Power Factor Improvement

They need to be close to the load, so as to reduce the current in the feeder cable.

In case of a rural feeder having a diversfied load, scatered across the feeder of approximately 100 KM in length,it would be difficult to locate the load centre. Can we rationalize it by any mathematical formoula?

Network calculations are, by their very nature, iterative and exceptionaly tedious. It might be better to place the effort where results can be won early.

It is easiest to look at each individual load point and assess the economics of installing power factor correction [PFC] at that point. PFC can significantly reduce the current in branches of a feeder, thereby reducing hot-spots both in it and locations further upstream. It also reduces the risk of needing to replace sections of the feeder with larger-cross-section cables.

Locating capacitors on a distribution circuit is as much an art as a science. If your system design is similar to what I saw recently in Thailand, the feeder has a relatively small number of large (500KVA or greater) distribution transformers. I would install capacitors adjacent to the larger distribution units. In my US system, I can estimate the capacitor KVAR at about 25-30% of the transformer KVA, but your load characteristics may be different.

If you want to be more precise, you can do some short-term monitoring of the feeder. Install a meter on the line in several different places to record voltage, current and power factor for about a week. Use the data gathered to find the optimum capacitor placement in order to minimize the distance reactive power will flow.

Once the capacitors are installed, check the power factor on the feeder at the substation. Because the load profile isn't flat (the load varies with time of day), you can't get a constant unity at the feeder. Just find a good average where the feeder is sometimes lagging a bit, sometimes leading a bit, but stays centered around 1.0.

Normally the 11kv supply receivers install it on their 11kv bus.In your case it should be close to the point where u are steeping it downie near the transformer where it is converted to LT voltage could be 440,380 depending upon ur country's practice.