Testing of Directional Relays Made Easy.pdf

7/27/2019 Testing of Directional Relays Made Easy.pdf

1/19

Alexander Dierks, Gawie Pretorius,Alexander Dierks, Gawie Pretorius,

Alectrix (Pty) Ltd, South AfricaAlectrix (Pty) Ltd, South Africa

Testing of DirectionalTesting of Directional OvercurrentOvercurrent RelaysRelaysMade EasyMade Easy

with XRIO,with XRIO, LinkToXRIOLinkToXRIO and OCC Test Moduleand OCC Test Module

Automation TechnologyAutomation Technology


2/19

Slide 2 Alectrix 2006

In a solidly earthed, meshed network currents in a linecan flow in both directions.

During fault conditions the response of overcurrent(O/C) and earthfault (E/F) relays needs to depend onthe direction of current flow.

Directional control is achieved by comparing the faultcurrent (operating quantity) with a polarizing voltage

(stabilizing quantity).

The polarizing voltage is calculated or measureddirectly from the voltage transformers (VT).

Why Directional O/C and E/F Relays?Why Directional O/C and E/F Relays?


3/19


Methods for Directional ControlMethods for Directional Control

Fault Voltage Polarised (E/F)Fault Voltage Polarised (E/F)

Zero Sequence Voltage Polarised (E/F)Zero Sequence Voltage Polarised (E/F)

Positive Sequence Voltage Polarised (O/C)Positive Sequence Voltage Polarised (O/C)

WattmetricWattmetric (O/C)(O/C)

QuadratureQuadrature Voltage Polarised (O/C & E/F)Voltage Polarised (O/C & E/F)

Negative Sequence Voltage Polarised (O/C & E/F)Negative Sequence Voltage Polarised (O/C & E/F)

(not covered in this application example)(not covered in this application example)


4/19


Fault Voltage PolarisedFault Voltage Polarised

The directional element measures the phase angle between fault current and

fault voltage.

Angle (1) is negative for typical forward faults.

For close-in faults this method is unreliable, as for small fault voltages no

reliable phase angle measurement is possible.

Directional Characteristic: - 45 90

Forward FaultReverse Fault


5/19


3V3V00 PolarisedPolarised

The directional element measures the angle between fault current and zerosequence voltage (3V0).

Angle (1) is positive and greater 90 for typical forward faults.

Sometimes -3V0

(i.e. negative of 3V0) is used.

Angle (2) is negative for typical forward faults.

3V0 is directly measured from an open delta connected VT or internallycalculated from the phase voltages (3V0 = VA+VB+VC).


6/19


Positive Sequence VoltagePositive Sequence Voltage PolarisedPolarised

The directional element measures the angle between positive sequence

current (I1) and positive sequence voltage (V1).

Angle is negative for typical forward faults.

V1 und I1 are calculated.

3 Phase Fault A-B Fault


7/19


Wattmetric MethodWattmetric Method

Forward direction is defined in a power vector diagram.

Operation is similar to the fault voltage polarised method.

Directional elements measures the angle between apparentpower S and active power P.

Angle (1) is positive for a typical forward fault.


8/19


Quadrature VoltageQuadrature Voltage PolarisedPolarised

The quadrature voltage is chosen such that it can be easily

measured in spite of the fault.

The directional element measures the phase angle between thefault current and the quadrature voltage as per the table below.

Each phase is measured independently.

IICC

IIBB

IIAA

Fault CurrentFault Current

VVAA--BBCC

VVCC--AA

BB

VVBB--CCAA

Polarising VoltagePolarising VoltageFaulted PhaseFaulted Phase


9/19



Example 1: A-N Fault:

The A phase directional element measures the phase angle between IAAand VVBB--CC.

AA = +45 for a typical forward fault.


10/19



Example 2: A-B Fault:

Phase A directional element measures the phase angle between IAA

and VVBB--CC. AA = +45 for a typical forward fault.

Phase B directional element measures the phase angle between IBBand VVCC--AA.

BB = +45 for a typical forward fault.

Phase A Phase B


11/19


QuadratureQuadrature VoltageVoltage PolarisedPolarised

The relay trips if phase A OR phase B element is picked-up.

To determine the resulting directional operating characteristic, the vectordiagram of phase B has to be superimposed onto the vector diagram of

phase A. The operating characteristic of phase B has to be inverted, i.e. A minus B.

Resultant directional operating characteristic is 240, from 225 to 105(not 180).

Phase A - B


12/19


How can such relays be tested?How can such relays be tested?

It is a complex task!It is a complex task!

Good understanding of directional relays and their methods isGood understanding of directional relays and their methods isrequired.required.

Time consuming task to set up test:Time consuming task to set up test:

Draw vector diagram and determine the operating area.Draw vector diagram and determine the operating area.

Determine fault currents and polarizing voltages in amplitudeDetermine fault currents and polarizing voltages in amplitudeand phase angle.and phase angle.

The Overcurrent module provides limited directional testingThe Overcurrent module provides limited directional testingfunctionality, i.e. Go / Nofunctionality, i.e. Go / No--Go test.Go test.

The pickThe pick--up of the directional operating characteristic cannot beup of the directional operating characteristic cannot betested.tested.


13/19


The Solution!The Solution!

XRIO ConverterXRIO Converter A function specific user interface / entry dialogue for directioA function specific user interface / entry dialogue for directional overnal over--

current relays.current relays.

O/C & E/F parameters can be entered.O/C & E/F parameters can be entered. Method of directional control, maximum torque angleMethod of directional control, maximum torque angle , operating angle, operating angle

For all fault types helper parameters for each directional charaFor all fault types helper parameters for each directional characteristic arecteristic arecalculated.calculated.

LinkToXRIOLinkToXRIO TechnologyTechnology Link any test parameter of a test module to any of the functionLink any test parameter of a test module to any of the function specificspecific

parameters defined or calculated in the XRIO converter.parameters defined or calculated in the XRIO converter.

Control Center Document (OCC)Control Center Document (OCC) Incorporates the XRIO converter andIncorporates the XRIO converter and LinkToXRIOLinkToXRIO technology.technology.

Perform a fully automated directional operating characteristic tPerform a fully automated directional operating characteristic test.est.

Test module automation allows the automatic display of the direcTest module automation allows the automatic display of the directionaltionaloperating characteristic.operating characteristic.


14/19


XRIO ConverterXRIO Converter


15/19


LinkToXRIOLinkToXRIO + + 15

t > * 2I > * 2

+

+ - 15


16/19


OMICRON ControlOMICRON Control CenterCenterDocumentDocument


17/19


Directional CharacteristicDirectional Characteristic

After completion of the test procedure select:After completion of the test procedure select:

Test | User command | Update Directional CharacteristicsTest | User command | Update Directional Characteristics


18/19



19/19


Summary of BenefitsSummary of Benefits

You donYou dont need to scratch your head everyt need to scratch your head every

time you test a directional relay!time you test a directional relay!

NoNo prepre--processingprocessing or relay parameters isor relay parameters is

necessary.necessary.

Error free testing of directional characteristicError free testing of directional characteristic

SingleSingle--clickclick solutionsolution

Time SavingTime Saving

Ease of UseEase of Use

Documents

Testing of Directional Relays Made Easy.pdf