The live line is insulated from the earth, and electrostatic induction can occur between it and the earth to form a capacitor. Similar to a flat capacitor. Theoretically, there is a capacitive effect between any two insulated conductors.
Assume that the terminal voltage at the head end of the line is U 1, U2, XC, XL and R. XL>& gtr, R can be ignored, for long-distance transmission lines, xc >;; The phase difference between the voltage on XL and C and the voltage on L is 180. The power supply voltage US≈UC-UL, and the voltage drop on the capacitor is greater than the power supply voltage, so the terminal voltage U2 > U 1.
In order to weaken the influence of "power frequency voltage rise", shunt reactors are often installed in the middle or end of long-distance transmission lines, and the capacitive charging power on the lines is compensated by the inductive reactive power of the reactors to reduce the power frequency voltage rise.