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Summer Training Report on 220 Kv Substation

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    SUMMER TRAINING REPORT ON STUDY OF 220 KV SUB-STATION (GAZIPUR) NEW DELH ACKNOWLEDGEMENT A number of people have contributed to the preparation of the manuscript of this report . I gratefully acknowledge the contribution of each of them. Firstly , I would like to express ,my thanks to my institution ,SHARDA UNIVERSITY (school of engineering and technology), Greater Noida, for giving me opportunity to have my Internship in Delhi Transco Limited. In particular ,Mr.

    Satpal Singh , the AM of Delhi Transco Limited , Gazipur , New Delhi, who catechized in us its important working and functions. Last but not the least I thank my parents and the Almighty whose blessings are always there with me. MD. ZEESHAN FAIZI phone no-+91-9650865622 CONTENTS Contents Abstract History of power sector in Delhi Formation of Delhi Electricity Board About DT Financial Turn around Future Plan Definition Introduction o About the substation Construction – Site Selection & Layout Equipment in a 220KV Substation Bus-bar o Insulators o Isolating Switches o Circuit breaker o Protective relay o Instrument Transformer § Current Transformer § Voltage Transformer o Metering and Indicating Instrument o Miscellaneous equipment o Transformer o Lightening arrestors o Line isolator o Wave trap Single line diagram (SLD) Brief descriptions of the instruments in the line diagram Storage of equipments for the substation Control and relay part DC supply system Conclusion ABSTRACT The report gives an overview of 220kv power substation .

    It includes electricity transmission and distribution processes at DTL , Gazipur substation . Its substation, an assembly of apparatus which is installed to control transmission and distribution of electric power , its two main divisions outdoor and indoor substation . Different equipments used in substations, Busbar, surge arrestor, Isolator, Earth switches , Current Transformers etc. Transformer which is being used here is core and shell type transformer for stepping up and down purposes.

    Different Instruments transformers , voltage, Current and CV transformers are also being used. finally the CVT rating which gives a total output overview. History Of Power Sector in Delhi Introduction| Electricity plays a vital role in our day-to-day life. It powers our houses, industries, hospitals and in fact our entire economy. Historically speaking the modern electricity industry utility system was first introduced to the world on the opening of Thomas Edison’s Pearl Street Electricity Generating Station on September 4th , 1882 at New York (United States of America).

    Insofar as Delhi is concerned, the position is that as per available records, the first diesel Power Station was established in Delhi in the year 1905 when a private English Company by name M/s. John Fleming was given permission to generate electricity under the provisions of the Indian Electricity Act 1903. The above mentioned Company was given the responsibility both of generation and distribution of power in a limited manner. That Company after obtaining license under the provisions of Electricity Act 1903 had set up a small 2 MW Diesel set at Lahori Gate in Old Delhi.

    Later on, this very Company was converted as Delhi Electricity Supply and Traction Company. In the Year 1911, the power generation was augmented by Steam Generation Station. In the year 1932, the management of Central Power House was handed over to New Delhi Municipal Committee (NDMC). In the field of power generation and distribution, a major break through was achieved in 1939 when Delhi Central Electricity Power. A uthority (DCEPA) was established.

    This Company was responsible for the supply of power to the areas covered by Local Bodies, namely, the Municipal Committees of Delhi, West Delhi and South Delhi, the Notified Area Committees of Red fort, Civil Lines, Mehrauli, Najaf Garh, amd the District Board of Delhi. The supply of electricity to the Municipal Committees of Delhi-Shahdara and the Notified Area of Narela was done by different private agencies. In 1947 DCEPA took over a Private Limited Company by name Delhi electric Supply traction Company Limited. |

    Promulgation of Electricity (Supply)Act 1948| In the year 1948, electricity (Supply) Act 1948 came into force, which inter-alia provided for the constitution of an electricity Board in the States that was to function as a vertically integrated electricity utility in the entire State, undertaking all the functions of activities related to electricity, which included electricity generation, transmission, distribution, supply, planning coordination and also was to act as regulatory authority for carrying out other functions incidental and ancillary thereto.

    In other words, the Electricity (Supply) Act 1948 was entitled to become a monopolistic undertaking in the field of electricity control by an instrument of the state and not by private sector. The principal objective behind the above policy decision of the Government of India in providing for the constitution of State electricity to all, particularly in semi-urban and rural areas because till then the availability of electricity was confined to urban areas and was mainly served by private electricity distribution licenses issued under the Indian electricity Act 1910. Formation of Delhi State Electricity Board| In pursuance of the provisions of the Electricity (Supply) Act, 1948, in Delhi, in the year 1951 the Delhi State Electricity Board (DSEB) came into existence and the responsibility of generation and distribution of electricity was taken over by DSEB from DCEPA. The entire staff of DCEPA and other agencies was absorbed by DSEB under the existing terms conditions of service. | Notification of Industrial Policy Resolution|

    Growth in demand of electricity Thus, starting the humble origin, i. e. , Private Limited Company having a few employees with primitive generation process, the generation, transmission, and distribution of power to the citizens of Delhi has now come in the hands of above mentioned six Companies with an employee strength which has grown over the years from a meager figure of few hundred to about 20,000. Prior to 1951, the demand of power in Delhi was about 27 MW which now has grown to about 4,000 MW.

    Availability of reliable and cheap power is absolutely essential for economic development of any developing society and consumption of electricity is an important indicator of the stage of development of agriculture, industry and commerce. With the growth of population, industries, importance of Delhi being the national Capital and with the advancement of technology, life style and increased use of new electrical electronic gadgets, the demand of power has gone up enormously.

    Present Scenario The role of Delhi Transco Limited is confined to arrange and provide transmission network of 400 KV and 220 KV source from Northern Grig. The present infrastructure for this purpose under 400 KV system is 4,725 MVA (2520 MVA with DTL and 2205 with Power Grid Corporation). As against this, 220 KV sub Stations have the capacity of 6,300 MVA is available for Delhi. Future Plans In the 11th Plan ending 2011-12 the transmission capacity is proposed to be augmented to meet the future requirements.

    Under 400 KV system, it is proposed to establish new Sub Stations at Mundka, South-East Delhi near Mandi village and East Loni Road with a capacity of 630 MVA each by DTL and also increase the capacity of existing sub-Station at Maharani Bagh by 630 MVA b Power Grid Corporation of India Limited. Similarly, under 220 KV system, augmentation and new addition in capacity to the tune of 1660 MVA under the existing Sub Stations is proposed. Further, new Sub Station at DSIDC Bawana-II (320MVA), Chandrawal (200 MVA), Jhatikara More (320 MVA),.

    Ridge Valley (320 MVA), Rohini-II (480 MVA), Sultanpuri (320 MVA), Electric lane (200 MVA), Trauma Centre (200 MVA), Wazirpur Industrial Area (320 MVA) and IGI Airport (320 MVA ) are proposed to be established. Thus, the capacity of 2520 MVA and 5940 MVA will be added in the 400 KV system and 220 kv substation respectively. To sum up, by 2011-12 transformation capacity of 8460 MVA will be added and a total capacity of 19485 MVA will be available to Delhi. | About DTL|

    Delhi Transco Limited, a successor company of erstwhile Delhi Vidyut board, came into existence on 1st July 2002, as a State Transmission Utility of the National Capital. After unbundling of DVB the distribution sector has been handed over to private companies while the generation and transmission are still with the government. Over the years, DTL has evolved as a most dynamic performer, keeping pace with the manifold challenges that confront the ever ncreasing demand-supply power situation and achieving functional superiority on all fronts.

    Being the capital of India and the hub of commercial activities in the Northern Region, coupled with the prosperity of population, the load requirement of Delhi has been growing at a much faster pace. Added to that, being the focus of socio-economic and political life of India, Delhi is assuming increasing eminence among the great cities of the world. Plus the vgision-2021, aiming to make Delhi global Metro politic and world class city demand greater infrastructure to enrich many services of infrastructure development. DTL has been responsibly playing its role in establishing.

    Upgrading, operating and maintaining the EHV (Extra High Voltage) network. DTL has also been assigned the responsibility of running the State load Dispatch Centre (SLDC) which is an apex body to ensure integrated operations of power system in Delhi. Delhi Transco is also committed to promote energy conservation not only in its own establishments but also in the entire Delhi. The company has done a lot to educate and sensitize the general public about the need of energy conservation. Transmission loss level has been reduced from 3. 84 per cent in 200-203 to 1. 8 per cent in 2009-10, which is one of the lowest transmission loss level in the country. To ensure adequate and efficient power supply. DTL has been continuously upgrading its biggest achievement has been its ability to handle the highest ever peak demand of 4720 MW in July 2010. The total availability of its transmission system stood 98. 78%. The modern technologies are being implemented in DTL by way of constructing GIS sub stations and laying XLPE 220 KV cable by employing cable link techniques and would be the largest network of its kind in India. | Care of Environment|

    DTL operate its obligations in a clean, green pollution free environment and has been providing more green coverage to the National Capital. It has contributed a lot in spreading awareness among the masses to use eco-friendly electrical appliances. The Energy Conservation Building Code also thrust upon to maximize the use of natural resources and minimize the use of electricity. Transparency and AccountabilityDelhi Transco Ltd. is committed to provide information to the citizens with a view to fulfill it obligations under Delhi Right to information Act 2001 and Right to Information Act 2005.

    Anyone desirous of seeking information related to the functions of the company can ask for information. Apart from this a transparent mechanism has been put in place for award of the works and release of payments to the contractors and other stake holders. | IT Initiatives| To enhance efficiency and productivity, DTL has initiated several IT based projects. For constant access to real-time data of the entire network, the company has implemented Supervisory Control and Data Acquisition (SCADA) systems. DTL has also carried out system studies, adopting state of the art software.

    Enterprise Resources Planning Software has been implanted which offers an integrated software facilitates best practice by creating more efficient system and concentrating its efforts towards maximizing profits. | Financial turn around| DTL has achieved a commendable financial turnaround after a four-year financial engineering process. It has posted profits in each of the past 4 years. In 2009-10 DTL profits, after tax stood at Rs. 77. 28 Crore, an impressive 21. 72% increase over the Rs. 63. 49 Crore, registered in the Government and Rs. 54 lacs DPCL for 2009-10. | .

    Future Plans| In the 11th Plan ending 2011-12 the transmission capacity is proposed to be augmented to meet the future requirements. Under 400 KV system, it is proposed to establish new Sub Stations at Mundka, South-East Delhi near Mandi village and East Loni Road with a capacity of 630 MVA each by DTL and also increase the capacity of existing sub-Station at Maharani Bagh by 630 MVA b Power Grid Corporation of India Limited. Similarly, under 220 KV system, augmentation and new addition in capacity to the tune of 1660 MVA under the existing Sub Stations is proposed.

    Further, new Sub Station at DSIDC Bawana-II (320MVA), Chandrawal (200 MVA), Jhatikara More (320 MVA),. Ridge Valley (320 MVA), Rohini-II (480 MVA), Sultanpuri (320 MVA), Electric lane (200 MVA), Trauma Centre (200 MVA), Wazirpur Industrial Area (320 MVA) and IGI Airport (320 MVA ) are proposed to be established. Thus, the capacity of 2520 MVA and 5940 MVA will be added in the 400 KV system and 220 KV system, respectively. | “The assembly of apparatus used to change some characteristics (e. g. Voltage ac to dc freq. p. f. etc) of electric supply is called sub-station”

    Introduction The present day electrical power system is a. c. i. e. electric power is generated, transmitted and distributed in the form of Alternating current. The electric power is produce at the power station, which are located at favorable places, generally quite away from the consumers. It is delivered to the consumer through a large network of transmission and distribution. At many place in the line of power system, it may be desirable and necessary to change some characteristic (e. g. Voltage, ac to dc, frequency p. f. etc. of electric supply. This is accomplished by suitable apparatus called sub-station for example, generation voltage (11KV or 6. 6KV) at the power station is stepped up to high voltage (Say 220KV to 132KV) for transmission of electric power. Similarly near the consumer’s localities, the voltage may have to be stepped down to utilization level. This job is again accomplished by suitable apparatus called sub-station. About the substation The substation in Gazipur (Delhi Transco Ltd), New Delhi is one of the largest power grids in Delhi.

    The most important of any substation is the grounding (Earthing System) of the instruments, transformers etc. used in the substation for the safety of the operation personnel as well as for proper system operation and performance of the protective devices. An earthes system comprising of an earthing mat buried at a suitable depth below ground and supplemented with ground rods at suitable points is provided in the substations. These ground the extra high voltage to the ground. As it is dangerous to us to go near the instrument without proper earth.

    If the instruments are not ground properly they may give a huge shock to anyone who would stay near it and also it is dangerous for the costly instrument as they may get damaged by this high voltage. Site Selection & Layout 220KV Substation :- 220KV Sub-Station forms an important link between Transmission network and Distribution network. It has a vital influence of reliability of service. Apart from ensuring efficient transmission and Distribution of power, the sub-station configuration should be such that it enables easy maintenance of equipment and minimum interruptions in power supply.

    Sub-Station is constructed as near as possible to the load center. The voltage level of power transmission is decided on the quantum of power to be transmitted to the load center. Selection of site Main points to be considered while selecting the site for Grid Sub-Station are as follows: i) The site chosen should be as near to the load center as possible. ii) It should be easily approachable by road or rail for transportation of equipments. iii) Land should be fairly leveled to minimize development cost. iv) Source of water should be as near to the site as possible.

    This is because water is required for various construction activities (especially civil works), earthing and for drinking purposes etc. v) The sub-station site should be as near to the town / city but should be clear of public places, aerodromes, and Military / police installations. vi) The land should be have sufficient ground area to accommodate substation equipments, buildings, staff quarters, space for storage of material, such as store yards and store sheds etc. with roads and space for future expansion. ii) Set back distances from various roads such as National Highways, State Highways should be observed as per the regulations in force. viii) While selecting the land for the Substation preference to be given to the Govt. land over private land. ix) The land should not have water logging problem. x) Far away from obstructions, to permit easy and safe approach termination of high voltage overhead transmission lines. Equipment in a 220KV Sub-Station :- The equipment required for a transformer Sub-Station depends upon the type of Sub-Station, Service requirement and the degree of protection desired. 20KV EHV Sub-Station has the following major equipments. Bus-bar When a no. of lines operating at the same voltage have to be directly connected electrically, bus-bar are used, it is made up of copper or aluminum bars (generally of rectangular X-Section) and operate at constant voltage. The bus is a line in which the incoming feeders come into and get into the instruments for further step up or step down. The first bus is used for putting the incoming feeders in LA single line. There may be double line in the bus so that if any fault occurs in the one the other can still have the current and the supply will not stop.

    The two lines in the bus are separated by a little distance by a Conductor having a connector between them. This is so that one can work at a time and the other works only if the first is having any fault. Insulators The insulator serves two purpose. They support the conductor (or bus bar) and confine the current to the conductor. The most commonly used material for the manufactures of insulators is porcelain. There are several type of insulator (i. e. pine type, suspension type etc. ) and there used in Sub-Station will depend upon the service requirement.

    Isolating Switches In Sub-Station, it is often desired to disconnect a part of the system for general maintenance and repairs. This is accomplished by an isolating switch or isolator. An isolator is essentially a kniff Switch and is design to often open a circuit under no load, in other words, isolator Switches are operate only when the line is which they are connected carry no load. For example, consider that the isolator are connected on both side of a cut breaker, if the isolators are to be opened, the C. B. must be opened first. Circuit breaker

    A circuit breaker is an equipment, which can open or close a circuit under normal as well as fault condition. These circuit breaker breaks for a fault which can damage other instrument in the station. It is so designed that it can be operated manually (or by remote control) under normal conditions and automatically under fault condition. There are mainly two types of circuit breakers used for any substations. They are (a) SF6 circuit breakers; (b) spring circuit breakers. For the latter operation a relay wt. is used with a C. B. generally bulk oil C. B. re used for voltage upto 66 KV while for high voltage low oil & SF6 C. B. are used. For still higher voltage, air blast vacuum or SF6 cut breaker are used. The use of SF6 circuit breaker is mainly in the substations which are having high input kv input, say above 220kv and more. The gas is put inside the circuit breaker by force ie under high pressure. When if the gas gets decreases there is a motor connected to the circuit breaker. The motor starts operating if the gas went lower than 20. 8 bar. There is a meter connected to the breaker so that it can be manually seen if the gas goes low.

    The circuit breaker uses the SF6 gas to reduce the torque produce in it due to any fault in the line. The circuit breaker has a direct link with the instruments in the station, when any fault occur alarm bell rings. Protective relay A protective relay is a device that detects the fault and initiates the operation of the C. B. to isolate the defective element from the rest of the system”. The relay detects the abnormal condition in the electrical circuit by constantly measuring the electrical quantities, which are different under normal and fault condition.

    The electrical quantities which may change under fault condition are voltage, current, frequency and phase angle. Having detect the fault, the relay operate to close the trip circuit of C. B. TYPES OF PROTECTIVE RELAY Overcurrent relay An “overcurrent relay” is a type of protective relay which operates when the load current exceeds a preset value. The ANSI device number is 50 for an instantaneous overcurrent (IOC), 51 for a time over current (TOC). In a typical application the overcurrent relay is connected to a current transformer and calibrated to operate at or above a specific current level.

    When the relay operates, one or more contacts will operate and energize to trip (open) a circuit breaker. Induction disc overcurrent relay These electromagnetic relays use the induction principle discovered by Galileo Ferraris in the late 19th century. The magnetic system in induction disc overcurrent relays is designed to detect overcurrents in a power system and operate with a pre-determined time delay when certain overcurrent limits have been reached. In order to operate, the magnetic system in the relays produces torque that acts on a metal disc to make contact, according to the following basic current/torque equation:

    Where – is a constant  and  are the two fluxes  is the phase angle between the fluxes The relay’s primary winding is supplied from the power systems current transformer via a plug bridge, which is called the plug setting multiplier (psm). Usually seven equally spaced tappings or operating bands determine the relays sensitivity. The primary winding is located on the upper electromagnet. The secondary winding has connections on the upper electromagnet that are energised from the primary winding and connected to the lower electromagnet.

    Once the upper and lower electromagnets are energised they produce eddy currents that are induced onto the metal disc and flow through the flux paths. This relationship of eddy currents and fluxes creates torque proportional to the input current of the primary winding, due to the two flux paths been out of phase by 90°. In an overcurrent condition, a value of current will be reached that overcomes the control spring pressure on the spindle and the braking magnet, causing the metal disc to rotate towards the fixed contact.

    This initial movement of the disc is also held off to a critical positive value of current by small slots that are often cut into the side of the disc. The time taken for rotation to make the contacts is not only dependent on current but also the spindle backstop position, known as the time multiplier ™. The time multiplier is divided into 10 linear divisions of the full rotation time. Providing the relay is free from dirt, the metal disc and the spindle with its contact will reach the fixed contact, thus sending a signal to trip and isolate the circuit, within its designed time and current specifications.

    Drop off current of the relay is much lower than its operating value, and once reached the relay will be reset in a reverse motion by the pressure of the control spring governed by the braking magnet. Distance relay The most common form of protection on high voltage transmission systems is distance relay protection. Power lines have set impedance per kilometre and using this value and comparing voltage and current the distance to a fault can be determined. The ANSI standard device number for a distance relay is 21. Fig:distance relay Current differential protection

    Another common form of protection for apparatus such as transformers, generators, busses and power lines is current differential. This type of protection works on the basic theory of Kirchhoff’s current law which states that the sum of the currents entering and exiting a node will equal zero. It is important to note the direction of the currents as well as the magnitude, as they are vectors. It requires a set of current transformers (smaller transformers that transform currents down to a level which can be measured) at each end of the power line, or each side of the transformer.

    The current protection relay then compares the currents and calculates the difference between the two. As an example, a power line from one substation to another will have a current differential relay at both substations which communicate with each other. In a healthy condition, the relay at substation A may read 500 amps (power exporting) and substation B will read 500 amps (power importing). If a path to earth or ground develops there will be a surge of current. As supply grids are generally well interconnected the fault in the previous example will be fed from both ends of the power line.

    The relay at substation A will see a massive increase in current and will continue to export. Substation B will also see a massive increase in current, however it will now start to export as well. In turn the protection relay will see the currents traveling in opposite directions (180 degrees phase shift) and instead of cancelling each other out to give a summation of zero it will see a large value of current. The relays will trip the associated circuit breakers. This type of protection is called unit protection, as it only protects what is between the current transformers.

    It is important to note that generally the higher the currents in the lines the larger the differential current required for the relay to see it as a fault. This is basically done due to small mismatches in current transformers. Small errors will increase as current increases to the point where the error could cause a false trip if the current differential relay only had an upper limit instead of the rising differential characteristic. It is also important to note that CTs have a point where the core saturates and the current in the CT is no longer proportional to the current in the line.

    A CT can become inaccurate or even saturate because of a fault outside of its protected zone (through fault) where the CTs see a large magnitude but still in the same direction. Instrument Transformer The line in Sub-Station operate at high voltage and carry current of thousands of amperes. The measuring instrument and protective devices are designed for low voltage (generally 110V) and current (about 5A). Therefore, they will not work satisfactory if mounted directly on the power lines. This difficulty is overcome by installing Instrument transformer, on the power lines. There are two types o f instrument transformer. ) Current Transformer A current transformer is essentially a step-down transformer which steps-down the current in a known ratio, the primary of this transformer consist of one or more turn of thick wire connected in series with the line, the secondary consist of thick wire connected in series with line having large number of turn of fine wire and provides for measuring instrument, and relay a current which is a constant faction of the current in the line. Current transformers are basically used to take the readings of the currents entering the substation. This transformer steps down the current from 800 amps to1amp.

    This is done because we have no instrument for measuring of such a large current. The main use of his transformer is (a) distance protection; (b) backup protection; (c) measurement. ii) Voltage Transformer It is essentially a step – down transformer and step down the voltage in known ratio. The primary of these transformer consist of a large number of turn of fine wire connected across the line. The secondary way consist of a few turns and provides for measuring instruments and relay a voltage which is known fraction of the line voltage. Metering and Indicating Instrument

    There are several metering and indicating Instrument (e. g. Ammeters, Voltmeters, energy meter etc. ) installed in a Substation to maintain which over the circuit quantities. The instrument transformer are invariably used with them for satisfactory operation. Miscellaneous equipment In addition to above, there may be following equipment in a Substation : i) Fuses ii) Carrier-current equipment iii)Sub-Station auxiliary supplies Transformer There are three transformers in the incoming feeders so that the three lines are step down at the same time. In case of a 220KV or more KV line station auto transformers are used.

    While in case of lower KV line such as less than 132KV line double winding transformers are used Auto transformer Transformer is static equipment which converts electrical energy from one voltage to another. As the system voltage goes up, the techniques to be used for the Design, Construction, Installation, Operation and Maintenance also become more and more critical. If proper care is exercised in the installation, maintenance and condition monitoring of the transformer, it can give the user trouble free service throughout the expected life of equipment which of the order of 25-35 years.

    Hence, it is very essential that the personnel associated with the installation, operation or maintenance of the transformer is through with the instructions provided by the manufacture. Basic principles : The transformer is based on two principles: firstly, that an electric current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.

    Lightening Arrestors Lightening arrestors with earth switch lightening arrestors after the current transformer are used so as to protect it from lightening i. e. from high voltage entering into it. This lightening arrestor has an earth switch, which can directly earth the lightening. The arrestor works at 30° to 45° angel of the lightening making a cone. The earth switch can be operated manually, by pulling the switch towards ground. This also helps in breaking the line entering the station. By doing so maintenance and repair of any instrument can be performed. Line isolator

    The line isolators are used to isolate the high voltage flow through the line into the bus. This isolator prevents the instruments to get damaged. It also allows the only needed voltage and rest is earthed by itself. Potential transformers with bus isolators :- There are two potential transformers used in the bus connected both side of the bus. The potential transformer uses a bus isolator to protect itself. The main use of this transformer is to measure the voltage through the bus. This is done so as to get the detail information of the voltage passing through the bus to the instrument. There are two main parts in it (a) measurement; b) protection. Lightening arrestors :- Firstly we can see lightening arresters. These lightening arrestors can resist or ground the lightening if falls on the incoming feeders. The lightening arrestors can work in a angle of 30 degrees around them. They are mostly used for protection of the instruments used in the substation. As the cost of the instrument in the station are very high to protect them from high voltage from lightening these lightening arrestors are used. Fig. lightening arrestor It is a device used on electrical power systems to protect the insulation on the system from the damaging effect of lightning.

    Metal oxide varistors (MOVs) have been used for power system protection since the mid 1970s. The typical lightning arrester also known as surge arrester has a high voltage terminal and a ground terminal. When a lightning surge or switching surge travels down the power system to the arrester, the current from the surge is diverted around the protected insulation in most cases to earth. Capacitor bank The capacitor banks are used across the bus so that the voltage does not gets down till the require place. Wave trap Wave trap is an instrument using for tripping of the wave.

    The function of this trap is that it traps the unwanted waves. Its function is of trapping wave. Its shape is like a drum. It is connected to the main incoming feeder so that it can trap the waves which may be dangerous to the instruments here in the substation. Low pass filter when power frequency currents are passed to switch yard and high frequency signals are blocked. Line Isolator with E. B– To isolate the line from Sub Station and earth, it under shut down. THE FIRE PROTECTION The fire protection device should be kept in store yard for safety of equipments during storage. SINGLE LINE DIAGRAM (SLD)

    A Single Line Diagram (SLD) of an Electrical System is the Line Diagram of the concerned Electrical System which includes all the required ELECTRICAL EQUIPMENT connection sequence wise from the point of entrance of Power up to the end of the scope of the mentionedWork. As these feeders enter the station they are to pass through various instruments. The instruments have their usual functioning. They are as follows in the single line diagram. 1. Lightening arrestors, 2. C V T 3. Current transformer 4. Isolators with earth switch 5. Circuit breaker 6. Line isolator 7. BUS 8. Potential transformer with a bus isolator 9. Isolator 10.

    Current transformer 11. Circuit breaker 12. Lightening arrestors 13. Transformer 14. Lightening arrestors with earth switch 15. Circuit breaker 16. Current transformer 17. Isolator 18. Bus 19. Potential transformer with a bus isolator 20. A capacitor bank attached to the bus. The line diagram of the substation: This substation has the capacity of 220kv and can step down to 66kv using two input lines through the incoming feeders. The input feeders are namely: 1. Sahibabad (220KV) And 2. Noida 1 (Sec-62) (220KV) these feeders come into the substation with 220kv. The substation of 220kv/66kv /11kv has fifteen outgoing feeders, namely: 6 kv outgoing to Kondli-1 Kondli-2 Vivek Vihar-1 Vivek Vihar-2 11 kv outgoing to DDA Flat Fish Market-1 Telco-1 Telco-2 Local TR KHP S/STN-3 Fish Market-2 Telco-3 DDA SFS Flat Taj Appartment BPS Brief descriptions of the instruments in the line diagram are 1. Lightening arrestors : Here that are used in the incoming feeders so that to prevent the high voltage entering the main station. This high voltage is very dangerous to the instruments used in the substation. Even the instruments are very costly, so to prevent any damage lightening arrestors are used. The lightening arrestors do not let the lightening to fall on the station.

    If some lightening occurs the arrestors pull the lightening and ground it to the earth. In any substation the main important is of protection which is firstly done by these lightening arrestors. The lightening arrestors are grounded to the earth so that it can pull the lightening to the ground. The lightening arrestor works with an angle of 30° to 45° making a cone. 2. C V T : A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra high voltage signals and provide low voltage signals either for measurement or to operate a protective relay.

    In its most basic form the device consists of three parts: two capacitors across which the voltage signal is split, an inductive element used to tune the device to the supply frequency and a transformer used to isolate and further step-down the voltage for the instrumentation or protective relay. The device has at least four terminals, a high-voltage terminal for connection to the high voltage signal, a ground terminal and at least one set of secondary terminals for connection to the instrumentation or protective relay.

    CVTs are typically single-phase devices used for measuring voltages in excess of one hundred kilovolts where the use of voltage transformers would be uneconomical. In practice the first capacitor, C1, is often replaced by a stack of capacitors connected in series. This results in a large voltage drop across the stack of capacitors that replaced the first capacitor and a comparatively small voltage drop across the second capacitor, C2, and hence the secondary terminals. CVT 220 kV rating Type: WP-245 V Operating voltage: 220/ 3 kV Voltage factor: 1. 5 V for 30 sec. Test voltage: 460 kV Test impedance 1050 kv peak

    Ellec cap: 4400±10% PF of 50 Hz ± 5% Nominal intermediate voltage 20/ 3 kv Spark over voltage: 36 kv Voltage divider ratio 220000/ 3 /20000/ 3 Total thermal burden: 1000 VA Temperature categ: 10 to 55°C Total weight: 900 Kg. 3. Current transformer : Current transformers are basically used to take the readings of the currents entering the substation. Thistransformer steps down the current from 800 amps to 1 amp. This is done because we have no instrument for measuring of such a large current. The main use of this transformer is (a) distance protection; (b)backup protection; (c) measurement. Current transformer ating……………….. Core 1 core 2 core 3 Ratio (A/A) 800/1 400/1 800/1 400/1 800/1 400/1 Sec. Conn: 1S1-1S2 2S1-2S3 3S1-3S3 Accuracy class: 0. 2 5P 10 PS Burden (VA): 30 15 NA Highest system Voltage: 145 kV insulation burn 275 kV/ 65014 Vp 4. Lightening arrestors with earth switch : Lightening arrestors after the current transformer are used so as to protect it from lightening i. e. rom high voltage entering into it. This lightening arrestor has an earth switch, which can directly earth the lightening. The arrestor works at 30° to 45° angel of the lightening making a cone. The earth switch can be operated manually, by pulling the switch towards ground. This also helps in breaking the line entering the station. By doing so maintenance and repair of any instrument can b performed. 5. Circuit breaker : The circuit breakers are used to break the circuit if any fault occurs in any of the instrument. These circuit breaker breaks for a fault which can damage other instrument in the station.

    For any unwanted fault over the station we need to break the line current. This is only done automatically by the circuit breaker. There are mainly two types of circuit breakers used for any substations. They are (a) SF6 circuit breakers; (b) spring circuit breakers. The use of SF6 circuit breaker is mainly in the substations which are having high input kv input, say above 220kv and more. The gas is put inside the circuit breaker by force ie under high pressure. When if the gas gets decreases there is a motor connected to the circuit breaker. The motor starts operating if the gas went lower than 20. bar. There is a meter connected to the breaker so that it can be manually seen if the gas goes low. The circuit breaker uses the SF6 gas to reduce the torque produce in it due to any fault in the line. The circuit breaker has a direct link with the instruments in the station, when any fault occur alarm bell rings. The spring type of circuit breakers is used for small kv stations. The spring here reduces the torque produced so that the breaker can function again. The spring type is used for step down side of 132kv to 33kv also in 33kv to 11kv and so on. They are only used in low distribution side. . Line isolator : The line isolators are used to isolate the high voltage from flow through the line into the bus. This isolator prevents the instruments to get damaged. It also allows the only needed voltage and rest is earthed by itself. 7. BUS : The bus is a line in which the incoming feeders come into andget into the instruments for further step up or step down. The firstbus is used for putting the incoming feeders in la single line. There may be double line in the bus so that if any fault occurs in the one the other can still have the current and the supply will not stop.

    The two lines in the bus are separated by a little distance by a conductor having a connector between them. This is so that one can work at a time and the other works only if the first is having any fault. 8. Potential transformers with bus isolators : There are two potential transformers used in the bus connected both side of the bus. The potential transformer uses a bus isolator to protect itself. The main use of this transformer is to measure the voltage through the bus. This is done so as to get the detail information of the voltage passing through the bus to the instrument.

    There are two main parts in it (a)measurement; (b) protection. 9. Isolators : The use of this isolator is to protect the transformer and the other instrument in the line. The isolator isolates the extra voltage to the ground and thus any extra voltage cannot enter the line. Thus an isolator is used after the bus also for protection. 10. Current transformer : Current transformers are used after the bus for measurement of the current going out through the feeder and also for protection of the instruments. 11.

    Circuit breaker : The circuit breakers are used to break the circuit if any fault occurs in the circuit of the any feeders. 12. Lightening arrestors : The use of lightening arrestors after the bus is to protect the instrument in the station so that lightening would not affect the instruments in the station. 13. Transformer : There are three transformers in the incoming feeders so that the three lines are step down at the same time. In case of a 220kv or more kv line station auto transformers are used. While in case of lower kv line such as less than 132kv line double winding transformers are used. 4. Lightening arrestors with earth switch : The lightening arrestors are used with earth switch so that lightening would not pass through the instruments in the station. 15. Circuit breaker : The circuit breakers are used to break the circuit for any fault. 16. Current transformer : Current transformers are used to measure the current passing through the transformer. Its main use is of protection and measurement 17. Isolator : These are used to ground the extra voltage to the ground. 18. Bus : This bus is to carry the output stepped down voltage to the required place. 9. Potential transformer with a bus isolator : Two PT are always connected across the bus so that the voltage across the bus could bemeasured. 20. Capacitor bank attached to the bus : The capacitor banks are used across the bus so that the voltage does not gets down till the require place. Storage of equipments for the substation All the substation equipments/materials received on site should be stored properly, either in the outdoor yard or in the stores shade depending on the storage requirement of that particular equipment.

    The material received should be properly counted and checked for any damages/breakages etc. The storage procedure for main equipment is as follows: I. EHV C. T. s and P. T. s Normally, 220KV are packed in iron structures for extra supports with cross beams to avoid lateral movement while those of. 132KV C. Ts. and P. Ts are packed and transported in wooden crates vertically 132 KV C. Ts. and P. Ts. should be stored vertically and those of 220 KV and 400 KV should be stored in horizontal position. C. Ts and P. Ts. packed in wooden crates should not be stored for longer period as the packing would may deteriorate.

    The wooden packages should be stored on a cement platform or on M. S. Channels to avoid faster deterioration of the wooden crates. C. Ts and P. Ts packed in iron cases stored in horizontal position should be placed on stable ground. No C. Ts and P. Ts. should be unpacked in horizontal position. II. L. A. s. and B. P. I. These are packed in sturdy wooden case as the porcelain portion is very fragile. Care should be taken while unpacking, handling and storage due to this reason. III. Batteries, Acid, Battery charger C & R panel, A. C. D.

    Bs copper piping, clamp connectors, hardwares etc. should be stored indoor. IV. Circuit breakers: The mechanism boxes of 33 KV – V. C. Bs should be stored on raised ground and properly covered with tarpaulins or should be stored in door. The interrupter chambers should be stored on raised ground to avoid rain water in storage area. V. E. H. V. C. B-Now-a-days SF6 circuit breaker are used at EHV rottages. The control and operating cabinets are covered in polythene bags and are packed in wooden and iron crates. These should be stored on raised ground and should be covered with tarpaulins.

    The arcing chambers and support insulators are packed in iron crates and transported horizontally. The +ve pressure of SF6 gas is maintained in these arcing chambers to avoid the ingress of moisture. It should be ensured that this pressure is maintained during the storage. Other accessories like pr. Switches, density monitor, Air Piping, control cables, wiring materials, SF6 gas pipes; SF6 cylinder should be stored in store shed. VI. Power transformers: The main Tank – The transformer is transported on trailor to substation site and as far as possible directly unloaded on the plinth.

    Transformer tanks up to 25 MVA capacity are generally oil filled, and those of higher capacity are transported with N2 gas filled in them +ve pressure of N2 is maintained in transformer tank to avoid the ingress of moisture. This pressure should be maintained during storage; if necessary by filling N2 Bushings – generally transported in wooden cases in horizontal position and should be stored in that position. There being more of Fragile material, care should be taken while handling them. Rediators – These should be stored with ends duly blanked with gaskets and end plates to avoid ingross of moisture, dust, and any foreign materials inside.

    The care should be taken to protect the fins of radiators while unloading and storage to avoid further oil leakages. The radiators should be stored on raised ground keeping the fins intact. Oil Piping. The Oil piping should also be blanked at the ends with gasket and blanking plates to avoid ingross of moisture, dust, and foreign. All other accessories like temperature meters, oil flow indicators, PRVs, buchholtz relaormers are received on site with loose accessories hence the materials should be checked as per bills of materials.

    CONTROL AND RELAY PARTS – These are used to control the operations of breakers, isolates, through protective relays installed on these panels various protection schemes for transformers, lines etc, are provided on these panels. AC & DC DB’S – These are used for extending A. C. & D. C. supplies whenever required through various circuits. There are two main Buses in this arrangement connected by each diameter. i) Through either of line breakers the line side Main Bus can be charged normally (Bus-I). i) The line breaker, tie breaker and IInd Bus breaker if closed in series will charge the IInd Main Bus. iii) Outage on anyone Bus can be availed without interruption on any Bus. The second Bus can feed all the loads. iv) Breaker from any bay can be taken out for maintenance without interrupting the supply. v) For efficient working two diameters are required having source in each diameter preferably connected diagonally opposite to two different buses. vi) If both the sources are connected to same Bus (i. e. from one side only one tie breaker can be attended at a time). ii) If all the four breakers connected to Bus are out the transformer can be charged through the breaker from remote substation source. viii) Changing over as in case of 2 Bus or 3 Bus systems is not necessary as supply is not interrupted, in any case as said above. ix) All the breakers in the diameters are in energized position including tie breakers to keep the system in tact in case of any fault. x) On line or transformer fault the tie breaker with respective line or transformer breaker will trip. xi) On Bus fault on any Bus only the two breakers (of two diameters) connected Bus will Trip. ii) The Teed-point remains unprotected in any of line or transformer or bus faults hence the Teed point protection is given by differential relay. In case of this protection the breakers (2 Nos. ) connected to Teed point (tie breaker + Bus breaker) will Trip.. DC SUPPLY SYSTEM TYPES OF BATTERIES For power plant application there are two main type of stationary batteries namely led acid and nicked cadmium. The later type have a longer life and more robust require less attention and maintenance have a better type performance and have a higher energy/weight ratio.

    However these are much costlier and are not available in our country on the other hand , led acid batteries are readily available in our country and are cheaper and hence extensively used in power plant application. The lead-acid batteries have two types of cells, planet and tabular . For the same standby capability , planet cells are more costly as compare to tabular but the life expectancy of tabular but the life expectancy of tabular cells is only 8-10 years in comaparison to plant cells which expected life of cell is 15 years .

    Float and Boost Charging Float charger (at 235 volt +, as per designed ) is sized to supply the continuous DC load in addition to float current requirement of batteries incase of ac supply failure the battery system will automatically feed the lighting load and relays . To charge the battery initially or incase of complete discharge to be charge with boost charger (at 281 volt+, as per design ) the boost charger is capable of meeting high voltage/current requirement of batteries.

    In addition to this the periodic equalizing charge requirement is also made by boost chargers. It is essential to disconnect the batteries from load prior or boost charging so as to avoid the damage to DC equipment due high voltage supplied by boost charger. CONCLUSION Indian power sector is at the threshold of acquisition ,merger ,expansion and capacity addition . In the same length and breadth it is facing competitive environment as well striving hard to meet ever growing costumer demand. The Delhi Transco Ltd. here in after referred to as DTL is no exception Intervention on issues in relation with cultural Transformation aimed at building DTL as an institution through change management principle , process and particle is priority rather than option. Revisiting, reengineering and free evaluating management system , practices and directional leadership with nurturing acumen assumes paramount importance . Thereby seeing the uphill efforts by these companies , we as a citizen of this hugel4y populated country should have an eye on the conservation of power . We must see whether these power is available to rural sector another important sector which boost our economy and promote other sector too.

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