Core System Specifications

Stage-Wise Technical Specifications

Upper Stage: HCTT625kVA/625kV-1

- **Input/Output:**  
  LV: 3kV/208.3A → HV: 625kV/1A  
- **Insulation Resistance:**  
  >2500MΩ (HV-LV-earth)  
- **Thermal Limits:**  
  Winding ΔT <65K, Oil ΔT <55K  
- **Duty Cycle:**  
  8×1hr cycles daily (1hr ON/OFF)

Sub Stage: HCTT-1250kVA/625kV-1

- **Power Handling:**  
  LV: 3kV/416.7A → HV: 625kV/1A  
- **Oil Specifications:**  
  - Acetylene-free  
  - Pour point >40°C  
  - Dielectric loss <0.5% @ 90°C  
- **Critical Protection:**  
  5/5A CT-monitored HV grounding

Certified Safety & Performance

• Voltage Stability:
  ≤5% deviation in cascade operation

• Environmental Resilience:

• Noise: ≤65dB(A) @ 4m (ISO 3746)

• Cooling: ONAN (Oil Natural Air Natural)

• Insulation Integrity:

• 10kV/1min (LV-HV-shell)

• 5kV/1min (measurement windings)

• Surge Protection:
  Integrated arresters on all windings

Compliance Framework

- **Partial Discharge:** IEC 60270 Class II  
- **Insulation Coordination:** IEC 60071-1  
- **Safety:** IEC 61010-1 Cat IV  
- **Oil Testing:** IEC 60156 + ASTM D877  
- **Temperature Rise:** IEC 60076-7

Technical Advantages

• Extreme Voltage Capacity:
  1375kV surge withstand (110% overload)

• Precision Diagnostics:
  PD detection <3pC @ 1000kV

• Robust Thermal Design:
  Certified 8-cycle daily operation at 1250kV

• Measurement Integrity:
  ≤3% waveform distortion under load

Operational FAQs (Snippet-Optimized)

Q: Maximum ambient temperature for full-load operation?
*A: Rated for 45°C ambient (IEC 60076-12) with ΔT safeguards.*

Q: Oil maintenance protocol?
*A: Replace when dielectric strength <30kV/mm (IEC 60296) or DGA shows acetylene.*

Q: Calibration interval for PD measurement?
*A: Annual calibration per IEC 60270 using NIST-traceable pulse generators.*