
Application Guide
P12y/EN AP/D32
MiCOM P125/P126 & P127
Page 55/74
5.11.1
Circuit Breaker Failure Protection Mechanism
The CB failure protection included in both MiCOM P126 & P127 relays is performed as
follows.
The
tBF
timer is initiated when a trip order is issued through the logic output
RL1
or by an
assigned digital input (start tBFl).
The trip order can be emitted from a protection element or auxiliary function associated to
the logic output RL1, the logic digital input can be energised from an external device.
In case of command from external device the start of the tBF is active by the change of
status of the relevant digital input (edge), when the tBF is expired a CBF signal is issued.
The tBF is reset when the relevant I< BF is verified for each phase. ((Ia< && Ib< &&
Ic<)==TRUE)
In case of a trip by a RL1 the MiCOM P126 & P127 relays monitor the current signal of each
phase and they compare each phase current signal with the undercurrent I< BF threshold
settable its menu. If the undercurrent I<BF is FALSE ((Ia< && Ib< && Ic<)==FALSE) when
the tBF timer is expired a CBF signal is issued, if it is TRUE (((Ia< && Ib< && Ic<)==TRUE)
the tBF timer is reset. A TRUE condition of the I<BF resets the tBF always.
In the CB fail menu it is also possible to choose if to lock the instantaneous I> and Ie>
thresholds when a CBF signal is emitted. This one allows more flexibility in the fault
localisation and isolation.
CB Fail Alarm
Any Trip
CBF Ia<
CBF Ib<
CBF Ic<
CB Fail Enabled
External CBF
Initiate
tBF
1
S
R
Q
P0428ENa
5.11.2
Breaker Fail Settings
A typical timer setting used with a 2 ½ cycle circuit breaker is around 150 ms.
The phase undercurrent settings (I<) must be set less than load current, to ensure that I<
operation indicates that the circuit breaker pole is open. A typical setting for overhead line or
cable circuits is 20% In, with 5% In common for generator circuit breaker CBF.
Содержание MiCOM P125
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Страница 5: ...Pxxxx EN SS B11 SAFETY SECTION...
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Страница 17: ...Getting Started P12y EN GS D32 MiCOM P125 P126 P127 GETTING STARTED...
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Страница 79: ...User Guide P12y EN FT D32 MiCOM P125 P126 P127 USER GUIDE...
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Страница 167: ...Technical Data P12y EN TD D32 MiCOM P125 P126 P127 TECHNICAL DATA AND CHARACTERISTIC CURVES...
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Страница 273: ...Commissioning and Maintenance P12y EN CM C22 MiCOM P125 P126 P127 COMMISSIONING AND MAINTENANCE GUIDE...
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Страница 299: ...Connections and Wiring Diagrams P12y EN CO C22 MiCOM P125 P126 P127 CONNECTIONS AND WIRING DIAGRAMS...
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Страница 311: ...Commissioning Test and Record Sheet P12y EN RS D32 MiCOM P125 P126 P127 COMMISSIONING TEST AND RECORD SHEET...
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