Underground Single-Phase AC SystemThe electric transmission system which transmits the single-phase AC electric power through the underground cables is termed as the underground single-phase AC system of transmission.The underground single-phase AC system of electric power transmission is classified into three types viz. −Single-Phase Two-Wire AC SystemSingle-Phase Two-Wire AC System with Mid-Point EarthedSingle-Phase Three-Wire AC SystemThe various systems of the electric transmission require different volume of conductor material. The volume of conductor material required in the above 1-phase underground AC system is described below.Conductor Material Required in 1-Phase 2-Wire Underground AC SystemThe typical single-phase 2-wire AC underground AC system is shown ... Read More

Underground DC SystemWhen the DC electric power is transmitted from the power generating station to the consumer through the underground cables, then the electric power transmission system is called the underground DC system.The underground DC transmission system is classified into three types −Two-Wire DC SystemTwo-Wire DC System with Mid-Point EarthedThree-Wire DC SystemConductor Material Required in Underground 2-Wire DC SystemThe underground two-wire DC system is shown in Figure-1. It has two conductors taken from the generator terminals.Let, 𝑉𝑚 = Maximum voltage between conductors𝑃 = Power to be transmitted𝑙 = Distance for which power is transmittedThe load current is given by, $$\mathrm{\mathit{I_{\mathrm{1}}\mathrm{\, ... Read More

Suspension InsulatorThe suspension type insulator is the one which consists of a number of porcelain discs connected in series by metal links in the form of a string as shown in Figure-1.Potential Distribution over Suspension Insulator StringAs we know the string of suspension insulators consists of a number of porcelain discs connected in series through metal links. The porcelain portion of each disc is in between two metal links. Thus, the disc acts like a capacitor represented by C as shown in Figure-2.The capacitance C is called the mutual capacitance. If the string has only mutual capacitance, then the charging ... Read More

Three-Phase Transmission SystemA three-phase transmission system is the one in which three line conductors are used to transmit the AC electric power from generating station to the substations. The three-phase system is universally adopted for transmission of electric power.Depending upon the number of conductors used, the three-phase AC transmission system is classified into two types viz. −Three-Phase Three-Wire SystemThree-Phase Four-Wire SystemConductor Material Required in 3-Phase 3-Wire AC SystemConsider a three-phase three-wire AC system as shown in Figure-1, it has three line conductors and one earthed neutral wire. The three-phase three-wire system may be star connected (as shown in Figure-1) or ... Read More

Single-Phase AC Transmission SystemThe electric power transmission system in which two conductors viz. phase conductor and neutral wire are used to transmit the electric power is known as single phase AC transmission system.The single phase AC transmission system can be classified into following three types viz. −Single-phase two-wire system with one conductor earthedSingle-phase two-wire system with mid-point earthedSingle-phase three-wire systemConductor Material Required in 1-Phase 2-Wire System with One Conductor EarthedThe single phase two wire AC system with one conductor earthed is shown in Figure-1.Let, $\mathrm{Power\: transmitted\mathrm{\, =\, }\mathit{P}}$$\mathrm{Maximum \: voltage \: between\: conductors\mathrm{\, =\, }\mathit{V_{m}}}$$\mathrm{RMS\: value\: of \: voltage\mathrm{\, =\, ... Read More

String EfficiencyThe suspension insulator is the one which consists of a number of porcelain discs connected in series by metal links in the form of a string.The voltage applied across the string of the suspension insulators is not uniformly distributed across the various discs, i.e. the disc nearest to the line conductor has much higher potential than the other discs. This unequal potential distribution is undesirable and it is usually expressed in terms of string efficiency. Therefore, the string efficiency of the suspension type insulator is defined as follows −“The ratio of voltage across the whole string to the product ... Read More

Transmission Line SupportsThe supporting structures used for overhead transmission line conductors, such as poles and towers, are called the transmission line supports.Generally, the transmission line supports supposed to possess the following properties −The line supports should have high mechanical strength so that it can withstand the weight of conductors and wind loads, etc.It should be light in weight without the loss of its mechanical strength.It should have longer life.It should be cheap in cost and economical to maintain.Accessibility of line conductors for maintenance is to be easy.There are various types of line supports available. The choice of supporting structure for ... Read More

What is Electric Supply System?The carrier of electrical power from power generating station to the consumer’s premises for its utilisation is called the electrical supply system.The whole electric supply system is segmented into three principle components, viz. −Power generating stationTransmission systemDistribution systemThe electric power is produced at the power generating station which are located quite away from the consumers. Then, the power is transmitted over large distances to load centres with the help of conductors called transmission lines. Finally, it is distributed to a large number of consumers through a distribution system.Types of Electric Supply SystemDepending upon the types of ... Read More

The element of the transmission line by which the line conductors are insulated from supports is known as line insulator. The insulators used in the transmission lines are of various types. Some of the important types of insulators are given as follows −Pin Type InsulatorSuspension Type InsulatorStain InsulatorShackle InsulatorPin Type InsulatorsThe pin type insulator is shown in the figure. The pin type insulator is fitted to the cross-arm on the pole. The pin type insulator has a groove on the upper end of the insulator for housing the line conductor. The line conductor passes through this groove and is bounded ... Read More

Corona Effect in Overhead Transmission LineThe phenomenon of violet glow, hissing sound and production of ozone gas in an overhead transmission line is known as corona.When a very high voltage is applied across two conductors of the overhead transmission line whose spacing is large as compared to their diameters. When this applied voltage exceeds a certain value (called critical disruptive voltage), then the conductors are surrounded by a faint violet glow that is known as corona effect.In practice, the corona effect is accompanied by a hissing sound, production of ozone, power loss and radio interference. The higher is the transmission ... Read More