How to Perform AC Withstand Testing on 35kV Power Apparatus Using a YDQ-10kVA/100kV Gas-Insulated Test Transformer

How to Perform AC Withstand Testing on 35kV Power Apparatus Using a YDQ-10kVA/100kV Gas-Insulated Test Transformer

A gas-insulated test transformer is an AC high-voltage step-up testing device filled with sulfur hexafluoride (SF6) gas medium to supply power-frequency dielectric withstand voltage for electrical insulation assessment. The YDQ-10kVA/100kV gas-insulated test transformer is specifically engineered to perform high-voltage insulation tests on power transformers, circuit breakers, cables, and switchgear operating at voltage levels up to 35kV in compliance with IEC 60060-1 and IEEE Std 4.

What Are the Core Technical Specifications of the YDQ-10kVA/100kV Transformer?

When selecting portable diagnostic apparatus for 35kV distribution assets, technical parameters must precisely align with insulation coordination requirements. The YDQ-10kVA/100kV model features an SF6 gas dielectric strength rated at 0.4 MPa nominal pressure, reducing structural mass to 40%–60% of equivalent oil-immersed test sets. Operating at a primary excitation voltage of 200V, it steps up output linearly to 100kV AC at 100mA rated current.

How Does SF6 Gas Insulation Improve On-Site Portability and Safety?

Field maintenance on remote 35kV substations requires lightweight equipment to decrease labor intensity during transport. Utilizing high-purity SF6 dielectric gas (per IEC 60376) enables tight clearance between high-voltage windings and the grounded aluminum alloy casing. This design eliminates oil leakage, fire hazard, and explosive risks associated with mineral oil dielectric fluids (IEC 60156 / ASTM D877).

The hermetically sealed vessel prevents moisture ingress and ambient particulate contamination. Consequently, the YDQ-10kVA/100kV unit maintains stable breakdown voltage across ambient temperature ranges from -20°C to +50°C without requiring periodic oil filtration or vacuum degreasing.

What Is the Operating Procedure for 35kV Equipment High-Voltage Withstand Testing?

Step 1: Pre-Test Setup and Pressure Check

Verify that the SF6 pressure gauge displays a reading within 0.38–0.42 MPa. Connect the safety ground terminal of the gas-insulated test transformer to the main station earthing grid using a copper cable with a minimum cross-section of 16 mm².

Step 2: Circuit Interconnection and Partial Discharge Suppression

Connect the primary excitation winding to the control bench output. Install a high-voltage current-limiting resistor (typically 1 Ω/V) between the HV output terminal and the 35kV device under test (DUT) to suppress arc surges during insulation breakdown.

Step 3: Voltage Ramping and Duration Execution

Apply power-frequency excitation at 50Hz/60Hz. Ramp the output voltage at 2 kV/s up to the standard test level (e.g., 85 kV AC for 35kV switchgear per IEC 62271-200). Hold the target voltage for 60 seconds while monitoring leakage current on the precision metering circuit.

Q: Can the YDQ-10kVA/100kV gas-insulated test transformer be used for partial discharge (PD) measurements?

A: Yes. Due to its optimized internal electric field distribution and high-purity SF6 gas insulation, internal background partial discharge remains below 5 pC at full 100kV output. When paired with high-frequency current transformers (HFCT) or acoustic sensors compliant with IEC 60270, it allows accurate detection of insulation defects without background noise interference.

Q: How does the pricing and total cost of ownership (TCO) compare to oil-immersed test transformers?

A: While the initial purchase price of an SF6 gas-insulated test transformer is approximately 15%–25% higher than traditional oil-immersed units, its maintenance-free structure eliminates oil sampling, fluid re-conditioning, and seal replacement costs, delivering a lower 5-year TCO for field diagnostic teams.