Partial Discharge Test
In transformer testing, the partial discharge test is a type of test that is used to determine the major defects in the insulation material used between different conductive components of the transformer. Partial discharge is nothing but a local electrical discharge that occurs within the insulating material used in the transformer and it provides information about the quality of the insulating material. The partial discharge is considered an early indicator of degradation of the insulation material.
This test becomes more important in the case of high voltage transformers. It is performed during manufacturing, commissioning, and maintenance periods.
The main purposes of the partial discharge test are the following:
- To detect any kind of defects in the insulation material used in the transformer.
- To determine the overall condition of the insulation material used.
Procedure of Partial Discharge Test
The following steps are followed to perform the partial discharge test on a transformer:
- Properly isolate the transformer from the power supply and bring it in the stable condition.
- Apply a high voltage across the transformer insulation. This applied voltage is greater than the normal operating voltage of the given transformer.
- Increase the applied voltage gradually to produce a partial discharge.
- Detect the partial discharge occuring in the insulating material during the test. For this, use the specialized sensors.
- Record the readings of the testing instruments and perform data analysis to obtain the test results.
It is always important to note that the partial discharge test is performed on a voltage higher than the normal voltage but lower than the breakdown voltage of the insulating material used in the transformer. Also, this test is performed at different voltages to determine the quality of insulating material used in the transformer under different electrical stresses. The results of this test provides complete information about the health of the insulating material used in the transformer.
During the partial discharge test, if low or no partial discharge occurs, then it shows that the insulation is in healthy condition. On the other hand, if a high or abnormal partial discharge occurs, then it shows that the insulation has become weak and may cause transformer failure. Hence, the partial discharge test helps us to make decisions about maintenance and repair of the transformer insulation.
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