1 Introduction State Grid Corporation of the transmission and distribution equipment procurement and bidding system for the centralized management and centralized operation of major reforms. 2005 363kV and above 1550kV and equipment procurement and bidding concentrated corporate headquarters, in turn 252kV equipment in late 2006 also focused on Beijing bidding for 40.5 ~ 126kV equipment in the network of provincial company focused bidding. State Grid Corporation in 2006 also prepared and issued "110 ~ 500kV Transformer substation Typical Specification General. "
In the bidding in order to better implement correctly the typical standard, reasonably determine the equipment and technical requirements related to this article talk about the high-voltage AC Isolating switch And earthing switches used in several problems for electric power engineering design and equipment selection of sector-related professional references.
2 Isolation Switch Switching on the current bus conversion
2.1 isolation switch opening and closing of the typical operation of bus switching current
Isolation conversion Bus Switch Switching current (commonly known as the circulation), is in normal operation, with the isolation switch is open, or closed by the same level of devices and bus voltage in an electrical substation within the closed loop composed of, in order to achieve load transfer current operation.
Domestic substation wiring, the use of more of a single bus connection (Single Bus, single busbar with bypass), Double Busbar (two busbar section, double busbar with bypass), half breaker and the bridge-shaped, angular, etc. connection. Among them, two-down bus bus bus conversion operation is to open and close the most typical and popular current conditions. In addition, as a special case, a single parent and dual parent wiring out of bypass bus, half breaker maintenance bus, the bridge-shaped, T-shaped, angular connection Loop Operation, in order to avoid breaking isolating switch with a long empty home online large capacitive current and the reverse procedure: first, isolating disconnect switch, then disconnect the circuit breaker to exit load bus. At this time also experience isolation switch opening and closing bus switching current problems.
2.2 standard specifies the parameters
Our national standard GB1985-2004 "high-voltage AC disconnectors and earthing switches" in Appendix B to regulate the sexual isolation switch opening and closing are given bus switching current requirements and test methods. Air insulated disconnecting switch, bus converter rated current value should be 80% of the rated current, maximum no more than 1600A, rated voltage bus conversion selected from Table 1; test opening and closing times for the 100 operating cycles. The maximum switching current rating of not more than 1600A, as is usually rated short time withstand current is based, rather than by isolating switch rated current to choose, so long the maximum current through the isolation switch is much smaller than its rated current, so the bus switching current maximum value can be set at 1600A. In 1986, the Institute of High Voltage Electric Power Research Institute in China to make opening and closing bus isolation switch switching current technical conditions, once with a computer calculation and analysis of the internal 10 ~ 500kV Bus Connection of several typical power conversion current, results consistent with no more than 1600A requirements.
Isolation switch contacts as slow movement, in the opening and closing bus switching current arc generated when the arcing time is longer, to make contact easy to burn. In order to meet the standards required switching capability, manufacturers need to switch on the additional arc in contact isolation, so that isolation switch contact structure is more complicated. Therefore necessary to isolate two types of switches: open and close with current capacity of bus converter and do not have to open and close bus switching current capability. Design and user departments in the selection of isolation switch should be treated differently.
2.3 Double Bus in opening and closing of bus isolation switches need to change the current bus
Actual operation in the substation, under normal circumstances, the bus only Double Busbar isolating switch and wiring in the bus bypass isolation switch, it needs to open and close bus switching current; the single-bus connection of the bus disconnecting switch, bus isolation switches and a large number of access lines, isolation switch, there is no conversion to open and close bus current condition.
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