Innovation-Section: Test-run for uprating a 220 kV OHL to 380 kV using insulated cross-arms and coated conductors

摘要

Different approaches to strengthen the transmission network for increasing load flows are used. One strategic principle is the "optimization before extension", which means applying methods which make comprehensive reconstructions redundant. A possibility to increase the capacity of an existing overhead line is the uprating of the voltage level. Such a voltage uprate - using existing assets and not requiring a new line corridor - is cost- and time efficient and gains more public acceptance. The challenge is that the increased voltage level causes higher electric fields resulting in possibly higher corona noise. The paper presents the solutions and innovations that were developed and tested to uprate an existing 220 kV overhead line (OHL) to 380 kV. In the project called "innovation-section" methods for uprating lines from 220 kV to 380 kV are implemented. This "innovation-section" is a 1,2 km long part of an existing 380 kV-line in Austria, with three suspension towers. The section is being used for a test-run of two technical innovations which are newly developed insulated cross-arms and conductors with a special construction and a treated surface. When uprating from 220 kV to 380 kV the existing ton-style lattice steel towers has to be converted to a new type of tower ensuring the clearances which are needed for the higher voltage level. The solution is an insulated cross-arm. In contrast to the well-known standard lattice steel cross arm in combination with suspension strings, insulators are directly connected to the tower's body as horizontal Vee. The new suspension was mechanically and electrically type tested with a special focus on low corona extinction voltage. As audible noise (AN) is one of the main aspects when increasing voltage, new conductors were developed to reduce corona noise. Special measures are taken to increase the diameter of the new conductors, without increasing mechanical forces on the existing towers and keeping the same current capacity. Moreover a hydrophilic coating is applied. According to first laboratory test results a noise reduction of approx. 10 dB(A) is expected compared to untreated standard conductors. The components which are necessary for the uprating have been developed and tested successfully.