Controlled closing on shunt reactor compensated transmission lines. I. Closing control device development

Abstract

A control device for point-on-wave closing or autoreclosing of shunt reactor compensated transmission lines for reduction of closing overvoltages is presented. The device is the first of its kind. It was put into field service successfully more than a year ago. Development aspects and basic investigations on the relevant transient switching phenomena are presented. The algorithm employed works independently of the shape of the voltage signal to be synchronized on by means of pattern recognition. Peculiarities of the hardware are high redundancy and a system to bypass the controller at any malfunction of the electronic circuits. The efficiency of the controller was verified by a combination of transient network analyser tests and EMTP simulations showing the ability of the device to suppress overvoltages. This procedure is generally recommended for future application o f control devices as a type test procedure.

Circuit-breaker requirements for alternative configurations of a 500 kV transmission system

“…That is the case reported in [4], where the design optimisation of the 550 kV, 330 km long line imposes severe limits for line switching overvoltages (1.7 pu). Controlled switching has been applied to different switching conditions in HV networks for about 10 years.…”

“…However, satisfactory technological solutions to put in practice the idea could only be developed in more recent times, thanks to the evolution of high-voltage circuit breaker designs and to the development of micro-electronic devices applied to power systems. The recently -reported experiences of the use of synchronous-switching systems have shown that these devices can be very efficient to control switching overvoltages, having thus become a powerful means at the disposition of utilities to help them meet stringent insulation coordination requirements, such as those generally especified when compact lines are to be used [4] . Accordingly, in the present study this solution has also been investigated, as a possible alternative to the use of closing resistors, generally quite onerous for EHV circuit breakers.…”

“…In the cases with PIR, a 400-ohms resistor, with a insertion time of 8 ms, has been considered. In the controlled-closing cases, the principles of a recently-developped synchronous device [4],[6], [11] have been applied. In the staggeredclosing simulations a separation of the pole-closing times of X ms has been adopted.…”

A Simple Short Circuit Analysis for Power Networks

“…The value of the rate of decrease of dielectric strength should exceed the maximum derivative of the applied voltage for proper operation of CB. The maximum pre-striking voltage is determined according to the statistical scatter of the contact's speed [6].…”

State equation based closing simulation

“…The value of the rate of decrease of dielectric strength should exceed the maximum derivative of the applied voltage for 14 proper operation of CB. The maximum pre-striking voltage is determined according to the statistical scatter of the contact's speed [6].…”