Protecting long distance transmission line through Pilot wire

[RAgrawal]

We are having about 5 KM long 132 kV, 4 nos Transmission lines protected with distance protection (PYTS relay, English Electric make).

I want to replace the distance protection with Pilot wire protection using HORM 4 relay (Areva make). For this 5 C, 1.1 kV grade 2.5 mm2, armoured pilot wire has been laid. I want to know following:

1. Is there any limitation interms of length of pilot wire?
2. What should be the voltage grade of pilot wire.
3. Any other problem, we can face, if we protect such a long length of line (5 KM) through pilot wire?

Fault level of 132 kV system is about 25 kA.

 

[ScottyUK]

One question would be why did you not opt for one of the fibre based differential relays such as Areva's LFCB? The distance problem with copper pilot based diff. schemes essentially goes away if fibre pilots are used.

Voltage rating would be to suit the maximum voltage likely to be encountered. Depending on whether this is a high impedance scheme, that could be quite high. It depends on the relay. I've tried to find a HORM 4 relay on Google, but it seems that it does not exist. Areva don't list it either. Can you provide either a URL to some data about it, or provide the correct type designation.

You are going about the design in a very strange manner: installing the cable first and then trying to find a relay which will work with it is unusual to say the least.


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[RAgrawal]

Fibre optic cable has not been used for some different reason. As far as laying cable first before selecting the relay, so let me clarify that control / pilot cable has been laid along with other cable and i have more or less decided to use HORM 4 relay as pilot wire relay. But some one has created a doubt in mind that due to long distance, this relay may mal operate. HORM 4 relay works on circulating current principle.

Regards,

 

[jghrist]

I think RAgrawal must mean MHOR04 not HORM 4. See

http://www.areva-td.com/static/html...typid=1079943327043&productline=1079943326752

I wouldn't think 5 km would present a problem, that isn't very long. The MHOR04 instruction manual should give guidance on pilot wire series resistance and shunt capacitance limitations.

The voltage grade of the pilot wire depends on the station GPR. Insulating transformers will be required and maybe neutralizing and/or drainage reactors.

See Chapter 5 of the GE Art and Science of Protective Relaying at

http://www.geindustrial.com/multilin/notes/artsci/art05.pdf

for a technical discussion of pilot wire relays and limitations.

Line differential relays with fiber optic cable would be much simpler. I'm working on a project now to replace pilot wire relays and copper pilot wires with line differential relays and fiber optic cable.

 

[skm]

jghrist : HORM 4 is the relay used for pilot wire protection and it mainly marketed in this part of world (India)by erstwhile Alstom-T&D.

As for its applicatiuon is concerend I remember using this relay for pilot wire protection application of 33kV overhead line + cable with a total route lenght of 20km about 10 years back. Will check and let you know anout its pilot wire cable specification. However as per the relay catalogue of HORM 4 and I quote:
"Any type of pilot having an insulation grade which can withstand 500V between cores may be used. The pilots should have a loop resistance excluding the relay of 1000 ohms. and a total intercore capacitance of less than 1.0 microfarad. The pilot circuit should be capable of tanding a pressure test of 5 KV rms between the two cores connected together and earth."

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