INSTALLATION OF 500MVA TRANSFORMER AT PGCIL
- 1. INTERNSHIP ON ERECTION, COMMISSIONING AND PRE- COMISSIONING OF 500MVA TRANSFORMER PRESENTED BY AKINAPELLI RAHUL 161230007 Internship at 400/220KV POWER GRID WARANGAL-SS Submitted at NATIONAL INSTIUTE OF TECHNOLOY DELHI
- 2. PGCIL PGCIL –POWERGRID CORPORATION OF INDIA LIMITED Incorporated on 23 October 1989 under the Companies Act, 1956 with an authorized share capital of Rs. 5,000 Crore. POWERGRID transmits about 50% of the total power generated in India on its transmission network. Its transmission network consists of roughly 148,838 circuit kilometres and 236 EHVAC and HVDC substations, which provide total transformation capacity of 332,163 MVA. POWERGRID's interregional capacity is 75,050 MW.
- 3. POWER TRANSMISSION THROUGH GRID SYSTEM
- 4. SINGLE LINE DIAGRAM OF POWER GRID
- 5. DUTIES OF 400/220KV PGCIL WARANGAL-SS Connects three power plants with 400KV lines Khammam Bhupalpally Ramagundam Supplies power to two cities with 220KV lines Nagaram Durshed Uses ICT’s to step down voltage from 400KV to 220KV. One 500MVA ICT Two 315MVA ICT
- 6. 500MVA INTER CONNECTING TRANSFORMER AND ITS PARTS Provided with 3 windings •Primary winding of 400KV and star type •Secondary winding of 220KV and star type •Tertiary winding of 33KV and delta type Parts of 500MVA ICT •Main Tank •Laminated Core •Windings •Transformer Oil •Conservator Tank •Breather •Radiator •Buchholz Relay •Pressure relief valve •Tap Changer
- 7. ERECTION AND UNLOADING TRANSFORMER Unloading of transformer Erection process • External and internal inspection • Final tightness test with vacuum and pressure. • Oil filling • Hot oil circulation using oil filter machine
- 8. PRE-COMMISSIONING CHECKS • 1st step is to prepare testing program schedule. • Next step is pre-commissioning checks Examples :- a. Should be from visible defects, b. All the valves are tightened properly, c. Oil is filled up to desired level in bushings, main tank, conservator tank and also in OLTC etc,. d. All the cables are tightened and etc,.
- 9. PRE-COMMISSIONING TESTS SFRA test: Sweep Frequency Response Analysis is to evaluate the mechanical integrity of core, windings and clamping structures by measuring their electrical transfer functions over a wide frequency range. Performed at 10V AC from 20Hz-20MHz supply Eg :- Voltage and Turns ratio measurement: 1. Voltage ratio test uses digital multi meter performed at 415V. 2. Transformer turns ratio test uses automatic transformer turns ratio(TTR) meter performed at 110V.
- 10. • Performed to locate defect in magnetic core structure, shifting of windings, failure in turn to turn insulation or problem in tap changer. • Performed at 440V AC on HV side and LV side is open • Carried on min, normal and max tap positions. Magnetizing current test: • Performed to check balance in the magnetic circuit. • 1-phase 230V supplied between phase and neutral and measure the voltage induced in other two phases of the same winding. • Equipment used is digital multimeter. • When voltage is applied at R-phase, Y- phase should be 50-90% and B- phase should be in 20-40% • When voltage is applied at Y-phase, other two phases induced voltage should be in 30-70%. Magnetic balance test:
- 11. • Performed to detect winding movement which occurs due to heavy fault current or mechanical damage during transportation. • A 3 phase 440V supply is given to HV winding and LV is shorted . • Measure primary voltage and current in primary and secondary • Performed on min, normal and maximum tap positions. • Acceptance values should be within 3 % of impedance specified. Short circuit impedance test • BDV test acceptance value > 70KV • PPM test Moisture content < 5ppm Tan delta at 90 degree <0.01 Moisture content < 5ppm Oil characteristics test
- 12. OTHER REMAINING TESTS Capacitance and tan delta measurement Verification of vector group and polarity test Measurement of winding resistance Winding insulation resistance measurement Core insulation test Testing on bushing CT’s Measurement of earthing resistance
- 13. FINAL COMMISSIONING CHECKS All the test results are verified and compared with factory results before commissioning. No leakage oil in any part of unit. Ensure oil level in the Bushings Ensure that tertiary winding terminals are insulated, when they are not used. Ensure earthing of Neutral, main tank body, radiator frame structure, fans and motor. And all the final verifications, continuity between switchyard and transformer meters, connections, sensors, fans attached and etc,.
- 14. ENERGISATION OF UNIT 1st charge the transformer under no load for 24 – 48 hours. Gradually load the transformer observing the noise, vibration, temperature rise, oil leakage etc. Check OLTC operation. Carry out Thermo vision scanning of HV/LV terminals and tank body. Carry out DGA test of oil as per schedule given in flow chart of this manual.
- 15. THANK YOU!!!