Effect of capacitance on performance of the short transmission lines i...
Short Transmission Line:When the length of the overhead transmission line is up to about 50 km and the line voltage is comparatively up to 20 kV.
Due to smaller lengths and lower voltage, the capacitance effect is small and maybe neglected, and hence Shunt admittance too.
Considered a short transmission line of resistance R and Reactance XL over a length.
V
s is the sending end voltage
V
R is the receiving end voltage
I is the load current.
cos ϕ
R is receiving end power factor
and, cos ϕ
s is sending end power factor
The phasor diagram of the system can be drawn by taking load current as a reference,
From the phasor,
(OC)
2 = (OD)
2 + (DC)
2(OC)
2 = (OE + ED)
2 + (DB + BC)
2V
2S = (V
R cos ϕ
R + IR)
2 + (V
R sin ϕ
R + IX
L)
2
Effect of capacitance on performance of the short transmission lines i...
Effect of capacitance on performance of short transmission lines
Introduction:
Short transmission lines refer to power lines that are relatively shorter in length compared to long transmission lines. Capacitance is an inherent property of transmission lines and it affects their performance in various ways. However, when it comes to short transmission lines, the effect of capacitance on their performance is extremely small. This can be attributed to low operating voltage and smaller length.
Explanation:
1. Capacitance and its impact:
- Capacitance is a property of any two conductive objects separated by an insulating medium.
- In the case of transmission lines, the conductive objects are the conductors themselves, and the insulating medium is the surrounding air or insulation material.
- Capacitance exists between the conductors and between the conductors and the ground.
- The capacitance of a transmission line depends on factors such as conductor spacing, length, and dielectric constant of the insulating medium.
2. Performance of short transmission lines:
- Short transmission lines have relatively smaller lengths compared to long transmission lines.
- Due to their shorter length, the amount of capacitance in short transmission lines is relatively low.
- The effect of capacitance on the performance of a transmission line is determined by factors such as voltage drop, power factor, and impedance.
- In the case of short transmission lines, the impact of capacitance on these factors is minimal.
3. Low operating voltage:
- Short transmission lines typically operate at lower voltage levels compared to long transmission lines.
- The lower operating voltage results in a smaller charging current, which is the current required to charge the capacitance of the transmission line.
- The charging current is proportional to the capacitance and the rate of change of voltage.
- Since the operating voltage is low in short transmission lines, the charging current is also low, reducing the impact of capacitance on the overall performance.
4. Smaller length:
- The length of a transmission line affects the total amount of capacitance.
- Short transmission lines have shorter lengths, resulting in reduced capacitance.
- The smaller length of the transmission line reduces the overall effect of capacitance on performance.
Conclusion:
In conclusion, the effect of capacitance on the performance of short transmission lines is extremely small due to the combination of low operating voltage and smaller length. These factors result in a lower charging current and reduced capacitance, minimizing the impact on voltage drop, power factor, and impedance.
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