Generator-EGCP2-Lightining

Hello ramvinod

1. A problem of damaged control module in Cat Power Alternators was solved by us some 40 years ago.

We used smaller Cat diesel alternators at the Temporary Powerhouse of Manapouri Power Station, Southwest of South Island, New Zealand, during construction of the permanent powerhouse.

Control modules were some NZ$2,000 each at the time, and several could be needed each week.

Caterpillar were no help, they just sold us more control modules.

We sent damaged modules (electronic units sealed in epoxy resin) away to the then DSIR (Department of Scientific and Industrial Research), and had them Xrayed, photos taken, then the epoxy was dissolved.

There were some diodes which we replaced with diodes of a higher PIV, recast in epoxy, sent back to site, and we tried them.

No further problems occurred, either from lightning, or 11kV cable "Flit Plugs" explosions down the tunnels.

I do appreciate 40 years has elapsed, and your units will be updated versions.

But the problem may be of a similar nature - you would have to try and see.

We also used to place High Voltage arc gaps (arcing horns) to arrest most of the lightning which harmlessly discharged across the arc gap.

The ground side of the arcing horns went to extensive Earth Mats located all below the installation, and to some further 10 metres all around each substation/takeoff point/cable connection.

We also ran overhead/aerial earth wires above the 11kV lines as required, and bonded these to each earth mat wherever the HV supply went.

The location there was on alluvial gravels, and also hard rock.

To encourage the lightning surge out of the electrical system, we also used to place some 20 turns of heavy conductor in series with each phase of the 11kV system, to act as an air-cored inductor, which kept the high-frequency lightning pulses out of the alternator/transformer system at the supply end, also similar air-cored inductors at each take-off point before the 11kV went into a substation or cable.

2. The hunting is almost certainly related to lightning damage, as it seems to have started at the same time as (1) above.

There would appear to be some damage in the control system, related to that lightning damage.

Summary:

Lightning-prone areas do need special planning, to eliminate problems as you have experienced.

You may also need to install lightning conductors to high points, if possible.

Without seeing your local situation, I do not know whether the lightning damage is caused by direct strikes or induced surges.

That's presently the best remote analysis I can give you.

Advise with further details, if able:

Site Photos, Site layout, elevations of equipment and buildings, HV Distribution layout, Earth Mat details, Transformer details, Soil resistivity and other details would be useful.

Kind Regards....

I too feel that the problem is mainloy due to induced voltages in ur system during the lightning. This can happen because of the earthing anomaly wherein the ground potential rises during lightning strike. It is better that u inspect the earthing system, its resistance and i would advise you to ensure the cabletrenches running between the buildings are totally covered with metallic cover, preferably aluminium which has low magnetic permeability. The cables would then be in a metallic tube similar to afardays cage and externally induced voltages will not damage.

Hello,

Why do not use surge traps?

It fixs the voltage and interrupt in case of strikes or indesirable high voltages.

Regards,

Hi Ramvinod,

Regarding the lightning failures, I agree with all the above.

For your hunting problem which only may be coincidental, Contact Woodwards. We have always found them to be very helpful.

The hunting is may well be a mechanical issue. Check all the linkages in the injector pump / linear actuator chain are free and without too much free play.

I don't know this particular module but they normally have a stability control potentiometer. Has some one adjusted this wrongly? Look up the makers recommendations and readjust it.

Best of luck

Chas

contact Mr.K.P.Haran of CAT who is based in Caterpillar engines Plant at Hosour who is new product Introduction manager who is an expert on EGCP and CAT 3500 gensets his Mobile e-mail is haran_k_p@cat.com who would be of help to you.

crm