CN110764019A - Line temporary grounding quantity judgment and high-precision positioning method based on double-end measurement - Google Patents
Line temporary grounding quantity judgment and high-precision positioning method based on double-end measurement Download PDFInfo
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Abstract
The invention provides a line temporary grounding number judgment and high-precision positioning method based on double-end measurement, which comprises the following steps of: s1, suspending the tail end of a power transmission line without grounding, measuring the insulation resistance of the line to the ground at the head end of the power transmission line by using an insulation resistance measuring instrument, and when the insulation resistance of the line is more than 100 megaohms, the line has no grounding point; when the insulation resistance of the line is 0-100 ohms, a temporary grounding point exists in the middle of the line; s2, when a temporary grounding point exists on the line, determining the upper limit of the distance from the grounding point on the line to the head end and the tail end respectively by adopting a head-end and tail-end positioning method, if the upper limit of the distance from the grounding point to the head end and the tail end is crossed, judging that only one grounding point exists on the line, and then accurately positioning the position of the grounding point by adopting a double-end high-precision positioning method; otherwise, judging that more than or equal to two grounding points exist on the line, and preliminarily defining the range of the grounding points by adopting a double-end positioning method; the invention has the characteristics of power frequency interference resistance, high positioning precision, simple and feasible measurement method and the like.
Description
Technical Field
The invention relates to the field of overhead line test detection, in particular to a line temporary grounding number judgment and high-precision positioning method based on double-end measurement.
Background
In order to prevent the occurrence of personal casualty accidents caused by induced electricity, the construction personnel can hang and establish temporary grounding wires at two ends of an operation range during power failure maintenance and construction operation of the overhead transmission line. Before line parameter measurement and line operation, the whole temporary grounding line needs to be dismantled. Because the length of the overhead transmission line reaches hundreds of kilometers, the temporary grounding wire is not detached in time. If the position of the grounding point cannot be accurately positioned, a large amount of manpower and time are consumed by only depending on manual checking.
Publication number CN107688136A discloses a method for judging and positioning an ultra-high voltage long-distance transmission line grounding point, which can determine whether the line is normally connected, determine that a grounding phase exists, and initially position the grounding position of the grounding phase. However, the invention proposes to determine the position of the grounding point by subtracting the grounding resistance of the grounding point from the direct current resistance of the grounding phase. Because the position of the grounding point is uncertain, when the grounding resistance of the grounding point adopts the designed ground grid resistance value provided by the invention, a larger error exists, and the situation of positioning error exists.
Disclosure of Invention
The invention provides a line temporary grounding number judgment and high-precision positioning method based on double-end measurement. The invention avoids the line power frequency parameter and mutual inductance coupling and other influencing factors, and eliminates the positioning error caused by the power end grounding resistance, the grounding point grounding resistance and the line direct resistance. The method has the characteristics of power frequency interference resistance, high positioning precision, simplicity, convenience, feasibility and the like, and is suitable for positioning temporary grounding points of alternating current and direct current overhead transmission lines with different lengths.
The technical scheme of the invention is as follows:
a line temporary grounding number judgment and high-precision positioning method based on double-end measurement comprises the following specific steps:
s1, suspending the tail end of a power transmission line without grounding, measuring the insulation resistance of the line to the ground at the head end of the power transmission line by using an insulation resistance measuring instrument, and when the insulation resistance of the line is more than 100 megaohms, the line has no grounding point; when the insulation resistance of the line is 0-100 ohms, a temporary grounding point exists in the middle of the line;
s2, when a temporary grounding point exists on the line, determining the upper limit of the distance from the grounding point on the line to the head end and the tail end respectively by adopting a head-end and tail-end positioning method, if the upper limit of the distance from the grounding point to the head end and the tail end is crossed, judging that only one grounding point exists on the line, and then accurately positioning the position of the grounding point by adopting a double-end high-precision positioning method; otherwise, judging that more than or equal to two grounding points exist on the line, and preliminarily defining the range of the grounding points by adopting a double-end positioning method;
the specific operation steps of step S2 are as follows:
s21, grounding the tail end of the line,measuring the loop direct resistance r of the line to the ground at the head end by adopting a loop direct resistance measuring instruments1Direct resistance of the measured loop
In the formula: r iss1The loop direct resistance is measured for the tail end short circuit and the head end; r ishgThe grounding resistance is the grounding resistance of the head end grounding grid; r isxThe direct current resistance of the first section of line; r isyThe direct current resistance of the tail section line; r isegA tail end grounding grid grounding resistor; r istwrThe grounding point grounding resistor comprises a tower material resistor of a tower at the grounding point and a grounding resistor of a grounding device;
s22, according to a formula
In the formula:
for the converted loop direct resistance value, β is the resistance temperature rise coefficient, t is the measured temperature value of the measuring circuit, the direct resistance of the loop at the head end is converted to the direct resistance under 20 DEG C
S23, according to the loop direct resistance rs1Formula determining the distance of the grounding point from the head end asl is the measured line length and r is obtainedx＜rs1Accordingly, the actual distance x between the grounding point and the head end is judged to be less than xs1I.e. the upper limit of the distance of the ground point from the head end is xs1；
S24, grounding the head end of the line, and measuring the direct resistance r of the line to the ground loop at the tail end by adopting a loop direct resistance measuring instruments2Direct resistance of the measured loop
In the formula: r iss2The loop direct resistance is measured for head end short circuit and tail end; in the same step S22, the direct resistance of the end loop is convertedDirect resistance to 20 DEG C
In the same step S23, it is determined that the upper limit of the distance from the ground point to the end is
S25, when
And, in the formula: r islJudging whether the line has one or only one grounding point for the full-length straight resistance value of the line; otherwise, judging that no less than two grounding points exist on the line;
s26, if the line has not less than two grounding points, according to the steps S22-S23, the upper limit x of the distance between the grounding point and the head end and the distance between the grounding point and the tail end can be determineds1And xs2Removing part of the grounding point; repeating the steps S21-S24;
and S27, if the circuit has one grounding point, accurately positioning the position of the grounding point by adopting a double-end high-precision positioning method.
The double-end high-precision positioning method in the step S27 comprises the following specific steps:
s271, disconnecting the tail end of the line from the ground, and measuring the direct resistance r of the line to the ground at the head end by adopting a direct resistance measuring instrument of the loopo1The measured loop direct resistance ro1＝rhg+rx+rtwrIn the formula: r iso1For the direct resistance of the loop measured at the end open circuit and the head end, the step S22 is synchronized to convert the direct resistance of the loop measured at the end open circuit and the head end to the direct resistance at 20 DEG C
S272, disconnecting the head end of the line from the ground, and measuring the direct resistance r of the line to the ground at the tail end by adopting a direct resistance measuring instrument of the loopo2The measured loop direct resistance ro2＝reg+ry+rtwrIn the formula: r iso2For open-end, end-measured loop direct resistance, step S22, startThe direct resistance value of the loop measured by the end open circuit and the tail end is converted into the direct resistance at the temperature of 20 DEG C
S273. simultaneous loop direct resistance positioning formula
Solving to obtain grounding point grounding resistanceDirect current resistance of line between head end and grounding point
Direct current resistance of line between terminal and grounding point
Direct resistance of full length of line
S274. adopting a formulaSolving for the precise distance x of the ground point from the head end, wherein:
in the step S22, the temperature rise coefficient of resistance β of the aluminum material is 0.0036 ℃-1The temperature rise coefficient of resistance β of the carbon fiber composite core lead is 0.0043 DEG C-1。
Compared with the prior art, the invention has the beneficial effects that:
(1) compared with the prior art, the method can judge whether the number of the grounding points on the line is one or not by adopting a double-end positioning method.
(2) Compared with the prior art, the method solves the problem that the grounding resistance of the grounding point is unknown and the positioning is inaccurate. The invention measures the direct resistance of three different loop structures at two ends of the circuit, and directly solves the grounding resistance of the grounding point by combining three direct resistance positioning equations. When the direct current resistance of a line between the head end and the grounding point is solved, the grounding resistance of the grounding point is reduced, the grounding resistance of a grounding network of a grounding end of a power supply is considered, the position of the grounding point can be accurately positioned, the problem of inaccurate positioning caused by unknown grounding resistance of the grounding point is solved, and errors caused by the grounding resistance of the grounding network are eliminated. When the grounding resistance at the grounding point is large, the positioning range of the existing method may exceed the full length of the line, and the problem of positioning error occurs.
(3) Compared with the prior art, the invention has higher positioning precision. The invention solves the loop direct resistance of the whole length of the line by a simultaneous three-loop direct resistance positioning equation to convert the position of the grounding point. When the grounding point exists on the line, the direct resistance of the whole length of the line cannot be directly measured, the conventional method generally adopts a theoretical design value for replacement, and the value has different degrees from an actual value, so that the error magnitude is difficult to determine. The method provided by the invention eliminates the positioning error caused by the direct resistance design value of the line, and the positioning error is less than 5% for the ultra-long extra-high voltage direct current line (thousands of kilometers) and less than 2% for the short distance alternating current and direct current lines (hundreds of kilometers).
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Fig. 2 is a diagram of a direct resistance measurement loop when the end of the line is grounded.
Fig. 3 is a circuit diagram of the present invention for measuring the direct resistance at the head end when the tail end of the line is grounded.
Fig. 4 is a circuit diagram of the end measurement of the direct resistance when the head end of the line is grounded according to the present invention.
Fig. 5 is a diagram for determining the number of line-grounding points according to the present invention.
Fig. 6 is a circuit diagram of the head end measurement of the direct resistance when the tail end of the line is open.
Fig. 7 is a circuit diagram of the invention for measuring the direct resistance at the end of the line when the head end is open.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In this embodiment, a certain dc ground electrode is taken as an example, the model number of the ground electrode line lead is 2 × 2 × JNRLH60/G1A-630/45, the length L is 134.7km, the design value of the overall length direct resistance of the ground electrode line is 3.56 Ω, the head end of the ground electrode line is a converter station, the tail end of the ground electrode line is a ground electrode, the design value of the converter station grounding grid resistor rhg is 0.023 Ω, and the design value of the ground electrode resistor reg is 0.2 Ω.
Before beginning to detect, the earthing pole circuit all does not put into operation, and the earthing pole circuit is located test condition: the earthing knife-switch at the first and the last ends of the earthing electrode circuit is positioned at the closing position, and the first and the last ends of the circuit are both earthed.
And (3) connecting the head end of the polar line 1 of the grounding electrode into an insulation resistance measuring instrument, sequentially opening a grounding knife switch at the tail end and the head end, and measuring the insulation resistance of the polar line 1 to the ground, wherein the insulation resistance of the polar line 1 is zero ohm. According to the flow chart 1 it is determined that a grounding point is present on the pole line 1. Due to the grounding point on the polar line, the direct current resistance of the polar line in the whole length cannot be obtained by measurement for the moment, and the known parameter cannot be positioned as the grounding point.
1) First, according to step S21, the dc resistance of the pole line 1 to ground is measured in the first section of the line. According to the figures 2 and 3, the direct resistance measuring instrument is connected in series to the head end of the polar line 1, the high-voltage output end is connected with the polar line, the grounding end is connected with the grounding network of the converter station, and the tail end of the polar line 1 is connected with the polar address grounding electrode. Measuring to obtain the direct resistance r of the polar line 1s1The value is formed by series-parallel connection of resistances such as direct resistance of a converter station grounding grid, direct resistance of the first section of a line, direct resistance of a grounding point grounding device, direct resistance of a tail end line, direct resistance of a grounding electrode and the like, and the positioning formula is
According to step S22Line temperature conversion
2) The above steps are repeated according to step S24, and the straight resistance r of the polar line 1 is measured at the end of the lines2The temperature conversion is performed according to step S22
3) According to step S25, calculation is made based on the measurement results
And (3) the resistance value is larger than the full-line direct resistance value of the line by 3.56 omega, and the line is judged to have one grounding point according to the flow charts 1 and 5.
4) According to step S271, according to FIG. 6, the tail end of the line is disconnected from the ground, the direct resistance measuring instrument is connected in series to the head end of the polar line 1, and the direct resistance r of the circuit to the ground is measuredo1. According to step S22, the loop direct resistance value is converted to the direct resistance at 20 DEG C
5) According to step S272, according to FIG. 7, the head end of the line is disconnected from the ground, and the above steps are repeated to measure the direct resistance r of the circuit to the groundo2. According to step S22, the loop direct resistance value is converted to the direct resistance at 20 DEG C
6) Vertical loop direct resistance positioning formula
The loop direct resistance positioning equation can be obtained as follows:
direct resistance r of grounding grid of converter stationhg0.023 omega, direct resistance of grounding electrode regSubstituting the equation set into 0.2 omega, and solving to obtain the final product
And r isl＝rx+ry＝3.252Ω。
According to step S274, the accurate distance x of the ground point from the head end is 92.25km, the actual distance is 90km, and the relative error is 1.67%.
The invention solves the loop direct resistance of the whole length of the line by a simultaneous three-loop direct resistance positioning equation to convert the position of the grounding point. When the grounding point exists on the line, the direct resistance of the whole length of the line cannot be directly measured, the conventional method generally adopts a theoretical design value for replacement, and the value has different degrees from an actual value, so that the error magnitude is difficult to determine. The method provided by the invention eliminates the positioning error caused by the direct resistance design value of the line, and the positioning error is less than 5% for the ultra-long extra-high voltage direct current line (thousands of kilometers) and less than 2% for the short distance alternating current and direct current lines (hundreds of kilometers).
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (3)
1. A line temporary grounding quantity judging and high-precision positioning method based on double-end measurement is characterized by comprising the following specific steps:
s1, suspending the tail end of a power transmission line without grounding, measuring the insulation resistance of the line to the ground at the head end of the power transmission line by using an insulation resistance measuring instrument, and when the insulation resistance of the line is more than 100 megaohms, the line has no grounding point; when the insulation resistance of the line is 0-100 ohms, a temporary grounding point exists in the middle of the line;
s2, when a temporary grounding point exists on the line, determining the upper limit of the distance from the grounding point on the line to the head end and the tail end respectively by adopting a head-end and tail-end positioning method, if the upper limit of the distance from the grounding point to the head end and the tail end is crossed, judging that only one grounding point exists on the line, and then accurately positioning the position of the grounding point by adopting a double-end high-precision positioning method; otherwise, judging that more than or equal to two grounding points exist on the line, and preliminarily defining the range of the grounding points by adopting a double-end positioning method;
the specific operation steps of step S2 are as follows:
s21, grounding the tail end of the line, and measuring the direct resistance r of the line to the ground at the head end by adopting a direct resistance measuring instrument of the circuits1Direct resistance of the measured loop
In the formula: r iss1The loop direct resistance is measured for the tail end short circuit and the head end; r ishgThe grounding resistance is the grounding resistance of the head end grounding grid; r isxThe direct current resistance of the first section of line; r isyThe direct current resistance of the tail section line; r isegA tail end grounding grid grounding resistor; r istwrThe grounding point grounding resistor comprises a tower material resistor of a tower at the grounding point and a grounding resistor of a grounding device;
s22, according to a formula
In the formula:
for the converted loop direct resistance value, β is the resistance temperature rise coefficient, t is the measured temperature value of the measuring circuit, the direct resistance of the loop at the head end is converted to the direct resistance under 20 DEG C
S23, according to the loop direct resistance rs1Formula determining the distance of the grounding point from the head end as
l is the measured line length and r is obtainedx＜rs1Accordingly, the actual distance x between the grounding point and the head end is judged to be less than xs1I.e. the upper limit of the distance of the ground point from the head end is xs1；
S24, grounding the head end of the line and adoptingA line direct resistance measuring instrument for measuring the direct resistance r of a line to ground loop at the tail ends2Direct resistance of the measured loop
In the formula: r iss2The loop direct resistance is measured for head end short circuit and tail end; in the same step S22, the direct resistance of the end loop is converted to the direct resistance at 20 DEG C
In the same step S23, it is determined that the upper limit of the distance from the ground point to the end is
S25, when
And, in the formula: r islJudging whether the line has one or only one grounding point for the full-length straight resistance value of the line; otherwise, judging that no less than two grounding points exist on the line;
s26, if the line has not less than two grounding points, according to the steps S22-S23, the upper limit x of the distance between the grounding point and the head end and the distance between the grounding point and the tail end can be determineds1And xs2Removing part of the grounding point; repeating the steps S21-S24;
and S27, if the circuit has one grounding point, accurately positioning the position of the grounding point by adopting a double-end high-precision positioning method.
2. The method for determining the temporary grounding quantity and positioning the line with high precision based on the double-ended measurement as claimed in claim 1, wherein the double-ended high-precision positioning method in the step S27 comprises the following specific steps:
s271, disconnecting the tail end of the line from the ground, and measuring the direct resistance r of the line to the ground at the head end by adopting a direct resistance measuring instrument of the loopo1The measured loop direct resistance ro1＝rhg+rx+rtwrIn the formula: r iso1Loop for tail end open circuit, head end measurementDirect resistance, synchronous step S22, converting the direct resistance value of the loop measured at the end open circuit and the head end to the direct resistance value at 20 DEG C
S272, disconnecting the head end of the line from the ground, and measuring the direct resistance r of the line to the ground at the tail end by adopting a direct resistance measuring instrument of the loopo2The measured loop direct resistance ro2＝reg+ry+rtwrIn the formula: r iso2For the open-end and end-end measured loop direct resistance, step S22 is synchronized to convert the open-end and end-measured loop direct resistance values to direct resistance at 20 deg.C
S273. simultaneous loop direct resistance positioning formula
Solving to obtain grounding point grounding resistance
Direct current resistance of line between head end and grounding pointDirect current resistance of line between terminal and grounding point
Direct resistance of full length of line
S274. adopting a formula
Solving for the precise distance x of the ground point from the head end, wherein:
3. the method for determining the temporary grounding quantity of the line and positioning the line with high precision based on the double-end measurement as claimed in claim 1, wherein the temperature rise resistance coefficient β of the aluminum material in the step S22 is 0.0036 DEG C-1The temperature rise coefficient of resistance β of the carbon fiber composite core lead is 0.0043 DEG C-1。
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