
143Transients on Overhead Lines
This voltage is called the “switching (surge) overvoltage,” which reaches 2
pu (per unit voltage = V/E) in a single lossless line:
Perunit voltagepu)
Appliedsource(steady-state volta
(
)
=
Voltage
gge
(2.1)
In reality, the voltage is reduced to less than 2 pu because of the travel-
ing-wave attenuation from the sending end to the remote end caused by a
resistance in the conductor (see Section 1.6.4.4). However, a real transmission
line has three phases, and a switching operation involves switching of three
phase switches. Then, a switching surge on one phase induces a switching
surge on the other phases. In addition, trav ...