9.4.6.5 Shot initiation from protection start signal
In it simplest, all auto-reclose shots are initiated by protection trips. As a result, all
trip times in the sequence are the same. This is why using protection trips may not
be the optimal solution. Using protection start signals instead of protection trips for
initiating shots shortens the trip times.
Example 1
When a two-shot-sequence is used, the start information from the protection
function is routed to the DEL_INIT 2 input and the operate information to the
INIT_2 input. The following conditions have to apply:
• protection operate time = 0.5s
• Str 2 delay shot 1 = 0.05s
• Str 2 delay shot 2 = 60s
• Str 2 delay shot 3 = 60s
Operation in a permanent fault:
1. Protection starts and activates the DEL_INIT 2 input.
2. After 0.05 seconds, the first autoreclose shot is initiated. The function opens
the circuit breaker: the OPEN_CB output activates. The total trip time is the
protection start delay + 0.05 seconds + the time it takes to open the circuit breaker.
3. After the first shot, the circuit breaker is reclosed and the protection starts again.
4. Because the delay of the second shot is 60 seconds, the protection is faster and
trips after the set operation time, activating the INIT 2 input. The second
shot is initiated.
5. After the second shot, the circuit breaker is reclosed and the protection starts
again.
6. Because the delay of the second shot is 60 seconds, the protection is faster and
trips after the set operation time. No further shots are programmed after the
final trip. The function is in lockout and the sequence is considered unsuccessful.
Example 2
The delays can be used also for fast final trip. The conditions are the same as in
Example 1, with the exception of Str 2 delay shot 3 = 0.10 seconds.
The operation in a permanent fault is the same as in Example 1, except that after
the second shot when the protection starts again, Str 2 delay shot 3 elapses before
the protection operate time and the final trip follows. The total trip time is the
protection start delay + 0.10 seconds + the time it takes to open the circuit breaker.
9.4.6.6 Fast trip in Switch on to fault
The Str _ delay shot 4 parameter delays can also be used to achieve a fast and
accelerated trip with SOTF. This is done by setting the Fourth delay in SOTF
Section 9 1YHT530004D05 D
Control functions
720 615 series
Technical Manual
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