CN-121983914-A - Calculation method and system for quadrilateral characteristic distance protection measurement impedance

CN121983914ACN 121983914 ACN121983914 ACN 121983914ACN-121983914-A

Abstract

The invention provides a calculation method OF quadrilateral characteristic distance protection measured impedance, which comprises the steps OF calculating a first measured impedance value and a second measured impedance value according to a fixed grounding distance or a fixed interval I section value and combining a fixed load limiting resistance fixed value and a measured impedance angle, drawing a circle by taking an origin O as a starting point and the first measured impedance value as a radius on the basis OF a quadrilateral characteristic diagram OF impedance protection action to draw an intersection point E between the first quadrant and a straight line PD or an extension line thereof, drawing a circle by taking the origin O as the starting point and the second measured impedance value as the radius to draw an intersection point F between the first quadrant and the straight line PD or an extension line thereof, and determining that the action impedance is positioned on a straight line PC if the length OF OE is determined to be smaller than the length OF OF, and determining that the action impedance is positioned on the straight line PD if the length OF OE is determined to be the first measured impedance value otherwise, and determining that the action impedance is positioned on the straight line PD and the final measured impedance value is the second measured impedance value. By implementing the invention, the calculation process and the calculation amount can be reduced.

Inventors

HUANG JIFANG
WANG QILIN
FENG ZONGJIAN
QIN LINSHENG
LIU HUAN
LIU LIZHEN

Assignees

深圳供电局有限公司

Dates

Publication Date: 20260505
Application Date: 20260114

Claims (4)

1. A method for calculating a quadrilateral characteristic distance protection measured impedance, the method comprising the steps of: According to the set grounding distance I section fixed value or the set phase-to-phase distance I section fixed value, and combining the set load limiting resistor fixed value and a known measured impedance angle, calculating a first measured impedance value and a second measured impedance value; Drawing a circle by taking an origin O as a starting point and a first measured impedance value as a radius to draw an intersection point E between the first quadrant and a straight line PC or an extension line of the straight line PC, and drawing a circle by taking the origin O as a starting point and a second measured impedance value as a radius to draw an intersection point F between the first quadrant and the straight line PD or an extension line of the straight line PD; If the length OF the straight line OE is determined to be smaller than the length OF the straight line OF, the action impedance is determined to be located on the straight line PC, and a final measured impedance value is obtained as the first measured impedance value, whereas if the length OF the straight line OE is determined to be greater than the length OF the straight line OF, the action impedance is determined to be located on the straight line PD, and a final measured impedance value is obtained as the second measured impedance value.
2. The method for calculating a quadrilateral characteristic distance protection measured impedance according to claim 1, wherein the measured impedance is calculated by the formula Or (b) Calculate a first measured impedance value Wherein, the method comprises the steps of, Is a known measured impedance angle; setting a value for the set grounding distance I section; Setting a value for the set phase interval I section; By the formula Calculate a second measured impedance value Wherein, the method comprises the steps of, The resistance set value is limited for the set load.
3. A computing system for quadrilateral characteristic distance protection measurement impedance, comprising: The calculation unit is used for calculating a first measured impedance value and a second measured impedance value according to the set grounding distance I section fixed value or the phase-to-phase distance I section fixed value and combining the set load limiting resistance fixed value and a known measured impedance angle; An intersection point drawing unit for drawing a circle based on a quadrilateral characteristic diagram of the existing impedance protection action, using an origin O as a starting point and a first measured impedance value as a radius to draw an intersection point E between the first quadrant and the straight line PC or an extension line of the straight line PC, and using the origin O as a starting point and a second measured impedance value as a radius to draw an intersection point F between the first quadrant and the straight line PD or an extension line of the straight line PD; And the measured impedance acquisition unit is used for determining that the action impedance is positioned on the straight line PC and obtaining a final measured impedance value as the first measured impedance value if the length OF the straight line OE is determined to be smaller than the length OF the straight line OF, and otherwise, determining that the action impedance is positioned on the straight line PD and obtaining the final measured impedance value as the second measured impedance value if the length OF the straight line OE is determined to be greater than the length OF the straight line OF.
4. The computing system for quadrilateral characteristic distance protection measurement impedance of claim 3, wherein the impedance is measured by the formula Or (b) Calculate a first measured impedance value Wherein, the method comprises the steps of, Is a known measured impedance angle; setting a value for the set grounding distance I section; Setting a value for the set phase interval I section; By the formula Calculate a second measured impedance value Wherein, the method comprises the steps of, The resistance set value is limited for the set load.

Description

Calculation method and system for quadrilateral characteristic distance protection measurement impedance Technical Field The invention relates to the technical field of power systems, in particular to a calculation method and a system for quadrilateral characteristic distance protection measurement impedance. Background The distance protection in relay protection is a line backup protection based on the principle of measuring the electrical distance (expressed as impedance) between a fault point and a protection installation position, and the action characteristic is that the closer the fault point is to the protection installation point, the smaller the measured impedance, and the farther the distance is, the larger the measured impedance is. At this time, the core element of the distance protection is an impedance relay, which calculates a measured impedance Zm by receiving the measured voltage U and current I. The impedance relay has a predetermined action characteristic (indicated as a region on the impedance complex plane), and when the measured impedance Zm falls within this action characteristic region, it is determined that the fault is within the protection range and a trip command is issued. The impedance relay includes a circular characteristic impedance relay (e.g., a full impedance circle, a directional impedance circle, an offset impedance circle, etc.) and a quadrangular characteristic impedance relay. The four straight lines (or approximate straight lines) of the quadrilateral characteristic impedance relay can better meet the requirements of avoiding load impedance, tolerating transition resistance, guaranteeing protection range and the like, so that the adaptability is stronger. Currently, the quadrilateral characteristic impedance relay can improve the adaptability to the transition resistance by adjusting the characteristic shape (increasing the R-axis coverage) and adopting an adaptive algorithm or the like. Therefore, the calculation of the quadrilateral characteristic action impedance (i.e., the distance protection measurement impedance Zm) is particularly critical in the power system. As shown in fig. 1, a conventional microcomputer protection is a quadrangular characteristic diagram of an impedance protection operation. In fig. 1, the working principle that when the load limiting resistance is set according to the normal overload impedance, the resistance component RDZ is generally set in a larger range, so that the resistance set value used by the grounding distance section I (or the inter-phase distance section I) is properly reduced on the basis of the set value is adopted, so that the basic principle that the resistance is fault according to 25 Ω at the short-circuit protection outlet or the inter-phase distance is 15 Ω, the length line is not greater than the grounding distance section I set value or the inter-phase distance section I set value by half is adopted, the adaptive condition ：XDZ＝(SinΦd＋tg7°*CosΦd)×|ZZD|;Rd=min{RDZ,max（XD1/2,25/LZ+R1）,8XD1};Rx=min{RDZ/2,max（XX1/2,15/LZ+R1）,8XX1}; for obtaining the resistance set value of the section I is adopted, wherein XDZ, zd, Φd and RDZ respectively represent the distance from point C to the origin O, the distance from point Z to the origin O, the included angle between ZZD and the point D to the origin O in the resistor-reactance rectangular coordinate system in fig. 1, and the length of ZZD is equal to the set section i.e. the impedance set value of the fixed section, the size of Φd is equal to the set protection angle value, and the length of the RDZ is equal to the set protection angle value (i.e. the overload resistance set value). In addition, rd is an actually solved grounding I-section resistance value, rx is an actually solved inter-phase I-section resistance value, XD1 is a set grounding distance I-section fixed value, XX1 is a set inter-phase distance I-section fixed value, LZ is a conversion coefficient of impedance twice (namely the ratio of PT transformation ratio to CT transformation ratio), and R1 is a positive sequence impedance resistance component of the whole circuit. Secondly, based on the self-adaptive condition of the resistance constant value of the distance I section, the method is combined with the known measured impedance angle theta (such as the included angle between the measured impedance Zm1 or Zm2 and the OA in fig. 1) to calculate the action impedance on the straight line PC or the straight line PD in the quadrangular characteristic protection action boundary, and specifically comprises (1) based on the self-adaptive condition of the resistance constant value of the distance I section, solving the P point angle, (2) comparing the calculated P point angle with the measured impedance angle theta, and determining whether the action impedance is on the straight line PC or the straight line PD according to the comparison result, (3) calculating the action impedance on the straight line PC or the strai