Method and device for flexibly identifying residual current-type electrical fire on line

Abstract

The invention relates to a method and device for flexibly identifying residual current-type electrical fire on line. The method comprises the following steps: arranging a residual current mutual inductor in a power transmission and supply circuit of a low-voltage power distribution system; obtaining an instantaneous value irz of lumped residual current in the circuit as well as waveform which areacquired by the mutual inductor through a power supply branch residual current and other signal detection unit; and according to the characteristics such as abrupt change, discontinuity and nonlinearity of a spot-heat agglomeration residual current instantaneous value ird, separating and extracting ird from irz by adopting a modern information processing technology, and calculating an effective value Ird of ird so as to identify whether potential electrical fire danger exists according to the size of Ird. The on-line identification device consists of three parts such as a residual current signal processing unit, the power supply branch residual current and other signal detection unit and an output execution unit. By adopting the residual current-type flexible on-line electrical fire identification method and device, the features of the potential electrical fire danger caused by electric arc grounding faults can be accurately extracted, normal residual current and abnormal residual current can be correctly identified, and alarm failure and false alarm can be avoided.

Description

technical field [0001] The invention belongs to the technical field of fault monitoring and control of electric low-voltage power distribution and consumption systems, and relates to an online identification method and device for monitoring electrical fire accidents caused by arcing grounding short circuits in effective grounding systems. Background technique [0002] In an effectively grounded low-voltage power distribution (utility) system, due to material aging, accidental damage, insulation performance degradation or failure of transmission lines (cables) and electrical equipment, etc., arcing grounding short-circuit faults often occur in the system, Arcs and electric sparks with a temperature exceeding 2000°C are generated, which in turn ignite the surrounding combustibles, causing major electrical fire accidents, and seriously threatening the normal operation of the power distribution (consumption) system and the safety of people's lives and property. [0003] At prese...

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Problems solved by technology

However, the main problem of this method in practical application is that it cannot accurately distinguish and separate the point heat accumulation residual current effective value Ird contained in the lumped residual current effective value Irz (caused by arcing grounding short-circuit faults, which can cause electrical fires) and the average distributed residual current effective value Irp (generated by the normal operation of the line and electrical equipment itself, which is a function of various uncertain factors such as line running time and state, ambient temperature and humidity, load quantity and type, etc., no potential electrical fire hazard ) and the value or ratio of the two are often caused by the uncertainty of the Irp value: when there is no potential electrical fire hazard (that is, Ird is small), the aggregate residual current value Irz may be greater than the preset value due to the upward fluctuation of Irp Threshold Irg—false alarms; or when there is a potential electrical fire hazard (that is, Ird is large), and because Irp fluctuates downwards, the aggregate residual current value Irz cannot be greater than the preset threshold Irg—false alarms; especially When there is a phase angle difference between the normal and evenly distributed residual current Irp in the line or electrical equipment and the Ird generated by the arcing ground fault, the aggregated residual current value Irz amplitude after the vector superposition may sometimes be smaller than that without the fault. small, making this underreporting even more serious

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