Blinking Incandescent Bulb

I presume all load including the Bulbs are on 3x1 Mw gensets.The generators must be running in parallel to supply 2.4MW.The load is varying ie a sudden demand and then ease off like in a press or Furnace.The generators are not able to support the sudden demand for power and hence there is a voltage and frequency drop which is seen clearly in the Incandescent lamps.Check the voltage and frequency when the lights are dimming and again when brightening.Try running 4x1 Mw .U may not have this problem.Another problem could be a low PF which makes the generators underrated.So in all probability running 4 in parallel may solve this problem.

Since we start the plant the load has not increase or no additional load has hook-up. This problem has just happen recently, after the do 15,000 hours service on the cummins engine.

1. Has the blinking always occurred in this configuration, or is this a new problem?

2. Are the lighting circuits connected at generator voltage, or is there a transformer involved?

3. Are the lighting circuits connected line to line, or line to neutral? (If line to neutral, I suspect the lighting panel may have a damaged or loose neutral connection.)

Blinking could be attributed due to following :

1]Loose connection including neutrol.

2]Suddon demand in load drops the frequency.Dimming will also be noticed during this period. Please observe & record the dip in voltage and frequency.

3]Genset governer could be sluggish.Please chech the governer performance and the droop.

4]Check the fuel quality , fuel filter cleanliness and air filter condition.

How fast does the blinking of lamp occurs?

Most probably frequency of voltage generated (50Hz) from one or more alternator is not matching.

Have you checked the frequency of each alternator output before synchronising to bus bar?

the generators are shifting out of phase = shorting and then coming back in a cyclic manner.

This can harm the gen sets .

Since this is a new problem, something must have failed/changed in the control circuitry that is supposed to keep all three online and in phase.

Read the manuals.

Check the output voltage of the AVR for proper stability setting (gain).

Does this happen evry second or so or randomly? If random, load response to AVR output needs to be investigated.

It happen every half second contineously, especially when the load or our 1.5MW sag mill motor is running.

Check the DC output from the AVR to the generator(exciter) for fluctuation and REDUCE the gain setting slichtly to stop the ossilation.

All plant lighting are blinking continoiusly in every half second. I checked the frequency is fluctuating between 50.05Hz to 49.92Hz.

This could indicate a serious problem in the phasing of generators. Try supplying the lighting from a single source (generator) and see if the problem is fixed....

I test all genset by loading the plant lighting circuit only and it doe's not blinking it's okay.

could you please check UK regulation P28 in this regard, it will give you some fare amount of idea.

thanks

Do you any large capacity Thyristor controller to control some heavy load like heaters? If yes fine tune your PID. I have faced similar problem few years back; could rectify by fine tuning.good luck.

Is the Sync; Voltage comparing; Power-Sharing; Transfer of load are Automatic or Manual?

Before Shifting of Load:
Normally all the Power-Sources are connected to Out-Put Assembly one by one & put on load.

Lighting load is also pure-resistive.
Any Inductive Load? Specially Varying-Speed [even due to varying or Withing On-Off type.

Seems to be problem in "Synchronising" of generators or mis-matching voltage.
But in Automatic Systems problem-creator is Isolated after some time.

Low-Power-factor seems to be not there due to Incandescent-Bulb load.

Control Gear [Control Assembly may be problem.
Try putting a part of lighting load on a single generator, one by one.
If no problem it is Sync problem. Look in the relevant control.

Unless you are on-site only probabilities can be listed.

As I have mentioned before, make sure that they are all supplied from ONE generator for a time as what I think is happening is that the line is from one generator and due to inaccurate wiring, the neutral is from another. The two Gennies are running, BUT NOT PARALLELED to each other!! You might be seeing the difference in frequency....