Digitized small current grounding line selection method

Abstract

The invention discloses a digitized small current grounding line selection method, and the method comprises the following steps: an acquisition output device completes sampling of three-phase currentand zero sequence current of each line; step 2, the acquisition output device completes judgement of zero sequence CT polarity and modification of zero sequence current sampled data of each line, andsends the data to a line selection device through point-to-point transmission by optical fibers based on an IEC60044-8 communication protocol; step 3, the line selection device receives the sampled data of each line and completes synchronization processing; step 4, the data line selection device subjected to synchronization processing selects out a faulty line through comprehensive analysis and judgement by a transient algorithm, and trips to isolate the fault through the line acquisition output device.

Description

Technical field [0001] The invention relates to a grounding line selection method for power system transmission and distribution, in particular to a line selection method for a small current grounding system. Background technique [0002] For systems with a voltage level of 3-66kV in my country's power grid, the neutral point generally adopts low-current grounding, including ungrounded neutral, grounded through arc suppression coils, and grounded through high resistance, which is also called neutral point ineffective grounding. The characteristic of the small current grounding system is that when a single-phase grounding fault occurs, it can run for 1-2 hours with the fault. Therefore, the reliability of the system operation is improved. However, when a single-phase ground fault occurs, the voltage of the non-faulty phase will rise to the line voltage, and long-term operation with faults will cause the weak links of the insulation in the system to be easily broken down, resulting...

AI Technical Summary

Problems solved by technology

[0003] When a single-phase ground fault occurs in a low-current grounding system, the short-circuit current is small and the fault characteristics are not obvious. At present, all kinds of devices usually use the phase comparison method as one of the main line selection methods, that is, by comparing the phases of the zero-sequence current of each line to find the difference for fault line selection, but the premise of the phase comparison method It is required that the polarity of the zero-sequence CT of each line must be the same, but there is a problem that the polarity of the zero-sequence CT is difficult to verify on site, which leads to restrictions on the line selection device based on the phase comparison method; moreover, there are many conventional substation outgoing line intervals. The grounding line selection device needs to be connected to a large number of secondary cables, the construction volume is large, and there are problems such as the failure of real-time alarms when the secondary cables are disconnected or falsely connected.

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