Winding Resistance Test
In transformer testing, the winding test is an electrical test that performed on a transformer to measure the resistance of its primary and secondary windings. This test provides the information about the DC resistance of the transformer’s primary and secondary windings. This test helps to examine the following issues in transformer windings:
- Loose connections between conductors
- Damaged conductors in the windings
- Transformer windings have specified electrical parameters to meet the industry standard
The winding resistance test of a transformer is basically a routine test which is performed during manufacturing and commissioning of the transformer. But it can also be performed during maintenance period to identify any abnormality.
Thus, the following are the two main purposes of the resistance winding test of transformer:
- To identify or predict any kind of fault due to winding resistance
- To calculate the temperature rise of the transformer windings, as the winding resistance is one of the key factor that influence their temperature.
Procedure of Winding Resistance Test
The step-by-step explanation to perform the winding resistance test on a transformer is explained below:
- Isolate the transformer from the system and de-energize it.
- Connect the required instrument to the transformer windings to measure their electrical resistances. It is important to note that the resistance testing is performed separately for primary and secondary winding.
- The test equipment gives the voltage and current values for the winding. Then, we use the formula (R = V/I) to calculate the resistance of the winding.
- These values are then compared with the standard values of the winding resistances mentioned in the design sheet of the transformer. If there is any significant difference between the measured values and specified values. Then, we take corrective actions.
While performing the winding resistance test, we take care of the following to ensure the accuracy in the test:
- Winding resistance test should be performed on ambient temperature. However, it should also be performed at some different temperature values that occur during normal operation of the transformer.
- Make proper connections between transformer windings and measuring instrument probes for accurate results.
- Follow proper safety guidelines to avoid any electric shock or accident. It becomes more important when dealing with high-voltage transformers.
After performing the winding resistance test, if there is significant difference between the measured value and the expected value of the winding resistance. This indicates that there is some issues in the transformer winding such as loose connection, short-circuit between turns, or any other fault.
Therefore, the winding resistance test is one of the most important diagnostic tool to evaluate the performance, efficiency, and safety of a 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