POWER TRANSFORMER PROTECTIVE MAINTENANCE BASICS AND TUTORIALS

POWER TRANSFORMER PROTECTIVE MAINTENANCE BASIC INFORMATION
Protective Maintenance Of Power Transformers Tips and Tutorials


Protective Maintenance
This philosophy consists of performing preventive maintenance, predictive maintenance, and corrective maintenance. The preventive maintenance involves schedule maintenance and testing on a regular basis.

Predictive maintenance involves additional monitoring and testing, where as corrective maintenance involves repairing and restoring transformer integrity to its original condition when degraded conditions are discovered.

The objective of the protective maintenance of transformers is to control and prevent severe oil and winding (paper) insulation deterioration. Mineral oil and paper insulation of the winding are affected by moisture, oxygen, heat, and other catalytic agents such as copper, iron, electric stress, and so on.

The end result is that oxidation takes place in the oil which leads to sludging of the transformer. In sealed units ingress of moisture via atmosphere or seal leaks must be prevented.

Moisture will reduce the dielectric strength of both the oil and the winding insulation systems. In addition, excessive heating of the transformer will cause the paper (winding insulation) to decompose (accelerate aging) which in-turn produces moisture (i.e., break up of cellulose fi bres results in freeing hydrogen and oxygen atoms which combine to form H2O).

Increased moisture formed in the paper not only reduces the insulating strength of the paper but also, as temperature rises, the moisture will migrate from the paper insulation to the oil and decreasing its dielectric strength.


The first step is to build transformer designs to keep moisture and oxygen out of transformers. The next step is to operate transformers so that they are not operated beyond their temperature ratings and limits.

In addition to the above, the severity of deterioration should be controlled by monitoring and testing transformer insulation systems on periodic basis, and take corrective actions to restore transformer to its original condition.

This philosophy can be summarized by the following:

1. Control transformer heat
2. Inspect and maintain transformer auxiliary devices
3. Test and maintain transformer insulation systems
4. Maintain transformer bushing insulation
5. Maintain transformer protective coating