Electrical Gronding Circuit

I want to run a simulation for an electrical (not electronic) circuit. No transient behavior. ONLY steady state.

The source is the local utility. The local utility provides power with the following characteristics. Steady state RMS voltage of 7.6 kV at 60 Hz. II modeled this as a voltage function generator at 7.6 kV RMS, 60 Hz.

The utility provides a maximum ground fault short-circuit current of 12 kA RMS. I modeled this with a current generator of 12 kA.

Then I connected both sources in parallel.

Question 1: Is this the correct model?

The rest of the circuit I do not have any problem.

Question 2: Should I run the time Time Domain simulation (even it is a steady state calculation with RMS values)?.

I want to know the RMS voltage drop at each point in the circuit and the RMS current through the circuit.

Question 3: With the current modeling scenario, the output voltage is a variable curve and in the Y axes (voltage) the values indicated in the axis are all zero. Why the voltage is depending on time and why the values of voltage in the Y axis are all zero?

Thanks so much.

by corvalan
April 29, 2014

Hi corvalan,

Welcome to CL.

Sorry but you have not given enough information from which to answer your questions.

You have stated some facts but you have not made clear exactly what you are trying to model.

Can you make an example of your circuit public so that people can see what you are asking about?

by signality
May 04, 2014

Thanks for answering. I made the entire project public with the name Ground Fault 1.

This is an electrical circuit (not electronic). I am interested in the steady state RMS voltage at different points. Also in the value of the steady state RMS current. It is a very simple circuit with ohms law. The frequency always remains at 60Hz.

This circuit is fed by the regional utility that gives you the RMS voltage, frequency, and maximum short circuit current. I modeled this as a voltage source (voltage and frequency) in parallel with a current source (the available short circuit current). I believe this model of the utility is not right.

Then I have the challenge of running the simulation. It is AC voltage (RMS) which does not varies with time and the frequency is fixed. So it is not a time domain calculation neither a frequency domain calculation. Both quanties are fixed because I am afer the RMS voltage at different points in the circuit.

Is it possible to calculate this very simple ohms law procedure with CircuitLab?

If so, how?

by corvalan
May 04, 2014

If you are only interested in RMS values at a fixed frequency and the resistances in your circuit have no frequency dependency (i.e. there are no inductive or capacitive reactances) then just replace the AC source with a DC source of the same value as the RMS value of your AC source.

The DC voltages and currents around such a circuit will be equal to the rms values of a purely resistive AC circuit.

In your example:

https://www.circuitlab.com/circuit/pb56g5/ground-fault-1/

you have no current source or sink, only V1 a 7.6kV voltage source.

This does not seem to relate tp the description you have given including a 12kA current generator.

At present all the switches in the circuit are open and so there is effectively no load on the voltage source.

Therefore it is still not clear exactly what you wish to model.

p.s. when posting in CL to save people having to hunt through your Workbench to find your circuit, it is good practice to include the url to your public (or unlisted) circuit by pasting a link from the using the Link & Share options into your post.

by signality
May 05, 2014

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