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Join Date: May 2011
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Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/21/2015 1:02 AM

6.6 kv VCB trips on first start up, of a 200 kw induction motor, without any trip indication.

After manual on/off it in test position, we insert it in service position and it get started smoothly.

It happened several times.

Please suggest possible reasons.

One of them might be malfunctioning of breaker mechanism.

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#1

Re: Vacuum Circuit Breaker trips on first start, without any indication

06/21/2015 10:52 AM

You might go to the movies and ask people as they enter the theater what the problem might be.

You could read the operator's manual and search for a clue.

You could ask the VCB supplier for enlightenment.

You could pray for divine intervention.

You could try another VCB.

You could ask a qualified electrician to solve the problem.

You could search the internet for help.

I found 240,000 possible sites to help those such as yourself.

Vacuum Circuit breakers trouble shooting

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#2

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 12:32 AM

Really hard to say. Check the motor and the VCB separately, chances are one of them is to blame.

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#3

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 1:15 AM

Please check the design also.

Regards

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Participant

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#4

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 2:53 AM

I were facing this problem too. it happened most of the time during processing then i take help from ijeee-apm based on electronic journals. i suggest you to do the same.

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#5

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 4:12 AM

Have you checked that there is a time delay to allow for starting current?

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Commentator

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#7
In reply to #5

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 6:30 AM

In absence of adequate starting time delay, it would trip on O/C fault. Actually it does not trip, it simply stops, without any indication. Breaker get Off within 2 seconds.

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#6

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 6:22 AM

We know nothing about the load his motor is driving. For a pump or fan the shaft angle won't affect starting torque. But for a reciprocating machine like compressor, crusher, etc., shaft angle at startup can have large influence on torque and inrush current.

Try taking note of shaft angle before each start and see if there's a pattern.

Here's a good article on the general subject: https://www.industry.usa.siemens.com/drives/us/en/electric-motor/anema-motors/specification/Documents/trouble-shooting-induction-motors.pdf

Good luck!

Zvi

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#8

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 7:06 AM

Dear Mr.satendrakumart,

My opinion is the problem could be with the Spring - where STIFNESS is a main criterion, and it is over compressed or stretched.

Pl. check up this aspect.

DHAYANANDHAN.S

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#9

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 8:13 AM

You give us no good way to give you help since you do not give the manufacturer or model number. I have seen breakers doing this many times and will guess at the type of breaker and a possible solution. If the breaker is a medium voltage (5-25KV) metal-clad switchgear, then the probable solution is in the racking mechanism. Most manufacturers use a series of sliding pieces in the racking mechanism and levers with rollers on the sides to detect whether the breaker is in the proper position or not. If one of those rollers does not fully drop into the slot provided for it in the racking mechanism it can be in either a trip-free position or nearly in that position so that when the breaker closes the mechanical forces cause a trip-free condition which is what you are describing. Racking the breaker to test position and closing it simply frees up the rollers and then in the fully racked in position it will function correctly when it did not before. If it is a breaker of the 3 manufacturers that I am most familiar with it is not necessary to rack it in and out to correct the problem. A simple sharp blow of the hand on the lower right hand corner of the breaker will cause the roller to drop into place and the breaker will close correctly. The ultimate solution is proper maintenance of the breaker involving cleaning and lubrication and adjustment of the racking mechanism and interlocks. How long has it been since the Vacuum bottles were tested?

Although the slot is usually only about 1/8 inch between the breaker and side panel, it is possible to see, using a flashlight the roller and slots of the interlocks and observe that they are not properly seated in the correct position.

The fact that no targets were set on the protective relays says that this is not a case of overcurrent or weird fault. It is most probably mechanical and it literally happens all the time on poorly maintained equipment with personnel that are not trained by people knowledgeable about the equipment.

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#10

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 1:20 PM

One of the reasons is a failure to discuss the problem over the telephone with the equipment supplier. Eliminate that one. First.

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#11

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/22/2015 6:38 PM

All medium and high voltage CB interruptors have internal interlocks than when activated, the closing action is impaired. Normal interlock operation has to be in the proper operative sequence for the breaker to close. Either the interlock operation has been tampered with or, it's faulty from factory. Consult the factory representative for interlocking settings and sequences. These devices are digitally logic operated and if the tripping device is not adjusted properly or it's not within required tolerances, the breaker will not close. The load recognition parameters have to be correct before they initiate the closing action. Also, if the breaker has been equipped with other configuration options, most of the options have an interlocked sequence that communicates with the main closing or tripping device. Sometimes, if one the mechanical latching mechanisms is dislodged or out of sync, the breaker will not start and/or safety trips to avoid further damage. Again, get a factory service to check for proper operation cycling and interlocking. Also, check the locked motor starting current against the tripping device settings for a possible load current/timing adjustment mismatch.

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#12

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/23/2015 9:43 AM

If it is failing in the automatic mode operation but not in the manual operation mode, then the system logic is not being satisfied. (Process Discharge pressure? Lube oil pressure? Start sequence mismatch? or?)

If failing in both manual and auto mode:

Loose terminal connection on any device in the stop circuit.

Loose terminal connection on the overload relay interlock.

Incorrect timer setting in the start circuit.

Bad stop button contact.

Control voltage level dropping below coil hold-in threshold during starting sequence.

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#13

Re: Vacuum Circuit Breaker Trips on First Start, Without Any Indication

06/28/2015 2:32 AM

Dear you should check tripping circuit properly. Maybe something is causing continous supply to trip coil. Or ypu should also check no voltage interlocks usually practised in 200kw motors feeders. How can u say vcb is having problem. Have u tried replacing it with other vcb and then concluding this vcb problem.

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4wsilver (1); dhayanandhan (1); Geoffrey36 (1); jack of all trades (1); jbourass (1); lyn (1); Niket (1); PWSlack (1); satendrakumart (1); SHOCKHISCAN (1); souabhpahwa (1); wirestan (1); Zvi (1)

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