Transformer Differential protection trip 1

[azril83]

Good Day Friends,
actually i faced same problem same as one of our member here. i was working at CCGT power plant. our generator was from ABB GT13E2. After finished major overhaul for the generator(rated 15.75kV), and during the commisioning of the generator, our generator protection trigger differential protection (87UAT). This happen when we would like to take high load for big motor rated at 6.6kV. We checked CT connection at the UAT, do some calibration to the REG card, and yet still cannot solve the problem. We then checked the commisioning document and noticed that vector unit setting at the REG card have to be changed to Y7. but during the overhaul we never change any setting at the REG set file. Anybody can explain this?

 

[slavag]

Hi Azril83.
1. first of all I recommend to you ask ABB support.
Are you have ABB LEC in your country?
2. For help to you more information nedeed
How are you freindly with this relay and CAP2-316?
What is a FW version of CPU card?
What is a calibration to the REG card you provided and what card?
Why provide commisiioning of REG?
Are you provide stability test for 87UAT?
Please send setting of 87UAT protection, reference value
of relevant CT channel.
What is a data of UAT?
What is a size of CT on both of sides?
I try help you, but is not so eazy via forum.
Regards.
Slava.

 

[oldfieldguy]

azril83--

Since you just finished major overhaul, are we correct in assuming that it was running well before the overhaul?

If so, then carefully review any electrical work or testing that took place, and insure that all equipment was returned to its proper operating state.

Does the generator trip immediately upon application of excitation or does it wait until a significant load is applied?

I had a 450 MW steam unit that came down for maintenance and when they restarted, it would drop out on current imbalance (negative sequence). The manufacturer reps had shorted out some CT's for some testing of the stator and a small shorting conductor was left in place.

old field guy

 

[slavag]

Azril83, Old field guy are right.
Don't forget about after overhaul problems.
Please see attached link.

thread238-195305
Regards.
Slava.
P.S.
See in 87UAT functional meas. Id and Ib parameters.

 

[slavag]

Hi Azril83.
Maybe I ask you about other REG, I asked about REG216/316.
Slava

 

[azril83]

i was using REG216. Normally after 2 years then we will do the calibration of the REG card. But, in my case, the calibration already done just a few months ago. so, after the unit shutdown, we proceed for the overhaul. we never disturb the REG card. but, unfortunately, our GT trip when we want to take high load (big motor 6.6kV). Excitation was not take into place yet. I just a little bit confuse, why before the overhaul our unit can run properly, but just after overhaul we have to change the setting of the vector group at REG card. our UAT spec yn1.

 

[slavag]

Hi Azril83.
I think you need back setting to yn7( BTW in REG216 you have only y7).
You are right, your trafo is yn1, but I assume that you have not right polirity on one 3xCT set and in commissioning time ( stability test) instead change CT wiring, commissioning eng. change vector group into relay
( yn1 -yn7 = 180 deg.).
It's easy check in REG216:
You need connect to relay and check:
1. Analog meas value, six channels of 87UAT, put reference point on first channel ( phase R of HV side) and check angels between phases on the same voltage level and between R-R, S-S and T-T on HV and LV level.
2. Function meas. check sum current and restraint current
and you see on this moment restraint current =0 and Id= sum of two currents ( of course vectory sum.).
Of course you need load, for prevent unwanted trip disconnect in setfile 87UAT trip from trip matrix, check all points and after test back again 87UAT trip to trip matrix.
Second way, check polirity of CT's and change it according to design.
Good luck.
Slava

 

[slavag]

Hi Azril.
see attached link.
stability test of step up trafo 250MVA yd1

http://i6.tinypic.com/6ais5e0.gif

same trafo: on load test.

http://i16.tinypic.com/6bd7q5x.jpg

Regards.
Slava

 

[azril83]

thanks Mr. slava. i really appreciate for the valuable information.

 

[lz5pl]

slavaq, what kind of software had you used for these stability tests? Are these screenshots taken from relay relay setting software or from disturbance evaluation soft? They are looking quite convenient.

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It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[slavag]

Hi Iz5pl.
It's CAP2-316, RE_216/316 ABB relay setting tool.
This relays and tool open for user on-line monitoring for stability and on-load tests.
This screenshots part of my reports for customer.
I save it, because it was my first commissioning of REG216 system w/o ABB person.
Regards.
Slava

 

[lz5pl]

Thank you, slavaq. I have no experience with ABB's REx216/316 relays, only with REL/RET512, but their software is different. First screenshot is very similar to Siemens Web Monitor tool, which I like very much. I also use it for Energizing Report.

http://www.triel.bg

------------------------
It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[slavag]

Yes, both of series are ABB relays, but SW complitly different and not only SW. One from Swiss ( BBC), one from Swedeen ( Asea).
Siemens is very similar, but also not powerful as CAP2-316.
BTW, we start think about use new ABB platform from Swedeen
RE_670.
Regards.
Slava

 

[lz5pl]

It would be a good choice. We already have some 670's here in Bulgaria, but I never touched them yet. Up to now I work more with Siemens relays, but just this week I have a substation with REF54x and RET521. But I consider to send some of our boys to pass training on 670's, they are the ABB future.

------------------------
It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[slavag]

Hi Iz5pl.
Welcome to the club of REF54_ and RET521.
I think about send my self to course of 670.
Yes, you are right this series is future of ABB (RED, REL, RET, REB and REG670).
Good luck with this substation.
Regards.
Slava.
( BTW, if you have some problem with REF54_ send me Q, my team have very good excperience with this relays, I work with this relay from 1999, we puted in services about 500 pcs)