may you help me getting a MATLAB function that represents under frequency relay ?

Do you have a MATLAB function that represents an under frequency relay?

[Star Strider]

I apologise for my not being informed, but since it’s possible that there could be different terms for it, just what is an ‘under frequency relay’?

[fotouh maree]

sir, iam glad to answer you , " under frequency relay " is a protective device that used to protect loads and generators as well. it monitors frequency of the grid and compare it with a preset value (50 or 60 HZ) then take a decision (to trip or not).

[Star Strider]

Thank you. I actually built one of those in hardware once to protect the outboard final amplifier of my amateur radio transmitter. It was a bandstop filter (essentially a parallel LC circuit in series with a power resistor) that energised a relay to disconnect the mains power if the frequency varied too much. (I don’t remember it ever tripping, at least while I was on the air.)

I don’t have SimPowerSystems, but if I were to design a Simulink block for one, I would create it as bandpass or bandstop filter (whichever you prefer) that would trip if the output changed beyond a certain threshold.

I’m not listing this as an Answer because it isn’t one.

[fotouh maree]

Thank you for your consideration, what i need is a MATLAB function that able to monitor frequency of the electrical grid instantaneously then compare it with a preset value then take a decision. shorty, what i need is not a filter , what i want is the ability to 1- monitor (measure) frequency , 2- compare it with a predefined value 3- trip a circuit breaker . i hope i am not disturbing you.