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JPSSE2022
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Recently, I have been doing some power systems studies in the utility I work in. In our short-circuit studies, we usually only consider 3-phase and single-phase faults.

However, I noticed that the double-line-to-ground fault level is extremely higher, to the point it far exceeds the circuit breaker ratings on many substations.

Since it is not conventional to study double-line-to-ground, and it is never seen in the recommendations of international standards such as IEC, do you think it is important that I consider it in my studies?

This concern has been bothering me for a while. I look forward to hearing your thoughts.

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answered Mar 29 '2

jconto
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The keyword here is "credible fault". If a fault is likely to occur in your network then it has to be studied. "Conventional" criteria in power system studies have been pass down based on past realities (lack of computational power, lack of data). Modern analysis tools are able to calculate 3ph, LG, LLG, LL faults on a single run. In a substation, the breaker duty capability should be above the max of those 4 fault currents. Now the issue is data quality (network data, sequence data).

I recommend to study all four types of faults in short circuit studies.

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Asked: Mar 29 '2

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Last updated: Mar 29 '22

Double-line-to-ground fault

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