35kV Line Reactors

[lyla1711]

We're working on a 35kV ring bus constructed out of GIS (four buses) and underground conductors. So it will be M-T-M-T-M-T-M-T (back to the first M), with each bus served by a substation transformer running the Delta Var 2 paralleling scheme. The loading on each bus is nearly identical. Typically the ties run open. During transformer maintenance, ties run closed.

Due to the physical layout of the site, we can't make all the tie conductors equal length (Bus 1 to Bus 2 tie is 90 ft and Bus 4 back to Bus 1 is 270 ft). I've been trying to match impedance by using different sizes/sets, but I'm finding that it's not practical. Are line reactors ever used at 35kV to match conductor impedance? I've never used them on the MV side before.

 

[RRaghunath]

I don't think there is any need to equalise the tie feeder impedances. I have seen ring main networks like this before.

 

[Jpascp]

We're working on a 35kV ring bus constructed out of GIS (four buses) and underground conductors. So it will be M-T-M-T-M-T-M-T (back to the first M), with each bus served by a substation transformer running the Delta Var 2 paralleling scheme. The loading on each bus is nearly identical. Typically the ties run open. During transformer maintenance, ties run closed.

Due to the physical layout of the site, we can't make all the tie conductors equal length (Bus 1 to Bus 2 tie is 90 ft and Bus 4 back to Bus 1 is 270 ft). I've been trying to match impedance by using different sizes/sets, but I'm finding that it's not practical. Are line reactors ever used at 35kV to match conductor impedance? I've never used them on the MV side before.

I have never seen any application for your purpose. Only for the following applications:

 

[bacon4life]

The impedance of 270 ft of bus may be negligible compared to the transformer impedance.

 

[waross]

One solution may be to run both bus to a common equi-distant location and from there together back to the transformer.

I've never used them on the MV side before.

Old text books, 80 to 100 or more, described a wireless reactor used for transformer impedance matching and load sharing on 110/220 Volt secondaries.
Transformer life was 20 years or less.
Failures were common.
If a larger transformer failed it may be replaced by two, smaller, unmatched transformers.
Hence the need to match impedance for load sharing.
The wireless reactor was a window core similar to a window CT core.
the wireless reactor would be mounted on a cross arm and one 120 Volt secondary line run through the core.

You may consider intentional magnetic encirclement on the shorter bus.
Run the numbers and see if it is feasible.