How To Assess The Condition Of A Power Transformer

Power transformer is an important link between domestic users and local substation for power supply.

It is mandatory to have a power transformer in viable condition. If the power transformer is not checked regularly then there can a fault in a transmission. It can result power supply outages over a large area.

In this article we would discuss several factors that determine the condition of a power transformer. Regular or periodic check up can help extending the life of a transformer.

Factors determining the health of power transformer

1. Winding: It is one of the most important parts of the Chint power transformer. The number of windings decides the ratio of the power transformer. It is vital to keep measuring the windings resistance from time to time. The transformer may have some loose contacts, that needs to assess and corrected. Electrical insulation of the windings as well as performing ratio test to be checked. It helps in reducing dielectric stresses, mechanical stresses and thermal stresses that can arise due to different issues on transformer windings.
2. Tap Changer or On-Load Tap-Changer: It is only mobile part on power transformer. It requires regular maintenance and checking. The mechanical defects in circuit and flaws in insulation system leads to improper functioning of tap changer. The mechanical defects deal with the incompetence of the changer to change the taps. This fault can be in the any component of transformer in the transmission system. Current circuit faults happen due to damage to the contacts. This ultimately leads to change in the resistance of the path of current. Tap changers are frequently damaged due to arcing also. Sometimes insulation system too fails. So, tap changers need to check thoroughly.
3. Bushing factors: It is an insulator in the transformers which permits an electrical conductor to go securely without any electrical contact with the transformer. It gives way to the current through the tank wall. The main cause for the inefficiency of bushing is overheating caused due to transformer vibrations. Other factors also include are bushing seal failure due to dielectric losses and partial discharge.
4. Cooling system: This system helps in minimizing the heat produced in transformer. The heat is produced due to copper and iron losses. The heat once developed in the transformer causes malfunctioning of transformer in many ways. The gases formed created more pressure which may result in bursting of transformer. It can also spoil the insulating materials present in the transformer.
5. Core Functions: The main role of the core in the transformer is to conduct and strengthen the magnetic flux created in it. A small defect in the core directly decreases the efficient working of the transformer. Due to eddy currents, there is breakdown in smallest part of lamination which leads to increase of heat. This would cause all kind of defects on the transformer.
6. Functioning of Tank: The main objective of tank is to contain oil which can be used for insulation and cooling purposes. The defect in the tank can occur due to various reasons. The factors which accelerate the process of degradation of tank are environmental, corrosion, humidity levels and radiation of sun. These factors can create cracks in the tank walls leading to leakage.

Types of Tests

There are several tests to check the proper functioning of transformer. Broadly two types of tests are conducted widely are routine tests and type tests.

• Routine tests are made to check the operational functioning of the individual unit
• Type tests comply with customised requirements like temperature rise test and dielectric type test

Along with these tests additional tests are also conducted by the customers at site before commissioning the power transformer.

These tests are conducted on regular basis as well as on emergency basis. These periodic test helps in assessing the condition of the transformer exactly and specifically.

The corrective methods and precautionary measures can be taken to ensure the proper functioning of the power transformer. This helps in extending the life expectancy and shelf life of power transformer.

Power transformers are critical and key systems among electrical assets both in primary substations and in industry.

When they breakdown, they cause financial as well as other losses. So, it is advisable to assess the working or functioning of transformer extensively on a regular basis. It would help in identifying various risk factors which can be rectified quickly.

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