Distributed Generation 3

[dwlawrence]

I am assessing the impact of a 1600 kW synchronous generator located approximately 15 kM out from a 13.8 kV substation. There is no regulation on the feeder and the utility maintains a fixed tap that maxes the voltage at the sub out at about 106% which results in 101% at feeder end at peak load. At minimum load, feeder end is around 104%. When the generation is added the voltage at the generator is around 108% at peak load and 110% at minimum load. I can get it down by absorbing more VArs (don't get me going on vars and Vars and VArs)at the generator but that seems crude.

The feeder conductor is a mix of 1/0 ACSR and 3/0 ACSR and there is one section that's #2 ACSR which of course is the root of the problem but reconductoring is not a preferred option.

Does anyone have any ideas for mitigation? I was thinking about a feeder regulator at the substation but I've seen voltage profiles for regulators that are all over the place with high voltage at low loads and not a lot of apparent intelligence. Are they any smarter now? If I could set it to sense if the generation was on or off and boost or buck accordingly this might work.

Comments?

 

[ccjersey]

How well would an induction generator fit into that location?

Any reason for that generator to ever be islanded or will it only operate in parallel with the substation feed.

 

[dwlawrence]

Not bad actually. It would still need the mid feeder regulator but the intrinsic VAr consumption seems to settle the voltage down quite well.

Bit of a starting problem though. Would need some TLC to get it going without dragging the feeder voltage down.

But there must be a catch. What is it?

No it will never island.

 

[Rodmcm]

I have engineered both synchronous ( no governor) and asynchronous on similar systems and have found that the induction units usually require a lower sending end voltage than the synchronous, They are also simpler, however, someone, somewhere has to make up the VARs.

In a recent project, with 2 x 1000kW synchronous units the only way we could keep the sending end voltage in reasonable limits was to install a pole mounted buck and boost unit. This was a cheap and good solution allowing us to export VArs, and never import them.

 

[dwlawrence]

Rodmcm

A "pole mounted buck and bosst unit"? Aka a regulator? So located right at the generation site, bi-directional, and what typical settings?

 

[dpc]

If you have other customers on this feeder, putting a regulator at the plant is probably not going to work. You can only raise the voltage so high at the sending end if you have customers electrically close to the regulator.

If this is an express feeder, you can get away with this.