cables.
Considering a worker in contact with a line conductor
HOT STICK TECHNIQUES
(radius of 1.5 cm), the minimum distance to the skin is 1 cm
and to the brain is 4 cm (see section 5.2). Using Ampere’s law, Magnetic fields : Hot-stick work ensures that sufficient dis-
it follows that the Low AL (1000 µT) is reached in the brain tance is maintained from the conductors such that the mag-
with a current flow of 275 A and the LEF for sensory effects as netic-field AL is not exceeded.
proposed by the draft CENELEC standard with a current of
550 A. The High AL is reached in the skin with a current flow Electric fields : For hot-stick techniques, it is likely that the
of 750 A. From these basic calculations, simple safety rules exposure of the worker will be similar to that of workers
can be proposed, which basically consist in translating the climbing towers past live circuits, considered in section 5.3.2.
AL (or LEF) for magnetic field into AL for current : If hot-stick techniques require closer approach to the live
conductors than this, further measures may be necessary, for
»» for currents lower than 500 A, no restriction for live-line example, live-line suits.
work : the direct contact is allowed;
»» between 500 and 750 A, the contact is allowed but not The magnetic field in this exposure situation is highly likely to
for the head; exceed the public levels relevant for workers at particular
»» over 750 A, no contact is allowed (but the live-line work risk, requiring a separate assessment.
can carry on using a protective equipment around the
conductor which prevents any direct contact).

ENTSO-E – EMF report | 15

 5.5 CABLE TUNNELS OR VAULTS
Magnetic fields : Cable tunnels allow close approach to lower overall field. It is therefore recommended that cable
insulated conductors. Confined working space may mean tunnels or vaults be treated as single conductors, as in 5.2
that deliberate close approach to conductors may be above.
necessary, and accidental close approach may be difficult to »» Action : no action necessary.
control.
Electric fields : All such cables will have conducting outer
»» Assessment : Calculations are possible for straight runs of layers which ensure the electric field is close to zero.
cables in tunnels but become difficult when there are com-
plex geometries and multiple circuits. Measurements may »» Assessment : no further assessment necessary.
be preferable but need scaling to maximum load which »» Action : no further action necessary.
may not be easy where multiple circuits are involved (de-
pending on the phasing, the worst case may not simply be The magnetic field in this exposure situation may exceed the
the maximum load in every circuit). In principle, there may public levels relevant for workers at particular risk. Either such
be scenarios where the field from the multiple cables is staff should be identified and person-specific assessments per-
larger than from any single conductor. However, practical formed, or entry into such areas should be prevented for all
experience shows that in most situations, multiple cables such staff.
actually increase the degree of cancellation and lead to a

5.6 SHORT-DURATION EVENTS (FAULTS, SWITCHING TRANSIENTS ETC)

Magnetic fields : Faults on transmission systems produce high General approach to short duration events : both faults and
currents, and hence high magnetic fields (well above the High switching transients last, except in very rare circumstances,
Action Level in scenarios where a person is present in the for no more than a few cycles of a 50 Hz waveform. It is con-
worst-case location at the time of a fault, although such sce- sidered that these events are of too short a duration to fall
narios are extremely rare given how rare faults are). within the scope of the Directive. Neither the Directive, nor
the ICNIRP Guidelines on which it is based, give a minimum
Electric fields : Switching transients when re-energising duration, so it is appropriate to refer to ICES, which suggests
an overhead line circuit can produce voltages three times 200 ms or ten cycles of the 50 Hz waveform. The CENELEC
normal, and hence peak electric fields three times normal, Standard specifies that exposures of duration less than this
often made up of the 50 Hz plus a higher-frequency compo- should be considered not to constitute over-exposure.
nent. Lightning strikes can also produce similarly high voltag-
es for extremely short periods.

5.7 HVDC AND OTHER EXPOSURES TO STATIC FIELDS

The commonest source of high static fields in TSOs is HVDC Electric fields : The Directive does not contain limits for stat-
convertor stations. HVDC cables or lines also produce static ic electric fields. Elsewhere, ICNIRP give a guideline figure of
fields, but generally at lower levels. Superconducting fault 25 kV/m for static electric fields (ICNIRP, 2009). Electric fields
current limiters may be used by some TSOs. under DC busbars in HVDC convertor stations have been
measured as around 20 kV/m, and are thus below even this
Magnetic fields : Static magnetic fields in the general areas guideline figure.
of HVDC convertor stations are likely to be less than 1 mT.
The highest static magnetic fields likely to be encountered in »» Action : no action needed.
accessible areas of HVDC convertor stations is against the
surface of an insulated cable. This is analogous the AC case For workers with AIMDs, the relevant threshold for static
considered in 5.2 and, depending on the rating and diameter magnetic fields is 0.5 mT. This is the threshold to avoid
of the cable, fields of several mT are possible. operation of the reed switch included in most devices, and
is constant for all devices, unlike interference from power-
»» Assessment : Static magnetic fields will not exceed the ELVs. frequency fields, where the sensitivity varies from device to
»» Action : no action needed. device. Fields in HVDC convertor stations are highly likely to
exceed this level. This level could also be found at distances
of order 10 m from a superconducting fault current limiter.
Steps should be taken to prevent staff with these devices
entering the relevant areas.

16 | ENTSO-E – EMF report

 5.8 SUMMARY OF EXPOSURE SITUATIONS

Exposure Assessment Action required

situation
Electric field Magnetic field Staff at particular Contact currents
Staff in general
risk and microshocks
Busbars, transformers,
Compliant Compliant None yes yes
etc (at ground level)
Restrict access,
Air-cored reactors Requires further
Compliant depends on outcome yes no
(at ground level) assessment
assessment
Work above ground Screening, depends
Requires further
level in high-voltage Compliant on outcome assess- yes yes
assessment
areas ment
Work outside high-
Compliant Compliant None yes no
voltage areas
Compliant based on
Insulated conductors Compliant None yes no
existing ratings
Climbing opposite side
Compliant Compliant None yes no
to live conductors
Probably compliant
Climbing past live None, depends on
but requires assess- Compliant yes yes
conductors outcome assessment
ment
Restrictions on
Live-line work on tow-
Compliant, given that current in conductor
ers and in substations:
staff wears conduct- Requires assessment or approach to con- yes no
Hot glove or bare hand
ing suits ductor, depends on
work
outcome assessment
Probably none, but
Live-line work on tow- conducting suits may
Requires assessment
ers and in substations: Compliant be required depend- yes yes
of closest approach
Hot stick work ing on outcome of
assessment
Compliant based on
Cable tunnels or vaults Compliant None yes no
existing ratings
Short-duration events No additional require-
(faults, switching Compliant Compliant None ment beyond existing no
transients etc) provisions
HVDC and other expo-
Compliant Compliant None yes no
sures to static fields

Table 4 : Summary of exposure situations

ENTSO-E – EMF report | 17

 6 BIBLIOGRAPHY
CENELEC. (201X). ICNIRP. (2010). INTERNATIONAL COMMISSION ON NON-
IONIZING RADIATION PROTECTION Guidelines for limiting
EU. (1989). Directive 89 / 391 / EEC of 12 June 1989 on the intro- exposure to time-varying electric and magnetic fields (1 Hz to
duction of measures to encourage improvements in the safety 100 kHz). Health Physics, 99(6), 818–836.
and health of workers at work.
IEC. (2009). IEC 62110. Electric and magnetic field levels gen-
EU. (1999). Council Recommendation 1999 / 519 / EC 12 July erated by AC power systems – Measurement procedures with
1999 on the limitation of exposure of the general public to regard to public exposure. IEC 62110.
electromagnetic fields (0 Hz to 300 GHz).
IEC. (2013). IEC 61786-1. Measurement of DC magnetic, AC
EU. (2013). Directive 2013 / 35 / EU of 26 June 2013 on the mini- magnetic and AC electric fields from 1 Hz to 100 kHz with
mum health and safety requirements regarding the exposure regard to exposure of human beings. Requirements for meas-
of workers to the risks arising from physical agents (electro- uring instruments. IEC 61786-1.
magnetic fields).
IEC. (2014). IEC 61786-2. Measurement of DC magnetic, AC
ICNIRP. (2009). INTERNATIONAL COMMISSION ON NON- magnetic and AC electric fields from 1 Hz to 100 kHz with
IONIZING RADIATION PROTECTION Guidelines on limits of regard to exposure of human beings. Basic standard for meas-
exposure to static magnetic fields Health Phys, 2009, vol.96, urements. IEC 61786-2.
no. 4, p. 504–514. Health Physics, 96(4), 504–514.

ANNEX A : WORKERS AT PARTICULAR RISK

A.1 PREGNANT STAFF
Note that there is no actual scientific evidence that the mother In either case, to avoid confusion, the TSO should make clear
or the unborn baby is any more sensitive to EMFs. However, as that this provision is made for peace of mind and as a precau-
the unborn baby clearly does not fall within the definition of a tionary measure rather than for medical reasons.
worker, and as it may be speculated that the developing em-
bryo is, in general, more sensitive to a number of external in- Where a member of staff is affected by these provisions,
sults, it is considered reasonable and precautionary to limit the reasonable adjustments to her work should be made, as for
exposure of the pregnant woman to the public exposure limits. any other pregnancy-related provision. A simple, but often
unnecessarily restrictive, approach is to restrict her to non-
TSOs should choose either : operational sites, e. g. offices, avoiding operational sites, e. g.
substations. If this is considered unduly restrictive, site-
»» To require all woman, from the point at which they notify specific assessments can be made.
their employer that they are pregnant, to be subject to the
public exposure limits; or In order to avoid proliferation of warning signs and the risk of
creating unjustified alarm, TSOs are recommended not to use
»» To allow the woman to exercise a choice as to whether she warning signs or restrictions on access related to pregnancy.
wishes to be subject to the public exposure limits or not
(this alternative approach avoids any risk that restricting
the woman to the public exposure limits, which could in-
volve restrictions on their work practices, could be consid-
ered discrimination).

18 | ENTSO-E – EMF report

 A.2 WORKERS WITH ACTIVE IMPLANTABLE MEDICAL DEVICES
“Active implanted medical devices” (AIMDs) include pace- This solution may be appropriate in cases when external per-
makers, implanted cardiac defibrillators, cochlear implants, sonnel could occasionally access the site.
implanted insulin pumps, neurostimulators, etc. Any “active”
medical device (i. e. one that has a power supply, electronic If a TSO chooses to place warning signs, it is assuming the
circuitry, and / or sensing electrodes) should be assumed to be responsibility for warning of relevant sites, and therefore
included in this category. should ensure that signs are placed at every relevant location.

In the absence of any reported effects, passive devices, e. g.

IDENTIFYING STAFF
joints, plates, pins, screws, etc, can be assumed not to give
rise to any interference effects with ELF EMFs. TSOs could alternatively choose to create personnel systems
to identify all staff with AIMDs, then to perform individual
Some AIMDs can, in some circumstances, experience inter- assessments for those staff to identify any restrictions neces-
ference from EMFs at levels below the Directive exposure sary.
limits. Except under exceptional circumstances, it is only ex-
posures above the Reference Levels from the public exposure This solution applies exclusively to internal staff.
limits that can produce interference, and the public exposure
limits should be used to identify such a possibility 3). Staff should be identified through :

The nature of AIMDs and the medical conditions for which »» Pre-employment medical screening and
they are fitted means that, if interference is created, there is
a risk of an extremely serious outcome, including the theo­ »» Return-to-work interviews.
retical risk of fatality. However, experience shows that such
serious outcomes, in practice, simply do not occur. TSOs Where a member of staff has an AIMD, an assessment of their
should exercise reasonable diligence to minimise the risk of work environment should be made by relevant EMF special-
interference, but absolute prevention of interference under ists, then an assessment of the implications for their role
all possible circumstances is not possible. should be made by Occupational Health, taking appropriate
account of the member of staff ’s own attitude to the risk.
Further, all people with AIMDs need to be aware of the risks
of interference from a number of sources that could be en- Particular AIMDs as fitted to particular individuals often
countered in any workplace or outside the workplace, and have a higher immunity to interference than the worst case
will have been informed of these risks at the time of fitting assumed by Standards of the public reference levels. The im-
their device. A TSO should take appropriate steps as an em- munity of particular devices can be assessed on a case-by-
ployer to protect its staff from hazards that are specific to its case basis, thus avoiding unnecessary restrictions to working
business. However, TSOs cannot assume complete responsi- practices. It will often be helpful to seek further details of the
bility for the protection of staff with AIMDs from all possible device and its sensitivity levels from the physician concerned
interference hazards, and this should be made clear to staff. and / or the manufacturer, and staff should be expected to
TSOs can assume that staff with AIMDs will be alert to the co-operate in seeking this information.
risks.
Reasonable adjustment should be made to work practices
Staff should always be encouraged to follow all advice given in order to reduce any risks arising from interference to an
to them by their physician or the device manufacturer. acceptable level.

TSOs can choose to protect staff with AIMDs either through Some exposures to staff with AIMDs occur while working at
a system of identifying locations, or of identifying staff, or a height. A TSO may decide that staff with AIMDs and preg-
combination of the two. nant staff should not work at heights anyway, on grounds of
general safety (e. g. the requirement for a high level of fitness,
3) The Reference Levels set by Directive 1999/519/EC are 100 µT for magnetic field and the consequences if an implanted defibrillator fires while
and 5 kV/m for electric field, which are lower than the limits for workers, as set out the worker is at height). However, a TSO may decide that
above. such a blanket policy relating to all AIMDs is not appropriate
and could possibly be discriminatory.
IDENTIFYING LOCATIONS
TSOs should also ensure appropriate information or controls
TSOs could choose to place warning signs or to restrict ac- for external personnel (e. g. contractors and visitors); sites
cess for locations where interference is possible, i. e. locations where there is a possibility of exposure to EMFs high enough
where the public reference levels are exceeded. This would to cause interference with AIMDs should include a suitable
include all substations, overhead lines, cable vaults and tun- warning of the possibility of interference.
nels, etc. It would then be expected that staff with AIMDs do
not enter these locations.

ENTSO-E – EMF report | 19

 ANNEX B : “CONTACT CURRENT” METHOD
FOR ASSESSING ELECTRIC FIELD EXPOSURES
In situations where the electric field is highly non-uniform, ter will give a result representative of the real contact current
spot measurements close to metallic structures can be very which can occur when a worker is connected to a ground
sensitive to the peak effect and can therefore significantly structure ( for example a worker with conductive shoes in a
overestimate to actual exposure of workers. A possible way to tower).
solve this issue is to consider that when exposed to an elec-
tric field a worker can be considered as a voltage generator The direct measurement of the contact current is easy to per-
(see figure). form considering that the contact impedance is not critical :

When a worker exposed to an electric fields has a permanent The usual coupling factor given in reference publications
contact to the ground, the contact current is the short-circuit (e. g. CIGRE) is 15 µA per kV/m, corresponding to the maxi-
current of the voltage generator. It depends on the magnitude mum (conservative) coupling situation, i. e. a man standing
of the electric field and on the position of the body in the field in a vertical electric field. Therefore the High AL for electric
and with regard to the ground plane. At ground level, the ca- field is equivalent to a 0.3 mA contact current and the LEF
pacitance C0 of a standing man is in the order of 150 – 200 pF (as proposed by CENELEC) is equivalent to 0.5 mA.
and, therefore the contact current I c remains independent
from the contact impedance Z c as far as it remains lower than Reciprocally, any contact current from a worker to a ground-
(2 π.f.C0 ) -1 = 10 MΩ. ed structure lower than 0.5 mA means that the corresponding
exposure to the electric field (whatever uniform or not) is
This condition is easy to comply with, and it also means that complaint.
a direct measuring the contact current using a usual amme-

Zc contact impedance

Ic contact current A
Uo
Ic Ic
Leakage
to ground Co

20 | ENTSO-E – EMF report

 ANNEX C : ASSESSMENT METHODS FOR
ELECTRIC FIELD EXPOSURES ON TOWERS
WITH LIVE CIRCUITS
Section 5.3.2 explained that when climbing on towers past measured on 400 kV towers. However, the field is aligned,
live conductors, electric fields can be high, and can certainly broadly speaking, horizontally through a linesman’s vertical
be above the High Action level and Limit Equivalent Field. body (see figure), an orientation where the coupling is less
Measurements in the vicinity of tower steelwork (which cause strong then the reference one (person standing at ground
strong local perturbations) and possibly perturbed by the level and exposed to a vertical field). So the field measure-
person making the measurement (who cannot be distanced ments in excess of the Action levels does not necessarily
from the measurement point as easily as at ground level) are indicate exceeding of the exposure limits values.
unreliable, but fields of 30 kV/m or even higher have been

Alternative assessment methods are available.

»» A simple approach is to scale the Action level or the Limit sults in a contact current 38 % smaller than from a 10 kV/m
equivalent field by the ratio of the height of a person to vertical field at ground level. In other words an exposure to
their thickness, a factor of perhaps 4. This factor very ap- a 20 kV/m vertical field at ground level is equivalent to a
proximately represents the ratio of the coupling in the two 32 kV/m horizontal exposure in a tower. This approach
geometries. The High Action level would thus become per- therefore allows to exceed the HAL, but requires to analyse
haps 80 kV/m, and the exposure is likely to be deemed the coupling of the field to the body for the work positions
compliant. in towers.

»» A second approach is outlined in the CENELEC Standard »» A third approach would be to perform numerical dosimet-
and based on measurements by EPRI is to use the total ric calculations specific to the exposure scenario. However,
contact current as a proxy for the effect of the electric field, no such calculations have yet been published.
as explained I annex B. This total contact current has been
measured both for the reference case of a person standing It is likely that, using one of the above alternative methods,
vertically in a vertical field, and for a worker leaning out 30° this activity will be demonstrated to be compliant, and there-
from a tower leg in a horizontal field (see figure above), and fore no further action is needed.
can therefore be used to scale from one to the other. EPRI’s
finding is that a horizontal field of 10 kV/m in a tower re-

ENTSO-E – EMF report | 21

 ABBREVIATIONS
AIMD Active Implanted Medical Device

AL Action Level

CNS Central Nervous System

EC European Commission

ELV Exposure Limit Value

EMF Electromagnetic Fields

ENTSO-E European Association of Transmission System Operators for Electricity

HAL High Action Level

HVDC High Voltage Direct Current

LAL Low Action Level

LEF Exposure-Limit-Equivalent-Field

PNS Peripheral Nervous System

TSO Transmission System Operator

UNITS
A Ampere, unit of electrical current; it measures the amount of electrical charge that flows in an
electrical circuit per 1 second. 1 A = 1,000 mA (milliampere); 1 mA = 1,000 µA (microampere);
1 kA (kiloampere) = 1,000 A

F Farad, unit of electrical capacitance, the ability of a body to store an electrical charge;
1 pF (picofarad) = one trillionth (10 -12) F

Hz Hertz, unit of alternating current (AC) or electromagnetic (EM) wave frequency;

1 Hz = one cycle per second. 1 Mhz (megahertz) = 1,000,000 Hz; 1,000 Mhz = 1 GHz (gigahertz)

Ω Ohm, unit of electrical resistance; 1 MΩ (megohm) = 1,000,000 Ω

T Tesla, unit of electric field strength; 1 T = 1,000 mT (millitesla) or 1,000,000 µT;

1 µT (microtesla) = 1,000 nT (nanotesla)

V Volt, unit of electric potential; 1 kV (kilovolt) = 1,000 V

V/m Volt per meter, unit of electric field strength; an electric field of 1 V/m is represented by a ­potential
difference of 1 V existing between two points that are 1 m apart.

22 | ENTSO-E – EMF report

 AUTHORS

FRANCOIS DESCHAMPS CHRISTOPH DÖRNEMANN VINCENT DU FOUR EDWARD FRIMAN

RTE, France Amprion, Germany ELIA, Belgium Svenska kraftnät, Sweden

ARIANNA GUARNERI MIKA PENTTILÄ KLEMENS REICH JOHN SWANSON

Terna, Italy Fingrid, Finland APG, Austria National Grid, UK

ENTSO-E – EMF report | 23

 CONTACT

ENTSO-E aisbl · Avenue de Cortenbergh 100 · 1000 Brussels – Belgium

Tel + 32 2 741 09 50 · Fax + 32 2 741 09 51
info @ entsoe.eu · www.entsoe.eu

© ENTSO-E 2016