Cleaning of a Heavily Contaminated MV Alternator in Nigeria

Our alternator specialists have just completed the in-situ cleaning of a severely contaminated medium-voltage alternator in a power plant in Nigeria, Africa.

The alternator has been in operation for around 32,000 hours in a very dusty environment without ever having been cleaned. Eventually, the winding temperatures reached unacceptable levels so that the unit’s load had to be reduced. A visual inspection by the plant’s operator and insulation testing by a specialized company revealed that the windings were very dirty and that the insulation values were too low. The Polarization Index (PI), which was calculated to be 1.4, was unacceptably low. The manufacturer of the alternator, Leroy Somer, specifies the PI to be at least 2.0 while we recommend not less than 3.0.

The specification of the alternator is as follows:

Manufacturer:	Leroy Somer	Type:	AC Alternator
Nominal Power:	7600 kVA	Nominal Voltage:	11000 V
Nominal Speed:	750 rpm	Frequency:	50 Hz

Condition of the alternator before cleaning:

Condition of the alternator after cleaning:

5000 Volt Megger readings before and after cleaning:

QuantiServ’s technicians achieved a superb result without using any harmful chemicals or CO₂ at all. Only water and a special formula of water-soluble, non-toxic detergent was used.

The power plant operator was highly pleased with the result of our cleaning work. He was told by more than one party that the rotor had to be withdrawn from the stator for cleaning. That we did it in-situ saved him a lot of time and money.

This case shows well the outstanding effectiveness of QuantiServ’s alternator cleaning method. So far we have not yet come across an alternator that we could not clean in-situ and where dismantling was required!

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