Summer Trainning report(SUBMITTED IN PARTIAL FULFILLMENT OF THE COURSE OF B.TECH.)

UNDERTAKEN AT

DELHI TRANSCO LIMITED

220 kV SUB-STATION

VASANT KUNJ

CH. DEVILAL MEMORIAL ENGG. COLLEGEPANNIWALAMOTA(SIRSA)(ESTABLISHED BY GOVT. OF HARYANA-2003) SUBMITTED TO:

SUBMITTED BY:

DEPARTMENT OF ELECTRICAL ENGG. OMENDER SINGHCDLMEC PANNIWALAMOTA 2606328(SIRSA) EE, FINAL YEAR

tABLE OF cONTENT1. Certificate

2. Acknowledgement3. About DELHI TRANSCO LIMITED4. Electric power transmission5. DTL 220 kV sub-station Vasant kunj6. Sub-station single line diagram7. Transformer8. Circuit breaker9. Current Transformer10. Capacitive Voltage Transformer11. Potential Transformer

12. Power Line Communication Carrier13. Shunt Capacitor Bank

14. Reactor

15. Lightning Arrestor

16. 220 kV Equipments17. 66 kV Equipments

18. 11 kV Equipments

19. 400 kVA Local Transformer20. Battery and Battery Charger

21. Protection of Transformer22. Protection of Feeder

23. BibliographyCERTIFICATE

This is to certify that OMENDER SINGH student of Batch 2006 Electrical Engineering IIIrd Year; Ch.Devi Lal Memorial Engg. College, Panniwala Mota (Sirsa) has successfully completed his summer training at Delhi Transco Limited 220 kV Sub-Station C-9 Vasant Kunj New Delhi for six week from 10th July to 20th August 2009 He has completed the whole training as per the training report submitted by him.

Assistant Manager

DTL C-9 Vasant Kunj New DelhiAcknowledgement

With profound respect and gratitude, I take the opportunity to convey my thanks to complete the training here.

I am extremely grateful to all the technical staff of the 220 kV Substation Vasant Kunj for their co-operation and guidance that helped me a lot during the course of training. I have learnt a lot working under them and I will always be indebted of them for this value addition in me.

I would also like to thank the training incharge of Ch.Devi Lal Memorial Engg. College, Panniwala Mota (Sirsa) and the entire faculty members for their effort and constant co-operation which has been a significant factor in the accomplishment of my summer training.

About DELHI TRANSCO LIMITED1. 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 Edisons 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 Authority (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.

2. 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.

3. 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.

4. Notification of Industrial Policy Resolution:- In the year 1952 the Government of India notified the Industrial Policy Resolution under the Industries Development and Regulation Act 1951 where under the electricity industry, which included all aspects of generation, transmission, distribution, and supply of electricity, came to be reserved for State sector. In other words, the private sector was not entitled to commence any business of generation, transmission, distribution, and (or) supply of electricity.

5. Formation of Delhi Electric Supply Undertaking by promulgation of DMC Act 1957:- After the promulgation of the Delhi Municipal Corporation Act 1957, the DSEB was dissolved and the functions of DSEB were taken over by Delhi Electric Supply Undertaking (DESU), which came into existence in 1958. After the formation DESU, the generation and distribution of electricity to all the areas of Delhi came under DESU and the employees of erstwhile DSEB were also absorbed by DESU.

6. Constitution of Delhi Vidyut Board: - The Government of the National Capital Territory of Delhi vide notification No. F.11 (10)/92-LSG /PF (II) dated 24.02.1997, issued under the Electricity (Supply) Act, 1948, constituted a separate Electricity Board, i.e. the Delhi Vidyut Board (DVB) for the NCT of Delhi w.e.f. 24.02.1997 for the purpose of generation and distribution of power to the entire area of NCT of Delhi except the areas falling within the jurisdiction of NDMC and Delhi Cantonment Board.

7. Practical difficulties in the working of Delhi Vidyut Board:- The activities of Delhi Vidyut Board from its inception, and as a matter of fact even prior thereto when the activities were being undertaken by DESU, were not financially viable on account of several factors affecting the electricity industry including the high level of losses in the system and the revenues being not able to meet the cost with result that like other State electricity Boards, Delhi vidyut Board suffered operating deficit in aggregate to the tune of Rs.2,386.72 crore during the period from 1995-96 to 2000-01. In addition the Delhi Vidyut Board was required to make adequate provision for bad and doubtful debts. The cumulative effect of all these factors was that the Delhi Vidyut Board was not in a position to meet its financial obligations and commitments including the payment for power purchased from generation companies and suppliers, such NTPC Limited, Nuclear Power Corporation Limited, national Hydroelectric Corporation Limited, etc., etc.

8. Unbundling of Delhi Vidyut Board in six entities: - In the recent for alleviating the concerns of consumers in the power sector, some reforms started gaining momentum. In that very direction with a view to safeguard the overall interests of the consumers GNCTD took some policy initiatives as as a result of which DVB was split into six Companies, viz., BSES Rajdhani Power Limited, BSES Yamuna Power Limited, North Delhi Power Limited, Delhi Transco Limited, Indraprastha Power Generation Company Limited, and Delhi Power Company Limited, as per the provisions contained in Delhi electricity reform Act 2000 read with Delhi Electricity Reform (Transfer Scheme) Rules 2001.9. 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.

10. 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.

11. 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.

Electric Power TransmissionElectric power transmission is the bulk transfer of electrical power (or more correctly energy), a process in the delivery of electricity to consumers. A power transmission network typically connects power plants to multiple substations near a populated area. The wiring from substations to customers is referred to as Electricity distribution, following the historic business model separating the wholesale electricity transmission business from distributors who deliver the electricity to the homes.[1] Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers, and may allow exploitation of low-grade fuel resources such as coal that would otherwise be too costly to transport to generating facilities.

Usually transmission lines use three phase alternating current (AC). Single phase AC current is sometimes used in a railway electrification system. High-voltage direct current systems are used for long distance transmission, or some undersea cables, or for connecting two different ac networks.

Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in transmission. Power is usually transmitted as alternating current through overhead power lines. Underground power transmission is used only in densely populated areas because of its higher cost of installation and maintenance when compared with overhead wires, and the difficulty of voltage control on long cables.

Overhead conductors are not covered by insulation. The conductor material is nearly always an aluminum alloy, made into several strands and possibly reinforced with steel strands. Copper was sometimes used for overhead transmission but aluminum is lower in weight for equivalent performance, and much lower in cost. Overhead conductors are a commodity supplied by several companies worldwide. Improved conductor material and shapes are regularly used to allow increased capacity and modernize transmission circuits. Thicker wires would lead to a relatively small increase in capacity due to the skin effect that causes most of the current to flow close to the surface of the wire.

Today, transmission-level voltages are usually considered to be 220 kV and above. Lower voltages such as 66 kV and 33 kV are usually considered sub-transmission voltages but are occasionally used on long lines with light loads. Voltages less than 33 kV are usually used for distribution. Voltages above 230 kV are considered extra high voltage and require different designs compared to equipment used at lower voltages.

DTL 220 kV Sub-Station

Vasant Kunj1. Vasant Kunj Sub-station receives electrical supply from the Mehrauli 220 kV grid by two 220 kV three phase lines2. The voltage is stepped down from 220 kV to 66 kV by 100 MVA Transformer.The 66 kV transmission lines are for the following circuits(C-Block Vasant Kunj Ckt I

(C-Block Vasant Kunj Ckt II

(D-Block Vasant Kunj Ckt I

(D-Block Vasant Kunj Ckt II

(Palam

(Ridge Valley Ckt I(Ridge Valley Ckt II

3. The voltage is further stepped down from 66 kV to 11 kV by 20 MVA Transformer.

The 11 kV transmission lines are for the following circuits

(Vasant Kunj C-8 s/s-1

(Vasant Kunj C-9 s/s-5

(Rang Puri

(IAAI Colony

(Vasant Kunj C-9 s/s-2

(Spinal Injury Hospital

(AV Hotel

(Vasant Kunj C-9 s/s-9 feeder 2(MahipalpurComponents of a Substation

1. Power transformer

2. Circuit Breaker

3. Current Transformer

4. Isolator w/o earth

5. Isolator with earth

6. Capacitive Voltage Transformer

7. Potential Transformer

8. Power Line Communication Carrier9. Neutral Current Transformer

10. Shunt Capacitor Bank11. Reactor

12. Lightning Assrestor

TransformerA transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors the transformer's coils. Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary to the number of turns in the primary as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP.

Losses in a Transformer

Winding resistance

Current flowing through the windings causes resistive heating of the conductors. At higher frequencies, skin effect and proximity effect create additional winding resistance and losses. Hysteresis losses

Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected. Eddy currents

Ferromagnetic materials are also good conductors, and a solid core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness.Magnetostriction

Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction. This produces the buzzing sound commonly associated with transformers, and in turn causes losses due to frictional heating in susceptible cores. Mechanical losses

In addition to magnetostriction, the alternating magnetic field causes fluctuating electromagnetic forces between the primary and secondary windings. These incite vibrations within nearby metalwork, adding to the buzzing noise, and consuming a small amount of power. Stray losses

Leakage inductance is by itself lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat.[30]

Components of a TransformerTerminal Bushings - The bushing is a hollow insulator, allowing a conductor to pass along its centre and connect at both ends to other equipment. Bushings are often made of wet-process fired porcelain, and may be coated with a semi-conducting glaze to assist in equalizing the electrical stress along the length of the bushing. The inside of the bushing may contain paper insulation and the bushing is often filled with oil to provide additional insulation. Bushings for medium-voltage and low-voltage apparatus may be made of resins reinforced with paper.Buchholz Relay - A Buchholz relay, also called a gas relay or a sudden pressure relay, is a safety device mounted on some oil-filled power transformers and reactors, equipped with an external overhead oil reservoir called a conservator. The Buchholz Relay is used as a protective device sensitive to the effects of dielectric failure inside the equipment. The relay has two different detection modes. On a slow accumulation of gas, due perhaps to slight overload, gas produced by decomposition of insulating oil accumulates in the top of the relay and forces the oil level down. A float operated switch in the relay is used to initiate an alarm signal. If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. This flow of oil operates a switch attached to a vane located in the path of the moving oil. This switch normally will operate a circuit breaker to isolate the apparatus before the fault causes additional damage. Buchholz relays have a test port to allow the accumulated gas to be withdrawn for testing. Flammable gas found in the relay indicates some internal fault such as overheating or arcing, whereas air found in the relay may only indicate low oil level or a leak.

Conservator It is cylindrical tank connected to the main shell of the transformer. When transformer oil expands due to the heat generated in the windings, the oil travels to the conservator tank via Buchholz Relay into the conservator tank. When oil cools down, it travels back to the main shell from the conservator tank.Breather The breather is connected to the conservator tank. It consists of a small cylindrical chamber filled with silica gel. When the oil expands, oil rushes to the conservator tank thus air is expelled out of it via the breather. When oil cools down, it travels back to the tank creating vacuum in the tank and sucking in air from the atmosphere. The air sucked in passes through the silica gel which absorbs the moisture from the air, hence air entering the tank is devoid of any moisture which is essential in maintaining the quality and insulation level of the oil. Transformer Breathers eliminate oil thickening and deteriorating when air space above it expands and contracts with climatic variations.Marshalling Box It a box placed next to the transformer which displays real time winding and oil temperature. It raises alarm and also issues tripping if the temperature rises beyond safe limits.Circuit BreakerA circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

The most common insulating fluids used are :-1. Air at Atmospheric Pressure

2. Compressed Air

3. Oil which produces hydrogen for Arc extinction

4. Ultra-high Vaccum

5. Sulphur hexafluoride gas

Arc interruptionMechanical low-voltage circuit breakers use air alone to extinguish the arc. Larger ratings will have metal plates or non-metallic arc chutes to divide and cool the arc. Magnetic blowout coils deflect the arc into the arc chute. In larger ratings, oil circuit breakers rely upon vaporization of some of the oil to blast a jet of oil through the arc. [2]Gas (usually sulfur hexafluoride) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the sulfur hexafluoride (SF6) to quench the stretched arc. Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material), so the arc quenches when it is stretched a very small amount (