plug setting multiplier

You will have to explain exactly what your are talking about because I have no idea. Plug Setting Multiplier of what?

Same response as JoaT from here in the USA... Don't know what kind of device you are asking about, nor setting multiplier of what kind of value?

OK. This is the Plug Setting Multiplier of an over current relay I was talking of...please help me out.

That helps a bit, but we still need to know a lot more!

Sounds like a shunt resistor that carries most of the current, so a low current relay can protect a higher current circuit. But is the shunt directly in parallel with the relay coil, or is there some sensing circuitry? And just what exactly do you want to accomplish? What are the specs of the relay, and what are the specs of the circuit it is to protect? AC, DC, single or three phase, resistive or inductive, etc.?

I Would like to define few terms before explaining you the terms. Normally CT secondary is of either 5A or 1A . Let us consider you are talking about CT with secondary of 5A. Now you have chosen current setting of relay as 150% which means 150% of 5A which is 7.5. Remember 7.5 A now as it is important to remember. Now when there is a fault in the circuit there will be heavy (large) current flow in the circuit. Let us say the current is 5000A in the circuit and let us say you have used the CT of 500/5A as described above as 5A secondary. The 5000 A in primary will be reflected as 5000/(500/5)=5000/100=50 A. Now to find the plug setting multiplier you have to divide 50 A by 7.5 A which is 8. so your plug setting multiplier is 8 and you have to find at which time the relay causes the breaker to trip depending upon the curve with let us say 1 as a time setting multiplier . But if you chose 0.8 as a time setting multiplier you are going to trip faster that is 0.8*time taken when the time setting multiplier was 1. I think you are clear by now regards Rajendra

Rajendra bhai, thanks for giving the idea of PSM. But it will be really thankfull to you if u can provide some information about Curves. what are all those curves like NI,VI,EI and breif description about relays like IDMT,DT

PSM = I (relay) / PS

PS : Plug setting.

consider 1.0 A relay (Relay coil is designed to carry current of 1.0 A on continuous basis)

Plug has been set at 0.5 A (50 %)

Fault current : 5 A

PSM : 5.0/ 0.5 = 10

If PSM is less than 1, it means normal conditions

If PSM is greater than 1, Relay is supposed to pick up

Higher values of PSM indicates that how serious the fault is