Distribution network wide-area overcurrent protection method and system

Abstract

The invention discloses a wide-area over-current protection method and system for power distribution networks. A wide-area protection main station collects information whether over-current protection devices monitor over-currents through a high-speed signal channel, which are separately mounted at the sites of individual power distribution switches in a power distribution network to be protected; if the wide-area protection main station collects the over-current information, whether an inter-phase short-circuit fault occurs inside a generalized node is judged; if the inter-phase short-circuit fault occurs inside the generalized node, the wide-area protection main station remotely controls the most upstream power distribution switch in the generalized node to trip out to clear the fault. The method and system disclosed by the invention achieve selective protection against over-currents due to inter-phase short-circuit in power distribution networks without needing time-limit cooperation, can be used for solving the difficulty of time-limit cooperation in power distribution networks and isolating inter-phase faults in power distribution networks with minimal switch on-off operation frequency, and are suitable for different types of open-loop power distribution networks.

Description

technical field [0001] The invention relates to a phase-to-phase fault protection method and system for a distribution network, in particular to a wide-area overcurrent protection method and system for a distribution network Background technique [0002] The phase-to-phase short-circuit faults of 10-35kV medium-voltage distribution network (hereinafter referred to as distribution network) include three-phase short-circuit, two-phase short-circuit and two-phase short-circuit to ground. When a phase-to-phase short circuit fault occurs in the distribution network, the resulting overcurrent will be much greater than the rated current. However, due to the short distribution line, the distribution load is distributed along the distribution line, and the distribution line passes through multiple distribution switch segments along the line, so the overcurrent protection of the distribution network lacks selectivity, and leapfrog trips often occur, resulting in power outages in the r...

AI Technical Summary

Problems solved by technology

[0009] ① Due to the large number of distribution network protection stages, it is often unable to meet the requirements of the allowable range of 0.3-0.5s delay and quick-break protection of substations

as attached figure 2 For the radial distribution network shown in , if Δt=0.15s (meeting the requirements of the spring switch), then ΔtF=0s, ΔtE=0.15s, ΔtC=0.3s, ΔtB=0.45s, ΔtA=0.6s, therefore, It is necessary to set the overcurrent protection at multiple power distribution switches to the same action time limit (ΔtF=0s, ΔtE=0s, ΔtC=0.15s, ΔtB=0.15s, ΔtA=0.3s), or some power distribution switches Not installing overcurrent protection (such as not installing at F, ΔtE=0.15s, not installing at C, ΔtB=0.15s, ΔtA=0.3s), making the protection lose selectivity

[0010] ② For such as attached image 3 In the hand-in-hand line shown in , due to the existence of double-sided power supplies, if directional overcurrent protection is adopted, there will still be too many series to meet the requirements of the allowable range of 0.3-0.5s delay and quick-break protection of the substation, for example, from right to left ΔtE=0s, ΔtD=0.15s, ΔtC=0.3s, ΔtB=0.45s, ΔtA=0.6s; coordinate from left to right ΔtA=0s, ΔtB=0.15s, ΔtC=0.3s, ΔtD=0.45s, ΔtE= 0.6s

When the hand-to-hand connection is in an abnormal operation mode, the over-current protection will lose its selectivity

[0011] ③For the distribution network with complex structure, if attached Figure 4 , 5 For the distribution network shown in , due to the many operating modes of the distribution network, it is often impossible to use the step time setting method to ensure the selectivity

On the other hand, due to the frequent transformation of the distribution network, it is difficult to calculate and update the protection value

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