Discussion in 'The Projects Forum' started by agsnip, Dec 4, 2012.

1. ### agsnip Thread Starter Member

Nov 19, 2009
12
0
hi,
i need help about using simulink for power system project. 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 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 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

2. ### Skeebopstop Active Member

Jan 9, 2009
358
9
Use a comparator with hysteresis to check your voltages. I am uncertain if you need to do it on the AC or DC component of the voltage. If DC rectify the AC and then create 5V supply for a comparator that has appropriate hysteresis and use comparator output to drive said relay to open or close circuit breaker. Might need to buffer comparator as generally they are open collector so not much power.