Molded case breaker testing, is removing conductors necessary

[kwikcoupe]

I am a facilities technician and this year are going to be performing the sites breaker testing. The large frame rack able breakers will be removed from the gear to be tested on a bench. The small frame 800 amp molded case breakers we have a question. We gave multiple vendors the chance to bid on the project based on a predetermined NETA testing SOW.

Some of the vendors said they were going to remove the building conductors from the breakers to perform testing in place then re-land the conductors and torque. Other vendors said they could use a stab in style cable that inserts into the Allen head of the lug and test across the breaker with the building conductors still landed and the breakers on either end of the conductors open or unracked based on design to isolate the breakers. I did not see in the NETA guidelines either method to be preferred or suggested as a best practice. I have never personally performed these tests but we do need to select a contractor. I can not say if the gear may have voltage transformers or other equipment tied to the system.

Can anyone suggest or explain the benefits either of these methods carries. From what I can tell, to keep the conductors landed the procedure involves less time which then costs less in manpower. It may be less intrusive since you are not touching the conductors. On the other side, complete isolation of the breaker cold be performed with removing the conductors but at nearly twice the cost based on time involved.

We are talking about a few hundred of these breakers to be tested in a few days time. If anyone could provide insight that would be very helpful.

Thank you
Michael

 

[don_resqcapt19]

Is there enough extra length to reterminate the conductors? It is my understanding that you should cut off the part of the conductor that was in the lug, strip back the installation and then re-land the conductor.

 

[petersonra]

Is there enough extra length to reterminate the conductors? It is my understanding that you should cut off the part of the conductor that was in the lug, strip back the installation and then re-land the conductor.

can't do that very many times before you run out of conductor. maybe crimp on some pin connectors?

 

[jumper]

Calling Zog or Brian John,,,,ring, ring.

 

[zog]

Electronic trip or thermal magnetic on your MCCB's?

 

[weressl]

Is there enough extra length to reterminate the conductors? It is my understanding that you should cut off the part of the conductor that was in the lug, strip back the installation and then re-land the conductor.

You are presuming that the connectors are box-lug and not compression, bolt-on type.

 

[kwikcoupe]

These are thermal magnetic trip units. We have mechanically crimped lugs on the wire ends that are through bolted through the buss.

 

[weressl]

These are thermal magnetic trip units. We have mechanically crimped lugs on the wire ends that are through bolted through the buss.

Bingo, no problem in unbolting and reconnecting those.

 

[kwikcoupe]

Time and cost is the problem. Over a 4 day period they would have hundreds of these connections to make. That is the performance of many individuals. One contractor wants to remove the conductors to test, the other says they can stay. Both claim to be using NETA standards. The bid to remove is much higher based on this manpower requirement. We aren't sure if this practice necessary or more of a best practice consideration. I can't find information saying either method is preferred or why hence the original post.

Thanks for the help

 

[GoldDigger]

Time and cost is the problem. Over a 4 day period they would have hundreds of these connections to make. That is the performance of many individuals. One contractor wants to remove the conductors to test, the other says they can stay. Both claim to be using NETA standards. The bid to remove is much higher based on this manpower requirement. We aren't sure if this practice necessary or more of a best practice consideration. I can't find information saying either method is preferred or why hence the original post.

Thanks for the help

Will it be as easy as the vendor implies to open or unrack breakers on both sides of the unit under test? Or will they still end up removing conductors on a large fraction of the breakers they are testing? If that happens, will they still hold to their quoted price or will it actually be T and M?

 

[kwikcoupe]

Its a hard bid quote, the distribution side would be unracked or removed, the load side breaker will be in the open condition during testing to isolate the breaker under test. The only breakers that do unrack are on the distribution side. All others are part of the equipment assembly and tied together with buss or flexible conductors.

 

[zog]

Time and cost is the problem. Over a 4 day period they would have hundreds of these connections to make. That is the performance of many individuals. One contractor wants to remove the conductors to test, the other says they can stay. Both claim to be using NETA standards. The bid to remove is much higher based on this manpower requirement. We aren't sure if this practice necessary or more of a best practice consideration. I can't find information saying either method is preferred or why hence the original post.

Thanks for the help

So if they leave the cables connected how do they do an insulation resistance test?

NETA doesn't offer much guidance on testing MCCB's, they punt to several other references, the best standard to follow is NEMA AB-4. We always remove MCCB's (And cables) to test per this standard, so if I were you I would go with the bids to remove OR consider not primary injection testing them at all. Most problems in a thermal magnetic MCCB will effect contact resistance. Of course a primary injection test is ideal but in situations like yours your maintenance dollars could be better spent in other areas.

 

[kwikcoupe]

So if they leave the cables connected how do they do an insulation resistance test?

NETA doesn't offer much guidance on testing MCCB's, they punt to several other references, the best standard to follow is NEMA AB-4. We always remove MCCB's (And cables) to test per this standard, so if I were you I would go with the bids to remove OR consider not primary injection testing them at all. Most problems in a thermal magnetic MCCB will effect contact resistance. Of course a primary injection test is ideal but in situations like yours your maintenance dollars could be better spent in other areas.

I'm sorry if I mistake what you are saying, but the insulation resistance test (megger) is forbidden by the company I work for on anything after the entrance cable. they had problems performing the test in the past and decided to remove it from the testing guidelines. If this is not what you are referring to I'm sorry. Thank you for the help. These technical aspects of the trade are fascinating but unfortunately I know nothing about them. Its great having a resource like this to gain the information needed.

 

[zog]

I'm sorry if I mistake what you are saying, but the insulation resistance test (megger) is forbidden by the company I work for on anything after the entrance cable. they had problems performing the test in the past and decided to remove it from the testing guidelines. If this is not what you are referring to I'm sorry. Thank you for the help. These technical aspects of the trade are fascinating but unfortunately I know nothing about them. Its great having a resource like this to gain the information needed.

Why would someone "forbid" Megger testing? It is part of just about every test procedure for every piece of equipment. Perhaps they had trouble before because they used that low big testing company that leaves the cables connected to the breakers while testing them.

 

[kwikcoupe]

Why would someone "forbid" Megger testing? It is part of just about every test procedure for every piece of equipment. Perhaps they had trouble before because they used that low big testing company that leaves the cables connected to the breakers while testing them.

Somehow, on a site different than ours, in a time long long ago, that megger test found its way into a controls circuit and fried many pieces of equipment. That's about all anyone talks about it and that may be all anyone really knows about it. In our market minutes of downtime costs thousands of dollars and having a system offline after the testing period during repairs would have cost a lot in revenue. In the SOW it specifically addresses that no megger testing is to be performed.

 

[petersonra]

Somehow, on a site different than ours, in a time long long ago, that megger test found its way into a controls circuit and fried many pieces of equipment. That's about all anyone talks about it and that may be all anyone really knows about it. In our market minutes of downtime costs thousands of dollars and having a system offline after the testing period during repairs would have cost a lot in revenue. In the SOW it specifically addresses that no megger testing is to be performed.

years ago (before my time) at the place I worked someone did exactly this and fried a bunch of instruments.

after that it was always specified that megger testing was only for power circuits.

 

[templdl]

So if they leave the cables connected how do they do an insulation resistance test?

NETA doesn't offer much guidance on testing MCCB's, they punt to several other references, the best standard to follow is NEMA AB-4. We always remove MCCB's (And cables) to test per this standard, so if I were you I would go with the bids to remove OR consider not primary injection testing them at all. Most problems in a thermal magnetic MCCB will effect contact resistance. Of course a primary injection test is ideal but in situations like yours your maintenance dollars could be better spent in other areas.

To my knowledge NETA doesn't set the testing standards, they adopt exsisting testing standards that are commonly done in the industry to be used by their members. There should be no magicak test that NETA has in addition to some who is not a NETA member other that you should be reasonably assured that a NETA member will conduct all of the tests as applicable as adopted by NETA.
That's what NETA brings to the party in my opinion. A reputable nonmember testing agency should offer a comparable service.