MODELLING OF ELECTROMAGNETIC WAVE PROCESSES TAKING INTO ACCOUNT REACTORS WITH UNGROUNDED NEUTRALS AND OVLS IN DOUBLE-CIRCUIT LONG-DISTANCE ETL

This paper studies the effects of switching
overvoltages considering reactors with ungrounded
neutrals and non-linear overvoltage limiters (OVL) in
double-circuit long-distance power transmission lines
(ETL). In long-distance extra high voltage double-circuit
electric transmission, one of the causes of surges occurs
during line switching. Traditionally, shunting reactors
(SR) are used at both ends of lines in order to ensure
protection against switching overvoltages. However, in
long distance AC ETL it becomes difficult to limit
overvoltages by SR only, and the operation of the system
is not stable enough. The combined shunt compensation
method helps limit the switching overvoltages in long
distance double circuit lines. A combined shunt
compensation of overhead extra high voltage power lines
which contains, apart from traditional SR connected to
the power line through reactor circuit breakers, reactors
permanently connected to the line according to the star
with ungrounded neutral configuration. Using the
proposed method, calculations were made on the
switching overvoltages occurring with OVLs connected
in parallel between SR and ungrounded reactors (UR) at
the sending ends and receiving ends of double-circuit
ETL. Mathematical models of reactors with ungrounded
neutrals, OVLs and sources are developed based on the
calculation methods as part of the conducted studies.
Using the bivariate cubic spline interpolation method for
switching overvoltages, line voltage (u) and current (i)
values are calculated, and voltage change curves at the
sending ends of the line are observed