Resonant test system UHV(L)

for electrical networksfor electrical machines and installationsfor substations

Product overview
The UHV(L) Inductance Adjustable Power Frequency AC Resonance Test System is a series-resonant test system designed for AC withstand tests on single hydro-generators (≤ 250 MW) and related high-voltage electrical apparatus. By tuning reactor inductance to the capacitive reactance of the test object, the system generates high test voltages with low input power while maintaining stable waveform quality and flashover protection.

Applications / Typical use

• AC withstand voltage testing of single hydro-generators up to 250 MW.
• High-voltage diagnostics, calibration and on-site testing for power generation and transmission equipment.

System composition

• AC power source
• Voltage regulator
• Excitation transformer
• High-voltage reactors (inductance-adjustable)
• High-voltage divider and measurement accessories

Operating Principle of Power Frequency AC Resonance Test System
The system operates on series resonance: the inductive reactance of the reactors is tuned to match the capacitive reactance of the test object (e.g., generator windings) at power frequency, producing resonance that enables high output voltages with minimal input current.

Product Characteristics

• High Efficiency and Compact Design: Due to full compensation of resonant reactive power, the power rating of the power supply and equipment is less than one-tenth of the capacity required by the test object (1/Q > 10). For the same capacity, the device offers compact size and light weight, along with high output capacity and low configuration power demand, resulting in cost-effectiveness, convenience, and safe operation.
• Superior Waveform Quality: Series resonance functions effectively as a current filtering circuit, ensuring that the current passing through the test object is predominantly fundamental current. The total harmonic distortion (THD) of the output voltage is extremely low, outperforming all existing AC voltage withstand equipment.
• Fault Current Limitation: In the event of flashover or breakdown, the short-circuit current through the test object is limited to less than one-tenth (1/Q) of the test current prior to the short circuit. This effectively prevents further damage to the fault point after breakdown.
• Safe Arc Extinguishing and Voltage Recovery: Following a flashover, the arc is automatically extinguished immediately. The process of restoring the resonant state voltage after arc quenching is a steady-state establishment process lasting several seconds. There is no risk of voltage overshoot or recovery overvoltage during the microsecond to millisecond transient process, ensuring safe operation.

Key Advantages of Power Frequency AC Resonance Test System

• High efficiency with low input power requirement due to series-resonant operation.
• Low total harmonic distortion (THD) of the output waveform, reducing flashover risk.
• Automatic arc extinguishing and protection against flashover or breakdown.
• Portable and adaptable design suitable for field/on-site testing.

Technical Parameters

• Rated output voltage: 0 ~ 60kV(AC RMS) and below
• output frequency: 50Hz
• Resonance voltage waveform: Pure sine wave, waveform distortion rate ≤1%
• Work system: Full power conticontrol consolenuous working time of 1min
• quality factor: 1040
• Maximum test capacity: 3000kVA and below
• Working power supply: 380V±15%、Power frequency 50Hz

What Are The Safety Protection Functions of Inductance Adjustable Power Frequency AC Resonance Test System

• Overvoltage protection: The output can be immediately cut off by setting "1.1 times the test voltage".
• Overcurrent protection: prevents equipment from being damaged by high current at the moment of breakdown of the test sample.
• Disharmony protection: Automatically shuts down when deviating from resonance due to flashover or parameter changes.
• Automatic recovery after flashing: This is also the most unique feature. Once the test sample undergoes non-destructive flashover, the resonance condition is disrupted, the voltage instantly disappears, and the arc is extinguished. The device will automatically re tune and attempt to resume testing with minimal damage to the equipment.