Trip Testing for MCBs

[macal]

I was interested in performing Trip tests for AC & DC MCBs for my customer. I will be injecting double the respective rated currents through the MCBs & check the tripping time against their type curves.

Is this method acceptable, quick & portable

 

[IQ Electrical]

I was interested in performing Trip tests for AC & DC MCBs for my customer. I will be injecting double the respective rated currents through the MCBs & check the tripping time against their type curves.

Is this method acceptable, quick & portable

Acceptable, slow and expensive.

 

[malcolmsanford]

And not very cost effective if you happen to damage the device. Not to say pretty dangerous if your going to subject a MCB and the tester to 20 times it's operating current (D type) in order for it to trip.

I would say that if there was a nice, quick, easy appliance that could test a MCB operation, the Janpanese would have invented ..................or IQ qould have.

 

[IQ Electrical]

And not very cost effective if you happen to damage the device. Not to say pretty dangerous if your going to subject a MCB and the tester to 20 times it's operating current (D type) in order for it to trip.

I would say that if there was a nice, quick, easy appliance that could test a MCB operation, the Janpanese would have invented ..................or IQ qould have.

Lol, too right!

Megger do a portable 'cart' type system but I'm sure it was around £12,000 the last time I enquired, even hire costs on this type of equipment, plus labour and shutdown can often mean simply replacing the MCBs can be a cheaper option!

 

[Knobhead]

Are you in the UK?
What rating are the MCB’s?
Why are you wanting to test them? They will already be ASTA certified.
You say you’re interested in testing them, is your client? I think he’ll soon loose interest when he finds the cost.

As to portable, get your Dr. Scrotes surgical support on order.

 

[IQ Electrical]

Are you in the UK?
What rating are the MCB’s?
Why are you wanting to test them? They will already be ASTA certified.
You say you’re interested in testing them, is your client? I think he’ll soon loose interest when he finds the cost.

As to portable, get your Dr. Scrotes surgical support on order.

Tony, mad as it seems, some insurance companies are insisting on these tests being carried out on large sites where their risks are high.

Apparently it's been an offshore platform requirement for some time too, maybe justifiably!

 

[Knobhead]

Our OP was asking about MCB’s.

I’ve assisted in carrying out primary and secondary injection testing for distribution equipment for 25 years. We always had independent companies to carry out the tests. Just testing the 11KV, 3.3KV and the 440V main breakers caused chaos. Testing every MCB on a large industrial site would be impossible!

 

[Engineer54]

I was interested in performing Trip tests for AC & DC MCBs for my customer. I will be injecting double the respective rated currents through the MCBs & check the tripping time against their type curves.

Is this method acceptable, quick & portable

What type of test equipement are you intending to use for these tests??

You only undertake such testing (Primary Injection) on MCCBs, VCBs, GCBs and the like, normally when commissioning a new Main Switchboard before it's initial energisation. ...Or during a major revamp, and maybe in some circumstances when an expensive CB is suspect of not performing!!, Most testing of such CBs would be via secondary injection testing. In all my years of testing and commissioning, i have never yet primary injected MCBs of any rating. I can remember testing a newly acquired MCCB injection test kit out on a 60A type 2 MCB , but that was for our own benifit, nothing to do with the installation being officially tested...


So yes you can test MCB's in the same manner, but as others have stated, it's a very expensive operation, even if you hire the test equipement, ....unless of course you have the use of such a test kit, and know the methodolgy in it's use.


One final point, there is nothing ''quick'' about undertaking any testing, or should i say, ...Their shouldn't be!!!!

 

[Knobhead]

there is nothing ''quick'' about undertaking any testing, or should i say, ...Their shouldn't be!!!!

Bank Holidays was our usual time for testing sections of the distribution system. So the manager would ask for volunteers to work, double time and a day in lieu would result in a stampede, if he mentioned primary injection testing there was a stampede in the opposite direction! It was a pain in the ar*e, interesting but a pain!

As you say no quick way around it.

 

[Engineer54]

Bank Holidays was our usual time for testing sections of the distribution system. So the manager would ask for volunteers to work, double time and a day in lieu would result in a stampede, if he mentioned primary injection testing there was a stampede in the opposite direction! It was a pain in the ar*e, interesting but a pain!

As you say no quick way around it.

Your right Tony, ...it is a real pain, especially when you need to disconnect large CSA cables or multiples of paralleled cables, from there breaker connections and wedging/holding them clear of the test connections. Preparations and reinstatement of Primary injection testing, is a very real time consuming exercise!!! Which is why Secondary injection testing is always the preferred method for ongoing/ future maintenance PPM scheduled testing!! And i think much more interesting....

 

[Engineer54]

Our OP was asking about MCB’s.

I've assisted in carrying out primary and secondary injection testing for distribution equipment for 25 years. We always had independent companies to carry out the tests. Just testing the 11KV, 3.3KV and the 440V main breakers caused chaos. Testing every MCB on a large industrial site would be impossible!

Those specialist companies make an absolute fortune, but are worth it, if they can set up your protection relays and controls for optimum performance. Seen quite a few that struggled to set up the control side of things mind...

When we have in the past sub contracted out this work module, i've always asked for a ''protection co-ordination study'' to be carried out an submitted by their design Engineer(s), prior to any work or commissioning being scheduled. This is checked thoroughly with the various manufacturers specifications and data, for omissions and compliance. Sometimes i can tweak here and there on some of the settings, if the discrimination in places is a little too fine, or overly wide.

 

[Deleted member 26818]

Cn't you just wire a plug Line to earh?
Always worked for me when finding MCBs.

 

[IQ Electrical]

Cn't you just wire a plug Line to earh?
Always worked for me when finding MCBs.

And a stopwatch for trip times?

 

[Deleted member 26818]

One bannana, two bannana.....

 

[cagedanimal2010]

not in to this sort of thing guys, could someone explain primary and secondary injection?
Many thanks.
Danny

 

[Knobhead]

not in to this sort of thing guys, could someone explain primary and secondary injection?
Many thanks.
Danny

Large ACB’s, OCB’s, VCB’s, Etc have CT’s to give a ratio of the current to the protection instruments. So a 200/5 CT will give 5A to the instrument when 200A is flowing through the main circuit. They also isolate the HV from the instrument.

So to set 200A O/L's at 125% with primary injection a current of 250A would be passed through the primary and the trip time measured. With secondary injection only 6.25A is needed. Further tests would be carried out at higher currents to check the current/time curve.
Now imagine primary testing a 1600A breaker, 125% = 2000A. I don’t even want to think of testing a 6000A breaker.

The primary injection equipment is hefty to say the least hence my reference to ordering a Dr. Scrotes surgical support. An absolute pain to connect up as Engineer said!

 

[1ManRiot]

MCB = mechanical circuit breaker? What is the difference to a regular 230V RCD?(new in the game)I presume testing them is a bigger deal than testing RCDs? We test RCDs on the random 230V supplies in trackside cabinets using a Megger IR/RCD tester.

 

[IQ Electrical]

MCB = mechanical circuit breaker? What is the difference to a regular 230V RCD?(new in the game)I presume testing them is a bigger deal than testing RCDs? We test RCDs on the random 230V supplies in trackside cabinets using a Megger IR/RCD tester.

MCB = Miniature Circuit Breaker.

The MCB is an overcurrent protective device whereas an RCD (Residual Current Device) only protects against earth leakage and must normally be used in conjunction with an overcurrent protective device or can be combined with an overcurrent protective device, known as an RCBO.

The test currents for RCD testing are typically much smaller (mA) than for MCB testing so the testing is much simpler and the cost of the equipment much less.