Siemens 7UT51 Instruction Manual page 76

5
Motor or Generator Differential Protection (87M/G)
Motor or Generator Differential Protection (87M/G) Occurrence
Time Delay Before Trip
If an 87M/G pickup occurs, the corresponding
- - -
time delay before trip timer will start (see Section 5.7 on page 75).
This event will not occur if the time delay setting is zero. Outputs
marshalled to this event will remain actuated until the time delay
expires (Address 1725).
Restraint
If the motion of the operating point suggests that a high
fault outside the protected zone is saturating the CTs, the event is
reported for each phase. The corresponding going
when the duration timer (Address 1717) runs out, or the 87M/G
function detects that an internal fault is also occurring (see
Section 5.5 on page 74).
Trip and Reset
Any 87M/G trip event will also cause event 5671 to occur. With the
default marshalling, event 5671 will actuate all the trip contacts,
signal contact 2, and (as for the general trip of any protection
function) signal contact 1. Outputs actuated by 87M/G trip events
will remain actuated until the 87M/G function resets (the same
conditions for dropout, event 5631G), plus the additional reset time
(Address 1727).
The 87M/G function will trip if and when ALL the following are true:
• an 87M/G pickup has occurred, and it has not yet dropped out
or already caused a trip,
-
• the 87M/G time before
Address 1725) has expired,
• any restraint has ended,
There are separate 87M/G trip events for each phase, and one
(event 5691) that reports the 87M/G trip of any phase. With the
default marshalling, event 5691 will light and latch LED 2 and (as
for any protection function trip event) LED 1.
If an 87M/G trip event occurs, the values of the differential currents
and restraining currents for each phase at the time of the trip are
recorded in the then open fault log.
Configuration Events
-
If the motor/generator description settings are changed, the
-
current matching factors for the phase currents are recalculated
and reported.
Table 5.1 Events Related to Differential Protection of a Motor or Generator (87M/G)
76
-
event occurs
-
trip time delay (if one is set
LCD Abbreviation
87Diff Pickup
-
current 87Blk SatPhA
87Blk SatPhB
87Blk SatPhC
87Diff GenTrip
87Diff TripPhA
87Diff TripPhB
87Diff TripPhC
87 Trip
Diff Ia= value
Diff Ib= value
Diff Ic= value
Rest Ia= value
Rest Ib= value
Rest Ic= value
k CT 1= factor
k CT 2= factor
7UT51 v3
Event Oper Fault In/Out
5621 C
5651 C G
5652
C G
5653
C G
5671
5672
5673
5674
5691
C
5701 C
5702
C
5703
C
5704
C
5705
C
5706
C
5713 C
5714
C
PRIM-2330C
S T
S
S
S
S T
S T
S T
S T
S T