Core System Specifications

Stage-Wise Technical Breakdown

1. Upper Stage Transformer (HCTT 250kVA/500kV)

- **Thermal Resilience:**  
  110% overvoltage (550kV/60s) without insulation failure  
- **Insulation Resistance:**  
  >2500MΩ (HV-LV-earth)  
- **Duty Cycle:** 15min ON / 15min OFF ×8 cycles daily  
- **Cooling:** ONAN (Oil Natural Air Natural)

2. Lower Stage Transformer (HCTT-500kVA/500kV)

- **Measurement System:** 1000:1 ratio winding  
- **Oil Specifications:**  
  - Dielectric loss <0.5% @ 90°C  
  - Acetylene-free / Solidifying point >40°C  
- **Insulation Tests:**  
  10kV/1min (LV-HV-shell)

Certified Safety & Protection

• Grounding System:
  HV terminal earthed via 5/5A CT for real-time monitoring

• Surge Protection:
  3kV arresters on excitation & transfer windings

• Thermal Limits:

• Winding ΔT: <65K

• Oil surface ΔT: <55K

• Overload Capacity:
  125% current (0.625A) for 300s

Compliance Framework

- **Partial Discharge:** IEC 60270 Class II  
- **Insulation Coordination:** IEC 60071-1  
- **Safety:** IEC 61010-1 Cat IV  
- **Oil Testing:** ASTM D877 / IEC 60156

Operational Advantages

• Precision Control:
  ≤±5% voltage deviation in cascade mode

• Rugged Construction:
  IP67-rated insulated barrel design

• Maintenance Features:
  Oil injection/release valves + dielectric monitoring

Technical FAQs (Snippet-Optimized)

Q: What’s the maximum daily operational duration at 1000kV?
A: 2 hours total (8×15min cycles with 15min cooling intervals).

Q: Is this system suitable for HVDC component testing?
A: No – use dedicated DC test sets for capacitors/HVDC applications.

Q: Oil replacement criteria?
*A: When dielectric strength drops below 30kV/mm (per IEC 60296).*