Longitudinal differential protection method of power transmission line

A transmission line, longitudinal differential protection technology, applied in emergency protection circuit devices, electrical components and other directions, can solve the problem of not fully equivalent distributed parameter circuits, not suitable for the quick-action requirements of longitudinal differential protection, unsuitable for high-voltage long-distance transmission lines, etc. question

Active Publication Date: 2011-06-01
CHONGQING UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] 1. The phasor compensation algorithm, but this algorithm is based on the calculation of the steady-state phasor, so it can only compensate the capacitive current in the steady state, but cannot compensate the transient capacitive current, so it cannot fully comply with the proposal for capacitive current compensation Require
[0006] 2. Time-domain compensation algorithm, but using a π-type equivalent circuit to calculate cannot completely equivalent to the distributed parameter circuit, so it is not suitable for high-voltage long-distance transmission lines above 300km
[0007] 3. The principle of the Beryllon transmission line model algorithm is to avoid the influence of the distributed capacitive current, but the algorithm uses the phasor method for calculation. Because the calculation time of the phasor method is too long, it generally takes 20ms, and 20ms is exactly One cycle time is completely unsuitable for the quick action requirements of longitudinal differential protection, resulting in low safety and stability of the power system
[0008] For the above-mentioned compensation scheme, UHV transmission lines generally have a long distance and large distributed capacitance, and the voltage obtained to compensate this point is not the actual voltage at this point, which will not meet the quick action requirements of longitudinal differential protection , which is detrimental to the security and stability of the power system

Method used

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  • Longitudinal differential protection method of power transmission line
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  • Longitudinal differential protection method of power transmission line

Examples

Experimental program
Comparison scheme
Effect test

experiment example 1

[0161] Experimental example 1: Detection of normal working conditions inside and outside the transmission line

[0162]In the normal working state inside and outside the transmission line, the A-phase current value is collected and calculated, and a total of 40 points are sampled in each cycle, and the collected value and calculation of the first 10 points of the A-phase line current are taken The values ​​are compared in Table 1 below:

[0163] Table 1 The normal situation of the structure inside and outside the line area

[0164]

[0165]

[0166] It can be seen from Table 1 that when both the inside and outside of the transmission line are working normally, as the value of the unit number j increases, the calculated current value is closer to the collected value of the current, that is, the absolute error is getting smaller and smaller; When j=4, the relative error is lower than 1%, and the accuracy is sufficient. Therefore, if the number of units is j=4, the accurac...

experiment example 2

[0167] Experimental example 2 Detection of the state of normal operation inside the transmission line and external short circuit

[0168] When the structure in the line area is normal and the A phase outside the area is short-circuited to ground, the current value of the A phase is collected and calculated, and a total of 40 points are sampled in each cycle, and the acquisition of the first 10 points of the A phase line current is taken The values ​​and calculated values ​​are compared in Table 2 below:

[0169] Table 2 The structure of the line in the area is normal, and the ground short circuit of phase A outside the area

[0170]

[0171] It can be seen from Table 2 that in the case of a normal structure in the line area and a ground short circuit of phase A outside the area, as the value of the number of units j increases, the calculated current value is still closer to the collected value of the current , that is, the absolute error is getting smaller and smaller; whe...

experiment example 3

[0172] Experimental example 3 Detection of the internal A-phase metal grounding short circuit of the transmission line

[0173] In the case of a metal-to-ground short circuit of the internal phase A of the transmission line, the current value of the phase A is collected and calculated, and a total of 40 points are sampled in each cycle, and the collected value and calculated value of the phase A line current of the first 10 points are taken Compare the table 3 below:

[0174] Table 3 Metal grounding conditions of phase A in the line area

[0175]

[0176] It can be seen from Table 3 that in the case of a metal-to-ground short circuit of the internal phase A of the transmission line, at this time, a major change occurs in the structure of the line area, and no matter what the number of units j is, the calculated current value is significantly higher or lower than Due to the collected value of the current, the absolute error is very large, and the relative error changes sign...

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Abstract

The invention relates to a longitudinal differential protection method of a power transmission line. The method comprises the steps of: collecting input and output signals in a power transmission line; acquiring sequence components of electrical signals at an input end; calculating sequence components of electrical signals at an output end so as to acquire a function expression of three-phase electrical signals at the output end of the power transmission line and calculate the values of electrical signals in each phase at each time; comparing the values with collected values; and accurately determining whether to carry out longitudinal differential protection according to an error value. The invention has the advantages of easy operation and accurate calculation; the relative error can be completely controlled within 1% according to actual demands; the method is free from the effects of system operating methods, network structures and fluctuations of the grid frequency; the compensation to distributed capacitance current is not needed, and the difficult problem that the accuracy of a line model is affected by the distributed capacitance current is solved; because the calculated object is an instantaneous value and is a scalar, the calculation time is shortened obviously, and the longitudinal differential protection time can be completely controlled within 5ms, and thus the purpose of quickly eliminating faults is achieved, and the security and the stability of the system are improved obviously.

Description

technical field [0001] The invention relates to a method for protecting a power transmission line, in particular to a method for protecting longitudinal differences in a power transmission line. Background technique [0002] Any transmission line can be completely equivalent to a circuit model composed of infinitely many units connected in series, such as image 3 shown. Each unit is composed of resistance, inductance, capacitance and conductance, such as Figure 4 As shown, among them, after the resistance and the inductor are connected in series, one end is the input end of the unit, and the other end is the output end of the unit, and is connected to one end of the capacitor, and the other end of the capacitor is grounded, and the conductance and the capacitor are connected in parallel. [0003] In the establishment of circuit models of traditional transmission lines, technicians often ignore the factors of capacitance and conductance. The established model is only an eq...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H7/26
Inventor 何建军罗建赵国富徐瑞林于光磊陈晓征黄正炫陈涛钟加勇蔡明张友强
Owner CHONGQING UNIV
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