4160 phase rotation verification 2

[tbwil1]

Hello all:
I am putting a new 4160V diesel genset in service on an existing med voltage transfer switch. To verify phase rotation I have a 25kV meter with two probes. I plan on reading utility A to gen A and so on with B and C, watching them go to zero volts as they drift in and out. If all three drift to zero I have the right rotation...accurate??

 

[PWR]

They are correct if all three phases go to near zero difference simultaneously. It is best to have two meters to do the test as incorrect rotation will not permit two phases to go to zero difference at the same time. If you can control the speed accurately enough you could move the meter between the phases.

 

[waross]

A suggestion;
1> Find some 4160/120 PTs and extend the 120 volt leads so that you don't have to go near the 4160.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

One set of VTs located such that they can be energized by each source without any wiring changes and a meter that can indicate phase rotation. Check rotation from both sources independently. Anything that involves moving connections leaves open the possibility of a misconnection. That guy Murphy, the one with the Law, loves the possibility of misconnection.

 

[slavag]

Hello.
Please see attached thread.
thread238-189772
All best solutions are included.
Good Luck.
Slava

 

[Marmite]

You can't check rotation at all if all you have is a single voltmeter. You would need a phase rotation tester, or rotoscope. You can check that the two sources are in phase with a single voltmeter, but only if the phase relationship if fixed. If your generator is drifting in and out of synch with the mains then you can not rely on the readings as you would need to take three readings at the same instant. Impossible with an HV tester.
Regards
Marmite

 

[lansford]

In the threads, a reference is made to a "high voltage tester" and the original post is not clear if voltge metering (PT) are used of if he is using a HV tester.
if the two systems are not refererenced to ground,one can get false results if the testing is completed expecting to test as if the two systems are referenced to ground!
Jim

 

[oldfieldguy]

This one is simple.

Two sets of analog voltmeters rated for the voltage. Access to the three hot terminals of both systems. The appropriate personal protective equipment and safety standby people.

With both systems hot and frequencies pretty closely matched, place one voltmeter with one probe and "a" of one system and "a" of the other. Place the other voltmeter on one of the other phases likewise.

Observe the voltmeter needles. They will both swing as the voltage of one system swings in reference to the other due to a slight frequency difference. If the rotations one both systems are the same, the needles on the two voltmeters will swing in the same direction together. If they are not, then the needles will swing in opposite directions. This isn't a subtle difference. It is obvious when you see it. You can move one probe to another phase to see what it looks like.

As for using PT secondary voltages to do the checks, this is good too, if you're ABSOLUTELY SURE of the wiring on the PT's. I've seen a few that weren't right. This would be a bad time to find out.

I've not had real success with using the new digital voltmeters due to response time for display.

old field guy

 

[waross]

And don't forget that the voltage swings on a 4160 system will be over 8000 volts. I mis-spoke when I suggested 4160 volt PTs. You will need PTs rated for over 8320 volts.
I appologise profusely for my mistake. (Maybe I need more coffee... Maybe less)

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[slavag]

Not Bill, this is mistake, not more, not less, you need other coffee, made in Turkey or some Arabic country
Please don't angree on me, but Canadien filter coffee is..., no words.;-)
Regards.
Slava

 

[tbwil1]

Thanks Fellas, the genset going in has a very accurate gov controller, I'm reasonably certain I can get it drifting very slowly and get a reading on two or maybe all three when they pass 0v simultaneously. I enjoy reading this forum, the information is great.
Brian

 

[davidbeach]

tbwil1,

No, you're not reading it correctly; you can't do it with sequential measurements. It may work, but it may not work, and if it doesn't work it will not work spectacularly

 

[tbwil1]

If I have a window of 2 to 3 seconds when the two sources are synchronized and passing zero volts, which is entirely possible with these controls, and two, or best case all three utility to gen readings are close to identical, won't that prove it?

regards,

Brian

 

[waross]

If these are ungrounded systems, try connecting one phase together with a jumper. That will give you a reference for the other phases. If you measure from one phase of an ungrounded system to one phase of another ungrounded system your voltages will be a reflection of the leakage currents to ground of the measured phase of each system. Interesting but meaningless and confusing.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[burnt2x]

tbwil1,
You only need to take rotation check (using a phase rotation tester) on the PT's three terminals of each source(on the MVTS PT's and on the diesel gen side PT's). Be sure you correctly wire the PT's and mark each terminal A, B, and C. Check if the rotation is ABC or CBA on each terminal set. If they are of the same phase rotation, then its okay to tie both sources.
Regarding reference problems, you always ground the neutral of PT's (the phase rotation tester I used is rated 500V, so no problem with testing equipment being busted). It doesn't take long.

 

[catserveng]

I hate to sound like a stick in the mud, but improper phasing of paralleled generators can cause severe damage and possibly injury.

I would strongly recommend getting a local electrical testing company or competent electrical contractor to do the phase checking on a medium voltage machine if you are not positvely sure how to do it. I don't feel the risk of having someone who isn't sure of how to make those essential checks is worth the money you would save by not having a qualified entity perform that service for you. Then you could observe and decide if you want to gear up to make those kinds of checks on your own in the future. Safety first!

Hope that helps.

 

[slavag]

Hello.
At this case, only Mike ( Catserveng) is right. Don't take chance, if don't sure.
Star to Mike.
Best Regards.
Slava
Safety first!!!Always!!!!!

 

[tbwil1]

Thanks Mike. This particular commissioning is a bit of an oddball startup in that there is an old G&W oil filled transfr switch (approx 1977 vintage)that will be staying in service. Normally we would supply the switchgear with the genset and I would have have a twisted pair of biasing lines that would drive paralleled gens in sync and hold them there for as long as needed but this is a stand alone unit with no paralleling provisions and old pt's at the ends of the gear. I will probably work on renting a second meter if i have doubts of safety or accuracy. Thanks again all.

regards,

Brian