The selection of a high-voltage insulation resistance tester is the first crucial step in ensuring the effectiveness of the test and the safety of the operation. During the selection process, the following core factors need to be carefully considered, combined with the test requirements and the characteristics of the tested equipment for a comprehensive judgment:
1. Test Voltage
The test voltage is the core parameter for selecting a high-voltage insulation resistance tester. Its selection should be based on the rated working voltage of the tested equipment and in accordance with the corresponding international and national standards.
Selection principles: The test voltage should be higher than the rated working voltage of the tested equipment to simulate the electrical stress the equipment is subjected to during operation; however, the voltage should not be too high to avoid damaging the insulation layer of the equipment.
Common test voltage levels: 50V, 100V, 250V, 500V, 1000V, 2500V, 5000V, 10kV, 15kV, etc.
Standard selection reference: Refer to IEEE 43-2013 and other relevant standards. Different rated voltages of the tested equipment correspond to the appropriate test voltage ranges:
Rated voltage < 100V of equipment (such as communication lines): Suitable for 100V or 250V test voltage;
Rated voltage 100V – 1000V of equipment (such as low-voltage motors, low-voltage cables): Suitable for 500V or 1000V test voltage;
Rated voltage 1kV – 35kV of equipment (such as medium-voltage motors, transformers, switch cabinets, medium-voltage power cables): Suitable for 2500V or 5000V test voltage;
Rated voltage > 35kV of equipment (such as high-voltage cables, large generators): Suitable for 5kV, 10kV or 15kV test voltage.
Selection conclusion: Based on the rated voltage range of the main test objects, select the instrument with the corresponding test voltage ranges.
2. Range
The range refers to the maximum insulation resistance value that the instrument can measure, directly determining the instrument’s suitability for different insulation state equipment.
Selection principles: The instrument’s range should comprehensively cover the possible insulation resistance values of the tested equipment, including the high resistance values of new equipment and the low resistance values of severely aged equipment.
Common range range: From several megohms (MΩ) to several terohms (TΩ, 1TΩ = 1,000,000 MΩ), high-end instrument ranges can reach 5TΩ and above.
Selection suggestion: For the testing requirements of high-voltage power equipment (such as high-voltage cables, generators, etc.), it is recommended to choose a model with a range of at least 1TΩ or above to ensure accurate measurement and recording of the subtle changes in equipment insulation performance, providing data support for status analysis.
3. Accuracy
Accuracy represents the accuracy of the instrument’s measurement results and is an important indicator for measuring the reliability of the measurement data.
Selection principles: The higher the instrument’s accuracy, the stronger the reliability of the measurement results, and the corresponding equipment cost will also increase. It is necessary to balance accuracy and cost based on the test requirements.
Common accuracy indication: In the industry, it is often indicated by the reading ratio, such as ±5% reading, ±3% reading, etc.
Selection suggestion: If only for equipment preventive tests and insulation performance trend analysis, an accuracy level of ±5% can meet the routine requirements; if for equipment research and testing or precise diagnosis of insulation status, it is recommended to choose a model with an accuracy of ±3% or higher.
4. Short-circuit Current
Short-circuit current refers to the larger current that the tester can output when measuring low-resistance insulation equipment, significantly affecting the test efficiency and data accuracy of capacitive equipment.
Function importance: A larger short-circuit current (usually ≥ 3mA) can help capacitive equipment such as long cables, large generators achieve rapid and stable charging, thereby obtaining more accurate measurement readings; at the same time, it can effectively “break through” the local insulation weaknesses of the equipment, accurately detecting insulation defects. Selection suggestions: If the daily test objects include large capacitive power equipment, it is recommended to choose models with a higher short-circuit current (such as 5mA or above).
5. Special functions
In addition to the basic testing functions, you can select instruments with corresponding special functions based on the actual test scenarios and diagnostic requirements to enhance the comprehensiveness of the test and the accuracy of the diagnosis. The core selectable functions and applicable scenarios are as follows:
PI/DAR (Polarization Index / Absorption Ratio Test): This is the core diagnostic function for determining whether insulating materials are damp or contaminated, and is a necessary function for testing power equipment such as motors and transformers;
SV/DD (Step Voltage / Dielectric Discharge Test): It can accurately diagnose insulation aging problems and local insulation defects, and belongs to advanced insulation diagnostic functions;
Voltage Ramp Mode: The test voltage gradually increases, allowing for real-time observation of leakage current changes, suitable for diagnosing equipment with relatively fragile insulation layers to avoid insulation damage caused by direct high-voltage testing;
Automatic Calculation and Storage: It can automatically calculate key indicators such as PI/DAR, and simultaneously store test data and change curves, facilitating subsequent data analysis, trend comparison, and test report preparation;
Data Interface: Equipped with USB, Bluetooth, etc., it enables rapid transmission of test data, improving the efficiency of data organization and sharing;
Protection Grade: For on-site outdoor testing scenarios, the IP dust-proof and water-proof grade of the instrument must meet the requirements of the on-site usage environment to ensure the stability and service life of the instrument.
Post time: Jan-21-2026