As the interlock conditions are also transmitted together with reporting in the IEC 61850 communication protocol it is a requirement that these interlock conditions are cyclically checked and not only with the request for a switching operation.

Therefore the parameter (221 104) ILOCK: Cycle t interl.check allows for setting the cycle time (range from 100 ms to 10 s), after which a check of the interlock conditions is carried out. As additional processor capacity must be provided for each of these checks it must be ensured that a favorable compromise is found for the cycle time setting value. On the one hand it is desirable to select a cycle time value which is as short as possible so that changes in the interlock conditions are updated without any notable delays, but on the other hand this cycle time value should not be so large that the P632 system will be under too much strain. As the P632 CPU load is dependent on the total number of function groups having been configured it is not possible to suggest a generally acceptable cycle time value.