Toshiba GR200 Series Instruction Manual page 109

Line differential protection ied

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Stub protection with overcurrent relay (STUB-OC)

Figure 2.9-1 depicts that a one-and-a-half breaker (1.5CBs) arrangement with a transmission

line including a disconnector (DS). An area 'stub zone' is defined within two CBs and the DS,

which is expressed by hatching in the figure.

For the 1.5CB arrangement, a voltage transformer (VT) is generally installed along the

line GH. Figure 2.9-1 shows that the line GH is taken out of service because of the DS being

open; hence, a distance relay in the IED_G cannot detect a fault when a fault occurs in the

'stub' zone. This is because a faulted voltage cannot be measured correctly using the VT G .

Thereby, an overcurrent relay (OC) is provided to protect the 'stub' zone and the OC relay

operates speedy upon occurrence of the fault.

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The implementation of such features is dependent upon the selection of hardware and

the configuration of functions. Several IED models do not support certain features. To

determine whether a particular feature has been implemented within an IED, identify the IED

ordering number; and check the order number at the "G&T position" referring to the

comparison table below. For more information, see

Table 2.9-1 Comparative table in respective ordering numbers

✓: Applicable

Figure 2.9-1 Fault occurred in stub zone

Relay function/ features

OC relay for stub protection

NA: Not applicable

Appendix: Ordering

6F2S1914 (0.49)

Ordering No. at "G&T"

GRL200 (Soft 033 & 037)

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