The challenge for busbar disconnectors of gas insulated switchgear (GIS) in a 420kV mixed technology (Hybrid) substation (MTS)

SUMMARY The demand for electrical energy in the southern pa rt of Germany, with environmentally friendly power generation of increasing on-shore an d especially off-shore wind farms in the northern part of Germany, puts high requirements on existing power transmission lines and substations in the 420kV range. The existing 420kV substations have to be modified for the higher energy transmission, from the northern to th e southern part of Germany. Transmission lines will be operated on their current limits (tra nsmission loads up to 3000 MVA) which cause feeder currents up to 4000A in the substation s. This brings attention to the capability of the busbar disconnectors and their behaviour during busbar-transfer operations. In the product related international standard IEC 6 2271-102 (2001) [1] the related bus-transfer voltage (transfer voltage) for 420kV Air Insulated Substations (AIS) is given with 300V, while 20V is standard for Gas Insulated Substations (GIS). For the rated bus-transfer current, one common value for air-insulated and gas-insulate d disconnectors is given with 1600A. This value considers a current distribution during commutation from one busbar to the other busbar of 80%/20% and therefore, a feeder current u p to 2000A. The 1600A was chosen as being typically the highest current which can be sw itched, although the rated currents of the disconnectors may be substantially higher. These given values for the bus-transfer voltage are not sufficient for the case in which an AISsubstation is modified by using the existing AIS-bu sbars and installing GIS bays. These Mixed-Technology Substations (MTS) are used due to the higher number of bays which can be installed on an existing footprint. Additionally , a greater flexibility in the substation layouts can be achieved. Investigated substation co nfigurations, which authorize the operator for bus-transfer operations, are double- or multi-b usbar arrangements or substations using a transfer busbar for maintenance. The distance, resp ectively the impedance, of the AIS busbar configuration over the closed coupling bay is very important for commutation. In addition, the feeder current and the load situation on the busbar , define the transfer voltage on the disconnector before, during, and after the bus-tran sfer operation. 21, rue d’Artois, F-75008 PARIS B3-107