Relays at the breaker or in the control house?

[Sideswiper]

Does anyone have some good references about why it is better to have relays in the control house than at the breaker?

I figure having it in the control house is better so that emergency maintenance on the breaker can happen safer and faster during rain or other inclement weather. Also I have doubts about microprocessor relays performing well in outdoor cabinets which could easily be exposed to water (especially if the cabinet isn't closed properly) or to extreme temperatures.

But construction sometimes sees the control house as an unnecessary cost (like when upgrading an old substation to microprocessor relays) so I'll need to make my arguments tighter. Or maybe I'm being overly concerned?

 

[slavag]

Hi.
You don't found some reference on the issue.
Your reasons are right reasons.
From other hand, GE show connections of the digital relays in the field.
From my point of view, protective relays must be in the control room.
Best Regards.
Slava

 

[racobb]

It is usually the old chocolate vs. vanilla thing and depends on the philosophy of the design engineer. There also could be specific application issues, but can't think of any right off. Some do not like extending the breaker control circuits to the house and prefer to keep them as a local function.

The micros we have in outdoor breaker cabinets have seemed to fair really well to date, but we always have heaters in the cabinets.

Alan

 

[jghrist]

Having a climate controlled space for the station battery is an advantage of having a control room.

The addition of a wireless transceiver to breaker control cabinets with microprocessor relays could help with some maintenance during inclement weather. Some things could be done with a laptop computer in your truck.

 

[dpc]

New arc-flash safety regulations in the US make the breaker-mounted relays less attractive.

I don't often see transformer protection relays located outside at substations, but feeder breaker relays outside is not uncommon. I'd not be too concerned about the microprocessor relays as long as the enclosures are kept non-condensing via space heaters.

This is also often a function of local climate.

David Castor

http://www.cvoes.com

 

[Sideswiper]

Thanks for the responses, pro or con!

I'm a relatively new protection engineer (three years). As we replace aging equipment and upgrade substations, there is often a discussion of whether we should put in a control house. It's good to see a few opinions on the matter.

 

[stevenal]

Put in the control house, and make it big. The only problem with control houses, is that the ones put in by the previous engineers are seldom big enough.

 

[cranky108]

I saw something simular, as reclosers vs breakers.
The electronic reclosers work well, as long as someone dosen't leave the doors open. However, each recloser contained a battery, which needed maintenance, and replacment every 5 years.
The building allows more space, and easer access where more equipment is needed, such as for transmission panels, and relays, and comm gear.

On small substations it maybe possible to do without a building, but it may take a dozen or more boxes to do it.

 

[rcw retired EE]

Modern control buildings are not "buildings" they are pre-fabricated and wired enclosures. That is much less expensive way to go.

In the US, tax treatment is different between a building and a piece of equipment. Buildings have a 20-30 year write off and pay property taxes, permits, etc. Equipment is written off much faster and may pay less property taxes be easier/faster to get building permits.

A small substation can afford a control enclosure with room for expansion when it can’t afford a building.

One advantage of placing a microprocessor relay in the breaker or transformer control enclosure is it can act as a remote I/O for other alarms and status without having to pull more wires, assuming there is a communication link. For example, the relay might monitor SF6 pressure, spring charge state, operations counts, control box temperature, local/remote selector switch position, disconnect switch status, transformer tap position. Control power status, etc., etc. Wiring is all in the CB panel with a fiber back to a SCADA communication hub. Not much field wiring.

Things to think about as you decide chocolate or strawberry or tutti-frutti.

 

[scottf]

If the relay is put at the breaker/transformer, it seems the burden placed on the CT (due to lead-length) would be greatly reduced, thus improving protection performance, etc...

 

[bacon4life]

When moving the relays to the breakers where do things like bus protection and transformer lockouts go?

On breaker and a half schemes it would require CTs from one breaker to run to another breaker. Right now most of our breakers are fairly interchangeable, so it would require a different spare parts stratagy if each breaker was customized with relays, test switches and interconnected lockouts.

Living in western Washington, having instrumentation technicians working in the rain/weather would be pretty big change.

 

[racobb]

As jghrist said, I also like for the station batteries to be inside a climate controlled space.

One must also always look at the application to determine what is the best overall solution.

I always prefer to have an indoor switchboard with the diffs and station OC protection/lockouts there and leave the feeder breakers completely local with respect to CT's and relay control circuits. Why....because that is my preference up front. Having said that, my most recent station did not allow for that....so it can depend on the application as well as the budget.

But with all else being equal, it still most often boils down to individual design preference.



Alan

 

[odlanor]

Its is common in distribution subestation without any kind of house , with control and protection installed at CB bay.

 

[marks1080]

Eventually you will start to see all relays mounted on or near the breakers in the yard. The holy grail of P&C right now is to eliminate the relay (control) building. A lot of time/money/resources are being poured into this right now. GEs new Brick device is the first major step towards this. Combined with IEEE 61850 the benefits are starting to outweigh the cons. The utility I work for is already experimenting with this concept, installing 'C', in addition to 'A' and 'B', protections on some elements as a test phase. I think within 10 years this will be common practice.

 

[Sideswiper]

I'm sorry, looking up "GE Brick" is giving me confusing results, do you have a link?

 

[DTR2011]

GE Brick

http://www.gedigitalenergy.com/multilin/catalog/hardfiber.htm

 

[marks1080]

The Brick, or devices like it, are the way things will soon be done imo. The first thing that jumps out at me is... how do you test the relay? We are used to opening current/potential circuits and injecting signals. That doesn't seem possible, or at least practicle with the brick.