CN107796979B - Zero sequence current waveform acquisition device for overhead distribution line with near line interference resistance - Google Patents
Zero sequence current waveform acquisition device for overhead distribution line with near line interference resistance Download PDFInfo
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- CN107796979B CN107796979B CN201710925052.3A CN201710925052A CN107796979B CN 107796979 B CN107796979 B CN 107796979B CN 201710925052 A CN201710925052 A CN 201710925052A CN 107796979 B CN107796979 B CN 107796979B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
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Abstract
The invention discloses an overhead distribution line zero-sequence current waveform acquisition device capable of resisting adjacent line interference, which solves the problem that the existing overhead distribution line zero-sequence current waveform acquisition device is easily interfered by adjacent line electromagnetic interference. A signal processor support (7) is arranged on a cross arm (2) of the overhead distribution line tower (1), a signal processor (5) is arranged on the signal processor support (7), and the signal processor (5) is connected with a signal collector (4) on an overhead conductor (3) through a coaxial cable (6); the signal processor (5) inputs voltage signals which are collected by the three signal collectors (4) and represent the three-phase current waveform of the overhead distribution line into respective signal conditioning circuits, and the voltage signals are input into an addition circuit after signal conditioning for addition operation, namely, signals representing the zero-sequence current waveform are output, namely: i0= iA + iB + iC. And a more accurate zero sequence current waveform is acquired, and the accurate judgment of the single-phase grounding of the transmission conductor is realized.
Description
Technical Field
The invention relates to a current waveform acquisition device, in particular to an overhead distribution line zero-sequence current waveform acquisition device capable of shielding electromagnetic interference of adjacent lines.
Background
The overhead distribution line is easy to generate single-phase grounding, and normally, the line is allowed to continue to operate for a period of time after the single-phase grounding is generated, but the single-phase grounding can cause the non-fault phase voltage to be increased, and the interphase short-circuit fault is easy to occur. Therefore, the method has important significance for preventing interphase short circuit fault in the single-phase grounding detection of the overhead distribution line. The detection of zero sequence current is an effective method for single-phase grounding detection, and the existing main method for collecting the zero sequence current of the overhead distribution line is to respectively install induction coils on A, B, C phase lines and obtain the zero sequence current by superposing signals representing current phasors of three-phase lines through an electromagnetic induction principle. However, the zero sequence current detection device based on the induction coil is easily interfered by an electromagnetic field of an adjacent power line, and the phenomenon of inaccurate zero sequence current measurement often occurs, so that the overhead distribution line which is not grounded is judged as a ground fault by mistake.
Disclosure of Invention
The invention provides an overhead distribution line zero-sequence current waveform acquisition device capable of resisting adjacent line interference, and solves the technical problem that the existing overhead distribution line zero-sequence current waveform acquisition device is easily interfered by adjacent line electromagnetic interference.
The invention solves the technical problems by the following technical scheme:
the general concept of the invention is that the metal conductor of the fixed resistor is directly connected into the overhead power distribution line, and the line current is measured by a method of measuring the voltage drop generated by the line current flowing through the conductor of the fixed resistor and calculating the measured current, so that the interference of a space electromagnetic field generated by an adjacent line on a measurement signal can be effectively avoided.
A zero-sequence current waveform acquisition device of an overhead distribution line capable of resisting adjacent line interference comprises an overhead distribution line tower 1, wherein a signal processor support 7 is arranged on a cross arm 2 of the overhead distribution line tower 1, a signal processor 5 is arranged on the signal processor support 7, and the signal processor 5 is connected with a signal collector 4 on an overhead conductor 3 through a first coaxial cable 6; the signal processor 5 inputs the voltage signals representing the three-phase current waveform of the overhead distribution line collected by the three signal collectors 4 into respective signal conditioning circuits, and the voltage signals are input into the addition circuit for addition operation after signal conditioning, namely, the signals representing the zero-sequence current waveform are output, namely: i0= iA + iB + iC.
The signal collector 4 is a double-layer barrel-shaped structure, the barrel-shaped outer shell layer is a current external leading-out confluence shell 13, the barrel-shaped inner shell layer is in an umbrella-shaped curved surface shape, the barrel-shaped inner shell layer is a current internal leading-out confluence shell 8B, a second coaxial cable 8A is arranged on the umbrella top of the inner cavity of the barrel-shaped inner shell layer, the other end of the second coaxial cable 8A is connected with a current lead-in confluence cable 12, the other end of the current lead-in confluence cable 12 is connected with an overhead conductor access end 17, an overhead conductor outlet end 18 is connected on the bottom end surface of the outer side of the barrel-shaped shell layer, a measurement voltage signal high potential outlet end 9 is arranged on the second coaxial cable 8A, a measuring voltage signal low potential leading-out terminal 10 is arranged on the inner cavity of the barrel-shaped inner shell layer, and a measuring voltage signal high potential leading-out terminal 9 and a measuring voltage signal low potential leading-out terminal 10 are electrically connected with the signal processor 5 through a first coaxial cable 6.
A fan bracket 14 is provided between the current introducing bus cable 12 and the barrel-shaped inner shell, and a fan 15 is provided on the fan bracket 14.
in the signal transmission process of current acquisition and characterization current, the interference of an electromagnetic field of an adjacent line on a measurement result is avoided, a more accurate zero-sequence current waveform is acquired, and the accurate judgment of single-phase grounding of a transmission conductor is realized.
Drawings
FIG. 1 is a schematic diagram of the general structure of the present invention;
Fig. 2 is a schematic structural diagram of the signal collector 4 of the present invention;
3 FIG. 3 3 3 is 3 a 3 sectional 3 view 3 taken 3 along 3 line 3 A 3- 3 A 3 in 3 FIG. 3 2 3; 3
Fig. 4 is a schematic circuit diagram of the signal processor 5 of the present invention.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings:
A zero-sequence current waveform acquisition device of an overhead distribution line capable of resisting adjacent line interference comprises an overhead distribution line tower 1, wherein a signal processor support 7 is arranged on a cross arm 2 of the overhead distribution line tower 1, a signal processor 5 is arranged on the signal processor support 7, and the signal processor 5 is connected with a signal collector 4 on an overhead conductor 3 through a coaxial cable 6; the signal processor 5 inputs the voltage signals representing the three-phase current waveform of the overhead distribution line collected by the three signal collectors 4 into respective signal conditioning circuits, and the voltage signals are input into the addition circuit for addition operation after signal conditioning, namely, the signals representing the zero-sequence current waveform are output, namely: i0= iA + iB + iC.
the signal collector 4 is a double-layer barrel-shaped structure, the barrel-shaped outer shell layer is a current external leading-out confluence shell 13, the barrel-shaped inner shell layer is in an umbrella-shaped curved surface shape, the barrel-shaped inner shell layer is a current internal leading-out confluence shell 8B, a second coaxial cable 8A is arranged on the umbrella top of the inner cavity of the barrel-shaped inner shell layer, the other end of the second coaxial cable 8A is connected with a current lead-in confluence cable 12, the other end of the current lead-in confluence cable 12 is connected with an overhead conductor access end 17, an overhead conductor outlet end 18 is connected on the bottom end surface of the outer side of the barrel-shaped shell layer, a measurement voltage signal high potential outlet end 9 is arranged on the second coaxial cable 8A, a measuring voltage signal low potential leading-out terminal 10 is arranged on the inner cavity of the barrel-shaped inner shell layer, and a measuring voltage signal high potential leading-out terminal 9 and a measuring voltage signal low potential leading-out terminal 10 are electrically connected with the signal processor 5 through a coaxial cable 11 for transmitting measuring voltage signals.
a fan bracket 14 is provided between the current introducing bus cable 12 and the barrel-shaped inner shell, and a fan 15 is provided on the fan bracket 14.
The signal collector 4 of the invention is connected in series in the line, the line current passes through the conductor of the fixed resistance, when the grounding occurs, the current of the grounding phase is transient current with a sudden change effect, and the conductor has an inductance effect, which can influence the accuracy of the transient current measurement; in addition, when harmonics are present in the line current, the conductor inductance also has an effect on the measurement of the harmonic current. According to the invention, the conductor of the signal collector 4 is designed to be in a quadratic coaxial mode, so that the conductor inductance is effectively reduced, and the measurement precision of transient current and harmonic current is improved. Line current passes through the conductor of the fixed resistor, and a heat effect is generated, so that the temperature of the conductor is increased, the resistivity of the conductor is changed, and the current measurement precision is influenced. The invention designs a cavity structure for the fixed conductor of the signal collector 4, installs the fan, and maintains the conductor in a relatively constant temperature range by an air cooling mode of forced air circulation, thereby avoiding the influence of temperature rise effect on the measurement precision of the line current. The method for measuring the current by directly connecting the metal conductor into the overhead distribution line is adopted, although the interference of an adjacent line on a measurement result is avoided relative to a coil measurement mode in the measurement method, the situation that the electromagnetic field of the adjacent line can induce potential on the metal conductor still exists, and the measurement precision is influenced. The method for designing the outer layer metal of the fixed conductor resists the possible induced potential of an electromagnetic field generated by a nearby line to the fixed resistance part, and ensures the measurement accuracy of the line current. The signal collector converts the current signal of the overhead distribution line into a voltage signal, when the load of the overhead distribution line is small, the current value is small, the voltage signal output by the signal collector is small, and therefore the possibility of distortion caused by the interference of an electromagnetic field of an adjacent line exists in the process of transmitting the output voltage signal to the signal processor. The invention adopts the coaxial cable as the transmission cable for measuring the voltage signal, thereby effectively avoiding the interference of the electromagnetic field of the adjacent line to the voltage signal in the transmission process.
The signal collector 4 has a function of sensing a current signal to be detected, and the sensing part of the signal collector structurally comprises a second coaxial cable 8A and a current internal leading-out convergence shell 8B, wherein the current internal leading-out convergence shell 8B is a quadric surface, and the two parts are connected into a whole. The second coaxial cable 8A is of a columnar structure, and a current introducing junction cable 12 and an overhead conductor access end 17 sequentially extend outwards and are of a coaxial structure; the current inner leading-out convergence shell 8B is of an umbrella-shaped curved surface structure, and sequentially extends outwards to form a current outer leading-out convergence shell 13 and an overhead conductor leading-out end 18. The edges of the second coaxial cable 8A and the current lead-out bus case 8B are respectively provided with a measurement voltage signal high potential lead-out terminal 9 and a measurement voltage signal low potential lead-out terminal 10, both of which are in an annular structure that is axisymmetrical with respect to the coaxial cable 8A. A fan bracket 14 and a fan 15 are arranged between the current leading-in bus cable 12 and the current leading-out bus shell 13, a fan energy-taking coil 16 is annularly arranged beside the fan 15 along the current leading-in bus part 12 and is electrically connected with the fan 15 to supply power for the fan 15 during working, the high-potential leading-out end 9 of a measurement voltage signal and the low-potential leading-out end 10 of the measurement voltage signal are electrically connected with a coaxial cable 11 for transmitting the measurement voltage signal, and a first coaxial cable 6 for transmitting the measurement voltage signal is led out from a gap of the fan bracket 14 to the outside of the signal collector and is electrically connected with the signal processor 5.
The signal processor 5 has a metal housing 23 and has an a-phase measurement voltage signal input 19, a B-phase measurement voltage signal input 20 and a C-phase measurement voltage signal input 21, as well as a signal output 22 which characterizes the zero sequence current. The first coaxial cable 6 for transmitting the measurement voltage signal is electrically connected with three input ends of the measurement voltage signal of the signal processor 5, the input ends of the measurement voltage signals of the A phase, the B phase and the C phase are electrically connected with the input ends of respective signal conditioning circuits, the output ends of the respective signal conditioning circuits are electrically connected with the input end of an addition circuit, and the output end of the addition circuit is the signal output end 22 for representing the zero sequence current.
A certain phase of the overhead conductor 3 is electrically connected with an overhead conductor access end 17 of the signal collector, so that the current of the matched electric line is led into a sensing part of the signal collector through a current leading-in confluence cable 12, and then is led out of the sensing part of the signal collector through a current leading-out confluence shell 13, and the detected current is reintroduced into the overhead conductor 3 through an overhead conductor access end 18. The measured current forms a voltage drop at the sensing part of the signal collector 4, a voltage drop signal is input into the coaxial cable 11 for transmitting the measurement voltage signal through the measurement voltage signal high potential leading-out terminal 9 and the measurement voltage signal low potential leading-out terminal 10, and the coaxial cable 11 for transmitting the measurement voltage signal transmits the potential difference signal to the phase measurement voltage signal input end of the signal processor 5. When the signal collector 4 works, the fan 15 energy-taking coil 16 takes energy through the current of the overhead distribution line to supply power to the fan 15, the fan 15 rotates to keep the temperature of the sensing part of the signal collector relatively constant in an air cooling mode, and when the distribution line is not loaded, the fan 15 stops working because the energy-taking coil 16 cannot supply power to the fan 15. Voltage signals which are collected by the three signal collectors 4 and represent three-phase current waveforms of the overhead distribution line are input into respective signal conditioning circuits, and are input into an addition circuit after signal conditioning for addition operation, namely, signals which represent zero-sequence current waveforms are output, namely: i0= iA + iB + iC.
Claims (2)
1. The zero-sequence current waveform acquisition device of the overhead distribution line capable of resisting adjacent line interference comprises an overhead distribution line tower (1), and is characterized in that a signal processor support (7) is arranged on a cross arm (2) of the overhead distribution line tower (1), a signal processor (5) is arranged on the signal processor support (7), and the signal processor (5) is connected with a signal collector (4) on an overhead conductor (3) through a first coaxial cable (6); the signal processor (5) inputs voltage signals which are collected by the three signal collectors (4) and represent the three-phase current waveform of the overhead distribution line into respective signal conditioning circuits, and the voltage signals are input into an addition circuit after signal conditioning for addition operation, namely, signals representing the zero-sequence current waveform are output, namely: i0= iA + iB + iC; the signal collector (4) is of a double-layer barrel-shaped structure, a barrel-shaped outer shell layer is of a current outer leading-out convergence shell (13), a barrel-shaped inner shell layer is of an umbrella-shaped curved surface shape, a barrel-shaped inner shell layer is of a current inner leading-out convergence shell (8B), a second coaxial cable (8A) is arranged on the umbrella top of an inner cavity of the barrel-shaped inner shell layer, the other end of the second coaxial cable (8A) is connected with a current leading-in convergence cable (12), the other end of the current leading-in convergence cable (12) is connected with an overhead conductor incoming end (17), an overhead conductor outgoing end (18) is connected to the bottom end face of the outer side of the barrel-shaped outer shell layer, a voltage signal high-potential outgoing end (9) for measurement is arranged on the second coaxial cable (8A), a voltage signal low-potential outgoing end (10) for measurement is arranged on the inner cavity of the barrel-shaped inner shell layer, and the voltage signal high-potential outgoing end (9) and the The devices (5) are electrically connected together.
2. The zero sequence current waveform acquisition device of the overhead distribution line resisting the adjacent line interference according to claim 1, characterized in that a fan bracket (14) is arranged between the current introducing bus cable (12) and the barrel-shaped inner shell layer, and a fan (15) is arranged on the fan bracket (14).
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| CN201710925052.3A CN107796979B (en) | 2017-10-02 | 2017-10-02 | Zero sequence current waveform acquisition device for overhead distribution line with near line interference resistance |
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| CN201710925052.3A CN107796979B (en) | 2017-10-02 | 2017-10-02 | Zero sequence current waveform acquisition device for overhead distribution line with near line interference resistance |
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| CN107796979B true CN107796979B (en) | 2019-12-13 |
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2017
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Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
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| SU1721524A1 (en) * | 1988-11-28 | 1992-03-23 | Душанбинское Проектно-Конструкторское Технологическое Бюро "Спецавтоматика" | Zero sequence current-to-voltage converter |
| JPH1164391A (en) * | 1997-08-19 | 1999-03-05 | Tempearl Ind Co Ltd | Noncontact ac microcurrent detection circuit |
| CN102135587A (en) * | 2011-01-31 | 2011-07-27 | 吕强 | Fault monitoring method and system of power line |
| CN102253271A (en) * | 2011-06-30 | 2011-11-23 | 华北电力大学 | Real-time measurement device and method for current of electrified overhead line |
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| CN103675569A (en) * | 2012-09-06 | 2014-03-26 | 国家电网公司 | Earth fault detection device and system for overhead line |
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| CN107796979A (en) | 2018-03-13 |
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