Electrical Design and Estimation

30Electrical Design Estimation & Costing 10EESI VIII Semester lOEE81: ELECTRICAL DESIGN ESTIMATION AND COSTING I SUBJECT CODE lOEESl No. of Lecture Hrs.lWeek 04 Total No, of Lecture Hrs. 52 IA Marks Exam Hours' Exam Marks 25 03 100 PART-A _' UNIT -1 GENERAL PRINCIPLES OF ESTIMATION: Introduction to estimation & costing,. Electrical Schedule, Catalogues, Market Survey and source' selection, Recording of estimates, Determination of required quantity of material, Labor conditions, Determination of cost material and labour, Contingencies, Overhead charges, Profit, Purchase system, Purchase enquiry and selection of appropriate purchase mode, Comparative statement, Purchase orders; Payment of bills, Tender form, General idea about IE rule, I~di~n Electricity Act and major appiic~bi~ I.E rules. 6Hours UNIT - 2 RESIDENTIAL BUILDING ELECTRIFICATION: General rules guidelines for wiring of residential installation and .positioningof equipment's, Principles of circuit design in lighting and power circuits, Procedures for designing the circuits and deciding the number of circuits, Method of drawing single line diagram, Selection of type of wiring and rating of wires and cables, Load calculations and selection of size of conductor, Selection of rating of main switch, distribution board, protective switchgear ELCB and MCB and wiring accessories, Earthing of residential Installation, Sequence to be followed for preparing estimate, Preparation of detailed estimates and costing of residential installation. 7Hours UNIT -3 ELECTRIFICATION OF COMMERCIAL INSTALLATION: Concept' of commercial installation, Differentiate between electrification of residential and commercial installation, Fundamental considerations for planning of an electrical installation system for commercial building, Design considerations of electrical installation system for commercial building, Load Dept of EEE, SJBIT Page 1 Electrical Design Estimation & Costing lOEE8t calculation and selection of size of service connection and nature of supply, Deciding the size of the cables, busbar switchboards, and bus bar chambers, distribution Mounting arrangements boards main .switch etc, .Earthing and positioning of the electrical of installation, Selection of type wire, wiring system and layout, Sequence to be followed to prepare estimate, Preparation of detailed estimate and costing of commercial installation. 7Hours UNIT -4 SERVICE CONNECTION, INSPECTION Concept of service connection, AND TESTING OF INSTALLATION: Types of service connection and their features, Method of l installation of service connection, Estimates of underground and overhead service connections, Inspection of internal wiring installations, Inspection of new installations, testing of installations, Testing of wiring installations,· Reason for excess recording of energy consumption by energy meter. . 6Hours PART-B UNIT-5 ELECTRICAL INSTALLATION FOR· POWER CIRCUITS: Introduction, Important considerations regarding motor installation wiring, Determination of input power, Determination of input current to motors, Determination of rating of cables, determination of rating of fuse, Determination of size of Condit, distribution Board main switch and starter. 6Hours UNIT-6&7 DESIGN AND ESTIMATION OF OVERHEAD TRANSMISSION· & DISTRIBUTION LINES: Introduction, Typical AC electrical power system, Main components of overhead lines, Line supports, Factors governing height of pole, Conductor materials, Determination of size of conductor for overhead transmission line, Cross arms, Pole brackets and clamps, Guys and Stays, Conductors configuration spacing and clearances, Span lengths, Overhead line insulators, Insulator materials, Types of insulators, Lightning Arrestors, Phase plates, DaI?-gerplates, Anti climbing devices, Bird guards, Beads of jumpers, Muffs, Points to be considered at the time of . erection of overhead lines, Erection of supports, Setting of stays, Fixing of cross arms, Fixing of insulators, Positioning Conductor erection, of conductors Dept ofEEE, SJBIT Repairing and attachment and jointing of conductor to insulators, Jumpers, , Dead end clamps, Tee-offs, Earthing of Page 2 Electrical Design Estimation & Costing lOEE81 transmission lines, Guarding of overhead lines, Clearances of conductor from ground, Spacing between conductors, Testing and commissioning of overhead distribution lines, Some important specifications. 12Hours UNIT: 8 DESIGN AND ESTIMATION OF. SUBSTATIONS: Introduction, Classification of substation, Indoor substations, Outdoor substations, Selection and location of site for substation, Main Electrical Connections Graphical symbols for various types of apparatus and circuit • elements on substation main connection diagram, Key diagram of typical substations, Equipment for substation and switchgear installations, Substation auxiliaries supply, Substation Earthing 6Hours TEXTBOOK: 1. Electrical Installation Estimating & Costing, J.B.Gupta, VIII Edition S.K. Katria &" Sons New Delhi REFERENCE BOOKS: 1. Electrical Design Estimating and Costing, K.B.Raina S.K.Bhattacharya, New Age International 2. Electrical Wiring Estimating and Costing, Uppal, Khanna Publishers Delhi 3. I.E,Rules and Act Manuals -, Dept of EEE, SJBIT Page 3 Electrical Design Estimation & Costing lOEESt INDEX SI.no Contents Page no " • " GENERAL" PRINCIPLES Introduction to estimation OF & ESTIMATION: costing, Electrical Schedule, Catalogues • Market Survey and source selection, Recording of estimates, • Determination of required quantity of material, Labor conditions Unit 1 • , Determination of cost material and labour, .. 7-16 Contingencies, Overhead charges• . . ". • Profit, Purchase system, purchase enquiry and selection . " " . " " of appropriate purchase "mode;Comparative statement, Purchase orders, • Payment of bills, Tender form, General idea about IE rule, Indian Electricity Act and major applicable I.E rules. • DESIGN AND ESTIMATION OF SUBSTATIONS: Introduction • Classification of substation, Indoor substations Outdoor substations • Unit 2 Electrical Connections • ... Selection and location of site for substation, Main 17-34 Graphical symbols for various types of apparatus and circuit elements Dept of EEE, SJBIT .. • Key diagram of typical substations • Equipment for substation and switchgear installations • Page 4 Electrical Design Estimation & Costing • lOEESt Substation auxiliaries supply, Substation Earthing ELECTRICAL INSTALLATION FOR POWER .. CIRCUITS: Introduction • Important considerations regarding motor. installation wiring Unit-3 • Determination of input power, Determination of input current to motors, i ....- 40-54 • Determination of rating of cables, • determination of rating of fuse • Determination of size of Condit, distribution Board main switch and starter SERVICE CONNECTIQN, INSPECTION TESTING OF INSTALLATION: .. • Concept of s'ervice: connection, . . , AND -.-_ Types of service .. .' . connection and their features UNIT-4 • Method of installation of service connection, Estimates of underground and overhead service connections • Inspection of internal wiring installations, Inspection of new installations, testing of installations • • • . Dept ofEEE, SJBIT 55-60 Testing of wiring installations, Reason for excess recording of energy consumption by energy meter. . Page 5 This tool is designed for use by electricians.Electrical Design Estimation & Costing 10EE81 UNIT -1 . lik~ an offer from one mechanic in a shop of a very low price for service while another indicates the cost of a job will be much higher. Determination of cost material and labour. Profit. For people soliciting estimates. Catalogues . Purchase system. Market Survey and source selection. Comparative statement. Indian Electricity Act and major applicable I. and quick research. Contingencies. Overhead charges.:. Payment of bills. architects and electrical engineers. When preparing estimates.E rules. Determination of required quantity of material. This can help reduce problems associated with variances in methodology. They can be helpful for getting a general idea of expenses before proceeding with a more detailed estimate.:accurate electrical. Both methods have value. Tender form. people can broadly divide them into detailed and approximate types. commercial or prototype development. General idea about IE rule. Purchase enquiry and selection of appropriate purchase mode. Introduction to estimation and costjng Electrical estimating is a process used by electricians. Labor conditions . An estimating technique is an approach to predicting cost or revenue.:. Purchase orders • •:. Electrical Schedule. Electrical estimating computer software has increased in popularity as it has improved in quality and performance.: . but Dept of EEE. they can't be quoted as firm bids. GENERAL PRINCIPLES OF ESTIMATION: Introduction to estimation & costing. Using a consistent methodology is important to achieve reliable and comparable results. SJBIT Page 6 • . experience. Recording of estimates. construction managers and engineers to determine the amount and cost ofelectricity required for a specific location or process.:. Approximate estimates offer a rough guess of the cost. There are two general methods of crea~ing. based on similar projects. There are different versions available for residential. Firms may have specific policies their personnel have to follow when making estimates to ensure that the approach will be similar no matter who prepares the estimate. benefits and risks.computer software or manual calculations. esti~ates. Original electrical estimating software options were quite clumsy to use. but recent enhancements have vastly improved this tool for electrical estimation. in tum. but have to be reviewed continually to keep them current. . This. and the public. reviewing all project' cost estimates and ensuring that . Electrical Schedule: The electrical load schedule is an estimate of the instantaneous electrical loads operating in a facility. also includes the costs for 'the purchase of right of way.estimators are expected to preparereasonable project cost estimates that represent the cost to complete the project. A homeowner looking for a new roof.' other agencies. in terms of active. and planning.:These costs include those required not only for the contractor to construct. Cost Estimates are Not Static Cost estimates.thoroughly compiled by diligently using all of the available data. SJBIT Page 7 . the Project Manager (PM) is responsible for keeping the project cost estimate up-to-date throughout the project development process. in a sense. for example. and ultimately results in loss of credibility.. modifying that data with good' judgment and using past cost' estimating experience so that the cost estimates can be used with confidence. kVAR' and kVA respectively). Project alternatives and their associated cost estimates must be. • .Electrical Design Estimation & Costing 10EE81 may provide a frame of reference. and the specifications and policies that will be in place during the construction of the project is required. They are not static.the current project cost estimates are entered into the Project Management data base and a hard copy is in the project file. budgeting. however. affects Engineering Services relations with the other divisions within Public Works & Utilities. Coordination between the project planning cost estimates. the project but. Prepare Reasonable Cost Estimates Project cost estimating is not an exact science. Unreliable cost estimates result in severe problems in programming. could ask for an approximate estimate from several contractors to learn more about the range of possible prices. are never completed. reactive and apparent power (measured in kW. Dept of EEE. The load schedule is usually categorised by switchboard or occasionally by subfacility / area. mitigation of environmental issu~~and any other costs that will be incurred to'complete the project. the project design cost estimates. Importance of Quality Cost Estimates The reliability of project cost estimates at every stage in the project development process is necessary for responsible fiscal management. whether commercial practices regaiding customizing. Various locational difficulties are described: 1. what are the customary terms and conditions. acquisition decisions. A catalogue layout properly designed must show your company's products or services arranged neatly. Confined sites 3.Electrical Design Estimation & Costing 10EE81 . Marret research informatio~ can be used to shape the ac~uisition strategy. so that they can be easily recognized. . In addition.isuppliers' . at the same time. the terms and conditions included in the contract. to determine the type and content of the product description or statement of work. it may inform the audience about the new comfort and convenience of a service or it can simply contain small businesses' month offers. buyer financing. capabilities. attractive to improve your sales. and the business practices that . it must look . modifying products or tailoring services are available to meet customer needs. SJBIT '4 Page 8 • . Finally. A catalogue may promote products within promotional packages or lithe known products. and. . . and discounts under which commercial sales are made. including warranty.. This requires one to collect and analyze information about the market ·th&( subsequently can be used to determine whether the need can be met by products or services available in the commercial market. Labor availability 4. to develop the support strategy. the visual coherence on which a company's corporate Image is supported ~~st be kept. Remoteness 2. and whether the distribution and logistics support capabilities of potential suppliers are sufficient to meet the needs of the government.of that data to make . Weather Dept of EEE. the catalogue layout must be strategically arranged ( in order to give more importance to certain items or to make the catalogue look more eyecatching.surround them-plus the analysis. Catalogues: The main objective of a catalogue is to promote the products and services offered by your company. and the evaluation factors used for source selection. Market Survey and source selection: Market research is a continuous process for"gathering data on product characteristics. A telephone is a requisite to any construction project: lack of communication during the construction process can result in major.. It may be necessary for the contractor to widen the existing route or construct a bridge to allow material trailers access into the job site.additional long-distance . because the project location is further away from the head office.. whose replacements costs must be borne by the contractor. costly errors. poses a contracting organization with a difficult set of problems to cope with. the requirement. Given these considerations. . Transportation Problems All material and labor must be transported to the building site. for example. Design considerations (related to location). Dept of EEE. In adJition. . SJBIT Page 9 . any route exists at all). If the transport route is poor (if. then a radio or cellular-type installation is required. Communication Problems • If adequate communications such as telephone are not available. Finally. indeed. then delays in material deliveries may occur. The route that is proposed should be studied carefully by the estimator.-' _" correct equipment selections becomes very important. the cost of hauling items of equipment to the job site increases as the distance increases. 6.for management to make the .Electrical Design Estimation & Costing lOEE81 5.telephone charges will be incurred. a project site located high in the Blue Ridge Mountains of Virginia. Vandalism and site security Remoteness A remote construction site. large vehicles may damage narrow bridges or other items of property. Existing capacity of existing bridges on route shouldbe established to verify if equipment loads can be accommodated of if the bridge needs to be strengthened by the contractor. Q it is fairly easy to price an electrical job and develop an appropriate estimate.Electrical Design Estimation & Costing 10EE81 Profit: Estimating the cost of labor for electrical construction can vary greatly from project to project. SJBIT Page 10 . complete required paperwork and execute the final contract. The niles vary depending on the dollar value of the transaction. to product receipt. J] . depending on the installation crew's experience and the complexity of the project. to payment. from requisition. Electrical contractors are responsible for installing. but the principles should be employed whenever funds are to be used. Charging an hourly installation rate is common for electrical contractors until installatidn data (number of hours per installer for job completion) can be collected and projects can be pstimated based on the amount of work. Fortunately. Purchase enquiry and selection of appropriate purchase mode: Guidelines on purchasing practices: These practices are used by Purchasing to promote competition and ensure that all purchases comply with the standard Requirements. most companies will focus solely on either residential or commercial work. the process of pricing an electrical job is similar no matter what type of building is involved. repairing. Purchase System: A method used by businesses to buy products and/or services. For those with a basic understanding of construction and electricity. Purchasing is available to perform the due diligence. Due to the differences in skills and costs between home systems and. how much to buy and when to buy it. A popular purchasing system is based on economic order quantity models. and mainta~ningelectrical systems in homes and commercial buildings. commercial systems. • . Purchasing systems are a key component of effective inventory management in that they monitor existing stock and help companies determine what to buy. A purchasing system manages the entire acquisition process. WORKING TOGETHER IN THREE WAYS 1. to purchase order. Dept of EEE. Purchasing will execute the final contract. • Investigate a supplier's financial stability. Our customers may work independently to source their needs and select their supplier in accordance with university policy. 3. There are a number of tools available for this initial phase 2. There are a number.Electrical Design Estimation & Costing lOEE8t 2. begin evaluating each supplier's capabilities. particularly if the product or service has not been purchased before. If you choose to select the supplier and obtain quotes without assistance from Purchasing. SJBIT Page 11 1 . with prior assurance that all university policies have been adhered to. The first step in selecting suppliers is often research.of guidelinesfor supplier selection • Find out how long the supplier has been in business. SELECTING QUALIFIED SUPPLIERS: Supplier selection and evaluation is a process that can. The following guidelines are included primarily to give our customers a better understanding of the process and to better facilitate communication and collaboration. Dept of EEE. take considerable time and energy depending on the product or service. However.' Strategic Partners are pre-qualified and choosing to . selecting suppliers and preparing and evaluatio~ of bids. 1. • Find out who are the supplier's primary customers and ask for and check references. 3. ' use one will eliminate the time' consuming processes of due diligence. Obtaining a Dun & Bradstreet financial report ('running a D&B') is a good place to start. on specialty projects or complex needs. . this section should serve as a guide or checklist. Purchasing is available to work in collaboration with our customers on large projects. a D&B contains only publicly available information or information that the supplier chooses to provide. When a Strategic Partner exists for the commodity or service being sought it is important and • • Q Purchasing strongly recommends their use. Some D&Bs also: include brief profiles of key management personnel and historical information on the company. Once a list of potential suppliers has been developed. . drawing on our customers experience while adding purchasing value. Another option is to check with local Better Business Bureaus. License: Grant of licenses. These steps should narrow the field to the three suppliprs (sometimes more) who will be asked to bid on the particular product or service. annual accounts of licenses.. 1910 This is an act relating to amend the law relating to the supply and use of electrical energy.• Tour the supplier's facilities. and suppliers may be c0l?-~ultedfor assistance in developing specifications.Electrical Design Estimation & Costing 10EE81 • Check bank references. 2. purchase of under takings. and service . The Contract Administrator (CA) in conjunction with the requester must define the requirements exactly. notice of new works. • provides access to University business for suppliers. PREPARING AND EVALUATING A BID Bidding goods and services is important for several reasons.: • provides a list of qualified suppliers for future bids>' . if possible. over head lines compensation for damage Dept of EEE. The requirements are then communicated to the selected suppliers by a Request for Quotation (RFQ) or a Request for Proposal (RFP). trade manuals. notice of telegraphic authority.provides a standard for comparing price. Colleagues. lying of supply lines. technical personnel.• Is the supplier really interested in doing business with the University? • Does the supplier use state-of-the art technology? • Does the supplier offer an educational discount? 4. railways and tramways. It regulate 1. : The bid process begins with the development of a set of specifications or objectives. quality. Works: provision has to the opening and breaking up Of streets. revocation or amendment of licenses. SJBIT Page 12 . The Indian electricity act. The bidding process: • allows "comparison shopping" for the best pricing and service Q • allows for an informed and objective choice among potential suppliers • encourages competition among suppliers. The electricity (supply) Act 1948: This act rationalizes the production and supply of electricity and generally provides for taking measures conductive to its development. statics and returns.. prohibition of connections with earth and• power for government to interfere in certain cases of default.1: C·riminal offences and procedure: Theft of energy penalty for maliciously wastiiig ~nergy or 'injuring works. • State electricity boards: Transmission companies generating companies. Transmission and use of energy by non licensees: Sanctions required by non licensees in certain cases. canals.. SJBIT Page 13 . Disconnection of supply . penalty for interference with meters or licensees works -and for improper use of energy .electric signal lines. • 5. powers of licensee to enter premises. constitution and composition of state electricity boards. protection of telegraphic and..aerodrums. penaltyfor illegal or defective supply or non-compliance with order..offences by compliance. • Q 6. powers of authority to make regulations. institution of prosecution.. . Power of central government to make rules.Electrical Design Estimation & Costing lOEE8t 3.. docks and piers. direction of central government to the authority.. penalty for unauthorized supply of energy by non licensees... Supply: Point of supply. Administration and Rules.stete electricity consultative councils and 'local advisory committees.. restriction on licensees. obligation on licensees to supply energy. Control of transmission and use of energy. notice of accidents and enquiries. it enacts • The central electricity authority: Constitution. Meters. to consumers. Power to control the distribution and consumption of energy.inter state Dept ofEEE. General protective clauses: protection of railways.. Powers of the state governments to give direction to a licensee.. I 4. Advisory boards. Powers to require accounts. appointment of electrical inspectors.. distribution and supply companies. of transmission companies.. captive generation and dedicated transmission lines. • De-licensing. transport policy regarding subsidies. transmission. distribution and supply companies.-. . • . transmission. 1998: The act provides f~~the establishment of the central electricity regulatory commission and state regulatory commission.. Open access and . trading and developments of electricity markets. accounts and audit. rationalization of electricity tariff. powers of entry... setting up and operating new generating stations. central and state transmission utilities. saving of application ofact. Power and duties of state electricity boards. jurisdiction.theact provides for • National electricity policy and plan • Promoting competition... Transmission Company. Parallel distribution. water power concession to be granted only to the board are a generating company.. officers and other employs of the board to be public servants.members. The works and trading procedure of the board.". and generating companies. 1998.Directions of generating.~ • Page 14 . • Compulsory consumer metering... _j -"'T*l"'. the Indian electricity supply act. Q The electricity regulatory commission act. • Duties of generating.Electrical Design Estimation & Costing lOEESt agreement to extend boards jurisdiction to another state . coordination between boards and multipurpose schemes. and distribution and supply companies.. and the generating company. annual reports statistics and returns arbitration penalties cognizance .formation . coordination with the r~ional electricity board. Dept of EEE. transmission companies.. The electricity act.objects. of offences direction by the state government . generating companies. • Licensing transmission...provision· relating to income tax. SJBIT !'-.. framing grid code and grid standards. 1948 and the electricity act 191O.etc. 2003: The content supersedes and consolidates the provision of the electricity regulatory commission act. promotion of efficient and environmentally benign policies and for matters connected with it.. The boards finance. miscellaneous items such as effects of other laws.. protection to persons acting under this act. e Offences and penalties for theft of electricity. canals. docks. • Finance. liabilities.' e Protection of railways.. e Power of the central government to facilitate and impress the efficient use of energy and its conservation. • Rationalizing subsidies.. Consumer protection: standard of performance.. { • Works.. • Notice. sources of energy or biomass connected to the grid it delineates.. e Transfer of assets. high ways. • Power of the state government to facilitate and impress the efficient use of energy and its conservation.Electrical Design Estimation & Costing 10EE81 • Reorganization of state electricity boards.. . e Appointment of electrical inspectors.. etc. • Constitution and functions of the central electricity authority. e The establishment and incorporation of the bureau of energy efficiency. wharfs and piers. telephone and electric signaling lines. wasting electricity extinguishing public lamps. Telegraphic.provisions. accounts and audit of the bureau. nuclear substances or materials and hydroelectricity and includes electrical energy or electricity generated from renewable. Energy conservation act 2001: This act concerns any form of energy derived from fossil fuels. advisory committees. e.ofaccidents and enquiries. e Power and function of the bureau. electric lines and materials. and Penalties and adjudication Dept of EEE. aero drums. of the energy management center. Others and miscellaneous . . appointment of . ' .. SJBIT Page 15 .. e special courts dispute resolutions • Tariff regulations. • Constitution and functions of central and state regulatory commissions. Electric supply lines ..clearences and supports erection of or alterations of buildings structures conditions to apply where telecommunication lines and power lines can be carried on the same supports. pole type substations discharge of capacitors. • General safety precautions regarding. It contains 143 rules along with detailed annexure and covers: I • Authorization to form duties.. provisions . service lines and apparatus on consumers premises. • General conditions relating to supply and use of energy: Testing of consumer's installation. • Overhead lines: Materials and strength. Voltage of supply. periodical inspection testing of consumers installations. identification of earthed conductors. • Electric traction: Additional rules for electric traction. Commencement of license. Point of supply. 1910... applicable t9... Supply ofx ray high frequency installations.joints.. advertisement of application and contents thereof approval of draft license and a notification for grant of licence. Precaution against leakage.. • Inspection of electric Installations: creation of inspection agency. general conditions has to transformation.accessbality of bare conductors .. entry and inspection.... inspection fees.. owners electrical contactors ..construction.. Current density in rails. intimation of accidents precautions to be adopted by consumers. use and control of energy.. contents and form of draft license. 1956. . Dept of EEE.Electrical Design Estimation & Costing lOEE81 The Indian electricity rules 1956 As per section 37 of Indian electricity act.connection with earth. Dedined voltage and frequency of supply pacing and sealing of energy and demand meters. Difference of potential on return..... lines crossing.medium.high and extra high voltage: Testing of insulation resistance . voltage test systems.. supply to neonsigns.electrical work man and suppliers .installation..service lines protection against lightning . amendment of license preparation and submission of accounts and model condition of supply.protective equipment instructions for restoration of persons suffering from electric shock. Precautions against failure of supply.submission of records by supplier or owner • Licensing :application. appeal against an order .pprotection operation and maintenance of electric supply lines and apparatus. unused overhead lines. SJBIT Page 16 • . The central electricity board has framed the Indian electricity rules.system and apparatus for low. Size and strength of trolley wires records.opproval by inspector. . supply and use of energy by non licenses and others penalty for breaking seal and other penalties for breach of rules repeal ' I '. Dept of EEE.. SJBIT Page 17 .relaxation by the inspector.Electrical Design Estimation & Costing lOEE8t • Additional precautions for mines and oil fields. • Miscellaneous provisions :Rules relaxation by the government . Substation Classification . centers. where the generators were housed. The word substation comes from the days before the distribution system became a grid. which are generally located far away from the load. High voltage transmission lines are used to transmit the electric power from the generating stations to the load centers. Substations may be owned and operated by an electrical"utility. or may be owned by a large industrial or commercial customer. Between the generating station and consumer. These Dept ofEEE.:. or perform any of several other .zt. Generally substations are unattended. A substation is a 'part of an electrical generation.Electrical Design Estimation & Costing 10EE81 UNIT-2 DESIGN AND ESTIMATION OF SUBSTATIONS: .. or at the interconnection of two different transmission voltages. smaller generating plants were converted to distribution stations. Introduction ( . and were subsidiaries of that power station. Key diagram of typical substations Introduction . and distribution system.:. Selection and location of site for substation .. . Substations Electric power is produced at the power generating stations. through several substations at different voltage revels. As central generation stations became larger. .y. A substation may include transformers to change volta:ge levels between high transmission voltages and lower distribution voltages. important functions. receiving their energy supply from a larger plant instead of using their own generators.:. The first substations were connected to only one power station.44 JG}. or the reverse. . SJBIT Page 18 4ll. transmission.. relying on SCADA for remote supervision and control. electric power may flow. Substation Earthing • •:. Substations transform voltage from high to low.:. Between the power generating st~tion and consumers a number of transformations and switching stations are required. The electric power i s produced at the power stations which are located at favourable places.Electrical Design Estimation & Costing lOEE8t are generally known as substations. Substations are to disconnect equipment or circuit at the time of faults. It is an assembly of electrical components such as bus-bars.f etc. Although there can be several types of Dept ofEEE. voltage.) used for this purpose is the sub-station. etc. near the consumers localities. d. generally quite away from the consumers. for switching operations of transmission provided with safety devices Substations are the convenient Some substations provide facilities lines. This job is againperfonned by suitable apparatus (e. the voltage may have to be stepped down to utilizationlevel. transformer etc. p.c. According to service requirements substationsand it is classified in to transformer substations. switchgear apparatus. it may be desirable and necessary to change some Characteristic (e. The assembly of apparatus (e.e.c to dc. Similarly. Thisjob is againaccomplished by a suitable apparatus called sub-station. power to d.c.c motors etc.g. i.c power e. SJBIT Page 19 Wi . electroplating. power transformers .) of electric supply. switching converting substations. For example.g ignitron) called sub-station. frequency. This is accomplished by suitableapparatus caned sub-station. Yet at someplaces inthe line of the power system. generation voltage (11 kV or 6·6 kV) at the _po~er station is stepped up to hi g h voltage (say 220 kV or 132 kV) for transmission of electric power. a. The substations may be classified in according to service requirements and constructional features. it may be desirable to convert large quantities of a. It is clear that type of equipment needed in a sub-station will depend upon the service requirement.. transmitted and distributed in the form of alternating current. The present-day electrical power system is a. place for installing synchronous condensers for the purpose of improving power factor and it provide facilities for making measurements to monitor the operation of the various parts of the power system. others are converting stations.g. It is delivered to the consumers through a large network of transmission and distribution. electric power is generated. At many places in the line of the power system. for traction. Their main functions are tf receive power transmitted at high voltage from the generating stations and reduce the voltage to a value suitable for distribution. Substations are important part of power system and form a link between generating stations.g. transmission systems and distribution systems. c. Dept of EEE.. SJBIT Page 20 .44lOV . sub-stations which change the voltage level of the electric supply.aadaJ:y ~ 33OV'.~ c:_ Sec.e To~ latge. i. lDnSmissiJ. DOKV 66KV 1.e.m System 705 XV.Electrical Design Estimation & Costing lOEESt sub-stations. 4()() The tiDe 110 «h!!!r ' KV.'0 inemum 1arg. we shall mainly confine our attention to only those sub-stations where the incoming and outgoing supplies are a. there is an ease of operation of the substation. circuit. A fault on the feeder or transformer circuit breaker .Electrical Design Estimation & Costing lOEE8t Types of Substations: 1.causes loss of the transformer and feeder . This design also places minimum reliance on signalling for satisfactory operation of protection. SJBIT Page 21 . Each circuit is protected by its own circuit breaker and hence plant outage does not necessarily result in loss of supply. Single Busbar: The ~eneral schematic for such a substation is shown in the figure below. With this design. Dept of EEE. Such a substation has the following characteristics. one of which may be restored after isolating the faulty circuit breaker. Additionally there is the facility to support the economical operation of future feeder bays. . Maintenance of a feeder or transformer circuit breaker involves loss of the circuit. All circuits may be restored after isolating the faulty circuit breaker. . Mesh Substation: The general layout for a full mesh substation is shown in the schematic below. . 2. SJBIT Page 22 "U ... Maintenance of one busbar section or isolator will cause the temporary outage of two circuits. Introduction of bypass isolators between busbar and circuit isolator allows circuit breaker maintenance facilities without loss of that circuit. complete shutdown of the substation. The characteristics of such a substation are as follows. Dept ofEEE. A busbar fault causes loss of one transformer and one feeder.Electrical Design Estimation & Costing lOEESt A fault on the bus section circuit breaker causes. . 3. Busbar faults will only.JBIT Page 23 .Electrical Design Estimation & Costing 10EE81 Operation of two circuit breakers is required to connect or disconnect a· circuit. I ":1/ ~ The reason that such a layout is known as a 1 1/2 circuit breaker is due to the fact that in the design. and no additional bypass facilities are required. . . s. not more than twice as many outgoing circuits as in feeds are used in order to rationalize circuit equipment load capabilities and ratings. Generally. Some characteristics of this design are: Dept ofEEE. Breaker faults will involve the loss of a maximum of two I circuits.1 ~. 1 112circuit breakers protect 1 feeder.\ . . cause the loss of one circuit breaker. >k x 10 the schematic below. ' .1 .. One and a half Circuit Breaker layout: The layout of a 1 112 circuit breaker substation is shown ry . there are 9 circuit breakers that are used to protect the 6 feeders. Circuit breakers may be maintained without loss of supply or protection. Thus. and disconnection involves opening of a mesh.. . Dept of EEE. & Costing cost of the circuit It is possible to operate anyone lOEESt breakers together with the complex pair of circui ts... it employs 'n + l' circuit breakers.." . Main and Auxiliary bus bar: This is technically a single bus bar arrangement "Auxiliary bus" energj zed from main busbars with an additional bus bar called through a bus coupler circuit. . There is a very high security against the loss of supply. This bus arrangement has been extensively used in 132 kV Sub Stations. Each circuit is connected to the main bus bar through a circuit breaker with isolators on both sides and can be connected to the auxiliary bus bar through an isolator. for 'n' number of circuits. As in the:case of single bus arrangement? this scheme also suffers from the .Electrical Design Estimation There is the additional arrangement. 4...energizing by that breaker as that circuit then gets energized the circuit through bus coupler breaker. .e. at a without de -. disadvantages . the entire substation . main: bus bar or the "associated isolator. . SJBIT " Page 24 . or groups of pairs of circuits.. that in the event of a fault on the.. i.. is lost. . The additional bus coupler circuit (Auxiliary time for routine controlled overhaul bus) facilitates and maintenance provision of taking out one circuit breaker. This scheme suffers from the disadvantage that when any circuit breaker.taken out for maintenance.tAIN AND AUXILIARY BUS BAR ARRANGIDvlENT • 5. This Bus bar arrangement was generally used in earlier 220 kV sub stations. Each circuit can be connected to either one of these bus bars through respective bus bar isolator./ Power Vtv' 'Iransformer ~ TYPICALlV. . Bus coupler breaker is also provided so that the circuits can be switched on from one bus to the other on load. is . Double bus bar: In this scheme.Electrical Design Estimation & Costing 10EE81 Incoming Line ~ /. the associated feeder has to be shut down. a double bus bar arrangement is provided. SJBIT Page 25 . Dept of EEE. IT /' ~I' ~ Power . Dept of EEE. SJBIT Page 26 .t Transformer TYPICAL DOUBLE BUS BAR ARRANCEAfENT • 6./" -: Main Bus . bus coupler to the Auxiliary breaker and Auxiliary bus during breaker without affecting the other circuits. Auxiliary transferred of double bus bar scheme can be overcome bus.Electrical Design Estimation & Costing 10EE81 Incoming Line Bus - Couplet I ~ 'lr-/-i" 'Ir-. by usmg additional bus isolators. maintenance The feeder is of its controlling This Bus bar arrangement circuit is generally used nowadays in 220 kV sub stations. Double Main and Auxiliary bus bar: The limitation . / .IAINAND AUXILIARY BUS BAR AR.Electrical Design Estimation & Costing 10EE81 Bus Coupler Main Bus-I[ .R." Dept of EEE. • According to service requirement • According to constructional features . Classification of sub-station There are several ways of classifying sub-station. Auxiliary BUS Transformer T"k"PICALDOUBLE ?v. .ANGEI\i. However the two most important way of classifying them are.IENT . e t ... SJBIT Page 27 ."' .. 1. 2. . are known as industrial sub-station.c. correction sis. 4. Such sis may be required for industrial utilization 5. Those sub-stations. SJBIT . These sub-station which improve the p. 3.f. Switching sub-station: These sub-station simply perform the switching operation of power line. electrical welding etc.f. Industrial sub-station: '. Frequency changer SIS:· Those sub-stations. Dept ofEEE. • • 6. II! Page 28 fa . power into d. of the system are called p. electroplating. Transformer sub-station Those sub-station which change the voltage level of electrical supply are called TIF sis. Power factor correction SIS: . these are generally located 'at receiving end sis. power are called converting sis ignition is used to convert AC to de power for traction. Converting sub-station: Those sub-station which change a.Electrical Design Estimation & Costing 10EE81 According to service requirement: According to service requirement sub-station may be classified into. are known as frequency changer sis. which supply power to individual industrial concerns. which change the supply frequency.c. equipment is invariably installed outdoor. • There should be reasonable access for both equipment & personal. when the. atmosphere is contaminated with impurities. Under such situations. The TfF step down Dept ofEEE.. Electric power is almost distributed in localities through such sub-station.pole or 4pole structure. 2)Indoor Sub-station :For voltage upto II KV. Side to protect the sub-station from lighting strokes. It is because for such Voltage the clearances between conductor and the space required for switches.Electrical Design Estimation & Costing lOEE81 According to constructional features i According to constructional features. • • There should be provision for emergency lighting and protection against fire. the equipment of the sis is installed indoor because of economic consideration. limited and the cost of the land is high. and other equipment becomes so great that it is not economical to installed the equipment indoor.T. the space available for equipment and building is. The IIKV line is connected to the TIF (11KV1440V) through gang isolator and fuses. SJBIT Page 29 . However. • The size of the sis should be as minimum as possible. • • There should be good ventilation 4) Pole-mounted sub-stationsThis is an outdoor sub-station with equipment installed overhead on H. The lighting arresters are installed on the H. It is the cheapest from of sis for voltage not exceeding IIKV (or 33KV in some cases). the sub-station is created underground. the sub-station are classified as : 1) Outdoor Sub-Station :For voltage beyond 66KV.B. C. The design of underground sis requires more careful consideration. 'these substations can be erected for voltage upto 66KV 3) Underground sub-station :In thickly populated areas. Key diagram of typical substations: . SJBIT Page 33 ..DOub~isol~$Witch 4 On IQad isolating switch • Dept ofEEE. housing etc. .Electrical Design Estimation & Costing 10EE81 5. 6. hospital. Drainage facility: The site selected for the proposed substation should have proper 1 drainage arrangement or possibility of making effective drainage arrangement to avoid pollution of air and growth of micro-organisms detrimental to equipment and health. drinking water. Availiblity of essential amenities to the staff: The site should be such where staff can be provided essential amenities like school. SJBIT '"# w¥ Page 34 . .....& Costing Electrical Design Estimation 10EE81 7 Oil circuit breaker Lightning: ~ (active gap) .. .. • "J Dept of EEE. . ' .. .B. 3-phase. the 11 kV line is brought to the indoor sub-station as underground cable. 3-phase. 4-wire. switch consists of isolators connected in each phase of the 3phase line. 400 V. (iiI) The secondary of transformer supplies to the bus-bars via the main O. side of the transformer (11 kV/400 V) via the 11 kV O.Electrical Design Estimation & Costing 10EE81 Key diagram of typical substations: (l) The 3-phase. 3:"wire11 kV line is tapped and brought to the gang operating switch installed • near the sub-station.C. The transformersteps down the voltage to 400 V.C. (il}From the G~O. The G.B: The voltage Dept of EEE. 4-wire supply is given to the various consumers via 400 V O.C. It is fed to the H.switch.B.O. From the busbars. SJBIT Page 35 .T. the switchgear in substations is located on :both the high voltage and the low voltage side oflarge power transformers. control. Typically. or SF6 equipment. a transformer and switchgear line-up may be combined in one housing. Oil-filled equipment allowed arc energy to be contained and safely controlled. The·very earliest ceht~al1?owerstations used simple open knife switches. . using oil circuit breakers. This type of equipment is directly linked to the reliability of the electricity supply. (iv) The CTs are locatfd at suitable places in the sub-station circuit and supply for the metering and indicating instruments and relay circuits Equipment for substation and switchgear installations: In an electric power system. switchgear is. with medium-voltage circuit breakers for distribution circuits. it switchgear line-up would be a metal-enclosed structure with electrically operated switching elements. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. along with metering.Electrical Design Estimation & Costing 10EE81 between any two phases is 400 V and between any phase and neutral it is 230 V. For industrial applications. called a unitized substation or USS. Today. mounted on insulating panels of marble or asbestos. the combination of electrical . disconnect switches. The switchgear on the low voltage side of the transformers may be located in a building. making opening manually operated switches too dangerous for anything other than isolation of a de-energized circuit. metering and communications. oil-filled equipment has largely been replaced by air-blast. protect and isolate electrical equipment. 400 V motor load is connected across 3-phase lines directly. • High voltage switchgear was invented at the end of the 19th century for operating motors and other electric machines. protection.100 kV. allowing large currents and power levels to be safely controlled by automatic equipment incorporating digital controls. and protection equipment. Power levels and voltages rapidly escalated.phase. By the early 20th century. SJBIT Page 36 . vacuum. Dept of EEE. fuses or circuit breakers used to control. The single phase residential load is connected between anyone phase and neutral whereas 3. The technology has been improved over time and can be used with voltages up to 1. To. . AC power is required for substation building small power. -.more number of earthing stations are provided at different places and are interconnected which helps to reduce the potential gradient. This chapter . safe at earth potential even though the insulation fails.. DC power is used to feed essential services such as circuit Jreaker trip coils and associated relays. The fault current through the neutral of the transformer to earth is to be distributed over a large area. lighting. otherwise the potential gradient of the earth around the earth connection may be dangerous. anti-condensation heaters and motors. describes how these auxiliary supplies are derived and explains how to specify such equipment.such'as transformer tank.. etc. To keep the-non-current carrying metal part::.substation equipments.provide proper grounding-for.' To provide a discharge path for lightning arre~ts. switchgear operating mechanisms. serves best to distribute the heavy fault .. gaps. A conductor is said to be solidly earthed when it is electrically connected to an earth electrode without intentional addition of resistance or impedance in the earth connection. For small stations. Dept of EEE. supervisory control and data acquisition (SCADA) and communications equipment. any other conductor or an array of conductors electrically connected to the general mass of the earth. current over a large earth area.Electrical Design Estimation & Costing lOEE8t Substation auxiliaries supply: All but the smallest substations include auxiliary power supplies. some communications equipment.. • BASIC TERMS OF EARTHING Earth: An object is said to be earthed when itis electrically connected to an earth electrode. SJBIT Page 37 . Substation Earthing: Earthing system~are provided in a substation for the following main reasons: -.».. structures. Earth Electrode: A metal plate. and ventilation.. etc. pipe. heating.. Earth mat consisting of heavy gauge-bonded conductors or cost iron grid buried at adepth of not less than 30 em and connected to the earth electrode.'. in terms of short circuits. i. electric shock. ~.. Peterson-coi 1 grounding (or resonant grounding) . etc. etc. stability. . Transformer tank.. protection. METHODS OF NEUTRAL GROUNDING The various methods of grounding the neutral of the system are: • 1. Solid grounding 2. fire. For example: motor body. Equipment earthing refers to connecting the non-current carrying metallic parts to earth available in the neighbourhood of electrical circuits. the purpose of neutral earthing and that of equipment earthing are distinctly different. the neutral of the system is solidly grounded.e. the neutral grounding is an important . The very purpose of earthing is to safeguard the equipment against possible damage due ~o .._ .aspect of power-system designs because the . . SJBIT Page 38 • ] ¥'h!!1fit .. In most of the modem high-voltage systems. etc. J!. performance of the system..& Costing Electrical Design Estimation Earthing Lead: lOEE81 The conductor by which the earth electrode is connected to neutral is called earthing lead. switch gear.. the neutral is connected directly to the ground. Reactance grounding 4. dROUNDING OR NEUTRAL EARTHING: TEte word "earthing" and "grounding" different from neutral-point have the same meaning. Earthed transformer Dept of EEE..Today. Voltage transformer grounding 6. It is very important to have good and effective earthing or grounding . . Equipment earthing ensures safety while neutral earthing is done mostly to ensure that the stator short-circuit current is limited and for stability reasons. 5. . Resistance grounding 3. Thus... is greatly affected "by the state of the neutral. . But equipment earthing is earthing. GROUNDING GRID: Grounding grids are used where there is a chance of flow of large fault currents through the • system. A grounding grid is composed of a number of rods that are joined together through i copper conductors to reduce the overall grounding resistance.: Fig. ground without any impedance between neutral and ground as shown in Fig. 13. SJBIT Page 39 .Electrical Design Estimation & Costing lOEE81 SOLID GROUNDINGOR EFFECTIVE GROUNDING: The term effective grounding is the same as solid grounding. the line to neutral voltage of phase 'a' becomes zero. but the phase to the earth voltage of the remaining two healthy phases'will be appro?C.l below . however..13 Solidly __ c grounded system Consider a line to ground fault on anyone phase. The performance of a" grounding grid system suffers when the rods are removed from the mesh.:. Voltage between the ground surface and the conductor should be kept at a minimum in case of a fault. They are also known as earthing mats or earthing grids. especially in the case of hard soil or soils having low conductivity. becomes an expensive process. This arrangement should be made near the ground surface as it limits the potential gradient.imately constant. As a result of this fault. The neutral is directly connected to . The following factors have to be taken into account while designing a grounding grid: . Driving rods deep into the soil.-----------------------4a ~--------------~b ~---------------------------- " ". Dept of EEE. say phase 'a' at a point F as shown in fig 2. . Ground is different from the electrical neutral. This article is intended to describe common features of electrical wiring that may apply worldwide. Use these tips to leam how to wire an electric motor. washing machines. . commonly referred to as building wiring.. ' __ t. providing them with • single phase AC power. AC power is brought into your house or shop in 3 phases. This article describes general aspects of electrical wiring as used to provide power in buildings and structures. Electric motors are the tools that use the altemating current (AC) power supplied to your home or shop by the power distribution company and transform it to mechanical energy to drive compressors.. but 120 electrical degrees out of phase with each other.. Larger motors are generally wired as 3 phase AC motors.' . tools. SJBIT §Me Page 40 it .". garage door openers. and is provided only for protection fi:om electric shock. Smaller motors are generally wired as 1 phase to neutral. and all are wired differently.Electrical Design Estimation & Costing 10EE81 UNIT -3: ELECTRICAL INSTALLATION FOR POWER CIRCUITS: Introduction: Electrical wiring in general refers to insulated conductors used to carry electricity. In addition. using all 3 phases of incoming power and not connecting to the electrical neutral line.. All of these types of motors must be wired properly to perform the desired motion. direct current (DC) motors can be used in battery power applications that do not have AC. fans. For information regarding specific national electrical codes.' Dept of EEE. " . and associated devices. Separate articles cover long-distance electric power transmission and electric power'distribution. Important considerations regarding motor "installation wiring: Electric motors are used in a wide variety of applications that affect our daily jives. and anything else that requires mechanical motion to operate. each of them 120 volts AC when referred to an electrical neutral. refer to the articles mentioned in the next section. Confirm that the motor rotates in the proper direction. tre motor shaft will turn when the 2 motor wires are connected to the power source. SJBIT Page 41 . • . the motor nameplate and motor manufacturer's information should explain the needed wiring to make the motor turn in a particular direction.carrying' as little current as possible. Dept ofEEE. Check the voltage rating of the motor..motors being driven by the 3 phase input power in a line to neutral configuration. The rated operating voltage will be listed on the nameplate of the 1110tOr. .. Wire the motor. available at hardware or electrical supply stores. It also can be noted that the motor has 3 connecting wires.be connected to the positive side of the power source and which should be connected to . 2.Electrical Design Estimation & Costing 10EE81 1. to strip about half an inch (13 111m)· of insulation from the end of the 1110torwire. 2.:. Use wire strippers. The motor nameplate or manufacturer's information will specify which of the 2 motor wires should. Secure the motor wire under the screw termination available on the power distribution panel. clockwise or counter clockwise.. • COnfiect··a 3···:ehaseAGMbtor Confirm that the motor is a 3 phase AC motor. If the motor does not rotate in the desired direction. Figure out the direction that the motor will tum'. That information should direct that I motor wire be attached to 1 (any 1) of the 3 power phases available and the other motor wire be attached to electrical neutral. . the negative side of the power source to achieve the desired direction of rotation. For example. Confirm from the motor faceplate the operating voltage that the motor will require from the power distribution system. Count the . 3.Attempt to ... Establish the direction of motor rotation. This information will be on the motor faceplate. rather than 2. 4.bal~mcethe power being drawn from each of the 3 available phases so that the neutral line is . The motor faceplate will define which direction. Consult the motor nameplate or manufacturer's information for this information. a motor intended to run from a 12-volt car battery should be rated at 12 volts. Determine the rotation. A high neutral current can unbalance the power system and cause poor motor performance.. the input leads may be swapped to reverse the motor direction of rotation. 5 hp. Dept of EEE. . as load decreases. Wire the 3 motor leads to the 3 phases of input power. peak efficiency is at 7..: JIg • :4lt.. If the motor does not turn in the desired direction.~i'J! • . . as shown in Figure 1. SJBIT Page 42 :4"'. Do not use the neutral line. A motor is considered under loaded when it is in the range where efficiency drops significantly with decreasing load. Figure 2 shows that power factor tends to drop off sooner.. However. . Attach the motor power leads. a 10-horsepower (hp) motor has an acceptable load range of 5 to 10 hp. Maximum efficiency is usually near 75% of rated load. A motor's efficiency tends to decrease dramatically below about 50% load. swap any 2 of the 3 motor wires to reverse the direction of rotation of the motor. 5.Electrical Design Estimation & Costing 10EE81 3. Determination of inputpower: Reasons to Determine Motor Loading Most electric motors are designed to run at 50% to 100% of rated load. the range of good efficiency varies with individual motors and tends to extend over a broader range for larger motors.. Thus. but less steeply than efficiency.. ..5-5. "10l~..99.~J!J!p ~~" . use them to estimate motor part-load..!:!!!p 1!-'.. With measured parameters taken from hand-held instruments.~.' .'.. 1. . You can then quantify the motor's part-load by comparing the measured input power under load to the power required when the motor operates at rated capacity.' Determining Motor Loads Input Power Measurements When "direct-read" power measurements are available.--~~~~--'~~· --~.:. "1tIges: . SJBIT g.-Ij.. ~ . The relationship is shown in Equation 3...J ~-. ....--:. . you can use Equation 1 to - calculate the three-phase input power to the loaded motor... ...~--.•0.. Page 43 Dept of EEE.~~ . '. .Electrical Design Estimation & Costing 10EE81 Figure 1 Motor Part-Load Efficiency (as a Function of'110 Full-Load Efficiency) ....~~--~~~~ Pemmf'uU·load . V I PF =: RMS current. Synthetic rubber compounds are used widely for insulation and sheathing of cables for flexible and for heavy duty applications. It is advisable that wiring of this type which is still in .7457 .of rated power PI Measured three-phase power in JeW Plr "" Input power at full-rated load in JeW = Determination of rating of cables: Cable insulation materials • Rubber For many years wiring cables were insulated with vulcanised natural rubber (VIR). p Load e P. mean line-to-line of 3 phases =: Equation 2 : 0.service should be replaced by a more modem cable. SJBIT Page 44 . although it is many years since it was last manufactured. = VxLrPFx.= hopx-'111 P Where: Plt = Jnput. when the rubber cracks and loses its insulating properties. Many Dept of EEE. X 100% "Where: Load =: OUtput power as a %. In this condition it will continue to give satisfactory service unless it is disturbed. becoming hard and brittle. " _.Jf 1000 Where: ~ =: Three-phase power in JeW .power at full-rated load in JeW hp .. Much cable of this type is still in service. Since the insulation is organic. mean of 3 phases Power factor as a decimal = RMS voltage.& Costing Electrical Design Estimation lOEE8t Equation 1 P. it is subject to the normal ageing process. . Nameplate rated horsepower 11ft = Efficiency at full-rated load = Equatiorf3' . c. is available which remains flexible at temperatures down to -20°C. as well a.v. LSF (Low smoke and fume) Materials which have reduced sm~ke and corrosive gas emissions in fire compared with p. it absorbs moisture from the air. P.v.c. hard and brittle. If it is in contact with absorbent materials.v. and XLPE (thermosetting) insulated cables in place of paper insulated types. as well as the weight of the cable. paper insulated cables are sheathed with impervious materials.c.v.s resistance to oil.v.C. This difficulty. If p.c. ozone and ultra-violet radiation depending on the formulation.) is now the most usual low voltage cable insulation. Dept of EEE. Because of this.c.c.V. SJBIT Page 45 . Dry paper is hygroscopic. has led to the widespread use ofp. Polyvinyl chloride (p.Electrical Design Estimation & Costing lOEE8t variations are possible.C.c. - At high temperatures the material becomes soft so that conductors which are pressing on the insulation (eg at bends) will 'migrate' through it. and so BS 7671 specifies that it should not be worked at temperatures below 5°C. the plasticiser may be 'leached out' making the p. lead being the most common. although versions which will operate safely at temperatures up to 85°C are also available. burns. It is clean to handle and is reasonably resistant to oils and other chemicals. sometimes moving to the edge of the insulation. it emits dense smoke and corrosive hydrogen chloride gas. The physical characteristics of the material change with temperature: when cold it becomes hard and difficult to strip. However a special p.v. When p. is exposed to sunlight it may be degraded by ultra-violet radiation. that is. It must be sealed to ensure that there is no contact with the air. must notbe allowed to exceed 70°C. Paper Dry paper is an excellent insulator but loses its insulating properties if it becomes wet. PILC (paper insulated lead covered) is traditionally used for heavy power work.v. Cables of this kind need special jointing methods to ensure that the insulation remains sealed. with conductor temperature ratings from 60°C to 180°C. Because of this property the temperature of general purpose P. The paper insulation is impregnated with oil or non-draining compound to improve its long-term performance.v. Thermosetting (XLPE) Gross-linked polyethylene (XLPE) is a thermosetting compound which has better electrical properties than p. . insulator. great mechanical strength. It has more resistance to deformation at higher temperatures than p.c. special seals are used to terminate cables.and high-voltage applications.c. The resulting cable is totally fireproof and will operate at temperatures of up to 250°C. Special mineral-insulated cables with twisted cores to reduce the effect of electromagnetic interference are available. which reduces the temperature at which the cable may be allowed to operate. SJBIT Page 46 - . . They are normally used as sheathing compounds over XLPE or LSF insulation. resistant to radiation and electromagnetic pulses.kept sealed within a copper sheath. and is therefore used for medium. It is also entirely inorganic and thus non-ageing. . the cable is used with an overall LSF covering. Dept of EEE. which it is gradually replacing. are pliable and corrosion resistant.v.Electrical Design Estimation & Costing 10EE81 have been available for some years. These cables have small. and can give considerable safety advantages in situations where numbers of people may have to be evacuated in the event of fire. Thermosetting insulation may be used safely with conductor temperatures up to 90°C thus increasing the useful current rating. Mineral Provided that it is kept dry. . a mineral insulationsuchas magnesium oxide is an excellent '. Since it is hygroscopic (it absorbs moisture from the air) this insula!ion is . In cases where the copper sheath may corrode. are waterproof. It is also replacing PILC in some applications.v.diameters compared with alternatives. Since it is necessary to prevent the ingress of moisture.. especially when ambient temperature is high. A LSF (low smoke and fume) type of thermosetting cable is available. earth continuity conductor: bare copper wires [1_.copper conductor - c) Split-concentric PVC insulated cables . .•.tb II- PVC sheath' 12 .Electrical Design Estimation & Costing lOEE8t Non-flexible low voltage cables Types of cable currently satisfying the Regulationsare shown in {Fig 4. a) Non-armoured pvc-insulated cables .PVC insulation 15 ..tc 7 6 5 4 1 2 1 .PVC oversheath 12 . -. stranded or flexible b) Armoured PVC-insulatedcables .1a II- _" pvc sheath 12 .:..PVC bedding 14 . SJBIT Page 47 :.PVC phase insulation Dept ofEEE.Fig 4.copper conductor: solid.. .16 .PVC insulation I ~ 3 2 t 1 3 . _ 5 ..Melinex binder .1}. ..Fig 4.Fig 4.armour-galvanised steel wire /3 . r'""w""i~re~------'-'--.inmi or smaller.2} shows some of the many types of flexible cords which are available.textile braided and compounded I 3 I 2 1 12 ~ 85°C 13 _ tinned rubber insulation copper conductor Flexible low voltage cables and cords By definition flexible 'cables' have conductors of cross-sectional flexible cords are sized at 4.2a 11 .neutral conductor: . a) Braided circular ..1d 1 ...15 . whilst .e.Fig 4.... {Figure 4.Electrical Design Estimation 10EE81 & Costing 13 .· ---c"'-op---p.. Quite dearly... the electrician is nearly always concerned with flexible cords rather than flexible cables.oversheath _ PVC 14 _ insulation - _ pvc coloured Ir2----------b-ra-'-jd--_ ---p-Ia--in'..PVC strings 17 . area 4 mrrf or greater..... SJBIT Page 48 . black PVC-covered wires d) Rubber-insulated (elastomeric) cables .Conductors _ plain Copper· Dept of EEE.Fig 4....copper conductors 4 ... plain copper e) Braided circular insulated with glass fibre .inner sheath .Fig 4. SJBIT T . .insulation (Cores) 60°C rubber 321 13 -conductors .----- 13 .Fig 4.tinned copper.pvc 13 .insulation ~O°Crubber or pvc' 1 2 13 ..-----------.2b 1 .conductors .. 3 2 .w: 0 .-.Fig 4. c) Circular sheathed ..2c .sheath -jubber or pvc 1 .PVC • 12 .glass braided overall Page 49 Dept of EEE.conductors .2e 1 .tinned copper " d) Flat twin sheathed .pvc ------------ 1 b) Unkinkable .Electrical Design Estimation & Costing 10EE81 r----. ?F.2d II- sheath . r-' 0:: .Fig 4.rubber layer collectively textile braided semi-embedded ~ 2 .I 1 .! o h 'I .insulation . '. . . SJBIT • Page 50 sell . such as 150°C rubber.2f ·C::=.Fig 4.~-~co~n-d~u-c~to-r~s---p-Ia-i~n-c-o-pp-e-r------~1 Flexible cables should not normally be used for fixed wiring. they must be visible .c.3) shows a short length of such cord used to make the final connection to a luminaire.stranded Copper 1) 1 Single core p. . throughout their length. • The temperature at the cord entry to luminaires is often very high. (Fig 4.conductors .asswhich can be supported by each flexible cord is listed in (Table 4H3A)..insulation.insulated and braided.insulated non-sheathed .pvc rI2~. Dept of EEE.v. especially where filament lamps are used. but if they are.2). part of which IS shown here as (Table 4.silicon rubber 13 . Maximum mass to be supported Cross-sectional area (mmj) (kg) . It is important that the cable or flexible cord used for fmal entry is of a suitable heat resisting type.Electrical Design Estimation & Costing 10EE81 2 .========== at:tT~ •. The maximum m. I /1 .insulation . . The fuse size should be based on the SMALLEST wire (largest gage number). One common misconception about choosing the correct fuse size is that it's dependent the load of the circuit. you can also look at the topic this was posted in on Oznium forums for a step by step guide to finding the amperages for common products at the Oznium store. SJBIT _- Page 51 . .150°C rubber-insulated and braided flexible cord used for the final connection to a luminaire .Electrical Design Estimation & Costing lOEE8t Fig 4. Dept of EEE.'. the load of the circuit should have nothing to do with choosing a fuse size. Actually. " The question of determining fuse size has been a common one lately so we decided to make a quick write up on choosing the correct fuse size. Determination of rating -offusee .in the circuit. Here is how to correctly choose the right fuse size for your circuit.3 . 2) Use the followingtable to determine the maximum current for whatever wire gage is being used. I) Determine the wire gage you already have by locating it on the package or measuring it. shielded.F. Dept of EEE. Surge. . Since these are only a few of the contributing parameters. Application testing and verification prior to production distribution Board main switch and starter: Power Distribution Board is a panel that has got fuses.Currents.. application.) IGFuse holder features.. Normal operating current 2. or height 8. Maximum available fault current 6. Pulses. It is through this main distribution board. Agency Approvals'required. Inrush Currents.I. It divides an electrical power feed into subsidiary circuits and provides protective fuse for each circuit placed within a common panel.) 11. etc. CSA. Start-up Currents. the electricity' is supplied to the Sub Main Distribution Board (SMDB) and electricity goes to the panels for further distribution. etc. contact your Littelfuse products reprentative.. PC board mount. diameter. Selection Factors 1. SJBIT Page 52 - . 4. Mrii Oi: Military 9.such as length. circuit breakers and ground leakage protection components required to distribute electrical power to many individual circuits or end user points.Electrical Design Estimation & Costing 10EE81 The application guidelines and product data in this guide are intended to provide technical information that will help with application design. Ambient temperature . VDE. such as UL. and Circuit Transients 7. 5. visual indication. panel mount. mounting block. R. if applicable and associated rerating (clips. Many of the factors involved with fuse selection are listed below. Overload current and length of time in which the fuse must open . Physical size limita~ions. Application voltage (AC or DC) 3. ease of removal. Fuse features (mounting type/form factor. testing is strongly recommended and should be used to verify performance in the circuit/application. MET!. For adritional assistance with choosing fuses appropriate to you requirements. axial leads. innovative designs are to be made so that clients have safe and uninterrupted power supply. Offering premium quality of work is important so that clients get value for their money. punched to clients requirements Termination for 'up to 4 cables per phase can be provided Dept of EEE. 3-pole. General features of Main Distribution Board >>- Busbars and. it is important . or as per requirement suitable for floor and wall mounting CABLING Removable undril1ed gJand pates on top and bottom. 30kA or 50kA BUS BARS H. Haryana. . polyester powder coated to RAL 7032 textured. To build the projects as per the requirements of the customers. non.shrouded . electrolytic ally tinned and colour coded ENCLOSURE Electro galvanized sheet steel.. . To have safe installation of electricity. and industries as well as other electrical contractors in North India including Punjab. commercial houses.H. that the work gets done from the best technical house.C. . incoming terminals . reducing connection costs >- Metering section and cable plinth can be provided INCOMER Load break switch 125 to 800A.ferrous type for single core cables. Right technical expertise is needed to accomplish the job.are fully. SJBIT Page 53 I . OUTGOINGS MCCBs 15 to 400A... J pole. 30kA or 50kA. and Chandigarh etc. Designing and building the electrical projects and implementing them flawlessly are not a small task that can get handled by any electrical company.D. It is important to keep high standards in the work they deliver as the part of electrical contracting services.. 3P with external rotary handle MCCB 100 to 800A. . Box type-terminals are provided on outgoing MCCBs for termination of cables. The clients include end users.Electrical Design Estimation & Costing 10EE81 Power Distribution Boards are common for most of the industrial or commercial electrical installations or for residential buildings. copper. motor. Now the question is why thesetypes of de -4 motors require the assistance of the starter in the first case. that the back emf at the starting is zero. SJBIT "~. develops as the motor armature starts to rotate in presence of the magnetic field. There is reliable after sales service provided by the company that saves installation cost.Electrical Design Estimation & Costing lOEE8t As per the specifications given by the clients. They are the manufacturers of one of the safest and cost-effective SMDB that complies with the quality standard.-This also essentially means. by generating action and counters the supply voltage. The only explanation to that is given by the presence of back emf Eb. The back emf. Dept of EEE. I Starter and its Importance: A 3 point starter in simple words is a device that helps in the starting and running of ashunt wound de motor or compound wound de motor. an exclusive range of power distribution board is designed by the best-in-class technicians at Advance Switchgear Co. cost of equipment storage and field testing.. Page 54 -Iii 'II . which plays a critical role in governing the operation of the . and develops gradually as the motor gathers speed. In the event of a fire or flash tlood. When the power goes out because of a storm. company connects their wires to your homes' feeder wires that attach to the meter on your home or power pole. Disconnect Switch- _A disconnect switch is mounted on the outside of your home close in proximity to the meter on .. Main Breaker Dept of EEE. The other instance is having a transfer switch in which you can switch between live power and a generator for backup power.having to enter a burning home or a flooded basement. This is where the electric . SJBIT Page SS . Your homes' electricity starts with the electrical service connection. INSPECTION AND TESTING OF INSTALLATION: I- Introduction: I We depend on electricity to light our homes. and even cook our meals. This is the device that measures the amount of electricity your home uses and determines the amount of money the electric company charges you on a monthly basis. a short circuit. The advantage of having a disconnect switch is for - safety.. a-neutral.--From here your meter either feeds a disconnect switch or a mainbreaker Or fusepanel. you can shut the power off from the outside of your home verses.the outside of your home or power pole. and a ground wire. A typical home has a single phase service consisting of an "A" phase and a "B" phase. turn on our television sets. or another problem in the electrical circuit. . understanding what the basic components of an electrical system is a must.Electrical Design Estimation & Costing 10EE81 UNIT -4 SERVICE CONNECTION. Branch Circuit Breakers Breakers that fe~d lighting. In a tripped state. an electric stove or central air conditioning. homes have a 100 amp or a 200 amp service. Dept of EEE. These appliances don't work unless both "A" and "B" phases are working. . Examples of 240 volt appliances would be an electric range. These switches come in many different styles and colors to suit your design needs. The 120 volt circuits require'a single pole breaker. It is used to turn the power on and off to the entire electrical panel. In that case. using only one phase of the electrical service. the wires would heat up and eventually could cause a fire.Electrical Design Estimation & Costing lOEE8t A breaker panel consists of a main breaker that is sized according to your homes' load needs. These.device you are connecting to. Switches Switches are the devices that turn on and off lights and fans in your home. A main breaker of 100 amps will only allow 100 amps to flow through it without tripping. In a 240 volt circuit. This main breaker protects the main service wires from damages that would occur given an overload. outlets. It is the interrupt between the service and the branch circuits of the panel.central air conditioning and sub-panels are considered branch circuits. There are single-pole. Typically. Remember to size your breaker by the name plate rating on the. outlets and furnaces. three-way. The breakers are usually sized at 15 or 20 amps. These circuits provide power to lighting. no current will flJw throughout the panel. Most of these examples would require a two-pole 30 amp breaker. SJBIT Page 56 .circuits can either be 120 volts or 240 volts. a two-pole breaker uses both phases of a circuit. Romex is a . Their purpose is to alter the flow of current to your lights and fans in a home. protected areas (inside stud walls.Electrical Design Estimation & Costing 10EE81 four-way and dimmer switches.. Televdions. SJBIT 1-' 1ft *sp--t¥ i5s . . Wiring is sized according to the load demand required. sheath. "Types of service connection and their features: This describes various types of utility electrical services and supply voltages. Wires are covered by aluminum or steel flexible sheath that is somewhat resistant to damage. - These different types of wiring carry electrical current from the panel to the device being fed.. Some outlets are used especially for wet areas.). freezers. computers. Outlets consist of a hot feed. The nominal system supply voltages listed below can vary by ±lO% or more. "" Bx cable is known as armored cable. Check the rated required load requirements marked on each device to determine the needed size wire to carry the needed load.This . Outlets Electrical outlets are used to plug portable devices into. Single strands of conductor wire are pulled through conduit that is the safest method for wiring for durability purposes. vacuums and toasters are all good examples of devices that can be plugged into an outlet. lights. Wiring Your home's wiring consists of rome x. on the sides of joists. etc. a neutral and a ground. BX cabl"~or wiring concealed in conduit. W~tt Node meter models are Page 57 Dept of EEE. - is suitable for use in dry. brand name for a type of plastic insulated wire: The"formal name is NM that means non-metallic . that are not subject to mechanical damage or excessiveheat. Dept of EEE. Medium Voltage: 601 volts to about 34. times the phase-to-neutral In symmetrical three-phase electrical system.• Voltage levels: • .. or 4 (not counting the safety ground) . Low Voltage: 600 volts or less ". Delta connected systems typically do not have a neutral .500 volts ". the phase-to-neutral voltages should be equal if the load is balanced. • Neutral present: • - Wye connected systems have a neutral • .3.732 . SJBIT Page S8 .Electrical & Costing Design Estimation 10EE81 available in seven different versions that cover the full range of electrical services types and voltages. High Voltage: 46. Meters and current transformers are designed for use on either 50 or 60 Hz systems.000 volts and up Wye Line-to--Neutral Wye or.Delta Line-lo-Line Voltage Voltage • 208 120 240 230 400 240 415 m 480 347 600 Line-to-line voltages voltages: = L732 v'3 • 120 are typically 1. Classification of Different Services: Altelnating current electric power distribution systems can be classified by the following properties: • Frequency: 50 Hz or 60 Hz • Number of phases: single or three phase • Number of wires: 2. ~. what is meant by electrical schedule? 4. 8. tendering and single tender? . limited. Explain by giving examples for the following terms.. i) Contingencies ii) Overhead charges iii) Profit Department of EEE. State the important facts.Electrical Design Estimation & Costing lOEE8t Assignment Questions UNIT -1: General Principles of Estimation .SJBIT Page 1 . functions and setup ofa organization. What is the purpose of estimating and costing? How is price list of materials prepared? 6. I. 3. iv) Contingencies v) Purchase System vi) Purchase orders. i) Electrical Schedule ii) Market survey and source selection iii) Catalogues ·. Define estimating and state its purpose. which an estimator should know for preparing an internal Wiring estimate. I 2. 9. Write the short notes on the following. Give the objectives. . State. How is the quantity of material required for internal wiring determined? Q 5. What is meant by global tendering. 7. 7.: 5:·What is the. 10 for small substations why pole mounted substations are preferred. 6. Write a shortnotes on determination of input current to motor 5~Write a short notes on determination of rating of cables. Page 2 Department of EEE. What is substation? Classify the substations according to the service and constructional Features. 7.Electrical Design Estimation & Costing 10EE81 UNIT2: Design and Estimation of Substations 1. Write a short notes on determination of rating of fuses. Write a short notes on determination of input power. ( 4. What are bus-bars and what are their functions? .. What is circuit breaker? Explain its functions. 8. 8. distribution board. What are the different types of substations? Write short notes on each of them.L Write a short notes on Power wiring. What are the functions of a substation? 2.' £l!¥¥¥¥Wf ~'~4:~ *f§t§§ @tW{ . 9.. Differentiate the functions between an isolator and a circuit breaker..necessity of substation in a power system? 6. Write a short notes on lightening wiring. What are the factors to be considered for motor installation wiring? 3.. Write a short notes on the following: i) Classifications of substations ii) Indoor Substations iii) Outdoor Substations and their necessity.SJBIT . 2. UNIT 3: ELECTRICAL INSTALLATION FOR POWER CIRCUITS . iv) Pole mounted substations v) Circuit breakers vi) Substation Earthing vii) Lightening Arresters . Compare outdoor and indoor substations. i . 3. Write a short notes on determination of size of conduit. main switch and starter. 4. is installed? iii) Why use of GI pipe is made for carrying the cable up to 2 meters fr~m the ground? 5." Department of EEE. Page 3 . SJBIT . Write a short notes on underground cables. What do you understand by by service line? Write down the various methods of installing Service lines. Explain the methods of installation of service mains in a two storey building with separate Energy meters. 2. Write a short notes on the following: i) Service line ii) Installation of service line for low roof building 4.. . Explain the following.. 3..OEE81 UNIT 3: SERVICE ~ONNECTION.~ ." Electrical Design Estimation & Costing 1.. INSPECTION AND TESTING OF INSTALLATION: I. i) How weatherproof cable service line is installed? ii) How underground cable service connection . 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