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I think I got it now. I was missing the X and Y nodes and that makes a difference. Say X (assume a relay) is energized then 4-A1 would energize if position “A” is selected in the rotory switch (43GF) as contact 1-2 would close and so would 5-6 but since 3-4 is open, 4-A2 wouldn’t energize. Now...

Hello I need help interpreting the rotary switch (CHR10 type) schematic. I have drawn part of the vendor drawing that I need help with. How do you read this? Say switch is on A position, does this mean contacts 1-2, 5-6 and 9-10 are closed? If B is chosen, 3-4, 7-8 and 11-12 would be closed...

Thanks electricpete. I looked at most standard and the one you have referenced is the best that I could find on the subject.

Please recommend any tips/ reference material/ standard (IEEE, IEC, ANSI) for conducting core/coil inspection of a liquid immersed transformer.

I'd like to thank dpc and JG2828 for their time and valuable suggestions.

THanks for the preliminary sets of answers. Assume we don't have the manufacturer's data; what would you do then? Are the current/voltage they are tested at sufficient to give us the relay time? If yes, which phase would we take? Maximum of all three phases? I agree about addition of the Diff...

We have to calculate the total relay time (tripping delay) for a 115 kV Breaker for fault analysis. Let’s say primary lead differential relays operate a lockout relay which in turn trips another WL-1 relay for breaker trip. The results (test conducted a decade ago) we have is as follows: • A...

Appreciate the input But I am more looking towards the requirement for the foundation at this time. How far from any existing building should the transformer be and which IEEE code (not 60) should be used for grounding etc.

We are planning to store a 700MVA (about 900,000 lbs) transformer in a new foundation with storm drain facility. The foundation will not have any fire protrection (sprinkler system) but will have oil containment pit. We'd like to know what requirements are there for storage of a spare...

What I collect from all your responses is that MCC can be used to supply power to my intended loads as long as the bucket has a breaker (molded case) NOT a MCC starter/protector. I guess that confirms my question, now only thing I need is an empty bucket in my MCC where I can install a ckt...

I know MCCs are commonly used for providing power to a motor circuit, such as pump or even motor etc. They have the OL/OC protection and starter cicuitry. Question I have is, can I use one of the bucket from a generic 480V MCC cubicle to provide power for Transformer auxilliaries which do not...

Read about Tan Delta test.

Agree with the posting above. Typically we don't worry if we are not talking about a long line which could have its own contribution.

Ideally, you would have an online oil purification system installed, I have seen some for LTC cabinet and I am sure that exists for the whole xfmr too. I don't agree with the online purification not because of the potential danger involved, but because you are getting rid of the symptoms not...

Scottf Appreciate the response. To me it is kind of counter intuitive that when a CT has 200/400:5 with 1.5/2.0 RF, the 1.5 factor applies to 400 NOT 200 and 2.0 applies to 200 not 400 (first to first, second to second). But since you are more exposed to this I will take your word for it. Thanks...

Thanks Scotf However, since it is a dual ratio meter, 200/400:5 with 1.5/2.0 RF; I think 1.5 applies to 200:5 ratio and 2 applies to 400:5 ratio. Hence, the continuous amps is 400*2=800 amps. Since the new one has 200:5 with RF 4, i.e. 200*4=800 amps that should work. Do you agree? Ok, the...

Thermal limits indicate max VA that can be passed through a conductor without damaging the insulator. Short Circuit limit is different and denotes maximum current that a breaker’s interrupter can withstand. Refer to IEEE Std 551-2006 for SC calculation.

Need to get your input on going from multi ratio revenue meter to single ratio. Only the CT discrepancies are listed: The existing one: 200/400:5 DR with 1.5/2.0 RF Thermal rating: 3000 VA Proposed one: 200:5 SR at 4.0 Thermal rating: 4000 VA The VT ratio (700/1200:1:1), accuracy...