Single-phase grounding fault detection and positioning method and system for low-current grounding power distribution network

Abstract

Power distribution networks of countries such as China and the like mainly adopt a low-current grounding method. Most faults of the low-current grounding power distribution networks are single-phase high-resistance grounding faults and low amplitude of transient capacitive current signals, short duration, and high detection difficulty are generated in a fault process so that an effective fault detection and positioning system is lacked. The invention discloses a fault detection and positioning method and system for a low-current grounding power distribution network. The system includes feeder line monitoring units, a communication terminal and a system master station. A feeder line monitoring unit wirelessly and synchronously triggers the other two phases to transmit data after a suspected grounding fault is detected. The system master station and the communication terminal adopt GPS time service. The communication terminal and the feeder line monitoring units carry out time hack through a time division multiplexing wireless communication network. The system master station collects three-phase feeder line monitoring unit data at a plurality of points through the communication terminal and detects and positions a grounding fault according to calculated zero-sequence voltage and zero-sequence current and issues a fault signal to feeder line monitoring units in front of a fault point on a fault phase so as to carry out fault indication.

Description

technical field [0001] The present invention generally relates to the fault detection and location of feeder automation part in power distribution automation, especially the method and system for single-phase ground fault detection and location of feeder with small current grounding distribution network. Background technique [0002] In the power system, the power comes from the power plant, and is transmitted to the load side through the high-voltage or ultra-high-voltage transmission network, and then the power is distributed to users of different voltage levels by the network with a lower voltage level, which mainly plays the role of power distribution in the power grid. The network is called the distribution network, referred to as the distribution network. In the power system, the distribution network is a short board that affects the reliability of power supply for users. The investment in the distribution network is relatively insufficient, and the level of automatio...

AI Technical Summary

Problems solved by technology

[0005] However, after a single-phase ground fault occurs, the single-phase ground fault point must be found as soon as possible to eliminate the fault.

Otherwise, the overvoltage generated by the ground fault can cause power system accidents such as cable explosion, voltage transformer PT burnout, and busbar burnout.

At the same time, if the grounding line is operated as a normal line for a long time, it will bring great hidden dangers to the safety of local residents and livestock.

In 2010, long-term operation of single-phase high-resistance grounding of power distribution overhead lines occurred in Hechi City, Guangxi, resulting in personal electric shock and death

[0020] (3) The zero-sequence reactive power of the fault line is negative;

[0021] (4) The zero-sequence active power of the fault line is large;

[0022] (5) The 5th harmonic current of the faulty line is large and reversed with that of the non-faulty line;

[0023] (6) The negative sequence current of the fault line is large

[0031] (2) The location of the ground fault cannot be accurately located

[0038] (2) Signal sources and other equipment require additional investment and construction, and power outages are required during construction;

[0039] (3) For common grounding faults with a grounding resistance of more than 800 ohms, it is impossible to generate a large enough coded signal current to activate the fault indicator, and it is impossible to detect high-resistance grounding faults;

[0040] (4) Unable to detect instantaneous ground fault

[0044] (1) A switch needs to be installed, and there must be a CT and PT inside the switch, and the investment in the switch and FTU is huge;

[0045] (2) It is difficult to capture small current transient signals when measuring CT, and high current will be saturated. When three-phase superposition generates zero sequence, it will cause large errors due to three-phase imbalance, and it is difficult to detect high-impedance grounding;

[0046] (3) PT has a ferromagnetic resonance problem;

[0047] (4) The installation of switches and FTU requires line power outage construction;

[0048] (5) Only the section between the switches can be located, and more accurate positioning cannot be achieved;

[0049] (6) It is very difficult to provide power to FTU on the overhead line, which affects its installation and normal operation

[0050] At present, the small current grounding system, especially the neutral point through the arc suppression coil grounding system, lacks effective ground fault detection methods and equipment, and cannot quickly detect the ground fault and indicate the grounding position

Many power supply departments are still using manual investigation methods such as pulling wires to locate ground faults. These methods have a low degree of automation, are difficult to implement, and have low efficiency. They cannot meet the requirements of the power system to continue to improve the reliability of power supply. one of the main difficulties of sex

Images