Hardware criterion circuit for single-phase grounding protection line selection

Abstract

A hardware criterion circuit for single-phase grounding protection line selection comprises a current sampling module and a voltage sampling module, wherein the current sampling module is connected with a first filter circuit; the voltage sampling module is connected with a second filter circuit; the first filter circuit is connected with a differentiating circuit; the second filter circuit is connected with a phase-correcting circuit; the differentiating circuit is connected with a first amplifying circuit; the phase-correcting circuit is connected with a second amplifying circuit; the first amplifying circuit is connected with a current direction judging circuit; the second amplifying circuit is connected with a voltage direction judging circuit; the current direction judging circuit and the voltage direction judging circuit are connected with a power direction judging circuit; the criterion circuit formed by the various circuits is completely triggered by hardware, instantaneous transient power can be captured, and a transient power method is adopted, so that the criterion accuracy is improved; besides, by adopting the hardware, the transient direction can be judged, a single chip microcomputer enters the sleeping mode, the energy consumption demands are reduced, a transient signal can be provided, a multiple criterion manner is supported, the criterion is no longer unitary, and the single-phase grounding judgment accuracy is further fully ensured.

Description

technical field [0001] The invention belongs to the technical field of line grounding protection, and in particular relates to a hardware criterion circuit for line selection of single-phase grounding protection. Background technique [0002] In substations, switch stations and power plants, 66 kV, 35 kV, 10 kV, 6 kV and 3 kV distribution lines are the main components of the power system; systems at these voltage levels Among them, the neutral points of transformers and generators are ungrounded or passed through the arc suppressing coil and resistance grounding for power transmission and distribution, and there are multiple output or input distribution lines connected to the busbar of the same voltage level. Most of them use aluminum or copper bars for overhead leads or high-voltage power cable leads; and the number of lines generally varies from five to six, more than a dozen or twenty to thirty, and each distribution line has many branches, which are erected in a radial m...

AI Technical Summary

Problems solved by technology

[0005] In the system, since the primary winding of the voltage transformer is connected to the bus bar of the system using Y0 wiring, when any line is single-phase grounded, a zero-sequence voltage will be generated at the triangular opening of the secondary winding, and zero-sequence voltage can be set. Sequence overvoltage alarm, but a certain line cannot be selected; when the ground is grounded, the voltage of the non-grounded phase line to the ground can rise several times the phase voltage, and when the system is accompanied by ferromagnetic resonance, the phase voltage will increase. The formation of overvoltage accelerates the aging of the insulating material of the power equipment and shortens the service life, which leads to the breakdown of the insulation equipment, and two or more phases will be grounded at the same time, resulting in a short circuit accident, which increases the damage of the power equipment.

Therefore, accidents such as explosion of voltage transformers and circuit breakers, burning of distribution transformers, and breakdown of power cables and porcelain bottles often occur in power systems; "Over-current protection" and "zero-sequence current" protection are both high-current start-up protection devices; small currents when single-phase grounding cannot drive this type of protection device to operate, so they cannot act on high-voltage switch (circuit breaker) tripping, failure Lines and non-fault lines cannot be isolated

[0006] In order to avoid the expansion of the accident, it is necessary to distinguish the faulty line from the non-faulty line in time; in the substation, switch station or power plant, if there is no reliable single-phase grounding protection line selection device installed, it is necessary to manually close the switch one by one The faulty line can only be selected through power outage trial inspection, and sometimes even all the distribution lines connected to the busbar must be switched off to find out; this will cause interruption of power supply of non-faulty lines, resulting in large-scale power outages; at the same time, it also increases the high voltage The number of operations of the switch shortens the service life, reduces the reliability and power supply capacity of the power supply; and to find the grounding point on the line, it is necessary to disconnect the numerous branch lines from the main line one by one, and then use an insulation resistance meter to measure each section. Or the insulation resistance value of each branch to the ground, the range of the fault point is manually judged

This process is very complicated and the workload is heavy; for personal safety, various safety measures need to be set up, which consumes a lot of manpower, materials and time, increases the labor intensity of electric workers, and at the same time has hidden dangers to personal safety

[0007] However, the single-phase grounding criterion of the current grounding protection line selection circuit is based on the electric field method. The single-phase grounding criterion is very single, resulting in unstable signals and easy misjudgments and missed judgments; The voltage signal has a large computational burden on the single-chip microcomputer, resulting in a transient missing signal

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