IS Limiter Solution

[apbanal]

Hi to ALL,

Good day to engineers!

I just wanna ask your valuable technical inputs or experiences about the IS Limiter that we are planning to use as one of the solution to limit the fault current.

We are building a new substation with four (4) parallel transformers (115/13.8kV). The 13.8kV side are interconnected with each other (with Tie CBs) but not a ring configuration and one of the requirements is to limit the fault current at the 13.8kV bus below 25kA. Based on the study and considering also the impedance and voltage requirements, IS Limiter has been proposed to install on the CENTER TIE CB with two (2) transformers at one side and two (2) transformers at the other side. During fault condition on either on the buses, it will operate and separates the system into two. Thus, only two remaining transformers will supply the fault (which is less than 25kA)and then the protection relay will take charge of the fault to isolate.

My question are below:
1. ABB told us that IS Limiter is a cross flow equipment (operates in either direction), Does it mean that we can have a different trip setting on either of the directions? I mean a different settings on each directions? The reason i ask this is because we are installing first three (3) transformers, so two (2) transformers on the other side of the IS Limter and one (1) transformer on the other side of the IS Limiter. And the contribution of fault level on each of the four transformer at 13.8kV side is around 10kA. So, if there is a fault on one side of the IS Limiter (two transformers), it is around 10kA that will pass to the IS Limiter while if there is a fault on the other side (one transformer), it is around 20kA that will pass to the IS Limiter.
2. Doe the setting can be easily adjusted?
3. Any nuissance trippings encountered?

Im very sorry guys if my post is too long. I just wanna explain our set-up and hope you will understand the way i explain.

Am hoping for your inputs and experiences with this type of protection equipment.

Again thank you very much for the help in advance.

Regards,
apbanal

 

[ppedUK]

Have you tried asking ABB?

Your question around nuisance tripping amused me a little. You ask the question as if you can just pop out and reset the unit when it trips! They don't work like that, when these units operate, you have to replace components, it is not a circuit breaker!

 

[rcw retired EE]

We have applied the current limiting fuse/explosive bus link in a couple systems and have seen it used on one other. I have not heard of any issues but maybe there were no faults with enough current to trip the limiter. We have not heard of any false actuations. (But we do not operate or maintain the facilities, just design and build them).

Response of limiters to current is basically like any fuse or overcurrent relay. It responds to current regardless of direction.

Unlike current limiting fuses, limiters are usually unaffected by downstream devices in series that may be trying to also clear the fault. If the settings are selected properly and the system is operating as the engineer envisioned it, the limiter will trigger and separate the systems before downstream breakers try to clear the fault. Those are big "If's" that needs to be verified by the manufacturer.

 

[Kiribanda]

apbanal,
The IS limiter consists of MV current limiting fuses. Therefore to achieve the correct selectivity it is working on rate of change of current (di/dt) principle.
Since (di/dt) depends on X/R ratio at the fault location, I am in the opinion that unless you do a series of system studies at 13.8kV bus, it is difficult to
judge the location just from other data.

 

[krisys]

The application of Is Limiter needs extensive engineering. Additionally, there are limited suppliers in the market for this equipment. It needs one panel space (in width) of about one meter(i.e; say width of a 2500A breaker panel) and will be embedded as part of a swichgear line up, usually next to the bus tie.
The breaking currrent is not site adjustable. Hence the requirements shall be clearly specified during the engineering and ordering stage. Not to mention that is quite expensive.

 

[dfdt]

Just for your information there is another product in the market called triggered fault current limiter which is very similar to ABBs Is limiter but does not work on di/dt priciple and hence is much simpler to set,

 

[apbanal]

Thanks everyone for all your help and feedback. Very much appreciated. We did already a detailed studies for which part of the system the ISL will be installed which is now in series with the TIE CB.

I would just like to ask everyone if you guys used the ISL in series with TIE CB (just assume two 13.8kV system with TIE CB closed - proposed to have ISL in series w/ TIE CB), then you have a spot network load downstream. Some issues being raised now are during the time when the ISL will open (assume fault on one feeder), the 13.8kV system will have an unbalance voltage and may possible affect the tripping of network protectors of the other transformers in the banked network load.

I just wanna know if are there anyone (companies/utilities) used ISL already the ISL with network load on the feeders (downstream)? where did the ISL located? I am just try look for a references a part of our justification also since our company is new on this and not used ISL ever with spot network load downstream of the feeders.

Again thank you very much for all your help and feedback.

 

[slavag]

Hello apbanal.
You must ask ABB and explain to ABB all issues in your project.

As I know, possible make setting ( operation ) according to direction, we had some similar application on bus tie.
It will be build by special connections of CT's incomers and bus-tie.

Its a very good system, we have some install base of ISL ( about 20 pcs ). only once was maloperation ( some problem in commissioning ).

 

[apbanal]

Hi Slavag,

Thanks for your feedback. We did already discussed with ABB about our concern and they are still on the process of conducting the studies. For the meantime, we just want also to ask feedback from other companies who had already used the ISL. You mentioned that you had installed in a bus tie? I just want to know the type of loads in your feeder? The reason i ask because our set-up is we have a banked network transformers (4 units) to supply a certain load. Two (2) transformers from each side of the bus TIE CB (with ISL) for reliability purposes.

And also just wanna ask if your company is a generation or electric distribution?

Again thanks much for your help.

 

[slavag]

Hi.
in all cases it's hard load, 6.6 ( hard motor load ) -22kV switchgeras.
Factory, few cases are co-generation, generation buses.
usually bus tie is include some logic, for example, ISl of closed bus-tie operated only in case of both incomers are closed too.
\You can use really block of ISl operation by aux contacts.

 

[apbanal]

Hi Slavag,

Thank you very much for your help. Very much appreciated.