When the transient state with protection coordination option is selected, SPARD® mp Power starts an internal clock that simulates the system’s electrical times. This clock starts at the moment the user indicates the place of the failure (with the aforementioned double click). Then it calculates the transient voltages and currents. For each relay, fuse, etc. it checks the operation type such as time vs. current for over-current relays and fuses, impedance characteristics and direction for distance relays, under voltage and superior time for low voltage relays, etc. It also indicates relay operation in the simulated time. If the curve or another characteristic indicates relay operation, its graphic symbol becomes red (simulating the flag in the old electro-mechanical relays) and it opens the switch(es) associated to the relay (switch symbol becomes green). The program does not stop simulating until the failure is completely corrected (even if total system blackout is necessary) or if after a simulation period (10 sec. approximately) it was not isolated. Once the system has stopped oscillating (this can be observed graphically) the user can find out in each operated relay the function that acted (50,51,67,21, zone 1,21 zone 2,50N, 51N, 27, 59, etc.), time from failure start until it operated, the current, etc. In the case of distance relays the impedance can also be observed. The trigger time from failure can also be seen for the switches. The user can see the virtual time for the non-triggered relays (time of triggering without the other protections), the current and other information. In this way the user can see whether the calibrations are correct or not and if the system is out of sync. The user can look at the operation curves, draw his own conclusions and change the data for the relays, start current, type of curve, time dial, reach, etc., and repeat the simulation process In order to obtain a fast, selective and coordinate system behavior.
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