Breaker testing for insurance requirements

[Thedroid]

Insurance company wants us to test all of our unit substation secondary breakers. They all GE AK breakers 600 and 1200A. They have all been retrofitted with AC Pro trip units within the last 10yrs.

Should we use primary or secondary injection for the tests. I don't think primary is a good option. They were primary tested after retrofit, and I don't want to risk damage to the contacts because we don't have many spares, and new contacts are becoming hard to find and GEXPRO has very long lead times. I believe the secondary testing will satisfy the requirements without the risk of damage.

 

[NorthSlope]

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.

 

[DTR2011]

It's funny how we test protective relays for 500kV with secondary injection all of the time, but this concept is not considered OK for a LV breaker.

 

[Zogzog]

ANSI/NETA tesing spec, which likely your insurance company references, requires primary injection testing.

Side note, I stock those contacts, along with 5 million other obsolete switchgear parts.

 

[oldfieldguy]

Add me to the list for primary injection.

smallgreek-

I understand your comment, but we test the trip circuits and other aspects of those 500 kV breakers. We test the relays. We test the controls.

Low voltage power circuit breakers shove all these into one package. Primary injection testing gets the mechanism, the trip coil, and the trip unit.

old field guy

 

[dpmac]

I would go with primary. The contacts will survive fine. Doing primary testing on AK25/50 takes very little extra time if any then secondary. We have found many defective solid state trip units of various mfg doing primary. Many of them tested fine with the secondary test set. Parts for AK breakers are available everywhere.

 

[Zogzog]

OFG, don't forget the CT's. Usually the failures we find are a loose connection to the CT itself but CT's sometimes fail too. Secondary injection won't find those issues either.

 

[oldfieldguy]

Zog-

The electrical utility (big one) that I used to work for tested CT's on initial commissioning. After that, the only ones regularly tested were those used in high impedance bus differential schemes. That is, unless something went wrong.

Another big electrical utility I did contract work for had us test all the CT's on ALL their transmission equipment. We found a couple of CT's in OCB's that had shifted and now had a shorting path through the window, resulting in very low saturation voltages. One of these became the 'smoking gun' in an investigation following a scheme misoperation, tripping on a through fault when it quit contributing current. But that was two out of hundreds...

Then a major manufacturer with a German name had a problem with water ingress into external CT's on GCB's. We tested THOSE regularly because the water damage caused the saturation to go down, too.

old field guy

 

[Thedroid]

Thats good to know. I had thought that primary was the only way to test all the components, but that there was a risk of damage to the breaker. We're going to go through about 20 breakers of so, so it will be a good job. Contractor will be doing the testing, we'll be doing the lifting and the cleaning.

 

[Zogzog]

Careful with the "cleaning", many contractors clean breakers with a degraser and then add a spray lube (Technition in a can), this will break down the real grease in your breaker and cause some serious long term isues. Better to just leave it be.

Regardng damage to your breaker, there are some concerns about primary injection testing of your ST and INST trip functions. The best method is to test LT with primary injection and the other functions via secondary injection. This method is often refered to as "Primary injection with secondary verification"

 

[EEIre]

I recommend to find out the insurance companies testing specification and follow its requirments as a minimum.

Don't try and guess what they want

 

[Thedroid]

Insurance company just wants to see a sticker on the front of the breaker with a date less than 10 yrs ago.

 

[EEIre]

I'm in Europe so if it were me I would go for the routine tests as described in para 8.4 of IEC 60947-2:Low-voltage switchgear and controlgear Part 2: Circuit-breakers

These are:
mechanical operation
verification of the calibration of overcurrent releases (requires primary injection)
verification of the operation of undervoltage and shunt releases
dielectric tests
verification of clearances