Surge Impedance Loading (SIL)
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
In power system work, the characteristic impedance is sometimes referred as surge impedance. It is defined as square root of Z/Y where Z = Series impedance of line = R + jX Y - Shunt admittance of line = G + jB
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
In the analysis of short and medium lines we were assuming that the capacitance associated with the line is lumped or concentrated at one or more point although in actual practice it is distributed along the length of line.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
Review Questions : 1. State equation for long transmission line of VS and IS in term of Vr and Ir and line parameter per unit length. Derive this hyperbolic equation and discuss i) Characteristics constant ii) Propagation constant 2. Derive expressions for the generalised A, B, C, D constants of a long transmission line by rigorous method cf analysis. 3. A3 phase transmission line 200 km long has the following constants Resistance/phase/km = 0.16 Ω, Reactance/phase/km = 0.25 Ω Shunt admittance/phase/km = 1.5 × 10-6 mho Calculate by rigorous method the sending end voltage and current when line is delivering load of 20 MW at 0.8 p.f. lagging. The receiving end voltage is kept at 110 kV. 4. Perform the analysis of long transmission lines using RIGOROUS method. 5. Explain the procedure for determining the transmission efficiency and voltage regulation of a long transmission line. AU May-05, Dec.-05, Marks 8 current relations in terms of receiving end 6. Derive for a long line the sending end voltage and voltage and current and the parameters of the line.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
The transmission system can also be assumed to be a four terminal network with two input terminals where power enters the network and two output terminals where power leaves the network.
End Condenser - Nominal T, π Method
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
The medium transmission lines are having length lying between 50 to 150 km and they operate at voltage greater than 20 kV.
Modelling and Performance of Transmission Lines
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
1. Explain the influence of power factor on the performance of a transmission line. 2. A single phase overhead transmission line delivers 1100 kW at 11 kV at 0.8 p.f. lagging. The total resistance and inductive reactance of the line are 8 and 16 respectively. Determine i) Sending end voltage ii) Sending end power factor iii) Transmission efficiency iv) Percentage regulation. [Ans : 13.038 kV 4.398,0.7518 lagging, 89.79 %, 18.52 %] 3. An overhead 3 phase transmission line delivers 3000 kW at a 0.8 pfl lagging to a load. The resistance and reactance of each conductor is 4 and 6 respectively. If the sending end voltage is 33 kV, determine i) Sending end voltage ii) Transmission efficiency. [Ans.: 31.96 kV, 99.24 %] 4. A three phase, 11 kV, 50 Hz, transmission line 10 km long delivers a load of 5 MW at 0.8 pfl lag at the far end. The resistance and reactance per phase, per km are 0.1 and 0.2 ohm respectively. Find sending end voltage, current and pfl Also draw the phasor diagram. Treat the line as a short AU : Oct.-96 [Ans.: 7.01 kV, 328.03 A, 0.7711 lag] 5. A 3-phase 5 km long transmission line, having resistance of 0.5 Ω / km and inductance of 1.76 mH/km is delivering power at 0.8 p.f. lagging. The receiving end voltage is 32 kV. If the supply end voltage is 33 kV, 50 Hz find 1) Line current 2) Regulation and 3) Efficiency of the transmission line. [Ans.: 31.108 A, 3.156 %, 98.44 %] 6. Derive expressions for regulation and efficiency of a short transmission line. Draw required circuit and phasor diagram. 7. Draw the phasor representation of short transmission line.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
In the analysis of short transmission lines, the capacitive effects are small and neglected. The resistance and inductance of the line are only taken into consideration.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
In the analysis of short transmission lines, the capacitive effects are small and neglected. The resistance and inductance of the line are only taken into consideration.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
In case of short transmission lines, the capacitive effects are small and neglected with some loss in the accuracy.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
The voltage regulation and transmission efficiency are the most important terms while analysing the performance of transmission line.
Modelling and Performance of Transmission Lines
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
The design and operation of a transmission line is greatly influenced by the voltage drop, line losses and efficiency of transmission system.
Subject and UNIT: Transmission and Distribution: Unit II: (a) Modelling and Performance of Transmission Lines
The parameters R, L and C associated with any transmission line are distributed uniformly along the whole length of line.