Injection Testing

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Dave_PE

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One of my clients was strongly adivsed by his insurance company to preform injection testing on all circuit breakers over 400A.

Does anyone have any suggestions, concerns, tips, overall thoughts on this type of testing. It's a hi-tech manufacturing company that runs 24/7/365 and pretty much has no downtime. It's a 25 year old facility. None of the breakers have ever been turned off. The clients worried about the down time if a CB fails the test and doesn't reset. For the lost production of an hour of unplanned downtime, they could just about replace all the switchboards with new ones.

We are designing a major expansion for them in the few years or so, so new services will be designed to replace these, and they will have redundancy to allow testing, partial equipment shutdowns, maintenance, etc to occur without affecting production.
 
Dave, we assist a testing company at times performing these test at facilities. In most cases it is during a planned plant shut down and there are back up plans in case a breaker fails.

I have also been told by some that it is an Insurance Company requiring it be done. The Insurance Company's have a vested interest in safety and loss of revenue if something broke.

The only problem I can think of was a 4160v starter not coming back on line after the feeder breaker was closed, but this was just a control relay that had nothing to do with the testing

It would be nice if they could wait to your new design is in place though.

Roger
 
Coordination of the work, and as noted a back up plan is necessary.

Typically, we do testing after an IR scan, the reason for this is to take advantage of the shut down to repair replace defective (high resistance) components, in addition this time should be taken to perform additional testing, lubrication and cleaning of the distribution equipment.

We always ask how do you know it works if you do not test it. IMO electrical non-destructive testing should be completed on a regular schedule, many of our customers break their facilities into 3 sections and we test 1/3 of the facility at a set time every year
 
I've been involved from the standpoint of removing and reinstalling the breakers for the test guys. Around my parts, it seems like Factory Mutual Insurance is one of the heavyweights forcing this breaker testing. Another good reason to go with fused bolted pressure switches.
 
Ahhhh, But Fused bolted pressure switches, need service also. Not as intensive or time consuming but necessary non the less.
 
My plant is down for a week. One of the things they are doing is injection testing.

They are cleaning transformers and oil testing, adding 2 more pad mount transformers out side the plant, re building the main panel to handle 5 main transformers, and I?m sure there?s more.

But we do plant shutdowns on a yearly basses because there is so much that can?t be done with out losing production. The cost for my plant for every hour of unplanned down time $80,000 plus $60,000 for restarting and the loss of parts in the machines.

The good thing is twice a year most of our industry will shut down for 2 weeks. Our shutdowns are one in July and one in December.
 
The breakers are 25 years old and have never been tested and they are worried that some may fail testing? That is the most backwards logic I have ever heard, they should be worried about what may happen if the breakers fail to trip from a fault, causing equipment damage and possible injuries (Huge arc flash from long trip times). Not to mention the downtime they would have from a failed breaker during production.

The insurance companies have done alot of research on the finicancial benifit of power system maintenance, they know what they are talking about. Ask your client if they are afriad to go to the doctor because the doc may find something wrong with them, or if they just wait and see.
 
The Bell System companies had a policy requiring injection testing of all breakers over 100 Amps every 3-5 years. This policy was developed after a 100A feeder breaker failed to trip and the resulting fire destroyed most of a Central Office in Manhattan with many millions in losses. A lot of phones on Wall Street were down. The cost of testing was insurance against a repeat fire.

Have your beakers ever been opened? Their mechanisms could be frozen and never trip under any overload or fault. Most breaker instructions say to trip or operate the breaker at least annually to make sure it is not frozen or welded shut.

A good testing company could look at your system and devise ways of running temporary power to critical loads using short shutdowns. The testing set up costs would be high and there would be a chance of failure or failed tests.

Bottom line - if their product is really that lucrative that they can't take a shutdown, they will loose a lot more when they are out of production for weeks after one fire or short circuit burn down. But insurance will cover the burn down and operating budgets have to cover the maintenance.

Start with IR and other non-destructive tests to find possible problems.
 
Thanks for the tips. I met with the facility guys this afternoon and have a little more and also better information. The maintenance electrician says they have a two shut downs a year where they cycle all the major CBs a few times, the main 4000A switchboards are only 12 years old and they also once a year complete a full IR scan of all the equipment. So, things are in much better shape than I was initially advised. They do have a 45 year old mechancial plant fusible switchboard that does need to be replaced....although it looks well maintained.

So, the upcoming injection testing should not be an issue......thanks for the tips.
 
Minor point:

We had to troubleshoot a switchboard with breakers that were constantly tripping on ground fault (for no apparent reason).

Secondary injection tests by the switchboard mfr. proved the breakers were working perfectly.However,they still continued to trip under a load of 20% or less.

With primary current injection,we found the ct's polarity were improperly configured for this application.

This is just a minor comment.:)
 
If the GFP was tripping I would have checked EVERYTHING (if I was the manufacturer). Also we have had issues with some CBs where secondary injection showed the CB were acceptable, but they were not. Manufactures seldom tell you this.
 
Breaker secondary testing only tests the internal electronic circuit and the trip mechanism. Secondary testing does not check the entire current path (including external sensors). This is why many people believe that secondary testing only does not meet the NEC requirements for testing a ground fault SYSTEM.

Note: the test button on a GFCI is a full function test.
 
When we do secondary injection testing and there is GFP involved we suggesting performing Primary on the GFP portion of the device. Current path is tested for resistance with micro-ohm meter.
 
Ground Fault Tests

Ground Fault Tests

jim dungar said:
Note: the test button on a GFCI is a full function test.
Click to expand...

Jim - there may be some Ground Fault installation problems that cannot be detected by the test button or by secondary injection tests on breakers and ground fault relays. These usually occur on 3P4W circuits. (Test button on GFCI receptacle is a full test.)

For example, problems we have found:
-Wrong neutral CT polarity.
-Neutral CT connected to neutral bus on wrong side of tie breaker in Main-Tie-Main Switchgear.
-Circuit neutrals connected to wrong CT (Wired to CT for spare breaker mounted in same vertical section.)
-Neutral bus grounded downstream of ground fault sensor.

Ten years ago, about 30% of the GF installations we tested failed, usually for the above problems. I hope the pass rate has increased.

These are installation problems, not maintenance issues.
 
not maintenance issues
Click to expand...

When installers are lacking in the proper understanding of the systems the install, this becomes a maintenance issue, just corrected a problem from a 35 year old improper installation.


Neutral conductor not installed in CT with phase conductors.
ZEROSEQUENCECT2.jpg
 
rcwilson said:
Jim - there may be some Ground Fault installation problems that cannot be detected by the test button or by secondary injection tests on breakers and ground fault relays. These usually occur on 3P4W circuits. (Test button on GFCI receptacle is a full test.)
Click to expand...

The test button on a GFCI breaker is also a full function test. GFCIs are very specific protective devices and should never ever be confused with other ground fault protection (GFI, GFP, GFPE and GFR to name a few).

As I stated above, many people consider primary injection testing as the only acceptable method to meet NEC 240.95(C). This is because the test button and secondary injection on these devices only tests the internal circuitry and not the system.
 
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