In the assessment of insulation performance for electrical equipment, AC withstand voltage testing at 35 kV is a critical method for evaluating insulation strength and identifying localized insulation defects. On-site “35 kV withstand voltage testers” are not single-purpose universal instruments but rather complete high-voltage test systems that must be specifically configured according to the capacitance, test voltage, and duration required by the equipment under test. Improper selection can directly reduce the reliability of test results and, in severe cases, damage the insulation of the equipment being tested. Below, we categorize system types based on common test objects and analyze relevant technical considerations.
1. Variable Frequency Series Resonance System: Suitable for High-Capacitance Equipment
For equipment with large capacitance—such as 35 kV cross-linked polyethylene (XLPE) power cables, gas-insulated switchgear (GIS), and large power transformers—the variable frequency series resonance system is currently the mainstream testing solution.
This system operates on the resonance principle ωL ≈ 1/ωC, requiring the power supply to provide only the active losses of the system, significantly reducing the power capacity needed. This optimization leads to smaller overall size and weight, making it more suitable for on-site transportation and handling.
Taking a 35 kV/300 mm² power cable with a length of 1–2 km as an example, the rated capacity of the entire system typically ranges from 135 kVA to 270 kVA. The output voltage capability should cover 52 kV (based on the GB 50150-2016 standard for cable handover tests) up to 108 kV (suitable for switches and current/voltage transformers). The system mainly consists of a variable frequency power source, excitation transformer, resonant reactor, and capacitive voltage divider, all equipped with comprehensive overvoltage, overcurrent, and flashover protection. Delivering pure sine wave output, it accurately simulates real-world power frequency conditions, meeting technical requirements specified in standards such as GB 50150 (Electrical Installation Engineering – Electrical Equipment Handover Test Standard) and DL/T 596 (Preventive Testing Regulations for Electric Power Equipment).
2. Power Frequency Withstand Voltage Tester: Suitable for Low-Capacitance Equipment
For devices with low capacitive current—such as circuit breaker contacts, insulators, insulating tools, and small-capacity transformers—a power frequency withstand voltage tester based on step-up test transformers is appropriate.
These systems have simple structures and deliver 50 Hz power frequency output, with capacities generally ranging from 2 kVA to 20 kVA. Output voltage ratings can be selected as needed, including 50 kV, 100 kV, or higher levels.
For circuit breaker contact withstand voltage testing, some dedicated units feature a double-horn electrode configuration, applying high voltage directly across the contacts to avoid unnecessary electric field distortion around insulating porcelain bottles, thereby improving test accuracy and operational safety.
3. Key Configuration Guidelines for Typical Test Objects
- 35 kV Power Cables (Handover Test): Use a variable frequency series resonance system; reference test voltage: 52 kV (phase-to-ground); test duration: 60 minutes.
- 35 kV Switchgear and Circuit Breakers (Contact Test): Either a power frequency withstand voltage tester or a series resonance system may be used; reference test voltage: 95 kV–100 kV; test duration: 1 minute.
- 35 kV Power Transformers and Instrument Transformers: Use either a series resonance system or a power frequency withstand voltage test set; test voltage should match the equipment’s insulation level (e.g., 75 kV), and the capacitance of the device under test must be calculated to ensure proper reactance matching.
- Insulating Ropes and Protective Insulating Tools: Use a dedicated insulated support frame combined with a test transformer; both the frame and electrodes must withstand voltages exceeding 110 kV to prevent surface discharge or creeping flashover.
When selecting a 35 kV withstand voltage test system, careful consideration must be given to the capacitance characteristics of the equipment under test, required test voltage, and on-site operating conditions. For high-capacity equipment such as cables and GIS, frequency-variable series resonance testing is preferred to balance test performance and equipment portability. For low-capacitance test specimens like circuit breakers and insulating tools, power-frequency withstand voltage equipment offers better cost-effectiveness and practicality.
Regardless of the testing method selected, the entire system configuration must comply with current standards GB 50150 and DL/T 596. Prior to testing, preparatory tasks such as voltage divider calibration and protection parameter setting must be completed to ensure accurate test data and guarantee the safety of personnel and equipment.
Post time: Aug-26-2026