Determination of the ABCD, parameter for a Short and Medium Transmission Line.

Experiment No.: – 03

Aim of the Experiment: –

Determination of the ABCD, parameter for a Short and Medium Transmission Line.

Apparatus Required: –

Sl. No.NameSpecificationQuantity
1Transmission Line section6 nos.
2Three-Phase Auto-transformer1 no.
3Digital Multifunction Meter2 nos.
4Connecting Wire Patch cordAs per required
Table No. 3.1

Circuit Diagram: –

fig. 3.1: Short transmission line
fig. 3.2: Medium transmission line

Theory: –

Transmission lines having length lesser than 80km and operating voltage lower than 20kV is known as short transmission lines. Due to smaller distance and lower line voltage, the capacitance effects are extremely small and therefore, can be neglected. So the performance of the short transmission line depends upon the resistance and inductance of the line.

Transmission lines having length between 80km to 200km and line voltage between 20kV to 100kV is known as medium transmission lines. Due to the length and voltage of the line the charging current is appreciable and therefore, capacitance effect can not be ignored. Though the capacitance is uniformly distributed over the entire length of the line, yet the capacitance may be assumed to be concentrated at one or more point.

ABCD parameters is also known as transmission line parameters.

\[\color\red{V_S = AV_R + BI_R}\] \[\color\red{I_S = CV_R + DI_R}\] \[\color\green{if\; receiving\; end\; is\; open\; circuit\; IR\;= \;0,\;} \] \[\color\green{so,}\] \[\color\red{ A = \dfrac{V_S}{V_R}\: {unit\: less}}\] \[ \color\red{C = \dfrac{I_S}{V_R}\: mho}\] \[\color\green{if \;receiving\; end \;is \;short\; circuit\; Vs\; =\; 0,}\] \[\color\green{ so,}\] \[ \color\red{B = \dfrac{V_S}{I_R}\: ohm.}\] \[ \color\red{D =\dfrac{ I_S}{I_R}\: unit\: less}\]

Procedures: –

  1. Connect all the apparatus as per circuit diagram properly.
  2. Before switching ON main supply verify the connection with concern faculty and keep the auto-transformer at minimum output voltage.
  3. Now Slowly increase the supply voltage to 200 V at sending end side keeping the receiving end side is in open circuit and note the readings as per observation table.
  4. Now Slowly increase the supply current to 1A at sending end side keeping the receiving end side is in short circuit and note the readings as per observation table.
  5. Calculate the A,B,C and D parameters of the transmission line as per formula.

Observation Table: –

For Short Transmission Line:

Sl. No.Sending end Voltage (Vs) in VoltsSending end Current (Is) in Amps.Receiving end Voltage (Vs) in VoltsReceiving end Current (Is) in Amps.Remarks
1Open circuit
2Short circuit
Table No. 3.2

For Medium Transmission Line:

Sl. No.Sending end Voltage (Vs) in VoltsSending end Current (Is) in Amps.Receiving end Voltage (Vs) in VoltsReceiving end Current (Is) in Amps.Receiving end Current (Is) in Amps.Remarks
1Open circuit
2Short circuit
Table No. 3.3

Calculation: –

\[\color\red{A = \dfrac{V_S}{V_R}}\] \[\color\red{B = \dfrac{V_S}{I_R}}\] \[\color\red{C = \dfrac{I_S}{V_R}}\] \[\color\red{D = \dfrac{I_S}{I_R}}\]

Conclusion: –

To be written by student.

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