Power distribution network's low voltage fault detection instrument and detection method

Abstract

The invention provides a power distribution network's low voltage fault detection instrument and detection method. The system consists mainly of a power supply part and a detection part. The power supply part uses a storage battery as its power supply; and the power is converted by an inverter into alternating current to be outputted. The detection part comprises converting the 220V voltage outputted from the power supply part into two shifts through a conversion bipolar switch before being outputted as 220V output of voltage shift and output of current shift. The method comprises: first, determining the type of a fault; determining whether there exists a fault or not through the exertion of voltage on a line and the feedback information from the line; in case of the generation of the maximum value of instant current if there exists a short circuit on the detected line, or rather the detected line impedance stands at zero, determining that fault exists on the line and that further detection is required; under the premise that the fault is determined, exerting a current value with certain magnitude onto the detected line continuously; using a clip type ammeter to search the flow direction and position of current; and utilizing the isolation function of an air switch to accurately spot the section of the line with the fault; and isolating and recovering the section of line with the fault.

Description

technical field [0001] The invention relates to a distribution network low-voltage fault detector and a detection method, belonging to the technical field of power grid fault detection. Background technique [0002] In recent years, the construction investment of my country's distribution network (hereinafter referred to as distribution network) has been continuously increased, and the development of distribution network has achieved remarkable results. However, there is still a gap between the power supply level and the international advanced level, and the quality of power supply needs to be improved. Nowadays, power accidents are mainly concentrated in the distribution network, of which 0.4 kV low-voltage network faults account for 90%. Statistics show that 80% of the power company's emergency repair efforts are used to deal with 20% of the electricity consumption of electricity users. [0003] There are various types of low-voltage faults in the distribution network. So...

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Problems solved by technology

[0005] (1) Short circuit fault, the short circuit between the phase wire and the phase wire, the short circuit between the phase wire and the neutral wire caused by the rupture of the line insulation layer will cause severe arc or even explosion, and the air switch will be damaged due to the instantaneous large current while tripping;

[0006] (2) Leakage fault, the leakage fault is reflected in the tripping of the four-pole switch due to line leakage

There are two common leakage faults: one is the leakage between the phase wire and the protective ground wire, which is common when the user confuses the neutral wire with the protective ground wire, causing the current of the electrical appliance to pass through the protective ground wire instead of the neutral wire, resulting in imbalance; Second, the short circuit between the neutral wire and the protective ground wire causes leakage. At this time, a part of the current is shunted through the protective ground wire, resulting in an imbalance at the leakage protection switch.

Leakage faults are more concealed and harmful than other faults;

[0007] (3) Disconnection fault, the main causes are: the wire is disconnected due to the influence of uncontrollable external force, the long-term heavy load of the line causes heat and the wire is blown, and the wire or switch is disconnected due to poor contact of the electrical connection point

However, this method also has obvious disadvantages. Since the output of the megohmmeter is direct current, and there are many inductive loads in the measured line, for direct current, it is equivalent to being in the state of being in the path all the time, that is, the state of zero impedance, which is easy to interfere with the test. As a result, the emergency repair personnel misjudged; in order to accurately detect the line, it is necessary to remove all direct-connected inductive loads that may affect the detection, but it is difficult to implement on site, so this method loses its practical significance

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