Title: Guide for the Application of Rogowski Coils used for Protective Relaying Purposes

Chair: Ljubomir KojovicVice Chair: Veselin Skendzic

Established: January 2004

Assignment - This Guide establishes criteria and requirements for application of Rogowski Coilsused for protective relaying in electric power systems. The selection and application of RCs forthe more common protection schemes are addressed.

Purpose - This document provides a guide for application of Rogowski Coils used for protectiverelaying in electric power systems. It is intended to assist the relay application engineer in thecorrect selection and application of RCs for protective relaying purposes. It provides requirementsrelevant to the performance, operation, testing, safety considerations, and maintenance ofRogowski Coil based current transducers.

This guide applies to all types of Rogowski Coils used for Protective Relaying Purposes.

Volta

ge

Current

Operating pointfor CTs

Saturation voltage

Linear region

Non-Linear region

Operating pointfor voltage transformers

Rogowski Coil V-I Characteristic

Conventional Current Transformer

Rogowski CoilIp Ls

Zbv(t)

MRs

Cs

Low Impedance

High Impedance

∑−=j

j tidtdMtv )]([)(

ip’ Rp Lp LsRs is

im

imr imx

LmRmZb

Rogowski Coil

10

100

1000

0.01 0.1 1 10 100Current [A]

Volta

ge [V

]1200/5 A CT

0 0.05 0.1 0.15 0.2 0.25-15

-10

-5

0

5

10

15

20

25

30

Cur

rent

[kA

]Secondary Current (referred to the primary)

Primary Current

Laboratory Test #346

Time [s]

1200/5 A CT

0 0.02 0.04 0.06 0.08 0.1

Cur

rent

[kA

]

Time [s]

1200/5 A CTsecondarycurrent

Primary current

-20

-10

0

10

20

30

40

-20

-10

0

10

20

0 0.02 0.04 0.06 0.08 0.1

Cur

rent

[kA

]

Time [s]

Rogowski coilnon-integratedsecondary signal Primary current

0 0.02 0.04 0.06 0.08 0.1

-20

-10

0

10

20

30

40

Cur

rent

[kA

]

Time [s]

Rogowski coil non-integratedsecondarysignal

Primary current

0 0.02 0.04 0.06 0.08 0.1

-20

-10

0

10

20

30

40

Cur

rent

[kA

]

Time [s]

Rogowski coil integratedsecondarysignal

Primary current

Intelligent Substations - Hitachi

ConventionalInstrument

Transformers

Low PowerInstrument

Transformers

GCB: gas circuit breakerCT: current transformerPT: potential transformer

Integrated High Voltage Switchgear(circuit breaker, isolator, groundingswitch, current and voltage sensors) inone gas insulated compartment

220 kV

ABB Combi Sensor Up to 60% less space requirement

PASS

Rogowski Electronic Current Transformer applied to a 550 kV Gas Insulated Substation (AREVA)

Trench Electric

Class 0.2 0.5 3P Voltage 6 - 36 kV Ferroresonance free

Cooper Power Systems

Differential Protection of

90 MVA, 34.5/1 kV EAF Transformers

26 in

9 in

Scale ±7.5 kApeak

Scale ±300 kApeak

Operate Signals Mismatch between primary and secondary currents is less than 1%

Trip Signals

95 kApeak

Restraint Signals

Primary Currents

Secondary Currents

A-phaseB-phaseC-phase

Cooper Power SystemsMobile Substations (primary side RCs)

Mobile Substations (secondary side RCs)

ABC

Ia Ib Ic Ir

Protective Relay

I1 I2

I1 I2

Protective Relay

Transformeror

Generator

i(t)

Rogowski Coil

filters andA/D

powersupply

Rogowski coil Conventional CT

E/O

O/E reception andinterface to relays

ground level

HV levelfiber opticalcable

Rogowski coil

Fiber OpticalCable

A/D

DataPower

Converter

LaserDiode

DataReceiver

PowerSupply

D/AConverter

DSP

AnalogOutput

DigitalOutput

RemoteUnit

GroundUnit

Fiber-OpticalCables

HV Linei(t)

GroundUnit

RC andRemote

Unit

Remote Unit

RC

Power DataFiber-Optical Cables

Ground Unit Junction

Box

HV Potential

Photonic Power Systems, Inc.