Calculation of Electrical Induction Near Power Lines

7/28/2019 Calculation of Electrical Induction Near Power Lines

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CALCULATION OF ELECTRICALCALCULATION OF ELECTRICALINDUCTION NEAR POWER LINESINDUCTION NEAR POWER LINES

Direction Expertise et Support Technique de TransportLignes, Cbles et environnement

Prepared by : Richard Lehoux, [email protected]

May 2008May 2008


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Scope of the presentationScope of the presentation

1. Calculation of Electric Field

2. Electric field induction in a human body1. IEEE Std80-2000 (Guide for Safety in AC Substation Grounding)2. EPRI (Electric Power Research Institute)3. CSA (Canadian Standard Association)

3. Design criteria

May 13th 2008May 13th 2008CEA EMF WORKHOPCEA EMF WORKHOP22

1. CSA2. HQT (Hydro-Qubec Transnergie)

4. Methods of determining induced current1. Empirical2. Boundary Element Method (BEM)

5. Comparison results: Empirical versus BEM


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Electric field induction in a human bodyElectric field induction in a human body

Range of tolerable current in a human body IEEE Std 80-2000, Article 5.2 "Effect of magnitude and duration"

1mA: threshold of perception 1-6 mA: unpleasant to sustain 10.5 mA: threshold for women let-go currents 16 mA: threshold for men let-go currents Note: the duration of the fault is infinite


Range of tolerable current in a human body EPRI "TRANSMISSION LINE REFERENCE BOOK",

Chapter 8, "Field effect of overhead transmission lines and stations",

Article 8.10 "Electric-field induction in people", paragraph "Response tosteady-State Currents" 5 mA: let-go values for children for a probability of 0.5% have been

conservatively estimated as equal to 5 mA threshold of perception


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Electric field induction in a human bodyElectric field induction in a human body

CSAC22.3 No.1-06, Article A.5.3.1 "Vertical desing clearances of wiresand conductors above ground or rails and Tables 2 and 4"

5 mA: let-go currents



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Design criteriaDesign criteria Height of conductorsHeight of conductors

CSA calculation criteria Article : A5.3.1 Based on the worst-case condition :

Vehicle is insulated from the ground by rubber tires Person contacting the vehicle is touching or standing on a well-grounded surface Induced current in all cases is below 5 mA (Let-go currents) Maximum line to ground voltage


HQT Use CSA design criteria

4,15 m

5 mA


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Methods of determining induced currentMethods of determining induced current

Two methods are available at HQT to determine theinduced current (5 mA let-go) in a human body

Empirical method (EPRI) Eas , fast, chea , a roximate


Boundary Element Method (Maxwell's Equations) Expensive, accurate


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Empirical methodEmpirical method

Method of approximating induced current in objects closeto ground EPRI "TRANSMISSION LINE REFERENCE BOOK"

Chapter 8, "Field effects of overhead transmission lines and stations" Method of approximating calculation of current induced on objects

close to the ground


Figure 8.8.2 "Shape for a rectangular solids"

(The shape is collecting electrical charge)

Many others shape available Horizontal / Vertical cylinder Flat plate House Horse Etc.


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Empirical methodEmpirical method

Sizes of vehicles(m)

Length Width Height

ArticleC22.3-01-06

2003 2006 HQ 2003 2006 HQ 2003 2006 HQ


Truck A5.3.1 15.2 23.0 23.0 2.4 2.6 2,6 4.15 4.15 4,15

Large

farm

A5.3.1 7.6 7.6 7.6 2.4 2.4 2.4 4.15 4.15 4.5 *

TrainA5.3.1

(example 4)4000.0 6.706

* : Height used by HQT


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Calculation with EPRI method to get 5 mA induced in a human body

Size of the truck :Length (A): 23 m

Width (B) : 2.6mHeight (H) : 4.15mCenter : 4.15/2 = 2.08

Ratio :A/B : 23/2.6=9.62

H/B

Empirical methodEmpirical method -- Exemple : TruckExemple : Truck


H/B : 4.15/2.6=1.6

With abacus :S/(A*B)=S/(23*2.6)=5.1

S=304.9

5mA=S*E/300 (E: Electric field)E=(5mA*300)/304.9=4.9kV/m

at 2.08m (center of vehicle) See slide 14 to determine

height of conductors

9.62

1.6

S/(AB

)

A/B

5.1


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Calculation with EPRI to get 5 mA induced in a human body

Size of the Large Farm Vehicle :Length (A) : 7.6 mWidth (B) : 2.4m

Height (H) : 4.5m (HQT - Study)Center : 4.5/2=2.25m

H/B

B)

Ratio :A/B : 7.6/2.4=3.2

Empirical methodEmpirical method -- Exemple : Large FarmExemple : Large Farmvehiclevehicle -- HQTHQT

May 13th 2008May 13th 2008CEA EMF WORKHOPCEA EMF WORKHOP10103.2

1.9

S/(

A/B

8.0

. . = .

With abacus :S/(A*B)= 8S=8(7.6*2.4)=146

5mA = S*E/300 (E: Electric field)E=(5mA*300)/146=10.3kV/m




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Calculation with EPRI to get 5 mA induced in a human body

Size of the Large Farm Vehicle :Length (A) : 7.6 mWidth (B) : 2.4m

Height (H) : 4.15m (CSA)Center : 4.15/2=2.08m

H/B

B)

Ratio :A/B : 7.6/2.4=3.2

Empirical methodEmpirical method -- Exemple : Large FarmExemple : Large Farmvehiclevehicle -- CSACSA

May 13th 2008May 13th 2008CEA EMF WORKHOPCEA EMF WORKHOP11113.2

1.9

S/(

A/B

7.0

. . = .

With abacus :S/(A*B)= 7S=8(7.6*2.4)=129

5mA = S*E/300 (E: Electric field)E=(5mA*300)/129=11.6kV/m




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Calculation of Electric FieldCalculation of Electric Field

The electric field is determined by these parameters :1. Voltage2. Distance between phases3. Diameter of conductors4. Number of conductors per bundle5. Presence of overhead ground wire6. Distance of conductors from the ground


Software available to calculate the electric field : CDEGS of SES (Package : MultiField - 38 k$ - Available on market) Coulomb (3D Electric Field Solver Used by IREQ - Available on

market) Expomag (In house software HQ)


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FAA TOWER - 735 kV /

Electro-mechanicals specifications 1 circuit Conductors

4 per bundles : 3.556 cm


s ances e ween

Voltage max 765 kV

Overhead ground wire Quantity : 2 : 1.27cm


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735 kV Electric Field

8

10

12

kV/m


Electric field 735 kV (FAA Tower) Conductors at rest

Heightof

Max. Elec. field: 10.3 kV/m Large Farm Vehicle


0

2

4

6

0 4 8 12 16 20 24 28 32 36

m

21.0 m

13.4 m

conductors

HQT ROW (80 m)< 2 kV/m

Max. Elec. field: 4.9 kV/m - Truck

Center of the ROW


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Boundary Element Method (BEM)Boundary Element Method (BEM)

Equivalent circuit of a truck near a power linesEquivalent circuit of a truck near a power lines


Human body

Represented by a 1 k

Isc = 5 mA

Modelizationdone by IREQ(Alain Turgeon)


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BEM ExampleBEM Example Truck parallel to the lineTruck parallel to the line

Capacitive induction simulation for a truck located at 17 metersof the center line and parallel to conductors

735 kV with FAA towers

4

4.5

5kV/m

17 m

Height of conductors simulation :21 - 22 - 23 - 24 Height of conductors


0

0.5

1

1.5

2

2.5

3

3.5

-50 -40 -30 -20 -10 0 10 20 30 40 50

m

Example of an electric profile field

ROW

2,6 m

4,15 m

15,7 18,3

5 mA


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BEM ExampleBEM Example Truck parallelTruck parallel

Height of

conductorsCapacitances

Currentin a human

body

(m)Ca-t(pF)

Cb-t(pF)

Cc-t(pF)

Ct-g(pF)

ISC(ma)


21 3,03 15,8 43,4 1,46 5,9622 3,19 15,4 40,6 1,46 5,51

23 3,33 15,0 38,0 1,46 5,09

24 3,45 14,6 35,6 1,46 4,71

o m t t e

current in ahuman body

at 5 mAthe height ofconductors

must behigher than

23.2 m


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BEM ExempleBEM Exemple Truck perpendicular to lineTruck perpendicular to line

Capacitive induction simulation for a truck located perpendicular to conductors735 kV with FAA towers

5

6 kV/m

Height of conductors simulation :17 - 18 - 19 - 20 Height of conductors


0

1

2

3

4

-50 -40 -30 -20 -10 0 10 20 30 40 50

m

4,15 m

Example of an electric profile field

ROW

23 m

5,5 28,5

5 mA


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BEM ExampleBEM Example Truck perpendicularTruck perpendicular

Heightof conductors

CapacitancesCurrent

in a humanbody

(m)Ca-t(pF)

Cb-t(pF)

Cc-t(pF)

Ct-g(pF)

ISC(mA)


17 4,19 21,2 49,1 1,44 6,54

18 4,36 20,3 45,9 1,45 6,05

19 4,52 19,5 42,9 1,45 5,58

20 4,65 18,7 40,3 1,45 5,18

To limit thecurrent in ahuman bodyat 5 mA theheight of

conductorsmust be

higher than20.5 m


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Comparison results: Empirical versus BEMComparison results: Empirical versus BEM

Height of conductors

735 kV FAA towerEmpiricalMethod

(m)

BEMMethod

(m)


21 20.5 perpendicular23.2 parallel

HQT chose empirical method for it's in house standard

BEM method permitted HQT to check the accuracy of empiricalmethod


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Empirical methodEmpirical method HQT resultsHQT results

NominalVoltage

(kV)TOWER

MINIMUM HEIGHT OF CONDUCTORS(m)

TRUCK(Electric Field : 4.9 kV/m)

LARGE FARM VEHICULE(Electric Field : 10.3 kV/m)

735 FAA Single circuit 21 13.8


ou e c rcu t . < .

315 EFK Single circuit 10.6 7

230 DPD Double circuit 6.7


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ACKNOWLEDGEMENTSACKNOWLEDGEMENTS

Daniel Goulet, Ph. D.

Alain Turgeon, P. Eng. M. Sc. A.


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Calculation of Electrical Induction Near Power Lines