Siemens 7UT51 Instruction Manual page 87

7UT51 v3
Bus Differential Protection (87B) Occurrence
Change in Operational Status
When the operational status of the 87B function changes, a
-
going event for the old status occurs followed by a coming
for the new status. The normal operational status is set in
Address 1801.
A binary input can temporarily change the operational status of the
function (see Section 13.2 on page 126). Any outputs marshalled
to these events will remain actuated for as long as the binary input
remains actuated.
-
If an open CT circuit is detected, the 87B protection of the
corresponding phase will be temporarily turned off.
Pickup and Dropout
If the operating point of any phase rises above 85% of the
threshold of the pickup characteristic, or if the restraint current
(I ) exceeds four times rated nominal current (I
rest
function will pickup (event 5631C). If no fault log is already open, a
new one will open.
If the operating point for all phases remains below 70% of the
threshold of the pickup characteristic for two full cycles, the 87B
function will dropout (event 5631G). See Section 6.4 on page 83.
-
An 87B phase pickup occurs if the operating point of a phase rises
above the pickup characteristic. Outputs marshalled to these
events will remain actuated until dropout of the corresponding
phase.
Time Delay Before Trip
If an 87B pickup occurs, the corresponding time
timer will start (see Section 6.7 on page 86). 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.
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 1817) runs out, or the 87M
function detects that an internal fault is also occurring (see
Section 6.5 on page 85).
PRIM-2330C
LCD Abbreviation
87Diff OFF
87Diff BLOCK
-
event
87Diff ACTIVE
>87Diff BLOCK
>87DiffBlkTrip
87Blk CTPhA
87Blk CTPhB
87Blk CTPhC
87Diff GenFlt
), the 87B
n
87Diff PhA
87Diff PhB
87Diff PhC
- - -
delay before trip 87Diff Pickup
-
current 87Blk SatPhA
87Blk SatPhB
87Blk SatPhC
-
event occurs
Bus Differential Protection (87B)
Event Oper
5615 C G
5616
C G
5617
C G
5603
5605
5662 C G
5663
C G
5664
C G
5631
5681
5682
5683
5621
5651
5652
5653
6
Fault In/Out
S
S
S
I S
I S
S
S
S
C G S T
C S
C S
C S
C S T
C G S
C G S
C G S
87