Toshiba GR200 Series Instruction Manual page 138

Line differential protection ied

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Figure 2.10-23 Earth fault compensation

The Zero-sequence Current Compensation function (ZPCC) controls the zero-sequence

compensation required as a consequence of the influence of the adjacent line in parallel line

applications.

When an earth fault occurs on the protected line, the ZPCC function will operate, in this

case parallel line compensation is performed to prevent under-reach caused by the mutual

zero-sequence current of the adjacent line.

When an earth fault occurs on the adjacent line, the ZPCC function does not operate,

compensation for the adjacent line is not performed to prevent overreach. The operating

condition of the ZPCC function is as follows:

Operation of ZG for earth-faults and multi-phase faults

ZG uses an EFL function for the detection of earth faults; hence, ZG will operate when the EFL

function operates. However, the operation of Z*G can be set to be either dependent or

independent of the operation of EFL; that is, On is set for the scheme switch [Z*G-EFL] for the

Z*G operation with EFL and Off is set for the scheme switch [Z*G-EFL] for the Z*G operation

without EFL.

There is a possibility that ZG even operates against a multi-phase fault. Because of the

effect of zero-phase compensation adjustment calculation, ZG elements tends to calculate

overreach (underreach) against a multi-phase fault when the direction of power flow is positive

(negative), it is recommended to make just ZS operate against the multi-phase fault.

ZG elements can be blocked by an operation of a multi-phase (2-phase or 3-phase) earth

fault detection by elements of ZG*COV as shown in scheme logics of the distance protection

element described later.

I 1 , I 2 , I 0

6F2S1914 (0.49)

GRL200 (Soft 033 & 037)

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