Insulation Resistance Test
The insulation resistance test is another important test in transformer testing that is used to determine the strength and quality of insulation used in the transformer. This test is also performed during manufacturing and commissioning of the transformer. However, it may be performed during maintenance of the transformer if required. The primary purpose of the insulation resistance test is measure the electrical resistance of the insulating material used between various conducting components of the transformer. This tests helps to evaluate that how much electrical stress the insulation can handle without breakdown.
Thus, the following are the primary objectives of the insulation resistance test of a transformer:
- To determine the weakness of the insulation that may cause faults in the transformer.
- To ensure electrical safety of the transformer, as a weak insulation between conducting components can cause an electric shock.
- To measure moisture content and degradation of the insulation.
Procedure of Insulation Resistance Test
We perform the insulation resistance test on an electrical transformer as per the following steps:
- Isolate the transformer from the power supply and properly de-energize it.
- Connect the measuring instrument to the transformer for measuring its insulation resistance.
- Take the following three readings:
- Measure the insulation resistance between the high voltage winding and transformer tank. During this measurement ground the low voltage winding.
- Measure the insulation resistance between the low voltage winding and the transformer take. During this measurement ground the high voltage winding.
- Measure the insulation resistance between the low voltage winding and the high voltage winding. During this measurement ground the transformer tank.
After measuring all these insulation resistance values, we have to compare them with the expected values. If the measured and desirable values are equal or nearly equal, it indicates that the insulation is in good condition, otherwise it need some corrective actions.
Hence, the insulation resistance test plays an important role to judge the quality, reliability, and safety of a transformer and it prevents any kind of unexpected failure of the transformer.
Transformer Testing
Transformer testing is a process of examining a transformer to determine its health i.e., whether it is working properly or not. On an electrical transformer, we can perform various types of tests to measure its performance and efficiency and to take corrective actions.
As we know, in electrical systems, an electrical transformer is one of the most important and commonly used electrical machines that perform voltage and current transformation. Thus, the primary function of an electrical transformer is to increase or decrease the value of voltage or current in an electrical or electronic circuit. To perform this voltage step-up or step-down operation, the transformer utilizes the phenomenon of electromagnetic induction.
To ensure the desirable and proper operation of a transformer, we perform a variety of tests on it such as winding resistance measurement, insulation resistance measurement, dielectric strength measurement, and more. The group of transformer tests is referred to by using an umbrella term, transformer testing. This article will explain the concept of transformer testing and different tests that are to be performed on a transformer daily, quarterly basis, and yearly basis. Let’s get started with the basic definition of transformer testing.
Table of Content
- Transformer Testing
- Types
- Type Test
- Routine Tests
- Special Tests
- Pre Commissioning Test
Transformer Testing