Two 150kVA, 3 phase-3 wire alternators are paraleeled manually through a synchroscope. The moment they are paraleled the pf of both generatos goes out in opposite directions. No.2 Generator isolates because of the reverse power relay operating.

Bosch type fuel pump units on both generators with motors that can be remotely operated throug the switch board controls are fitted.
Suggestive of cross-current compensation adjustment required.

Can somebody give me some guidelines/diagrams

 

Your reactive droop is not set on one or more of your regulators. You need to take one gen off line set your kw base plant load with pf of .9 lag. Put gen two on line take one off and set droop as per gen one. This should help, reactive droop, cross current compensation will need to make sure your in droop before moving forward. This can be set basler sr4a slide resistor, if memory serves me correct, lead to lag less droop, digital dvr2000e etc. laptop adjustable.

 

First of all a couple of questions:

1. Are the generators intended to operate in parallel, or were they originally designed for stand-alone units?

2. Do you know the droop characteristics of both speed control and voltage control of both generators?

3. Do the speed and voltage controllers of the two generators have the same setpoints, or are they set arbitrarily?

Generators that were originally designed for stand-alone operation do not normally have cross current compensation systems, unless they are equipped with the more sophisticated control systems, which in the size of your generator may not be the case.

Having said that, you can get to operate your generators in parallel if you have access to the droop and reference setpoints of both speed and voltage of both generators. Basic procedure is this:

1. Run each generator at no load condition (i.e. with circuit breaker open) and measure the speed (frequency) and voltage. This gives you the reference setpoints of each generator. If adjustments to such are possible, set the two generators such that both have the same no load speed and same no load voltage.

2. Apply the same load to each generator seperately, and measure both the speed drop and the voltage drop of each generator. This will give you the speed droop and the voltage droop characteristics. Again if you have adjustments set the two generators to produce the same droop for both voltage and speed. Aim towards a droop of about 3 to 4% for each parameter, to ensure stability.

3. Repeat 1 above to ensure that the reference setpoints have not shifted, or else repeat 1 and 2 above to get the characteristics of the two generators as close as possible.

With this approach you should get your generators to run in parallel without the need of cross-current compensation. They will not share exactly 100%, but at least they will run in parallel without either of them overshooting to one extreme and tripping out.