Toshiba GR200 Series - 2.9 Stub protection with overcurrent relay (STUB-OC)

6F2S1914 (0.49)
GRL200 (Soft 033 & 037)
- 86 -
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.
CT2
G
CT1
G
Terminal-G
Fault
IED_G
IED_H
CT2
H
CT1
H
Terminal-H
Line GH
Line
DS
CB
CB
CB
Line
VT
G
CB
VT
H
CB
CB
Figure 2.9-1 Fault occurred in stub zone
(2.44.1)
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Note: 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 Appendix: Ordering .
Table 2.9-1 Comparative table in respective ordering numbers
Section
feature
Relay function/ features
Ordering No. at “G&T”
33
37
–
STUB-OC
OC relay for stub protection
✓
✓
✓: Applicable NA: Not applicable