Installing Capacitor Banks in LT Diesel Generator Circuit

No.

If you have automatic voltage regulation on the gen set any attempt at pf correction will upset working of voltage regulator.

The DG set is operating at 0.8 power factor lag.The Capacitor is required for Voltge improvement for the line losses.The capacitor addition will derate the capacity of DG Set.So you should not connect the DG Set with capacitor bank.More over sine wave of genaration will be distorted which results equipments get damaged.

Hello,

At first i suggest u dont use capacitor for D.G. Alternator of Diesel Generators systems are rated for 0.8pf Lag. We can not add uncontrolled reactive ( Capacitive ) compensation for DG. If in case of power factor of system goes to leading, then there is every chance failure of windings

You can purchase power factor controllers commercially (reactors). We use them all the time on drilling rigs which run at 0.2 PF. 7-8 MW at 0.2 PF is a ton of amps and heat. We have swings from 0.2 to 0.95 with the average at 0.6. Low power factor numbers like 0.2 heat up the rotor more than the stater. At 0.8 PF the generator people wind and cool the stater and rotor to be at the same temperature rise. Anything off of the 0.8 standard rating will heat the rotor as the regulator field forces the poor girl to keep voltage dip in control due to recirculating magnetism throwing some harmonics on the sensing lines. You can even buy reactive load banks to match your resistive load banks when you test generator sets. The engine only sees watts, so controlling power factor will not save you any fuel. It will keep the generator cooler. 1000 kW at 0.9 PF will burn as much fuel as 1000 kW at 0.2, but, the amps will toast your alternator at 0.2 if it is not rated for it. For low power factors I specify a 20% sub-transient reactance generator (high impedance windings) to limit current draw at these excursions. You can also look into a permanent magnet generator on the back of your rotating rectifier (your alternator may be designed to add this) and this roatating magnetic field produces AC voltage to power your regulator so the regulator line power voltage is free from harmonics and will not shut off the regulator during a short circuit.

I hope this helps.

Hi Petropower,

Recently, a 500 kW - 480 V 3 ph new DG plant, shut-off 3 minuts after start by inverse power when start a 180 HP ESP. The HV side of SUT has one capacitor Y bank 5 kV - 3x2x5 microfarads.

Can we discuss this question please?

Please answer to Serca_2@hotmail.com

Thanks.

All the Alternators are rated for .8pf. The true power limit is KVAX.8. In order to limit the reactive power,We may have to adopt real time compensation rather than fixed compensation. As you increase the power factor the de-ration of DG starts to increase.

Hence we may have to check & balance KVA gained and de-ration.

I have seen some real time dynamic reactive compensator, which will provide reactive compensation for both lag and lead depending on the input signal it gets from output. It is PWM IGBT based compensator with capacitors.

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Instal AUTO POWER FACTOR CONTROLLER, with a set point as 0.92 Lag

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