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ELECTRIC AND MAGNETIC FIELDS ASSESSMENT

SECTION 15

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Environmental Assessment Certificate Application

for the RichmondAirportVancouver Rapid Transit Project

15-1 December 2004

15 Electric and Magnetic Fields Assessment

15.1 Executive Summary

This section presents a state-of-the-art review of electric and magnetic fields

(EMF) from electric transportation systems, undertaken by Paul Wong

International, Inc. in October 2003. Magnetic fields from electric transportation

systems are generally more complex than those produced by power lines, and

fields in the frequency range from 0 to 3000 Hertz (Hz) are typically generated.

Electric transportation systems also generate electric and magnetic fields above

3000 Hz. The review of high frequency emission levels and electromagnetic

compatibility (EMC) from various transportation systems is beyond the scope of

this project. However, a general discussion on electromagnetic compatibility ofthe proposed electric transportation system is included in this section. (In

addition, note that SECTION 19.2.3discusses the potential health effects of EMF

associated with electric rail transportation systems).

Based on a review of available literature on EMF from electric transportation

systems, the following conclusions are drawn:

15.1.1 Electric Field (0 to 3000 Hz)

Regardless of the type of transportation technology to be used in the RAV

Project, the expected electric fields from the new rapid transit system will

likely be similar to those measured and calculated for urban mass transit

systems in the U.S. Department of Transportation (U.S. DOT) studies and

International Electrotechnical Commission (IEC) standards. With this

assumption, the expected static (Direct Current (DC), 0 Hz) and extreme low

frequencies (ELF) (5 to 3000 Hz) electric field levels from the new rapid

transit system will be below the International Commission on Non-Ionizing

Radiation Protection (ICNIRP) 24-hour electric field exposure guidelines for

the general public. The ELF electric fields will likely be insignificant whencompared to those generated by common distribution lines found in

residential areas, typically from a few volts per meter (V/m) to 100 or

200 V/m. The static electric field at a distance of 10 m from the track will be

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December 2004 15-2

Electric fields are easily attenuated by most common materials, especially

conductive materials, and do not penetrate significantly into the passenger

vehicles. Structures like buildings, platform overhangs, and vegetationprovide varying degrees of shielding of electric field in station buildings, on

station platforms, and at the wayside.

15.1.2 Magnetic Field (0 to 3000 Hz)

In addition to the power frequency, the RAV rapid transit system will produce

magnetic fields of other frequencies, mostly from 0 to 3000 Hz. The magnetic

fields will have complex frequency spectra, and will be highly variable in

space and time.

Regardless of the type of transportation technology to be used in the RAV

Project, the expected magnetic fields from the new rapid transit system will

likely be similar to those measured and calculated for urban mass transit

systems in the SkyTrain and U.S. DOT studies (after excluding one type of

vehicle due its unique design), and IEC standards. With this assumption, the

expected average static and ELF magnetic field levels from the RAV line will

be below the ICNIRP 24-hour magnetic field exposure guidelines for the

general public. However, it must be noted that the maximum fields at some

locations in the vehicles (e.g., near the traction control equipment), or on

station platforms could exceed the ICNIRP guidelines.

Average power frequency (60 Hz) magnetic fields in the RAV vehicles will

likely be in the range of 10 milligauss (mG), a level comparable to those

found directly under overhead power distribution lines. Exposure to magnetic

fields is a common occurrence in daily life. Power frequency fields near

common household appliances range from less than 1 to about 150 mG at a

distance of one foot from the field source. It should be noted that the field

characteristics associated with household appliances and the RAV rapid

transit system are different (e.g., field levels drop off more rapidly withseparation distance from household appliances than do those from the RAV

line).

Average ELF (i.e., 5 to 3000 Hz) magnetic fields in RAV vehicles and on

station platforms will likely be about 50 and 10 mG, respectively.

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15-3 December 2004

Average static magnetic fields in RAV vehicles and on station platforms will

likely be about 1,000 and 600 mG, respectively. The earths field is about

500 mG, and can be perturbed easily by all common ferromagnetic objects. Astudy shows that the earth's field can be elevated above its natural level

within a distance of eight feet from a subcompact car (e.g., from about 540 to

1100 mG beside the headlight and to 820 mG beside the drivers door), and a

common steel folding chair can change the earth's field by up to 60 mG within

a distance of one foot.

The characteristics of the wayside magnetic field from the RAV rapid transit

system will be similar to those on station platforms, except that the field levels

will decrease rapidly with increasing distance from the tracks. Static magnetic

fields at a distance of 10 m from the tracks will likely be

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December 2004 15-4

comparable to those described in the United Kingdom study by University of

York (2002), it is unlikely that electromagnetic emissions from the RAV line

will interfere with commercial (AM (amplitude-modulated) and FM (frequency

modulated)) radio services in most installations. The probability ofinterference with cable services, such as cable TV, will be even more remote.

Low frequency magnetic field interference with information technology

equipment, such as computer monitors, will not be likely for distances greater

than 10 m from the tracks.

In the unlikely event that an interference complaint does occur, the procedure

to resolve the complaint is similar to that for power lines. Industry Canada will

be contacted for their assistance to determine the cause of the complaint. If

the cause is indeed from the new rapid transit system, the Concessionaire

will endeavour to resolve the complaint by finding a solution that is mutually

acceptable to both the complainant and the Concessionaire.

To minimize the potential interference impacts of electromagnetic fields

associated with the new rapid transit system and to ensure electromagnetic

compatibility within the proposed RAV system and the surrounding

environment, the RAV system contract specifications will contain provisions

to control and monitor stray currents and electromagnetic interference (EMI),

specifically electromagnetic compatibility.

15.2 Introduction

Since the type of transportation technology to be utilized for the RAV Project has

yet to be defined, the review addresses EMF from the existing SkyTrain system

and other guided and non-guided electric transportation systems.

Due to the concern of some members of the public about alleged health effects

associated with exposure to power lines, the majority of the EMF literature covers

power frequency fields2

(National Research Council (NRC) 1997, NationalInstitute of Environmental Health Sciences (NIEHS) 1998 and 1999, Neutra et al.

addition to other activities, the IEC publishes International Standards and collaboratesclosely with the International Organization for Standardization (ISO).2The power frequency is 60 Hz in North America and 50 Hz in most other countries.

Power frequency fields therefore refer to fields in the 50 to 60 Hz range only.

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2002). Due to the characteristics of the onboard electrical systems, magnetic

fields from electric transportation systems are generally more complex than those

produced by power lines, and fields in the frequency range from 0 to 3000 Hz (or

3 kHz, kilohertz) are typically generated (Feero and Dietrich 1995).

Based on the literature review, typical EMF levels from electric transportation

systems in the frequency range from 0 to 3000 Hz will be documented and an

upper bound (i.e., worst-case) for EMF levels from the electric transportation

systems will be derived. Upper bound EMF levels will be compared with the 24-

hour exposure guidelines for the general public established by the ICNIRP.

Electric transportation systems also generate electric and magnetic fields above

3 kHz. These fields are lower in magnitude than those generated in the lower

frequencies, and are generally governed by electromagnetic emission and

electromagnetic compatibility requirements of the transportation system (e.g.,

see technical specifications for SkyTrain Mark II Vehicles for the Millennium Line

(Bombardier 1998)). The review of high frequency emission levels and

electromagnetic compatibility from various transportation systems is beyond the

scope of this project. However, a general discussion on electromagnetic

compatibility of the electric transportation system is included.

15.3 Characteristics of Electric and Magnetic Fields

Electricity is expressed in terms of voltage (measured in volts or kilovolts, V or

kV), current (in amperes or kiloamperes, A or kA), and power (in watts or

kilowatts, W or kW). Our homes are wired for 120 V and 240 V, while power lines

that transport electricity operate at thousands of volts or kilovolts. The amount of

electric power flowing in an electrical circuit is proportional to the voltage

multiplied by the current.

Electricity is used in two basic forms, AC (alternating current) and DC (direct

current). AC is the form of electricity common to all homes. For AC, the voltageand current change polarity like a sinusoidal wave. In contrast, for DC, the

voltage and current remain at the same polarity. Examples of DC electricity are

the ordinary 1.5 V flashlight batteries, and the 12 V automotive batteries.

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Electric and magnetic fields are invisible lines of force surrounding any conductor

or wire carrying electricity and they are found everywhere electricity is used.

They are common to every residence, school, or workplace that receives

electrical service. The term "field" refers to both the lines of force and the regionsin which they occur. All electrical equipment, such as power tools, home

appliances, televisions, hair dryers, household wiring, transportation equipment

and power lines produce EMF. AC power lines produce mainly AC fields at the

power frequency (60 Hz in North America and 50 Hz in most other countries);

while DC power lines produce mainly DC or static fields (0 Hz). The earth itself

produces a DC magnetic field. Most of the power lines are AC lines, and there is

only one high voltage DC transmission line in BC.

An electric field is produced by electric charges along a wire when a voltage is

applied, regardless of whether or not a load current is flowing in the wire. When

the power switch of an appliance is turned on, an electric current begins to flow

and produces a magnetic field. The magnetic field increases in strength with an

increase in current flowing in the wire, while the electric field level generally stays

fairly constant with time since the voltage on the wires is closely regulated by the

power utility. As the amount of electric power carried by a power line, electrical

circuit, or electrical system (such as the electric transportation system) is

proportional to the voltage multiplied by the current, any changes to power or

load demand3 with time results in changes to the current levels, and hence

magnetic fields.

Electric field strength increases with an increase in the voltage on the conductor,

while magnetic field strength increases with an increase in the current flowing in

the conductor. Maximum EMF levels occur near live electrical conductors, such

as a SkyTrain power rail, and decrease rapidly with increasing distance away

from the power-carrying conductors. Electric field is usually measured in volts per

metre (V/m) or kilovolts per metre (kV/m), where 1 kV/m = 1000 V/m; and

magnetic field in milligauss (mG) or microteslas (T), where 1 T = 10 mG.

Not all electric and magnetic fields are the same. They depend on thecharacteristics of the power source which generates the fields. For example, a

DC power source produces static electric and magnetic fields which do not vary

3From a 120 V outlet, a 60 W light bulb requires 0.5 A, while a 600 W light bulb requires

5 A. That is, a higher power demand requires a higher current level when the voltage isthe same.

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15-7 December 2004

in magnitude and orientation with time, while an AC power source produces

electric and magnetic fields which do vary in both magnitude and direction with

time.

Electric and magnetic fields at the power frequency and at other frequencies are

produced by many devices that one encounters daily. For example, in addition to

power frequency fields, a computer monitor also emits EMF into its surrounding

area in the 20 to 70 kHz range, while a microwave oven also generates EMF

within an enclosed metal cavity in the 2 GHz (gigahertz, where 1 GHz =

1,000,000,000 Hz) range.

Frequencies in the electromagnetic spectrum are grouped together into bands.

For example, the MF (medium frequency, from 0.3 to 3 MHz or megahertz) band

covers AM radio broadcast services, and the VHF (very high frequency, from 30

to 300 MHz or megahertz) band covers VHF television (channels 2 to 13) and

FM radio broadcast services. This report covers EMF from transportation

systems in the 0 to 3000 Hz range. While there is no uniform agreement on the

frequency range denoted by the ELF band, this report will use the ELF band to

cover frequencies from 3 to 3000 Hz, and the ULF (ultra low frequency) band to

cover any frequencies below 3 Hz (i.e., from 0 to 3 Hz).

In most situations, ULF and ELF electric fields from outdoor sources such as

power lines do not penetrate into the interior of structures, such as homes. This

is because most of the building materials can essentially block or shield the

passage of the electric lines of force or electric fields. In contrast, the magnetic

lines of force or magnetic fields cannot be blocked or shielded easily by most

building materials.

Magnetic fields from AC power lines in North America consist primarily of a 60 Hz

component. In some cases, there are also harmonic components (i.e., multiples

of 60 Hz), but these are typically small in number. Their spatial distributions can

usually be described by a two-dimensional model.

ELF magnetic fields produced by transportation vehicles are far more complex

than those produced by power lines mainly due to:

Multiple sources - Magnetic fields from a transportation vehicle arise from

multiple sources both within and external to the vehicle. Spatial distributions

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December 2004 15-8

cannot be expressed simply by attenuation curves which are temporally

stable.

Continuous frequency distribution - The time varying component of the

magnetic field often does not exhibit a discrete and temporally stablefrequency distribution. Consequently, field intensities in various frequency

bands rather than fields at specific frequencies must be addressed.

15.3.1 EMF from Electric Power Systems

Power transmission lines bring power from a generating station to a

substation. Power distribution lines bring power from the substation to our

homes. Transmission and distribution lines can be either overhead or

underground. Overhead lines produce both electric and magnetic fields.

Underground lines do not produce electric fields above ground but doproduce magnetic fields. Typical EMF levels for power transmission lines are

shown in Figure 15.1(NIEHS 2002).

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15-9 December 2004

Figure 15.1 Typical EMF Levels for Power Transmission Lines

Source: NIEHS 2002.

Electric fields directly beneath power lines may vary from a few volts per

meter for some overhead distribution lines to thousands of volts per meter for

high voltage transmission lines. The electric field strength can be reduced by

the walls and roofs of most buildings, whereas magnetic fields are not

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reduced by most building materials. Both electric and magnetic field levels

decrease rapidly with increasing distance from the line.

The distance at which the magnetic field from a power line becomesindistinguishable from typical background levels differs for different types of

lines. At a distance of 90 m and at times of average electricity demand, the

magnetic fields from many transmission lines can be similar to typical

background levels found in most homes.

Typical voltage for power distribution lines ranges from 4 to 35 kV. Electric

field levels directly beneath overhead distribution lines may vary from a few

volts per meter to 100 or 200 V/m. Magnetic fields directly beneath overhead

distribution lines typically range from 10 to 20 mG for main feeders and less

than 10 mG for laterals. Such levels are also typical directly above

underground lines. Peak EMF levels, however, can vary considerably

depending on the amount of current carried by the line. Peak magnetic field

levels as high as 70 mG have been measured directly below overhead

distribution lines and as high as 40 mG above underground distribution lines

(NIEHS 2002).

The strongest EMF outside a substation comes generally from the power

lines entering and leaving the substation. The strength of the EMF from

equipment within the substations, such as transformers, reactors, and

capacitor banks, decreases rapidly with increasing distance away from the

equipment. Beyond the substation fence or wall, the EMF produced by the

substation equipment is typically indistinguishable from background levels.

15.3.2 EMF in Homes

Electric fields in homes typically range from 0 to 10 V/m, whereas magnetic

fields vary greatly (NIEHS 2002). Both electric and magnetic field levels

decrease rapidly with increasing distance from the source.

In a study by the U.S. Electric Power Research Institute (EPRI) in which spot

measurements of magnetic field were made in the center of rooms in 992

homes throughout the US, half of the houses had magnetic field levels of

0.6 mG or less, when the average of measurements from all the rooms in the

house was calculated; and the all-room mean magnetic field for all houses

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was 0.9 mG (NIEHS 2002). The measurements were made away from

electrical appliances and primarily reflect the fields from household wiring and

outside power lines.

In general, the background level of magnetic field within a residence depends

mainly on the proximity and loading of adjacent power lines, and the internal

wiring in a house does not contribute significantly to the background level.

However, the conditions in apartment blocks may be similar to those

encountered in multi-storey commercial buildings where the building main

supply wires may contribute significantly to the background level.

Magnetic field levels near household electrical appliances can be higher than

those from other sources, including power lines. However, appliance fields

decrease in strength with distance more quickly than do power line fields.

Table 15.1 lists median magnetic field levels generated by common

household appliances using AC power (U.S. Environmental Protection

Agency (U.S. EPA) 1992). Magnetic field strength does not necessarily

depend on how large, complex, or powerful the appliance is. Magnetic fields

near larger appliances are often weaker than those near smaller ones.

Appliances may have been redesigned since the data were collected, and the

fields they produce today may differ considerably from those shown in

Table 15.1(NIEHS 2002).

Table 15.1 Median Magnetic Field Levels Household Electrical

Appliances

Magnetic Field at Various Distances

from Source (mG)1Room Source

6 1 2 4

Office Air cleaners

Copy machines

Fax machines

Fluorescent lights

Electric pencil sharpeners

Video display terminals2

180

90

6

40

200

14

35

20

-

6

70

5

5

7

-

2

20

2

1

1

-

-

2

-

Bathroom Hair dryers

Electric shavers

300

100

1

20

-

-

-

-

Workshop Battery chargers 30 3 - -

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Magnetic Field at Various Distances

from Source (mG)1Room Source

6 1 2 4

DrillsPower saws

150200

3040

45

--

Living

Room

Ceiling Fans

Window Air Conditioners

Color Televisions2

-

-

-

3

3

7

-

1

2

-

-

-

Kitchen Blenders

Can Openers

Coffee Makers

Dishwashers

Food Processors

Garbage Disposals

Microwave Ovens2

Mixers

Electric Ovens

Electric Ranges

Refrigerators

Toasters

70

600

7

20

30

80

200

100

9

30

2

10

10

150

-

10

6

10

4

10

4

8

2

3

2

20

-

4

2

2

10

1

-

2

1

-

-

2

-

-

-

-

2

-

-

-

-

-

Bedroom Digital Clocks3

Analog Clocks3

Baby Monitors

-

-

6

1

15

1

-

2

-

-

-

-Laundry/

Utility

Electric Clothes Dryers

Washing Machines

Irons

Portable Heaters

Vacuum Cleaners

3

20

8

100

300

2

7

1

20

60

-

1

-

4

10

-

-

-

-

1

Source: U.S. EPA 1992.Notes:1. Dash (-) means that the magnetic field at this distance from the operating appliance

could not be distinguished from background measurements taken before theappliance was turned on.

2. Some appliances produce both 60 Hz and higher frequency fields (e.g., televisions

and computer screens produce fields at 10-30 kHz, as well as 60 Hz). Microwaveovens produce 60 Hz fields of several hundred mG, but they also generatemicrowave energy inside the appliance that is at a much higher frequency, about2.45 GHz. We are shielded from the higher frequency fields but not from the 60 Hzfields.

3. Measurements were taken from clocks that were AC-powered. Most digital clockshave low magnetic fields. In some analog clocks, however, higher magnetic fields areproduced by the motor that drives the hands.

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15.4 EMF Guided Electric Transportation Systems

Electric traction systems typically can be divided into two categories

according to the power supply systems (IEC 1998):

DC Systems

Traction power is developed by DC motors operating in the voltage range

from about 500 to 3000 V. Voltages lower than approximately1500 V are

used mostly for urban transit systems, light rails, metros, subways or rapid

transits; whereas voltages above approximately1500 V are used mostly for

commuter (i.e., suburban or regional) rails. Current is supplied via a live feed

rail (third rail system) or overhead wire (catenary), and returns partly through

the normal running rails (sometimes a fourth rail), and partly through the

earth. The traction power system is supplied from the local utilitys powernetwork through three-phase rectifiers giving a ripple fundamental at six times

the network power frequency (IEC 1998).

Typical maximum traction currents appropriate to normal running conditions

are:

tram lines: up to ~1 kA

underground lines: up to ~4 kA

AC Systems

Operating voltages generally range from about 11 to 25 kV (sometimes up to

50 kV with autotransformers), and the supply frequency is generally 16 2/3,

25, 50 or 60 Hz. The lower operating frequencies (16 2/3 and 25 Hz) are

used only for voltages below approximately 15 kV. The current is supplied via

overhead wires with or without the use of auto or booster transformers to

direct the return current from the rails to the overhead return wire.

Typical maximum traction currents appropriate to normal running conditions

are:

on single track branch lines: up to ~0.5 kA

on double track main lines: up to ~2.0 kA

on suburban lines: up to ~2.5 kA (main line and suburban line

running side by side)

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The traction power is generally supplied from the local electric utility to a

substation where the AC power is converted to DC power, or appropriate AC

voltage level and frequency, as required by the traction system. The power is

then transmitted to the traction vehicle via a system of flexible suspensioncontact lines (the overhead catenary) with which a vehicle-mounted

articulated device (the pantograph) is brought into contact. On low voltage

lines, a trackside conductor rail may be provided from which power is

collected by a sliding contact (the collector shoe).

On the traction vehicle, the power is regulated and supplied to electric motors

to control the movement of the vehicle. Auxiliary power is also regulated and

although of lower power than that supplied to the traction motors, can still be

a significant source of EMF and electromagnetic noise.

The locomotive supplies power, generally at voltages "1500 V (sometimes at

3000 V) and at powers up to 800 kW, to the electrical systems of the train for

lighting, heating, air-conditioning, battery charging, and converters. This

auxiliary current may return to the locomotive via the rails.

The most comprehensive studies on the characterization of the EMF

environment of guided transportation systems were carried out by the U.S.

DOT, Federal Railroad Administration, John A. Volpe National Transportation

System Center (U.S. DOT 1992, 1993a, 1993b, 1993c, 1993d, 1993e, 1993f;

Muc 2001). The results show that the frequency spectra of magnetic field

from the transportation systems are complex and highly variable over time

(see Figure 15.2 (U.S. DOT 1992)). In comparison, the fields from power

lines are predominantly in the power frequency, and are more stable

temporally. The major instrument used in these studies was a portable Multi-

wave system developed by Electric Research and Management Inc. of

Pennsylvania (EPRI 1992). The five guided ground transportation systems

studied were:

Transrapid TR07 Maglev System Attractive electromagnetic suspension(EMS) maglev (magnetic levitation) technology. Active guideway. Linear

synchronous motor (LMS), 55 to 215 Hz. Inductively coupling from

guideway. Dynamic braking (resistors at inverter station). Test track in

Emsland, Germany.

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Train Grande Vitesse (TGV) A high speed rail system.

Autotransformer fed catenary 25 kV, 50 Hz, or DC 1.5 kV catenary.

Variable frequency inverter control with AC motors. Regenerative braking

for high speed, dynamic braking for low speed. Traction power equipmentin locomotives. Paris to Tours, France. Test train and revenue service.

Amtrak Northeast Corridor (NEC) and New Jersey Transit (NJT) North

Jersey Coast Line (60 Hz AC power segment, Long Beach section) -

Controlled rectifiers and DC motors for electrified sections. Dynamic

braking (resistors above locomotive). Traction power equipment in

locomotives. Revenue service.

- NEC (Washington, DC - New York) Double fed catenary, 11 kV, 25

Hz.

- NEC (New York - New Haven)-Autotransformer fed catenary, 12.5 kV,

60 Hz.

- NEC (New Haven - Boston) Diesel-electric, 105 Hz alternators,

rectifiers and DC motors.

- NJT (Matawan - Long Branch) Single fed catenary, 12.5 kV, 60 Hz.

Washington, DC Metropolitan Area Transit Authority (WMATA) Metrorail

DC 750 V, third rail. Cam or 273 Hz chopper control with DC motors.

Regenerative braking for high speed, dynamic braking for low speed

(resistors under vehicles). Traction power equipment beneath each

vehicle. Gaithersburg, Maryland to Washington, DC revenue service.

Massachusetts Bay Transit Authority (MBTA) Subway DC 600 V, third

rail or catenary. Cam or 218 Hz chopper control with DC motors. Dynamic

braking (resistors under vehicles). Traction power equipment beneath

each vehicle. Boston metropolitan area revenue service.

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Figure 15.2 Example of Magnetic Field Versus Frequency and Time

Source: U.S. DOT 1992. Figure 3-3.

(112 cm above floor, Inside Transrapid TR07 maglev vehicle)

Magnetic Field Characteristics

The characteristics of the magnetic field are controlled by the electric current

flowing in the wires. In electrified rail systems using overhead catenaries, AC

current from the nearby substation or autotransformer flows in the catenaries

via a pantograph to the locomotive or powered passenger vehicle, and

returns to the substation or autotransformer via the running rails. This current

loop is a major magnetic field source near electrified railroads. The situation

is also true for urban mass transit systems, which usually receive DC power

from a third (supply) rail. In this case, the current loop formed by the supply

rail and the return (running) rails is smaller and therefore a less effective

magnetic field source than the catenary-track current loop.

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The loop current varies with time according to the traction power demand.

This results in a corresponding change in the magnetic fields in the vehicle

and along the guideway. Factors such as train length, onboard load,

acceleration and deceleration rates, track incline and train speed affect thetraction power requirement. For same system voltage, larger trains requiring

higher power produce higher magnetic field levels than those produced by

smaller, lighter and slower trains.

For catenary-powered transportation systems, the magnetic field produced by

the larger current loop is spatially rather uniform throughout the train. The

spatial variability was more complicated for the TGV, where a high voltage

cable ran across the roofs of the vehicles carrying power from the rear

locomotive to the front locomotive, and caused magnetic fields to be higher

near the ceilings than near the floor in the passenger compartments (U.S.

DOT 1993b). For third rail systems, the magnetic field tends to be higher near

the floor of the vehicle (due mainly to under-car traction control equipment)

and lower near the ceiling (U.S. DOT 1993c). In general, the onboard traction

equipment and other onboard electrical systems can also be significant

magnetic field sources (Feero and Dietrich 1995).

Currents in the catenary-track or third rail-track circuit produce magnetic

fields along the wayside, on station platform, and in the train. The wayside

and platform fields have the same frequency characteristics as those in the

train, and generally the same temporal variability as long as the train is within

the same power block between substations or autotransformers. The field

levels along the wayside drop significantly once the train passes to the next

substation or autotransformer beyond the wayside point of interest, and

attenuate rapidly with increasing distance from the tracks.

In the Transrapid TR07 maglev system, the traction power is produced by a

moving magnetic field in the long stator of the guideway (linear synchronous

motor propulsion). The frequency of the magnetic field produced by the

guideway varies linearly with the speed of the vehicle. Hence, unlikeconventional transportation systems, the active guideway represents a major

magnetic field source. The guideway of any transportation system using

linear synchronous motor or linear induction motor technology is likely to

produce magnetic fields of characteristics similar to those produced by the

TR07 system (U.S. DOT 1993e).

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Unlike other transportation systems, the TR07 system uses magnetic fields

for vehicle levitation and guidance; they are nominally static fields but require

dynamic control to maintain gap equilibrium, thus resulting in a significant

time varying component. Magnetic fields from the levitation and guidancemagnets, and from currents in the under-car cables providing power to these

magnets, were detected in the vehicle, and briefly along the guideway or at

the station when the vehicle was present.

Magnetic fields from electrical equipment in rectifier stations, transformer

yards and other power supply and conditioning stations fall off rapidly with

distance away from the equipment, and their influence generally are confined

within the station property line. Significant magnetic fields were not measured

beyond station property lines where the general public may be found (U.S.

DOT 1993e).

Electric Field Characteristics

According to the U.S. DOT studies, the two major electric field sources for

electrified railroads are the high voltage (11 to 25 kV) overhead catenaries

(including the catenary feeder conductors in the autotransformer fed

systems), and the overhead transmission lines that supply power to the

substations.

Third rail and catenary circuits of the urban mass transit systems are not

significant electric field sources in areas routinely accessible to workers or the

general public. The voltage on these systems is relatively low (600 to 750 V),

and power delivery to traction power substations is typically at distribution

voltage level. Hence, electric fields associated with urban mass transit

systems are similar to those near common distribution lines along residential

streets (U.S. DOT 1993e).

Electric fields were not measured near the power supply facilities associated

with the TR07 system. The field levels from the 110 kV transmission line

supplying power to the facilities were likely to be similar to those produced byother high voltage transmission lines.

Since the electric field is related to the voltage of the power supply line or

catenary, the frequency of the electric field is the same as the frequency of

the power supply line or catenary. The AC power grid frequency is 60 Hz for

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North America, or 50 Hz for most other parts of the world. Power frequencies

of 16 to 25 Hz, which were commonly used prior to the standardization of the

power frequency, are still being used in some railway systems, such as a

portion of the Amtrak Northeast Corridor.

As the voltage of the supply line or catenary is closely regulated, the electric

field shows little temporal variability. AC electric field levels exceeding 100

V/m generally occur within ~30 m of the tracks (U.S. DOT 1993a, 1993b) or

within ~40 m of high voltage transmission lines (U.S. DOT 1993b).

Some urban transit systems use an overhead catenary to supply power to the

vehicles. For example, in the MBTA system, the catenary voltage is 600 V

DC, which produces an estimated DC field of 50 V/m or less on station

platforms, or at road crossings directly under the catenary (U.S. DOT 1993e).

Electric fields are easily attenuated by most common materials, especially

conductive materials, and do not penetrate significantly into the passenger

compartments of the trains. Structures like station buildings, platform

overhangs, and vegetation provide varying degrees of shielding of electric

field in station buildings, on station platforms, and at the wayside.

15.4.1 Magnetic Field - Guided Transportation Systems

As the initial tests for the U.S. DOT studies (U.S. DOT 1992, 1993a, 1993b,

1993c, 1993d, 1993e, 1993f) indicated that there were no significant

components of magnetic field in frequencies from 2565 to 3000 Hz, magnetic

field data were collected in the frequency band from 0 to 2560 Hz, instead of

the entire ULF and ELF bands from 0 to 3000 Hz, in order to achieve a

twofold increase in the amount of recordings that could be saved in the

waveform recorder (Feero and Dietrich 1995). The following frequency

partitions were used in the data analyses:

Static or DC (0 Hz) The magnetic field component which did not vary inintensity or orientation over the time of the waveform

snapshot.

ELF frequencies

(5 to 2560 Hz)

The total time varying magnetic field measured by the

field sensor. Measured signals were processed

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digitally using FFT (Fast Fourier Transform) from 2.5

to 2562.5 Hz. Since the bandwidth of each FFT

component was 5 Hz, the centre frequencies of the

components were from 5 to 2,560 Hz.

Sub-power

frequencies

(5 to 45 Hz)

The total field measured with components below the

power frequencies of common electric power systems

(i.e., 50 and 60 Hz). The center frequencies of the FFT

components ranged from 5 to 45 Hz with the actual

bandwidth from 2.5 to 47.5 Hz.

Power frequencies

(50 to 60 Hz)

The total field measured with components in the

frequency range of the common power systems. The

center frequencies of the FFT components ranged

from 50 to 60 Hz with the actual bandwidth from 47.5

to 62.5 Hz.

Power frequency

harmonics

(65 to 300 Hz)

The total field measured with the centre frequencies of

the FFT components from 65 to 300 Hz, and the actual

bandwidth from 62.5 to 302.5 Hz. This band includes

the first few harmonics above the power frequency,

and many of the components generated by various

sources in the vehicles.

High ELF

frequencies

(305 Hz to 2560 Hz)

The total field measured with the centre frequencies of

the FFT components from 305 to 2560 Hz, and the

actual bandwidth from 302.5 to 2562.5 Hz. The

common power systems typically do not produce

significant fields in this frequency band.

15.4.1.1 Passenger Compartments

Measurements were conducted at many locations in the passengercompartments of the transportation vehicles. The Amtrak Northeast Corridor,

New Jersey Transit, North Jersey Coast Line (Long Beach), and French

TGV-Atlantique (TGV-A) are intercity rail systems that use high voltage AC

catenaries. They carry large passenger loads over relatively long distances

and at high speeds. The dominant field source is current in the catenary-track

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loop. Although the Transrapid TR07 maglev vehicle is different from other

intercity rail vehicles in its propulsion, guidance, and suspension technology,

the measurements show similarities in field characteristics such as spatial

uniformity over the length of the vehicle, temporal variability with tractionpower needs, and time varying magnetic fields in the same range of

frequencies.

Table 15.2 is a summary of average and maximum magnetic field levels in

the passenger compartments of the intercity rail vehicles (U.S. DOT 1993e).

With the exception of the TR07 maglev vehicles, the field levels were

relatively uniform in the passenger compartments and the maximums and

averages of all measurements (at various measurement heights) in the

passenger compartments were tabulated. For TR07, only data measured at

47 cm above the floor were tabulated. Including average and maximum

values of all the data in the TR07 passenger compartments without regard to

height above the floor is misleading because of the high field levels near the

floor (see Figure 15.3) (U.S. DOT 1993e).

From Table 15.2, the highest time varying field was found on the NEC-25 Hz

section because of higher speed, hilly terrain and a lower catenary voltage

(11 kV, hence higher current for the same power requirement), and occurred

in the frequency band containing the catenary power frequency. Lower fields

were found on the NEC-60 Hz section due to flatter terrain, lower speed, and

higher voltage (12.5 kV versus 11 kV). Even lower fields were found on the

TGV-A system due to its higher catenary voltage (25 kV versus 12.5 kV for

NEC) and lower catenary current (for the same power requirement).

Magnetic field levels measured in the vehicles on the NEC non-electrified

section were mainly due to hotel services unrelated to electric traction

power.

In terms of magnitude and frequency contents, magnetic fields from all

transportation systems were not significantly different from each other (see

Figure 15.4) (U.S. DOT 1993e). However, the frequency characteristics weredifferent from those reported for other common magnetic field sources (e.g.,

Figure 15.5shows a comparison of magnetic fields in a maglev vehicle with

those near transmission lines, distribution lines, and household appliances).

With the increasing use of solid state devices, distribution lines and

household appliances may generate more than just power frequency fields

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December 2004 15-22

(U.S. DOT 1993e). In a study comparing various types of ELF-EMF exposure

environments, the authors concluded that maglev technology, as evidenced

by the TR07 system, does not present substantially unique exposure to

passengers or crew (U.S. DOT 1993f).

The average static field at ~50 cm above the floor of the TR07 vehicle was

about the same as that in other intercity rail systems where the only known

static field source was the geomagnetic field. In general, the geomagnetic

field can be affected easily by nearby ferromagnetic objects. Around the

Emsland test site, the earths field is ~490 mG. The measured geomagnetic

field was distorted by the TR07 guideway structure, producing enhanced field

above or below the structure, and reduced field alongside the structure.

Inside the vehicle, average static fields ranged from ~835 mG near the floor

to ~500 mG at the standing head level. The static fields were more spatially

variable, but slightly more stable over time than the time varying fields.

Urban mass transit systems in the U.S. DOT studies consisted of individually

powered vehicles connected to 600 V (MBTA) or 750 V (WMATA) DC power

supply systems using a third rail, with the exception of one system. The

MBTA Blue Line cars operated on third rail while in tunnels and on catenaries

while above surface; the magnetic field environment did not change

appreciably between the two arrangements.

Most of the urban mass transit vehicles in the U.S. DOT studies used the

older cam power control technology, where the power supplied to the

traction motors was controlled by electromechanical contactors operated from

a cam switch. The MBTA Green Line cars and the WMATA 3000 Series cars

used more modern electronic chopper technology to control the power to

the traction motors. The chopper frequencies were 218 and 273 Hz for the

Green Line cars and 3000 Series cars respectively. Magnetic fields from the

modern Green Line cars were similar to those from the older MBTA cam

controlled cars (U.S. DOT 1993d). Likewise, the fields in the front and back

sections of the WMATA 3000 Series cars were similar, but in the centresection, the field characteristics were unique in amplitude, frequency

spectrum and spatial variability, and strongly dependent on height above the

floor (see Figure 15.6) (U.S. DOT 1993c). For the same reason as given for

TR07 maglev vehicles, only average and maximum field values measured at

a height of 60 cm above the floor are shown in Table 15.3(U.S. DOT 1993e).

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From Tables 15.2 and 15.3, the ELF field levels in the urban mass transit

vehicles were lower than those in the intercity rail vehicles, with the exception

of the WMATA 3000 Series cars. In the urban mass transit vehicles, the ELF

fields were produced by the traction current in the under-car power controlequipment. The current in the third rail or catenary and running rails circuit

produced fields in the lower frequency bands. The static field was elevated

above the geomagnetic field due to the DC current in the third rail-track or

catenary-track circuit, and the under-car power control equipment.

The static and ELF fields produced by the smoothing reactor (an inductor

used for reducing ripples in the DC current) beneath the center of the

WMATA 3000 Series cars were substantially greater than those in other

urban mass transit vehicles. Since similar field characteristics were not

observed in the MBTA Green Line cars employing similar chopper

technology, the authors concluded that the high field levels were a result of

the specific design of the smoothing reactors, and not inherent characteristics

of the chopper controlled propulsion systems (U.S. DOT 1993e). In addition,

an improvement in the design of the magnetic circuit could reduce the stray

field generated by the smoothing reactor by orders of magnitude (Feero and

Dietrich 1995).

For both the MBTA high speed trolley and trolley buses, the highest field

levels typically occurred closest to the floor in almost all frequency ranges.

This again indicated the dominant field source was the traction and control

equipment under the floor.

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Table 15.2 Magnetic Field - Intercity Rail Vehicles Passenger Areas

(Average (and maximum) field levels in mG)

Transportation

System

Static

DC

0 Hz

Sub-Power

Freq.

545 Hz

Power

Freq.

5060 Hz

Power Freq.

Harmonics

65300 Hz

High ELF

Freq.

3052560 Hz

ELF

Freq.

52560 Hz

NEC

25 Hz

606

(1763)

132.0

(776.0)

6.0

(41.4)

16.2

(95.2)

2.7

(14.7)

133.8

(782.1)

NEC

60 Hz

630

(1039)

1.4

(12.2)

52.0

(407.0)

5.7

(43.9)

1.4

(12.8)

52.5

(408.4)

NEC

Non-electric

569

(1033)

1.4

(6.7)

4.8

(26.3)

0.7

(5.9)

0.2

(1.9)

5.2

(26.5)

NJT

Long Beach

734

(1016)

1.6

(13.0)

18.2

(107.1)

2.5

(17.7)

0.7

(3.6)

18.6

(108.8)

TGV

AC Section

545

(962)

23.3

(106.2)

30.5

(164.7)

2.7

(10.4)

1.5

(5.4)

43.2

(165.0)

TR07*

Maglev

611.1

(1110)

47.6

(141.4)

7.7

(29.4)

18.5

(35.5)

1.2

(2.5)

52.4

(143.2)

Source: U.S. DOT 1993e. Table 3-1 and U.S. DOT 1992. Table 3-2.

*Values for TR07 Maglev represent measurements at 47 cm above the floor, see Section 15.4.1.1 text. Average levels for other types ofequipment were derived from several measurement heights.

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15-25 December 2004

Figure 15.3 Magnetic Field Versus Height - TR07 Maglev Vehicle

Passenger Areas

Source: U.S. DOT 1993e. Figure 2-6.

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Figure 15.4 Magnetic Field Versus Frequency - Intercity Rail and

Urban Mass Transit Vehicles Passenger Areas


Maximum (bar top) and average (horizontal line) field levels

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15-27 December 2004

Figure 15.5 Magnetic Field Comparison - TR07 Vehicle and Other

Sources



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December 2004 15-28

Figure 15.6 Magnetic Field Versus Height WMATA 3000 Series Metrorail

Car Passenger Areas


Table 15.3 Magnetic Field Urban Mass Transit Vehicles Passenger

Areas (Average (and maximum) field levels in mG)

Transportation

System

Static

DC

0 Hz

Sub-

Power

Frequency

545 Hz

Power

Frequency

5060 Hz

Power

Freq.

Harmonics

65300 Hz

High ELF

Frequency

3052560

Hz

ELF

Frequency

52560 Hz

WMATA

Subway (Cam)

Cars

1013

(4714)

9.9

(64.5)

1.0

(5.6)

1.6

(9.3)

0.9

(5.0)

9.4

(64.8)

WMATA*

3000 Series Cars

2685

(23732)

98.5

(423.9)

12.6

(50.8)

133.5

(248.6)

41.2

(61.6)

177.8

(443.6)

MBTA

Subway Cars

534

(1981)

5.2

(66.0)

1.1

(14.7)

1.4

(18.3)

0.7

(4.7)

5.7

(68.4)

MBTA

High Speed

Trolley

719

(3074)

4.1

(25.6)

0.8

(4.8)

0.7

(3.7)

0.3

(1.8)

4.5

(26.0)

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15-29 December 2004

Transportation

System

Static

DC

0 Hz

Sub-

Power

Frequency

545 Hz

Power

Frequency

5060 Hz

Power

Freq.

Harmonics

65300 Hz

High ELF

Frequency

3052560

Hz

ELF

Frequency

52560 Hz

MTBA

Trolley Bus

273

(467)

1.7

(12.9)

1.6

(6.5)

0.8

(3.4)

1.3

(9.3)

3.2

(13.2)

Source: U.S. DOT 1993e. Table 3-2.*Values for WMATA 3000 Series Cars represent measurements at 60 cm above the floor,see Section 15.4.1.1 text. Average levels for other types of equipment were derived fromseveral measurement heights.

15.4.1.2 Passenger Platforms

Magnetic field measurements were taken on both outdoor and underground

station platforms, generally at the yellow safety line near the edge of theplatform at both the arriving and departure ends, as well as at other points

near the center of the platform. In addition, measurements were taken on

escalators, on mezzanines, and in waiting lounges. As passengers were not

permitted on the outdoor platform when TR07 maglev vehicles were passing,

magnetic fields were measured at the station door leading to the platform.

The major magnetic field source on station platforms was the AC or DC

current in the catenary-track or third rail-track circuit, or active maglev

guideway. The field characteristics were similar to those in the vehicles and

were determined by the type of electrification. Secondary magnetic field

sources on the platforms were currents in nearby electric circuits, or in

structural members of the platform.

Table 15.4 shows averages and maximums of all measurement data for

station platforms and waiting areas. Magnetic field levels in waiting lounges

were considerably lower than those on the platforms.

Measured magnetic field levels in the TR07 passenger station were similar to

those along the guideway. While a vehicle was passing the station, the timevarying field level near the edge of the loading platform could approach 300

mG. However, passengers were not permitted in this area when there was a

passing vehicle. Within the waiting area in the station, the time varying fields

produced by the passing vehicle could approach approximately 20 mG. As at

other locations along the guideway, the fields had a complex frequency

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December 2004 15-30

spectrum, with the largest field components in the low frequencies, and they

occurred briefly while the vehicle was passing the station.

The static field for the intercity rail systems was mainly due to thegeomagnetic field and was fairly constant with time. When a train was in the

station, the geomagnetic field was perturbed, producing some of the

maximum values in Table 15.4. The static field near the platform surface was

spatially quite variable, probably due to perturbation from the structural steel

in the platform.

Time varying fields for the intercity rail systems were dominated by the

characteristics of the catenary current. Temporal variability of the field on the

platform was larger than that in the vehicles because there was little or no

magnetic field from the catenary-track circuit when the train was beyond the

first substation or autotransformer away from the station platform.

Time varying field levels on platforms for urban mass transit systems were

typically smaller than those for intercity rails because catenaries were not

generally used to carry current in the former systems. Low frequency

magnetic fields from fluctuating DC traction current were larger at stations

with catenaries (MBTA outdoor-catenary) than those at stations with third

rails. Higher frequency (>60 Hz) magnetic fields were most prevalent at urban

mass transit stations that were served by chopper-controlled vehicles

because of fields generated by the onboard chopper control equipment.

Static fields were more variable with time due to fields produced by the DC

current in the third rail-track or catenary-track circuit. The average static fields

were not elevated in any consistent manner.

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15-31 December 2004

Table 15.4 Magnetic Field Station Platforms and Waiting Lounges Passenger Areas

(Average (and maximum) field levels in mG)

Transportation

System

Static

DC

0 Hz

Sub-Power

Freq.

545 Hz

Power

Freq.

5060 Hz

Power Freq.

Harmonics

65300 Hz

High ELF

Freq.

3052560 Hz

ELF

Freq.

52560Hz

NEC 25 Hz

Princeton Junction Platform

422

(970)

38.1

(537.0)

1.1

(13.8)

8.8

(121.2)

1.6

(17.1)

39.6

(550.8)

NEC 60 Hz

New Rochelle Platform

650

(1629)

0.9

(51.5)

59.8

(407.2)

15.6

(101.6)

4.9

(26.6)

62.2

(417.6)

NJT 60 Hz

Red Bank Platform

525

(615)

0.6

(4.8)

28.0

(209.4)

8.0

(50.6)

2.6

(15.7)

28.8

(213.2)

NEC Non Electric

South Station Lounge

511

(912)

0.2

(0.7)

0.4

(0.7)

0.1

(0.3)

0.0

(0.1)

0.5

(1.1)

NEC 25 Hz

Penn Station Lounge

573

(1372)

6.0

(13.4)

0.5

(0.9)

1.0

(2.2)

0.1

(0.3)

6.1

(13.6)

Transrapid TR07

Passenger Lounge

547

(549)

0.1

(12.4)

0.1

(6.3)

0.1

(14.9)

0.0

(1.3)

0.2

(19.5)

TGV A (AC Section)

Vendome Platform

460

(485)

0.3

(0.9)

7.0

(43.8)

0.6

(1.6)

0.7

(1.5)

9.0

(43.9)

WMATA-Outdoor-Chopper

Grosvenor Platform

455

(2065)

0.9

(20.4)

1.7

(3.7)

1.5

(57.7)

0.8

(26.0)

3.1

(66.6)

WMATA-Outdoor

Grosvenor Escalator

424

(1090)

0.5

(2.4)

1.2

(4.5)

0.4

(0.9)

0.3

(1.5)

1.5

(5.1)

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December 2004 15-32

Transportation

System

Static

DC

0 Hz

Sub-Power

Freq.

545 Hz

Power

Freq.

5060 Hz

Power Freq.

Harmonics

65300 Hz

High ELF

Freq.

3052560 Hz

ELF

Freq.

52560Hz

WMATA-Underground

Gallery Place Platform

385

(953)

1.0

(12.7)

0.3

(1.8)

0.6

(8.4)

0.9

(3.3)

1.5

(15.5)

WMATA-Underground

Gallery Place Mezzanine

455

(1004)

0.3

(0.8)

0.3

(0.5)

0.2

(0.5)

0.2

(1.3)

0.5

(1.5)

MBTA-Underground

Several Platforms

625

(2411)

2.0

(20.5)

2.6

(9.5)

1.4

(4.1)

0.8

(2.2)

4.0

(23.0)

MBTA-Outdoor-Catenary

Wood Island Platform

612

(1718)

6.5

(81.4)

2.9

(6.4)

1.4

(7.9)

1.4

(3.9)

8.6

(82.0)

MBTA-Underground-Chopper

Government Center Platform

515

(912)

2.1

(8.0)

0.9

(3.8)

2.7

(16.2)

1.1

(7.8)

4.0

(17.6)

Source: U.S. DOT 1993e. Table 3-3.

Note: Average levels for different equipment types were derived from several measurement heights.

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15-33 December 2004

15.4.1.3 Wayside Locations

Wayside measurements were carried out at the sides of the tracks with trains

passing in either direction and at highway overpasses and underpasses. The

characteristics of the field along the track rights-of-way were very similar to

those on station platforms except that the field levels decreased rapidly with

increasing distance from the tracks. Measured maximum field data were

combined with theoretical attenuation rates for fields from currents in the

catenary and running rails to produce Figure 15.7(U.S. DOT 1993e).

Figure 15.7 Magnetic Field Versus Horizontal Distance from Tracks

Intercity Rail and Urban Mass Transit Systems


Measurements from the 25 and 60 Hz sections of the NEC Line, the 60 Hz

section of the NJT North Jersey Coast Line, and the 50 Hz section of the

TGV-A Line provided generally consistent time varying wayside field levels.

The range of maximum wayside field levels is shown in Figure 15.7. The

frequency spectrum of the wayside magnetic field of the intercity rail systems

was dominated by the frequency of the catenary current and its harmonics,

as it was at the station and in the vehicles. Average wayside magnetic fields

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December 2004 15-34

were not very meaningful as they were highly dependent on factors such as

rail traffic density, train speed and distance between substations.

Elevated magnetic field levels were only encountered near the TR07guideway for brief periods when the guideway was energized and a vehicle

was passing by. At 10 m from the centreline of the TR07 guideway, the height

of the guideway was not a significant factor in determining the field levels

(U.S. DOT 1992). Although the TR07 maximum field levels were within the

range of field levels for intercity rails (see Figure 15.7), the magnetic field

characteristics (i.e., frequency and temporal variability) along the maglev

guideway were different from those along other intercity rails. Like the fields

inside the vehicle, the guideway fields had a complex frequency spectrum,

with the largest fields in the low frequencies.

The TR07 levitation fields were nominally static fields, and could be detected

briefly along the guideway or at the station, while the vehicle was passing by

or stopped. In the absence of the vehicle, the static magnetic field near the

TR07 guideway was not significantly different form the earths field (U.S. DOT

1992).

The principal magnetic field component produced by the DC current in the

third rail-track circuit of an urban mass transit system was the static

component, which at the wayside was small compared to the geomagnetic

field and could not be reliably measured (U.S. DOT 1993c). However, the

larger loop spacing of the catenary-track circuit of the above surface section

of the MBTA Blue Line produced a measurable static field at the wayside

(U.S. DOT 1993d). The maximum static field levels at the wayside of the

catenary-powered urban mass transit system are shown in Figure 15.7.

Since the maximum field component from the urban mass transit system was

the static component, and was small compared to the geomagnetic field, the

total static field environment at the wayside was not substantially changed.

Theoretically calculated typical maximum magnetic field curves for DC andAC electric traction systems with overhead catenaries are given in an IEC

document (see Figures 15.8and 15.9) (IEC 1998). The calculations are for a

current of 1000 A with 50% of the current returning through the normal rails,

and the other 50% through earth. The DC system is supplied from the AC

power grid through three phase rectifiers giving a ripple frequency six times

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15-35 December 2004

the power grid frequency. Magnetic fields along the wayside vary

considerably according to the position of the moving traction engine relative

to the points of electricity supply. Linear conversion of magnetic field levels is

allowed for other traction currents. Typical maximum traction currentsappropriate to normal running conditions have been discussed in SECTION

15.4:DCSYSTEMS AND ACSYSTEMS.

Figure 15.8 Calculated Typical Maximum Magnetic Field Versus

Horizontal Distance from Tracks DC Railway Line with

Overhead Contact Wire System

Source: IEC 1998. Figure 11.Notes:

Calculations for 1 kA of traction current with 50% of the current returning through therails, and the other 50% through earth.

Contact wires above centre of track (x = 0).

Calculations at 1 m above the surface of the rail.

1 T/kA = 10 mG/kA.

Magnetic fields along the wayside vary considerably according to the position of themoving traction engine relative to the points of electricity supply.

Linear conversion of magnetic field levels is allowed for other traction currents.

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December 2004 15-36

Figure 15.9 Calculated Typical Maximum Magnetic Field Versus

Horizontal Distance from Tracks AC Railway Line with

Overhead Contact Wire System

Source: IEC 1998. Figure 12.Notes:

Calculations for 1 kA of traction current with 50% of the current returning through therails, and the other 50% through earth.

Contact wires above centre of track (x = 0).

Calculations at 1 m above the surface of the rail.

1 T/kA = 10 mG/kA. Magnetic fields along the wayside vary considerably according to the position of the

moving traction engine relative to the points of electricity supply.

Linear conversion of magnetic field levels is allowed for other traction currents.

Table 15.5gives typical maximum EMF levels at the fundamental frequency

(DC or AC), calculated for conductor arrangements regarded to be typical for

the respective type of electrification (IEC 2003b).

A study at a train station along the Milan - Malpensa Airport route in Italy

shows that the measured maximum ELF magnetic field level from the DC

overhead catenary was below approximately 2 mG at a distance of 10 m from

the tracks, and the dominant frequency was 300 Hz (Imposimato 2000). The

author commented that the measured value agreed well with the theoretical

curve in the IEC document. As the current loading at the station was low (i.e.,

tens of amperes) at the time of the measurements, the author predicted that

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15-37 December 2004

the field level could reach approximately 100 mG when the current loading

could be much higher (i.e., hundreds of amperes) in the winter months.

Table 15.5 Typical Calculated Maximum Electric and Magnetic FieldLevels at Fundamental Frequency of Different Electrification

Systems

System Frequency

(Hz)

Electric

field (V/m)

Magnetic field

(mG)

Reference

condition

750 to 1200 V

DC conductor

rail

0

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December 2004 15-38

15.4.1.4 Outside Power Supply Facilities

Measurements were made outside power facilities associated with various

transportation systems, at one or more locations outside the facility fence or

wall where public access was likely and magnetic field levels were expected

to be high (U.S. DOT 1993d).

Power facilities associated with intercity rail systems consisted of transformer

or autotransformer yards. Magnetic fields produced by these facilities were

time varying fields at the network and catenary power frequency and its

harmonics. Temporal variability of the fields was determined by the power

needs of all the trains operating in the track sections served by the station.

Power supply stations for urban mass transit systems were often smaller butmore complicated than those for intercity rails. In addition to AC equipment,

there were rectifier banks for converting AC power to DC power. The DC

output current of the station, fluctuating according to the traction power needs

on the tracks served by the station, produced static and low frequency time

varying fields. In addition, the rectifiers produced magnetic fields at

harmonics of the power frequency.

Inverter stations, containing all components of an intercity rail power supply

station and an urban mass transit power supply station, were used only by

the TR07 maglev system. The DC output from the rectifier banks was

converted into a variable frequency AC current used by the active guideway.

The inverter station produced static and time varying fields with a wide range

of frequencies.

Magnetic fields measured outside power supply facilities associated with

intercity rail systems, urban mass transit systems, and the TR07 maglev

system are shown in Figure 15.10. Near intercity rail system power facilities,

only time varying fields were produced. The only static field was the

geomagnetic field. The principal component of the time varying field was thepower frequency component. Near urban mass transit system power

facilities, a static field produced by the DC current was found in addition to

the geomagnetic field. The principal components of the time varying field

consisted of low frequency and harmonic components.

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Figure 15.10 Magnetic Field Outside Power Stations of Electrified Rail

Systems



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December 2004 15-40

The highest time varying magnetic fields were found near the TR07 maglev

inverter facilities where a wide range of frequencies was present. However, it

was not known whether the public would be permitted as close to the

equipment in a revenue service installation as the location wheremeasurements were made. Although the time varying fields near major

equipment had very complex frequency and time characteristics, the average

field levels were generally below about 2 mG. Feeder cables were the only

major field source outside the power stations. Measured time varying fields

from cables were generally below 2 mG and they attenuated quickly with

distance away from the cables. The cables and power supply equipment had

no measurable effect on the earths field, other than passive perturbation of

the earths field due to the ferromagnetic materials in the structures and

equipment (U.S. DOT1992).

15.4.2 Magnetic Field - SkyTrain System

The SkyTrain, North Americas longest fully automated rapid transit system,

uses advanced rapid transit technology, which employs linear induction motor

(LIM) propulsion and unique steerable suspension. The primary power is 600

V DC (300 V DC), with propulsion power conversion and auxiliary power

conversion equipment onboard each car. It is a five-rail system: two rails for

300 V DC, two running rails and one reaction rail for LIM propulsion. The

chopper frequency of the propulsion control unit is approximately 470 Hz for

Mark I vehicles and approximately 20 kHz for newer Mark II vehicles. The

frequency of the AC current (generally below 100 Hz) in the linear induction

motor is used for controlling the speed of the vehicle. The substation feed is

typically supplied by the B.C. Hydro 3-phase, 12 kV distribution system. The

onboard auxiliary power system is 36V DC for Mark I vehicles; 48V DC and

480 V AC 3-phase for Mark II vehicles.

Magnetic field measurements were obtained from the existing SkyTrain

system (Expo Line, Mark I vehicles): in moving vehicles, at typical

substations, at station platforms and at a trackside location (Takahashi 1993).As field levels were found to vary continuously with time at all locations, field

readings were recorded continuously for intervals of one to five minutes.

From the recorded data, the minimum, maximum and average readings of

each recorded interval were obtained. The recording instruments used in this

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study were EmdexC meters by Electric Field Measurement of Massachusetts,

with 3-dB (decibels) bandwidth typically from about 35 to 400 Hz.4

15.4.2.1 SkyTrain Vehicles

Sixteen measurement locations spaced more or less uniformly from the front

to the rear of the vehicle were selected. Besides readings at the standard

measurement height of 1 m (IEEE 1994), some readings were also taken at

the floor level, and at heights of 0.5 and 1.7 m (see Table 15.6). Magnetic

field levels in the vehicles varied according to many factors, such as track

grade, speed and acceleration rate. At a measurement height of 1 m, the

highest average and maximum readings were 19 and 58 mG, respectively.

Readings were generally higher at lower heights (0.5 m and floor level), and

lower at higher heights (1.7 m). At the floor level, the highest average andmaximum readings were 175 and 1017 mG respectively. At 1.7 m, the

highest average and maximum readings were 6.7 and 20 mG respectively.

For each sample, the peak value was typically three times the average value

(see Figure 15.11).

Table 15.6 Magnetic Field - SkyTrain Vehicles Passenger Areas

(Frequencies: 35 to 400 Hz)

Height Above

Floor

No. of

Samples

Average Field

(mG)

Highest

Average Field

(mG)

Maximum Field

(mG)

1.7 m

1.0 m

0.5 m

Floor Level

6

38

2

6

5.0

9.4

16

109

6.7

19

17

175

20

58

84

1017

All Heights 52 20.6 175 1017

Source: Takahashi 1993.

4The EmdexC meter is normally used for measuring 60 Hz fields, however, it does

respond to fields containing non 60 Hz components since its 3 dB cut-off points (i.e.,those points where the meter response is ~0.7 times of its response at 60 Hz) arerespectively about 35 and 400 Hz.

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December 2004 15-42

Figure 15.11 Magnetic Field Versus Time SkyTrain Vehicle

Source: Takahashi 1993. Graph 3.

(1 m above floor, 35-400 Hz)

15.4.2.2 Station Platforms

Measurements were made at a single island type platform (Scott Road), and

a double island type platform (Edmonds). The ambient magnetic field levels

were

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Figure 15.12 Magnetic Field Versus Time SkyTrain Platform



15.4.3 Near Guideway

On the John Molson walkway near Fairmont Street, the ambient level was

below 1 mG. As a train was passing by this location, the level increased

momentarily to 22 mG (see Figure 15.13).

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December 2004 15-44

Figure 15.13 Magnetic Field Versus Time Near SkyTrain Guideway



15.4.4 Inside Power Substations

For substations, measurements were made at a double unit substation

(Broadway), and three single unit substations (Royal Oak, Joyce and

Nanaimo). Readings were taken both inside and outside the substation

buildings and fenced areas, with the measuring instrument typically at 30 cm

from the closest equipment. For the double unit substation (Broadway), the

highest average and maximum readings inside the substation buildings andfenced areas were 127 and 414 mG, respectively. For the single unit

substations, the Nanaimo substation had the highest readings, with the

highest average and maximum readings at 285 and 528 mG, respectively.

Localized higher readings were found outside the substation buildings.

Presumably these locations were near buried underground AC power cables

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feeding the substations. The general public is not allowed inside the

substations or fenced areas.

15.4.4.1 Outside Power Substations

Outside the Broadway substation, the maximum field level dropped from 6.7

mG on the north side of the substation to 1.4 mG at the centreline of the

sidewalk. Outside the Joyce substation, the maximum level dropped from 21

mG on the south side of the substation to 3.4 mG at the centreline of the

sidewalk. Outside the Royal Oak substation, the maximum level dropped

from 28 mG on the south side of the substation to 1.3 mG at the centreline of

the lane. Outside the Nanaimo substation, the maximum level dropped from

33 mG on the south and north sides of the substation to 0.5 mG at a distance

of 12 m away from the substation.

15.5 EMF Other Transportation Systems

A comprehensive study on the characterization of the EMF environment for

various forms of transportation was carried out by Dietrich and Jacobs (U.S. DOT

1999) as an extension to broaden the previous EMF work discussed in

SECTION15.4.1. It provides extensive static and ELF electric and magnetic field

data for:

Four conventional cars and light trucks.

One diesel transit bus.

One commercial jetliner, while taxiing. The aircraft generators produce

400 Hz electric power, which is carried from the rear to the forward cockpit

area via cables under the cabin floor.

One double-deck diesel-powered ferry boat.

One electricpowered airport shuttle tram. Vehicle obtains 60 Hz electric

power from an energized third rail. Traction motors are on the drive wheels.

Most of the power control equipment is beneath the floor, and some incabinets at both ends of the vehicles.

Five escalators. Drive motors are 60 Hz and usually located at one end of the

escalator.

Four moving walkways at an airport (essentially horizontal escalators).

Five electric cars and light trucks.

Two electric buses for shuttling around airport.

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Two self-powered commuter rail vehicles using variable frequency AC drive.

This type of vehicle was not characterized in the previous work on electrified

rail systems. Unlike conventional trains in which powered locomotives pull a

string of non-powered cars, these self-powered cars have onboard electricmotors and necessary electrical equipment to collect electric power from the

overhead catenaries and propel themselves along the track. The speed of the

AC motors, and hence the speed of the train, is controlled by the frequency of

the electric power supplied to the motors. High power electronics beneath the

car convert the single-phase 60 Hz power collected from the catenaries via a

roof-mounted pantograph to DC power, and ultimately to three-phase AC

power at the frequency appropriate for the speed of the train.

Based on the measurement protocol from previous work, the positions of the

detectors were standardized to capture data at various body locations, various

locations within a vehicle, and various locations on the platform.

Complex (i.e., variable in time and space) ELF magnetic fields were present in

every transportation system examined. The frequency content and magnitude of

the magnetic field vary markedly between transportation systems, at different

places within each vehicle, and at different times at the same location, thus

making it difficult to provide concise comparisons between transportation

systems. To comprehend fully the variation in magnetic field characteristics

among transportation systems and to gauge the variability (spatially and

temporally) within each class of vehicle, one should look beyond the summary

descriptors (e.g., average field levels) and examine the complete summary data

of each transportation system (U.S. DOT 1999).

Time varying electric fields were essentially non-existent in all of the

transportation systems examined except the commuter rail system. Onboard the

vehicle, chest-level 60 Hz electric fields from the 27.5 kV overhead catenary

supply system ranged from ~0 to 18 V/m, averaging 4.6 V/m. No fields were

detectable at harmonics of 60 Hz, nor at any of the other frequencies generated

by the onboard electric traction power equipment. The only time varying electricfields in other transportation systems were low frequency fields associated with

the movement of passengers or test personnel near the measurement site. Static

electric charge on synthetic clothing and other belongings produced a static

electric field. When these objects moved in the vehicle, there was an associated

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time varying component consisting of very low frequency components. The

detected fields were typically in the range of 3 to 30 V/m.

Table 15.7shows a summary of magnetic field levels in various frequency bandsaveraged across a wide range of locations and operating conditions for ten

transportation systems, together with the maximum field levels recorded at any

location and any instant of time. Since thousands of measurements were made

Documents

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