What is the charging of the line?

Why it is necessary to charge the line before it is connected to 400KV grid?

 

Responding to GNRao’s 17-Apr-08 (01:26) query...

1) When a 400kV line is energized, the current taken by line-capacitance, called charging current, can be high. The charging reactive MVA is a related to: a) physical properties (e.g., length, equivalent equilateral spacing, tower configuration); b) electrical characteristics (e.g., conductor material, diameter, # per phase); and c) the square of the applied voltage!

2) It is necessary to "charge" the line by using a source whose voltage can be increased slowly! This procedure avoids the sudden application of a large capacitive load to the source.

3) Although not requested, you might find the following formula useful in estimating charging reactive MVA per unit-length of a typical transmission line:

MVAr(c)/mile = (5.00x10^6)x(kV)^2, or MVAr(c)/km = (3.11x10^6)x(kV)^2,

Regards, Phil Corso