CN114167115A - Non-contact current sensor, fault monitoring device and method - Google Patents

Abstract

The invention relates to a non-contact current sensor.A shell is hollow and columnar with two open ends, is made of aluminum and is longitudinally distributed; the two end covers respectively cover the ports at the two ends of the shell and are made of resin; the iron core is vertically arranged in the shell and consists of an upper inner core and a lower inner core, the upper inner core is made of a high-magnetic-permeability material, and the lower inner core is made of a low-magnetic-permeability material; the enameled wire is wound on the upper inner core and the lower inner core, and an outer tap is arranged at the transition position of the upper inner core and the lower inner core; one end of the first integrating resistor is electrically connected with the outer tap, and the other end of the first integrating resistor is electrically connected with a tap of the enameled wire wound out of the lower inner core; one end of the second integral resistor is electrically connected with a tap of the enameled wire winding upper inner core, and the other end of the second integral resistor is electrically connected with a tap of the enameled wire winding lower inner core and a public end of the first integral resistor. The invention has the beneficial effects that: the low-current signal in the power grid can be monitored, and the accuracy of fault diagnosis is ensured, so that early warning can be effectively carried out in the future.

Description

Non-contact current sensor, fault monitoring device and method

Technical Field

The invention relates to the technical field of power grids, in particular to a non-contact current sensor, a fault monitoring device and a fault monitoring method.

Background

The rapid development of national economy provides extremely high requirements for the power supply stability of a power transmission line, the spanning distance of the power transmission line is long, and the environment of a line corridor is changeable. The power transmission line is very easy to be disturbed by factors such as lightning stroke, external force damage and the like in the operation process to cause tripping, how to quickly recover power supply after the line is tripped, and the improvement of the satisfaction degree of power supply service is always a relatively concerned problem in the operation and maintenance work of a power grid.

On the other hand, with the implementation of the new enterprise standard of the distributed fault monitoring device of the national power grid transmission line, the actual engineering requirements are combined, the transmission line needs to perform early warning on partial early-warning faults in the operation process, and the fault rate of the transmission line is reduced, so that the requirement for monitoring high-frequency low current generated by the early-warning faults is provided.

At present, a distributed fault monitoring device of a power transmission line is widely applied to a power grid, the device is directly installed on a line body, and the real-time monitoring and diagnosis functions of the faults of the power transmission line can be realized based on a traveling wave current monitoring technology. Because the distributed fault monitoring terminal is installed on the line body, the monitoring equipment is installed in a power failure operation mode, but in actual engineering application, part of important lines cannot be powered off instantly, so that the device has certain limitation in engineering application, and hot-line work has the defect of high cost, so that a device which is convenient for engineering installation and can effectively measure the fault current of the power transmission line is needed to measure the fault traveling wave current and the discharge current small signal.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a non-contact current sensor, a fault monitoring device and a method, so as to overcome the above-mentioned deficiencies in the prior art.

The technical scheme for solving the technical problems is as follows: a non-contact current sensor comprising:

the shell is hollow and is in a column shape with two open ends, is made of aluminum and is longitudinally distributed;

two end covers which respectively cover the ports at the two ends of the shell and are made of resin;

the iron core is vertically arranged in the shell and consists of an upper inner core and a lower inner core, the upper inner core is made of a high-magnetic-permeability material, and the lower inner core is made of a low-magnetic-permeability material;

the enameled wire is wound on the upper inner core and the lower inner core, and an external tap is arranged at the transition position of the upper inner core and the lower inner core;

one end of the first integral resistor is electrically connected with the outer tap, and the other end of the first integral resistor is electrically connected with a tap of the enameled wire wound out of the lower inner core;

and one end of the second integral resistor is electrically connected with a tap of the enameled wire winding upper inner core, and the other end of the second integral resistor is electrically connected with a tap of the enameled wire winding lower inner core and a public end of the first integral resistor.

The invention has the beneficial effects that:

because the abnormal discharge current waveform is measured, the discharge current waveform is usually extremely low in amplitude and milliampere level, so that the upper inner core is made of a high-permeability material to ensure that the discharge current waveform can be effectively collected;

because the fault current is measured, the fault current is usually higher in amplitude, and the distortion of an output waveform caused by the magnetic saturation phenomenon of a coil is prevented, so that the lower inner core is made of a low-magnetic-permeability material;

the combination of an external tap of the enameled wire at the transition position of the upper inner core and the lower inner core, a tap of the enameled wire wound out of the lower inner core and a first integral resistor is used for measuring fault traveling wave current and power frequency current; the combination of a tap of the enameled wire wound out of the upper inner core, a tap of the enameled wire wound out of the lower inner core and a second integral resistor is used for measuring the abnormal discharge traveling wave current; so that the sensor can monitor the small current signal in the power grid, and the accuracy of fault diagnosis is ensured, thereby effectively carrying out early warning in the future.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the high magnetic conductivity material is permalloy; the low permeability material is ABS.

Furthermore, the number of turns of the enameled wire wound on the upper inner core is 20-60 turns, and the number of turns of the enameled wire wound on the lower inner core is 300-500 turns; the resistance value of the first integrating resistor is 30-70 omega, and the resistance value of the second integrating resistor is 800-1200.

The effective effect of the two steps is as follows: the measurement of fault traveling wave current, power frequency current and abnormal discharge traveling wave current can be effectively ensured to be completed.

A fault monitoring device: the system comprises an upper computer, a server in communication connection with the upper computer, and a plurality of monitoring terminals connected with the server;

the monitoring terminal comprises a capacitance voltage division sensor, a conditioning circuit and a non-contact current sensor; the non-contact current sensor is vertically arranged on a line tower in the longitudinal direction, and the conditioning circuit is electrically connected with a tap of the enameled wire wound out of the lower inner core, a tap of the enameled wire wound out of the upper inner core and an outer tap respectively; the capacitance voltage division sensor is arranged below the tested electrified three-phase lead.

The further effective effects are as follows:

the monitoring terminals are arranged on the tower in a distributed mode, long-distance lines are decomposed into a plurality of monitoring points, fault positioning errors caused by attenuation of traveling wave waveforms transmitted to an upper computer from a long distance are avoided, and positioning accuracy is effectively improved;

the non-contact current sensor is directly installed on a tower, the tower is at the ground potential, and the non-contact current sensor is not electrically connected with the line body, so that the non-contact current sensor can be installed in a live mode, is not influenced by a line power failure plan, and is more flexible in engineering installation.

Furthermore, the conditioning circuit comprises a first-stage amplifying circuit, a second-stage amplifying circuit, a filter circuit, a phase-shifting circuit and a gain adjusting circuit, wherein one output of the first-stage amplifying circuit is sequentially connected with the filter circuit, the phase-shifting circuit and the gain adjusting circuit, and the other output of the first-stage amplifying circuit is sequentially connected with the second-stage amplifying circuit and the gain adjusting circuit.

Further, the capacitive voltage division sensor includes:

a metal sheet arranged below the line and forming a coupling capacitor C with the line₁And form a grounding capacitance C with the ground₂；

Sampling capacitor C_M1The damping resistor R is connected in series and then connected in parallel with the coupling capacitor C₁Two ends.

The further effective effects are as follows: and the cable is not electrically connected with the line body, so that the cable can be installed in a live mode, the cable is not influenced by a line power failure plan, and the engineering installation is more flexible.

A fault monitoring method adopts the fault monitoring device; the method specifically comprises the following steps:

s100, the monitoring terminal periodically collects the traveling wave current and traveling wave voltage of the line at the non-fault moment and temporarily stores the traveling wave current and traveling wave voltage to obtain a traveling wave current waveform sequence xbdl at the non-fault moment₁And a sequence of travelling wave voltage waveforms xbdy₁；

S200, monitoring fault triggering of a terminal to acquire traveling wave current and traveling wave voltage at the fault triggering moment of a line, storing the traveling wave current and the traveling wave voltage and acquiring a traveling wave current waveform sequence xbdl at the fault moment₂And a sequence of travelling wave voltage waveforms xbdy₂；

S300, calculating a correlation coefficient of the waveform at the fault moment and the temporary storage waveform at the non-fault moment to obtain a current correlation coefficient rho_dl1And voltage correlation coefficient ρ_dy1；

S400, recombining the inner volumes of the waveform sequence stored at the fault moment to obtain a new traveling wave current waveform sequence xbdl_cz1The sequence of travelling wave voltage waveforms xbdy_cz1And calculating the current correlation coefficient rho after waveform recombination according to the waveform sequence after waveform recombination and the waveform sequence at the non-fault time_dl2And voltage correlation coefficient ρ_dy2；

S500, repeating the step S400 for n times to obtain a fault moment recombined traveling wave current waveform sequence xbdl_cznAnd recombining the traveling wave voltage waveform group sequence xbdy_cznAnd repeating the sequence for 1 time, and calculating the correlation coefficient rho of the waveform sequence after 1 time of recombination and the waveform sequence at the non-fault moment_dlnAnd ρ_dynRespectively taking phase relationsThe value having the largest absolute value is recorded as the judgment reference data as max | ρ_dln|，max|ρ_dyn|；

S600, taking the maximum correlation coefficient of the traveling wave voltage as a judgment basis;

judging max | rho_dyn|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S800;

if the condition that the traveling wave voltage is not collected exists at the fault moment or the non-fault moment, taking the traveling wave current as a judgment basis:

judging max | rho_dln|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S700;

s700, amplifying, filtering, phase shifting and gain adjusting the traveling wave current at the fault triggering moment, and transmitting the traveling wave current to a server;

s800, judging the polarities of traveling wave voltages transmitted back by two monitoring terminals in all monitoring terminals on the same line, if the traveling wave voltages are the same, discarding the traveling wave voltages, reselecting the two monitoring terminals for judging again, and if the traveling wave voltages are not the same, uploading the waveforms to an upper computer;

if the terminal does not return the traveling wave voltage, the traveling wave current is taken as a judgment basis, and the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

Further, in S200, the monitoring terminal fault triggering is performed by power frequency voltage change threshold triggering, power frequency current change threshold triggering, or traveling wave voltage threshold triggering.

Further, the method for recombining the inner roll in S400 comprises the following steps:

the last sampling point of the waveform sequence is moved to be the first sampling point of the waveform sequence, and the rest sampling points are all moved backwards by one bit.

Further, S700 specifically is:

s810, uploading terminal operation condition information to a server by all monitoring terminals;

s820, the server sorts the monitoring terminals on the same line from high to low according to the working condition information uploaded by the monitoring terminals;

s830, the server selects two monitoring terminals with the highest electric quantity to send a command to be triggered, and the monitoring terminals receive the command to be triggered;

s840, triggering faults of the two monitoring terminals;

s850, the two monitoring terminals send trigger marks to the server and send back a waveform polarity transmission instruction;

and S860, the monitoring terminal judges the waveform polarity according to the voltage traveling wave and transmits a polarity flag bit back to the server, wherein the positive polarity is 0 and the negative polarity is 1.

S870, the terminal monitors a voltage traveling wave waveform sequence, finds out a point with the maximum absolute value, the sequence number of the point is marked as index, sequentially pushes forward and backward b sampling points, judges whether the symbol of the point is the same as the symbol of the point of the index, if so, the rule is satisfied, the polarity of the sampling point with the sequence number of the index is the polarity of the waveform, if not, finds out a point with the second absolute value of the sampling point, and carries out the judgment again until the rule is satisfied;

s880, sequencing all the monitoring terminals on the same line according to the electric quantity, enabling the two monitoring terminals with the optimal electric quantity to transmit back voltage traveling waves, judging the polarity of the voltage traveling waves, if the two monitoring terminals have the same polarity, abandoning the voltage traveling waves, reselecting the two monitoring terminals with the next electric quantity for repeated judgment, and if the two monitoring terminals have no same polarity, uploading waveforms;

s890, if the terminal does not return the traveling wave voltage, taking the traveling wave current as a judgment basis, wherein the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

The beneficial effect of adopting the four steps is as follows:

the parameters of the monitoring terminal can be dynamically adjusted according to different lines, line faults can be individually monitored according to the obstructed environment of the lines, and the pertinence and the reliability are higher;

the multi-channel collection is adopted, and the collected waveforms are screened at the server, so that the data volume required to be uploaded by the monitoring terminal is greatly reduced, and the operational reliability of the monitoring terminal can be integrally improved.

Drawings

FIG. 1 is a wiring diagram of a non-contact current sensor and conditioning circuit according to the present invention;

FIG. 2 is a layout diagram of metal sheets in the capacitive voltage divider sensor according to the present invention;

FIG. 3 is a schematic diagram of a capacitive voltage divider sensor according to the present invention;

FIG. 4 is a schematic diagram of the conditioning circuit of the present invention;

in the drawings, the components represented by the respective reference numerals are listed below:

1. the non-contact type current sensor comprises a non-contact type current sensor body, 110, a shell, 120, an upper inner core, 130, a lower inner core, 140, an enameled wire, 150, an outer tap, 160, a first integrating resistor, 170, a second integrating resistor, 2, a capacitance voltage division sensor, 210, a metal sheet, 3, a conditioning circuit, 310, a first-stage amplifying circuit, 320, a second-stage amplifying circuit, 330, a filtering circuit, 340, a phase-shifting circuit, 350 and a gain adjusting circuit.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

Example 1

The non-contact current sensor 1 needs to measure fault traveling wave current (several amperes to several thousands amperes), abnormal discharge traveling wave current (several milliamperes to several amperes), and power frequency current (ampere level);

therefore, a non-contact current sensor 1 with a specific structure is designed, as shown in fig. 1, and the specific structure thereof is as follows:

the noncontact current sensor 1 includes: the outer shell 110, the end cover, the upper inner core 120, the lower inner core 130, the enameled wire 140, the first integral resistor 160 and the second integral resistor 170;

the shell 110 is hollow and columnar, two ends of the shell are open, the shell 110 is made of aluminum, the shell 110 is vertically arranged on a line tower in the longitudinal direction, and the shell 110 can shield interference signals of an external electromagnetic field;

the two end covers respectively cover the ports at the two ends of the shell 110, and the two end covers are made of resin materials with higher strength and stronger corrosion resistance, so that the magnetic field of effective signals can penetrate through the interior of the shell to be measured subsequently;

the upper inner core 120 is vertically arranged in the outer shell 110, and because the abnormal discharge current waveform is measured, the discharge current waveform is usually extremely low in amplitude and in milliampere level, the upper inner core 120 is made of a high-permeability material so as to ensure that the discharge current waveform can be effectively collected; the lower inner core 130 is vertically arranged in the outer shell 110, and because the fault current is measured, the fault current is generally high in amplitude, the distortion of an output waveform caused by the magnetic saturation phenomenon of a coil is prevented, so that the lower inner core 130 is made of a low-magnetic-permeability material;

the enameled wire 140 is wound on the upper inner core 120 and the lower inner core 130, and an external tap 150 is arranged at the transition position of the upper inner core 120 and the lower inner core 130 on the enameled wire 140;

a tap of the enameled wire 140 wound out of the upper inner core 120, a tap of the enameled wire 140 wound out of the lower inner core 130, and an external tap 150 of the enameled wire 140 at the transition position of the upper inner core 120 and the lower inner core 130 are respectively connected with a conditioning circuit 160;

one end of the first integral resistor 160 is electrically connected to the outer tap 150, and the other end of the first integral resistor 160 is electrically connected to a tap of the enameled wire 140 wound out of the lower inner core 130;

one end of the second integral resistor 170 is electrically connected with a tap of the enameled wire 140 wound out of the upper inner core 120, and the other end of the second integral resistor 170 is electrically connected with a tap of the enameled wire 140 wound out of the lower inner core 130 and a common end of the first integral resistor 160;

the combination of the external tap 150 of the enameled wire 140 at the transition of the upper inner core 120 and the lower inner core 130, the tap of the enameled wire 140 wound out of the lower inner core 130 and the first integral resistor 160 is used for measuring fault traveling wave current and power frequency current;

the combination of the tap of the enamel wire 140 wound out of the upper inner core 120, the tap of the enamel wire 140 wound out of the lower inner core 130 and the second integral resistor 170 is used to measure the abnormal discharging traveling wave current.

Example 2

This example is a further optimization performed on the basis of example 1, and specifically includes the following:

the high magnetic permeability material is preferably permalloy; the low permeability material is preferably non-magnetically permeable ABS.

Example 3

This example is a further optimization performed on the basis of example 1 or 2, and is specifically as follows:

the number of turns of the enamel wire 140 wound on the upper inner core 120 is less than that of the enamel wire 140 wound on the lower inner core 130;

in general, the number of turns of the enameled wire 140 wound on the upper inner core 120 is 20 to 60 turns, and the number of turns of the enameled wire 140 wound on the lower inner core 130 is 300 to 500 turns.

The resistance of the first integrating resistor 160 is smaller than the resistance of the second integrating resistor 170;

in general, the resistance of the first integrating resistor 160 is 30-70 Ω, and the resistance of the second integrating resistor 170 is 800-1200 Ω, so as to implement the integral measurement of the fault current, the abnormal discharge current and the power frequency current.

Example 4

As shown in fig. 1 to 4, a fault monitoring device includes an upper computer, a server and a monitoring terminal; the monitoring terminals are respectively connected with a server, and the server is in communication connection with an upper computer;

the monitoring terminal comprises a non-contact current sensor 1, a capacitance voltage division sensor 2 and a conditioning circuit 3; the non-contact current sensor 1 is vertically arranged on a line tower in the longitudinal direction, and the conditioning circuit 3 is electrically connected with a tap of the enameled wire 140 wound out of the lower inner core 130, a tap of the enameled wire 140 wound out of the upper inner core 120 and an outer tap 150 respectively; the capacitance voltage division sensor 2 is arranged below the tested electrified three-phase lead; the capacitance voltage division sensor 2 and the conditioning circuit 3 are respectively connected with the server.

Example 5

As shown in fig. 4, this embodiment is further optimized based on embodiment 4, and the specific details thereof are as follows:

the conditioning circuit 3 comprises a primary amplifying circuit 310, a secondary amplifying circuit 320, a filter circuit 330, a phase-shifting circuit 340 and a gain adjusting circuit 350;

the first-stage amplification circuit 310: the OUTPUT signal of the current sensor is used as an INPUT signal of the circuit, and OUTPUT is OUTPUT after the INPUT signal is amplified;

the filter circuit 330: taking an OUTPUT signal of the OUTPUT of the first-stage amplifying circuit 310 as an INPUT signal of the circuit, filtering the OUTPUT signal, removing inherent noise waveforms of the circuit, and outputting the filtered OUTPUT signal;

the phase shift circuit 340: taking the OUTPUT signal of the OUTPUT of the filter circuit 330 as the INPUT signal of the circuit, and outputting the OUTPUT after phase shifting;

the secondary amplification circuit 320: taking the OUTPUT signal of the first-stage amplifying circuit 310 as the INPUT signal of the circuit, and outputting the OUTPUT signal after amplifying again;

the gain adjustment circuit 350:

the OUTPUT signal of the phase shift circuit 340 is used as the INPUT signal 1 of the INPUT1 of the circuit, the OUTPUT signal of the secondary amplifying circuit 320 is used as the INPUT signal 2 of the INPUT2 of the circuit, and the gain multiple of the collected signal is restored.

The specific circuit connection is as follows: one output of the first-stage amplifying circuit 310 is connected to the filter circuit 330, the phase-shifting circuit 340 and the gain adjusting circuit 350 in sequence, and the other output of the first-stage amplifying circuit 310 is connected to the second-stage amplifying circuit 320 and the gain adjusting circuit 350 in sequence.

Example 6

As shown in fig. 2 and fig. 3, this embodiment is a further optimization performed on the basis of embodiment 4 or 5, and the specific details thereof are as follows:

the capacitive voltage division sensor 2 includes: sheet metal 210 and sampling capacitor C_MAnd a damping resistor R₁；

The metal sheet 210 is arranged below the tested electrified three-phase lead, and a coupling capacitor C is formed between the tested electrified three-phase lead and the metal sheet 210₁The metal sheet 210 forms a grounding capacitor C₂，C₁And C₂Will form a capacitance voltage-dividing capacitor at C₁Two-end parallel sampling capacitor C_MAnd resistorDamping resistance R₁Realize voltage measurement, sample voltage u_mThe voltage signal is measured by satisfying the following relation with the line voltage u;

example 7

Due to the fact that the line environment is complex, a plurality of interference waveforms exist on the line, the interference waveforms have the characteristic of stable waveform form, if the interference waveforms are not processed, the monitoring terminal can be triggered by mistake, a plurality of invalid signals are uploaded, the data volume is greatly increased, and the power consumption of the monitoring terminal is improved, so that the fault monitoring method is designed, the inherent interference waveforms of the line are removed, and low-power-consumption operation of the monitoring terminal is guaranteed;

the method specifically comprises the following steps:

s100, the monitoring terminal periodically collects traveling wave current and traveling wave voltage signals of the line at the non-fault moment, temporarily stores the traveling wave current and traveling wave voltage signals, and records a traveling wave current waveform sequence xbdl at the non-fault moment₁＝[x₁,x₂,x₃...x_n]And a sequence of travelling wave voltage waveforms xbdy₁＝[y₁,y₂,y₃...y_n]；

S200, monitoring normal operation of a terminal, detecting and triggering, monitoring fault triggering of the terminal, collecting traveling wave current and traveling wave voltage at the fault triggering moment of a line, storing, and recording a traveling wave current waveform sequence xbdl at the fault moment₂＝[z₁,z₂,z₃...z_n]Traveling wave voltage waveform sequence xbdy₂＝[w₁,w₂,w₃...w_n]；

S300, calculating a current-related coefficient p according to the fault moment waveform sequence and the non-fault moment waveform sequence_dl1Voltage correlation coefficient p_dy1；

S400, carrying out involution recombination on the waveform sequence obtained at the fault moment to obtain a new traveling wave current waveform sequence

Travelling wave voltage waveform sequence

And according to the recombined waveform sequence

Non-fault moment waveform sequence xbdl₁＝[x₁,x₂,x₃...x_n]、xbdy₁＝[y₁,y₂,y₃...y_n]Calculating the current correlation coefficient rho after waveform recombination_dl2Voltage correlation coefficient ρ_dy2；

S500, repeating the step S400 for n times to obtain a fault moment recombination traveling wave current waveform sequence

Recombination traveling wave voltage waveform group sequence

And the calculation is carried out once per cycle, and the correlation coefficient rho of the waveform sequence after once recombination and the waveform sequence at the non-fault moment is calculated_dlnAnd ρ_dynAnd respectively taking the maximum absolute value of the correlation coefficient as the judgment reference data to be recorded as max | rho_dln∣,max∣ρ_dyn∣；

S600, taking the maximum correlation coefficient of the traveling wave voltage as a judgment basis,

judging max | rho_dyn|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S800;

if the condition that the traveling wave voltage is not collected exists at the fault moment or the non-fault moment, the traveling wave current is used as a judgment basis,

judging max | rho_dln|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S700;

s700, amplifying, filtering, phase shifting and gain adjusting the traveling wave current at the fault triggering moment, and transmitting the traveling wave current to a server;

s800, judging the polarities of traveling wave voltages transmitted back by two monitoring terminals in all monitoring terminals on the same line, if the traveling wave voltages are the same, discarding the traveling wave voltages, reselecting the two monitoring terminals for judging again, and if the traveling wave voltages are not the same, uploading the waveforms to an upper computer;

if the terminal does not return the traveling wave voltage, the traveling wave current is taken as a judgment basis, and the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

Example 8

This example is a further optimization performed on the basis of example 7, and it is specifically as follows:

in S200, the fault triggering of the monitoring terminal adopts power frequency voltage change threshold triggering, power frequency current change threshold triggering or traveling wave voltage threshold triggering.

Trigger threshold for industrial frequency voltage change

Setting normal operation voltage U of the tested electrified three-phase conductor, and according to the requirement of the power grid on the quality of the line operation voltage, if the sum of the absolute values of the positive and negative deviations of the voltage does not exceed 10% of the rated value, then the change threshold value of the part is delta U₁＝0.1U；

Because the output of the capacitive voltage division sensor 2 is related to the distance, and the positions of the mounting point of the monitoring terminal and the upper conductor are not absolutely symmetrical, the voltage change threshold caused by the asymmetry of the mounting point is considered, and the calculation can be carried out according to the following formula;

calculating a voltage change threshold Δ U₂；

In the formula: d_A、d_B、d_CRespectively the distance between the installation point of the capacitance voltage division sensor 2 and the tested electrified three-phase lead,

is d_A、d_B、d_CAverage value of (i), i.e.

In order to reduce false triggering of the monitoring terminal as much as possible and achieve the purpose of reducing power consumption and data transmission quantity, a reliable coefficient mu of a threshold value can be set, the value of mu is 1-1.2, adjustment is performed according to the running condition, the initial value is 1, and then the power frequency voltage change threshold value is as follows:

Δu＝μ*(ΔU₁+ΔU₂)；

trigger threshold value for power frequency current change

Considering the measurement error of the non-contact current sensor, triggering a threshold value coefficient delta v according to the actual error value p% of the designed non-contact current sensor (the measurement error range of the parameter sensor given by the invention is 10 percent)₁＝1+p％；

The output of the non-contact current sensor is related to the installation point of the monitoring terminal, and the variable current caused by the asymmetry of the installation point and the coefficient delta v caused by the asymmetry of the installation point are considered₂；

In the formula: d_A、d_B、d_CRespectively the distance between the mounting point of the non-contact current sensor (1) and the tested electrified three-phase lead,

is d_A、d_B、d_CAverage value of (i), i.e.

Because the non-contact current sensor is arranged on a tower to collect three-phase synthetic voltage, zero-sequence current in power grid relay protection can be used as a reference value, a trigger threshold value is set, the zero-sequence current can be inquired from the relay protection, the maximum value is taken, and the inquiry value is set to be delta i_lAnd then the power frequency current change trigger threshold setting value is as follows: Δ i ═ Δ ν₁*Δν₂*Δi_l；

Travelling wave voltage trigger threshold

The waveform amplitude of the inherent interference traveling wave voltage acquired by the traveling wave voltage acquisition circuit is set to be

The traveling wave voltage change trigger threshold is set to

Example 9

This example is a further optimization performed on the basis of example 7, and it is specifically as follows:

the method for calculating the current correlation coefficient in S300 includes:

the method for calculating the voltage correlation coefficient in S300 includes:

example 10

This example is a further optimization performed on the basis of example 7, and it is specifically as follows:

the method for recombining the inner roll in the S400 comprises the following steps:

the last sampling point of the waveform sequence is moved to be the first sampling point of the waveform sequence, and the other sampling points are all moved backwards by one bit, if the traveling wave current waveform after the fault is according to the sampling pointRegularly recombining, the new waveform sequence is xbdl_cz1＝[z_n,z₁,z₂,z₃...z_n-1]After the traveling wave voltage is recombined according to the rule, the new waveform sequence is xbdy_cz1＝[w_n,w₁,w₂,w₃...w_n-1]。

Example 11

This example is a further optimization based on example 7 or 10, and the specific details are as follows:

current correlation coefficient rho after waveform recombination in S400_dl2Voltage correlation coefficient ρ_dy2The calculation method comprises the following steps:

example 12

This example is a further optimization performed on the basis of example 7, and it is specifically as follows:

because the action range of the power transmission line fault monitoring terminal only aims at the line section between the two installation points, and fault diagnosis is not needed for the lines outside the monitoring section, the collected data is further effectively judged so as to reduce the data volume.

The sequence of a line installation point from a small station to a large station is set, and the waveform sequence of the traveling wave of the voltage collected by the 1# monitoring terminal is u_xb1＝[a₁,a₂,a₃...a_n]And the waveform sequence of the traveling wave voltage collected by the 2# monitoring terminal is u_xb2＝[b₁,b₂,b₃...b_n]And by analogy, as the monitoring terminals need to keep low power consumption operation, and the power consumption of the data transmission module is mainly higher at the monitoring terminals, each monitoring terminal uploads signals in the following manner after acquiring the trigger waveform.

S800 specifically comprises the following steps:

s810, uploading terminal operation condition information to a server by all monitoring terminals;

s820, the server sorts the monitoring terminals on the same line from high to low according to the working condition information uploaded by the monitoring terminals;

s830, the server selects two monitoring terminals with the highest electric quantity to send a command to be triggered, and the monitoring terminals receive the command to be triggered;

s840, triggering faults of the two monitoring terminals;

s850, the two monitoring terminals send trigger marks to the server and send back a waveform polarity transmission instruction;

and S860, the monitoring terminal judges the waveform polarity according to the voltage traveling wave and transmits a polarity flag bit back to the server, wherein the positive polarity is 0 and the negative polarity is 1.

S870, monitoring the voltage traveling wave waveform sequence u by the terminal_xb1＝[a₁,a₂,a₃...a_n]Finding out a point with the maximum absolute value, wherein the sequence number of the point is marked as index, in order to eliminate a part of spike-type interference items in a line, sequentially pushing forward and backward b sampling points (according to different values of sampling rates, the embodiment proposes to take a point with the length of 5us as a decision point), judging whether the sign of the point is the same as that of the index, if so, satisfying the rule, and if not, finding a point with the next absolute value of the sampling point, and performing the judgment again until the rule is satisfied;

s880, sequencing all the monitoring terminals on the same line according to the electric quantity, enabling the two monitoring terminals with the optimal electric quantity to transmit back voltage traveling waves, judging the polarity of the voltage traveling waves, if the two monitoring terminals have the same polarity, abandoning the voltage traveling waves, reselecting the two monitoring terminals with the next electric quantity for repeated judgment, and if the two monitoring terminals have no same polarity, uploading waveforms;

wherein, homopolar indicates that the fault point is not in the two terminal monitoring sections, and reverse polarity indicates that the fault point is in the monitoring sections;

s890, if the terminal does not return the traveling wave voltage, taking the traveling wave current as a judgment basis, wherein the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

Example 13

This example is a further optimization performed on the basis of example 12, and it is specifically as follows:

for the convenience of understanding the content of S870, an example is given:

terminal monitoring voltage traveling wave waveform sequence u_xb1＝[a₁,a₂,a₃...a_n]The corresponding serial numbers of the points are [1,2,3.. n ]]If the serial number corresponding to the point with the maximum absolute value of the sampling point value is the 100 th and the sign is negative, whether the signs of the values of the sampling points with the serial numbers of [ -1b0-0b +,1b-00+1 are all negative is judged, if yes, the polarity of the voltage traveling wave waveform sequence is negative, if not, the point with the second absolute value of the sampling point value is found, the operation is carried out again until the point meeting the requirement is found, and the waveform polarity is judged.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. A non-contact current sensor, comprising:

the shell (110) is hollow and columnar with two open ends, is made of aluminum and is longitudinally distributed;

two end covers which respectively cover the ports at the two ends of the shell (110) and are made of resin;

the iron core is vertically arranged in the shell (110) and consists of an upper inner core (120) and a lower inner core (130), the upper inner core (120) is made of a high-permeability material, and the lower inner core (130) is made of a low-permeability material;

the enameled wire (140) is wound on the upper inner core (120) and the lower inner core (130), and an external tap (150) is arranged at the transition position of the upper inner core (120) and the lower inner core (130);

a first integral resistor (160) having one end electrically connected to the outer tap (150) and the other end electrically connected to a tap of the enameled wire (140) wound out of the lower inner core (130);

and one end of the second integral resistor (170) is electrically connected with a tap of the enameled wire (140) wound out of the upper inner core (120), and the other end of the second integral resistor is electrically connected with a tap of the enameled wire (140) wound out of the lower inner core (130) and a common end of the first integral resistor (160).

2. A contactless current sensor (1) according to claim 1, characterized in that: the high-permeability material is permalloy; the low magnetic permeability material is ABS.

3. A contactless current sensor (1) according to claim 1 or 2, characterized in that: the number of turns of the enameled wire (140) wound on the upper inner core (120) is 20-60 turns, and the number of turns of the enameled wire (140) wound on the lower inner core (130) is 300-500 turns; the resistance value of the first integrating resistor (160) is 30-70 omega, and the resistance value of the second integrating resistor (170) is 800-1200 omega.

4. A fault monitoring device, characterized by: the monitoring system comprises an upper computer, a server in communication connection with the upper computer, and a plurality of monitoring terminals connected with the server;

the monitoring terminal comprises a capacitance voltage division sensor (2), a conditioning circuit (3) and the non-contact current sensor (1) according to claims 1-3; the non-contact current sensor (1) is vertically arranged on a line tower in the longitudinal direction, and the conditioning circuit (3) is electrically connected with a tap of an enameled wire (140) wound out of a lower inner core (130), a tap of the enameled wire (140) wound out of an upper inner core (120) and an outer tap (150) respectively; and the capacitance voltage division sensor (2) is arranged below the tested electrified three-phase lead.

5. A fault monitoring device according to claim 4, wherein: the conditioning circuit (3) comprises a first-stage amplifying circuit (310), a second-stage amplifying circuit (320), a filter circuit (330), a phase-shifting circuit (340) and a gain adjusting circuit (350), wherein one output of the first-stage amplifying circuit (310) is connected with the filter circuit (330), the phase-shifting circuit (340) and the gain adjusting circuit (350) in sequence, and the other output of the first-stage amplifying circuit (310) is connected with the second-stage amplifying circuit (320) and the gain adjusting circuit (350) in sequence.

6. A fault monitoring device according to claim 4 or 5, wherein:

the capacitive voltage division sensor (2) comprises:

a metal sheet (210) disposed under the wiring and forming a coupling capacitance C with the wiring₁And form a capacitance to ground C with the earth₂；

Sampling capacitor C_M1The damping resistor R is connected in series and then connected in parallel with the coupling capacitor C₁Two ends.

7. A fault monitoring method, characterized by: using the fault monitoring device of claim 4 or 5 or 6;

the method comprises the following steps:

s100, the monitoring terminal periodically collects the traveling wave current and traveling wave voltage of the line at the non-fault moment and temporarily stores the traveling wave current and traveling wave voltage to obtain a traveling wave current waveform sequence xbdl at the non-fault moment₁And a sequence of travelling wave voltage waveforms xbdy₁；

S200, monitoring fault triggering of a terminal to acquire traveling wave current and traveling wave voltage at the fault triggering moment of the line, storing the traveling wave current and the traveling wave voltage, and acquiring a traveling wave current waveform sequence xbdl at the fault moment₂And a sequence of travelling wave voltage waveforms xbdy₂；

S300, calculating a correlation coefficient of a fault moment waveform and a non-fault moment temporary storage waveform to obtain a current correlation coefficient rho_dl1And voltage correlation coefficient ρ_dy1；

S400, recombining the inner volumes of the waveform sequence stored at the fault moment to obtain a new traveling wave current waveform sequence xbdl_cz1The sequence of travelling wave voltage waveforms xbdy_cz1And according to the recombined waveform sequence and non-fault time waveformSequence, calculating the current correlation coefficient rho after waveform recombination_dl2And voltage correlation coefficient ρ_dy2；

S500, repeating the step S400 for n times to obtain a fault moment recombined traveling wave current waveform sequence xbdl_cznAnd recombining the traveling wave voltage waveform group sequence xbdy_cznAnd repeating the sequence for 1 time, and calculating the correlation coefficient rho of the waveform sequence after 1 time of recombination and the waveform sequence at the non-fault moment_dlnAnd ρ_dynThe maximum absolute value of the correlation coefficient is taken as the judgment reference data and recorded as max | rho_dln|，max|ρ_dyn|；

S600, taking the maximum correlation coefficient of the traveling wave voltage as a judgment basis;

judging max | rho_dyn|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S800;

if the condition that the traveling wave voltage is not collected exists at the fault moment or the non-fault moment, taking the traveling wave current as a judgment basis:

judging max | rho_dln|≥k，0≤k≤1；

If the condition is met, the waveforms at the fault moment are abandoned, and if the condition is not met, the operation goes to S700;

s700, amplifying, filtering, phase shifting and gain adjusting the traveling wave current at the fault triggering moment, and transmitting the traveling wave current to a server;

s800, judging the polarities of traveling wave voltages transmitted back by two monitoring terminals in all monitoring terminals on the same line, if the traveling wave voltages are the same, discarding the traveling wave voltages, reselecting the two monitoring terminals for judging again, and if the traveling wave voltages are not the same, uploading the waveforms to an upper computer;

if the terminal does not return the traveling wave voltage, the traveling wave current is taken as a judgment basis, and the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

8. A fault monitoring method according to claim 7, characterized in that: in S200, the fault triggering of the monitoring terminal adopts power frequency voltage change threshold triggering, power frequency current change threshold triggering or traveling wave voltage threshold triggering.

9. A fault monitoring method according to claim 7 or 8, characterized in that: the method for recombining the inner roll in the S400 comprises the following steps:

the last sampling point of the waveform sequence is moved to be the first sampling point of the waveform sequence, and the rest sampling points are all moved backwards by one bit.

10. A fault monitoring method according to claim 7, 8 or 9, wherein: the S800 specifically comprises the following steps:

s810, uploading terminal operation condition information to a server by all monitoring terminals;

s820, the server sorts the monitoring terminals on the same line from high to low according to the working condition information uploaded by the monitoring terminals;

s830, the server selects two monitoring terminals with the highest electric quantity to send a command to be triggered, and the monitoring terminals receive the command to be triggered;

s840, triggering faults of the two monitoring terminals;

s850, the two monitoring terminals send trigger marks to the server and send back a waveform polarity transmission instruction;

and S860, the monitoring terminal judges the waveform polarity according to the voltage traveling wave and transmits a polarity flag bit back to the server, wherein the positive polarity is 0 and the negative polarity is 1.

S870, the terminal monitors a voltage traveling wave waveform sequence, finds out a point with the maximum absolute value, the sequence number of the point is marked as index, sequentially pushes forward and backward b sampling points, judges whether the symbol of the point is the same as the symbol of the point of the index, if so, the rule is satisfied, the polarity of the sampling point with the sequence number of the index is the polarity of the waveform, if not, finds out a point with the second absolute value of the sampling point, and carries out the judgment again until the rule is satisfied;

s880, sequencing all the monitoring terminals on the same line according to the electric quantity, enabling the two monitoring terminals with the optimal electric quantity to transmit back voltage traveling waves, judging the polarity of the voltage traveling waves, if the two monitoring terminals have the same polarity, abandoning the voltage traveling waves, reselecting the two monitoring terminals with the next electric quantity for repeated judgment, and if the two monitoring terminals have non-same polarity, uploading waveforms;

s890, if the terminal does not return the traveling wave voltage, taking the traveling wave current as a judgment basis, wherein the judgment mode is the same as the traveling wave voltage judgment mode;

and if the traveling wave voltage and the traveling wave current have no data, discarding the terminal without data, and reselecting other terminals on the line.

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