Variable Frequency Series Resonance Test Equipment for High Voltage AC Testing

High voltage AC withstand testing is an important procedure to verify the insulation performance of electrical equipment before commissioning and during maintenance.

Power cables, transformers, GIS, switchgear and generators must pass withstand voltage tests to ensure reliable operation in power systems.

However, traditional high voltage test equipment often faces challenges during field applications:

• Large power supply requirements
• Heavy equipment transportation
• Difficult operation in complex environments
• High requirements for testing sites

For modern power engineering projects, engineers need a testing solution that can provide high voltage output while maintaining portability and efficiency.

This is why variable frequency series resonance test equipment has become increasingly popular in power testing applications.

Variable frequency series resonance testing uses the resonance principle between the reactor and the capacitance of the tested equipment.

During testing, the system adjusts the output frequency to reach the resonance point. At this condition, a relatively small input power can generate a high test voltage required for AC withstand testing.

Compared with traditional test methods, series resonance technology provides several advantages:

• Reduced power capacity requirement
• Smaller equipment size and weight
• Better output voltage waveform
• Lower risk of high short-circuit current damage
• More suitable for field testing

Power cables are one of the most common applications of variable frequency resonance systems.

During cable installation and commissioning, AC withstand testing helps engineers:

• Verify insulation quality
• Detect potential insulation defects
• Ensure safe operation after energization

For long-distance XLPE cable systems, resonance testing provides an effective solution because cable capacitance creates large test capacity requirements.

Transformers are critical components in substations.

Before operation, transformers require insulation tests to verify:

• Winding insulation condition
• Electrical strength
• Manufacturing and installation quality

Variable frequency series resonance equipment can provide stable AC test voltage for transformer insulation evaluation.

The system is also suitable for:

• GIS equipment
• Circuit breakers
• Busbars
• Generators
• Other high voltage electrical equipment

It helps power maintenance teams complete acceptance testing and preventive maintenance efficiently.

To meet the requirements of high voltage testing departments and power engineering companies, Wuhan Hongzhi Gaoce Electrical Technology developed the HZG1101 Variable Frequency Series Resonance Test Equipment.

The system consists of:

• Variable frequency control power supply
• Excitation transformer
• High voltage reactor
• Capacitive voltage divider

The modular reactor design allows flexible combination according to different voltage levels and test requirements.

It is suitable for:

• 10kV power equipment testing
• 35kV distribution systems
• 110kV substations
• 220kV transmission equipment
• Details: 0.1Hz VLF High Voltage Generator for AC Withstand Testing

The equipment can automatically scan the frequency range and quickly locate the resonance point.

This reduces manual adjustment time and improves testing efficiency.

HZG1101 supports:

• Automatic testing mode
• Manual operation mode
• Automatic tuning with manual voltage adjustment mode

Engineers can select different operation methods according to actual testing conditions.

The system integrates multiple safety protection functions:

• Over-voltage protection
• Over-current protection
• Zero-start protection
• Detuning protection
• Flashover protection
• Emergency shutdown

These functions help improve testing safety during high voltage operation.

• Rated power: 5.5–500kW
• Input voltage: Three-phase 380V or single-phase 220V
• Output voltage: 0–400V adjustable
• Output frequency: 20–300Hz
• Frequency resolution: 0.1Hz step adjustment
• Output current: 13–1250A

• Output voltage waveform distortion: <1.0%
• Quality factor: Q>50
• Measurement accuracy: 1.5%
• Continuous operation time: 15 minutes under rated conditions

• Rated voltage: 0–1000kV
• Rated current: 1–10A
• Inductance range: 30–600H
• Working frequency: 20–300Hz

As power networks continue to expand, reliable insulation testing has become essential for preventing equipment failures.

Variable frequency series resonance test equipment provides power engineers with a safer, more efficient and practical method for high voltage AC withstand testing.

With flexible configuration, automatic tuning capability and advanced protection functions, HZG1701 helps improve testing efficiency for cables, transformers, substations and other high voltage electrical equipment.