1. Structural Design and Mechanical Strength
Seismic Performance:
Hydropower stations are often located in areas with complex geological conditions. Transformers must have good seismic performance to withstand the impact of natural disasters such as earthquakes.
Mechanical Strength:
Transformers must have sufficient mechanical strength and rigidity during transportation, installation, and operation to prevent deformation or damage.
2. Insulation and Dielectric Strength
Insulation Level:
Transformers must meet high-standard insulation requirements, including lightning impulse withstand voltage, switching impulse withstand voltage, and short-time power frequency withstand voltage. For example, the lightning impulse withstand voltage of a 500kV transformer must reach 1550kV (peak).
Moisture and Contamination Protection:
Hydropower stations have high humidity environments. Transformers must have moisture-proof and contamination-proof measures to ensure that insulation performance is not affected by the environment.
3. Cooling and Temperature Rise Control
Cooling Method:
Transformers must use an efficient cooling system, such as oil-immersed cooling (ONAN) or forced oil circulation air cooling (OFAF), to ensure that the temperature rise does not exceed the limit during full-load operation.
Temperature Rise Limit:
The top oil temperature rise should not exceed 60K, the average winding temperature rise should not exceed 65K, and the hot spot temperature rise should not exceed 70K.
4. Electrical Performance
Rated Parameters:
Transformers must meet the rated voltage, rated capacity, and frequency requirements of hydropower stations. For example, the rated capacity of a 500kV transformer is usually 360MVA, with a rated frequency of 50Hz.
Short-Circuit Impedance:
Short-circuit impedance must be controlled within a reasonable range to reduce the impact of short-circuit current on the system.
Voltage Regulation Method:
Choose no-excitation voltage regulation or on-load voltage regulation according to needs to ensure voltage stability.
5. Environmental Adaptability
Protection Level:
The enclosure protection level of the transformer must reach IP23 or higher to prevent the ingress of dust, small animals, and moisture.
Special Environment Adaptation:
Adapt to special environmental conditions such as high altitude, high humidity, and extreme temperatures.
6. Safety and Reliability
Five-Prevention Functions:
High-voltage switchgear must be equipped with “five-prevention” interlocking devices to prevent misoperation.
Grounding System:
Transformers must have a reliable grounding system to ensure safe operation.
Fault Monitoring:
Some transformers need to be equipped with intelligent monitoring systems to monitor the operating status in real-time and detect and handle faults in a timely manner.
7. Environmental Protection and Energy Saving
Low-Loss Design:
Transformers must use low-loss materials and technologies, such as low-loss silicon steel sheets, to reduce no-load and load losses.
Environmental Materials:
Prioritize the use of environmentally friendly insulating oil and recyclable materials to reduce environmental impact.
8. Special Technical Requirements
Excitation Transformer:
Transformers used in the excitation system of hydro-generator must meet the DL/T 1628-2016 standard to ensure the stability and reliability of the excitation system.
Three-Phase Integrated Design:
Some hydropower stations use three-phase integrated transformers to reduce land occupation and improve operating efficiency.
