Is limiters

[davva]

We are investigating the use of Is limiters for a marine platform. The Is limiters required are to be installed as part of a 50kA, 11kV switchboard.

I have only managed to find ABB as a supplier so far. Are there other manufacturers out there that meet these requirements?

I would also be interested to hear peoples views on the use of Is limiters, e.g. design problems or nuisance tripping (worse still failure to trip!)

 

[slavag]

Hi Davva.
ABB Germany is Is limmiter supplier only.
Other companies haven't something like to this,
Company, i thisnk Clip, provide fuse, but it's not Is limmeter, diff. is Is limmeter operated according to dI/dt.
In our area we have about 10psc, work w/o any problems many years.
Good support end team.
Best Regards.
Slava

 

[HVmariner]

Hi Davva!

I've studied this when working for a company concurrent to ABB in the electrical propulsion business.

I've been informed last year by Schneider Electric (Grenoble-France) of developments being made to propose the same type of device as the ABB Is-limiter. If you need, I could find contact names there in my archives.

If fact, their is no particular problem in using this for marine applications, ABB have been doing this on numerous veseels.

The main reason why this was not implemented on the project I've been working on is that the network was finally changed from 6.6 to 11 kV.

Just a few points to be care:
- what happens when the equipment trips: impacts on your switchboard (destroyed? reparable? still in operation? facilities for repairing,...)
- cost in very high
- will your switchboard need be type tested again in regards of class and IAC requirements?

Hope this helps.
Regards,
HVmariner

 

[davva]

Thanks both.

I believe Schneider are using the Clip technology which slavag has referred to.

My understanding of the device is that it is contained with a certified switchboard, i.e. it is a 50kA limiting device within a 50kA switchboard.

If it trips (spurious trip) then this is o.k (apart from the loss of multiple services which may be a problem but not in terms of safety of those in immediate vicinity of the switchboard).

However, if it fails to trip on a short circuit then you better hope and prey you are not in the same room as the switchgear. That is to say the device should be should so reliable that this situation will never happen.

 

[HVmariner]

Davva,

I've just find more information on Schneider solution (see doc. attached): It really looks like the ABB Is-limiter system.

Regarding installation of the ABB Is limiter, we had investigated different solutions:
- a completed seperate cubicle as you discribe,
- just purchasing the different parts as loose parts, and installing these in our switchboard's supplier.
Different solutions are possible and can be discussed with ABB.

Rgrds,

 

[slavag]

Hi Davva.
What HVmariner saied.
ABB have a lot of different solutions.
You have discussed with ABB Calor Emag ( Germany).
It's really professional team.
Good Luck.
Slava

 

[waross]

a completed seperate cubicle as you discribe

Beware, if the limiter fails to clear a switchboard fault, it won't matter how well protected the limiter is. The smoke and fire will be at the switch board.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[slavag]

Hi Bill.
separate cubicle ..not for protected the limiter .
On this year, our company will install two such limiter.
In one case it's separate cubicle, becouse it is additional to the 25 years old switchgear and fisically is not enough space.
In second case ABB suppliy Is limiter as loose material and switchgear supplier install it in the original cubicle.
Regards.
Slava

 

[waross]

Thanks, Slava.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[hvcad]

We have worked on a number of installations were Is-limiters have been installed. The ABB tripping logic is robust as it is based on instantanous i(t), di/dt measurements. One concern is the impact of capacitor switching - this may cause a high di/dt leading to tripping of the unit. Generally this happens when pf correction capacitors are installed after the Is limiter and the trip settings have not been re-evaluated. Note aware of any cases where a limiter has failed to trip.
In a system with NERs earth fault levels are limited and the limiter does not need to operate for an earth fault. For a L to L fault, two phases will see the fault - but only one phase has to trip - so there is some inherent redundancy in the design. Same applies for three phase faults - only two of the three limiters needs to operate to limit the fault current.
You might find these papers useful:-

http://www.ipst.org/techpapers/2007/ipst_2007/papers_IPST2007/Session13/82.pdf

http://www.ipst.org/TechPapers/2005/IPST05_Paper026.pdf

Dr K S Smith
Mott-MacDonald, Power Systems Division
Glasgow, Scotland.

 

[hvcad]

oops, got one of the links wrong, should be:-

http://www.ipst.org/TechPapers/2005/IPST05_Paper038.pdf

Dr K S Smith
Mott-MacDonald, Power Systems Division
Glasgow, Scotland.

 

[davva]

HVCAD. Many thanks for the info.