High Voltage Test Transformers: Key Equipment for Electrical Insulation Testing

High voltage test transformers (HVTT) are fundamental devices in power system insulation testing. Alongside series resonant test systems, they simulate extreme voltage conditions to verify equipment reliability against operational stresses, lightning strikes, and internal overvoltages.

Core Functions of High Voltage Test Transformers

HVTTs serve three critical roles in high-voltage laboratories:

• Power Frequency Testing: Generates AC voltages up to 2250kV to test long-term insulation endurance.

• Operational Surge Simulation: Produces "long-wavefront" switching impulses for UHV transmission research.

• Ancillary Power Supply: Provides input power for DC/impulse voltage generators.

Technical Characteristics vs Power Transformers

While sharing basic principles with power transformers, HVTTs feature distinct designs:

Series Resonant Test Systems: Advanced Solution

For ultra-high voltage testing (≥500kV), cascaded systems address size/weight limitations:

• Modular Design: Multiple units stack vertically to achieve MVAs.

• Frequency Tuning: Matches test object capacitance (30-300Hz range).

• Energy Efficiency: Q factors >50 reduce input power requirements.

Critical Applications in Power Systems

These systems validate insulation performance for:

• GIS Components: Partial discharge detection at 1.2U_n

• Transmission Lines: Corona loss measurement under wet conditions

• Substation Equipment: Switching impulse tests (250/2500μs waves)

Selection Criteria for Test Systems

Key parameters when specifying HV test equipment:

1. Voltage Class: 150% of maximum system overvoltage

2. Short-Circuit Current: ≥1A for clear fault detection

3. Cascading Capability: Synchronization accuracy <1% phase error

Conclusion

As power grids evolve toward UHV levels, high voltage test transformers and resonant systems remain indispensable for ensuring insulation integrity. Their ability to simulate real-world overvoltage scenarios helps prevent catastrophic failures in critical infrastructure.