33 KV Substations & Automatic Power Factor Controller

Submitted By:Girish GuptaId no. 42206,

4th Year,Electrical Engineering,College of Technology,

Govind Ballabh Pant University of Agriculture & Technology,

Pantnagar

Project ReportSummer Training,Electrical Section,

Service Block,Keshav Dev Institute of Petroleum Exploration,

ONGC Dehradun.

Sl.No.

Topic PageNo.

1. Office Order 22. Certificate 43. Acknowledgement 54. Oil and Natural Gas Corporation Ltd. 6

Mission and Vision of ONGC 7 Objectives of ONGC 8 History of ONGC 8 Achievements of ONGC 10 ONGC today 11 Some facts about ONGC 12 Global Ranking 13 Institutes of ONGC 14 KDMIPE 15

5. Training Area : Service Block 17 33 KV Substation 18 Components of Electrical Distribution 20 Explanation 25

6. Automatic Power Factor Controller 28 Introduction 29 Power Factor Correction for Linear Loads 34 Power Factor Correction for Non Linear Loads 35 APFC 38 Use of APFC in ONGC Complex 41 APFC Working 43

7. Specification for APFC with LT Capacitors 478. Conclusion 549. Bibliography 55

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INDEX

CERTIFICATEThis is to certify that Mr. Girish Gupta, students of 4th year, Electrical Engineering, Bachelor of Technology, College of Technology, Govind Ballabh University of Agriculture & Technology, Pantnagar has undergone summer training at electrical Section, Service Block, KDMIPE, ONGC Ltd., Kaulagarh Road, Dehradun from 2nd

June 2014 to 3rd July, 2014 under the overall guidance of Er. Vivek Malaviya, S.E. (Electrical).

Mr. Girish Gupta has successfully completed his training and submitted the training project report. During the period of training he was found sincere, punctual and regular. His conduct and behavior was very good.

Er. Vivek Malaviya

Super-Intending Engineer (Electrical)

ONGC Ltd.

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ACKNOWLEDGEMENT

I am very thankful to Dr. Sanjay Bhutani, DGM (chemistry) who gave me an opportunity to undergo training at the Electrical Section, Service Block, KDMIPE, ONGC Ltd., Dehradun.

I am also thankful to Er. Vivek Malaviya, S.E. (Electrical) who organized the training in a systematic manner and guided me through the whole training programme.

I would also like to thank all officer/officials who guided and helped me at each and every step in the training programme.

Girish Gupta

Id no. 42206

4th year,

Electrical Engineering

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4. OIL AND NATURAL GAS CORPORATION LIMITED (ONGC)

Oil and Natural Gas Corporation Limited (ONGC) was incorporated on June 23, 1993. It is an Indian public sector petroleum company. It is a Fortune Global 500 Company ranked 335 th and contributes 77% of India’s crude oil production and 81% of India’s natural gas production.

ONGC was set up as a commission on August 14, 1956. Indian government holds 74.14% equity stake in this company. ONGC is one of Asia’s largest and most active companies involved in exploration and production of oil. It is involved in exploring for and exploiting hydrocarbons in 26 sedimentary basins of India. It has supported more than 600 million metric tons of crude oil and supplied more than 200 billion cubic meters of gas since its inception, thus fuelling the increasing energy requirements for the Indian economy. To sustain this growth, ONGC has drawn up ambitious strategic objectives, which include doubling the oil and gas reserve.

Having accreted six billion tons oil and oil equivalent reserves in its first 45 years of operation, ONGC now aims to double these reserves by 2020. The second strategic objective is to augment the global recovery factor from the existing 28% to the global norm of 40% in next 20 yrs.

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4.1 MISSION AND VISION OF ONGC

To be a world class Oil and Gas Company integrated in energy business with dominant Indian leadership and Global Presence.

World Class

Dedicated to excellence by leveraging competitive advantages in R&D and technology with involved people.

Imbibe high standards of business ethics and organizational values. Abiding commitment to safety, health and environment to enrich quality of community

life. Foster a culture of trust, openness and mutual concern to make working a stimulating

and challenging experience for the people. Strive for customer delight through quality products and services.

Integrated in Energy Business

Focus on domestic and international oil and gas exploration and production business opportunities.

Provide value linkages in other sectors of energy business. Create growth opportunities and maximize shareholder value. Retain dominant position in Indian petroleum sector and enhance India’s energy

availability.

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4.2 OBJECTIVES OF ONGC

To develop and sustain core values. To develop business leaders for tomorrow. To provide job contentment through empowerment, accountability and responsibility. To build and upgrade competencies through virtual learning, opportunities for growth

and providing challenges in the job. To foster a climate of creativity, innovation and enthusiasm. To enhance the quality of life of employees and their family. To inculcate high understanding of ‘Service’ to a greater cause.

4.3 HISTORY OF ONGC

In August 1956, the Oil and Natural Gas Commission was formed. Raised from mere Directorate status to Commission, it had enhanced powers. In 1959, these powers were further enhanced by converting the commission into a statutory body by an act of Indian Parliament.

1960-1990Since its foundation stone was laid, ONGC is transforming India’s view towards Oil and Natural Gas by emulating the country’s limited upstream capabilities into a large viable playing field. ONGC, since 1959, has made its presence noted in most parts of Indian and in overseas territories. ONGC found new resources in Assam and also established the new oil province in Cambay basin (Gujarat). In 1970 with the discovery of Bombay High (now known as Mumbai High), ONGC went offshore. With this discovery and subsequent discovery of huge oil fields in the Western offshore, a total of 5 billion tons of hydrocarbon present in the country was discovered. The most important contribution of ONGC, however, is its self-reliance and development of core competence in exploration and production activities at a global competitive level.

Post 1990ONGC’s HAL Dhruv helicopter started operating off the coast of Mumbai. Post 1990, liberalization in the economic policy was brought into effect; subsequently partial disinvestments of government equity in Public Sector Undertakings were sought. As a result, ONGC was re-organized as a limited company and after conversion of the business of the erstwhile Oil and Natural Gas Commission to that of Oil and Natural Gas Corporation Ltd in 1993, 2 % of shares through competitive bidding were disinvested. Further expansion of equity was done by 2% share offering to ONGC employees. Another big leap was taken in March 1999,

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when ONGC, Indian Oil Corporation (IOC) and Gas Authority of India Ltd. (GAIL) agreed to have cross holding in each other’s stock. Consequently the Government sold off 10% of its shareholding in ONGC to IOC and 2.5% to Gail. With this, the Government holding in ONGC came down to 84.11%. In 2002-03 ONGC took over Mangalore Refinery and Petrochemicals Ltd. from Birla group and announced its entrance into retailing business. ONGC also went to global fields through its subsidiary, ONGC Videsh Ltd. (OVL). ONGC has made major investments in Vietnam, Sakhalin and Sudan and earned its first hydrocarbon revenue from its investment in Vietnam.

In 2003, ONGC Videsh Limited (OVL), the division of ONGC concerned with its foreign assets, acquired Talisman Energy's 25% stake in the Greater Nile Oil project.

In 2009, ONGC discovered a massive oil field, with up to 1 billion barrel reserves of heavy crude, in the Persian Gulf off the coast of Iran. Additionally, ONGC also signed a deal with Iran to invest US$3 billion to extract 1.1 billion cubic feet of natural gas from the Farzad B gas field.

In 2011, ONGC applied to purchase of 2000 acres of land at Dahan to process offshore gas. ONGC Videsh, along with Statoil ASA (Norway) and Repsol SA (Spain), has been engaged in deep water drilling off the northern coast of Cuba in 2012. On 11th August 2012, ONGC announced that it had made a large oil discovery in the D1 oilfield off the West coast of India, which will help it to raise the output of the field from around 12,500 barrels per day (bpd) to a peak output of 60,000 bpd.

In November 2012, OVL agreed to acquire Conoco Phillips 8.4% stake in the Kashagan oilfield in Kazakhstan for around US$5 billion, in ONGC's largest acquisition to date. The acquisition is subject to the approval of the governments of Kazakhstan and India and also to other partners in the Caspian Sea field waiving their pre-emption rights.

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4.4 ACHIEVEMENTS OF ONGC

ONGC has been ranked at 198 by the Forbes Magazine in their Forbes Global 200 list for the year 2007.

ONGC has featured in the 2008 list of Fortune Global 500 companies at position 335. ONGC is ranked as Asia’s best Oil and Gas Company, as per a recent survey conducted

by US-based magazine Global Finance. 2nd biggest E&P company, as per the Platts Energy Business Technology (EBT) Surveys

2004. Ranks 24th among Global Energy Companies by Market Capitalization in PFC Energy 50

(December 2004) Economic Times 500, Business Today 500, Business Baron 500 and Business Week

Recognizes ONGC as most valuable Indian Corporate, by Market Capitalization, Net worth and Net Profits.

It was conferred with 'Maharatna' status by the Government of India in November 2010. The Maharatna status to select PSUs allows more freedom in decision making.

In 2011, ONGC was ranked 39th among the world's 105 largest listed companies in 'transparency in corporate reporting' by Transparency International making it the most transparent company in India.

In April 2013, it was ranked at 155th place in the Forbes Global 2000 for 2012. ONGC was ranked as the Most Attractive Employer in the Energy sector in India, in

the Randstad Awards 2013. ONGC received the ‘Golden Peacock Award 2013’ for its HSE practices. In February 2014, FICCI conferred it with Best Company Promoting Sports Award. In May 2014, ONGC was accorded with FORTUNE World's Most Admired Company. In June 2014, ONGC was ranked 217th in the world and 3rd in India

in the Newsweek Green Ranking, the world’s most recognized assessments of corporate environmental performance.

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4.5 ONGC TODAY

ONGC ranks as the Numero Uno Oil & Gas Exploration & Production (E & P) Company in Asia, as per Platts 250 Global Energy Companies List for the year 2007.

ONGC is the only Company from India in the Fortune Magazine's list of the World's Most Admired Companies 2007. ONGC is 9th position in the Industry of Mining, crude oil production.

ONGC ranks 239th position in the prestigious Forbes Global 2000 and Numero Uno ranking amongst Indian Companies.

ONGC contributes over 78 per cent of India's oil and gas production. ONGC's overseas arm ONGC Videsh Limited (OVL) projects are spread out in Vietnam,

Russia, Sudan, Iraq, Iran, Libya, Myanmar, Syria, Qatar, Egypt, Cuba, Nigeria Sao Tome Principe, Brazil, Nigeria and Columbia. OVL Currently has participation in 29 E & P Projects in 15 Countries. Out of the existing 29 Projects, OVL is Operator in 14 Projects and Joint Operator in 2 Projects in 9 Countries.

Today ONGC uses one of the Top Ten Virtual Reality Interpretation facilities in the world. ONGC has one of the biggest ERP implementations in the Asia through collaboration

with SAP AG. The manpower in ONGC currently consists of a dedicated team of nearly 40,000

professionals. ONGC posted a net profit of Rs. 156.429 billion, the highest by any Indian company. In

the financial year 2006-07 and has a net worth Rs. 614 billion. It has also contributed over Rs. 286 billion 10 the exchequer in the same period.

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Sakhlin Oil field owned by ONGC Videsh, Russia

4.6 SOME FACTS ABOUT ONGC

Oil and Natural Gas Corporation limited (ONGC India) is considered Asia's best oil & Gas Company. It ranks as the 2nd biggest E & P company (and 1st in terms of profits), as per the Platts Energy Business Technology (EBT) Survey 2004. It ranks 24th among Global Energy Companies by Market Capitalization in PFC Energy 50 (December 2004). ONGC was ranked 17th till March 2004. Before the shares prices dropped marginally for external reasons.

Activities Everyone who works at ONGC India is responsible for protecting the environment, health and safety of our people and communities worldwide. Our commitment to the performance is an integral part of our business, and achieving cost-effective solution is essential to our long-term success.

The dedication to the causes of environment and safety in ONGC is amply demonstrated by the fact that a separate institute named Institute of Petroleum Safety, Health and Environment Management (IPSHEM) had been set up way back in 1989 to deal with these issues. Oil and Natural Gas Corporation Limited ONGC's safety policy seeks to provide safe and healthy working conditions and enlist the active support of all staff in achieving these ends.

The development activities of ONGC have been planned on sound ecological principle and incorporate appropriate environmental safeguards.

ONGC Represents India's Energy Security: ONGC has single-handedly written India's hydrocarbon saga by the following methods:-

Building 6 billion tons of In-place hydrocarbon reserves with more than 300 discoveries of oil and gas; in fact, 5 out of the 6 producing basins have been discovered by ONGC: out of these in place hydrocarbons In domestic acreage, Ultimate Reserves are 2.1 Billion Metric tons (BMT) of Oil Plus on Equivalent Gas (O+OEG).

Cumulatively producing 685 Million Metric tons (MMT) of crude and 375 Billion Cubic Meters (BCM) of Natural Gas, from 115 fields.

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4.7 GLOBAL RANKING ONGC ranks as the Numero Uno Oil & Gas Exploration & Production (E&P) Company in

the world, as per Platts 250 Global Energy Companies List for the year 2008 based on assets, revenues, profits and return on invested capital (R01C)

ONGC ranks 20th among the Global publicly-listed Energy companies as per PFC Energy 50(Jan 2008)

ONGC is the only Company from India in the Fortune Magazine's list of the World's Most Admired Companies 2007.

Occupies 152nd rank in "Forbes Global 2000" 2009 list (up 46 notches than last year) of the elite companies across the world ; based on sales, profits, assets and market valuation during the last fiscal. In terms of profits, ONGC maintains its top rank from India.

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4.8 INSTITUTES OF ONGC

ONGC conducts institutional research and development in the oil and gas, and other related sectors. It has established separate institutions to undertake specific activities in key areas of exploration, drilling, reservoir management, production technology, ocean engineering, safety and environment protection. These institutions function in the form of nine independently managed R&D centers. There R&D institutes with highly experienced and highly qualified manpower support exploration and production activities of ONGC. These institutes are:-

1. Keshav Dev Malviya institute of Petroleum Exploration (KDMIPE), Dehradun.2. Institute of Drilling Technology (IDT), Dehradun.3. ONGC Academy, Dehradun4. Institute of Reservoir Studies (IRS), Ahmedabad.5. Institute of Oil and Gas Production Technology (IOGPT), Mumbai.6. Institute of Engineering and Ocean Technology (IEOT), Mumbai.7. Institute of Petroleum and Safety Environment Management (IPSEM), Margao.8. Institute of Bio-Technology and Geotectonic, Guwahati.

ONGC IN DEHRADUN

The headquarters of Oil & Natural Gas Corporation LTD (ONGC) is situated in Dehradun along with the following offices.

Tel Bhavan (headquarter) Keshav Dev Malviya Institute of Petroleum Exploration (KDMIPE) Institute of Drilling Technology (IDT) ONGC Academy (formerly Institute of Management Development (IMD)) Geo Data Processing and Interpretation Center (GEOPIC) Exploration & Development Directorate (E & D Dte.)

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4.9 KDMIPEKeshava Deva Malviya Institute of Petroleum Exploration (KDMIPE) is located in picturesque valley of Dehradun in the state of Uttarakhand. It was founded in 1962 with an objective to provide geo-scientific back up to the exploratory efforts of India's National oil company, ONGC.

The Institute was rechristened as Keshava Deva Malviya Institute of Petroleum Exploration (KDMIPE) on 19th December, 1981 by the then Prime Minister of India Late Mrs. Indira Gandhi in the memory of the Father of Indian Petroleum industry and first chairman of ONGC-Late Shri Keshava Deva Malviya. Since its inception the Institute is continuously providing its geo scientific support towards finding more oil and gas in various basins within India and globally, wherever ONGC is seeking business.

Presently the Institute is the nodal agency for multidisciplinary synergistic basin scale and domain specific research in exploration. The Institute has strength of around 300 highly experienced scientists and technical officers in the field of Geo scientific research, Basin research, Resource and Acreages appraisal and E & P data management. It is equipped with state of the art facilities, soft wares and cutting edge technologies. The Institute caters to the needs of all the basins currently under active exploration and producing Assets, both in India as well as overseas operation by our sister company ONGC Videsh Limited, We also provide consultancy services in areas of geoscience and exploration to national and international oil companies.

KDMIPE has been an ISO: 9001: 2000 certified institute from 3.12.2004 to 03.12.2007. To achieve the highest standard of Quality, Health, Safety and Environment, KDMIPE has strived to get QHSE certificate and the same was awarded to KDMIPE on 13th June, 2008.

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Business ActivitiesKeshava Deva Malaviya Institute of Petroleum Exploration is a sub-unit of the public sector petroleum giant Oil and Natural Gas Corporation Limited. The product developed at KDMIPE relates to various processes and technologies connected to exploration technology. Various innovations, problem solving measures, indigenous resourcing and applied R & D are carried out that totally caters to the requirements of the different assets/basins of its parent company, ONGC.

The parent company provides the key support required for functioning of the institute, which includes Manpower, Finance, Infrastructure, Equipments etc. and facilitates Field Validation.

Core Strengths are: Basin evaluation and opening of new areas of exploration. Geoscientific laboratory analysis (Sedimentology. Biostratigraphy, Geochemistry,

Reservoir, Petro physics and Gravity-Magnetic) Developing exploration concepts and models. Play models and petroleum systems. Attain breakthrough in exploration in frontier basins. Hydrocarbon Resource Appraisal of Indian and foreign basins. E & P data network. Induction of appropriate technologies and related skills.

With an objective to foster Applied-Basic and Fundamental research continuum in the field of G & G and Petroleum exploration, the Institute has been developing academia-industry strategic alliances in the form of R & D collaboration with various National and International universities and Institutes. Our national collaborative partners are Andhra University, BHU, Varanasi, Calcutta University, Indian Institute of Technology, Kanpur, Kharagpur, Indian School of Mines (ISM) Dhanbad, National Geophysical Research Institute (NGRI) Hyderabad, Dibrugarh University, Presidency College, Delta Studies Institute (DSI), Visakhapatnam and WIHG. In the international arena we had collaboration with ARC, Canada, UNOCAL, Oregon State University, University of Southern California, and EGI, USA, BGR, Germany, IFP France, Cambridge University, UK and Petroleum Gas University of Ploiesti, Romania.

We have recently taken new initiatives in non-conventional energy sources, and inducted Synthetic Aperture Radar (SAR), Sea Bed Logging (SBL), Q-Marine and GX Technology and other contemporary processing and interpretation soft wares on application tools. Institute with its intellect and state of the art technology continuously strive for improving success ratio in exploration and opening up of new basins and provinces for overall energy security of the nation.

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5. TRAINING AREA: SERVICE BLOCK, KDMIPE, ONGC, DEHRADUN

The service block at KDMIPE deals with the power Supply system, air conditioning plant, pump house and UPS systems which are required for smooth running of various activities at ONGC. The service block constitutes of various functional blocks. These blocks are:

1. 33KV electric substation 2. Captive power generation and distribution system 3. Air conditioning plant 4. Electric workshop 5. A. C. workshop

Functions of Service Block

1. Ensure that the power supply at the research institute is regular and regulated. 2. Make sure that the workstations have uninterrupted power supply via UPS systems. 3. Managing the water supply in the institute. 4. Making surety about the A. C. Plant functioning properly.

Training at the Service Block

The service block at KDMIPE provides training to the engineers who are either in the electrical stream or in the mechanical stream. The service block has excellent facilities for pursuing training. It has its own air conditioning plant, which is of prime interest to the mechanical engineers and the UPS system and generator house which is essential for electrical engineers.

All the facilities are very important for any institute hence the service block plays a vital role for the proper functioning of the KDMIPE since it is a research institute hence It should have run excess to power supply and the time otherwise the research work going on may suffer.

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5.1 33 KV SUBSTATION

INTRODUCTIONSub-stations are vital element in a power supply system of industrial enterprises. They serve to receive, convert and distribute electrical energy in KDMIPE campus of ONGC. 33 KV sub-station was commissioned on June 1985 It gets power supply from KAULAGARH POWER HOUSE through underground cables. In case of power failure, electric power is supplied from GENERATOR HOUSE (4×1000KVA) situated in service block.

GENERAL DISCRIPTIONThe 33KV line is received from UPCL in the main panel and the necessary measurements are made. Its output (33KV) is fed to the high-tension bus bar. From the high-tension bus bar the supply is given to four panels, which are in parallel connection through 630 A, 33 KV, OCB. In the panels also the necessary measurements are made after stepping down the supply with help of instrument transformers. Here also there are relays installed which aid in the protection of the panels.

From the four paralleled panels the supply is given to the step-down transformers through underground cables (at 33KV). The specifications of the transformers are 1600 KVA, 133KV/433 KV/50Hz. The primary (High Tension) side of the transformer is DELTA connected (3 phase, 3 wire system) with 33 KV input and secondary (Low Tension) side of the transformer is STAR connected with the star point grounded via neutral (3 phase, 4 wire system) with 433V output. An on load tap changer is also connected on the H. T side of the transformer. By changing the taps of the tap changer, the output voltage on the low-tension side can be increased or decreased as required. The service voltage of the tap changer is 33 KV and the normal working current is 16.6 A, The output of each of these transformers is fed to a 3000 ALT bus bar through a 3200A switch. The necessary measurements regarding voltage, amperage, frequency and power factor are made again after stepping down through instrument transformers on the 3000 A connecting is given through fuses, earth fault relays, over current relays, under voltage relays etc. The output of the transformers is fed to four independent 3000A bars which connect it to L. T. Bars. The stepping down by the help of the transformers and various measurements are down to this connecting bus bar the output of each transformer is fed to four segments L. T. Independently which are coupled together by the help of couplers. The function of the bus coupler is to couple the load on one or more bus bar to other bus bars so that all load requirements are fulfilled in case of failure of transformers. From this L. T. Bus bar various feeders are taken out and 3-phase supply is given to various places as and when required. A capacitor circuit is provided with each L. T. Bus bar segment to improve power factor.

In case there is a power failure from UPSEB so that transformers cannot be activated. 4 diesel generators sets of capacity 1000KVA are provided which can supply the requisite power for fulfilling the load requirements. The diesel generator sets are controlled and synchronized by a panel provided in the generator house. The output of the single alternator or all the alternators working in parallel and in synchronization are fed to the diesel generator set bus bar through a

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1600A switch. From the diesel generator set bus bar, 4 parallel cables corresponding to the 4-diesel set is fed to the L. T. Bus bar through a 2000A circuit breaker. These cables are the 1600A bus bars. The various measurements as regarding frequency, voltage and amperage and power factor are made on the 1600A bus bar by stepping down the voltage and current to measureable ranges by the help of instrument transformers. System protection is provided through earth fault relays, over current relays etc. Another safety protection that is provided is the backup relay whose function is the prevention of switching on of either transformer of the diesel generator set if the corresponding transformer is working and supplying to the L. T. Bus bar and vice versa.

STEP DOWN TRANSFORMERS The transformer is the device that transfers electrical energy from one circuit to other through the medium of magnetic field without the change in frequency. The primary and the secondary of the transformer are coupled magnetically. In a step down transformer, the Primary has a large number of windings than the secondary, such that the secondary voltage is lower than the primary voltage. As there are no moving parts, this has high efficiency and requires negligible amount of maintenance and supervision. The transformer has a central laminated core over which windings are made. This tank is provided with fins, radiators, conservator and silica gel breather.

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5.2 COMPONENTS OF ELECTRICAL DISTRIBUTION

SUBSTATION A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.There are different types of substation. These are:-

1. TRANSMISSION SUBSTATION A transmission substation is one whose main purpose is to connect together various transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, the substation contains high voltage switches that allow lines to be connected together or isolated for maintenance. Transmission substations can range from simple to complex. A small 'switching station' may be a little more than a bus plus some circuit breakers. The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels and a large amount of detection and control equipment (capacitors, relays, switches, breakers, voltage and current transformers).

2. DISTRIBUTION SUBSTATION A distribution substation is one whose main purpose is to transfer power room the transmission system to the distribution system of some area. It is uneconomical to directly connect electricity consumers to the main transmission network (unless they use large amounts of energy); so the distribution station reduces voltage to a value suitable for connection to local roads.

3. COLLECTOR SUBSTATION In distributed generation projects such as a wind farm, a collector substation may be required. It resembles a distribution substation although power flow is in the opposite direction, from many wind turbines up into the transmission grid. Usually for economy of construction the collector system operates around 35 KV, and the collector substation steps up voltage to a transmission voltage for the grid. The collector substation can also provide power factor correction if it is needed, metering and control of the wind farm. In some special cases a collector substation can also contain an HVDC converter station.

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4. CONVERTER SUBSTATIONS

Substations may be associated with HVDC converter plants, traction current, or interconnected non-synchronous networks. These stations contain power electronic devices to change the frequency of current, or else convert from alternating to direct current or the reverse. Formerly rotary converters changed frequency to interconnect two systems; such substations today are rare.

5. SWITCHING SUBSTATION A switching substation is a substation without transformers and operating only at a single voltage level. Switching substations are sometimes used as collector and distribution stations. Sometimes they are used for switching the current to back-up lines or for parallelizing circuits in case of failure.

CIRCUIT BREAKERS A 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 interrupt current flow. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. There are different types of circuit breakers which are:-1. LOW-VOLTAGE CIRCUIT BREAKERS

Low-voltage (less than 1,000 VAC) types are common in domestic, commercial and industrial application, and include Miniature Circuit Breaker (MCB) and Molded Case Circuit Breaker (MCCB).

2. MAGNETIC CIRCUIT BREAKERS Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with the current. Certain designs utilize electromagnetic forces in addition to those of the solenoid.

3. THERMAL MAGNETIC CIRCUIT BREAKERS

Thermal magnetic circuit breakers, which are the type found in most distribution boards, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. The thermal

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portion of the circuit breaker provides an "inverse time" response feature, which trips the circuit breaker sooner for larger over currents.

4. COMMON TRIP BREAKERS Three-pole common trip breaker for supplying a three-phase device. This breaker has a 2A rating. When supplying a branch circuit with more than one live conductor, each live conductor must be protected by a breaker pole. To ensure that all live conductors are interrupted when any pole trips, a "common trip" breaker must be used. These may either contain two or three tripping mechanisms within one case, or for small breakers, may externally tie the poles together via their operating handles.

5. VACUUM CIRCUIT BREAKERS With rated current up to 6,300 A, and higher for generator circuit breakers. These breakers interrupt the current by creating and extinguishing the arc in a vacuum container.

6. AIR CIRCUIT BREAKERS Rated current up to 6,300A and higher for generator circuit breakers. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Usually electronically controlled, though some models are microprocessor controlled via an integral electronic trip unit. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.

7. SULFUR HEXAFLUORIDE (SF 6) HIGH-VOLTAGE CIRCUIT BREAKERSA sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission-level voltages and may be incorporated into compact gas-insulated switchgear.

Isolator

In electrical engineering, a disconnector, disconnect switch or isolator switch is used to ensure that an electrical circuit is completely de-energized for service or maintenance. Such switches are often found in electrical distribution and industrial applications, where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow

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isolation of apparatus such as circuit breakers, transformers, and transmission lines, for maintenance. The disconnector is usually not intended for normal control of the circuit, but only for safety isolation. Disconnector can be operated either manually or automatically.

Lightning Arrestors

A lightning arrestor is a device used in power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.

Current Transformer

A current transformer (CT) is used for measurement of alternating electric currents. When current in a circuit is too high to apply directly to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry.

Potential Transformers

Voltage transformers (VT) (also called potential transformers (PT)) are a parallel connected type of instrument transformer, used for metering and protection in high-voltage circuits or phasor phase shift isolation. They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering. A potential transformer may have several secondary windings on the same core as a primary winding, for use in different metering or protection circuits. The primary may be connected phase to ground or phase to phase. The secondary is usually grounded on one terminal. There are three primary types of voltage transformers (VT): electromagnetic, capacitor, and optical. The electromagnetic voltage transformer is a wire-wound transformer. The capacitor voltage transformer uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic VT. An optical voltage transformer exploits the electrical properties of

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optical materials. measurement of high voltages is possible by the potential transformers.

Bus Coupler

Bus coupler is a device which is used to couple one bus to the other without any interruption in power supply and without creating hazardous arcs. It is achieved with the help of circuit breaker and isolators.

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5.3 EXPLANATIONTransformation may take place in several stages in sequence starting at the generation plant where the voltage increased for transmission purposes and is then progressively reduced to the voltage required for household or industrial use. The range of voltages in a power system varies from 110V up to 765kv depending on the country.

A substation that has a step-up transformer increase the voltage while decreasing the current while a step-down transformer decrease the voltage while increasing the current for domestic and commercial distribution. The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station where the generator was housed, and were subsidiaries of that power station.

Substation generally contain one or more transformers and have switching, protection and control equipment. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network. Smaller distribution stations may use Autoreclosures or even fuses for protection of branch circuits. Substations usually do not have generators, although a power plant may have a substation nearby. A typical substation will contain line termination structures, high voltage switchgear, one or more power transformers, row voltage switchgear, surge protection, controls and metering. Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation.

Substations may be on the surface in fenced enclosures, underground or located in special purpose buildings. Substations located within the building they serve are particularly a feature of high-rise buildings. Indoor substations are usually found in urban areas to reduce the noise from the transformers, and for reasons of appearance. Where a substation has a fence, it must be properly grounded (UK earthed) to protect people from high voltages that may occur during a fault in the transmission system. Earth faults at a substation can cause Earth Potential Rise at the fault location.

DESIGN The main issues facing a power engineer are reliability and cost. A good design attempts to strike a balance between these two to achieve sufficient reliability without excessive cost. The design should also allow easy expansion of the station if required. Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. Where land is costly, such as in urban areas, gas insulated switchgear may save money overall. The site must have room for expansion due to load growth or planned transmission additions. Environmental effects of the substation must be considered, such as drainage, noise and road traffic effects. A grounding (earthing)

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system must be designed. The total ground potential rise and the gradients in potential during a fault (called "touch" and "step" potentials), must be calculated to protect passers-by during short-circuit in the transmission system. The substation site must be reasonably central to the distribution area to be served. The site must be secure from intrusion by passers-by, both to protect people from injury by electric shock or arcs, and to protect the electrical system from misoperation due to vandalism.The first step in planning a substation layout is the preparation of a one-line diagram, which shows in simplified form the switching and protection arrangement required, as well as the incoming supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers and transformers) arranged on the page similarly to the way the apparatus would be laid out in the actual station.

LAYOUT What follows is a description of a substation.

In the largest stations, incoming lines will almost always have a disconnect Switch and a circuit breaker, some cases the lines will not have both ; with either a switch or a circuit breaker being all that is considered necessary. These devices are used as isolation and protection devices. A disconnect switch is almost always used solely to provide isolation, due to it not being rated for breaking a loaded circuit while a circuit breaker is often used both as an isolation element as well as protection device. Where a large fault current flows through the circuit break, this may be detected through the use of current transformers. The magnitude of the current transformers output may be used to trip the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point. This seeks to isolate the fault point from the rest of the system and allows the system to continue operating with minimal impact.

Once past the switching components, the lines of a given voltage all tie into a common bus. This is a number of thick metal bus bars; in most cases there are three bars, since three phase electrical power distribution is largely universal around the world.

Once past the switching components, the lines of a given voltage connect to one or more buses. These are sets of bus bars, usually in multiples of three, since three-phase electrical power distribution is largely universal around the world.

The arrangement of switches, circuit breakers and buses used affects the cost and reliability of the substation. For important substations a ring bus, double bus, or so-called "breaker and a half" setup can be used, so that the failure of any one circuit breaker does not interrupt power to other circuits, and so that parts of the substation may be de-energized for maintenance and repairs. Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations. Once having established buses for the various voltage levels, transformers may be connected between the voltage levels. These will again have a circuit

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breaker, much like transmission lines, in case a transformer has a fault (commonly called a "short circuit").

Along with this, a substation always has control circuitry needed to command the various circuit breakers to open in case of the failure of some component.

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6. AUTOMATIC POWER FACTOR

CONTROLLER

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6.1 INTRODUCTIONPower factor is the ratio between the KW (Kilo-Watts) and the KVA (Kilo-Volt Amperes) drawn by an electrical load where the KW is the actual load power and the KVA is the apparent load power. It is a measure of how effectively the current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.

BASIC PRICIPLE OF POWER FACTOR

a) RESISTO R

If a sinusoidal voltage source connected to a resistor, current will flow, power will be dissipated in the resistor and the resistor will heat up.

The current is given I=V/R and the power is given by P=I*V or P= V2/ R. The voltage and current are the rms (root mean square) values.

Fig. 1. Waveforms for resistive load

Figure 1 shows the waveforms for this experiment. The top blue waveform is sinusoidal voltage. The voltage is 1V rms giving a peak voltage of 1. 414V.

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Voltage

Current

Power

AC Source Resistor

Time Axis

Time Axis

Time Axis

The red waveform is the current. It is 1A rms, 1. 414 A peak.

The green waveform is the instantaneous power, i. e. the product of voltage and current from moment to moment. For example, at the left hand vertical line the voltage and current are both at their peaks, so the power is

1.414V * 1.414A= 2 watts

At the right hand vertical line it is at the negative peaks of voltage and current. Here the instantaneous power is

-1.414V * -1.414A= 2 watts

That is the product of two negatives gives a positive value. The average of the power waveform is 1W.

b) Inductor

Suppose now the resistor is replaced with an inductor with an inductance L henry. The current in an inductor lags exactly 90° behind the applied voltage. This is illustrated by the red current waveform in figure2. On close scrutiny at the instantaneous power waveform, it is observed that between the vertical lines a negative voltage is being multiplied by a positive current, giving a negative power.

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What the negative power means is that during that part of the cycle, energy is actually transferred from the inductor (load) back into the voltage source.

An inductor is an energy storage device. The energy stored in an inductor is 0.5 * I2 * L.

If the load is a perfect inductor, the negative power will exactly cancel the positive power, and net power dissipation is zero.

However, the voltage is still 1V and the current is still 1A, giving a product which is definitely not zero. Thus supposed 1W of input is not producing 1W of heat. This is commonly called "wattles watts". The correct term is Volt-Amps or VA. We say the circuit is drawing 1VA but consuming no power. The pure inductor dissipates no heat, so it has a power factor of zero.

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Voltage

Current

Power

900

Inductor

AC Source

Time Axis

Time Axis

Time Axis

Fig. 2. Waveforms for inductive load

c) Resistor and Inductor

Now an inductor and a resistor simultaneously are connected in parallel with each other.

The same voltage as before has been applied to both inductor and resistor. Hence, each one must be drawing the same current as before.

With the resistor drawing 1A in phase with the supply voltage and the inductor drawing 1A at a phase lagging the voltage by 90°.

The overall current (Fig-3) is the moment to moment summation of these two currents. It can be shown graphically or mathematically that the total current has a phase exactly half way between the two individual currents (i. e. lagging the voltage by 450) and a magnitude of 1. 414A

The input voltage is 1V and the current 1. 414A, so the input VA is 1. 414VA.

The power consumed is 1W, the same as in the resistor only. Hence, the power factor is 1W/1. 414VA = 0. 707. It is also the Cosine of the phase angle (Phi) between voltage and current.

Hence ‘the ratio between power and VA is power factor.

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Voltage

CurrentAC Source

Parallel Combination of Resistor &

Inductor

Power

Time

Time

Time

Fig. 3. Waveforms for both resistive and inductive load

Causes of Low Power Factor

Electrical equipments which need reactive power like inductor. Motors require reactive power during their operation to maintain magnetic fields. Non-linear loads distorts power factor.

Disadvantages of Low Power Factor

Inefficient use of Electrical Energy. Overloading of Transformer/Generator. Overloading of Cables, Switchgear, Busbar etc. Higher temperature due to increased losses. Imposes larger KVA demand. Reduces revenue to Electrical Utilities. Leads to poor voltage regulation.

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6.2 POWER FACTOR CORRECTION FOR LINEAR LOADS

From the above figure,

For the resultant current I1 from inductor, phase angle is δ.

For the resultant current I2 from inductor and capacitor, phase angle is β.

As,

δ > β

Cos δ < Cos β

So in the case of combined circuit of inductor and capacitor, power factor is greater than with respect to the power factor of and inductive circuit.

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βδ

I1

I2

I = Active Current

Reactive InductiveCurrent

Reactive Capacitive

Current V = Line Voltage

6.3 POWER FACTOR CORRECTION FOR NON-LINEAR LOADSA non-linear load on a power system is typically a rectifier (such as used in a power supply), or some kind of arc discharge device such as a fluorescent lamp, electric welding machine, or arc furnace. Because current in these systems is interrupted by a switching action, the current contains frequency components that are multiples of the power system frequency. Distortion power factor is a measure of how much the harmonic distortion of a load current decreases the average power transferred to the load.

Non-linear loads change the shape of the current waveform from a sine wave to some other form. Non-linear loads create harmonic currents in addition to the original (fundamental frequency) AC current. Filters consisting of linear capacitors and inductors can prevent harmonic currents from entering the supplying system.

In linear circuits having only sinusoidal currents and voltages of one frequency, the power factor arises only from the difference in phase between the current and voltage. This is "displacement power factor". The concept can be generalized to a total, distortion, or true power factor where the apparent power includes all harmonic components. This is of importance in practical power systems that contain non-linear loads such as rectifiers, some forms of electric lighting, electric arc furnaces, welding equipment, switched-mode power supplies and other devices.

Power factor correction in non-linear loads Passive PFC

The simplest way to control the harmonic current is to use a filter that passes current only at line frequency (50 or 60 Hz). This filter reduces the harmonic current, which means that the non-linear device now looks like a linear load. At this point the power factor can be brought to near unity, using capacitors or inductors as required. This filter requires large-value high-current inductors, however, which are bulky and expensive. A passive PFC requires an inductor larger than the inductor in an active PFC, but costs less. This is a simple way of correcting the nonlinearity of a load by using capacitor banks. It is not as effective as active PFC. One example of this is a valley-fill circuit.

Active PFC

An active power factor corrector (active PFC) is a power electronic system that changes the wave shape of current drawn by a load to improve the power factor. The purpose is to make the load circuitry that is power factor corrected appear purely resistive (apparent power equal

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to real power). In this case, the voltage and current are in phase and the reactive power consumption is zero. This enables the most efficient delivery of electrical power from the power company to the consumer. Some types of active PFC are:

o Boosto Bucko Buck-boost

Dynamic power factor correction

Dynamic power factor correction (DPFC) sometimes referred to as "real-time power factor correction," is used for electrical stabilization instances of rapid load changes. When electrical networks experience rapid load changes, especially with the presence of non-linear loads, standard power factor correction is unable to adjust with the constantly changing, i.e. dynamic, electrical network, causing over or under correction. DPFC has the ability with semiconductors to connect capacitors or inductors to electrical networks without disturbing the electrical network and causing unnecessary stress to electrical components, such as fuses and capacitors. Implementation of DPFC improves power quality by reducing current, especially reactive current, bringing stability to the electricity.

For companies, especially manufacturers, poor power quality leads to higher electrical bills due to power quality penalties. While PFC is available, few companies use it because PFC tends to be expensive without being cost effective. Today, DPFC devices range from sampling that takes place once per wave cycle (50 Hz/60 Hz) to over 8000 times per wave cycle.

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BENEFITS OF POWER FACTOR CORRECTION

Reduction in KVAR Demand. Reduction in KVA Demand Reduction in Line Current Avoid Power Factor penalties Reduction in Transformer Rating Reduction in Line loss Reduction in Switchgear rating Reduction in Cable / Bus – Bar Size

DISADVANTAGES OF FIXED CAPACITOR IN PFC

Manual operation(on/off) Not meet the require KVAr under varying loads. Can result leading power factor Cause over voltage Mal-operation of relays, diesel generators Saturation of transformer Penalty by electricity authority

NEED FOR AUTOMATIC POWER FACTOR CORRECTION (APFC)

Varying power demand on the supply system. Power factor also varies as a function of the load requirements. Difficult to maintain a consistent power factor by use of Fixed Compensation i.e. fixed

capacitors. Leading power factor under light load conditions (fixed compensation). No manual intervention is needed. As under leading power factor under light load conditions which results in over voltages,

saturation of transformers, mal-operation of diesel generating sets and penalties by electric supply authorities, APFC prevent leading power factor also.

6.4 AUTOMATIC POWER FACTOR CORRECTION (APFC)

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A Power-factor controller is the interface between the AC line and utility source that receives the Power Power-factor controller (PFC) act as reactive power generators, and provide the needed reactive power to accomplish KW of work. The basic function of a Power-factor controller (PFC) is to create a resistive load to the AC source. This implies that the input current must differ from the sinusoidal source voltage by only a scaling factor. Their waveforms must be identical, though scaled by the effective input resistance of the PFC, by Ohm's Law. How such a circuit can be incorporated in a substation supplying bulk power to various loads to be controlled so that its average per-cycle inductor current are controlled by a scaled input voltage (O, scaled by T,)? The resulting current (ig) would follow the voltage and the power source input would appear resistive, in other words, form a current control loop driven by the input sine wave. Because the loop would require a bipolar range to accommodate a sinusoid, incorporation of a bridge rectifier at the input is to be done. The rectified sine wave (or sine magnitude), Og is now uni-polar (assumed positive going with respect to PFC ground), but is not followed by a storage capacitor, That capacitor is, instead, placed at the output of the current-loop converter. This explained in diagram shown in Fig. 4.

As shown in Figure 4, power-factor controller (PFC) conceptual design provides no control over the output voltage. Coincidentally, it can vary for the sine magnitude input controlling the current, If the scale-factor is electronically adjusted using an analog multiplier, then it can be

implemented a second outer control loop to control the output voltage. This scheme consequently works like this. The outer voltage loop compares the storage-capacitor output voltage, scaled by a voltage divider, Hv, against the controlled voltage, set by a voltage

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TG.VG VCe ACeVCA PWM d TIGD

RSHE

TG.VGTG.VG

IG+

-

Σ

Fig. 4 Block Diagram of Power Factor Controller

reference. If too low, a voltage-loop error amplifier, Ave, increases its input to the multiplier. The other input is the sine magnitude voltage-divided first by a fixed divider, Tg, that is increased in amplitude. The multiplier output now is a larger sine magnitude controlling the current of the current control loop. This loop compares the controlled current to the sensed power source input current.

If the instantaneous value along the sine magnitude input-current is too low. The output of the current-loop error amplifier, Ace, to the pulse-width modulator (PWM) increases, and the PWM duty-ratio, D, increases. This causes the active converter switch to be on longer, increasing the inductor current. This current dumps into the storage capacitor and the output voltage increases. The voltage loop responds accordingly. To summarize, the inner current loop is actually a switching trans-conductance amplifier with scaled sine magnitude input. It is also a programmable-gain amplifier (PGA); with the gain controlled by a voltage control loop which adjusts average output current i to maintain output voltage OO. The block diagram of the entire APFC is shown in Figure 5.

Two blocks (transfer functions), the duty-ratio (or control) to source current T IGD, and the source current iG to output current iO or TIGO, represent the converter. Figure 5 also shows the effect of the input voltage, OG on the power source, in that T IGD is a function of OG. Current-and voltage-loop error (and dynamic compensation) amplifiers have gains of ACE and AVE. Respectively. RS is

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V2

TG π Σ ACe

HC

PWM

RD

TIGI TIGO ZO

V2V2AVeVVeVva

VC

-

+

IO/IGIG/DTC

vca d ig iox

x

/+

-

VO

Fig. 4 Block Diagram of Automatic Power Factor Controller

the sense resistor (or equivalent) and He is the current-loop sampling effect. HV is the output voltage divider and ZO Is the storage capacitor and load-the next stage-of the power source. TC

is the transfer function of the closed current loop:

TC=IG/TG*VG

The feed-forward path above TG drives the divider input of the multiplier. As the line voltage varies, the peak-to-average ratio (π/2 is approximately equal to 1.57) remains constant. Consequently, dividing by the average can compensate this variation. The amplitude is thus normalized to a constant value.

Advantage & Cost Benefits of PF Improvement

Automatic Power-factor controller (APFC) act as reactive power generators and provide the needed reactive power to accomplish k W of work. This reduces the amount of reactive power, and thus total power, required by the utilities. The reduction in total power reduces the money required for the energy needed to run the organization.

6.5 USE OF APFC IN ONGC COMPLEX

Uttaranchal power corporation Ltd (UPCL) is the power supplying authority for ONGC's installations in Dehradun. Electricity tariffs of UPCL were structured in a relatively simple

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manner. High tension (HT) consumers were charged based on both demand (k VA) and energy (kWh).

UPCL impose surcharges to the bulk costumers for not maintaining the Power factor equal to 0. 85. The surcharges are 10.0% over the total bill if Power factor is below 0.8 and 5.0% if the Power factor is below 0.85.

So in August-September 2005, commissioning of APFC was done at the 33KV sub-station of the ONGC institute.

The key reasons and steps for the installation of APFC are:-

ONGC have with 4 * 1600 KVA transformers installed in the institute in an event of the power failure from UPCL side. The demand of the institute complex is 4* 1000 KVA.So the percentage loading of transformers is 63% ((1000/1600)*100).

The power factor of institute before APFC installation was 0.79 which leads to the penalty charge of 10%.

So to improve the Power factor and to avoid the surcharge, the substation has to add KVAr through the APFC, the sanction for installation and commissioning of Automatic Power-factor controller (APFC) was given by appropriate authorities.

The improved Power factor was aimed at 0.95. KVAr rating required to achieve this Power factor is,

KVAr = kW * [Tan {existing (Cos-1 PF)} – Tan {improved (Cos-1PF)}] Now putting the values in above KVAr=4*1000 * 0. 79 * [Tan {existing (Cos-10. 79)} - Tan {improved (Cos-10. 95)}]KVAr= 1413.8 KVAr.

This KVAr was then supplied by the APFC. Initially total KW demand of institution is 4 * 1000 * 0.79 = 3160.

With a new power factor of 0.95, total KVA now needed from the UPCL were New KVA = 3160 / (4 * .95) = 831.6 KVA

After the implementation of the provision of APFC, the institute will save charges towards k VA demand and surcharges @ 10% (which was approx. Rs, 3.0 lakhs per month).

Also now transformers were loaded with only 52% of the capacity. The enabled the institute to earn bonus from UPCL and have cushion for addition of

more load in the future to be supplied by these transformers resulting in Energy Efficiency in electrical system.

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6.6 APFC WORKING

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APFC unit installed in ONGC Service Block

In APFC, Capacitors grouped into several steps. Suitable switching devices with coupled with inrush current limiting devices are

provided for each step Power Factor is sensed by Current Transformer(CT) & Potential Transformer(PT) in line

side KVAr required to achieve target PF is computed by the Microprocessor based APFC relay APFC relay switches appropriate capacitor steps CT and PT senses improved PF and gives feedback Thus target Power Factor is achieved.

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1. Reactive Power Control Relay2. Network connection Points3. Slow Blow Fuses4. Inrush Current Contractors5. Capacitors6. Transformers

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Specification of capacitors in APFC:-

1. KVAr2. Degree Of Protection IP203. Ambient temperature4. Voltage rise should be≤ 3.0% [% Voltage rise = (KVAr * %X)/(KVA)]5. Voltage rise due to series reactor and harmonics6. Size of individual capacitor banks (step requirement).7. Directly connected Discharge Device (Resistor, VT) to discharge the capacitor to reduce

voltage to 50 volts within one minute.

Selection of Switching Equipments

For Low Tension (LT) 1. Switch-fuse units/Circuit Breakers/ Thyristors.2. Switch should be quick make and break type3. Rating of CB, contactors, fuse and cable should be ≥ 130% of capacitor rated

current.4. For automatic switching, each step capacitor should be provided with fuse and

contactor.

For High Tension (HT) 1. HT capacitor is connected to bus by Circuit Breaker.2. Circuit Breaker rating should be ≥ maximum operating voltage of circuit3. Continuous current rating of CB should be ≥ 135% of rated capacitor bank

current

PFC improvement without Harmonics problem

The harmonics are caused by many nonlinear loads; the most common in the industrial market today, are the variable speed controllers and switch mode power supplies. Harmonics on the supply cause a higher current to flow in the capacitors. This is because the impedance of the capacitors goes down as the frequency goes up. This increase in current flow through the capacitor will result in additional heating of the capacitor and reduce its life.

Due to this reason conventional capacitors are not used alone to correct the power factor in APFC. For this, Detuning reactors are connected in series with power factor correction capacitors to reduce harmonic currents and to ensure that the series resonant frequency does not occur at a harmonic of the supply frequency. The reactors are usually chosen and rated as either 5% or 7% reactors. This means that at the line frequency, the capacitive reactance is

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reduced by 5% or 7%. Using detuning reactors results in lower impedance, increasing the current, so the capacitance will need to be reduced for the same level of correction. When detuning reactors are used in installations with high harmonic voltages, there can be a high resultant voltage across the capacitors. This necessitates the use of capacitors that are designed to operate at a high sustained voltage. Capacitors designed for use at line voltage only, should not be used with detuning reactors. The detuning reactors can dissipate a lot of heat. The enclosure must be well ventilated, typically forced air cooled. With the use of detuning reactors, APFC:-

It offers capacitive reactance at fundamental frequency for necessary power factor correction.

It offers inductive reactance at all higher order dominant harmonic frequencies to avoid resonance.

Its self-series resonance frequency “fR” do not coincide with predominant harmonics.

Benefits of APFC Consistently high power factor under fluctuating loads. Prevention of leading power factor Eliminate power factor penalty Lower energy consumption by reducing losses. Continuously sense and monitor load Automatically switch on/off relevant capacitors steps for consistent power factor. Ensures easy user interface Protect under any internal fault User friendly, aesthetically designed enclosure, dust and vermin proof.

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Combination of Detuning Reactor and Capacitors

7. SPECIFICATION FOR AUTOMATIC POWER FACTOR CONTROL

PANELS WITH LT CAPACITORS

Scope and ApplicationThis Specification covers the minimum requirements and guidelines for Automatic Power Factor Control Panels with LT Capacitors for application in Production Installations, colonies. Work Shops, and Sub-Stations etc. for improvement of Power Factor, where average P. F. Is low or where there is a statutory requirement of State Electricity Boards.

General Requirements

Adequate lifting facilities shall be provided. The panels should be made out of best quality materials ; designed and manufactured in

conformance with relevant Indian/international Standards, The information as per attached Data Sheet at Annexure-XXX shall be furnished

completely by the vendors/ manufacturers and submitted along with the tender document.

The APFC panels shall be suitable for installation as specified, and shall be capable of withstanding normal stresses experienced during transportation, erection and commissioning.

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Technical Features: (General Technical Requirements) Sl No. Parameter Value3.0.1 Material Panel shall be fabricated with 14 SWG cold rolled

Sheets steel.3.0.2 Panel Doors Panel shall be compartmentalized with all doors

in front only.3.0.3 Panel Contactors The contactors used in the control panel shall be

Suitable for capacitor Switching.3.0.4 Robustness Should withstand vibration; normal Stresses

experienced during transportation, erection andcommissioning ; and shall have high corrosionresistance to polluted atmospheres andchemicals.

3.0.5 Duty Shall be manufactured for Continuous Duty.

Codes & StandardsUnless otherwise specified elsewhere in this specification, the rating as well as performance and testing of Automatic Power Factor Control Panels with LT Capacitors shall confirm to the latest revisions of all the relevant standards available at the time of placement of order, as listed in, but not item/equipment shall be designed. The item/equipment shall be designed, constructed and tested as per relevant Codes & Standards/Standard as per suitable for the intended service. All applicable latest editions/ versions of Indian/International Standards are part of this specification. In case of conflict; specifications and related standards shall take precedence in the order.

Sl. No. Standard Title3.1.1 IS 13340:1993/ IEC

60831-1Power Capacitors of Self-healing Type for AC Power Systems having Rated Voltage up to 1000 V-Specification

3.1.2 IS 13341:1992 / IEC 60831-2

Requirements for ageing test, self-healing test and destruction test on shunt capacitor of the self-healing type for AC power Systems having a rated voltage up to and Including 1000 V.

3.1.3 IEC 61921 Power Capacitors – Low voltage power factor correction banks

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Technical Parameters: (Specified)Sl. No. Parameter Value1 Rated Operational Voltage 415V (+/- 10%)2 No. of Phases 33 Frequency of system 50 Hz (+/- 3%)4 KVAR rating of panel 400 KVAr5 Capacitor total losses < .5 W/KVAr6 Type of duty Continuous7 Ambient temperature 0 to 500 C8 Type of capacitors Self-Healing Type confirming

to IS 13340, 13341 IEC 60831 -1 & 2

9 Enclosure Protection IP 4210 Installation Indoor11 Mounting Wall/ Floor Mounted12 Cable entry Top / Bottom13 Lifting Lifting Lugs required14 Safety Features Door Interlock/ Protection

Against

Automatic Power Factor Control Panel shall be rated for continuous duty, having the following:

Main incoming control shall be with 3 phase MCCB, Copper bus bar, Current Transformer for Protection system, Ammeter and Voltmeter with Selector Switch, Power Factor Meter, Earth Leakage Relay having Auto Manual Switch, Timer 0-60 sec with Relay, Voltage rating of relay (exact operating voltage of the installation to be given by indenter i. e. 400, 415, 440 V)

Outgoing controls: On-Off Push Button Switches, HRC fuses with fuse grips, Indication for Capacitor "ON", Hooter for Power Factor going out of range/limit (optional).

Special Features: Power Failure Cut-off-when supply voltage of installation falls below 109 & of rated voltage. When power restores-all capacitors are to be switched within one minute, in sequence with proper timing according to the power factor requirement. Time gap between two successive capacitor switching on shall be between 4 to 8 seconds. Indication of number of capacitors online and Indicating light / alarm in case the power factor goes below limit shall also be provided.

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Constructional Features1. Capacitors shall be shock proof, rust proof, water proof, leak proof and dust proof, 2. Features of capacitor: nonmetallic container or sheet steel with earthing provision, Self-

healing, Self protected and hermetically sealed. 3. Earthing terminals, lifting hooks and a separate rack for capacitors to be provided. 4. Compartment doors shall open away from the cable alley and shall be provided with

special locks which will ensure tight closing of doors making the compartment effectively dustproof.

5. All equipment inside the compartment shall be arranged in a logical manner for ease of maintenance at site.

6. Indicating On-Off lamps shall be provided on each capacitor rack. 7. Control wiring shall be provided with ferrule numbers and the terminal blocks shall be

numbered for ease of connection. 8. Control Supply shall be tapped after the mains incomer, 9. MCCB control circuit shall have protection Fuses/MCBs. 10. Fabricated panel shall undergo a treatment of degreasing, picking and two coats of

primer before providing inner and outer coating of paint. 11. Panel shall be provided with cooling fan for controlling the excessive temperature rise. 12. HRC Fuses shall be of DIN type. 13. Contactor shall be of reputed make Such as L & T. Siemens and Crompton Greaves etc. 14. CTs shall be of cast resin/tape wound type and shall be capable of withstanding rated

fault current of the system for 1 (one) second. 15. Incoming circuit breaker shall be of suitable size of MCCB/HRC fuse and of reputed make

such as L & T, Siemens and Crompton Greaves etc.16. Capacitor units used in the panel shall be as per IS 13340: 1993/IEC 60831-1. 17. Panel shall be meticulously wired and tested and shall be complete with all essential

auxiliaries like Voltmeter, Ammeter etc. 18. Cable entries shall be provided at top/bottom. 19. Cabinet shall be color powder coated to provide an aesthetic look.

MaterialVendor to ensure that material of construction of offered panel and all its constituent components shall compatible with specified operating conditions and parameters ; and shall be suitable for the intended service, except as required by the data sheet/indenter or the relevant codes and standards.

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Annexure – XXX

Capacitor Name Plate/ Marking Detail1. Manufacture's Name/Trade Mark2. Serial Number3. Rated Output in KVAIT4. Rated Voltage5. Rated Frequency6. Upper Limit of Temp7. Category8. Number of Phases9. Discharge Devices10. Insulation Level11. Total Weight12. Type of Dielectric13. Type of lmpregnant14. Connection Symbol15. ISI marking & Number

Panel1. Manufacturers Name/Trade Mark 2. Serial Number 3. Rated Output in KVAR 4. Rated Voltage 5. Rated Frequency 6. Power Factor Range 7. Dimensions 8. Weight

WarningWarning instruction that "Capacitors must be discharge before handling" shall be prominently marked in red color.

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INSPECTION AND TESTING

Inspection shall be carried out in conformity with the ordered Specifications IS 13340: 1993/ IEC 60831-1; is 13341: 1992/IEC 60831- 2; IEC 61921 and other relevant standards.

Test on Capacitor Units

Routine Test1. Visual examination 2. Sealing test. 3. Measurements of capacitance and output. 4. Insulation resistance between terminals and capacitor container. 5. Capacitor loss tangent (tan delta) measurement. 6. AC voltage test between terminals. 7. AC voltage test between terminal and container. 8. Test for discharge devices.

Type Tests1. Voltage test between terminals. 2. Voltage test between terminals and container. 3. Thermal stability test. 4. Capacitor loss tangent (tan delta) measurements at elevated temperature. 5. Self-healing test. 6. Test for capacitance and output. 7. Capacitor loss tangent measurement, 8. Lightening impulse voltage test between terminals and container. 9. Short circuit discharge test.

Acceptance Test1. Visual examination. 2. Test for capacitance and output. 3. Capacitor loss tangent (tan delta) measurement. 4. Insulation resistance.5. AC voltage test between terminals. 6. AC voltage tests between terminals and container. 7. Test for discharge device. 8. Sealing test.

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Test on Capacitor Banks

Routine Tests1. Measurements of capacitance and output. 2. Insulation resistance between terminals and capacitor container.

Acceptance Test1. Test for capacitance and output. 2. Insulation resistance.

Special Test1. Ageing Test2. Destruction Test

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7. CONCLUSION

Maintaining Power Factor near to unity in high tension (HT) Substation connected by state electricity corporation is very much relevant where Power factor penalty or bonus rates, as levied by state electricity, are to contain reactive power drawl from grid. By incorporating Automatic Power-factor controller (APFC) in the system, reactive component of the network is reduced and so also the total current in the system from the source end. Voltage level at the load end is increased. k VA loading on the source generators as also on the transformers and lines up to the APFC reduces giving capacity relief. A high Power factor can help in utilizing the full capacity of electrical system. Improved Power factor will earn bonus instead of surcharges from state electricity and allow the addition of more load in the future to be supplied by the Substation, resulting in Energy Efficiency in electrical system.

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8. BIBIOGRAPHY1. Energy efficiency in electrical utilities, Guide book for National certification examination for energy managers and energy auditors, Bureau of energy efficiency, Ministry of Power, Govt. of India, 2003.

2. General aspect of energy management and energy audit, Guide book for National certification examination for energy managers and energy auditors, Bureau of energy efficiency, Ministry of Power, Govt. of India, 2003.

3. www.wikepedia.com

4. www.slideshare.com

5. www.electrical-installation.org

6. www.home-energy-metering.com

7. www.enspecpower.com

8. www.allaboutcircuits.com

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