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132 kv sub-station, power transmission

here, briefly explained on the equipments of 132 kv sub-station as like 132kv to 33kv 50mva transformer, capbank, relay, busber, lightning arrester, storage battery,circuit breaker, safety procedures, CT PT transformer etc.................

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132 kv sub-station, power transmission

  1. 1. TRAINING REPORT FOR VOCATIONAL TRAINING PROGRAMME AT DEBAGRAM 132/33/11 KV SUB-STATION West Bengal State Electricity Transmission Company Limited Submitted by Diploma-3rd Year, 6th Semester Department of “Electrical and Electronics Engineering” Mirmadan Mohanlal Government Polytecnic Sayan Roy Arup Mondol Prasanta Sarkar Prasanta Baidya Animesh Paul Biswajit Saha Soumik Pramanik Saikat Sarkar
  3. 3. WBSETCL In exercise of power conferred under Section 131(4) of the Electricity Act 2003, the Govt. of West Bengal unbundled West Bengal state Electricity Board into two Companies viz. West Bengal State Electricity Distribution Company Limited (WBSEDCL) and West Bengal State Electricity Transmission Company Limited (WBSETCL). Under the West Bengal Power Sector Reforms Transfer Scheme 2007, activities relating to Transmission and Load Dispatch business of WBSEB were transferred to West Bengal State Electricity Transmission Company Limited (WBSETCL). In effect of the Power Sector Reforms Transfer Scheme 2007, West Bengal State Electricity Transmission Company Limited was incorporated under the provisions of the Companies Act 1956 on 16.02.2007 and other obtained Certificate of Commencement of business on 21st March, 2007. WBSETCL wholly owned by Govt. of West Bengal, is a professionally managed, a multi-sited Power Transmission Company in Eastern India. The Company has developed strong in-house expertise in various facets of power transmission business. As on the end of financial year 2016-17, the Company operates and maintains a transmission network of 12962 CKM of Extra High Voltage Transmission lines along with 117 sub-stations (400 KV- 66 KV) having total transformation capacity of 27752 MVA, spread over the entire stretch of the State of West Bengal. With focus of improving performance, the transmission system was consistently maintained at an availability of 99.91% for the year 2016-2017, at par with international standards. The Company emphasize on evolving and adopting new technologies continuously to effectively meet the challenges of power transmission in the State of West Bengal. On operation and maintenance front, continuous efforts envisage to provide stable and quality power with minimum extent possible transmission loss. To cater the need of improving transmission system and to meet the requirement of increasing demand of both industrial and rural load in the State of West Bengal, various transmission projects are under execution.
  4. 4. i. OVERVIEW OF SUB-STATION Debagram 132/33/11 KV Substation WBSETCL Introduction:- Debagram substation is a 132/33/11 KV substation under West Bengal State Electricity Transmission Company Limited. Debagram 132 KV substation connected with the grid via 132 KV Debagram-Krishnagar, Debagram-Katwa and Debagram-Amtala double circuit transmission lines. The substation feed power to Railway through Debagram-Debagram TSS 132 KV line and Palassey, Akandaberia, Nakashipara, Muragachha and Tehatta 33/11 KV Substations of WBSEDCL through 33 KV feeders. The installed transformer capacity of the substation is 2 X 132/33KV, 50MVA + 3 X 33/11KV, 6.3 MVA + 33/11 KV, 5 MVA. Total 7 nos. 11 KV feeders i.e. Kaligang, Agradweep, Juranpur, Matiary, Panighata, Bagunda and Debagram Feeders receive power from the substation. Apart from that 2 nos. capacitor bank also installed at the substation. Single line diagram of the substation given below.
  7. 7. iii. Switching Operation 1. First close the isolators at both side of the bus coupler breaker. 2. Then close the bypass isolator of the feeder which is to be transferred to transfer bus. 3. Now energized the transfer bus by closing the bus coupler circuit breaker from remote. 4. After bus coupler breaker is closed, now the power from main bus flows to the feeder line through its main 5. Breaker as well as bus coupler breaker via transfer bus. 6. Now if main breaker of the feeder is switched off, total power flow will instantaneously shift to the bus coupler breaker and hence this breaker will serve the purpose of protection for the feeder. 7. At last the operating personnel open the isolators at both sides of the main circuit breaker to make it isolated from rest of the live system. So, it can be concluded that in Main and Transfer Bus System the maintenance of circuit breaker is possible without any interruption of power. Because of this advantage the scheme is very popular for 33 KV and 132 KV system.
  8. 8. iv. EQUIPMENTS & TRANSMISSION a. Lightning arrester(LA) b. Isolators c. Bus bars d. Circuit Breaker(CB) e. Electrical power transformer(TR) f. Instrument Transformers(CT & PT) g. Control and Relay panel h. Capacitor bank. i. Conductor j. Reactor k. Under Ground cable l. Insulator m. Earthling System n. Transmission Tower o. Battery System p. Communication system(PLCC)
  9. 9. a. Lightning Arrestor(LA) The device which is used for the protection of the equipment at the substations against travelling waves, such type of device is called lightning arrester or surge diverter. In other words, lightning arrester diverts the abnormal high voltage to the ground without affecting the continuity of supply. The arrester which uses zinc oxide semiconductor as a resistor material, such type of arrester is known as a metal oxide surge arrester or ZnO Diverter. In Debagram Substation lightning arrester is using to protect transformer and others equipments in the substation b.Isolator Electrical isolators separate a part of the system from rest for safe maintenance works. So definition of isolator can be rewritten as Isolator is a manually operated mechanical switch which separates a part of the electrical power. Isolators are used to open a circuit under no load. There are many type of isolator used in substation. Like that, ★ Line Side isolator ★ Main bus side isolator ★ Transfer bus isolator ★ Earthing isolator
  10. 10. Main Bus isolator: A bus isolator is an off load switch that connects the line breaker and the bus. It sits between circuit breaker and bus. Line Side isolator: line isolator is an off load switch that connects the line breaker and the line. It sits between circuit breaker and current transformer. Transfer Side isolator: Transfer bus side isolator which operates when power feed through transfer bus. Earthling isolator: Main function of earth switch is to ground the isolated bus/conductor. It is interlinked with isolator, when isolator opens the circuit, earth switch is closed & when isolator closes the circuit, earth switch is opened. In Debagram Substation, using rotating type isolator, it may be operated manually or by using remote control operator. c. Busbars Busbar Is a very important part of a substation which connects incoming circuit and outgoing circuit and transformer bays etc. In Debagram substation there is two types of 132KV busbar ----1. 132 KV Main Bus 2. 132KV Transfer Bus. Other bus bar is,33 KV mian bus , 11KV main bus Size description of hollow Aluminum tube/conductor at Bay side.Busbar of 132KV , 33KV , 11 KV are this type of conductor.
  11. 11. d. Circuit Breaker Electrical circuit breaker , which can be operated automatically or manually for protecting and controlling of electrical power system. In the modern power system the design of the circuit breaker has changed depending upon the huge currents and to prevent from arc while Operating. There is 2 Types of Circuit Breakers In Debagram Substation ● SF6 Circuit Breaker ●Vaccume Circuit Breaker Sulphur hexafluoride gas is known as an SF6 gas which is used as insulating medium for the circuit breaker. high tendency of absorbing free electron. The negative ion is formed when a free electron collides with the SF6 gas molecule; it is absorbed by that gas molecule. Electrical Power Transformer In Debogram Substation,there are two 50 MVA,132/33 KV, three 6.5 MVA,33/11 KV and one 5 MVA ,33/11 KV, for voltage step down and two 100 KVA 33/0.4 KV earthling transformer and 100KVA 33/0.4 KV station servise transformer.
  12. 12. Transformer Accessory: Bushing ( HV side & LV side) ,Horn gap arrester , Main tank , Transformeroil , Winding (primary & secondary), Core , Tap changer(OLTC) , Conservator tank , Breather , Explosionvent/pressure release device(PRV/PRD) , Marshalling box, Ratting Plate , Oil level indicator(MOG) , Temperature indicator(WT & OT) , Radiator , Cooling fan , Oil pump Transformer Protection: Buchholz Relay, Over Current protection, Differential protection, restricted Earth fault protection,Backup Earth fault protection, Winding temperature & Oil temperature protection Cooling System ■ Oil NaturalAir Natural(ONAN) ■ Oil NaturalAir Forced (ONAF) ■ Oil Forced Air Forced (OFAF) ■ Oil Forced Water Forced (OFWF) f. Instrument Transformer (CT & PT) Specially designed transformer which is used to to measure high alternating Current and Voltage , is called instrument transformers Current Transformers (CT) The current transformer is used for measure alternating current & protection in power system. PotentialTransformers (PT) Potential transformer is a voltage step-down transformer which reduces the voltage of a suitable value (i.e high voltage circuit to a lower level). Main purpose of potential transformer is 1. Voltage measurement , 2. Protection.
  13. 13. g. CONTROL AND RELAY PANEL A control & relay panel is designed to provide to control the associated line or transformer through outdoor switchgear of substations. The control & Relay panels are complete in themselves with all main and auxiliary relays, annunciation relay, switches, wiring, labels, terminal blocks, illumination, cable etc. These panels are used for the control & monitoring of electrical equipments such as transformers, busbar, and circuit breakers.Control panel for Outdoor SF6 Circuit Breaker, Master Trip Relay, Trip circuit Supervision Relay, Indications & meters etc. A relay is a switching device which is used to switching high voltage line using low voltage power supply. Most important use of relay is for protection from fault.and manual on/off of supply Different Types of Relays are: 1. Distance Protection Relay Impedance Relay is protection relay which functions depending upon the distance of fault in the line. More specifically, the relay operates depending upon the impedance between the point of fault and the point where relay is installed. These relays are known as Distance Relay or Impedance Relay. 2. Overcurrent relay
  14. 14. This type of relay works when current in the circuit exceeds the predetermined value. In an over current relay or o/c relay the actuating quantity is only current. There is only one current operated element in the relay, no voltage coil etc. are required to construct this protective relay. 3. Differential Protection Relay A differential relay is used to identify all kind fault in a transformer. Voltage Differential Relay Biased or Percentage Differential Relay Voltage Balance Differential Relay 4. Buchholz Relay : Buchholz relay is used for protection of all kind of internal fault . It is used on all oil immersed transformers. Such relay can only be fitted to the transformers equipped with the conservator tank as it is installed in between the conservator tank and the main tank. h. CAPACITOR BANK Static capacitor is used in parallel to improve lagging power factor of transmission line. A Capacitor Bank is a group of several capacitors of the same rating that are connected in series or parallel configaration with each other to increase active power or voltage. When the inductive load of the line is increase then the reactive component
  15. 15. increase so the KVAR increase of the line by adding capacitor in parallel the inductive load reduces. Also increase the power factor and receiving end voltage. i. Conductor Conductors which carry electric power from the sending end sub-station to the receiving end station. Most of the conductor in Debagram Substation are ACSR (Aluminium conductor Steel reinforced) In 132 kv High volt side moose conductor are used in main buss and panther conductor are used in transfer buss. Jumper Wire : Jumper used to connect to terminal of busbar or lines. Dropper : Dropper is the verticle conductor connected with bushing of transformer. j. Reactors Capacitor (Damping) Reactors are designed to be installed in series with a shunt- connected capacitor bank to limit inrush currents in the capacitor bank due to switching operations, to limit outrush currents due to close-in faults and to control the resonant frequency of the system due to the addition of the capacitor banks. k. Underground Cable: Underground cable essentially constitutes of one or more conductors covered with suitable insulation and surrounded by a protective cover. UG cable is divided by two part 1.Power cable and 2.Control cable
  16. 16. underground Cable are used for connection from AC distribution box & DC distribution box as a power cable control & relay panel to different equipment such as CB, CT, PT, LA, transformers accessory as a control cable. l. Insulator: The overhead line conductor should be supported on the towers in such a way that current from the conductors do not flow the earth to the support. So the insulators provide necessary insulations between the line conductors and support. Types of insulator used as overhead line : 1. Pin Insulator 2. Suspension Insulator 3. Strain Insulator 4. Shackle type insulator Pin Insulator: The pin insulator is used in power distribution for the voltage up to 33KV. It is placed on the cross arm of the supporting tower. The pin insulator has grooves on the upper end for keeping the conductor. Suspension Insulator: In higher voltage, beyond 33KV, it becomes uneconomical to use pin insulator because size, weight of the insulator become more.Each insulator of a suspension string is called disc insulator because of their disc like shape.Each disk is permitted for 11 KV line to earth voltage.
  17. 17. Strain Insulator: When suspension string is used to sustain extraordinary tensile load of conductor it is referred as string insulator. When there is a dead end or there is a sharp corner in transmission line, the line has to sustain a great tensile load of conductor or strain. A strain insulator must have considerable mechanical strength as well as the necessary electrical insulating properties. m. Earthing System Earthing or grounding is required to immediate discharge of electricity directly to the earth or ground during lightning and switching surge conditions. The benefits of earthing or groundingin an electrical system Safety of operational and maintenance stuff . Discharge of electrical charge to ground . Grounding of overhead shield wire. Electromagnetic interference Common Types of Earthing Used at sub-station : Earthing mat: a number of rods when joined together through copper conductors constitute an earthing mat. It reduces overall grounding resistance .such a mess of conductor laid near the ground surface ,in limiting the potential gradient . in hard soil or in soils having low conductivity , driving of rods quite deep may prove expensive. Earth pit: earth pit are the preferred method of earthing especially for electrical network. Electricity always flows the path of least resistence and to diavert the maximum current away from a circuit, earthing pits are designed to reduce ground resistance.
  18. 18. n. TransmissionTower The main supporting unit of overhead transmission line is transmission tower. Transmission towers have to carry the heavy transmission conductor at a sufficient safe height from ground. Based on numbers of circuits carried by a transmission tower, it can be classisfied as- Single circuit tower Double circuit tower Multi circuit tower. o. Battery System DC supply is required for closing and tripping of circuit breaker control board indication control and instrumentation communication and annunciation system etc. Battery are also used to provide illumination in certain and sensitivity area for otherwise work with stand still.
  19. 19. Battery Charger:- The battery charger converts AC to DC voltage and also charged the battery by float (trickle charging) and boost (quick charging) charging method automatically. p. Communication System(PLCC) The PLCC is used to communicate with sub-station to substation for send & receive information, data etc. But Debagram substation this method is not using. Now they are using optical fibre cable for communication purpose.
  20. 20. V. OPERATING INSTUCTION AND MAINTENANCE Operating Instruction: An Operating Agreement (OA) is an agreement between two Operating Authorities. It is used to confirm that an electrical apparatus operational state will be held in an agreed state until the OA is cancelled. An OA is used when one party needs to work on an item of plant or electrical apparatus which requires isolation and/or earthing from an adjacent Operating Authority. The Operating Agreement recipient shall verify the isolations and earthing points stated on the Agreement, and may apply additional locks and tags. An OA is not a work permit. It does not authorise work to be undertaken. A work permit must be issued to allow work to take place. The conditions stated on the work permit must reference the OA. An OA is issued by a switching operator. For standard outages, the outage requestor will write the associated switching program, unless otherwise agreed. For the commissioning of other Operating Authority apparatus, Horizon Power will usually write the switching program. The issue and relinquishment of Operating Agreement must be recorded as steps in the switching program. Maintenance: Monitoring systems provides all the technical information required to maintain utmost availability and at the same time maximize performance, including loading and lifetime benefits. This advanced monitoring solution surveys every link in the energy supply chain. Accurate monitoring of all primary components of a substation makes possible optimized loading and performance, and it helps increase the lifetime of the line. Electrical Preventive Maintenance Electrical preventative maintenance isn’t just an important way to avoid preventable electrical repairs and maintain your system. It’s also a great way to save money! Using electricity produces heat. Over time, that heat causes expanding and contracting of an electrical system.
  21. 21. 1) Visual inspection of electrical equipment inside substation 2) Thermo-vision scan of the different electrical equipment and transmission lines before and after preventive maintenance Electrical Breakdown Maintenance: Breakdown maintenance is maintenance performed on equipment that has broken down and is unusable. It is based on a breakdown maintenance trigger. It may be either planned or unplanned. VI. CONDITION MONITORING AND DIAGNOSTICS TESTING Condition Monitoring: To ensure the power system operates safely and reliably, it is essential to monitor and evaluate the health condition of power equipment on-line or off-line. This study reviews the research status in condition monitoring and diagnosis of power equipment, including transformer, gas insulated switchgear, cable, external insulation, generator, and power capacitor in recent years. Although much progress has been made in technologies of condition monitoring and fault diagnosis such as test accuracy, fast and accurate fault localisation and recognition of fault types, there are still many deficiencies which needs further research work, including the reliability of signal collection from sensors, the accuracy of data treatment and analysis, antiinterference performance of test equipment, appropriate models used for condition evaluation. The prospective of condition monitoring and diagnosis technologies of power equipment are also presented in this study. It is proposed that the application of big data, internet of things and cloud computing should be expected and given special attention in the near future.
  22. 22. Diagonistic Testing: Circuit braker:- 1. SF6 GAS Analysis 2. Circuit breaker Timing 3. Circuit breaker Contact Resistance Measurement 4. Insulation resistance Measurement LightningArrester:- 1. Leakage Current Measurement 2. Insulation resistance Valve Transformer:- 1. Dissipation Factor: 2. Insulation resistance : 3. P.I. 4. Tr. Oil Test Transformer oil Test: 1. BDV 2. ACIDITY 3. D.F. (Tan Delta) 4. Moisture Content 5. D.G.A. D.C System:- 1. Earth Fault Locator
  23. 23. vii. System Study Techniques System study is a major part of monitoring of the system for every substation. Generally shift engineers takes voltage, current, megawatt, MVAR, temperature (OTI & WTI) reading of the each transformer and feeder, charging current and voltage of battery bank etc. in every hours. The condition of silica gel, oil leakage, Sf6 gas pressure etc checked in every shift. The system study of the different equipment of the substation is very much required to take preventive action in case of any abnormality of the system. viii. Trouble Shooting Electrical transmission and distribution equipment; Experience in operating, maintaining and troubleshooting of Switchyard and substation equipment The term “troubleshooting” mainly attributes to sort out different problems such as non-closure of “closing coil” or “tripping coil” of circuit breaker, non- functioning of remote operating isolators, relays etc. The interconnectivity of the particular circuit including the various interlocking limit switches and relay contacts. Check for simultaneous open & close of slow open & close of main contacts, of circuit breakers and isolators.
  24. 24. ix. Electrical Safety Procedures, Accident Prevention What is safety: "Safety" denotes "Existence" of safe situation", meaning "not dangerous" or "not risky". To achieve Safety in a job, or at work site, or in the process of work, two attempts are made- a. To shield a danger b. To guard people against the risk of a danger. Electrical Safety is about attempts an efforts to ensure preventing physical loss or damage of people caused by Electrical shock i.e. passage of electric current through one's body. Safety Precautions in substation: 1. Get the substation inspected by the local fire service officer if required. 2. In case of fire, call fire station & give them guidance. 3. Provide Co2/DCP/Foam as extinguishing medium at proper place. 4. Earthing of Transformer, breaker etc should be done effectively. 5. Provide high temperature trip to Transformer. 6. Attend loose contact or red hotspot in time detected through thermo- vission camera. 7. Avoid joint in cables. 8. Avoid loose fuse links.
  25. 25. 9. Use Safety equipment (PPE) like safety rope, safety belt, insulating rubber mat, discharge cum earthing rod, safety shoe, hand gloves, high voltage detector, safety ladder, helmet etc. of proper rating at the time of work. 10. Provide adequate water supplies for firefighting. 11. Ensure availability of First aid box with requisite drugs & other materials. In any Electrical substation safety is a very important part. We already know alphabetic letter ABC i.e. " always be careful" So If we do any job related to Electrical mechanical or other work It should be "Always be careful" & maintain proper safety because safety 1st Safety must. X. TRANSMISSION SUB-STATION & LINE MAINTENANCE Substation maintenance: Substation maintenance plays a very important role to ensure trouble free operation of any substation. Maintenance of different equipment done periodically on different interval as per standard maintenance prcedure of WBSETCL: 1. Maintenance of Battery banks carried out monthly by taking specific gravity and voltage of each lead acid type cells and cleaning of the battery etc. 2. Thermo-vision scanning of different equipment of the substation done periodically for detection of Hot spots in the connectors. 3. Winter and pre-puja maintenance of the Bus, Transformer, Circuit Breakers, Isolators, Current transformers, Lightening Arrestors etc. of all the Bays carried out by tightening of connectors, cleaning of insulators, checking of I.R. value of the equipment etc. 4. The condition monitoring of the equipment also carried out for evaluation of health of the particular equipment. In case of any abnormality noticed during the tests, corrective action taken to avoid failure of that equipment which may cause breakdown and even accident.
  26. 26. 5. Checking the operation of relays and other protective equipments to ensure safety of the system. Line maintenance: Line maintenance plays a very important role in power transmitting system. For uninterrupted power supply it is essential to maintain the transmission lines remains healthy both during normal and hazardous condition. For preventive and predictive maintenance of transmission lines following methods are applied: 1. Regular line patrolling of the transmission line towers and line components carried out for detection of loss / damage of any tower member, damage of conductor, approaching of any earth object like trees near the line, dislocation of Vibration damper, damage of disc insulator string, sagging of line etc. 2. Thermo-graphic scanning of jumpers for detecting Hot spots. 3. Punctured insulator detection by electric field measurement / voltage measurement method. 4. Tower footing earth resistance measurement.