What is psm tsm for idmt relay?

Answer 1

PSM stands for Plug setting multiplier and can be found on the front of the relay module in the form of a scale . PSM = Actual or fault current in the relay / ( CT Secondary current X Amp setting in the relay) From the above value of PSM find the time in seconds from the front of relay panel scale i.e., PSM Vrs Time in seconds Miltiply the time in seconds with the TSM to find the tripping time for the relay for the specific value of fault current TSM = Time setting multiplier Relay Operating time = TSM x time in seconds <- as observed from the scale .