Substations operating at voltages exceeding 800 kV are considered Ultra High Voltage (UHV) substations. The technical requirements for equipment in such substations are stringent due to the high voltage levels involved. Here are the key technical requirements for substation equipment exceeding 800 kV:
Insulation Design:
- Substation equipment for UHV applications requires robust insulation systems capable of withstanding high electric field stresses and voltage levels exceeding 800 kV.
- Insulation materials with high dielectric strength, such as SF6 gas for gas-insulated switchgear (GIS) and oil-impregnated paper for transformers, are commonly used to ensure reliable insulation performance.
Voltage Stress Management:
- Equipment design must incorporate measures to manage voltage stresses, such as shaping of conductor profiles, optimization of insulation thickness, and use of grading rings or shields to distribute electric fields evenly and reduce stress concentrations.
Clearances and Creepage Distances:
- Adequate clearances and creepage distances are essential to prevent flashovers and insulation breakdowns in UHV substations.
- Equipment design should adhere to international standards and guidelines for determining clearances and creepage distances based on the rated voltage levels and pollution severity of the operating environment.
Material Selection:
- High-quality materials with superior mechanical, thermal, and electrical properties are required for UHV equipment construction.
- Insulating materials, conductors, bushings, insulators, and enclosure materials must be carefully selected to ensure durability, reliability, and long-term performance under extreme operating conditions.
Switching and Fault Current Handling:
- UHV equipment must be capable of interrupting and withstanding high fault currents associated with the transmission of large power flows.
- Circuit breakers, disconnectors, and other switching devices should be designed to handle fault currents exceeding several thousand amperes and provide rapid fault clearance to maintain grid stability.
Temperature Management:
- Efficient cooling systems are essential to manage temperature rise in UHV equipment and prevent overheating under continuous or transient loading conditions.
- Cooling methods such as natural convection, forced air cooling, oil circulation, or gas circulation may be employed depending on the type and size of the equipment.
Mechanical Strength and Stability:
- UHV equipment must be designed to withstand mechanical stresses, including wind loads, seismic forces, and thermal expansion/contraction effects.
- Structural analysis, finite element modeling, and testing are conducted to verify the mechanical strength and stability of equipment under various operating and environmental conditions.
Reliability and Maintenance:
- UHV equipment must demonstrate high reliability and require minimal maintenance to ensure uninterrupted operation and minimize downtime.
- Design features such as redundant systems, condition monitoring, remote diagnostics, and predictive maintenance capabilities are incorporated to enhance equipment reliability and service life.
Safety and Environmental Compliance:
- UHV equipment design should prioritize safety for personnel and environmental protection.
- Safety features such as interlocks, grounding systems, insulation monitoring, and protective enclosures are implemented to mitigate risks of electric shock, arc flashes, and environmental hazards.
Testing and Certification:
- UHV equipment undergoes rigorous testing and certification procedures to validate performance, reliability, and compliance with international standards and regulatory requirements.
- Type tests, routine tests, and special tests are conducted on individual components and complete assemblies to ensure conformity to specifications and standards.
By meeting these technical requirements, substation equipment exceeding 800 kV can effectively support the transmission of electricity at ultra-high voltage levels, enabling efficient and reliable operation of UHV substations in power transmission networks.
