Reducing air clearance requirements for voltage uprating of overhead line by use of line surge arresters
While uprating an overhead line to a higher voltage level, it is often difficult to achieve the required clearance level for the uprated structure. Use of Transmission Line Arresters (TLAs) is an effective technique in controlling overvoltages and thereby, achieving the required clearance margin. In this paper, suitability of this technique in reducing the clearance margin is discussed. A case study on uprating an existing 275 kV overhead line to 400 kV is investigated here.
Voltage uprating of overhead transmission lines
In recent years, uprating of existing overhead power line has become a popular option for electric utilities to address increasing demand for power. Uprating overhead line by increasing voltage allows considerable increase in power transfer capability. This paper initially examines technical issues and conventional methods of uprating the voltage of overhead transmission lines. It then considers a case of existing 275kV line in L3 tower to analyse these issues and propose appropriate process for its possible uprating to 400kV system. In this case, phase-to-earth clearance was found to be a key issue for voltage uprating. Application of line surge arresters along the line was proposed for controlling overvoltage thereby reducing the minimum required clearance for 400kV system.
Application of 800 kV SF6 Dead Tank Circuit Breaker with Transmission Line Surge Arrester to Control Switching Transient
An 800 kV metal oxide transmission line surge arrester (TLA) has been developed, installed, and tested on the AEP 765 kV Marysville to Kammer transmission line. The purpose of this transmission line surge arrester (TLA) is to pave the way for the development, construction, and application of an 800 kV SF6 dead tank circuit breaker without closing resistors and free standing current transformers at AEP's 800 kV Orange station. The maximum design operating voltage is 800 kV, and 765 kV is the nominal operating voltage. Successful field test results of the TLA's ability to limit switching overvoltage emanating from circuit breaker operation to below the transmission line switching withstand are given. Successful test results of the 800 kV dead tank circuit breaker design dielectric test are given.