Siemens siprotec 7SA522 - Page 310

2 Functions
310
7SA522 Manual
C53000-G1176-C155-3
choice is made in address  S5(75,37. Set this parameter to <(6 if you
wish single-pole trip for the first stage, otherwise to 12.
If the breaker does not respond to this trip repetition, the adjacent circuit breakers are
tripped after T2 i.e., the circuit breakers of the busbar or of the concerned busbar
section and if necessary also the circuit breaker at the remote end unless the fault has
been cleared.
Separate delay times can be set
• for single- or three-pole trip repetition to the local feeder circuit breaker after a 1-
pole trip of the feeder protection 7SROH at address ,
• for three-pole trip repetition to the local feeder circuit breaker after 3-pole trip of the
feeder protection 7SROH (address ),
• for trip of the adjacent circuit breakers (busbar zone and remote end if applicable)
7 at address .
The delay times are set dependant on the maximum operating time of the feeder
circuit breaker and the reset time of the current detectors of the breaker failure protec-
tion, plus a safety margin which allows for any tolerance of the delay timers. Figure 2-
136 illustrates the timing of a typical breaker failure scenario. The dropout time for si-
nusoidal currents is ≤ 15 ms. If current transformer saturation is anticipated, the time
should be set to 25 ms.
Figure 2-136 Time sequence example for normal clearance of a fault, and with circuit breaker
failure, using two-stage breaker failure protection
Single-stage
Breaker Failure
Protection
With single-stage operation, the adjacent circuit breakers (i.e. the breakers of the
busbar zone and, if applicable, the breaker at the remote end) are tripped after a delay
time 7 (address ) following initiation, should the fault not have been cleared
within this time.
The timers 7SROH (address ) and 7SROH (address ) are then set to
∞ since they are not needed.
But you may use the T1-timers for single-stage protection if you wish to utilize the fa-
cility of setting different delay times after single-pole trip and three-pole trip of the
feeder protection. In this case set 7SROH (address ) and 7SROH (ad-
dress ) separately but address  S5(75,37 to 12, to avoid a single-