Positive Sequence Impedance Differential Protection Method for Distribution Networks Containing IBDG with Braking Characteristics

Abstract

The invention discloses a positive sequence impedance differential protection method with braking characteristic for a power distribution network containing inverter-based distributed generation (IBDG). The method comprises the following steps of acquiring a three-phase current and a three-phase voltage at a protection position to acquire positive sequence impedance; carrying out information exchange between protection at two sides through an optical fiber Ethernet or a wireless communication network; carrying out calculation of action impedance and braking impedance by a local-side protection device after acquiring positive sequence impedance information and positive sequence current amplitude information which are measured by opposite-side protection; and judging whether a protected region is a fault section or not according to an action criteria with the baking characteristic. The method is applicable to circuit protection between a bus of a substation outlet of an active power distribution network and a distributed power supplies and between the distributed power supplies, the influence of fault characteristic of IBDG and through load current on protection performance can be dealt with, and the influence of a branch load on the judgment of a fault direction during an external fault can be prevented duo to the adoption of the action criteria; and moreover, data synchronism between two ends is not needed, the requirement on communication is relatively low, and the method has relatively high transition resistance resistant capability.

Description

technical field [0001] The invention relates to the technical field of relay protection for power systems, in particular to a positive-sequence impedance differential protection method with braking characteristics suitable for the operation characteristics of an inverter-type distributed power distribution network. Background technique [0002] Feeders of medium and low voltage distribution networks are often only equipped with circuit breakers at the head end of the line and equipped with three-stage current protection. The setting calculation focuses on sensitivity, and the automatic reclosing function of the head end protection or feeder automation guarantee is selected. After the inverter-based distributed generation IBDG (inverter-based distributed generation) is connected, when the upstream line of the IBDG fails, in order to isolate the faulty line from both sides of the fault point and prevent the transient fault from developing into a permanent fault, it is necessary...

AI Technical Summary

Problems solved by technology

If random loads with different characteristics in the downstream are taken into account at the same time, the change rule of the equivalent impedance on the back side of the protection will be more complicated, and its impedance angle may exceed the fault criterion range of the positive direction of the fault component direction element, resulting in the failure of the protection.

Therefore, the adaptive current protection principle based on local information and the directional protection principle based on fault components have limited applicability in the distribution network with IBDG, and there is a possibility of misjudgment

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