Depending on the type of internal fault detected the P632 will respond by trying to eliminate the problem with a warm restart. (See above; for further details read also about P632 behavior with problems in Chapter “Troubleshooting”.) Whether or not this measure will suffice can only be determined if the monitoring signal has not already been stored in the monitoring signal memory because of a previous fault. If it was already stored and a second fault is detected then, depending on the type of fault detected, the P632 will be blocked after the second warm restart.

In order to better monitor this behavior the parameter at SFMON: Mon.sig. retention is applied. This parameter may either be set to ‘Blocked’ or to a time duration (in hours). (It is, however, discouraged to set it to 0, because in this case, there would be no blocking at all, so that there would be the danger of maloperation in case of a permanent failure.)

The default for this timer stage is Blocked, i.e. blocking of the protection device with two identical faults occurs independently of the time elapsed since the first fault monitoring signal was issued.

The behavior caused by sporadic faults could lead to an unwanted blocking of the P632 if the monitoring signal memory had not been reset in the interim, for example, because the substation is difficult to reach in wintertime or reading-out and clearing of the monitoring signal memory via the communication interfaces was not enabled. To defuse this problem it is suggested to set the function parameter to a specific time period so that blocking will only occur if the same fault occurs again within this time period. Otherwise, the P632 will continue to operate normally after a warm restart.