Overcurrent Backup Protection - Toshiba GRL100-701B Instruction Manual

2.5 Overcurrent Backup Protection

Inverse time and definite time overcurrent protections are provided for phase faults and earth
faults respectively.
Scheme logic
The scheme logic of the overcurrent backup protection is shown in Figures 2.5.1 and 2.5.2. The
overcurrent protection issues single-phase tripping signals in the operation of OC and OCI, and
issues a three-phase tripping signal BU-TRIP in the operation of EF or EFI element. Three-phase
tripping of OC and OCI is available by PLC signals OC_3PTP and OCI_3PTP. Tripping by each
element can be disabled by the scheme switches [OCBT], [OCIBT], [EFBT] and [EFIBT]. The
EF element issues an alarm for the backup trip for earth fault. The alarm can be disabled by the
scheme switch [EFBTAL].
The overcurrent backup protection can be blocked by the binary input signal BUT_BLOCK.
Tripping by each protection can be blocked by PLC signals OC_BLOCK, OCI_BLOCK,
EF_BLOCK and EFI_BLOCK. The OC and EF can trip instantaneously by PLC signals
OC_INST_TP and EF_INST_TP.
The OC and OCI protections can connect to the Fail-safe elements by PLC. Then the outputs of
Fail-safe elements are connected to OC-A_FS, OC-B_FS, OC-C_FS, OCI-A_FS, OCI-B_FS
and OCI-C_FS.
OC-A
OC-B
OC-C
OC_INST_TP
1633
[OCBT]
+
"ON"
OC_BLOCK
1589
OC-A_FS
1736
OC-B_FS
1737
OC-C_FS
1738
OCI-A
OCI-B
OCI-C
[OCIBT]
+
"ON"
OCI_BLOCK
1590
OCI-A_FS
1740
OCI-B_FS
1741
OCI-C_FS
1742
BUT_BLOCK
1550
TOC
65
t 0
66
t 0
67
t 0
0.00 – 10.00s
&
&
&
&
1
68
69
70
&
1
1
Figure 2.5.1 Overcurrent Backup Protection OC and OCI
 83 
459
≥1
&
460
≥1
&
461
≥1
&
≥ 1
OC_3PTP
1650
462
&
463
&
464
&
≥ 1
1651 OCI_3PTP
6 F 2 S 0 8 5 0
OC-A TRIP
OC-A TP
≥1
OC-B TRIP
OC-B TP
≥1
OC-C TRIP
OC-C TP
≥1
113
OC_TRIP
&
OCI-A TRIP
OCI-A TP
≥1
OCI-B TRIP
OCI-B TP
≥1
OCI-C TRIP
OCI-C TP
≥1
114
OCI_TRIP
&