How do you calculate relay settings?
Calculation of Over Current Relay Setting:Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480 Amp.Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current.Required Over Load Relay Plug Setting = 480 / 600 = 0.8.More items…•.
Where is the plug setting multiplier?
Plug setting multiplier is nothing but a ratio between the actual fault current in the relay operating coil to pick up current (the relay current setting). In other words, the ratio between the CT (current transformer) secondary current to relay operating current is called plug setting multiplier (PSM).
What is standard inverse curve?
Inverse Time Over Current is also referred to as Time Over Current (TOC), or Inverse Definite Minimum Time (IDMT). It means that the trip time is inversely proportional to the fault current. The trip time is calculated from the following parameters: Trip curve. Select from the standard set of IEC and IEEE curves.
How do you calculate PSM?
Say current setting of the relay is 150 % therefore pick up current of the relay is 1 × 150% = 1.5 A. Now, after calculating PSM, we have to find out the total time of operation of the relay from Time/PSM curve. From the curve, say we found the time of operation of relay is 3 second for PSM = 10.
What is PSM and TMS?
TSM is time setting multiplier which comes into role only when pick-up value is reached. Practically PSM tell us about the magnitude of fault. The more the value of fault current, the more will be the PSM and hence the relay should clear the fault more quickly.
What is TMS relay?
Formally, TMS is. defined as the ratio where, for a given PSM T is the desired relay operating time and Tm is the corresponding operating time at TMS of 1.0. TMS is also referred to as TDS (Time Dial Setting).