Optical CTs & VTs for 132kV outdoor switchyards 6

[RRaghunath]

I have searched the forum and found some posts on the optical instrument transformers.
These seem to be preferred choice when it comes to measuring high order harmonics as well as high precision revenue metering over a wide load range.
But as a technology, these are still not very proven when compared to conventional CTs & CCVTs and are still much, much expensive.
Appreciate any feedback.
Thanks in anticipation.

 

[dpc]

I know ABB has been pushing this technology for several years and also predicting the end of conventional PTs and CTs.

But I've never seen any units actually installed and operating for either metering or relaying, at least in this part of the world. It probably can make economic sense at EHV substations, but at 132 kv, I'm not so sure.

David Castor

http://www.cvoes.com

 

[rcw retired EE]

I put some in for metering at 230 kV on a generating plant two years ago. The supplier is now out of business. They sold the CT technology to someone but no one picked up their VT technology.

It's not cost effective at 132 kV. Yo can get high accuracy without going optical.

There are some instrument trasnformer experts on the forum that coudl give you better ideas.

 

[scottf]

Optical units are good at measuring high order harmonics...but a conventional CT will do pretty well up to approx. the 32nd harmonic. Do you need information on higher harmonics?

As for revenue meter, there are conventional CT options that actually have a wider and more accurate range than optical CTs. Check out AREVA's extended-range CTs (ERCTs), which was a Ritz product until AREVA bought the HV part of Ritz in 2006.

(disclaimer, I was with Ritz and was involved in the ERCT development and promotion...still with Ritz, but we have nothing to do with the AREVA HV products any longer)

Your comments on the optical technology not being proven is correct. One of the reasons the technology hasn't taken off is all of the optical offering have had MAJOR field problems. Aren't many customers willing to pay a high premium for optical units with a high risk for problems and, in the end, don't offer many, if any, performance options over modern conventional ITs.



Your

 

[RRaghunath]

All valuable comments. Thanks dpc, rcwilson and scottf.

US is generally in the forefront when it comes to embracing new technology (at least that is my impression).
But, it seems even in US, the optical instrument transformers are yet to gain a foothold.

 

[Paszt]

"US is generally in the forefront when it comes to embracing new technology"
You made me spit my drink out from laughing. The US is lagging most of the rest of the industrialized world as far as Power Transmission & Distribution technology. I attribute this to our very large infrastructure (making upgrading slower) and also our more mature work force. I take no stance on whether this is a good or bad thing.

Case in point is the IEC-61850 standard which most of Europe and the Middle East are implementing in the majority of new installations. The US is still in large part in the testing phases.

If you're not familiar with IEC-61850, it's implementation will replace the traditional copper wires with communications cables.

Which brings me back to your Optical CTs & VTs question. Once the process bus part of the IEC-61850 standard is finalized, optical CTs & VTs will be used to enable digital communications between the instrument transformers and the metering and protection devices.

 

[RRaghunath]

Thanks, Paszt.
I too think the optical CT/VT future is linked to IEC61850 (and so called digital substations).

 

[Skogsgurra]

I was working with HVDC guys in Ludvika 10 - 15 years ago. Some of them were working on optical current transducers and were very enthusiastic. I think that these CTs were used later in quite a few HVDC projects. But never seen them in ordinary 50 and 60 Hz applications.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[slavag]

Hi.
From my point of view we have here mix of things.
IEC61850 with optical CT/VT and process bus is somthing one.
BTW, isnt exactly too, see GE solution with standard CT/VT and Brick.

Optical CT its somthing other
For example see attached:

http://www.nxtphase.com/sub-products.htm

Om this moment conventional CT/VTs are preffered, IMXO.

Best Regards.
Slava

 

[86ed]

I agree with Paszt. The U.S. is definitely lagging in power Generation/ Transmission/ Distribution technology. There are a lot of old school guys out there that still aren’t ready to give way to some of the new technologies coming out. Also, utilities would need to reassess the maintenance workforce needed for these new technologies. It would require hybrid specialists that can work on older protection schemes that also have the ability to work with the new stuff.

In the past I worked with a major U.S. utility and now I work for one of the big bad European engineering conglomerates. I’m getting the opportunity to work on technologies (i.e. IEC61850) that I wouldn’t have seen at the utility for years.

 

[RRaghunath]

Paszt & 86ed,
UEC which is the basis for IEC61850 originated in US, is n't it! If this is true, it is suprising US is not leading when it comes to adopting digital substation concept! May be it all boils down to economics!

 

[scottf]

Regarding adoption of new technology, I would use optical instrument transformers as a good example of newer not always being better.

US utilities were rightly very cautious to adapt optical IT's and that decision was proven correct on many fronts.

Still today, optical IT's aren't anywhere close to being reliable enough for use in protection or revenue metering applications. I honestly don't know of one single installation of optical IT's that haven't had some kind of problem, ranging from repeated failures of electronic components to inherent design issues with accuracy drift and error.

 

[marks1080]

The utility I work for doesn't use a single optical IT. We are one of the larger utilities in N.A.

In regards to new technologies we do use them. But we test them rigorously before making them standard. Some of the senior P&C engineers with my utility have worked directly on developing the IEEE 61850 standard. Both the U.S. and Canada have done a lot of work creating the 61850 standard. N.A. is leading the way on that, and other technologies. We have implemented it at one of our stations along with the GE Brick as a 'C' scheme.

I work on a nuclear site and we are contracted to do their P&C work. All relays on the nuclear site are electro-mechanical, with the exception of an old microprocessor based relay that the utility developed itself in the early 80's. My impression of the nuclear world (at least the site I work on) is that change is very slow. As long as the process works, people are very hesitant to change equipment, for good reason.

 

[Paszt]

Realize that I never said that the US was not inventing the new technologies, just that we are slower to adapt. I also stated that I take no stance on whether this is a good or bad thing. New technology is good, but not if it fails regularly. I am however against the use of electro-mechanical relays in new projects. The microprocessor based relays have been proven to be reliable.