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It really comes down to the efficiency of the motor. Check out your current motor eff. If it is not a newer motor most likely you can save on operating expense by buying a high eff motor. Of course you want your load to match the most eff curve of the motor. I tell my operations elec guys to...

Thanks all for your input. It does give me insight that these faults although uncommon do happen. And that it can get quite hot given certain circumstances. I would still appreciate any more feedback from others that have experienced high ground heating with this type of fault. Thanks, Will...

Here is a rough sketch. Primary TX Secondary Service Panel ---------- ||-------------- ---------| Fault Here are some numbers: Example - Primary current: 25 amps - Secondary current: 250 amps Secondary Volts: 2 cond, 240V, + neutral...

To provide more info - what I was trying to get to: Given a fault condition exists on the cable - L-G for example. High resistance fault - current is below the upstream fuse capacity on the primary side of the transformer. And as the fault is before the downstream breaker the breaker is no...

Hi All, Would like to know if anyone could offer their observations of the heating involved with a underground cable fault, either 240 or 480V. I am having an issue where I would like to understand how much heating could possibly occur. This would be for a supply service on the secondary side...

Hi ZogZog, Yes I missed it - here is what I found. *9. Perform power-factor or dissipation-factor tests on each pole with the breaker open and each phase with the breaker closed. *10. Perform power-factor or dissipation-factor tests on each bushing. Use hot collar procedures if bushings are...

Hi All, Thanks for your responses. Yes manual does shed some light as well, say to use an AC highpot. Also warns about Xrays - so the last few comments cleared up my next question. Last question - "A power factor test should also be done if it is new to establish baseline data. " from Zogzog...

Hi, We need to test a new medium voltage vacuum breaker. Manual says to us an AC megger. We have a DC meggar. Anyone know the reason for the difference of AC vs DC meggering? Thanks, Will...