You are totally correct. Use the nominal system and motor paramaters for the first "fire up" of the motor. If operation leads you to another conclusion (var flow, instability) tou can always go back and change the tap accordingly.
Do primary injection testing! It's the only way to test the whole breaker - CTs, trip unit and all interconnections. The low voltage at the output of a high current test set will not damage the contacts.
I agree, mechanical stress is much more of a concern than thermal overload. But transformers are designed and built to live through energisation inrush. If the down stream equipment can stand the energisation - de-energisation the transformer should be the least of your problems
What were the relay failures that the self check did not catch?
Solid state relays generally work perfectly if they are set up properly to begin with and nobody "lets the smoke out".
I've been setting and testing them for going on 15 years now and have never seen one that passed initial test...
As a guy who makes part of his living doing these tests - let me add two cents. Slope method, if done correctly, is just as valid as fall of potential. Ten times the major diagonal is an ideal - not a "make or break".
I have tested lots of substations, from 345 kV on down. Some come close to...
TurbineGen:
Let me go back to the original post. My first question would be - which breakers are closing and WHY?
Checking actual voltage should be easy with a PT and a Fluke. Then you'd know what the voltage actually is.
NorthSlope
I don't know what a "ground rod resistance meter" is - BUT - there are several legitimate ways to check the resistance of a ground rod to "remote earth" (the traditional definition). What is your resistance to a "ground resistance meter"?
Overloading would NOT account for rust on the top of the core. That's a function of water - only! 23 MW on a 37.5 MVA transformer is well within loading norms. How lightly loaded, or unloaded, lets moisture "settle in" to a sealed tank is beyond me.
Depending on what "paper was ruined" means -...
Surge arresters respond to voltage and rate-of-rise of voltage. Fuses respond to current. Up here we do have arresters in front of fuses. How many it has saved over the years I can't say. With a lot of calculation you could take the fuse clearing curve, the anticipated rate-of-rise of the...
It depends on what is most imprtant to you in a "power quality" analyzer. I have used both an rpm (now made by Fluke)and an AstroMed. If you want primarilly voltage triggered transients use the rpm. (It has 5 current channels and 4 voltage channels in "Y" configuration),and an AstroMed Dash 18...
Shielding on the cables is for voltage field control - NOT magnetic field control. It is entirely possible to use non-magnetic steels for a structural member and route all three phases, individually, through the same plate. Large transformers do this all the time.
1. If you're playing in the US of A use 208Y / 120. Not some odd-ball voltage rating.
2. Probably not necessary. Any motor small enough to be a single phase load should NOT affect the controls unless you'rew on an incredibly soft system.
3. YES it is bad practice. You're spending somebody's...
MI cable is notoriously difficult to measure. Temperature makes a difference as does relative humidity. How far apart were the readings taken? I agree with the comment on polarity. Standards say rhat the item inder test (a conductor in your case) should be Negative and the reference...
Transformers don't CAUSE fluctuations. They reflect, from one winding to another, what happens external to them. (Barring an internal fault - which doesn't seem to be the case here)
On which side of the transformer (primary or secondary) are these fluctuations being noticed?
What type of...
