A bus protection method for CTs connected at two sides of a bus-tie switch

Abstract

A bus protection method for CTs connected at two sides of a bus-tie switch comprises a protection device for more than two sections of buses. The protection device acquires all bus voltages, all branch current and knife switch positions on a bus and CT current and switch positions at the two sides of the bus-tie switch; the protection device automatically calculates bus protection three-phase voltage, large-difference current and small-difference current of each section of bus, calculates bus tie interval differential current of the bus-tie switch itself and current of the CTs at two sides ofthe bus tie, judges whether the bus tie CTs have a line-breaking fault or not and selects a faulty bus or a bus to trip when fault occurs; and meanwhile, a bus tie interval differential protection logic is newly added, the difference current of CTs at the two sides of the bus-tie switch and the current magnitude of the CTs at the two sides of the bus-tie switch are calculated, and the bus-tie switch or the bus is selected to trip according to the bus voltage opening condition, the bus-tie switch difference current and the current magnitude at the two sides. The method is simple and reliable, and improves quickness and accuracy of protection and cutting during bus dead zone fault.

Description

technical field [0001] The invention relates to a busbar protection method connected to CTs on both sides of a busbar switch, especially for the situation that all busbars need to be cut off quickly or the busbar is disconnected first and then the faulty busbar is selected for tripping when the busbar dead zone fault is required. Background technique [0002] The principle of bus differential protection is mainly to judge the fault inside and outside the bus area according to the large difference current, and select the faulty bus to trip according to the small difference current. For the bus tie interval, usually the bus protection only connects to the CT current on one side of the bus tie switch. When a fault occurs between the switch and the CT, there is a fault that cannot be removed quickly. The bus protection first jumps to the normal bus, and then through the dead zone protection or bus tie failure. The protection then removes the fault condition. This solution has t...

AI Technical Summary

Problems solved by technology

For the bus tie interval, usually the bus protection only connects to the CT current on one side of the bus tie switch. When a fault occurs between the switch and the CT, there is a fault that cannot be removed quickly. The bus protection first jumps to the normal bus, and then through the dead zone protection or bus tie failure. Protection and then fault clearing

This solution has the characteristics of expanded fault removal range and slow fault removal time, which has a great impact on the safe and stable operation of the system

In most projects, CTs are installed on both sides of the bus coupler. At the same time, when a fault occurs between the CTs on both sides of the bus coupler, the two sections of the busbar should be cut off at the same time, but there is a lack of selectivity and flexibility.

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