Self-supply microprocessor protection device with current trip

Abstract

The invention relates to a self-supply microprocessor protection device. The self-supply microprocessor protection device comprises a CT sampling loop, wherein the CT sampling loop comprises an A-phase CT sampling loop, the A-phase CT sampling loop comprises a current transformer 2LHa, a current transformer CTa and a switch connection point JA2, the switch connection point JA2 is connected in series with the current transformers, the A-phase CT sampling loop also comprises an A-phase transducer Ta and an overcurrent trip protection circuit, the overcurrent trip protection circuit is connectedin parallel with the switch connection point JA2, the overcurrent trip protection circuit comprises an overcurrent tripper Y7 and a switch connection point JA1, the switch connection point JA1 is connected in series with the overcurrent tripper Y7. When a short-circuit accident occurs in a power supply system, the A-phase transducer Ta is used for acquiring current energy of the short-circuit accident and converting to the microprocessor protection device for power supply, so that the microprocessor protection device can normally work, the accident is detected and distinguished, a protection action command is started, a power-grid fault point is removed, and protection failure of the microprocessor protection device caused by excessively low voltage of an external working power supply or power failure is prevented.

Description

technical field [0001] The invention relates to the technical field of microcomputer protection, in particular to a self-powered microcomputer protection device with current tripping. Background technique [0002] In the power system industry, the protection, measurement and control of high-voltage substation equipment with a power supply load greater than 400KVA capacity are realized by microcomputer protection devices in substations with a voltage level of 10KV and above. Among them, the 10KV switching stations under the jurisdiction of the State Grid and the substation equipment with a voltage level of 35KV and above are equipped with a special DC power supply panel (DC110V or DC220V) as the working power supply of the microcomputer protection device and switchgear, but in some small-scale 10KV Distribution transformers, box transformers, and ring network power distribution equipment do not use DC power panels as the working power supply due to limited space and investmen...

AI Technical Summary

Problems solved by technology

However, some 10KV small and medium-sized distribution transformers, box transformers, and ring network power distribution equipment do not use DC power screens as working power sources due to small space constraints and investment savings, but directly use 10KV busbar voltage transformers to directly step down to AC 220V as The working power of the device

If the AC220V power supply loses power or is unstable, it will affect the reliability of the system protection equipment

Although the AC working power supply is economical, convenient and practical, the stability and reliability of the power supply cannot be guaranteed. When the voltage transformer fuse is blown, it will cause the secondary voltage phase loss, power loss or line voltage drop, etc., especially when the system has a large Power supply accidents (such as 10KV bus short circuit, phase-to-phase short circuit and near-point short circuit accidents), will cause the system 10KV bus voltage to drop, the secondary side voltage of PT is unstable, and the AC220V working power supply voltage value sometimes drops to 50%. Below, the protection of secondary protection equipment such as microcomputer devices will fail due to low working power, which will not be effective and the faulty line will be cut off.

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