Why seres capacitors are used in transmission lines?

Answer 1

A poor power factor (due to large reactive loads) in a transmission system will reduce the voltage on local bus bars. Typically, especially for industrial facilities, there will be a large inductive component to the system loads, by installing shunt capacitors in close proximity to these loads the inductive component is effectively cancelled out, allowing the transmission lines to carry greater real power.

[Once the capacitors are charged the reactive power demand of the inductive load is fulfilled by the charge/discharge cycle of the capacitors rather than by long-distance transmission of reactive power].

Answer 2

Capacitors are connected in series with some lines (series compensated lines) and in parallel. Capacitors in parallel are used to prop up the voltage at that location by injecting reactive power onto the grid. Capacitors in series are used to cancel out some of the inductance of the line, which allows for more power to be transported through the line.

Capacitors at load centers are often used for power factor correction, and are connected in parallel (line to ground). To achieve efficiency in a power delivery system it is most efficient to have the current and voltage in phase. Often the load is inductive hence the current lags the voltage (due to motors etc.). Capacitors are switched in and out of the transmission system to counteract this effect.

Answer 3

Capacitor banks are used to prop up voltage on weak systems (where weak is relative to load). Adding shunt capacitors causees the voltage to go up, just like adding shunt inductors pulls the voltage down.

Answer 4

Capacitors can be used to decrease the inductance of power lines (series compensation), and for voltage support (capacitors are put in parallel with the system).

Answer 5

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