A collection method of three-phase single-cable single-phase ground current

Abstract

The invention discloses a method for acquiring the single-phase grounding current of a three-phase single cable. According to the method, the head end of a three-phase single-core cable shielding layer is connected with a zero-sequence current mutual inductor in series, the three-phase single-core cable shielding layer is grounded through the zero-sequence current mutual inductor and acquires the capacitance current through the zero-sequence current mutual inductor during single-phase grounding failure of the three-phase single-core cable, the rated voltage and the transformation ratio of the zero-sequence current mutual inductor can be selected according to the protective requirement, and the current of the zero-sequence current mutual inductor is not influenced by load current, so that the protection sensitivity is improved; and a voltage limiter is arranged at the far end of the three-phase single-core cable shielding layer, and the voltage limiter takes on low impedance and conducts the current to the ground when the voltage of the three-phase single-core cable shielding layer is increased to the limited value, so the method is high in practicability and has strong popularization and application value.

Description

technical field [0001] The invention belongs to the technical field of cable grounding current collection, and in particular relates to a method for collecting single-phase grounding current of a three-phase single cable. Background technique [0002] At present, the grounding protection fault current acquisition method adopted by the three-phase single-core power cables in domestic operation is: adopt the zero-sequence current filter method composed of three-phase CT (current transformer), figure 1 It is a schematic diagram of the principle of cable single-phase short-circuit fault current acquisition provided by the prior art. This method has the following defects: [0003] (1) The transformation ratio of the zero-sequence current filter is selected according to the line load, and the general transformation ratio is consistent with the overcurrent protection transformation ratio. When grounding, the grounding capacitor current is very small, generally tens of amperes, the...

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Problems solved by technology

When grounding, the current of the grounding capacitor is very small, generally tens of amperes, the current of the secondary side of the zero-sequence current filter is very small, and the protection sensitivity is not high

[0004] (2) The zero-sequence current filter is affected by the load current. If the load current is unbalanced in three phases, it will affect the protection sensitivity;

[0005] (3) When an external through-fault occurs, a large unbalanced current will be generated.

[0007] (5) It cannot reflect the insulation condition of single-phase power cables

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