M5-Electrical installationsbee (2).pptx

Basic of analog in electrical engineering used in day to today life and application in electrical system Basic of analog in electrical engineering used in day to today life and application in electrical system Basic of analog in electrical engineering used in day to today lifeBasic of analog in electrical engineering used in day to today life and application in electrical system application in electrical system

1. K.S.RANGASAMY COLLEGE OF TECHNOLOGY (Autonomous) 50 EE 001 – BASIC ELECTRICAL ENGINEERING MODULE 5- ELECTRICAL INSTALLATIONS AND HOUSE WIRING S.Jaividhya AP/EEE

2.   Components of LT Switchgear SFU, MCB, ELCB, MCCB. Miniature Circuit Breaker The MCB has some advantages compared to fuse. It automatically switches off the electrical circuit during abnormal condition of the network means in over load condition as well as faulty condition. The fuse does not sense but miniature circuit breaker does it in more reliable way. MCB is much more sensitive to over current than fuse. Another advantage is, as the switch operating knob comes at its off position during tripping, the faulty zone of the electrical circuit can easily be identified. But in case of fuse, fuse wire should be checked by opening fuse grip or cutout from fuse base, for confirming the blow of fuse wire. Quick restoration of supply can not be possible in case of fuse as because fuses have to be rewirable or replaced for restoring the supply. But in the case of MCB, quick restoration is possible by just switching on operation. Handling MCB is more electrically safe than fuse. Because of to many advantages of MCB over fuse units, in modern low voltage electrical network, miniature circuit breaker is mostly used instead of backdated fuse unit. Only one disadvantage of MCB over fuse is that this system is more costlier than fuse unit system.

3. MCB

4. Working Principle Miniature Circuit Breaker There are two arrangement of operation of miniature circuit breaker. One due to thermal effect of over current and other due to electromagnetic effect of over current . The thermal operation of miniature circuit breaker is achieved with a bimetallic strip whenever continuous over current flows through MCB, the bimetallic strip is heated and deflects by bending. This deflection of bimetallic strip releases mechanical latch. As this mechanical latch is attached with operating mechanism, it causes to open the miniature circuit breaker contacts. But during short circuit condition, sudden rising of current, causes electromechanical displacement of plunger associated with tripping coil or solenoid of MCB. The plunger strikes the trip lever causing immediate release of latch mechanism consequently open the circuit breaker contacts. This was a simple explanation of miniature circuit breaker working principle.

5. Miniature Circuit Breaker Construction It is very simple, robust and maintenance free. Generally a MCB is not repaired or maintained, it just replaced by new one when required. A miniature circuit breaker has normally three main constructional parts. These are: Frame of Miniature Circuit Breaker The frame of miniature circuit breaker is a molded case. This is a rigid, strong, insulated housing in which the other components are mounted. Operating Mechanism of Miniature Circuit Breaker The operating mechanism of miniature circuit breaker provides the means of manual opening and closing operation of miniature circuit breaker. It has three-positions "ON," "OFF," and "TRIPPED". The external switching latch can be in the "TRIPPED" position, if the MCB is tripped due to over-current. When manually switch off the MCB, the switching latch will be in "OFF" position. In close condition of MCB, the switch is positioned at "ON". By observing the positions of the switching latch one can determine the condition of MCB whether it is closed, tripped or manually switched off.

6. Trip Unit of Miniature Circuit Breaker The trip unit is the main part, responsible for proper working of miniature circuit breaker. Two main types of trip mechanism are provided in MCB. A bimetal provides protection against over load current and an electromagnet provides protection against short-circuit current . Operation of Miniature Circuit Breaker There are three mechanisms provided in a single miniature circuit breaker to make it switched off. If we carefully observe the picture beside, we will find there are mainly one bi - metallic strip, one trip coil and one hand operated on-off lever. Electric current carrying path of a miniature circuit breaker shown in the picture is like follows. First left hand side power terminal - then bimetallic strip - then current coil or trip coil - then moving contact - then fixed contact and - lastly right had side power terminal. All are arranged in series.

7. If circuit is overloaded for long time, the bi - metallic strip becomes over heated and deformed. This deformation of bi metallic strip causes, displacement of latch point. The moving contact of the MCB is so arranged by means of spring pressure, with this latch point, that a little displacement of latch causes, release of spring and makes the moving contact to move for opening the MCB. The current coil or trip coil is placed such a manner, that during short circuit fault the mmf of that coil causes its plunger to hit the same latch point and make the latch to be displaced. Hence the MCB will open in same manner.

8. Again when operating lever of the miniature circuit breaker is operated by hand, that means when we make the MCB at off position manually, the same latch point is displaced as a result moving contact separated from fixed contact in same manner. So, whatever may be the operating mechanism, that means, may be due to deformation of bi - metallic strip, due to increased mmf of trip coil or may due to manual operation, actually the same latch point is displaced and same deformed spring is released, which ultimately responsible for movement of the moving contact. When the the moving contact separated from fixed contact, there may be a high chance of arc. This arc then goes up through the arc runner and enters into arc splitters and is finally quenched. When we switch on an MCB, we actually reset the displaced operating latch to its previous on position and make the MCB ready for another switch off or trip operation.

9. Earth Leakage Circuit Breaker or ELCB If any current leaks from any electrical installation, there must-be any insulation failure in the electrical circuit , it must be properly detected and prevented otherwise there may be a high chance of electrical shock if-anyone touches the installation. An earth leakage circuit breaker does it efficiently. Means it detects the earth leakage current and makes the power supply off by opening the associated circuit breaker . There are two types of earth leakage circuit breaker, one is voltage ELCB and other is current ELCB.

10. Voltage Earth Leakage Circuit Breaker The working principle of voltage ELCB is quite simple. One terminal of the relay coil is connected to the metal body of the equipment to be protected against earth leakage and other terminal is connected to the earth directly. If any insulation failure occurs or live phase wire touches the metal body, of the equipment, there must be a voltage difference appears across the terminal of the coil connected to the equipment body and earth. This voltage difference produces a current to flow the relay coil. If the voltage difference crosses, a predetermined limit, the current through the relay becomes sufficient to actuate the relay for tripping the associated circuit breaker to disconnect the power supply to the equipment. The typicality of this device is, it can detect and protect only that equipment or installation with which it is attached. It cannot detect any leakage of insulation in other installation of the system.

11. Current ELCB or RCCB or Residual Current Circuit Breaker The working principle of current earth leakage circuit breaker or RCCB is also very simple as voltage operated ELCB but the theory is entirely different and residual current circuit breaker is more sensitive than ELCB. Actually, ELCBs are of two kinds, but it is general practice to refer voltage based ELCB as simple ELCB. And current based ELCB is referred as RCD or RCCB. Here one CT core is energized from both phase wise and neutral wire.

12. Single Phase Residual Current ELCB. The polarity of the phase winding and neutral winding on the core is so chosen that, in normal condition mmf of one winding opposes that of another. As it is assumed that, in normal operating conditions the current goes through the phase wire will be returned via neutral wire if there's no leakage in between. As both currents are same, the resultant mmf produced by these two currents is also zero-ideally. The relay coil is connected with another third winding wound on the CT core as secondary. The terminals of this winding are connected to a relay system. In normal operating condition there would not be any current circulating in the third winding as here is no flux in the core due to equal phase and neutral current. When any earth leakage occurs in the equipment, there may be part of phase current passes to the earth, through the leakage path instead of returning via mental wire. Hence the magnitude of the neutral current passing through the RCCB is not equal to phase current passing through it.

13. Three Phase Residual Current Circuit Breaker or Current ELCB. When this difference crosses a predetermined value, the current in the third secondary winding of the core becomes sufficiently high to actuate the electromagnetic relay attached to it. This relay causes tripping of the associated circuit breaker to disconnect the power supply to the equipment under protection. Residual current circuit breaker is sometimes also referred as residual current device (RCD) when we consider the device by disassociating the circuit breaker attached to RCCB. That means, the entire parts of RCCB except circuit breaker are referred as RCD.

14. MOLDED CASE CIRCUIT BREAKER (MCCB) Definition – MCCB is a switching device which is used in LT electrical system. It provides protection against overload & short circuit. Fault sensing arrangements are installed inside MCCBs & shunt release is provided for remote tripping of MCCB. It is available between 100A & 630Acurrent.

15. Working Principle   MCCB provides protection against over load through thermal mechanism. It has bimetallic contacts which expand & contract on temperature changes. Under normal condition these contacts allow normal current to flow but when current exceeds its trip limit, the bimetallic contacts start heating up & expand until the circuit is isolated/tripped. When MCCB is tripped, faulty circuit is isolated from circuit & the temperature of bimetallic contacts starts getting normal & MCCB again is ready for next operation. Secondly, protection against short circuit – if current is very high, fault current should be interrupted immediately. This is achieved by electromagnetic induction. Whenever fault occurs, the high current induces a magnetic field in a solenoid coil located inside the breaker, this magnetic induction trips a contact & current is interrupted. In the tripping process, arc is produced & that is dissipated by taking suitable measures inside the breaker. These breakers can be manually switched off or on also which is required during maintenance or other purpose.

16. MCCBs are available with protection range from 50% to 100% of rated MCCB. Ex –200A, TP MCCB can be used from 100A load to 200A in steps of 10% e.g. 110A, 120A, 130A, 140A, 150A, 160A, 170A, 180A, 190A & 200A. On every stage MCCB will provide overload & short circuit protection. Selection of MCCB – It should be capable to carry the rated current of load, (Note: Rating of MCCB should not be much higher than rated/full load current otherwise MCCB will not trip on fault). Check number of poles – TP, TPN & 4P where TP (for 3 phase load) = TP stands for Triple pole which means three phases (R,Y,B) & these phases will be part of MCCB & neutral is not required for load. These 3 phases are opened & closed with the operation of MCCB.

17. TPN (for 3-phase load) = TPN stands for Triple pole with neutral where three phases will be part of MCCB & will be closed or opened with the operation of MCCB but neutral will be connected directly with load & neutral will remain connected with load , 4P (for 3-phase load) = 4P means Fore pole which means 3 phases & a neutral and all will be part of MCCB. In this case, 3-phases &neutral will be part of MCCB &opened & closed with MCCB operation. Type of protection–According to Time Curve protection. Fault current rating which should be in kA (thousand amperes) which means that a MCCB can withstand the fault current of short circuit, With operating Handle or without handle Ex – 200A TP MCCB with 35kA fault current& operating handle.

18. CURRENT RATING OF MCCBs  A typical range of Three phase MCCB –  100A, 125A, 150A, 200A, 250A, 315A, 400A, 630A, (Note: MCCBs are available with 25-50KA fault level.)

19. DIFFERENT TYPES OF BATTERY Primary Batteries: As the name indicates these batteries are meant for single usage. Once these batteries are used they cannot be recharged as the devices are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against recharge of primary cells. Some of the examples for the disposable batteries are the normal AA, AAA batteries which we use in wall clocks, television remote etc. Other name for these batteries is disposable batteries.

20. Secondary Batteries: Secondary batteries are also called as rechargeable batteries. These batteries can be used and recharges simultaneously. They are usually assembled with active materials with active in the discharged state. Rechargeable batteries are recharged by applying electric current, which reverses the chemical reactions that occur during discharge. Chargers are devices which supply the required current. Some examples for these rechargeable batteries are the batteries used in mobile phones, MP3 players etc. Devices such as hearing aids and wristwatches use miniature cells and in places such as telephone exchanges or computer data centre’s, larger batteries are used.

21. Types of Secondary (rechargeable) Batteries Nickel Ion Battery: The half-cell reaction at the positive plate: Ni2O3+ H2O + 2 e− ↔ 2 NiO + 2 OH− and at the negative plate: Fe + 2 OH− ↔ Fe(OH)2 + 2 e− (Discharging is read left to right, charging is from right to left.) The open-circuit voltage is 1.4 volts, dropping to 1.2 volts during discharge. The electrolyte mixture of potassium hydroxide and lithium hydroxide is not consumed in charging or discharging, so unlike a lead-acid battery the electrolyte specific gravity does not indicate state of charge. The voltage required to charge the Ni-Fe battery is equal to or greater than 1.6 volts per cel . Lithium hydroxide improves the performance of the cell. The equalization charge voltage is 1.65 volts. Nickel Iron battery is a high performance rechargeable battery with Nickle hydroxide positive plate, iron negative plates and potassium hydroxide as it’s electrolyte. Swedish inventor  Waldemar Jungner had developed a nickle iron battery in 1899, while working on his nickle -cadmium battery but abandoned the battery and production because of lower efficiency of charging reaction. American Inventor Thomas Edison invented, developed , used and popularized the nickle iron batteries latter in 1901 , he also patented the battery and deployed it to use and products with companies such as Detroit Electric.

22. Active Materials of Nickle Iron Battery a. Positive Plate: The positive plate of a Nickle Iron battery is formed of Nickle Hydroxide [Ni(OH)3] or Nickle Peroxide[NiO2]. The positive plate is formed with an addition of about 17% of Graphite and 2% of barium hydroxide  impurities. The addition of Graphite increases the conductivity of the plate and barium hydroxide increases the service life of plate. b. Negative Plate: The negative plate is formed by Iron and it’s Oxide. The negative plate is also added with very small amount of nickel sulfate and ferrous sulfide impurities to improve the performance of the plate. c. Electrolyte: The electrolyte is a solution of Potassium Hydroxide [KOH]  and distilled water. In the ratio of about 1:4.  A small amount of Lithium Hydroxide [ LiOH ] is also added with electrolyte for proper utilization of nickle peroxide at positive plate and thus increase performance and lifetime.

23. Construction The electrodes and electrolyte of a nickle iron cell or battery are assembled into a container made up of nickle plated iron. With welded lids providing holes for the terminals and for opening to examine and add electrolyte. The positive and negative plates of a Nickle Iron cell are grouped together and interlocked with Ebonite in between to prevent internal short between plates.   The negative group of plates contains one more plate than positive group and the two extreme end plates of negative plates group are connected to the external Nickle plated Iron container.

24. Nickel Cadmium ( Nicd ) Battery: Lead Acid Battery Lithium – Ion Battery

25. Important characteristics of batteries Chemistry The main  battery chemistries  are lead, nickel and lithium. They all need a specific designated charger, this is why charging these batteries on a different charger from their own might cause an incorrect charge, despite it may seem to work at first. This happens because of the different regulatory requirement of each chemistry. Voltage A battery features a  nominal voltage . Along with the amount of cells connected in series, chemistry provides the open circuit voltage (OCV), which is about 5-7% higher on a fully charged battery. It is important to check the correct  nominal voltage of a battery  before connecting it. Capacity The  capacity of a battery  indicates the specific energy in ampere-hours (Ah), which represents the discharge current that a battery is able to issue over the course of time. Installing a battery that has a higher Ah than indicated offers a longer runtime, just as a smaller Ah provides a shorter runtime. Moreover, charging a larger battery will take more time than charging a smaller one, but the Ah divergence must not surpass 25 %.  

26. Cold Cranking Amps ( Cca ) Every  starter battery  is marked with cold cranking amps, also abbreviated CCA. The number denotes the amount of  amps  that the battery is able to provide at -18°C. Specific Energy and Energy Density Specific energy  expresses the  capacity of a battery  in weight ( Wh /kg), and it can also be called gravimetric  energy density . Energy density, also called volumetric energy density, describes volume in liters ( Wh /l). Those products that need a long runtime at moderate load are optimized for high specific energy. Specific Power Loading capability is designated by  specific power , also called gravimetric power density. Power tools need a battery made for high specific power that features a lowered specific energy (capacity).

27. C-Rates C-rates  indicate how much time a battery takes to charge or discharge. If the battery is at 1C, it charges and discharges at a current that is equal to the marked Ah rating; at 0,5C, the time is doubled and the current is half; at 0,1C the time is 10-fold and the current is one-tenth. Load Load  describes the current drawn from a battery. The voltage drops under load because of the internal battery resistance and the state of charge ( SoC ), causing the end of discharge. Power is measured in watts (W) and it represents the current provided; energy is the physical work over the course of time and it is indicated in watt-hours ( Wh ). Watts And Volt-Amps ( Va ) Watts and Volt-amps  (VA) represent, respectively, the real power metered and the apparent power influenced by a reactive load. Watt and VA readings are equal if measured on a resistive load. A reactive load triggers a phase shift between voltage and current, causing the lowering of the power factor ( pf ) and the ideal one (1) to 0,7 or less. The dimensioning of electrical wiring and circuit breakers has to be based on VA power.

28. UPS Configurations The arrangement of rectifier, inverter, battery and other components can be carried out in different ways. Each arrangement has advantages and disadvantages.  Normally the more robust the configuration, the more expensive the UPS. UPS are classified in two basic ways - standby and on-line. In a standby UPS, power is normally supplied directly from the mains and the inverter only switched in if the mains fails.  This can have the advantages of cheaper cost and higher efficiencies.  On-line UPS always supply the load via the inverter.  These are more expensive, but because the inverter is always used they can resolve many power quality issues.

29. Standby UPS In a standby UPS, the static (electronic) transfer switch supplies the load directly with mains power.  In the event of power failure, the static transfer switch immediately changes over to power from the inverter . Static transfer switches when switching from mains to inverter power, will typically do this in less than 5 mS.   The battery is always kept at full charge by the rectifier and immediately available for supplying power.  Often a filter provides some power conditioning when supply mains power to the load.  A surge arrestor protects the UPS and loads from over voltage conditions.

30. On-line (Double Conversion) UPS    In on-line mode, the load is always supplied via the inverter.  The inverter normally takes it's input from the mains, but will switch to the battery when the mains supply goes out of tolerance.  The static bypass will supply power directly from the mains in the event the inverter is turned off or develops a fault . A big advantage of on-line UPS is that the load is always supplied by the inverter and many power quality issues on the mains are eliminated.

31. Relation between line and phase voltage and currents in balanced systems Star Connection Phase current ( Iph ) = Line currents (IL) Line voltage = √3 phase voltage Delta Connection IL = √3 Iph Phase voltage ( Vph ) = Line voltage (VL)

32. House Wiring Home wiring started when electric lights and telephone were first installed in homes towards the end of the 19th century. By the end of the 20th century an increased variety of systems were available for installation in homes. Therefore, Electrical service is considered essential in modern homes.

33. Service Entrance:  That portion of a home’s electrical system from the utility pole to the home’s main electrical disconnect. The main electrical service disconnect is the circuit breaker that turns all of the house’s electrical power off at one point. Mast Head:  The upper part of the metal conduit pipe, at the outside of the house, above the electric meter, where the electrical service wires from the street attach to the house. Neutral:  The return conductor (white wire) of a circuit connected ultimately to the earth to receive flow “back” from a light or appliance. Contact with neutral wire should not give you a shock. Drip Loop (at the service entrance):  Slack in the overhead electrical entrance wires (at the masthead) which prevents water from running down the service entrance wires and into the electrical panel.

34. Conduit:  A metal or plastic pipe through which electrical wires are run. Conduit protects wires from damage and are usually used in exposed locations, such as along the outer surface of a exterior house wall. Busbar :  A piece of rigid metal found in an electrical panel. A busbar distributes electricity from the service entry cable to the various circuits by means of their connection to the busbar . Breaker or Circuit Breaker:  An automatic safety device that shuts off the electrical power when the current (or amount of electricity or heat) becomes a greater volume of electricity than the breaker is designed to handle . Grounding:  The process of connecting all home electrical devices, appliances and wiring, whether intentional or accidental, so that they are connected to the earth, at the outside of the house. This interconnected grid means that excess electrical current will seek and be absorbed by the ground.

35. Domestic wiring Serivce main Meter board Distribution board Energy meter

36. Service main

37. Meter board