THIẾT KẾ CƠ BẢN TRẠM BIẾN ÁP 400kV .
“Design of 400/220kV Sub-station” Sanjay Chatterjee 27th April 2008 Srex Power India Private Limited Includes Overview of 400kV sub-station Design Process Design considerations Question / Answer Imp considerations in substation design Safety of personnel and equipment Reliability and Security Adherence to Statutory obligations – I.E rules, Environmental aspects Electrical design considerations Structural design considerations Ease of maintenance Possibility to Expand System parameters Sr Description 400kV 220kV Nominal system voltage 400kV 220kV Max operating voltage 420kV 245kV Rated frequency 50Hz 50Hz Number of phases 3 System neutral earthing Effectively earthed Corona Extinction voltage 320kV 156kV Min creepage distance 25mm/kV 25mm/kV Rated short ckt Current for sec 40kA 40kA 10 Radio interference voltage at 1MHZ (for phase to earth voltage) 1000 mV (320kV) 1000 mV (156kV) System parameters Contd Sr Description 400kV 220kV 11 Rated insulation levels i) Full wave impulse withstand voltage for lines for reactor/ X’mer for other equipments 1550kVp 1300kVp 1425kVp 1050kVp 950kVp 1050kVp ii) Switching impulse withstand voltage (dry/wet) iii) One power freq withstand voltage (dry/wet) for lines for CB / Isolator for other equipments Remarks 1050kVp 680kV 520kV 610kV 630kV 460kV 460kV 530kV 460kV (Line-ground) (open terminals) Substation Bird’s view 400kV Circuit Breaker 400kV Isolator 400kV Current Transformer 400kV CVT Mesh (Ring) busbar system Merits Busbars gave some operational flexibility Demerits If fault occurs during bus maintenance, ring gets separated into two sections 2.Auto-reclosing and protection complex Requires VT’s on all circuits because there is no definite voltage reference point These VT’s may be required in all cases for synchronizing live line or voltage indication Breaker failure during fault on one circuit causes loss of additional circuit because of breaker failure Remarks Most widely used for very large power stations having large no of incoming and outgoing lines and high power transfer Minimum Clearances 400kV 220kV Phase to Earth 3500 mm 2100 mm Phase to phase 4200 mm (Rod-conductor configuration) 4000 mm (Conductor-conductor configuration) 2100 mm Sectional clearance 6400 mm 4300 mm Clearance Diagram Bus Bar Design Continuous current rating Ampacity caculation as per IEEE:738 Short time current rating (40kA for Sec.) IEC-865 Stresses in Tubular Busbar Natural frequency of Tubular Busbar Deflection of Tube Cantilever strength of Post Insulator Aeolian Vibrations Gantry Structure Design Sag / Tension calculation : as per IS: 802 1995 Sr Temp Wind Pressure Limits Min No wind Min 36% Every Day No wind T