HOW TO SAFE GUARD THE TRANSFORMER..???

Transcription

1 CPRI

2 HOW TO SAFE GUARD THE TRANSFORMER..??? CPRI Efficient and Effective network planning, Design and Forecasting Highly Reliable and Stable Protection system and co-ordination Measures to mitigate various faults and abnormal conditions Safe, rugged, optimum, economical and energy efficient design and manufacturing. Condition monitoring and Reliability centered maintenance

3 QUALITY CONTROL CPRI The totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs. QUALITY SYSTEM MUST ENSURE Uniformity of products Consistency in performance Reliability in service life Customer satisfaction

4 CPRI UNIFORMITY OF PRODUCTS: Using standard fittings, components and accessories CONSISTENCY IN PERFORMANCE: Good manufacturing practice Adequate testing at all stages Close monitoring to control process variable Ideal case of process control : zero-defect Any defect to be followed by root-cause analysis and necessary system level changes to be introduced

5 CPRI RELIABILITY IN SERVICE LIFE: Ensured by adequate design margins and over-load capacity Maintenance instructions & steps to be taken in case of break down, contingency plans and recovery procedures to be provided CUSTOMER SATISFACTION : Ease of operation, maintenance free Inter-changeability, rapid restoration of operation Clear documentation, availability of spares Speedy redressal of complaints

6 RISK POOL CRADLE-GRAVE RAW MATERIAL COPPER IRON DESIGN SUPPLY- CHAIN CORE INSULATION COSTING ACCESORIES COOLING MAINTENANCE &RLA DISASTERS R&R QUALITY CONTROL PROCESS FAULTS PROTECTION ERECTION AND COMMNG SHIPMENT TESTING & INSPECTION STORAGE& HANDLING

7 TEST ON TRANSFORMER AS PER IS:1180-1, 2014 Routine Tests: a) Measurement of winding resistance IS 2026 (Part 1). b) Measurement of voltage ratio and check of phase displacement IS 2026 (Part 1). c) Measurement of short-circuit impedance (principal tapping, when applicable) and load loss at 50 percent and 100 percent load IS 2026 (Part 1). d) Measurement of no-load loss and current IS 2026 (Part 1). e) Measurement of insulation resistance IS 2026 (Part 1). f) Induced over-voltage withstand test IS 2026 (Part 3). g) Separate-source voltage withstand test IS 2026 (Part 3). h) Pressure test (see 21.5). j) Oil leakage test (see 21.5).

8 TESTS ON TRANSFORMER AS PER IS:1180-1, 2014 Type Tests: a) Lightning impulse test IS 2026 (Part 3). b) Temperature-rise test IS 2026 (Part 2). NOTE - Maximum measured total loss (No load at rated excitation + load loss at maximum current tap converted to 75 ºC reference temperature) at 100 percent loading shall be supplied during temperature rise test. c) Short-circuit withstand test IS 2026 (Part 5) (up to 200 kva). NOTE Routine tests before and after short circuit test shall be conducted as per IS 2026 (Part 1). d) Pressure test (see 21.5)

9 TEST ON TRANSFORMER AS PER IS:1180-1, 2014 Special Tests: a)short-circuit withstand test IS 2026 (Part 5) (above 200 kva) NOTE Routine tests before and after short circuit test shall be conducted as per IS 2026 (Part 1). c) No load current at percent voltage (see 5.9.3). d) Paint adhesion tests. The test is performed as per ASTM D3359 (Standard Test Methods for measuring adhesion by Tape test). a)determination of sound levels IS 2026 (Part 10) e) BDV and moisture content of oil in the transformer (IS 335). NOTE Tests at d) and e) may be carried out on more than one unit subject to agreement between user and supplier

10 Pressure test 3, Non sealed (Plain tank) Type test (for 30 minutes) Routine test ( for 10 minutes) Corrugated tank Sealed (upto 200kVA) , upto 25kVA)

11 Vacuum Test (Type Test) 3 Transformers Upto 200 kva 250mm of Hg. for 30 minutes 3 Transformers >200kVA & upto 2500kVA 500mm of Hg. For 30 minutes

12 Oil Leakage test (Type test) Non-sealed &sealed Type Transformers: Pressure of Twice the normal head measured at base of tank for 8 hours Tank with corrugations: Pressure of 15kPa measured at top of the tank for 6 hours.

13 Paint Adhesion test (Special Test) Major steps of the procedure: Criss-cross marks are made on tank painted surface using Criss-Cross cutter. Adhesion tape is pasted on this area. After few minutes, pasted adhesion test is forcefully pulled off from one length. No paint shall come out along with adhesion tape.

14 Implementation CPRI QUALITY CHECKS AT ALL STAGES OF MANUFACTURE : From receipt of raw materials to finished product Stage inspection Select samples randomly by batch, by lot Identify vendors and assess them Even the qualified vendors are subjected to surprise audit to short-list a few. This is called vendor qualification. Check for calibration of meters and and other measuring devices for valid calibration

15 Quality Check Schematic CPRI WINDING COMPLETE CORE ACTIVE PART ASSEMBLY COMPLETE TRANSFORMER

16 Mechanical tests Electrical tests Chemical tests WINDING Insulation Paper Hard Paper Press Board Mechanical tests Electrical tests Machining test Punching tests Mechanical tests Electrical tests Chemical tests CPRI Phenol resin paper tube Phenol resin paper test Mechanical, Electrical tests on tubes Cu wire conductor Visual & Dimension Control tests Mechanical tests Electrical tests OR Al. Wire conductor Visual & Dimension Control tests Mechanical tests Electrical tests Winding Visual & Dimensional Control Check for no. of turns Inspection control after winding assembly & winding finishing Visual & Dimensional Control after winding impregnation and pressing

17 QUALITY CONTROL CHECKS FOR TRANSFORMER CPRI A. PAPER COVERED CONDUCTORS (ALUMINIUM OR COPPER) Check visually and dimensionally for both bare and insulated conductors Test for percentage elongation and tensile strength (mech. Department) Test electrical conductivity and resistance

18 CPRI ACTIVE PART ( WINDING) Visual and dimensional check Check for correct number of turns Inspection of joints Dimensional check after impregnation and coil Compression

19 COMPLETE CORE CPRI Laminations Tests On Materials Visual And Dimensional Control During Process Of Slitting, Shearing, Punching, Deburring Of Laminations Complete core Assembly of core Visual and Dimensional Control High voltage test on core bolts Type test Core loss test of naked core

20 CPRI CORE LAMINATION (MATERIAL) Watt loss Stacking factor Surface insulation Visual and dimensional checks

21 CPRI LAMINATION (PROCESSING) Visual and dimensional check during slitting, Cutting, punching deburring CORE ASSEMBLY Visual and dimensional checks Verticality Dielectric test on core bolt Core loss test

22 Lid complete Visual & Dimensional control Lid Visual & Dimensional control of steel sht. Mechanical test chemical test ACTIVE PART ASSEMBLY Core coil assembly Tap changer (off-load) Visual & Dimensional control High voltage test Visual & Dimension Control tests Mechanical tests Milli volt drop test Insulator & Condenser bushings Visual & Dimensional control Active part Inspection Control LV & HV connections. Inspection Control Visual & Dimension Control tests Tap changer (on-load) OLTC Assembly Inspection Control Mechanical Test Electrical Test Ratio Test CPRI Transformers above 500 kva after Vaccum driving Ratio Test Power transformers

23 CPRI B. COMPLETE ACTIVE PART &TANK Dye penetration test for lifting lugs Ratio test on windings Visual and dimensional check on insulators Tap changer : torque test, operation test, Millivolt drop test, combined electrical operation Visual and dimensional checks for connections and joints Core bolt test Ratio test at terminals

24 C. TANK ASSEMBLY CPRI MATERIAL Visual and dimensional checks on tank steel sheets Mechanical test on steel sheet Chemical composition FABRICATION Visual and dimensional checks of tank Pressure test Dye penetration test on welded joints of tank GASKET Visual and dimensional check

25 D. OIL FILLING CPRI Check for leakage in tank and at gaskets Physical, chemical & electrical properties of oil Volume resistivity

26 TRANSFORMER CPRI Transformer complete Inspection control during / after mounting of accessories and devices Type tests Lightning Impulse test, Temperature Rise Test, Short circuit Test, Pressure Test Routine tests Visual & Dimensional control after painting & Final assembly Packing & Dispatch control CUSTOMER

27 F. TESTS ON ACCESSORIES Conservator - leakage test, dimensional Verification Radiators - dimensional checks Buchholz relay - leakage test, operation Pressure relief valve - operation Breather - dimensional check CPRI

28 CPRI Failure Modes During Short Circuit tests Radial forces failure modes: Buckling: Characteristic failure mode for inner winding Axial forces failure modes: Spiraling: Characteristic failure mode for inner and outer winding Collapse of end support Conductor tilting Bending of cables

29 Failure Analysis of Transformers CPRI Categories of failures generally observed and their probable cause of failure of Transformers : A) Major failures during or after Short circuit: 1.1 % change in % X after short circuit test beyond limits. 1.2) LV/HV bushing break during S. C test, subsequently oil comes out. 1.3) PRV operate during short circuit test. 1.4) Oscillogram voltage & current wave shapes get distorted. 1.5) Flash in tap changer noticed during SC test. 1.6) Transformers Oil get carbonized.

30 Failure Analysis of Transformers CPRI 1.7) Routine Test after Short Circuit test. - During DVDF voltage get collapsed. - No load current excessively high. - High voltage power frequency voltage collapse. - Magger (IR) value of winding gets zero. 1.8) After untanking of the transformer. - Winding assembly get completely distorted. - Spacers & blocks comes out from assembly. - Top or bottom permawood ring breaks. - Pressure bolts loosen, break or displace from its position. - Tie Rods get loosen,subsequently spacers and blocks also get loosen. - Base yoke channel loosen, subsequently core get disturbed. - Supports for holding tap winding leads get break or loosen.

31 Failure Analysis of Transformers CPRI B) Minor failures : (Before S.C. test): i) Megger (IR) of HV-E or LV-E zero. ii) High Voltage power frequency test HV-E or LV-E do not withstand. iii) Ratio at one of the tap or more taps beyond the tolerance limits as specified in the standard iv) Induced over voltage test fail to withstand., Indicate failure of inter turn in winding v) No load looses or load losses or both beyond the guaranteed limit as specified by the customer. vi) Tap Switch operation problem in the test either due to pin broken which connects handle rod and tap switch.

32 1.6MVA, 6.6/0.433 kv Transformer Observations: %change in % x beyond limit after 5 th shot, No Load current abnormally high, carbonized oil came out from PRV, arcing mark noticed on LV busbar, paper insulation of winding burnt.

33 630kVA, 22/0.433 kv Transformer Observations: %change in % x beyond limit after 7 th shot, No Load current abnormally high, end blocks & spacers found loose, V phase winding HV winding deformed.

34 1.5 MVA, 33/ 0.69 kv Transformer Observations: %change in % x beyond limit after 2 nd shot, abnormal sound noticed, oil carbonized, W ph HV winding damaged & conductor burnt, end blocks & spacers found displaced.

35 800KVA,33/0.433 kv Transformer Observation: %change in % x beyond limit after 8 th shot, variation in resistance, Delta lead found opened.

36 1.0MVA,11/0.433 kv Transformer Observation: waveform distorted, U & W ph LV busbar found bent & shorting with core. Arcing noticed between core & LV busbar.

37 1.0MVA, 11/0.433 kv Transformer CENTRAL POWER RESEARCH INSTITUTE,

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