Transformer testing instruments can be classified in multiple dimensions based on the test object and purpose. Among them, classification by test items is the most commonly used method. The specific categories and corresponding instrument functions are as follows:
1. Insulation characteristic testing instruments
These instruments are mainly used to evaluate the operating conditions of the main insulation and longitudinal insulation of transformers. The core instruments and their functions include:
Insulation resistance tester: Measures the insulation resistance between windings and between windings and ground of the transformer to determine if the insulation is damp or has through defects.
Dielectric loss factor tester: Measures the dielectric loss factor and capacitance of the transformer bushings and windings. This indicator is a sensitive basis for judging the aging and dampness of insulation materials.
DC resistance tester: Measures the DC resistance of the transformer windings to check the welding quality of the winding conductors, the contact condition of the tap changer, whether there is a short circuit between winding turns, and whether the lead connections are good.
Absorption ratio / polarization index tester: Often serves as an advanced function module of the insulation resistance tester. By calculating the ratio of insulation resistance at different time points, it can more accurately determine the dampness of the insulation.
2. Ratio and voltage vector testing instruments
These instruments are used to verify the core functions of voltage transformation and phase adjustment of transformers. The core instruments and their functions include:
Ratio tester: Accurately measures the voltage ratio of the transformer, checks the accuracy of the tap changer adjustment at each position, and determines whether there is a short circuit between winding turns.
Connection group tester: Verifies whether the actual connection group of the transformer is consistent with the requirements marked on the nameplate.
3. No-load and load characteristic testing instruments
These instruments are used to measure the basic performance parameters and operating losses of transformers. The core instruments and their functions include:
No-load loss test system: Measures the no-load current and no-load loss (iron loss) of the transformer under the condition that one side of the winding is open and the other side is applied with the rated voltage.
Load loss test system: Measures the load loss (copper loss) and impedance voltage of the transformer under the condition that one side of the winding is short-circuited and the other side is passed with the rated current.
Power quality analyzer / power analyzer: Often serves as the core measurement unit of the no-load and load loss test systems, used to accurately measure key electrical parameters such as voltage, current, power, and power factor.
4. Winding deformation testing instruments
These instruments are specifically used to diagnose whether the internal windings of the transformer have mechanical displacement, distortion, or deformation after being impacted by short-circuit current or transported with vibration. The mainstream instrument is the frequency response analysis method winding deformation tester, which determines whether the winding has deformed by comparing the response curves of the winding at different frequencies.
5. Oil testing instruments
These instruments are suitable for oil-immersed transformers and are used to test the performance of transformer insulating oil. The core instruments and their functions include:
Oil dielectric strength tester: Measures the breakdown voltage of insulating oil to determine if the insulation strength of the oil meets the standard.
Trace moisture tester: Accurately measures the trace moisture content in insulating oil to assess the degree of oil dampness.
Gas chromatograph: Analyzes the composition and content of dissolved gases in insulating oil, which is an effective means to diagnose latent faults (such as overheating and partial discharge) inside the transformer.
6. Comprehensive and high-voltage testing instruments
These instruments are mainly used to conduct the final insulation strength assessment of transformers and integrate multiple test functions to improve testing efficiency. The core instruments and their functions include:
Ultra-low frequency high-voltage generator / AC withstand voltage test system: Applies an AC voltage higher than the rated voltage to the transformer to test the withstand voltage strength of the main insulation.
DC high-voltage generator: Used to conduct DC withstand voltage tests and leakage current tests on transformers to evaluate insulation performance.
Comprehensive test bench: Integrates multiple test functions such as ratio, DC resistance, and inter-turn detection to achieve one-stop testing of multiple items of the transformer, improving the degree of automation and testing efficiency.
Post time: Jan-30-2026