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Protection of complicated bus arrangements using centralized low impedance intelligent electronic de

Protection of complicated bus arrangements using centralized low impedance intelligent electronic device

CIGRE Journal

In this paper, protection of a complicated bus arrangement with dual bus coupler and bus sectionalizer using low impedance differential protection applicable for very high voltages like 220kV and 400kV is discussed. In many power generation stations, several operational procedures are implemented to utilize the transfer bus as main bus and to facilitate maintenance of circuit breakers and current transformers (in each section) without shutting down the bay(s). Owing to this fact, the complications in operational philosophy have thrown challenges for the bus bar protection implementation.

Author(s): Dinesh Babu, Jorge Cardinas, M.V.Gopalan, Bala Vinayagam
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In this paper, protection of a complicated bus arrangement with dual bus coupler and bus sectionalizer using low impedance differential protection applicable for very high voltages like 220kV and 400kV is discussed. In many power generation stations, several operational procedures are implemented to utilize the transfer bus as main bus and to facilitate maintenance of circuit breakers and current transformers (in each section) without shutting down the bay(s). Owing to this fact, the complications in operational philosophy have thrown challenges for the bus bar protection implementation. Many bus topologies allow any one of the main busses available in the station to be used as an auxiliary bus. In such system, pre-defined precautions and procedures are made as guidelines, which are followed before assigning any bus as an auxiliary bus. The procedure involves, shifting of links, changing rotary switches, insertion of test block and so on thereby causing unreliable operation. This kind of unreliable operations or inadvertent procedural lapse may result in isolation of the bus bar from the grid due to unpredictable operation of bus bar protection relay which is a commonly occurring phenomenon due to manual mistakes. With the sophisticated configuration and implementation of logics in modern intelligent electronic devices, the cumbersome procedures are totally eliminated and the operator is free to choose the transfer arrangement without compromising the protection need of a bus differential system for a reliable operation. This paper deals with the security logics for such special scenarios, implemented in bus bar protection relay (GE make B90) to ensure system stability and eliminate all the special operational precautions / procedure.