CN107796979B - Zero sequence current waveform acquisition device for overhead distribution line with near line interference resistance - Google Patents

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

Zero-sequence current waveform acquisition device for overhead distribution lines against interference from adjacent lines

technical field

The invention relates to a current waveform acquisition device, in particular to a zero-sequence current waveform acquisition device for overhead power distribution lines capable of shielding electromagnetic interference from adjacent lines.

Background technique

Overhead distribution lines are prone to single-phase grounding. Usually, the line is allowed to continue running for a period of time after single-phase grounding occurs, but single-phase grounding will cause the non-faulty phase voltage to rise, and phase-to-phase short-circuit faults are prone to occur. Therefore, the detection of single-phase grounding of overhead distribution lines is of great significance for preventing phase-to-phase short-circuit faults. The detection of zero-sequence current is an effective method for single-phase grounding detection. The existing main method for collecting the zero-sequence current of overhead distribution lines is to install induction coils on the A, B, and C phase lines respectively, and through electromagnetic induction The principle is to superimpose the signals representing the current phasor of the three-phase line to obtain the zero-sequence current. However, the above-mentioned zero-sequence current detection device based on the induction coil is susceptible to the interference of the electromagnetic field of the adjacent power line, and the phenomenon of zero-sequence current measurement is often inaccurate, and then the ungrounded overhead distribution line is misjudged as a ground fault.

Contents of the invention

The invention provides an overhead distribution line zero-sequence current waveform acquisition device that is resistant to interference from adjacent lines, and solves the technical problem that the existing overhead distribution line zero-sequence current waveform acquisition device is easily subjected to electromagnetic interference from adjacent lines.

The present invention solves the above technical problems through the following technical solutions:

The general idea of the present invention is to directly connect the metal conductor with fixed resistance to the power distribution overhead line, and measure the line current by measuring the voltage drop generated by the line current flowing through the conductor with fixed resistance to calculate the measured current, which can effectively avoid the The interference of the space electromagnetic field generated by the line on the measurement signal.

An overhead power distribution line zero-sequence current waveform acquisition device capable of resisting interference from adjacent lines, comprising an overhead power distribution line tower 1, a signal processor bracket 7 is arranged on the crossarm 2 of the overhead power distribution line tower 1, and the signal processor The support 7 is provided with a signal processor 5, and the signal processor 5 is connected together with the signal collector 4 on the overhead wire 3 through the first coaxial cable 6; The voltage signal of the three-phase current waveform of the overhead distribution line is input to the respective signal conditioning circuit, and after signal conditioning, it is input to the addition circuit for addition operation, that is, the signal representing the zero-sequence current waveform is output, namely: i0=iA+ iB+ iC.

The signal collector 4 is a double-layer barrel structure, the barrel-shaped outer shell is the confluence shell 13 that leads out of the current, the shape of the barrel-shaped inner shell is an umbrella-shaped curved surface, and the barrel-shaped inner shell is the current inner-lead confluence shell 8B. A second coaxial cable 8A is arranged on the umbrella top of the inner cavity of the barrel-shaped inner shell. The terminals 17 are connected together, and the outer bottom end surface of the barrel-shaped outer shell is connected with an overhead wire connecting end 18, and the second coaxial cable 8A is provided with a high-potential lead-out end 9 for the measurement voltage signal, and on the barrel-shaped inner shell The inner cavity is provided with a low-potential lead-out terminal 10 for the measurement voltage signal, and the high-potential lead-out terminal 9 and the low-potential lead-out terminal 10 for the measurement voltage signal are electrically connected to the signal processor 5 through the first coaxial cable 6 .

A fan bracket 14 is arranged between the current lead-in bus cable 12 and the barrel-shaped inner shell, and a fan 15 is arranged on the fan bracket 14 .

During the process of current acquisition and signal transmission representing the current, the invention avoids the interference of the electromagnetic field of the adjacent line on the measurement results, acquires more accurate zero-sequence current waveforms, and realizes the accurate judgment of the single-phase grounding of the transmission wire.

Description of drawings

Fig. 1 is the overall structural representation of the present invention;

Fig. 2 is the structural representation of signal collector 4 of the present invention;

Fig. 3 is a sectional view along A-A in Fig. 2;

FIG. 4 is a schematic diagram of the circuit structure of the signal processor 5 of the present invention.

Detailed ways

The present invention is described in detail below in conjunction with accompanying drawing:

An overhead power distribution line zero-sequence current waveform acquisition device capable of resisting interference from adjacent lines, comprising an overhead power distribution line tower 1, a signal processor bracket 7 is arranged on the crossarm 2 of the overhead power distribution line tower 1, and the signal processor The support 7 is provided with a signal processor 5, and the signal processor 5 is connected with the signal collector 4 on the overhead wire 3 through the coaxial cable 6; The voltage signal of the three-phase current waveform of the electric line is input to the respective signal conditioning circuit, and after signal conditioning, it is input to the addition circuit for addition operation, that is, the signal representing the zero-sequence current waveform is output, namely: i0=iA+ iB+ iC.

The signal collector 4 is a double-layer barrel structure, the barrel-shaped outer shell is the confluence shell 13 that leads out of the current, the shape of the barrel-shaped inner shell is an umbrella-shaped curved surface, and the barrel-shaped inner shell is the current inner-lead confluence shell 8B. A second coaxial cable 8A is arranged on the umbrella top of the inner cavity of the barrel-shaped inner shell. The terminals 17 are connected together, and the outer bottom end surface of the barrel-shaped outer shell is connected with an overhead wire connecting end 18, and the second coaxial cable 8A is provided with a high-potential lead-out end 9 for the measurement voltage signal, and on the barrel-shaped inner shell The inner cavity is provided with a measurement voltage signal low potential lead-out terminal 10, and the measurement voltage signal high potential lead-out terminal 9 and the measurement voltage signal low potential lead-out terminal 10 are electrically connected to the signal processor 5 through a coaxial cable 11 for transmitting the measurement voltage signal. Together.

A fan bracket 14 is arranged between the current lead-in bus cable 12 and the barrel-shaped inner shell, and a fan 15 is arranged on the fan bracket 14 .

The signal collector 4 of the present invention is connected in series in the line, and the line current passes through a conductor with a fixed resistance. When grounding occurs, the current of the grounding phase is a transient current with a sudden change effect, and the conductor itself has an inductive effect, which will affect the transient current. The accuracy of the measurement; in addition, when there are harmonics in the line current, the conductor inductance will also affect the measurement of the harmonic current. The present invention designs the conductor of the signal collector 4 as a quadratic coaxial type, effectively reduces the inductance of the conductor, and improves the measurement accuracy of the transient current and the harmonic current. When the line current passes through the conductor with fixed resistance, it will produce thermal effect, which will increase the temperature of the conductor, thereby changing the resistivity of the conductor and affecting the accuracy of current measurement. The present invention designs a cavity structure for the fixed conductor of the signal collector 4, installs a fan, and maintains the conductor in a relatively constant temperature range through the air-cooling method of forced air circulation, avoiding the influence of the temperature rise effect on the measurement accuracy of the line current . The method of directly connecting the metal conductor to the overhead distribution line to measure the current, although the measurement method avoids the interference of the adjacent line on the measurement results compared with the coil measurement method, but there is still the situation that the electromagnetic field of the adjacent line may induce an electric potential on the metal conductor , affecting the measurement accuracy. The invention resists the possible induction potential of the fixed resistance part caused by the electromagnetic field generated by the adjacent line through the method of designing the outer layer metal for the fixed conductor, 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, and the voltage signal output by the signal collector is also small, so that the output voltage signal is transmitted to the signal processing In the process of the converter, there is a possibility of distortion caused by the interference of the electromagnetic field of the adjacent line. The invention adopts the coaxial cable as the transmission cable for measuring the voltage signal, which effectively avoids the interference of the electromagnetic field of the adjacent line on the transmission process of the voltage signal.

What has the function of inducting the measured current signal in the signal collector 4 is that the structure of the sensing part of the signal collector includes the second coaxial cable 8A and the current inner-drawing junction shell 8B, and the current inner-drawing junction shell 8B is a quadric surface. Parts are joined together. The second coaxial cable 8A has a columnar structure, and extends outwards in turn to lead the current into the bus cable 12 and the overhead wire access terminal 17, both of which are of coaxial structure; the current inwardly led out bus shell 8B is an umbrella-shaped curved surface structure, and extends outwards in turn The outgoing current is drawn out from the confluence shell 13 and the overhead wire connection terminal 18 . On the edge of the second coaxial cable 8A and the confluence shell 8B drawn out from the current, there are respectively a high-potential lead-out end 9 of the measurement voltage signal and a low-potential lead-out end 10 of the measurement voltage signal, both of which are axisymmetric with respect to the coaxial cable 8A ring structure. A fan bracket 14 and a fan 15 are installed between the current lead-in confluence cable 12 and the current external lead-out confluence case 13, and a fan energy-taking coil 16 is installed in a ring along the current lead-in confluence part 12 beside the fan 15, and is electrically connected with the fan 15, When working, it supplies power to the fan 15, and the high potential terminal 9 of the measurement voltage signal and the low potential terminal 10 of the measurement voltage signal are electrically connected to the coaxial cable 11 for transmitting the measurement voltage signal, and the first coaxial cable for transmitting the measurement voltage signal 6 is led out from the gap of the fan bracket 14 to the outside of the signal collector, and is electrically connected to the signal processor 5 .

The signal processor 5 has a metal casing 23, and has an A-phase measurement voltage signal input terminal 19, a B-phase measurement voltage signal input terminal 20, a C-phase measurement voltage signal input terminal 21, and a signal output terminal 22 representing zero-sequence current. The first coaxial cable 6 used to transmit the measurement voltage signal is electrically connected to the three measurement voltage signal input terminals of the signal processor 5, and the A phase, B phase, and C phase measurement voltage signal input terminals are connected to the respective signal conditioning circuit input terminals Electrically connected, the output ends of the respective signal conditioning circuits are electrically connected to the input ends of the adding circuit, and the output end of the adding circuit is the signal output end 22 representing the zero-sequence current.

A certain phase of the overhead conductor 3 is electrically connected to the overhead conductor access terminal 17 of the signal collector, so that the current of the distribution line of this phase is introduced into the bus cable 12 through the current and passed into the sensing part of the signal collector, and then led out of the collector shell through the current 13 Lead the distribution line current out of the sensing part of the signal collector, and reintroduce the measured current into the overhead wire 3 through the overhead wire access terminal 18 . The measured current forms a voltage drop in the sensing part of the signal collector 4, and the voltage drop signal is input to the coaxial cable 11 for transmitting the measurement voltage signal through the high-potential lead-out terminal 9 of the measurement voltage signal and the low-potential lead-out terminal 10 of the measurement voltage signal Among them, the coaxial cable 11 for transmitting the measurement voltage signal transmits the potential difference signal to the input terminal of the phase measurement voltage signal of the signal processor 5 . While the signal collector 4 is working, the fan 15 energy-taking coil 16 takes energy through the overhead power distribution line current, and supplies power to the fan 15, and the fan 15 rotates to keep the temperature of the sensing part of the signal collector relatively constant in an air-cooled form. When the power distribution line has no load, the fan 15 stops working because the energy-taking coil 16 cannot supply power to the fan 15. The voltage signals representing the three-phase current waveforms of overhead distribution lines collected by the three signal collectors 4 are input to their respective signal conditioning circuits, and after signal conditioning, they are input to the addition circuit for addition operation, that is, the output represents zero-sequence current waveforms The signal, 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).