Operation and Maintenance of 220KV Receiving Substation

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Operation and Maintenance of 220KV Receiving Substation Chavan P.LStudent Member IEEE, G. Suchitra Member IEEE and Jangamshetti S.H Senior Member IEEE Abstract–This paper presents operation and maintenance of 220kv substation. Different maintenance schedules are mentioned. Current, voltage, power and reactive power are noted for 100MVA power transformer and 220KVlines at 220/110/33/11KV receiving substation Semikeri, Bagalkot, KPTCL. Load on transformer and lines analyzed. Planned maintenance schedule keeps the substation equipment in proper working condition to provide maximum reliability, flexibility in operation, continuity of service with reduce down time and reduce the cost of operation and maintenance. I. INTRODUCTION Maintenance is a key activity for utilities in order to assure the proper operation of the networks. And it implies a huge amount of human and economic resources. Saving Maintenance costs means that it is needed to proper operation of substation equipments. The availability of reliable and quality power has made the job of substation more important. This can be achieved by establishing the new substation, with most efficient and reliable equipments and taking more care in their operation and maintenance. Maintenance may be defined as the upkeep of the substation electrical equipment in proper working and efficient condition to derive the Reliable and efficient operation, Optimum utilization Availability of quality power, reduced down time, Detection of premature faults, Minimizing revenue losses etc. To meet the above requirement, the equipment has to be checked, attended to, trouble shoots and operated under specified conditions. A large percentage of failure of electrical equipment are due to deterioration of insulation, loose contact, abnormal operating condition etc. many of these failure can be anticipated by regular application of simple tests and timely maintenance . If the fault condition leading to failure is detected in the early stage itself, the extent of damage can be reduced and the equipment can be reconditioned and put back in to service. Any abnormality will be followed by warming signal like variation in sound, excess temperature, vibration, sparks, blown out fuses, frequent trappings, tripping before full load. The detection of incipient faults in electrical equipment depends up on use of proper diagnostic tools, its effective use, correlation and proper interpretation of test results and observation based on experience, manufacturers guidance etc. II. MAINTENANCE ACTIVITY 1. Corrective or breakdown maintenance. 2. Preventive maintenance.

3. Condition based maintenance. 4. Reliability centered maintenance. 5. Equipment failure analyses. 6. Techniques for reducing down time. 7. Spare management. 8. Documentation/ computerization on maintenance. Corrective or breakdown maintenance is carried out as and when necessary. This applies only to low value and auxiliary equipments, breakdown of which does not affect power supply continuity. Preventive maintenance calls for advance plan is made to carry out preventive maintenance. The advantage lies in uninterrupted power supply, increased availability of the equipment and reduction in maintenance cost. Condition base maintenance is based on condition assessment of the equipment by tests ON or OFF the line. This is ideal for prevention of equipment failure and other associated consequent damages. Reliability centered maintenance is generally carried out on old equipment by conducting ‘ remaining life assessment studies’ and based on economics, life extension techniques are adopted without sacrificing reliability and availability. The maintenance costs are also reduced. Equipment failure analysis is the major responsibility of maintenance personnel to prevent repeated failure of equipment and provide inputs foe necessary change in design parameters, new equipment design, quality control plan, erection and subsequent maintenance technique. Techniques of reducing down time play a vital role in continuity of power supply. Hot line maintenance of one line of double circuit line with other circuit in live condition, deployment of emergency restoration system etc, is few examples. Spares management ensures availability of right spares most frequently required and at the right location and thereby help immediate restoration of power supply. The documentation is a record of the type of maintenance activity carried out, any abnormalities noticed during checking etc, chronologically documented and computerized for further analysis and action. III.SUBSTATION EQUIPMENT Equipments installed at 220/110/33/22KV substation Semikeri, Bagalkot,KPTCL.

receiving

2 TABLE-1: Equipments installed at 220/110/33/22KV receiving

substation Semikeri,Bagalkot,KPTCL

SL.No 1

100MVA, 220/110/11kV Power Transformers

100MVA

Rating

Numbers

2

20MVA

1

10MVA

1

4

20MVA, 110/33kV Power Transformer 10MVA, 110/33kV Power Transformer Current transformer

5

Potential transformer

6

SF6 Circuit breaker

7

Isolators

8

lighting arrester

220KV class 110KV class 33KV class 11KV class 220KV class 110KV class 33KV class 11kV class 220KV class 110KV class 33Kv class 11KV class 220KV class 110KV class 33KV class 220KV class 110KV class 33KV class

36 48 12 33 6 6 3 3 7 16 5 11 34 75 11 6 15 5

3

Equipment

2

IV.MAINTENANCE SCHEDULE Maintenance schedule is categorized into daily, weekly, monthly, quarterly and yearly maintenance schedules. Maintenance for 1. Power transformer (100 MVA, 20MVA, 10MVA) 1. Check and re-condition of silica jelly. 2. Check the working cooling fans, pumps 3. Release gas from BH relay 4. Clean the bushing, radiator, body etc., 5. Check earthing connection 6. Check jump connections 7. Check OLTC motor drive and control panel i) Lubricate bearing and cleaning ii) Check the gear box oil level iii) Check operation of limit switch, sequence switch with transformer in off conditions iv) Check gasket joints for oil leakage 2. HT Circuit breakers 1. Clean the porcelains 2. Check the connections for loose contact 3. Check tripping through relays 4. Check the wiring for loose contact 5. IR valves, oil level for MOCB;s 6. Vermin Proofing of control box 7. Check annunciation scheme 8. Lubricate moving/link mechanisms wherever recommended by manufacturer 9. Replacement of Oil (in case of MOCB;s) 3. HT: CT’s, PT’s & Lightning arresters. 1. Clean the porcelain and metal body 2. Check connection both primary and secondary for tightness 3. Check oil level 4. Take IR values

5. Check earth connection for proper contact 4. 11 kV Switchgears 1. Clean the breakers, panels and bus bars thoroughly, clean insulators with CTC or Petrol 2. Check II values of the bus bars and individuals, breakers between phases and earth 3. Check operation of breakers on local remote through relay and corresponding annunciation 4. Check and lubricate operating mechanism wherever necessary 5. Tighten the terminal connection of all auxiliary circuit and wiring 6. Check all earth connections between the panel and electrodes for tightness and check the contact resistance of earth connection. 7. Replace oil in MOCB’s as recommended by supplier, check oil condition in BOCB’s and replace if necessary 8. Check contact travel, contact erosion in MOCB’s and BOCB’s 9. Check 11 kV CT’s and PT’s connections 5. Isolator 1. Check jump connection and replace PG clamps, if necessary 2. Check the alignment of isolator 3. Cleaning and applying petroleum jelly to contacts 6. GOS-HR fuses –Station yard Earthing 1. Check clean and grease the GOS and check contacts for erosion, clean insulator 2. Check operation for proper closing of the insulator 3. Check the fuses and renew the same wherever HR fuses are provided 4. Check the earth resistance of earthing mat and all individual earthing if any, the resistance should be within the prescribed limit, otherwise action should be taken to Bering the same to within limit immediately as it is very important aspect for the safety of the equipment in any station. TABLE.2: Maintenance Schedule for Oil-Filled Power Transformers Maintenance or Test

Review equipment ratings Preventive maintenance

Transformer physical inspection Bushings – visual inspection Bushings - check oil level Bushings – cleaning Transformer and bushings Doble test Transformer and bushings– infrared scan Insulating oil - DGA, physical, and chemical tests Leakage reactance, Turns Ratio tests, SFRA test Cooling fans – inspect and test Oil pumps and motors - inspect and test Heat exchangers – inspect Conservator and bladder - inspect

Recommended Interval

5 years As Per manufacturer’s recommendations Annually Quarterly and 3-5 years Weekly 3-5 years 3-5 years (6 months to 1 year for suspect bushings) Annually Annually after first year of operation If problems are indicated by other tests Annually Annually Annually 3-5 years

3 Top oil and winding thermometers Oil level indicator operation Pressure relief device Sudden pressure relay Buchholz relay Inspect foundation, rails, trucks

Annually inspect and infrared scan 3-5 years calibrate 3-5 years Annually inspect and perform function test 3-5 years check oil leaks Annually inspect and perform function test 3-5 years test per manufacturer’s recommendations Annually inspect and perform function test 3-5 years

TABLE.3: Maintenance Schedule of SF6 Breaker Maintenance or Test

Review equipment rating Preventive maintenance

Record gas pressure and temperature, compare with tolerances Record operations counter Visual inspection Check foundation, grounds, paint Check external screws, bolts, electrical terminals tight Contact resistance test, power factor insulation test, motion analyzer, trip test, moisture test on gas Verify operation and calibration of temperature and pressure switches and gauges Check lube points, heater operation, tightness of terminals, linkages screws, bolts; latch, linkage, operating mechanism adjustments Overhaul breaker with new seals, contacts, nozzles Overhaul disconnect, grounding, and breaking switches Gas cart maintenance

Recommended Interval

5 years Per manufacturer’s manuals Monthly

instruction

5 years

10 to 15 years or 4,000 to 10,000 operations (more frequent if high current operation) 15 years or 5,000 to 10,000 operations

Recommended Interval

Solid-state relays Calibration and functional testing Microprocessor relays calibration and functional testing

Upon commissioning 1 year after commissioning and every 3 years Upon commissioning 1 year after commissioning and every 8-10 years Immediately upon installation and/or upon any changes in wiring and every 3-6 years Daily

Upon commissioning and every 2 years

5Years

Maintenance or Test

3-6 years Ambient dependent As soon as possible Annually

Recommended Interval

5 years Semi-annually Annually

Recommended Interval

5 years Annually

3-6 years Ambient dependent Annually

TABLE.8: Maintenance Schedule of Batteries Maintenance or Test Visual inspection Battery float voltage

instruction

5 years

Check red light lit for lockout relay and circuit breaker coil continuity Lockout relays Cleaning and lubrication

5 years Quarterly to semiannually 3-6 years Ambient dependent

TABLE.6: Maintenance Schedule for Transmission Lines

Review equipment ratings External visual inspection, Check and tighten connections, Check and clean enclosures Hipot (to ground and between phases) or Doble Infrared scan, while loaded if possible

5 years

Fault/load study and recalculate settings Electro-mechanical relays Calibration and functional testing

Protection circuit functional test, including lockout relays

Recommended Interval

TABLE.7: Maintenance Schedule for Buswork and Enclosures by

TABLE.4: Maintenance Schedule for Relays and Protection Circuits Maintenance or Test

Review equipment rating Visual inspection with binoculars Clean insulator and check connections Doble test (power frequency dielectric loss, direct current [DC] insulation resistance, power factor) Replace all silicon carbide arresters with metal oxide varistor type Infrared scan

Maintenance or Test

required

Per manufacturer’s manuals

Maintenance or Test

Review equipment ratings Visual inspection with binoculars Infrared scan

Monthly Monthly, annually,5 years 5 years Annually 5 years, if manufacturer

TABLE.5: Maintenance Schedule for Arresters

Cell float voltage Specific gravity Temperature Connection resistance Capacity testing Safety equipment inspection Battery monitoring system

Recommended Interval Monthly Shift (charger meter)Monthly overall battery voltage with digital meter compare with charger meter Monthly, pilot cells with digital meter Quarterly, all cells Monthly, pilot cells Quarterly, 10 percent (%) of cells Annually, all cells Monthly (pilot cell) ,Quarterly (10% of all cells) Annually, all connections 5 years, annually if capacity less than 90% Monthly, test all wash devices and inspect all safety equipment According to manufacturer’s recommendations

TABLE.9: Maintenance Schedule – Battery Chargers Maintenance or Test Preventive maintenance

Recommended Interval Dependent on charger type manufacturer’s recommendations

and

4 TABLE 10: MW/h load on incoming, outgoing lines, 100MVA Power transformer and Allotted by ALDC. On 4th July 2011

Hour

MW/h on incomi ng line.

MW/h on outgoi ng line. 72 72 96

60 62 54

64 65 65

11 12 13

126 130 142

66 68 76

60 62 66

60 60 57

14

162

90

72

57

15 16 17

140 144 152

84 86 84

56 56 64

57 55 56

18 19 20

134 118 116

78 74 68

52 44 46

57 59 65

8 9 10

132 142 150

MW/h on 100MVA Transformer

MW/h Allotted by ALDC ( load dispatch center)

Fig.1: MW load on 220 kV incoming line V/s time in hours

TABLE. 11: peak and min load on 100MVA 220/110 kV power transformer

Peak load in MW

1/7/11 2/7/11 3/7/11 4/7/11 5/7/11 6/7/11 7/7/11 8/7/11 9/7/11 10/7/11 11/7/11 12/7/11 13/7/11 14/7/11 15/7/11

86 96 80 72 60 62 54 50 52 60 78 88 66 58 60

Minimum load in MW 62 54 46 44 38 36 36 32 30 38 44 42 34 26 26

Fig.2: MW load on 220 kV outgoing line V/s time in hours

TABLE.12: Max and min KV, on 220KV, 110KV , 33KV,11KV lines.

Max

Min

Max

Min

11KV

Mi n

33KV

Max

110KV

Min

1/7/11 2/7/11 3/7/11 4/7/11 5/7/11 6/7/11 7/7/11 8/7/11 9/7/11 10/7/11 11/7/11 12/7/11 13/7/11 14/7/11 15/7/11

220KV Max

K V

215 220 219 220 220 220 220 220 220 218 220 215 220 224 220

198 190 202 205 208 210 200 205 200 198 190 190 190 208 198

114 112 113 112 114 115 114 115 114 112 115 113 114 115 115

100 100 104 105 106 108 108 104 101 100 99 100 102 108 100

33 34 33.5 33.5 34 34 34 34 34 33.5 33.5 33.5 34 34.5 34

31 30 31 31.5 31.5 32 32 31 30.5 30.5 29.5 30 30 32 31

11.4 11.5 11.5 11.5 11.6 11.6 11.6 11.8 11.6 11.4 11.6 11.5 11.6 12 11.5

10.8 10.8 10.9 10.8 10.8 10.9 10.9 10.5 10.6 10.8 10.8 10.6 10.7 10.8 10.8

Fig.3: MW load on 100MVA power transformer V/s time in hours

Fig.4: peak and Min load on 100MVA 220/110 kV power transformer

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V. CONCLUSION Planned maintenance schedule keeps the substation equipment in proper working condition to provide maximum reliability, flexibility in operation, continuity of service with reduce down time and reduce the cost of operation and maintenance. Planned maintenance schedule which includes daily, weekly, monthly, half yearly, yearly checks based on the manufacturer’s recommendation which increases working time as well as life of the equipment. Establishing the substation near to the load centers minimize the transmission and distribution losses and it possible to supply quality power to consumer with competitive prices. The good design of a substation should provide a high level of service continuity, provision for further expansion, flexibility of operation and low initial and ultimate costs. VI. REFERENCES [1] FIST volume 4-1B revised November 2005. [2] KPTCL training institute, Study material on “training programme on maintenance”. [3] KPTCL annual report 2010. [4] S. Rao, Text book“Testing commissioning operation & maintenance of electrical equipments” [5] Website: www.kptcl.com. [6] Website: www.kpcl.com. VII. BIOGRAPHY Chavan P.L: was born in Bagalkot, Karnataka state,India,on July 13,1985.He received B.E. degree in Electrical and Electronics engineering from visheshwaraya technological university, Belgaum, in 2009.worked as a faculty in SRVR polytechnic Guledagudd. He is presently persuing master degree in power and energy systems, in Basaveshwar Engineering College, Bagalkot, Karnataka, India. Proff. G. Suchitra: was born in Bagalkot, Karnataka,India on 10 may,1960.She obtained B.E. Electrical degree from Karnataka university dharwad. M.Tech from Bangalore University in 1990 and persuing Ph.d in Basaveshwar Engineering College, Bagalkot. Presently working as faculty in department of Electrical and Electronics at Basaveshwar Engineering college, Bagalkot, Karnataka,India. Dr. Suresh. H. Jangamshetti: (S'88, M'90, SM'97) was born in Bijapur, Karnataka, India on May 28, 1963. He obtained his B.E (Electrical) degree from Karnataka University Dharwad in 1985 and M.Tech. (Power Systems) & Ph.D (Wind Energy Systems) from IIT Kharagpur in 1989 & 2000 respectively. His areas of interest include Wind-Solar Energy Systems, Energy Conservation, Computer Applications to Power System and FACTS He won the "Outstanding IEEE Student Branch Counsellor" award for the year 1996(R10) and 2010 (IEEE Bangalore Section) at Basaveshwar Engineering College, Bagalkot, Karnataka, India. He was Fulbright-Nehru Visiting Lecture Fellow at Michigan Technological University, Houghton MI USA during Fall 2011. He is working as Professor in the department of E&E at Basaveshwar Engineering College, Bagalkot.