400 MVA Transformer

Primary Voltage Ratings: 330kV
Secondary Voltage Ratings: 150kV
TYPE: Autotransformer
BIL: 950/550kV
Standards: DSTU EN 60076-1, GOST
Power Rating: 400MVA
Cooling Method: ONAN/ONAF/OFAF

The 400 MVA transformer, designed for temperate climates and outdoor use, operates effectively at elevations up to 1000 meters and temperatures from -40°C to +45°C. It features a high voltage rating of 330 kV and medium voltage of 165 kV, with a cooling system of ONAN/ONAF/OFAF. The transformer includes advanced safety and monitoring systems, a robust cooling and maintenance setup, and a reliable control cabinet. It ensures a high efficiency of 99.797%, with a service life of at least 30 years and an MTBF of 25,000 hours.

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The 400 MVA transformer is a three-phase, oil-immersed autotransformer with forced air and oil circulation cooling. It is a double-winding unit with a rated capacity of 400,000 kVA and voltage classes of 330 kV (HV) and 165 kV (LV). Designed for temperate climates and suitable for outdoor installation, it operates efficiently at altitudes of up to 1,000 meters and in ambient temperatures ranging from -40°C to +45°C.

Key Specifications

Rated Capacity: 400,000 kVA
High Voltage (HV): 330 kV
Medium Voltage (MV): 165 kV
Winding Connection: Yna
Longest Permissible Current: 979 A
Cooling System: Three-stage ONAN/ONAF/OFAF
Transformer Efficiency (PEI): 99.797%

Insulation and Voltage Ratings

Full Wave Lightning Impulse (LI):
- HV Winding: 950 kV
- MV Winding: 550 kV
Chopped Wave Lightning Impulse (LIC):
- HV Winding: 1050 kV
- MV Winding: 600 kV
AC Withstand Voltage (LTAC):
- HV Winding: 395 kV (ph-ground), 525 kV (ph-ph)
- MV Winding: 230 kV (ph-ground), 275 kV (ph-ph)
Neutral Insulation Class: 35 kV
AC Neutral Input Test Voltage: 85 kV

Cooling and Maintenance

Oil Preservation System: Elastic membranes air-bag type
Tank Design: Bell type with lower connector and additional oil sump
Cooler Group: Shut-off valves with visual indicators and easy maintenance access

Safety and Monitoring

Gas Relay: Two-float design with separate 'alarm' and 'trip' settings
Oil and Winding Temperature Indicators: Equipped with contacts for monitoring
Pressure Relief Valve: Includes actuation signalling contacts
Control Cables: Routed in stainless steel sleeves for protection against mechanical damage and sunlight

Additional Features

Control Cabinet: IP55 protection, automatic temperature maintenance, dual power sources, and LED lighting
Voltage Control Device: Vacuum diverter switch of OLTC with a 1250 A rated current
Tap Changer Range: ±8.4% to +7.2% with 8 steps

Reliability and Longevity

Mean-Time-Between-Failures (MTBF): Minimum 25,000 hours
Operational Service Life: Minimum 30 years

This 400 MVA autotransformer combines advanced technology with rigorous standards to ensure exceptional reliability and efficiency for high-demand power applications.