Blocking By Frequency Variance; Time Delays - Siemens 7UT51 Instruction Manual

7UT51 v3
7ULS
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Figure 4.11 Higher Harmonic Restraint Characteristic
4.8 Blocking by Frequency
Variance
If the system frequency varies too far from the rated
nominal frequency, the transformer differential
protection will be blocked, as illustrated in Figure 4.12.
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Figure 4.12 Blocking of Transformer Differential Protection
(87T and 87HS) by Variance from Nominal
System Frequency.
PRIM-2330C
Transformer Differential Protection (87T and 87HS)
4.9
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If an 87T pickup occurs, and the 87T function is not
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being restrained, the function will immediately trip
unless a time delay has been set in Address 1625. If
an 87HS pick up occurs, the 87HS function will
immediately trip unless a time delay has been set in
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Address 1626 (restraint does not apply to the 87HS
7ULS
function).
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To ensure that the trip state lasts long enough for the
circuit breaker to operate, the trip state can be
prolonged by a reset time delay that is set in
Address 1627.
All times are pure delay times which do not include the
inherent operating time.
%ORFN If a trip occurs, the contacts and LEDs marshalled to
7 7ULS
the event will remain activated until the corresponding
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function (87T or 87HS) drops out.

Time Delays

1625 87 DELAY
Time delay between pickup and trip for 87
differential protection (in addition to the
inherent operating time of the relay).
60.00 s, or ∞
–
Range: 0.00
Default: 0.00 s
1626 87HS DELAY
Time delay between pickup and trip for
87HS differential protection (in addition to
the inherent operating time of the relay).
60.00 s, or ∞
–
Range: 0.00
Default: 0.00 s
-
1627 T RESET
Additional time to remain in trip state of the 87 and/or
87HS functions, after the trip signal has disappeared
(in addition to the inherent reset time of the relay).
–
Range: 0.00 60.00 s
Default: 0.10 s
4
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