Capacitive Power Factor

Maybe this.

"The generator set AVR monitors generator output voltage and controls alternator field strength to maintain constant output voltage. Relatively low AVR output is required to maintain generator voltage at no load. In the figure shown, the no load exciter field current required is less than half the full load level.

Filter equipment is often sized for operation at the expected maximum load on the UPS or motor load. At light loads there may be excess filter capacitance, causing a leading power factor. Since rectifiers are commonly designed to ramp on from zero load to minimize load transients, leading power factor loads may be imposed on the system until inductive loads are added to the system or the load factor of the nonlinear load increases.

A utility supply simply absorbs the reactive power output because it is extremely large relative to the filter system and it has many loads that can consume this energy. With a generator set, however, the rising voltage from the leading power factor causes the voltage regulator to turn down and reduce alternator field strength. If the AVR turns all the way off it looses control of system voltage, which can result in sudden large increases in system voltage. The increase in voltage can result in damage to loads, or can cause the loads to fail to operate on the generator set."

My question is simple is that if we maintain leading power factor at LT room. Is there a chance that can harm the electronic circuit installed on machines

No, there isn't.

As long as your voltage stays within the equipment rating, it should be OK. Usually voltage rises with excess reactive power contribution to the circuit.

What is LT Room? How do you measure power factor? It would be an unusual instrument, generally.

Maybe your paper had to do with power system resonance, which could be a concern depending on what you really have in your LT Room...

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/ia02607001e.pdf

<...This is very harmful for electronic circuit...>

Nonsense.

A normal HV to 400/230V transformer will have about 4% impedance. At rated power/current transfo typical regulation with load power factor is...

Power factor, Regulation

Unity, +1% - you get 99% nominal volts

0.8 lag, +3%

< 0.5 lag, + 4 to 4.2 %

0.75 lead, - 2 %

0 lead, -4% - you get 104% volts.

So, if transfo ratio is chosen to give 230V +4% no-load, which is common, you could get 108% volts with leading load, plus however much the HV may go high, maybe 110% total. Compare 104% less 1 to 3% = 101 to 103% with 0.8 lag to unity.

Of course, it is unusual that capacitive load is near 100% of transfo rating, but it is clear why leading loads are deplored by power suppliers.

Another basic factor is that capacitive loads switched-in at peak voltage will instantly draw a very high peak current. Resistance in a capacitor is less than 1% of its 50 Hz reactance. Compare the slowed current rise with inductive load.

Due to high peak current, contactors/switches have a much reduced rating for capacitive load for e.g. fluorescent lamps with electronic ballast or choke with power factor correction.

Semiconductors are even more stressed by the high peak currents of capacitive loads so inverters feeding capacitive loads is usually a "no-no".

The sudden high current and voltage dip when switching on a capacitive load can upset electronic equipment e.g. switching on compact fluorescent table lamp can cause modern TV (typically with remote control and without mechanical on/off switch) on same outlet to turn on without user action.

If you have a capacitive source reactance, this is likely due to capacitors connected inside the installation and these capacitors could instantly provide high current if you connect a load (even if they compensate parallel inductive loads steady-state).

However, since many installations have significant P.F. corrected lighting loads without trouble, I would look at the voltage at "problem" loads before blaming the supply source.