CAT 5 cable

[144x]

Hi,
I need to know if there is any standard for usage of CAT 5 cable for transmission of data in the switchyard of the high voltage substations .let's say is it ok to use these kind of media instead of fiber optic cable in the HV and EHV environment for substation automation projects?
thanx a lot.

 

[davidbeach]

Why on earth would you even consider copper where fiber could work? The major benefit of fiber in these applications is its immunity to Ground Potential Rise.

 

[dpc]

Most CAT 5 cable isn't rated for outdoor, wet or below ground use.

You'll need to get an equivalent with proper use rating.

Fiber would be better.

 

[144x]

actually I don't want to use it.my contractor wants to use it.I want to prevent it .but I need proof.

 

[dpc]

Well, he'll need to come up with something that is rated for outdoor use and wet locations. It won't be from Staples or Office Depot.

Will it be in its own conduit?

 

[davidbeach]

What is he proposing as spark-gaps or other surge arrestor capable of blocking a few thousand volts of GPR?

 

[scottf]

I can't imagine why one would propose cat5 cabling in a substation.

There is no significant cost advantage. Fiber media converters (if they don't want to use a switch with fiber inputs) are very cheap and easy to use.

Seems to me, your contractor should be the one providing proof/justification!!

 

[itsmoked]

Or even wireless if the distances are short enough.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[144x]

I thought may be there is a quote in IEEE or some other standard addressing this issue.

 

[dpc]

Probably nothing in IEEE standards or NESC to prohibit it. In olden times there was no fiber, so communications was done by hard-wired signal, RS-485, or something similar, so it's not like it has never been done.

I think we're just saying that fiber eliminates a lot of safety and EMI concerns that you would have with wired Ethernet.

 

[davidbeach]

Keith, I wouldn't even accept wireless in a substation environment, at least not for anything related to protection. The substation can be an extremely hostile E-M environment during fault conditions.

Fiber is a wondrous solution to many problems and whoever is first able to make a usable fiber connection between instrument transformers and relays will probably make a killing. We can avoid copper for digital data, but so far the analog data from the instrument transformers still comes in on copper.

 

[itsmoked]

Good point!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[DonPhillips]

If you have a decent contract, you can ask the contractor to prepare a proposed deduct change order so you can see how much money he is willing to give back. This makes some of these substitutions go away.

Don Phillips

http://worthingtonengineering.com

 

[scottf]

Plenty of folks (my company included) make instrument transformers with digital output. Just not much interest in it.

We make a unit that uses conventional transformation and then convert it to digital with a fiber output. Not too many people are interested in it.

In reality, there's no real need to justify going away from how IT's are connected now.

 

[davidbeach]

OK, a complete system - Instrument transformer -> Standard Digital protocol over fiber -> Relay with input for said protocol. All of the above per C37.90. I'm not aware of a standard protocol or relays capable of accepting such an input, but I'd be glad to learn.

 

[lz5pl]

In my view problem with optical instrument transformers is that not only relay protections but also other loads must be connected. I don't know for example about existing of any energy meters for commercial metering suitable for connection to such CT's and VT's.
Anyway I expect in few years this will change also.

 

[144x]

anyway,after many hours of searching I finally got what I needed.

"IEEE P1615™/D4
Draft Recommended Practice for Network
Communication in Electric Power Substations"

link for download
"

http://grouper.ieee.org/groups/sub/wgc3/C3TF1 Documents/drafts/P1615_draft1.0.pdf"

has some figure which shows what kind of media should be used inside control room and what in the switchyard.

 

[ScottyUK]

Page 49 for those who are interested.


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