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 .
DMT relay stands for definitive mean time, and IDMT stands for inverse definitive mean time. In IDMT relay, there is a minimum time delay with magnitude.
As with any IDMT relay the higher the fault current the quicker the trip time.
i working 66 kv and 220 kv substation. over substatin transformer and 66 kv sf6 bracker use i intersted for working of idmt realys with breacker tripping coil.
i working 66 kv and 220 kv substation. over substatin transformer and 66 kv sf6 bracker use i intersted for working of idmt realys with breacker tripping coil.
idmt curve
Inverse Definite Minimum Time Lag = IDMT relay It's a electromagnetic type rotating disk relay. Tripping time of relay decreases with increasing fault current. see http://myweb.tiscali.co.uk/robert.booth/uni/docs/Power%20Supply%20Assignment%203.pdf
PSM-I Exam: Unlocking Your Agile Potential
PSM Makassar was created on 1915-11-02.
the actual r.m.s current flowing in the relay expressed as a multiple of the setting current (pick up current) is known as plug setting multiplier.mathematically ,PSM= SECONDARY CURRENT/RELAY CURRENT SETTINGorPSM= (primary current during fault)/(relay current setting *C.T ratio)
The CT associated with the DMT, IDMT, inverse, very inverse and extremely inverse possess different characteristics. In particular, Inverse and IDMT CT’s have different operating points on their magnetic characteristics. i.e. Both have different saturation levels.
idmt means inverse definite minimum time. so in this type of relay as the value of operand that is current increase time taken by the relay to operate decrease. higher the current lower is the time taken by the relay to operate. AND dmt definite minimum time (DMT) relay take its minimum time to operate regardless of the value of the current. The definite mean time lag in disc type EM relays is inverse to current as the disc is faster at higher current and hence the less time.Definite mean time lag is possible in static relays by setting the time lag.