study of electromagnetic interference on distribution ... of electromagnetic interference on...

Study of Electromagnetic Interference on Distribution Conductors

from Parallel Transmission Line and Practical Mitigation Solutions

Mike Shen, PEng, MASc, SMIEEE

2014 IEEE PES T&D Conference

Chicago, IL, USA

1

Acknowledgement

• Appreciate the opportunity of working on NextEra Wind Farm project.

• Appreciate my co-authors, Shilpa Shah and Ramin Eftekhari, for their contributions.

2

Outline

• Introduction

• Basics of Electric and Magnetic Fields

• Joint-use Transmission Line and Distribution Line

• Induced Voltage on Distribution Neutral from Overbuilt Transmission Line

• Different Mitigation Solutions

• Summary

3

Introduction

• Renewable energy resources are increasingly built at remote rural areas.

• Developers prefer to share the ROW of existing transmission or Distribution lines and route their HV tap line along the existing ROW.

• Excessive induced voltage and current on distribution neutral and phase conductors may occur during normal operation, fault, and transient conditions of the transmission system.

4

Cont.

• Electromagnetic Interference from transmission line includes magnetic induction effect and electrostatic effect.

5

Magnetic induction

Electrostaticinduction

HV line MV or LV line

Line current

Couplingcapacitor

Basics of Electric Fields

• Point charge 𝑄 and Electric field 𝐸

• Line charges and Electric field 𝐸

• A long single phase ac transmission line and Electric field 𝐸

6

Cont.

• Vector addition of electric fields under a three-phase transmission line

7

θ1

A B C

r1 r2 r3

θ2 θ3

EA(t)EB(t)

EC(t)

P

Cont.

• Electric potential 𝑉 and the electric field 𝐸

8

Basics of Magnetic Field

• A short section current carrying wire

• A long current carrying wire

• A long single phase ac transmission line

9

Cont.

• Vector addition of magnetic fields under a three-phase transmission line

10

θ1

A B C

r1 r2 r3

θ2 θ3

HA(t)

HB(t)

HC(t)P

I (out) I I

Cont.

• Changing magnetic field and the induction voltage

11

Loop

BV

E

Joint-use Transmission

Line and Distribution Line

12

Induced Voltage from Electric Field

• Electric field under TL Phase A to ground

13

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16

Tran

sve

rse

vo

ltag

e (

kV)

Seperation distance (m)

• Voltage induced on the ungrounded neutral conductor

Cont.

• Neutral conductor is 12 m from the lowest TL phase conductor.

– Ungrounded -> 486 V

– Single point grounded -> 0.3 V

– Multi point grounded -> 0.06 V

14

Induced Voltage from Magnetic Field

• Magnetic field under TL Phase A to ground

15

• Voltage induced on the ungrounded neutral conductor

0

50

100

150

200

250

300

350

400

450

500

0 2 4 6 8 10 12 14 16

Lon

git

ud

ina

l v

olt

ag

e (

V)

Seperation distance (m)

Cont.

• Neutral conductor is 12 m from the lowest TL phase conductor.

– Ungrounded -> 60.0 V

– Single point grounded -> 60.0 V

– Multi point grounded -> 14.8 V

16

Different Mitigation Solutions

• 25 ohm ground resistance

• 10 ohm ground resistance

17

0

2

4

6

8

10

12

14

16

-3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000

Ind

uce

d v

olt

ag

e (

V)

Distribution length (m)

0

1

2

3

4

5

6

7

8

9

10

-3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000

Ind

uce

d v

olt

age

(V

)

Distribution distance (m)

Cont.

• Bury 1 km 4/0 bare copper conductor on each end of DL

• Balancing of TL phase conductor geometry

18

0

1

2

3

4

5

6

7

-3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000

Ind

uce

d v

olt

ag

e (

V)

Distribution length (m)

0

0.01

0.02

0.03

0.04

0.05

0.06

-3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 3000

Ind

uce

d v

olt

age

(V)

Distribution length (m)

Cont.

• T/L Transposition

– Every 1000m

– Every 100m

19

0

1

2

3

4

5

6

7

8

-3000 -2000 -1000 0 1000 2000 3000

Ind

uce

d v

olt

age

alo

ng

neu

tral

(V

)

Distribution line length (m)

0.4

0.41

0.42

0.43

0.44

0.45

0.46

0.47

0.48

0.49

0.5

-3000 -2000 -1000 0 1000 2000 3000

Ind

uce

d v

olt

ag

e (

V)

Distribution line length (m)

Cont.

• Increase the separation distance between distribution neutral and transmission line.

• Convert overhead distribution system to shielded power cable.

20

Thank you for your attention

Questions?

21