# How can i design an over/under voltage relay by using simulink?

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Mee Guring on 30 Nov 2012
Answered: Joel Van Sickel on 2 Dec 2022
example of the voltage relay is, it has a fundamental voltage of 400V. When it reaches 410V or over, the relay tripped(overvoltage). when the relay is 390 or below, the relay tripped(undervoltage). the relay is connected to a circuit breaker. it is a single phase relay. the input is the sinwave(rms. there is a harmonic connected to the input because the circuit is to check the the graphs of harmonic distortion. the RLC load is connected as an output.
this is the characteristic for the over voltage t=k>*a/[(b*(U/Us -1)-0.5)^p] + c
t = operate time [s] k> = time multiplier, 0.4 U = measured voltage [V] U> = set start voltage [V] a = constant 480 b = constant 32 c = constant 0.035 p = constant, 2
undervoltage t=k<*a/[(b*(1-U/Us)-0.5)^p] + c
t = operate time [s] k< = time multiplier, 0.4 U = measured voltage [V] U< = set start voltage [V] a = constant 480 b = constant 32 c = constant 0.055 p = constant 2

Joel Van Sickel on 2 Dec 2022
You can implement all of that logic in Simulink to create a control signal for a breaker or an ideal switch to behave as the relay (ideal switch is likely better, unless you want logic to wait for a zero crossing before disconnecting). If you prefer matlab, you could also use the matlab function to implement this logic.

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