Toshiba GR200 Series Instruction Manual page 135

Line differential protection ied

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ZS-DirRθ(R abscissa)

Figure 2.10-22 Z1S Quad element close-up fault (Offset action)

Operation of ZS for earth and multi-phase-faults

ZS can operate for any of the following faults: a phase-to-phase fault, phase-to-phase ground

fault, and a fault evolving into a multi-phase fault. To strengthen dependability in detecting

the multi-phase fault, it is possible to add the judgement of fault phase identifier. The fault

phase identifier consists of ZG elements. The judgement condition will be added when On is

set for setting [Z*S-MSDET]†. In order not to add the judgement in ZS, the user can set Off for

the setting.

†Note: It is recommended to set [Z*S-MSDET]=On in the instantaneous main protection

element only. Since operating condition of Z*S elements is increased by setting

On, it is desirable to set Off in the backup protection easier to operate.

Special characteristic in ZG

Earth fault compensation (Zero sequence current compensation)

On the detection of an earth fault, ZG requires a compensation function that corrects

measuring errors caused by the earth return of zero-sequence current. By using the

compensation function, the positive-sequence impedance to the fault point can be determined

precisely by the reactance element in the faulted phase. For a double-circuit line, the zero-

sequence current from the adjacent line is introduced to compensate for influences from zero-

sequence mutual coupling. Considering a case where the angle of the positive-sequence

impedance and the zero-sequence impedance differs, the distance protection function carries

out zero-sequence current compensation vectorially. We can see this case commonly in cable

Offset Quadrilateral characteristic during close-up fault

Static Quadrilateral characteristic

ZS-DirXθ(X ordinate)

6F2S1914 (0.49)

GRL200 (Soft 033 & 037)

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