MCCB vs HRC overcurrent protection

[baldsparkies]

Can you adjust the time lag coefficient on the MCCB? A small mains blip shouldn’t cause nuisance tripping.
What’s it going out on over current or under voltage? I had a problem with U/V on an ACB a few years ago, 2ms delay solved the problem.

Many thanks Tony,

I will have a look at the calibration settings when on site and take it from there.
Some units have 2 dials covering trip threshold marked In and Io, others are even more flexible with 3 dials, the third covering Isd which I believe is the prospective fault current.
i usually multiply the nominal rating set on dial 1 Ir by the Io and Ir calibrations.
Any other info would be much appreciated, but my guess is they have been gradually increasing loadings, and as a result a loss of power, even though momentary would mean a sudden surge through the device which would re instate under full load is causing the tripping. So hopefully re calibration could well be the answer. They also need regular checks on the system to ensure max demand criteria remains within the design parameters of the install, but you would think that would be common sense.

 

[Knobhead]

That old chestnut again, has anything changed? No! Well, we added this and that and oh, that other bit, but nothings changed! (Well it’s only bits of stuff).

A different scenario but I had to up rate an ACB from 800A to 1200A and add a 3rd feeder cable etc. But nothing had changed! Someone sneaked the 300HP compressor in under the cover of darkness!

 

[baldsparkies]

Aint that the truth Tony, Often with the bigger companies, they have various contractors adding here and adding there with no one keeping check on who's doing what, where and why. I remember on one site Red phase had 80 amps Yellow 260 and Blue 140. But it happens all the time, at least on this one the phases are pretty well balanced so no issues there. Thanks for the responses to all.

 

[gaz101]

Is it possible to add an alarm
To call maintenance if the mccb tripped

 

[baldsparkies]

Is it possible to add an alarm
To call maintenance if the mccb tripped

Already on the UPS and connected to the network Gaz, Hence the 2.30 in the morning call out (Not nice)

 

[Knobhead]

Is it possible to add an alarm
To call maintenance if the mccb tripped

It’s a bit late by then, the problem has to be stopped before it starts.

Quote the plant manager “did you know the main breaker’s tripped again?” Me “yes the fu**ing kettles stopped boiling and it’s bl**dy dark in here!”

Discrimination and trip settings are a nightmare when you get to 400A+ breakers, as Baldsparkies obviously knows. Both time and current are adjustable so it’s easy to alter one setting on the local breaker and move the problem one step up the ladder.

 

[baldsparkies]

Don't worry Tony, I shall be taking some 6" nails up with me.

 

[johnboy6083]

Aint that the truth Tony, Often with the bigger companies, they have various contractors adding here and adding there with no one keeping check on who's doing what, where and why. I remember on one site Red phase had 80 amps Yellow 260 and Blue 140. But it happens all the time, at least on this one the phases are pretty well balanced so no issues there. Thanks for the responses to all.

Very true mate. the sites im working on, nobody has a clue whats in them and what isnt. half of them are not even fully functional, and trying to find out anything ie teste results ect, is a nightmare.

at the moment, they have employed another frim to carry out PIR's, but they are also testing our firms half finished installs, failing them, as they are not complete, and ive still got to test them when they are fininshed. i reckon that the firm will bill for remedials, and when thhey turn up to carry out the work, wuill find it all kosher, cos we would of finished, and earn for nout.

its a shame that electrical safety isnt a priority.

 

[Knobhead]

its a shame that electrical safety isnt a priority.

The eternal cry of the maintenance / industrial electrician.

 

[johnboy6083]

ill try and get some photos of some of the gear i see. its ancient, but sill works. in one place there are 2 massive generators, one english electric, and one blackstone. they have DC generators at the end, on the same shaft, which i guess are being used as exciters. a small petrol engine acts as the starter. its a shame, but both of these beasts are no longer operational. the panel for the blackstone genny must be 50's, and still in good nick. ive opened some of the cubicles, just tp noes at the wiring, and its the neatest ive ever seen.

 

[baldsparkies]

Would be interesting to see Johnboy. The fact there still operational is testament to the quality of build with the old stuff,
I mean look at me. Born in 1953 and still going strong, keep tripping over the zimmer frame though.

 

[johnboy6083]

i was born in 87, and keep breaking down! lol

 

[Knobhead]

I was heart broken to take this out and replace it with modern crap. Just a pitty I didn’t get a picture of the front, polished black slate

View attachment 5718

We even had a mercury arc rectifier.

Meet Rodney

View attachment 5719

Used to scare the living daylights out of me at first, but then I got quite fond of it. To watch it working was like watching a living thing.

 

[Engineer54]

Come-on Tony, ....So what's this plant panel actually a part of?? Spill the beans...lol!!!

 

[johnboy6083]

that looks like a work of art. im actually an industrial pervert, but half the tiome i dont know what im looking at!