Labrador-Island Link ±350kV HVDC Transmission Scheme - Key Design Aspects: HVDC and Power Electronic Technology and Developments

摘要

Labrador-Island Link (LIL) HVDC Project is a ±350 kV, 900MW bipole scheme based on Line Commutated Converter (LCC) technology. The scheme will deliver power from the hydroelectric generation facilities which are located at Muskrat Falls, Labrador to Soldiers Pond, which is located on the Avalon Peninsula of Newfoundland in Canada. The DC connection comprises of two overhead line sections (407km and 661km) on either side of a DC submarine cable section (32km). The DC neutral is connected to sea electrodes via electrode lines of 400km and 12km length from Muskrat Falls and Soldiers Pond converter stations respectively. Each converter pole is independently designed with a continuous overload capability of 675MW and a short time overload capability of 900MW. The transmission of the overload during monopole operation requires operation of the scheme with the DC cables connected in parallel. The switchgear arrangements at each of the DC cable transition compounds is suitably designed to enable online paralleling and offline de-paralleling of the DC submarine cables. In addition to normal monopole and bipole circuit configurations, the LIL HVDC project is required to operate in loop power flow mode. Loop power flow mode results in circulation of up to rated current in the DC circuit to prevent ice adhesion on the overhead DC lines. In this mode of operation the scheme can appear as a minimal load (scheme losses) on the AC system. Design considerations for this operating mode are elaborated in this paper. This paper presents the design solution provided by ALSTOM GRID and discusses the key design challenges. The paper also details the design considerations for the interface between the converter transformer and the valve hall and for equipment installed within the outdoor DC cable transition compounds where the environmental conditions are harsh.