Standards for Removable MV Circut Breakers
Standards for Removable MV Circut Breakers
(OP)
The power plant that I work for has the following type of MV Circuit Breakers Installed for 4.16 kv and 13.8 kv:Hyundai Vacuum contactor, HCA Series, Model: HCA62LD, 3P, 200A, 7.2KV, 100A fuse frame, Make: Hyundai Heavy Industries.
The problem is that in the last year we have had 2 coils of the circuit breaker burned up during the start up of the equipment after maintenance, not to the circuit breaker itself. The manufacturer says that it is caused by the circuit breaker not being fully attached to the bus before closing.
Question: Having worked in many power plants around the world with GE, Westinghouse and Siemens, I have never encountered a circuit breaker that would allow the circuit to be energized without positive locking onto the bus was confirmed by the breaker either through limit switches or local indicators.
I have looked for the manufacturing standards and for the requirement for circuit breakers to have positive indication of position, but can not find it if it exists. Help!
The problem is that in the last year we have had 2 coils of the circuit breaker burned up during the start up of the equipment after maintenance, not to the circuit breaker itself. The manufacturer says that it is caused by the circuit breaker not being fully attached to the bus before closing.
Question: Having worked in many power plants around the world with GE, Westinghouse and Siemens, I have never encountered a circuit breaker that would allow the circuit to be energized without positive locking onto the bus was confirmed by the breaker either through limit switches or local indicators.
I have looked for the manufacturing standards and for the requirement for circuit breakers to have positive indication of position, but can not find it if it exists. Help!






RE: Standards for Removable MV Circut Breakers
I think if the breaker is not fully retracted and locked, it can be considered to be in "Maintenance Position", therefore the provisions of clause 5.11 of IEC 62271.203 apply, which state that there shall be an interlocking mechanism that prevents the breaker from functioning while in Maintenance Position.
The only solution is to commission the local supplier who sold you the breakers to do maintenance for 1 year, and put all the liability clauses for remuneration in case of down time in the contract. During this year, make management aware that the breaker should be replaced with a more respectable one from GE, Westinghouse or Siemens as you mentioned.
RE: Standards for Removable MV Circut Breakers
That said, close and tripi coils fail all the time and are one of those things you should stock spares of. Coils are the most commonly requested part I get.
As far as the standard, it would help to know where inthe world you are located as different standards may apply.
RE: Standards for Removable MV Circut Breakers
Sometimes the electrical interlock is as simple as the position wherein the secondary connection plug makes up in conjunction with the position of the primary connections.
It is not unusual for the electrical interlock to make before the mechanical interlock has reached the proper location to allow a "close" operation. On some breakers, this leaves the mechanism in "trip free" mode, where the close coil triggers the mechanism but the linkage will not actually close the primary contacts.
In others, the mechanical interlock may prevent the linkage from moving.
In the second case, continued application of "close" voltage may burn up a coil.
That might happen in the first case, but most breakers have an "anti-pump" feature in the close circuit so that the close signal must be dropped and re-applied to get another close attempt. Improper alteration of the close circuit might do away with that feature, leading to a failure path.
Careful study of the electrical and mechanical interlocks is needed.
old field guy
RE: Standards for Removable MV Circut Breakers
· IEC 60470
· UL 347
· NEMA ICS 3
RE: Standards for Removable MV Circut Breakers
I don't know... he says "circuit breaker" and then gives "vacuum contactor". This might be some sort of retrofit.
I've heard of some horrible stories of less than adequate retrofits putting vacuum contactors into old air-magnetic breaker carriages without proper attention to interrupting capacity and coverage of all the mechanical and electrical interlocks.
One of those took several lives at a nearby power station some years back. That's why I worry about things like this...
old field guy
RE: Standards for Removable MV Circut Breakers