Category Archives: Short-circuits and faults

Fault analysis in non-safety-related circuits during design basis events

It is typical when calculating short circuit currents to incorporate the full cable length into the fault analysis. However, you must be careful when analyzing short-circuits during design basis events. Continue reading

GE HAA relays in sudden-pressure applications

Picture of GE HAA 16B relay

Fault-pressure relays protect transformers from internal electrical faults that other protective relays, like differential or overcurrent, can’t always detect. If the transformer’s protective relaying scheme is old, it might have a GE model HAA relay installed. This is likely in nuclear power plants of a late 1960s or early 1970s vintage. Continue reading

GE IAC and ABB HU Transformer Protective Relays in Nuclear Power Plants

Protective relay panel, photo courtesy North American Switchgear, whose website it located at, microprocessor-based protective relays aren’t yet a common staple in nuclear power plants because of the trepidation associated with installing sensitive solid-state circuitry in safety-critical applications. This trend, however, is slowly changing. Until then, though, it is useful to become aquainted with the older kinds of relays still in operation.

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An explanation of the origin of a generator’s subtransient reactance

The term “subtransient reactance” is denoted by the symbol X’’d and is used to calculate available short-circuit generator fault currents. But where does it come from? What’s its origin? Continue reading

In-depth explanation of the short-circuit behaviors of five important types of electrical equipment

I described in a previous article the benefits of learning how to do short-circuit analysis by hand. There are five primary elements that you need to know how to model when doing so. I go into the details here . . . . Continue reading

Calculating short-circuit currents by hand

You won’t do many short-circuit hand calculations, but it’s useful to go through the exercise to develop an understanding of the fault behavior of typical electrical equipment. There are five you should get to know . . . . Continue reading

Three kinds of protective devices

There are three common types of protective devices you’ll encounter in the nuclear power industry. Here I summarize their functionality . . . .

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