VCB EXPLOSION
VCB EXPLOSION
(OP)
To All Experts,
Specs of the VCB are below;
VD4 ABB - 17.5 KV/630 Amperes/ 25 KA
Our plant is diesel/bunker C power plant supply the small island. The unit is status is on going commissioning and it is synchronize to the grid.
The diesel generator rated 13.8 KV and 2.1 MW capacity connected to generator breaker and bus then, taking off to the feeder line to utility network.
It were happened 4 times explosions, below are the sequence of events;
1. First , the DG was synchronized and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We neglect to check the internal of VCB and replaced it nee VCB and PT fuses.
2. Second , again the unit is synchronized and and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We neglect to check the internal of VCB and replaced it nee VCB and new PT ans fuses again.
3. Third , again the unit is synchronized and and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We check the VCB all replaced then we found out the the caused of flashover and switchgear explosion is from the VCB. And, why that the only damage and failed bottom contact of the VCB is only phase B among the 3 and Phase A & C is is not damages.
My questions now, is what would be the cause of series of failure of the VCB.
Before we instaled was the insulation resistance in the bottom is 200 Mega ohms respectively while the top terminal is in 3 giga ohms.
Please help.
Specs of the VCB are below;
VD4 ABB - 17.5 KV/630 Amperes/ 25 KA
Our plant is diesel/bunker C power plant supply the small island. The unit is status is on going commissioning and it is synchronize to the grid.
The diesel generator rated 13.8 KV and 2.1 MW capacity connected to generator breaker and bus then, taking off to the feeder line to utility network.
It were happened 4 times explosions, below are the sequence of events;
1. First , the DG was synchronized and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We neglect to check the internal of VCB and replaced it nee VCB and PT fuses.
2. Second , again the unit is synchronized and and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We neglect to check the internal of VCB and replaced it nee VCB and new PT ans fuses again.
3. Third , again the unit is synchronized and and run 2-3 hours and switch gear explosion and DG tripped with the indication of 51V and 87G.
After explosion , my team checked and it was found out the the PT fuse blown and flash over evidence observe in the PT and VCB.
We check the VCB all replaced then we found out the the caused of flashover and switchgear explosion is from the VCB. And, why that the only damage and failed bottom contact of the VCB is only phase B among the 3 and Phase A & C is is not damages.
My questions now, is what would be the cause of series of failure of the VCB.
Before we instaled was the insulation resistance in the bottom is 200 Mega ohms respectively while the top terminal is in 3 giga ohms.
Please help.






RE: VCB EXPLOSION
See [for instance]:
file:///C:/Users/win7/Downloads/302233.pdf
It is not exactly your case but it may draw an image.
RE: VCB EXPLOSION
RE: VCB EXPLOSION
Regards
Marmite
RE: VCB EXPLOSION
RE: VCB EXPLOSION
Regards
Marmite
RE: VCB EXPLOSION
RE: VCB EXPLOSION
Have these failed breakers and the switchgear gone through the required AC dielectric tests ?
There should be a dielectric test voltage level for a 1 minute or 10 sec test recommended by the manufacturers of both the equipment, else you can use voltage levels at 75% of specified design test levels in IEC or IEEE, whichever standard it was manufactured to. In IEEE world, we can refer to NETA in absence of manufacturers data.
Insulation resistance test (most at 10kv DC max) does not stress the dielectric above the nominal operating level, so equipment can still fail once subjected to normal voltage stress and accompanying spikes on the system.
It is odd that the same phase failed / flashover. There should be some physical oddity with regards to Phase-B compared to the other phases, like smaller ground clearance ... anything, else there is an even chance that if these are substandard breakers they could have failed on other phases. Lucky that it was not a phase-to-phase fault, else damage would be much more.
Flash over are easily cleaned by blasting frozen CO2, if anyone qualified over there.
RE: VCB EXPLOSION
RE: VCB EXPLOSION
Before carrying out any operations, always make sure that the
operating mechanism spring is discharged and that the apparatus is
in the open position.
To lift and handle the circuit-breaker, proceed as follows (fig. 2):
– use a special lifting tool (1) (not supplied) fitted with ropes with
safety hooks (2);
– insert the hooks (2) in the supports (3) fixed to the frame of the
circuit-breaker and lift. Put the hooks (2) into the support holes (3)
according to the type of apparatus (see table);
– on completion of the operation (and in any case before putting into
service) unhook the lifting tool (1) and dismantle the supports (3)
from the frame.
During handling, take great care not to stress the insulating parts and
the terminals of the circuit-breaker.
RE: VCB EXPLOSION
The VCB is properly handling in lifting, the main issue on this , why the VCB explode when synchronize after 3 hours?
RE: VCB EXPLOSION
Relays are my thing; whenever something goes wrong on our system that might involve relays I always go after everything that might possibly have gone in the relays and let other influence the investigation in other directions. Then when I get to the final report and the principal cause turns out not to be relays I've got a certain additional credibility simply because I didn't try to point the blame elsewhere in the beginning.
The working theory of what went wrong always has to be that which best explains everything that happens and doesn't require any "ifs, ands, or buts". A beautiful theory that covers everything except for one fact is of no use at all, you have to have the a working theory that explains everything, regardless of where it might point. In the initial stages of an investigation that working theory can change frequently. You can have a great theory of what happened and discover one new fact that makes you start all over again. You can't ever be defensive about what might have happened, it is what it is.
RE: VCB EXPLOSION
Your photograph does not support this - someone has tilted the breaker using the primary disconnect. This is exactly what the OEM says to avoid.
RE: VCB EXPLOSION
Please see pics.
RE: VCB EXPLOSION
RE: VCB EXPLOSION
RE: VCB EXPLOSION