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List of Questions: What is Power Transmission? What is Corona in Transmission Lines?  What is ACSR? What is Sag? What is an Insulator? What are some factors on which sag depends? Why do overhead transmission lines posses capacitance? Why bundled conductors are employed in transmission lines? Why transmission line conductors are stranded? What is skin effect?  1. What is Power Transmission? The carriage of electric power from Generation Station to Distribution Stations is known as Power transmission. Electric power is generated at the power stations (Nuclear plants, Hydro power plants, Coal power plants etc.). It is then transmitted over large distances to distribution stations with the help of conductors known as transmission lines 2. What is Corona in Transmission Lines?  When an alternating voltage is applied across two conductors having larger spacing as compared to their diameters, there is no change in surrounding air. However, when the applied voltage exceeds certain limit (techn

  Power Transmission and Distribution:   The structure of a power system can be divided into generation (G), transmission, (T), and distribution (D) facilities, as shown in Figure (A). An ac three-phase generating system provides the electric energy. this energy is transported over a transmission network, designed to carry power at high or extrahigh voltages over long distances from generators to bulk power substations and major load points. the subtransmission network is a medium to high-voltage network whose purpose is to transport power over shorter distances from bulk power substations to distribution substations.  The transmission and subtransmission systems are meshed networks with multiplepath structure so that more than one path exists from one point to another to increase the reliability of the transmission system.  The transmission system, in general, consists of overhead transmission lines (on transmission towers), transformers to step up or step down voltage levels, substat

Electrical basics: Voltage : The unit is volt.  voltage is the amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called voltage. Resistance: The unit is ohm. It  is represented by two circuits with equal voltages and different resistances. The circuit with the higher resistance will allow less charge to flow, meaning the circuit with higher resistance has less current flowing through it. Current: The unit is ampere. It measure the amount of charge flowing through the circuit over a period of time Power: The unit is watt. Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. It is the rate of doing work. Volt-ampere (VA) : V olt-ampere is the unit used for the apparent power in an electrical circuit. The apparent power equals the product of root mean square voltage and root mean square current. In direct current circuits, this produ

Installation of electrical conduits, accessories and boxes : Normally using three types of conduits. 1. EMT conduits - Electrical metallic tubing 2. PVC conduits - poly vina chloride  3. Flexible conduits. What are the equipment and machinery required for installation? Electric grinder - cutting of support elements Bending spring - bending pvc pipes Heat gun - softening pvc pipes before bending Hack saw - cutting of pvc / EMT pipes EMT pipe bending machine - bending of EMT pipes Round file - removing the burr from cuts Drilling machine - Drilling for anchors Line dori, marker pen, plump line - marking for conduit route. Hand tools - hammer, screw driver, spanner set etc. Concrete hole saw cutter - coring hollowcore slabs General and procedure for installation : Size of conduits to be used shall be as per the drawing  Conduit shall be inspected before installation, and if not smooth inside and outside, free of flows and imperfect of any kind, it shall not be installed.  Ensure that joii

  Identification of electrical equipment and devices : MSB - main switch board (HV) LPDB - lighting and power distribution                         board PDB - power distribution board LDB - lighting distribution board LFB - lighting feeder pillar IPS - isolated power system UPS - uninterruptible power supply MCB - miniature circuit breaker  MCCB - moulted case circuit breaker  ACB - air circuit breaker  VCB - vaccum circuit breaker ELCB - earth leakage circuit breaker  HV - high voltage  MV - medium voltage  LV - low voltage  ELV - extra low voltage  A - ampere  V - voltage W - watts WAP - wireless access point ACP - access control panel  SD - smoke detector  LS - loud speaker AV - audio video  BB - battery bank BC - battery charger BD -bus duct GCP - generator control panel GEN - standby diesel generator TR - transformer MCC - motor control centre EMCC - emergency motor control centre  CBS - central battery system ECBDB - emergency central battery                                  dist

  Auto transformer: Auto transformer is kind of transformer, where primary and secondary shares some common single winding. So basically its one winding transformer Auto transformer employs only single winding per phase as against two distinctly separate windings in a conventional transformer. Applications of auto transformer : -compensating the voltage drops by boosting supply voltage in distribution system. -auto transformer with a number of tapping are used for starting induction and synchronous motor.  -auto transformer is used as variac in laboratory or continuous variable over broad  ranges are required.  Instrument transformer : It is used in AC system for measurement of electrical quantities i.e. Voltage, current, power, energy, power factor, frequency. It is also used with protective relays for protection of power system. Basic function of instrument is to step down the ac system voltage and current. Types of instrument transformer : Parameter type : -current transformer (CT) 

  TRANSFORMER: 1.what is a transformer? The transformer is a static machine used for transforming power from one circuit to another without changing frquency. Transformer operates on ac supply. The transformer working on the principle of an mutual induction. It doesn't have rotating or moving parts so transformer is a static machine. 2.what is the working principle of transformer? It is based on the faraday's law of electro magnetic induction. Mutual induction between two or more winding is responsible for transformation action in an electrical transformer. According to the faraday's law: rate of change of flux linkage with respect to time is directly proportional to the induced emf in the conductor or coil. 3.what are the main parts of transformer? Primary winding.  Magnetic core.  Secondary winding.  4.what are the accessories of a transformer ? Bucholz relay.  Silica gel breather of transformer.  Oil surge relay.  Radiator of transformer.  Magnetic coil gauge.  LV and HV

  INDUCTION MOTOR 1.What is an induction motor? an alternating current motor in which torque is produced by the reaction between a varying magnetic field generated in the stator and the current induced in the coils of the rotor. It is also called as asynchronous motor.  2.what are the types of induction motor? Single phase induction motor a) split phase induction motor b) capacitor start induction motor c) capacitor start capacitor run induction motor d) shaded pole induction motor Three phase induction motor a) squirrel cage induction motor b) slip ring induction motor 3.what is slip in an induction motor? It is the difference between the flux speed(Ns) and rotor speed(N). Speed of the rotor of an induction motor is always less than its synchronous speed. %slip = (Ns-N) *100/Ns. 4.what are the methods of measuring slip? a) measurement of rotor speed b) measurement of rotor frequency c) stroboscopic method 5.what are the method of speed control in three phase induction motor? a)control

 Testing of Electrical cables(HV, MV, LV) : The following shall be the guidelines for the testing personnel during the inspection and testing of LV, MV and HV cables. 1.Phase identification test: Use safety grounding devices to discharge any trapped charges before connecting /disconnecting any test leads or other connections to/from the cable. Disconnect the cable under test from any electrical circuit. Connect the battery box, at one end of the cable :            - 0V to earth            - 4.5V to L1            - 9V to L2            - 13.5V to L3 Using a multimeter, check if at the other end of the cable, the voltages for each phase are correct according to drawings and specifications. 2.Shield continuity test: Use safety grounding devices to discharge any trapped charges before connecting /disconnecting any test leads or other connections to/from the cable. Using a multimeter, measure the resistance of the shield. Investigate the shields with resistance of more than 10 ohms per 1000f

How to do Installation and Termination of Electrical cables(HV, MV, LV) : 1.Material : All wires and cables to be examined prior to installation. No wire or cable with bruised, cut or abraded insulation, or wire that does not pass a continuity test shall be used. 2.Tools and equipment : Truck, crane, cable drum jacks, cable drum shaft, cable socks, cable rollers, cable cutter, hydraulic crimping tools, hand crimping tools, scaffolding with wheels, ladders, torque wrench, box spanner set, ring spanner set, open end spanner set, screw driver, hack saw frame, measuring tape, drilling machines, holesaw cutter, cutting pliers.  3.Preparation : Cables shall be identified with regard to type, size, length etc. And shall be inspected for any physical damage. The cable shall be free from any damages and the ends sealed with caps to prevent the ingress of water during transportation or storage.  4.Installation : All cable shall be megger tested prior to pulling cable.  Prior to commencing the ca

Moulded case circuit breaker (MCCB): MCCB is a type of electrical protection device that is used to protect the electrical circuit from excessive current, which can cause overload or short circuit.It is mostly used in industries, commercial buildings.  -The range of rated current is up to 1000A -Trip current may  be adjusted -Thermal/thermal magnetic operation 

 Miniature  Circuit breaker(MCB) : MCB is an automatically operated electrical switch. protect an electrical circuit from damage caused by excess current from an overload or short circuit. The function is to interrupt current flow after a fault is detected.It is mostly used in homes, commercial buildings, industries.  -The range of rated current is up to 100A  -Thermal / thermal magnetic operation.  Types of Circuit breaker - single pole, double pole, three pole and four pole.

  Isolator :                An  isolator  is a device used for isolating a equipment or circuit from a source of power. An  isolator  is a mechanical switching device. The ampere rating: 20A to 160A Maximum operating temperature: 60 degrees Celsius  Types of isolator-single pole, double pole, three pole and four pole isolator     

  Electrical tools has 3 types 1.Hand tools 2.Measuring tools 3.power tools 1.Hand tools:                       Hand tools are powered by hand other than electrical power. Categories of hand tools are pliers, cutter, spanner, screw driver, hammer, hacksaw frame, crimping tools, insulation tape, alanki set.etc. 2.Measuring tools:                                  measuring tool is anything used to take a measurement of current, voltage, power, resistance. Measurement tools are multimeter, clamp meter, megger, earth resistance tester.  3.Power tools:                          Power tools are actuated by an additional power source other than solely manual labour used with hand tools. Categories of power tools are hammer drill, jigsaw, cordless drill, cutting machine.