States Assembly | Limitation of short-term exposure

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Ordinance

Limitation of 100 kV/m short-term exposure

10 kV/m

The Ordinance specifies exposure limit val-

ues aimed at limiting short-term expo-

sure. These limits are based on the recom- 1 kV/m mendations of the International Commis-

sion on Non-Ionising Radiation Protection (ICNIRP) that are used in many other coun- 100 V/m tries. If these limits are complied with,

none of the scientifically accepted nega-

tive effects on our health can occur. These

include an increase in body temperature 10 V/m due to very high intensity radiation from

transmitters, and triggering of undesira -

ble nerve impulses or muscle contractions 1 V/m by intensive electric or magnetic fields.

The exposure limit values must be com-

Frequency 1 Hz 1 kHz 1 MHz 1 GHz 1 THz

plied with wherever people spend any

length of time.

The exposure limit values for the electric field strength (green curve) specified in the ONIR vary according to the frequency of the radiation, since the effects on human beings occur at different intensities depending on frequency.

100 mT 10 mT

1 mT 100 T 10 T 1 T 100 nT 10 nT

Frequency 1 Hz 1 kHz 1 MHz 1 GHz 1 THz

For the same reason, the exposure limit values for the magnetic flux density (red curve) are also frequency-dependent.

Exposure limit values

System Frequency Exposure limit value

– The exposure limit values specified by the

Ordinance are internationally co-ordinated. Railway catenaries 16.7 Hz 300 T and 10,000 V/m

– They protect against scientifically accepted High-voltage power lines 50 Hz 100 T and 5,000 V/m damage to health. Radio/TV transmitters 10 - 400 MHz 28 V/m

– They take account of the overall Mobile phone 900 MHz 41 V/m

low-frequency or high-frequency radiation base stations 1,800 MHz 58 V/m

at a given location. UMTS transmitters 2,100 MHz 61 V/m

– They must be complied with wherever

people spend any length of time (including Examples of exposure limit values for various frequencies.

very short periods).

Precautionary limitation of long-term exposure

Exposure limit values ensure protection tal Protection Law also states that meas-

against recognised, acute effects, but ures must be taken at the source to limit

they do not protect against suspected environmental pollution. Here the criteria

effects at lower radiation intensities, es- are technical and operational feasibility,

pecially with long-term exposure. A great as well as economic acceptability.

deal of research is still required in this The ONIR implements these principles by

area. When the Federal Council drew up specifying thresholds for various catego-

the ONIR, it did not want to wait for fur- ries of radiation sources. These so-called

ther research findings, and for this rea- installation limit values apply to radiation

son it included precautionary measures from a single installation and are well be-

to limit the long-term exposure. low the exposure limit values. For mobile

The provisions concerned are based on the phone base stations they are around 10

principle of precaution as established in times lower, and in the case of new high-

the Federal Law relating to the Protec- voltage power lines they are as much as Places of sensitive use

tion of the Environment. Article 1, para- 100 times lower. Installation limit values

graph 2 of this law states: "Early preven- must be complied with wherever people Precautionary protection provided by tive measures shall be taken in order to spend lengthy periods of time (at plac- the installation limit values is limited to limit effects which could become harmful es of sensitive use). These provisions are locations where people regularly spend or a nuisance". In other words, suspicion among the most stringent regulations of lengthy periods of time. Here, long-term of harmful effects is sufficient, and it is their kind in the world. exposure shall be kept as low as possi- therefore not necessary to provide scien- However, in view of the unclear situation ble. Places of sensitive use include apart- tific proof. In Article 11, the Environmen- with respect to risks to health, even these ments, schools, hospitals, offices and play-

stringent regulations do not provide 100- grounds, but do not include balconies and

percent safety. It is not possible for au- roof terraces, stairways, garages, storage Installation limit values thorities and medical experts to provide and archive rooms, temporary workpla-

a guarantee of safety, either now or in the ces, churches, concert halls and theatres,

– The installation limit values specified future. However, this holds not only for the camp sites, sports and leisure-time facil- by the ONIR are of a precautionary radiation issue, but also for many other ities, passenger areas in railways, obser- nature. new technologies. It is not possible to ex- vation decks.

– They are much lower than the clude all potential health risks on a sci-

exposure limit values. entific basis, since life processes are too

– They are based on the principle of complex to allow every conceivable biolog-

precaution established in the Federal Law ical effect to be studied in advance. But

relating to the Protection of the since the installation limit values reduce

Environment, and have been specified in long-term exposure, the risk of any conse-

accordance with technical, operational quences to our health that are not clearly

and economic criteria. recognisable today is also minimised.

– They limit the level of radiation from a

given installation.

– They must be complied with wherever

people spend lengthy periods of time. System Frequency Installation limit value

– They ensure that exposure to electrosmog

is low at places of sensitive use, and in Railway catenaries 16.7 Hz 1 T (24-hr average)

this way they also reduce the risk of High-voltage power lines 50 Hz 1 T

suspected harmful effects on health. Radio/TV transmitters 10-860 MHz 3 V/m

Mobile phone 900 MHz 4 V/m

Installation limit values are based on tech- base stations 1,800 MHz 6 V/m

nical, operational and economic criteria, and UMTS base stations 2,100 MHz 6 V/m

not on medical or biological findings. This

means they are not levels indicating harm-

lessness, and compliance with them cannot Examples of installation limit values. These have to be complied with in the reference guarantee that all harmful effects can be operating mode. Please refer to the descriptions of the various installation categories excluded. However, this also does not mean for more detailed information.

that negative effects occur if installation

limit values are exceeded.

Ordinance

Controls by means of calculations and measurements

The competent federal, cantonal or mu- nicipal authorities verify whether the lim- it values specified by the Ordinance are complied with. For this purpose they may carry out calculations or measurements. For example, operators of mobile phone base stations are required to submit a site data sheet together with their application for a building permit. The radiation in the vicinity of the installation is calculated on the basis of the transmission capacity and directions. The cantonal or municipal authorities check the accuracy of these data and calculations. Similar calculations are also carried out on other installations such as high-voltage power lines and rail- way catenaries.

The radiation can be measured after the system has been put into operation. Here a distinction is made between approval and control measurements.

In order to protect the population, the designation of new building zones will only be permitted

in close proximity to existing or planned supply installations emitting non-ionising radiation Approval measurements

if the installations concerned are able to comply with the installation limit values specified in

the ONIR. Approval measurements are carried out in

order to ascertain that the respective in - New building zones stallation limit value is complied with in a

given operating mode – in the case of mo- In addition to measures at source, the For example, mobile phone base stations bile phone base stations, for example, at ONIR also sets out to ensure the lowest must be improved in such a manner as to full utilisation capacity and maximum ap- possible long-term exposure by means of ensure that the installation limit value is proved transmission power. These meas- land use planning. It restricts the develop- fully complied with at all places of sensi- urements are normally carried out if cal- ment zoning of new areas if they are in the tive use, but no such requirements apply culations indicate that radiation levels are close vicinity of existing or planned facil- to power lines and railway catenaries. In likely to exceed 80 percent of the speci- ities that produce non-ionising radiation. the case of electricity transmission, the fied installation limit value. It is often the In this way it ensures that no heavily ex- Ordinance merely calls for optimisation case that the proprietor of the facility posed places of sensitive use will be cre- of the phasing arrangement, and in the entrusts a specialised company with the ated in the future. Since 1 February 2000, case of catenaries a return conductor is task of carrying out these measurements, the definition of new building zones is only required. Even though these measures do since such companies possess the neces- permitted if the installation limit values not suffice to bring the level of radiation sary know-how and experience. The asso- can be complied with. below the installation limit value in devel- ciated costs have to be borne by the pro- The situation is different, however, in oped areas, the Ordinance does not call prietor in accordance with the principle building zones that were approved before for any other improvements. The Federal of "polluter pays".

the above date and are located near a ra - Council was of the opinion that a reduc- Approval measurements can never be car- diation source. Here, development is per- tion of radiation levels to below the instal- ried out fully independently of the propri- mitted without any restrictions, even if an lation limit value would be disproportion- etor, since the latter is required to pro - installation limit value is exceeded. How- ate for existing power lines and catenar- vide the necessary data concerning the ever the installation concerned has to be ies. For the same reason it also rejected current operating mode during the meas - improved, and the ONIR specifies the re- the idea of reversing zoning in areas that urement procedure. In the case of mobile quired degree of improvement for each are already zoned. phone base stations, the Ordinance stipu- type of installation. lates that the installation limit value must

be complied with at full operating capaci- ty and maximum transmission power. This status seldom applies in practice, however,

since the base station normally operates at lower output levels. For this reason, the results have to be projected from the cur - rent to the maximum approved transmis- sion power. It is only in this way that the authorities are able to judge whether the installation limit value has been complied with. These projections are based on data provided by the operator concerning the current operating mode.

Control measurements

Control measurements are carried out for a quite different purpose, namely to de- termine the radiation level when the in- stallation concerned is in its actual state of operation. Control measurements are carried out independently of the oper - ator. This hand-held test antenna (above) can be used for detecting the maximum exposure level

indoors. A spectrum analyser (below) depicts the results of the frequency selective measure-

ment. Since each frequency is recorded separately, it is possible to specifically measure the Measurement of radiation level of radiation from a single mobile phone base station.

from mobile phone base stations

There are various methods for measuring radiation from mobile phone base stations:

Broadband measurement: With this method, a sensor is used which records the overall radiation in a broad frequency range. Along- side mobile phone base stations, other systems such as radio and TV transmitters also contribute towards these readings, but it is not possible to distinguish between the individual sources.

Frequency selective measurement: This method is used if, on the basis of a broadband measurement, it is not possible to judge with sufficient certainty whether a mobile phone base station complies with the installation limit value. Here it is only the radiation from the installation concerned that is measured. Selective frequency measurements are more demanding and time-consuming than broad- band measurements, and require more com- plex measuring equipment.

Code selective measurement: This method is used for measuring UTMS radiation if the other two methods fail to yield conclusive results. Here, only the temporally constant proportion from the UMTS signal is recorded, and subsequently projected. In this way it is possible to clearly allocate the recorded signals to a specific transmitter.

Power supply

Wherever electricity is generated, transmitted and consumed, electric and magnetic fields are created as by-products. The higher the current and voltage, and the shorter the distance

from the current-bearing installations, the higher the intensity

of these fields becomes. In the area of power supply, the highest levels of exposure occur in the immediate vicinity of transformer stations and high-voltage power lines.

Wherever there is an electric current, there are also low-frequency fields

Contents

From power plant to mains socket > P From power plant to mains socket

The three parameters of electricity > P In Switzerland, a large proportion of For shorter distances (e.g. region to re-

electricity is produced from hydropow- gion), the voltage is reduced to between How fields are created > P er plants that are often located well away 50 and 150 kV and the energy is usually

from places where it is subsequently con- transported via overhead lines support- Three-phase alternating current > P sumed. This means that much of the en- ed by concrete masts.

ergy we consume has already travelled a And at the local level, the voltage is re- Magnetic fields from overhead considerable distance. Generators in the duced to between 6 and 30 kV and the en- power lines > P various types of power plants generate ergy is transported either by underground

electricity with a frequency of 50 Hz and cables or via overhead lines supported by Reduction of the magnetic field a voltage of 6 to 27 kilovolts (kV). wooden poles.

by phase optimisation > P High voltages reduce transmission loss- In residential areas, villages, etc., trans-

es, and in view of this, the voltage is in- former stations finally reduce the voltage Temporal variation of the magnetic field creased in the respective power plant by to the levels normally used in households near a high-voltage transmission line > P means of transformers before the elec - (i.e. 230 and 400 volts).

tricity is fed into the transmission grid.

Electric fields from overhead As a rule, levels of 220 or 380 kV are used

power lines > P for long-distance transport. This overland

network mainly comprises overhead lines

More localised magnetic fields supported by pylons.

from underground cables > P

Precautionary regulations of the ONIR > P

Regional

Magnetic field from a National Interregional dis- distribution Local distribution

transmission grid, tribution networks, networks, networks, transformer station > P 7 380 or 220 kV 50 to 150 kV 6 to 30 kV 230 V / 400 V

Consumers

Cable distribution cabinet

Pole mounted transformer Transformer station

Power plant Sub-station Sub-station

On its way from power plant to end user, electricity first has to be converted to higher voltages, then brought back down to lower voltages. Electric and magnetic fields are produced both along power lines and in the vicinity of transformer stations.

Power supply

The three parameters of electricity How fields are created Some of the properties of electric and magnetic fields are similar: for example,

There are three physical parameters Everyday we use electrical appliances in both cases they weaken rapidly with in- which characterise electricity: and devices at home, at work and in our creasing distance from the source. How-

leisure time. And wherever electricity is ever, they differ greatly when it comes to Current: This is measured in amperes (A) used, electric and magnetic fields are cre- screening: electric fields can be screened and indicates how much electricity is flowing ated – for example in close proximity to fairly easily, whereas magnetic fields free- through a conductor. If we use water supply high-voltage power lines, sub-stations and ly penetrate practically all materials, and as an analogy, the current would correspond transformer stations. But these fields are screening is therefore only possible with to the throughput of water per time unit. also created by electrical appliances in the aid of special metal alloys or thick alu- The greater the throughput, the higher the households, offices, factories, etc. minium sheets, and even then only to a current. In households, fuses in distribution Electric fields occur as soon as an appli- limited extent.

boxes or panels limit the current to 0 or ance is connected to the power supply via

A. The largest high-voltage power lines are a cable and plug. As soon as it is switched

designed for currents of up to ,00 A. on, current begins to flow, and this gives

rise to a magnetic field in addition to the

Voltage: This is measured in volts (V). To stay already existing electric field. Since our

with the water supply analogy, this is equiva- power supply is operated with alternat-

lent to water pressure, which is still present ing current with a frequency of 50 Hz, the

even if the tap is turned off and no water is electric and magnetic fields are also 50 Hz

flowing. In the same way, a plugged-in alternating fields.

power cable, e.g. for a bedside table lamp, is

"live", even if the light is switched off and

no electricity is flowing. General purpose Three-phase alternating current

batteries range from . to V. The mains

supply in households is 0 V, while high-volt- The 0 Hz electricity network is operated second circuit nearby, all six combinations age power lines can be up to 0,000 V. with three-phase alternating current. Here, generate an equally strong magnetic field.

three phase conductors form one line circuit. But as soon as two line circuits are brought Frequency: This refers to the number of The alternating currents in each conductor close together, the magnetic fields of the oscillations per second, and it is measured are phase shifted by one-third of an oscilla- individual circuits can be mutually strength- in hertz (Hz) ( Hz = oscillation per second). tion period – they have differing phase an- ened or weakened. This depends on how the Frequency is only of importance for alternat- gles. There are six different possible combi- order of the phases of the second line circuit ing current. With batteries, the positive and nations for connecting the three phases has been arranged in relation to the first one. negative poles are fixed. They supply direct (R, S and T) to the three phase conductors

current that always flows in the same direc- of a line circuit. As long as there is not a

tion. By contrast, alternating current chang-

es its flow direction: electricity in households

has a frequency of 0 Hz. And this frequency

is always the same, from the power plant

to the mains socket, whereas voltage and R S T

current change according to network level.

0 5 10 15 20

Time (milliseconds)

With the three-phase alternating current system, the currents in the three conductors are each phase shifted by one-third of an oscillation period. The three phases are designated R, S and T.

Magnetic fields from overhead lines

The intensity of a magnetic field is indi- cated in microtesla (µT). With high-voltage

power lines, the higher the current, and the greater the distances between the power-bearing conductors, the greater the spatial bearing of the magnetic field. The most intensive exposure occurs at mid-span between two pylons, where the conductors are closest to the ground. The level varies, however, according to the de- sign of the power line and the current. The magnetic field weakens with increasing distance from the power line. This means that the higher the conductors are above the ground, the weaker the field. In the View (in perspective) of the magnetic field of a typical 380-kV high-voltage transmission line case of transmission lines with several line with two line circuits at full load (1,920 A). The highest exposure occurs around the six current- circuits, or power lines running parallel bearing conductors: within the red tubes the level is more than 100 microtesla (T), and at the to one another, the magnetic fields of the perimeter of the large tunnel it has fallen to 1 T.

individual circuits can be mutually weak-

ened or strengthened. Therefore it is pos- 100

sible to reduce the intensity of the mag-

netic field by optimising the order of the

phases. 80

The walls of buildings cannot screen mag-

netic fields effectively. 380 kV overhead

power lines can increase exposure to mag- 60

netic fields in neighbouring houses locat-

ed up to a distance of 150 to 200 metres.

Further away, exposure approaches the 40

normal background level of approximately 0.02 to 0.04 µT which is usually encoun- tered in residential dwellings connected

to the electricity mains. However, the in- 20

tensity can be much higher in the close vi-

cinity of electrical appliances.

m 80 60 40 20 0 20 40 60 80

Cross-section of the magnetic field of the high-voltage transmission line depicted above, at mid-span between two pylons where the conductors are closest to the ground. The exposure diminishes with increasing distance from the power line, and is not influenced by walls, trees or the ground. The significance of the concentric lines is indicated in the colour scale below.

0.1 1 10 100 1000 10 000

Installation limit value Exposure limit value

Scale of magnetic flux density in microtesla (T).

Power supply

Reduction of the magnetic 100 field by phase optimisation

By contrast with electric fields, it is very 80 difficult to screen magnetic fields. Careful arrangement of the conductors and opti - misation of the order of the phases are 60 the best options for limiting their reach.

The alternating currents in each conduc-

tor are shifted in time with respect to 40 each other – they are said to have differ-

ent phase angles. Depending on the way in which the three phases are connected to

the conductors at the ends of the trans- 20 mission line, the magnetic field will be of

smaller or larger spatial extension. Opti- misation of the order of the phases means 0 connecting the conductors in such a man-

ner that the spatial extension of the mag - netic field is minimised. For this purpose, 20 simulation programs are used that calcu-

late the most suitable order of the phas- m es based on the given conductor arrange- ment and predominant power flow direc- tions.

80 60 40 20 0 20 40 60 80

With a favourable arrangement of the conductors and by optimising the order of the phases, it is possible to significantly reduce the spatial extension of the magnetic field. The illustration above depicts the magnetic field of a double-circuit 380-kV high-voltage transmission line with optimised phase order. The illustration below shows the same system with unfavourable phase order. The significance of the concentric lines is indicated in the colour scale.

100 80 60 40 20

m 120 100 80 60 40 20 0 20 40 60 80

0.1 1 10 100 1000 10 000Scale of magnetic flux density

in microtesla (T). Installation limit value Exposure limit value

Temporal variation of the magnetic field 0.5 T

near a high-voltage transmission line

0.4 T

The magnetic field depends on the current,

and thus on the corresponding electric- 0.3 T

ity consumption in households, industry,

etc. The time profile of magnetic field ex- 0.2 T

posure in the vicinity of high-voltage pow-

er lines thus reflects the fluctuating elec-

tricity consumption, depending on time of 0.1 T

day and season.

Unlike current, the voltage remains prac- 0.0 T

tically constant, and this also applies to

the electric field of high-voltage power

0 h 2 h 4 h 6 h 8 h 10 h 12 h 14 h 16 h 18 h 20 h 22 h 24 h

lines, which stays proportional to the volt-

age. Example of a 24-hour profile of the magnetic field near a 220 kV high-voltage transmission

line on a weekday in January. The magnetic field fluctuates depending on the currents flowing through the two line circuits

Electric fields from overhead 100

power lines

The strength of electric fields is meas- 80

ured in volts per metre (V/m). It largely depends on the voltage and the distance from the conductor. Directly beneath a 60

380-kV high-voltage power line, the elec-

tric field strength close to the ground can reach 5,000 V/m. The lower the voltage,

the less intense the electric field. For ex- 40

ample, beneath a 220-kV line the strength

is up to 3,000 V/m, for 110-kV lines it is a maximum of 700 V/m and for lines below 20

50-kV it is up to 400 V/m. As the diagram shows, the field strength weakens with in- creasing distance from the conductors. 0

Electric fields can be distorted and weak- ened by low-conductive materials such as trees, bushes and buildings. The conduc- m 80 60 40 20 0 20 40 60 80 tivity of building materials usually suffices

to reduce an external electric field by 90 Cross-section of the electric field of a 380 kV high-voltage transmission line with two circuits, percent or more inside the building. at mid-span between two pylons where the conductors are closest to the ground (minimum

permissible distance from the ground). Directly below the power line, the exposure limit value of 5,000 volts per metre is almost reached. Buildings, trees and the ground distort electric

fields and attenuate them. This means that exposure inside buildings from overhead power lines can be more or less ignored. The significance of the concentric lines is indicated in the colour scale below.

5 50 500 5000 50 000 500 000

Exposure limit value

Scale of electric field strength in volts per metre (V/m).

Power supply

More localised magnetic fields just as high directly above an underground

from underground cables cable system as it is immediately beneath Precautionary regulations of the ONIR

an overhead power line, it decreases more

Whereas long-distance electricity trans- quickly on departing laterally than is the The precautionary emission limitations mission is primarily effected via overhead case with overhead lines. for high-voltage transmission lines spec- power lines, most local distribution is now Unlike the magnetic field, the electric field ified in the ONIR vary according to wheth- carried out using underground cables. is completely shielded by the cable sheath er the installation is new, to be modified With overhead lines, the air between the and the soil. This means that no electric or old.

conductors acts as an insulator. The con- field is detectable even if we are standing New installations: At places of sensitive ductors have to be a certain distance directly above the underground cables. use such as residential dwellings, the in- apart in order to prevent arcing. But with Today it would be technically feasible to stallation limit value for new high voltage underground cables, the conductors are also lay high-voltage power lines (over power lines or upon replacement of exist- very well insulated and can therefore 50 kV) underground, but the associated ing ones is 1 microtesla (µT). This limit ap- be placed closer together, as a result of costs would be much higher, and repair plies to operation of the power line at full which the reach of the magnetic fields is work would be more costly and time-con- capacity. Since current varies according reduced. suming. In view of this, electricity sup- to time of day and season, and only rare- This means that, compared with overhead ply companies prefer to use overhead ly reaches full load, the average magnetic power lines carrying the same current, systems. field exposure when the installation lim- the magnetic field of an underground ca- it value is complied with is well below 1 µT. ble system has a much smaller spatial ex- In certain exceptional circumstances, the tension. Although the exposure may be relevant authorities may allow this limit

value to be exceeded.

Installations to be modified: The term View (in perspective) "modified" refers to all changes concern- of an underground ing conductor arrangement, phase order cable line with three or operating status of an existing high- conductors in voltage power line. At places of sensitive separated plastic use at which the installation limit value tubes embedded in of 1 µT was already exceeded prior to the concrete. implemented changes, the magnetic field

intensity may not be increased. At all oth-

er places of sensitive use, the installa-

tion limit value must be complied with. As

with new installations, exceptions may be

granted under certain circumstances.

6 4 2

– 2

– 4

m 9 6 3 0 3 6 9

Cross-section of the magnetic field of an underground cable line. Here the conduit is 0.8 metres

below the surface. Since the current-bearing conductors (745 A each) are close together, the spatial extension of the magnetic field is significantly smaller than is the case with overhead 220 kV overhead transmission line near Laax transmission lines, and the exposure also diminishes more quickly with increasing distance. (canton of Grisons).

Old installations: If old power lines exceed Magnetic field from a

the installation limit value at places of transformer station

sensitive use, the phasing has to be op-

timised. Beyond this the Ordinance does Transformers increase or decrease volt- not specify any additional requirements. ages. They are used in power plants, sub- If the power line concerned does not com- stations, residential areas and industrial ply with the installation limit value even zones. Transformer stations in residential after optimisation of phasing, this is tol- areas are fed via the regional electrici- erated. ty distribution network. They change the

supply voltage (which ranges from 6,000 Type of power line Distance for compli- up to 30,000 V) to the levels required for

ance with installation use in households (230 and 400 V). A ba- limit value of 1 T sic transformer station comprises a high- voltage component, a transformer and a

380 kV overhead lines 60 to 80 metres low-voltage distributor. Both the low- 220 kV overhead lines 40 to 55 metres voltage distributor itself and its con - 110 kV overhead lines 20 to 30 metres nection to the transformer generate the 50 kV overhead lines 15 to 25 metres strongest magnetic fields. This is partly 110 kV underground 3 to 6 metres because the current is much higher here cables than it is on the high-voltage side, but also

because the spatial separation between The cited direct distances from the con- the individual conductors in the low-volt- ductors apply when phasing is optimised. age distributor increases the magnetic The higher the conductors are suspend- fields still further.

ed, the shorter the minimum lateral dis- Since there are numerous types of trans- In addition to high-voltage power lines, tance for compliance with the installa- former stations, it is very difficult to make sub-stations, too, produce relatively intensive tion limit value. generally applicable indications of the magnetic fields within their fenced-in area.

magnetic fields they cause.

Low-voltage distribution

Transformer High-voltage component

The transmission grid in Switzerland (blue = 380 kV, green = 220 kV).

230/400 V 303 A

Depiction (in perspective) of the magnetic

field of a walk-in transformer station at full

load (630 kVA). In the dark-red sections, the

magnetic field exceeds 100 T, and at the

perimeter of the lighter zone it is 1 T. This 230/400 V 303 A 20 kV 108 A is a well-designed transformer station with

optimised components. The magnetic field of 20 kV 90 A

transformer stations that are not so well

designed can have a much wider extension.

Electrical appliances in the home

In most homes, field exposure is not dominated by external sources, it is mostly caused by electrical appliances we use indoors. Here we ourselves are able to exercise precaution and reduce our level of exposure by taking basic measures. For ex- ample, we should avoid placing permanently operated electrical appliances in locations where people spend lengthy periods

of time.

Electrical appliances in the home are usually the main source of exposure

Contents

Sources of electrosmog in households > P Sources of electrosmog in households

Increased exposure near In our own home we can also be exposed to

electrical appliances > P electrosmog from external sources such

as nearby high-voltage power lines, rail- Appliances in permanent use > P way catenaries, mobile phone base sta-

tions, etc., but in most cases a large pro- Precautionary reduction portion is in fact home-made. Electrosmog of electrosmog > P 0 in households is made up of the following

emissions:

Regulations governing new – Low-frequency electric and magnetic domestic installations > P 0 fields from domestic installations, i.e.

fixed distribution and fuse boxes/pan- No limit values for electrical els, electricity cables, mains sockets, as

appliances > P 0 well as extension cables dryer, the magnetic field falls to between

– Low-frequency fields from lighting and 0.01 and 7 µT at a distance of 30 centi-

Microwave ovens > P 0 electrical appliances metres, and to between 0.01 and 0.3 µT

– High-frequency electromagnetic radi- at a distance of 1 metre. A similar situa-

Electrical appliances in ation produced by cordless phones or tion applies to electric cooker tops: in the the household > P wireless networks for computers (see immediate vicinity, their magnetic field is page 52). between 1 and 50 µT, but this weakens to

Kitchen appliances > P 0.15 to 8 µT at a distance of 30 centime- Increased exposure tres, and falls to between 0.01 and 0.04 µT

Reducing electrosmog in bedrooms > P near electrical appliances at a distance of 1 metre.

Screens > P In houses connected to the electrici - Appliances in permanent use

ty mains, the typical background level of

Lighting > P the magnetic field from the power supply As a rule, our exposure to magnetic fields

is between 0.02 and 0.04 microtesla (µT). from appliances like those cited above is This applies to the vast majority of build- only short term because they are not in ings that are located outside the area of permanent use. However, the situation direct exposure to sources such as high- is different when it comes to applian- voltage transmission lines, railway cate- ces that are in use all the time, e.g. clock naries and transformer stations. radios. If such devices are used in places These exposures are normally superim- where people spend several hours a day posed by magnetic fields from electrical (e.g. bedrooms, living rooms), this can lead appliances inside the building. Exposure to long-term exposure. It is possible to can be significantly higher in the imme- significantly reduce the level of exposure diate vicinity of appliances that produce by maintaining an adequate distance from strong magnetic fields: appliances that are permanently in use. In

– High consumption appliances that gen- the case of a clock radio, for example, at erate heat, e.g. cookers, boilers, hairdry- a distance of around 1 metre the magnet- ers, clothes irons ic field is no greater than the background

– Appliances with magnetic coils or trans- level in the building. Since magnetic fields formers, e.g. TV sets, low-voltage halo- are able to penetrate even solidly con- gen lamps, clock radios structed walls at virtually full strength, it

– Appliances equipped with an electric is important to also pay attention to the motor, e.g. drills, food mixers, vacuum situation in neighbouring rooms when de- cleaners. ciding where to place permanently oper- ated appliances.

In the case of hairdryers, for example, mag-

netic fields of more than 100 µT can occur

directly on the casing surface, but their

level diminishes quickly with increasing

distance. Depending on the type of hair-

Electrical appliances in the home

Precautionary reduction of electrosmog trical installations and appliances that No limit values for electrical appliances

are in use for lengthy periods of time

There are several simple precautionary (e.g. electric floor heating systems) can In Switzerland, there are no legally binding measures we can take to reduce the lev- cause high levels of exposure. This ap- limit values concerning non-ionising radi- el of exposure to non-ionising radiation plies especially if appliances are used ation from electrical appliances. Technical at home: close to the body, as is the case with measures to reduce electric and magnet-

– Switching off and unplugging appli- electric blankets and electric water ic fields are certainly desirable, but in or- ances. Appliances continue to consume beds. Here, too, switching off such appli- der to avoid trade barriers, these need to electricity even in standby mode, and ances and unplugging them during the be defined at an international level. Cor- they therefore produce a magnetic night reduces the level of exposure. responding standards currently exist for field. If we switch them off when we no computer monitors (e.g. TCO label). longer need them, the magnetic field Regulations governing The intensity of fields produced by electri- also disappears. And if we even unplug new domestic installations cal appliances must not be compared with such devices when we do not need to the limit values specified by the ONIR for use them for longer periods, we can also The ONIR does not specify any installa- installations such as high-voltage trans- eliminate the electric field. tion limit value as a precautionary emis- mission lines or transformer stations.

– Maintaining adequate distance from sion limitation for domestic electrical in- Electrical appliances produce localised, electrical appliances. Since field inten- stallations, but it does contain technical non-homogeneous fields, whereas the lim- sity diminishes with increasing distance requirements concerning the arrange - it values specified by the Ordinance apply from the source, we should maintain an ment of cables and distribution systems to more extensive fields.

adequate distance between electrical in order to reduce field intensities. All

appliances and our preferred spots of new installations have to correspond to Microwave ovens

stay. The recommended minimum dis- the recognised status of technology. This

tance from clock radios is 1 metre, and includes star-shaped arrangements of To cook foodstuffs, microwave ovens use from TV sets it is 2 metres. And since power feeds (wherever possible), avoid- the heat produced by high-frequency ra- magnetic fields are able to pass through ance of loops in power feeds, and installa- diation with a frequency of 2.45 gigahertz walls without obstruction, these dis- tion of main distribution systems at a suf- (GHz). Thanks to screening and other pro- tances also apply to appliances in neigh- ficient distance from bedrooms. tective measures, almost no radiation es- bouring rooms. capes from microwave ovens.

– Avoiding the long term use of electri- It is not possible to screen out radiation cal appliances close to the body. Elec- altogether, but as long as the microwave oven is intact, the amount of radiation that is able to escape through the door and seals is so low that it does not repre- sent a health hazard. However, if the door seal should be heavily soiled or damaged, higher levels of radiation may escape un- der certain circumstances. The following measures can be taken to reduce radia- tion from microwave ovens:

– The door seal and casing should be checked periodically to make sure they have not been damaged. Microwave ov- ens that have been damaged or have been in use for several years should be checked by specialists, and replaced if necessary.

– Keep the eyes sufficiently away from the door while the microwave oven is in op- eration.

– A distance of at least 1 metre should be maintained from a microwave oven if it is used for a lengthy period of time.

The ONIR applies to stationary installations and does not specify limit values for electrical appliances. But intensive magnetic fields also occur in the immediate vicinity of household appliances.