Method for detection and indication of single-phase ground faults of small current grounding power distribution network and device

Abstract

A small current grounding mode is mainly adopted in power distribution networks in China and other countries. Most faults of a small current grounding power distribution network are single-phase high resistance ground faults, transient state capacitance current signals generated in the fault process are low in amplitude, short in time of duration and high in fault detection difficulty, and an effective fault detection and indication device is not available. The invention discloses a method for detection and indication of faults of the small current grounding power distribution network and a feeder line monitoring unit device. An electricity taking device with the power control function supplies power to feeder line monitoring units, voltage signals are collected through a capacitance type voltage sensor, current signals are collected through an electronic type current sensor, after suspected ground faults are detected, the other two phases are synchronously triggered in a wireless mode, and data are transmitted in a time division multiplexing wireless communication mode; after three-phase feeder line monitoring unit data of multiple points are gathered on system master station platform software, ground fault detection is conducted according to calculated zero-sequence voltages and calculated zero-sequence currents, and fault signals are issued to the feeder line monitoring unit in front of the fault point on the fault phase for fault indication.

Description

technical field [0001] The present invention generally relates to the fault detection and indication of feeder automation part in power distribution automation, especially the method and equipment for single-phase grounding fault detection and indication of 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 automation ...

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

[0043] The main disadvantages of the ground fault detection and location method based on networked FTU are;

[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