Busbar Trip (87Bb)/Central Breaker Fail Backtrip Confirmation (50Bf) - GE P741 Technical Manual

P74x/EN ST/Na7
(ST) 4-18
BUSBAR OPTION
SEF Block Alarm
Options for Sensitive Differential Earth Fault (SEF) Protection (87BB/N) only are as follow:
Enabled:
If the Sensitive Differential Earth Fault Protection (87BB/N) is blocked, the associated alarm
is raised and is flashing on the front panel of the P741.
Disabled:
If the Sensitive Differential Earth Fault Protection (87BB/N) is blocked, the associated alarm
is not raised and is not present on the front panel of the P741.
Confirm Reset PU
Enables or disables the PU error auto- reset.
ST
3ph Block-Alarm
When enabled, an alarm is displayed when one zone is blocked by a Differential Busbar
Protection function (87BB).
Delay Trip Status
Activate or deactivate a time delay before 87BB (phase differential busbar protection) trip.
When activated, the settable delay time (using 'Delay Trip Timer' menu) is used to confirm
the fault or to clear the fault before zone trip.
Delay Trip Timer
'Delay Trip Timer' sets the delay time to confirm a phase differential busbar protection
(87BB) trip when 'Delay Trip Status' is enabled. This delay time must be shorter than the
time delay of phase circuitry fault monitoring ('DIFF BUSBAR PROT / ID>1 Alarm timer'
menu).
Diff Display Min
Sets a minimum threshold to display a differential current ('Measurement' column). When
the differential current is less than this threshold on the 3 phases, the displayed current is
forced to 0.
1.2.3 Busbar Trip (87BB) or Central Breaker Fail BackTrip Confirmation (50BF) ("BB Trip Confirm"
menu – P742/P743)
The peripheral units can be enabled to control the trip command issue by the central unit
(87BB or 50BF) if a local fault threshold, either phase or earth (i.e. I>BB or I
exceeded.
This criterion provides additional scheme stability. Should the command proceed, and a trip
be issued to the circuit breaker this element can confirm the evolution of a circuit breaker
failure condition. If the element is still operated after a set time delay a breaker failure
condition must exist.
BB Trip Confirm
I>BB Current Set
Setting for the minimum pickup phase fault element trip authorization
I >BB Current
N
Setting for the minimum pickup Earth fault element trip authorization
Menu Text Default Setting
Enabled
Enabled
Enabled
Disabled
0.1s
0A
Menu Text Default Setting
1.20*I
n
0.20*I
n
Note: I is the CT nominal current.
n
MiCOM P741, P742, P743
Setting Range
Min. Max.
Enabled / Disabled
Enabled / Disabled
Enabled / Disabled
Enabled / Disabled
50ms 5s
0A 500A
Setting Range
Min. Max.
0.05*I 4.00*I
n n
0.05*I 4.00*I
n n
Settings
Step Size
10ms
10A
>BB), is
N
Step Size
0.01*I
n
0.01*I
n