Applications of distance relays on distribution networks

[PeterS84]

Hi All,
I'm interested in hearing your opinions on using distance relays on distribution networks - how common is it, do you use it mostly as primary or backup, what are the expectations as far as the operating time is concerned (is ~30ms acceptable for Zone1), are you trying to use it on networks with a lot of distributed generation (with all the problems related to variable amount of DG that can be connected at one time)?

Thanks in advance,
Peter

 

[DTR2011]

I believe it really depends on how your netWork is configured. In th US, which has mostly radial systems, it is not often used, unless there is DG. In some European countries, @10kv, it is quite common,as there are networked systems at that level.

 

[dpc]

I've never seen a distance relay on a utility distribution feeder in my part of the world.



David Castor

http://www.cvoes.com

 

[DTR2011]

In the greater Chicago area, if you want to connect DG, you must have 21P protection (local utility interconnection policy). This is of course at a generator site. As far as feeder protection I have not seen it in the US. In areas of Germany and Austria and other places in that region, it is as popular as a 50/51 relay.

 

[PeterS84]

Is it then considered as anti-islanding protection?

 

[dpc]

smallgreek,

So the 21P has Zone 1 set to reach back to the utility substation?

 

[PHovnanian]

Its rare. Distance protection works best when the line impedance comprises a significant part of the total system impedance at the point of a fault. This is the case on (longer) transmission lines than (shorter) distribution lines where the substation and upstream source impedances are relatively greater.

The other issue to consider is: Why use it? Transmission systems are typically configured to loop through a series of intermediate substations, each with its own system of breakers. In this case, distance relaying provides a method of tripping the closest breaker to the fault.

The case of distribution with multiple sources (DG, for example) is one possible application, but I think directional power schemes seem to be more popular, at least for the small DG systems I'm familiar with.

 

[cranky108]

The only place we use a distance relay on distribution, is as a directional torque control for a loop.

 

[jghrist]

How would you coordinate distance protection with fused taps?

 

[cranky108]

We don't. The time over current relays do that. The distance relays are just for torque control.

 

[DTR2011]

Dpc-

It's been about 10 years since I have done commissioning work in that region. IIRC, it was a 2 zone step distance scheme, therefore I would guess it was ~80%/120%, or something in that neighborhood. The generation sites I was involved with were mostly landfill gas applications by some of the more well established players and some less in that market.

There were many heated discussions between the OEMs of packaged he sets and the local utility on relaying requirements.

 

[ScottyUK]

It's fairly common on the UK transmission and primary distribution networks, but our grid is very different to the US system, being a (relatively) tightly meshed system in a (relatively) small geograhical area. I'm no expert on distance protection, being from a generation background rather than T&D, although some of our relays use similar principles.


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If we learn from our mistakes I'm getting a great education!

 

[m3ntosan]

Depends what you understand by distribution system, if it’s 110 and 132 kV, then distance protection will be a main and a backup protection for OHL and cables in the UK and Eastern Europe, as far as I know. It's also used as a backup protection on transformers feeding in to distribution networks > 200 MVA , 400/110 kV and 220/110 kV in Eastern Europe, but not in the UK, and main protection on bus-couplers and bus-sections associated with autoclose schemes on 110 kV network.

May you grow up to be righteous, may you grow up to be true...

 

[PeterS84]

Thanks for all your replays.

@m3ntosan:
Yes, by distribution I mean networks up to 132kV. I'm surprised you mention cables as well - I was under impression that for cables it's mostly current diff.

 

[m3ntosan]

@PeterS84,

For 110 kV cables, in Eastern Europe you'll find old analogical distance protection RD110, from former Democratic Germany Republic, by EAW Berlin and differential protection, DZL from former Soviet Union, using pilot cable, these two as main protections and E/F or O/C as backup.

Also, you'll find important 110 kV s/s without BBP, using zone 1 extension or zone 2 override to protect the busbars from remote ends, with a fairly high level of generation embedded into 110 kV network. BFP with 500 ms setting at 110 kV in Eastern Europe, you won't find BFP in the UK at 132 kV level.



May you grow up to be righteous, may you grow up to be true...

 

[PeterS84]

By BFP do you mean Breaker Failure protection?

 

[slavag]

Hi.
110kV-132kV is not so distribution, its sub-transmission.
OK, its not so important.

BBP and BFP ( bus bur and breaker failure protection) are depend on the country code/standards or economical reason.

Actually, 21, Distance protection in radial O/H lines or cables with one source is not so used.

DZL is 87L, DZL is russian transcription of differntial line protection, based on the pilot wire or fiber optic connection between ends.
As usually, all depends