CN107796979A - The overhead distribution zero-sequence current waveform acquisition equipment of anti-nearby lines interference - Google Patents

Abstract

The invention discloses an overhead power distribution line zero-sequence current waveform acquisition device capable of resisting interference from adjacent lines, which solves the problem that existing overhead power distribution line zero-sequence current waveform acquisition devices are susceptible to electromagnetic interference from adjacent lines. A signal processor support (7) is provided on the cross arm (2) of the overhead power distribution line tower (1), a signal processor (5) is provided on the signal processor support (7), and the signal processor (5) The signal collector (4) on the overhead wire (3) is connected together through the coaxial cable (6); the signal processor (5) collects the signal collected by the three signal collectors (4) to represent the three phases of the overhead distribution line The voltage signal of the current waveform 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. Accurate zero-sequence current waveforms are collected and accurate judgment of single-phase grounding of transmission wires 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 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 coaxial cable 8A is arranged on the umbrella top of the inner chamber of the barrel-shaped inner shell, and the other end of the coaxial cable 8A is connected with a current lead-in bus cable 12, and the other end of the current lead-in bus cable 12 is connected to the overhead wire access terminal 17 at Together, an overhead wire outlet 18 is connected to the outer bottom end surface of the barrel-shaped outer shell, a high-potential lead-out end 9 for measuring voltage signals is provided on the coaxial cable 8A, and a measurement The voltage signal low potential terminal 10 , the measurement voltage signal high potential terminal 9 and the measurement voltage signal low potential terminal 10 are electrically connected to the signal processor 5 through another coaxial cable 11 .

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 coaxial cable 8A is arranged on the umbrella top of the inner chamber of the barrel-shaped inner shell, and the other end of the coaxial cable 8A is connected with a current lead-in bus cable 12, and the other end of the current lead-in bus cable 12 is connected to the overhead wire access terminal 17 at Together, an overhead wire outlet 18 is connected to the outer bottom end surface of the barrel-shaped outer shell, a high-potential lead-out end 9 for measuring voltage signals is provided on the coaxial cable 8A, and a measurement The voltage signal low potential terminal 10, the measurement voltage signal high potential terminal 9 and the measurement voltage signal low potential terminal 10 are electrically connected to the signal processor 5 through the coaxial cable 11 for transmitting the measurement voltage signal.

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. measurement accuracy; 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.

The structure of the sensing part of the signal collector 4 that has the function of inducting the measured current signal includes a coaxial cable 8A and a current inner-leading confluence shell 8B. The current inner-leading confluence shell 8B is a quadratic surface, and the two parts are connected as one. The coaxial cable 8A has a columnar structure, and the current is extended outward in turn to introduce the bus cable 12 and the overhead wire access terminal 17, both of which are of coaxial structure; The confluence shell 13 and the overhead wire connection terminal 18 are drawn out. On the edge of the 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 rings with respect to the coaxial cable 8A. 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, Power is supplied to the fan 15 during operation, 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 coaxial cable 11 for transmitting the measurement voltage signal is from The gap of the fan bracket 14 leads to the outside of the signal collector, and is electrically connected with 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 coaxial cable 11 for transmitting 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 electrically connected to the respective signal conditioning circuit input terminals, The output terminals of the respective signal conditioning circuits are electrically connected to the input terminals of the adding circuit, and the output terminals of the adding circuit are the signal output terminals 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 signal of. Namely: i0=iA+ iB+iC.

Claims (3)

1. a kind of overhead distribution zero-sequence current waveform acquisition equipment of anti-nearby lines interference, including overhead distribution Shaft tower（1）, it is characterised in that in overhead distribution line line pole tower（1）Cross-arm（2）On be provided with signal processor support（7）, Signal processor support（7）On be provided with signal processor（5）, signal processor（5）Pass through coaxial cable（6）With aerial condutor （3）On signal picker（4）Link together；Signal processor（5）By three signal pickers（4）The sign frame collected The voltage signal of overhand lines three-phase current waveform is input in respective signal conditioning circuit, is input to after signal condition Add circuit makees add operation, i.e. output characterizes the signal of zero-sequence current waveform, i.e.,：i0=iA+ iB+ iC.

A kind of 2. overhead distribution zero-sequence current waveform acquisition dress of anti-nearby lines interference according to claim 1 Put, it is characterised in that signal picker（4）For double-deck barrel-like structure, barrel-shaped outer shell is that the shell that confluxes is drawn outside electric current（13）, bucket Shape hypostracum is shaped as umbrella curve form, and barrel-shaped hypostracum is that the shell that confluxes is drawn in electric current（8B）, in barrel-shaped hypostracum Coaxial cable is provided with the umbrella top of chamber（8A）, coaxial cable（8A）The other end be connected with electric current and introduce and conflux cable（12）, Electric current introduces the cable that confluxes（12）The other end and aerial condutor incoming end（17）Link together, in the outside of barrel-shaped outer shell Aerial condutor is connected with bottom face and picks out end（18）, in coaxial cable（8A）On be provided with measurement voltage signal high potential extraction End（9）, measurement voltage signal low potential exit is provided with barrel-shaped hypostracum inner chamber（10）, measurement voltage signal high potential Exit（9）With measurement voltage signal low potential exit（10）Pass through another coaxial cable（11）With signal processor（5）Electricity Link together.

A kind of 3. overhead distribution zero-sequence current waveform acquisition dress of anti-nearby lines interference according to claim 2 Put, it is characterised in that introduce the cable that confluxes in electric current（12）Blower tray is provided between barrel-shaped hypostracum（14）, in fan Support（14）On be provided with fan（15）.