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I appreciate all the responses. It seems there is no cut and dry answer to this one. From this discussion I gather that if we are matching voltage we also need to make sure that the transformers are not more than a couple steps off, and that if matching steps we need to make sure the voltages...

I have a substation transformer question and would like to get other people’s opinion or current practice on the subject. We have several substations with 115kV to 12.47kV transformers that feed a set of switchgear. Some of these stations have 2 transformers, which is where my question comes...

A coworker in our generation engineering department recently experienced this problem so I thought I’d check on here for some ideas for him, I’ll try to be brief, let me know if you need more information. We had an 11.5kv, 9MW hydro unit out for 2 weeks of scheduled maintenance. During this...

This is medium voltage switchgear. I got the 8" gap by measuring the seperation of the stabs on the back of the breaker. I was under the impression that the Gap was the acutal spacing between the energized parts, is this not correct? Table D.8.2 in 70E has a column labeled "Typical conductor...

Thanks for all the input. This won't be such a big deal when we get the clearing time reduced, but until then how would you quantify the hazard? I am tempted to use the 1584 equations (even though they are not valid past 6"), increase them by some margin and then write up an explanation as to...

Here is my system data: V = 12.47kV Isc = 8.338kA Ia = 8.12kA D = 914mm (36") t = 1.1 seconds G = 152mm (~6") Using the IEEE 1584 equation in 70E I get an incident energy of 11.3 cal/sq cm Using the theoretical equation [D.8.4] in 70E I get an incident energy of 70 cal/sq cm How can they be...

Sure enough, this voltage restraint was set at 33%, we are gonna move it up to 85%. Thanks

I've been reading this forum since I got out of school (about a year ago). I've learned alot from everyone here, hopefully I can start contributing as I become more competent in the power field, for now I have a question I would like advice on. Recently we had a main breaker trip on...

Thanks, I figured that was the case, but some of the manufacturers make it a pain to look up the device curves online

If I have the short time delay on a LV molded case circuit breaker set at .1 seconds, is this the total amount of time it will take the breaker to open? Does the .1 seconds include breaker operating time or is it just a delay before the breaker starts to operate?