Chapter 7) 7SR23 DAD Applications Guide
©2013 Siemens Protection Devices Limited
Chapter 7 Page 28 of 42
5.3
Sustained Fault (87/50SFM)
The 7SR23 is connected to measure unbalance current. The sustained flow of fault current after a differential
protection operation indicates either a failed CB condition or fault in a protection ‘blind spot’, see Figure 5-4.
Where one of the circuit breakers fails to trip the relay cannot inherently identify which CB has failed, it can
measure continued flow of differential current only.
ZONE 1
CCT
PROT
Bus 1
CCT
PROT
Bus 2
ZONE 1
CCT
PROT
Bus 1
CCT
PROT
Bus 2
a) Busbar 1 Fault
b) Busbar 1 Blind
Spot Fault
ZONE 2
ZONE 2
ZONE 1
CCT
PROT
Bus 1
CCT
PROT
Bus 2
ZONE 1
CCT
PROT
Bus 1
CCT
PROT
Bus 2
c) Feeder Blind
Spot Fault
d) Busbar 2 Blind
Spot Fault
ZONE 2
ZONE 2
Figure 5-4
Position of Uncleared Faults
The SFM feature used in conjunction with the Circuit Position Monitor can provide the following information.
CB Status Monitoring
One or More CBs Closed
All CBs Open
From fig. 3.1
CTs Overlapping the CBs
1) Uncleared Fault Event
2) Failed CB Identified
1) Uncleared Fault Event
2) Blind Spot Fault Event – F4 or F6
From
Figure 3-2
CTs on ‘Circuit’ Side of CBs
1) Uncleared Fault Event
2) Failed CB Identified
1) Uncleared Fault Event
2) Blind Spot Fault Event – F3 or F4
From
Figure 3-4
CTs on ‘Busbar’ Side of CBs
1) Uncleared Fault Event
2) Failed CB Identified
1) Uncleared Fault Event
2) Blind Spot Fault Event – F3
Summary of Contents for 7SR23 DAD
Page 1: ...Answers for energy 7SR23 DAD High Impedance Protection Relay Reyrolle Protection Devices ...
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Page 4: ...7SR23 DAD Contents 2013 Siemens Protection Devices Limited ...
Page 60: ...Chapter 3 7SR23 DAD Performance Specification 2013 Siemens Protection Devices Limited ...
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