220 kV power transformer is a high-voltage transformer used in transmission substations to step voltage up or down for efficient long-distance power transmission and distribution. It is a critical component of modern electrical grids.
Typical Specifications
·Highest System Voltage: 245 kV
·Rated Voltage: 220/132 kV, 220/110 kV, 220/66 kV, 220/33 kV, etc.
·Rated Power: 100–500 MVA (commonly 125, 160, 250, 315 MVA)
·Frequency: 50 Hz or 60 Hz
·Number of Phases: Three-phase
·Cooling Method: ONAN/ONAF, OFAF, OFWF
·Insulation: Mineral oil or natural/synthetic ester
·Vector Group: YNd1, YNd11, YNyn0+d11, etc.
·Tap Changer: On-Load Tap Changer (OLTC)
·Impedance: Typically 10–18%
Main Components
·Magnetic core
·High-voltage (220 kV) winding
·Low-voltage winding
·Transformer oil
·Main tank
·Conservator tank
·Radiators
·Cooling fans and oil pumps
·Silica gel breather
·High-voltage bushings
·Low-voltage bushings
·On-load tap changer (OLTC)
·Buchholz relay
·Pressure relief device (PRD)
·Oil and winding temperature indicators
·Oil level gauge
Common Voltage Ratios
·220/132 kV
·220/110 kV
·220/66 kV
·220/33 kV
·220/11 kV (industrial applications)
Typical Applications
·Extra-high-voltage transmission substations
·Grid interconnection stations
·Large industrial plants
·Renewable energy integration (wind and solar farms)
·Regional transmission networks
Typical Efficiency
·Full-load efficiency: 99.5–99.8%
·Expected service life: 30–50 years with proper maintenance
Protection Systems
·Differential protection (87T)
·Restricted earth fault (REF)
·Overcurrent protection (50/51)
·Earth fault protection (50N/51N)
·Buchholz protection
·Pressure relief protection
·Oil and winding temperature protection
·Overfluxing protection (24)
Routine Tests (per standards)
Typical factory acceptance tests include:
·Winding resistance measurement
·Turns ratio (TTR) test
·Insulation resistance (IR)
·Applied voltage test
·Induced overvoltage test
·Lightning impulse test
·Partial discharge measurement
·No-load loss and current
·Load loss and impedance voltage
·Oil dielectric strength and dissolved gas analysis (DGA)
Applicable Standards
IEC 60076 – Power Transformers
IEEE C57 series – Power Transformer Standards
IEC 60296 – Transformer insulating oils
IEC 60137 – Bushings for alternating voltages above 1 kV
A 220 kV transformer is one of the most common transmission-class transformers used by electric utilities worldwide, typically connecting 220 kV transmission systems to lower-voltage sub-transmission or distribution networks while handling power ratings from approximately 100 MVA to over 500 MVA.