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Surge Impedance Loading: A transmission line may considered as generating capacitive reactive volt-amperes in shunt capacitance and consuming (absorbing) inductive reactive volt-amperes in its series inductance. The load at which inductive and capacitive reactive volt amperes are equal and opposite is called the surge impedance Loading or (nature load of the line). "The power delivered by the line to purely resistive load equal to its surge impedance the load at which the inductive and capacitive reactive volt-amperes are equal and opposite, is called surge impedance Loading of the line." Capacitive volt-amp. generated in the line = V *I = V / Xc = V² / ωL Inductive volt-amp.  absorbed in the line = V * I = I *XL = I² *ωL Under natural load conditions, Capacitive volt-amp. = Inductive volt-amp.             V² * wc   =    I² * ωL    or,  V / I   = √(L/C) =  Zo = Surge impedance At this load V and I are in same phase. At this Zo is purely resistive. There is not present imagina

Skin Effect: If DC is passed in a conductor, the current density is uniform over the cross section of the conductor but when alternating current flows through a conductor, the distribution tends to become non uniform. There is a tendency of the current to crowd near the surface of the conductor. This is called skin Effect. The current density is maximum at the surface of the conductor and minimum at the center of the conductor. The effect is equivalent to a reduction of the cross-section area of the conductor and, therefore the effective resistance of the conductor is increased. Skin effect is caused by opposing eddy currents induced by the changing magnetic field resulting from the alternating current. Fig. Skin Effect Skin Effect increases with increase in  i.) frequency ii.) Diameter of Conductor iii.) Permeability Method to Reduce Skin Effect: I.) Always use high conducting material such as copper, almunium etc. II.) We should use stranded wire instead of solid wire. III.) Frequenc

 Proximity Effect occurs in high A.C. Voltage transmission lines. It occurs two or more overhead conductor due to flux linkages. When two or more conductor are in proximity, their electromagnetic field interact with each other, with the result that the current in each of them is redistributed such that the greater current density is concentrated in that part of the strand most remote from the interfering conductor. In each case, a reduced current rating results from the apparent increases of Resistance. Apart from the skin effect the non uniformity of the current distribution is also caused by proximity Effect.Proximity effect is more in case of power cables.  Let's take a case, Two conductors; current flows in same direction: Fig. Current flow same direction We know that, Φ = LI  It's mean flux is directly proportional to inductor.  Inductive reactance (XL) = 2πfL     We can write, L =  XL / 2πf Now, we can says that, inductor is inversely proportional to frequency. Conditions

Corona: When a normal alternating voltage is applied across two conductors with enough sparing in between them,then there is no change in atmospheric conditions. But if the voltage applied exceeds a particular limiting value then the air surrounding the conductor gets ionised due to which hissing noise or a faint glow appears. Thus, the phenomenon of hissing noise, faint glow and production of ozone gas surrounding the overhead lines, due to ionisation of air is called Corona. The complete disruption in dielectric strength or insulation of an insulating material (air) near the surface of the conductor at certain point is called concept of Corona. Corona occurs only when the electric field intensity is greater than dielectric strength of air. Fig. Corona Effect In general Corona occurs around the power conductor due to two reasons: I.) Electrical power transmission is at higher operating voltage. II.) Number of free electrons in the space surrounding the power conductor are more due to

Tower: The structure which are used to support the transmission lines are called tower or line support poles. The types of Tower are following: 1.) Wooden poles:  Wooden poles are used for low voltages and distribution purpose only. Wooden poles are used for line Voltage upto 11 kV. 2.) Reinforced concrete poles: These poles are mechanically strong and their mantainance cost is low. Their life is very long but these tower are very heavy. Hence, the cost of transportation is high. These are used for system upto 33 kV voltage levels. 3.) Steel Tabular poles: These towers are designed for high and extra high voltage transmission line for longer life such poles must be painted regularly. 4.) Lattice steel Poles: This steel towers are very commonly used as these are suitable for the system with voltage higher than 33Kv and useful for long span. These are useful for railway line crossing; river crossing and crossing of valleys.

 Insulator is a substance through which electron doesn't flow. The overhead line conductors should be supported on the poles or tower in such a way that current from the conductors do not flow to earth through support. The types of Insulator are following: 1.) Pin type Insulator: The pin type Insulator is secured to the cross-arm on the pole. Pin type Insulator operate satisfactory required for transmission and distribution of Electrical voltage upto 33 kV. The value of safety factor for pin type Insulator is about 10. Fig. Pin type Insulator 2.) Suspension type Insulators:- The suspension type Insulator consists of number of procelain discs connected in series by metal link in the form of a string. A suspension Insulator is designed to operate at 11 kV. The no. disc in series would depend upon the working voltage. Fig. Suspension type Insulator 3.) Shackle Insulator:-  Shackle type Insulator are used I  tension cable. These Insulator can be operated either horizontally and vertica

Conductor: Conductor is a metal that permit allow to flow of electron from particle to particle inside it.An electrical conductor allows the electric charges to easily flow through them. The property of conductors to “conduct” electricity is called conductivity. Such materials offer less opposition or “resistance” to the flow of charges. Conducting materials allow easy charge transfer because of the free movement of electrons through them. Properties of Electrical Conductor: The main properties of electrical conductors are as follows: - A conductor always allows the free movement of electrons or ions. - The electric field inside a conductor must be zero to permit the electrons or ions to move through the conductor. - Charge density inside a conductor is zero i.e. the positive and negative charges cancel inside a conductor. - As no charge inside the conductor, only free charges can exist only on the surface of a conductor. - The electric field is perpendicular to the surface of that con

Resistance : Resistance is the opposition offered by the conductor to flow of current. The symbol of Resistance is  Mathematically, V= IR                  or, R = V/I The ratio of voltage to the current is known as Resistance. The Resistance of transmission line is uniformly distributed along its whole length. Effective Resistance = (Power loss in conductor) / I^2 We know that,              R =   ρ * l / a                   Where,    ρ  = Resistivity                                    l  = Length                                    a  = Cross-section area Now, we can define; Resistance is directly proportional to length and inversely proportional to the area of conductor. Inductance: When an alternating current flows through a conductor, a changing flux is setup which links conductor due to this flux linkage, the conductor produces inductance. The symbol of inductance: Mathematically, Inductance is defined as flux linkage per Ampere.           L = ψ /I       (Henry)    or, L = NΦ / I   

 When Recieving end of the transmission line is operating under no load condition or lightly condition,sending end voltage(Vs) is less than Recieving end Voltage (VR). Ferranti Effect is due to charging current Ic of the line. In medium Transmission lines; At No-Load,   Hence, Recieving end Voltage is more than sending end voltage. This is Ferranti Effect. This is also show that Ferranti Effect depends on the frequency and Electrical Length of the line. Now Let's see; At Load condition, Here, we saw that, No Ferranti Effect occurs at Load condition. **Ferranti Effect is more dominanting in communication Lines.** ## Elimination of Ferranti Effect: --To eliminate/nullify Ferranti Effect, we need inductor parallel to the capacitor.

Quality Factor Quality Factor describes the energy storage capability of and Capacitor in RLC circuit. It's also called Q factor. Series RLC Resonance circuit:  Q[L] = 2π * {(Energy stored by an Inductor)/(Energy dissipated by R per cycle)} Q[C] = 2π * {( Energy stored by capacitor)/(Energy dissipated by R per cycle)} Energy stored by inductor = 1/2 LIo^2 Energy stored by capacitor= 1/2 CVo^2 Where, Vo and Io = peak value) Energy dissipated by R per cycle = {1/2 (Io^2 * R)}*To  Now,  Q[L] = 2π * {(1/2 LIo^2) / (1/2 Io^2*R)*To} or, Q[L] = 2π /To * (L/R) or, Q[L] = Wo*(L/R) = XL/R = IXL/IR V=VL/VR Q[L] = VL /V = WoL/ R = 1/R * √(L/C) ------(1) And, Q[C] = 2π * {(1/2 CVo^2) / (1/2 Io^2*R)*To} or, Q[C] =  2π /To * (CVo^2/Io^2R) or, Q[C] = Wo * {( C * Io^2 * Xc)/(Io^2*R) or, Q[C] = 1/(WoRC) = Xc/R = Vc/VR Q[C] = Vc/V = 1/(WoRC) = 1/ R *√(L/C) -----(2) From eqn(1) and eqn(2); we can says that, Q[L] = Q[C] = 1/ R * √(L/C) = Q[S] Where, Q[S] = Q- factor in series RLC Resonance circuit Band

Power factor is the Ratio of Active power(P) to Apparent power(S). Mathematically, Cos(phi) = P / S But, S = P + jQ Where, P = Active power =VI Cos(phi) And Q = Reactive power= VI sin(phi)  or, Cos(phi) = VICos(Phi) / VI  Power factor = Cos(phi) Simply,we can define; Power factor means the utilisation of useful power from total power. Best way to understand power factor: In Series connection, Let's take phasor diagram of RL series circuit, From above phasor diagram;we can define, Power factor describes the direction of resultant current with respect to resultant voltage.   --In case of Leading power factor, Resultant current will lead from resultant Voltage. --In case of lagging power factor, Resultant current will lag from Resultant Voltage. Cos(phi) = VR / V = I.R / V  = (I/V) * R Cos(phi) = {(Resultant current / Resultant Voltage)}* R Cos(phi) = VR / V = I*R / I*Z = R/Z    In parallel connection, Let's take phasor diagram of RL parallel circuit, From above phasor diagram; we

Reactive Power Reactive power is used to control voltage over transmission line or in power systems network. Mathematically, Reactive Power is product of volage and current with sin(phi).        Q = VI sin(phi) -----------(1) Here, we observed that from eq.(1), Reactive Power depends upon flux (phi). And We have,   V = E1 = 4.44 Nf(phi) ----------(2)     Where, phi = magnetic flux(Weber)                     N  = No. of turns                     f   = freuency(Hz) From eqn(2), We can says that, voltage depend upon flux. By this way we can say that, Reactive Power depends upon voltage. In case of synchronous machine: Over excitation ---> Over flux ---> Over R.P Need of Reactive Power : Voltage control in power system is important for proper operation for electrical devices/elements to prevent from damage such as :  -To reduces Transmission lines losses -To mantain the ability of system and prevent Voltage collapse. -Over heating of Electrical machine - Reactive Power (VARs) is used