Siemens 7UT51

7UT51 v3
Bus Differential Protection (87B)
6
PRIM-2330C 87
Bus Differential Protection (87B) Occurrence LCD Abbreviation Event Oper Fault In/Out
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
-
event
for the new status. The normal operational status is set in
Address 1801.
87Diff OFF
87Diff BLOCK
87Diff ACTIVE
5615
5616
5617
C
C
C
G
G
G
S
S
S
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.
>87Diff BLOCK
>87DiffBlkTrip
5603
5605
I
I
S
S
If an open CT
-
circuit is detected, the 87B protection of the
corresponding phase will be temporarily turned off.
87Blk CTPhA
87Blk CTPhB
87Blk CTPhC
5662
5663
5664
C
C
C
G
G
G
S
S
S
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
rest
) exceeds four times rated nominal current (I
n
), the 87B
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.
87Diff GenFlt 5631 CG S T
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.
87Diff PhA
87Diff PhB
87Diff PhC
5681
5682
5683
C
C
C
S
S
S
Time Delay Before Trip
If an 87B pickup occurs, the corresponding time
-
delay
-
before
-
trip
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.
87Diff Pickup 5621 C S T
Restraint
If the motion of the operating point suggests that a high
-
current
fault outside the protected zone is saturating the CTs, the event is
reported for each phase. The corresponding going
-
event occurs
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).
87Blk SatPhA
87Blk SatPhB
87Blk SatPhC
5651
5652
5653
C
C
C
G
G
G
S
S
S