CN110879308B - Zero zone current measuring device and control method thereof - Google Patents

Zero zone current measuring device and control method thereof Download PDF

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Publication number
CN110879308B
CN110879308B CN201911166316.7A CN201911166316A CN110879308B CN 110879308 B CN110879308 B CN 110879308B CN 201911166316 A CN201911166316 A CN 201911166316A CN 110879308 B CN110879308 B CN 110879308B
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China
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current
measurement
switch
current meter
circuit
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CN110879308A (en
Inventor
莫文雄
王勇
刘俊翔
朱璐
苏海博
乔胜亚
张显聪
彭和平
袁召
刘黎明
陈立学
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Huazhong University of Science and Technology
Guangzhou Power Supply Bureau Co Ltd
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Huazhong University of Science and Technology
Guangzhou Power Supply Bureau Co Ltd
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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
    • G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero
    • 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
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Testing Relating To Insulation (AREA)

Abstract

The invention relates to a zero zone current measuring device and a control method thereof. The zero zone current measuring device comprises an oscillating circuit, a vacuum arc-extinguishing chamber and a measuring circuit which are connected in series. The vacuum arc extinguish chamber is used for controlling the on-off of a circuit between the oscillating circuit and the measuring circuit. The measuring circuit comprises a first measuring branch, a second measuring branch and a third measuring branch which are connected in parallel. The first measuring branch, the second measuring branch and the third measuring branch are respectively provided with a current meter. Therefore, after the zero zone current control device is conducted to form a loop, currents in different stages before and after the vacuum arc extinguish chamber is disconnected can be measured by matching the disconnection of the vacuum arc extinguish chamber and the respective conduction of different measuring branches, and the purpose of measuring the zero zone current before and after the breaker is disconnected is achieved.

Description

Zero zone current measuring device and control method thereof
Technical Field
The invention relates to the technical field of zero zone current measurement of circuit breakers, in particular to a zero zone current measuring device and a control method thereof.
Background
In recent years, with the development of flexible direct current transmission technology and the progress of high-power electronic technology, high-voltage direct current transmission is valued and developed with its unique advantages. The circuit breaker is a core device for protecting the safe operation of the power system.
In order to improve the breaking capacity of a circuit breaker in high voltage direct current transmission, it is necessary to intensively study the characteristics of a vacuum arc. And accurately acquiring the numerical value of zero zone current before and after the breaker is switched on has great significance for deeply researching the characteristics of the vacuum arc.
The inventor finds out in the process of realizing the conventional technology that: in the conventional technology, a device for measuring zero zone current before and after the circuit breaker is switched on and switched off is lacked, and the zero zone current before and after the circuit breaker is switched on and switched off is difficult to measure.
Disclosure of Invention
Therefore, it is necessary to provide a zero zone current measuring apparatus and a control method thereof to solve the problem that it is difficult to measure zero zone current before and after the circuit breaker is opened in the conventional technology.
A zero zone current measurement device comprising: an oscillating circuit for generating an oscillating current, the oscillating circuit having a first output and a second output; a measurement circuit connected between the first output terminal and the second output terminal; the measuring circuit comprises a first measuring branch, a second measuring branch and a third measuring branch which are connected in parallel, wherein the first measuring branch comprises a switch VT1 and a current meter A1 which are connected in series; the second measuring branch comprises a switch VT2 and a current meter A2 connected in series; the third measuring branch comprises a sampling resistor R1 and a current meter A3 which are connected in series; and the vacuum arc extinguish chamber is connected between the first output end and the measuring circuit so as to control the circuit connection and disconnection between the first output end and the measuring circuit.
In one embodiment, the zero zone current measuring device further includes: and the controller is connected with the current meter A1, the current meter A2, the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber, and is used for acquiring the measurement results of the current meter A1 and the current meter A2 and controlling the on-off of the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber.
In one embodiment, the second output terminal is connected to a ground GND; the measuring circuit further comprises a thyristor SCR connected with the first measuring branch in parallel, and the cathode of the thyristor SCR is connected with the first output end; the anode of the thyristor SCR is connected with the second output end; and the gate pole of the thyristor SCR is connected with the controller so that the controller controls the conduction of the thyristor SCR.
In one embodiment, the switch VT1 and the switch VT2 are insulated gate bipolar transistors.
In one embodiment, the current meter A1, the current meter A2, and the current meter A3 are differential current sensors.
In one embodiment, the current meter a1 has a range of 0 to 300 kiloamperes; the measurement accuracy of the current meter A1 is 15 amperes; the current meter a2 and the current meter A3 range from 0 to 600 amps; the measurement accuracy of the current meter a2 and the current meter A3 was 150 milliamps.
In one embodiment, the tank circuit includes a capacitor C1 and an inductor L1 connected in series with the capacitor C1, one plate of the capacitor C1 is connected to one end of the inductor L1, the other end of the inductor L1 is the first output terminal, and the other plate of the capacitor C1 is the second output terminal; the zero zone current measuring device further comprises: and one end of the charging circuit is connected with one plate of the capacitor C1, and the other end of the charging circuit is connected with the other plate of the capacitor C1 so as to charge the capacitor C1.
The zero zone current measuring device comprises an oscillating circuit, a vacuum arc-extinguishing chamber and a measuring circuit which are connected in series. The vacuum arc extinguish chamber is used for controlling the on-off of a circuit between the oscillating circuit and the measuring circuit. The measuring circuit comprises a first measuring branch, a second measuring branch and a third measuring branch which are connected in parallel. The first measuring branch, the second measuring branch and the third measuring branch are respectively provided with a current meter. Therefore, after the zero zone current control device is conducted to form a loop, currents in different stages before and after the vacuum arc extinguish chamber is disconnected can be measured by matching the disconnection of the vacuum arc extinguish chamber and the respective conduction of different measuring branches, and the purpose of measuring the zero zone current before and after the breaker is disconnected is achieved.
A control method of a zero zone current measuring apparatus applied to the zero zone current measuring apparatus in any one of the above embodiments, comprising: obtaining a first measurement of the current meter a1 and comparing the first measurement to a first preset value; if the first measurement result is smaller than the first preset value, controlling the switch VT1 to be opened and controlling the switch VT2 to be closed; obtaining a second measurement of the current meter a2 and comparing the second measurement to a second preset value; and if the second measurement result is equal to the second preset value, controlling the vacuum arc-extinguishing chamber and the switch VT2 to be switched off.
In one embodiment, if the second measurement result is equal to the second preset value, after controlling the vacuum interrupter to be disconnected, the method further includes: a third measurement of the third current meter is obtained and a plot of current versus time is plotted based on the first measurement, the second measurement, and the third measurement.
In one embodiment, the first preset value is greater than or equal to 500 amperes and less than or equal to 600 amperes; the second preset value is 0; if the second measurement result is equal to the second preset value, after the vacuum interrupter is controlled to be disconnected, the method further comprises the following steps: and after a preset time period, controlling the SCR to be conducted.
The control method of the zero zone current measuring device is used for controlling the zero zone current measuring device, and can measure the current of the vacuum arc extinguish chamber in different stages before and after disconnection by matching with control of disconnection of the vacuum arc extinguish chamber and control of respective conduction of different measuring branches, so that the purpose of measuring the zero zone current before and after disconnection of the circuit breaker is achieved.
Drawings
Fig. 1 is a schematic circuit diagram of a zero zone current measuring device according to an embodiment of the present application.
Fig. 2 is a schematic circuit diagram of a zero zone current measuring device according to another embodiment of the present application.
Fig. 3 is a schematic circuit diagram of a zero zone current measuring device according to another embodiment of the present application.
FIG. 4 is a graph of current plotted against time in one embodiment of the present application.
Wherein, the meanings represented by the reference numerals of the figures are respectively as follows:
10. a zero zone current measuring device;
110. an oscillation circuit;
112. a first output terminal;
114. a second output terminal;
120. a measurement circuit;
122. a first measurement branch;
124. a second measurement branch;
126. a third measurement branch;
130. a vacuum arc-extinguishing chamber;
140. a charging circuit;
142. a rectifier.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
The application provides a zero zone current measuring device 10 and a control method for the zero zone current measuring device 10, which are used for measuring zero zone current generated before and after a breaker is switched on and off. The zero zone current here means: the current in the circuit is increased from a time before the circuit breaker is opened to a time after the circuit breaker is opened. It follows that the zero zone current should at least comprise the current from the time before the circuit breaker opens to the time when the circuit breaker opens, i.e. the current before zero, and the current from the time when the circuit breaker opens to the time when the circuit breaker opens, i.e. the current after arc. The direction of the current is different before and after the breaker is opened, so the current when the breaker is opened is called current zero crossing.
In the embodiments of the present application, a circuit breaker including a vacuum interrupter 130 is taken as an example to describe the zero zone current measuring device 10 and the control method thereof.
As shown in fig. 1, a zero zone current measuring device 10 includes an oscillating circuit 110, a measuring circuit 120, and a vacuum interrupter 130.
Specifically, the tank circuit 110 is used to generate an oscillating current. Tank circuit 110 may generally include a capacitor and an inductor in series. Wherein the capacitor is used for releasing and storing electric charges to generate current. The inductor can be made of a wire wound magnetic core and is used for inhibiting the current discharged by the capacitor from increasing sharply so as to form sinusoidal discharge. When the electric energy of the capacitor is discharged, the magnetic field energy stored in the inductance coil is converted into the electric energy through the coil to charge the capacitor, and the charging current cannot be increased sharply due to the effect of the inductance, so that the charging with a sine rule is formed. Thus, an oscillating current can be formed.
In this embodiment, we name the capacitor C1 and the inductor L1 as the capacitors forming the tank circuit 110. The tank circuit 110 has a first output 112 and a second output 114. The first output terminal 112 is a terminal of the inductor L1 far from the capacitor C1; the second output terminal 114 is a plate of the capacitor C1 far from the inductor L1. In fig. 1, the first output 112 and the second output 114 are identified using black nodes.
The measurement circuit 120 is connected between the first output 112 and the second output 114. In the present embodiment, the measurement circuit 120 includes a first measurement branch 122, a second measurement branch 124, and a third measurement branch 126. The first measurement branch 122, the second measurement branch 124, and the third measurement branch 126 are electrically connected in parallel with each other. The first measuring branch 122 includes a switch VT1 and a current meter a1 connected in series, so that when the switch VT1 is turned on, the current meter a1 can measure current; conversely, when the switch VT1 is open, the current meter A1 counts as 0. The second measuring branch 124 comprises a switch VT2 and a current meter a2 connected in series, so that when the switch VT2 is turned on, the current meter a2 can measure the current; conversely, when the switch VT2 is open, the current meter A2 counts as 0. The third measurement branch 126 includes a sampling resistor R1 and a current meter A3 in series. The resistance of the sampling resistor R1 should be much larger than the resistances of the switch VT1 and the switch VT2, so that when the switch VT1 or/and the switch VT2 are closed, the indication of the current meter A3 is 0, and when the switch VT1 and the switch VT2 are opened, the current of the circuit where the current meter A3 is located passes through.
The vacuum interrupter 130, i.e. the vacuum switch tube, is connected between the first output terminal 112 and the measurement circuit 120, and is used for controlling the on/off of the circuit from the first output terminal 112 to the measurement circuit 120.
More specifically, when the zero zone current measuring device 10 of the present application operates, the vacuum interrupter 130 may be controlled to be closed first, and at this time, a current loop may be formed in the zero zone current measuring device 10. At this time, the switch VT1 may be controlled to be closed, and the switch VT2 may be controlled to be opened, so that the current outputted from the first output terminal 112 flows into the first measuring branch 122 after passing through the vacuum interrupter 130, and then flows into the second output terminal 114, so that the current detector a1 measures the loop current. When the current measured by the current meter A1 is less than the maximum measuring range of the current meter A2, the switch VT1 can be controlled to be opened, and the switch VT2 can be controlled to be closed, so that the current meter A2 can measure the loop current. When the current measured by the current meter a2 is equal to 0, the VT2 can be controlled to be turned off, and at this time, the post-arc current flows through the sampling resistor R1 and the current meter A3, so that the current meter A3 measures the post-arc current. Therefore, after the zero zone current control device is conducted to form a loop, currents in different stages before and after the vacuum arc extinguish chamber 130 is disconnected can be measured by matching with the control of the disconnection of the vacuum arc extinguish chamber 130 and the control of the respective conduction of different measuring branches, so that the purpose of measuring the zero zone current before and after the breaker is disconnected is achieved.
In one embodiment, the zero zone current measurement device 10 of the present application further comprises a controller (not shown in the figures).
Specifically, the controller may be a single chip microcomputer with a preset program. The controller is connected with the current meter A1, the current meter A2, the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber 130, and is used for obtaining the measurement results of the current meter A1 and the current meter A2 and controlling the on-off of the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber 130. The specific control process of the controller will be described in the following control method, and will not be described herein again.
In one embodiment, as shown in fig. 2, the second output 114 is connected to ground GND, and the measurement circuit 120 further includes a thyristor SCR connected in parallel with the first measurement branch 122.
Specifically, the second output terminal 114 is connected to the ground GND.
The measurement circuit 120 includes a thyristor SCR. The thyristor, also known as a silicon controlled rectifier 142, includes an anode, a cathode, and a gate. When the thyristor SCR bears positive anode voltage and the gate pole has trigger current, the thyristor can be conducted. In this embodiment, the anode of the thyristor SCR may be connected to the second output 114, the cathode of the thyristor SCR may be connected to the first output 112, and the gate of the thyristor SCR may be connected to the controller. At this time, after the post-arc current measurement is finished, the controller inputs trigger current at the gate of the thyristor SCR to trigger the thyristor to be turned on, so as to protect the sampling resistor.
In one embodiment, the zero zone current measuring device 10, its switch VT1 and switch VT2 may be insulated-Gate Bipolar transistors (IGBTs). The insulated gate bipolar transistor includes a gate, a collector, and an emitter. Wherein the collectors of the switch VT1 and the switch VT2 may be connected to the first output terminal 112 through the vacuum interrupter 130; the emitters of the switch VT1 and the switch VT2 may be connected to the second output terminal 114. The gates of the switch VT1 and the switch VT2 may be connected to a controller, so that the controller controls whether the switch VT1 and the switch VT2 are turned on or off.
In this embodiment, the resistance of the sampling resistor R1 can be made 0.1 Ω by using an igbt as the switch VT1 and the switch VT 2. Since the on-state voltage drop of the igbt is only a few volts, the equivalent resistance of the igbt is only a few milliohms when passing thousands of amperes of current, which is much smaller than the resistance of the sampling resistor R1. Therefore, when the switch VT1 and/or the switch VT2 are turned on, no current flows through the third measurement branch 126 having the sampling resistor R1, thereby protecting the current meter A3.
Further, the zero zone current measuring device 10 of the present application, its current meter a1, current meter a2, and current meter A3 may be differential current sensors. The output signal of the differential current sensor, namely the rogowski coil, is the differential of the current with respect to the time, so that the input current can be really restored, and the controller can draw a current-time curve graph according to the output results of the current meter A1, the current meter A2 and the current meter A3.
In one embodiment, in view of the large current flow and the small zero zone current flow when normally flowing, current meters with a range of 0 to 300 kilo amps may be used as current meter A1, and current meters with a range of 0 to 600 amps may be used as current meters A2 and A3. The current meter a1 can measure 10 to 20 amps, among other things, with accuracy. That is, the current meter a1 may measure 10 amps, 15 amps, or 20 amps. The measurement accuracy of current meter a2 and current meter A3 may be 100 milliamps to 200 milliamps. That is, the measurement accuracy of the current meter a2 and the current meter A3 may be 100 ma, 200 ma, or 150 ma. Therefore, the zero zone current measuring device 10 not only is suitable for measuring large current during normal through current, but also is suitable for measuring the current after the arc with high precision, so that the zero zone current is accurately measured.
In one embodiment, as shown in fig. 3, tank circuit 110 includes a capacitor C1 and an inductor L1 connected in series with capacitor C1. One substrate of the capacitor C1 is connected to one end of the inductor L1. The end of the inductor L1 not connected to the capacitor C1 forms the first output 112, which is illustrated as a black node. The substrate of the capacitor C1 not connected to the inductor L1 forms the second output terminal 114, which is indicated by the black node.
The zero zone current measurement device 10 may also include a charging circuit 140.
Specifically, one end of the charging circuit 140 is connected to one plate of the capacitor C1, and the other end of the charging circuit 140 is connected to the other plate of the capacitor C1, so that the capacitor C1 can be charged.
Further, the charging circuit 140 may include an alternating current power source DC and a rectifier 142 connected in series. The alternating current power supply DC is used to output alternating current. The rectifier 142 is used to rectify the alternating current into direct current, thereby charging the capacitor C1.
The present application also provides a control method of the zero zone current measuring apparatus 10, which is applied to the zero zone current measuring apparatus 10 in any one of the above embodiments. Before the control method of the current measuring device is executed, the vacuum interrupter 130 and the switch VT1 can be in a closed state, in which the circuit is normally open. The control method of the zero zone current measuring device 10 includes:
s100, obtain a first measurement result of the current meter a1, and compare the first measurement result with a first preset value.
Specifically, the first measurement here refers to the measurement of the current meter a 1. When the vacuum interrupter 130 and the switch VT1 are closed, the current from the oscillator circuit can flow into the current meter a1, and the current meter a1 has a reading. The first preset value may be a fixed value preset in advance in the controller.
S200, if the first measurement result is smaller than the first preset value, the switch VT1 is controlled to be opened, and the switch VT2 is controlled to be closed.
An oscillating current is generated due to the tank circuit 110. The oscillating current is sinusoidal. Thus, the first measurement of current meter A1 is constantly changing. When the first measurement result is smaller than the first preset value, the switch VT1 is controlled to be opened, and the switch VT2 is controlled to be closed.
S300, a second measurement of the current meter a2 is obtained and compared to a second preset value.
The period during which the switch VT2 is closed is the pre-zero current period. When the control switch VT2 is closed, a second measurement of the current meter a2 is obtained, and the current meter a2 has an indication. The second measurement of current meter a2 is the pre-zero current. The second preset value may be a fixed value preset in advance in the controller.
S400, if the second measurement result is equal to the second preset value, controlling the vacuum interrupter 130 and the switch VT2 to be turned off.
After the vacuum interrupter 130 and the switch VT2 are opened, a post-arc current is generated. The post-arc current may flow into current meter A3 via sampling resistor R1, at which time current meter A3 takes a third measurement. The third measurement is the post-arc current. The post-arc current and the pre-zero current together constitute a zero zone current.
Further, the method for controlling the current measuring apparatus may further include, after step S400:
s500, acquiring a third measurement result of the third ammeter, and drawing a graph of the current with respect to time according to the first measurement result, the second measurement result and the third measurement result.
Specifically, the third measurement here refers to the measurement of the current meter a 3. The current meter a1, current meter a2, and current meter A3 may be differential current sensors whose output signals are the current derivative with respect to time. Thus, the first, second, and third measurements of current meter A1, Current meter A2, and Current meter A3 may be plotted as a function of current versus time.
In one embodiment, the first predetermined value is less than or equal to the maximum measurement range of the current meter a2, so that after the VT2 is turned on, the current meter a2 will not be damaged because the current is greater than the maximum measurement range of the current meter a 2. Meanwhile, the first preset value is not suitable to be much smaller than the maximum range of the current meter a2, and it is difficult to accurately measure the current before the vacuum interrupter 130 is disconnected.
In one specific embodiment, the first preset value may be greater than or equal to 500 amps and less than or equal to 600 amps when the current meter a2 has a range of 0 to 600 amps. That is, the first preset value may be 500 amperes, 600 amperes, or 550 amperes.
The second preset value may be 0 so that after the vacuum interrupter 130 is disconnected, the post-arc current is measured by the current meter A3 connected in series with the sampling resistor R1.
Further, the method for controlling the current measuring apparatus may further include, after step S500:
and S600, after a preset time period, controlling the SCR to be conducted.
The preset time period is a time period for measuring the current after the vacuum interrupter 130 is disconnected. After the vacuum interrupter 130 is opened, the post-arc current will typically return to zero in tens of microseconds to a hundred microseconds. Thus, the preset time period may be 20 microseconds, may be 100 microseconds, and may be 50 microseconds or 80 microseconds. After the preset time period, the SCR of the thyristor is controlled to be conducted, and the situation that the sampling resistor is damaged by huge current generated by the heavy breakdown of the current measuring device can be prevented. The thyristor SCR is controlled to be turned on by inputting a trigger current to the gate of the thyristor SCR.
The operation of the zero zone current measuring device 10 and the control method thereof according to the present application will be described with reference to fig. 3 and 4.
Before the zero zone current measuring device 10 is operated, the capacitor C1 is charged by the ac power source DC through the rectifier 142. After the capacitor C1 is charged, the zero zone current measuring device 10 can start to operate.
Initially, vacuum interrupter 130 and switch VT1 are closed and conductive. At this time, the zero zone current measuring device 10 normally flows. The current flows from the first output 112, through the vacuum interrupter 130, into the first measuring branch 122, and into the second output 114. At this time, current meter A1 measures the current in circuit 120 and generates a first measurement. The first measurement is communicated to the controller.
And after the controller acquires the first measurement result, comparing the first measurement result with a first preset value. The first preset value is slightly less than the maximum range of current meter a 2. When the first measurement result is equal to or less than the first preset value, the switch VT1 is controlled to be opened, and the switch VT2 is controlled to be closed and conducted. At this time, the current flows from the output terminal, flows into the second measuring branch 124 after passing through the vacuum interrupter 130, and then flows into the second output terminal 114. At this time, the current meter a2 measures the current in the circuit 120 and generates a second measurement. The second measurement is communicated to the controller. The second measurement result is the current before zero in the zero zone current to be measured.
And after the controller acquires the second measurement result, comparing the second measurement result with a second preset value. The second preset value is 0. When the second measurement result is equal to the second preset value, the vacuum interrupter 130 and the switch VT2 are controlled to be turned off. At this time, the post-arc current flows out of the second output terminal 114, into the sampling resistor R1 and the current meter A3. Current meter A3 measures the current in circuit 120 and generates a third measurement. The third measurement is communicated to the controller. The third measurement result is the post-arc current in the zero zone current to be measured.
After the controller obtains the first measurement result, the second measurement result and the third measurement result, a curve graph of the current with respect to time can be drawn according to the first measurement result, the second measurement result and the third measurement result. A plot of current versus time may be as shown in fig. 4. Wherein, the time period from t1 to t2 is a current change curve when the current is normally flowed; the time period t2 to t3 is the pre-zero current in the zero zone current; the time period t3 to t4 is the post-arc current in the zero zone current.
According to the zero zone current measuring device 10 and the control method thereof, the current measuring meters can be switched in time when the current reaches the zero zone current by using the plurality of measuring branches for measuring in a time-sharing manner, so that the zero zone current can be accurately measured.
After the post-arc current measurement is finished, the controller can input trigger current at the gate of the thyristor SCR to trigger the thyristor SCR to be conducted, so that the thyristor SCR can be used for protecting the sampling resistor R1.
The zero zone current measuring device 10 and the control method thereof can monitor the loop current of the zero zone current measuring device 10 by measuring the current by using the wide-range current meter a1 when the current is normally passed. Therefore, when the current reaches the first preset value, the current can be switched to the second measuring branch 124 in time, the current meter a2 with higher precision measures the current, and the current before zero can be monitored with high precision. After the current crosses zero, namely reaches a second preset value, the current is switched to the third measuring branch 126 in time, and the current meter A3 with higher precision measures the current, so that the post-arc current can be monitored with high precision. According to the zero zone current measuring device 10 and the control method thereof, the currents of different stages before and after the vacuum arc-extinguishing chamber 130 is disconnected can be measured by controlling the disconnection of the vacuum arc-extinguishing chamber 130 and controlling the respective conduction of different measuring branches, so that the purpose of measuring the zero zone current before and after the circuit breaker is disconnected is achieved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A zero zone current measuring device, comprising:
an oscillating circuit (110) for generating an oscillating current, the oscillating circuit (110) having a first output (112) and a second output (114);
a measurement circuit (120) connected between the first output (112) and the second output (114); the measurement circuit (120) comprises a first measurement branch (122), a second measurement branch (124) and a third measurement branch (126) connected in parallel, wherein the first measurement branch (122) comprises a switch VT1 and a current meter a1 connected in series; the second measuring branch (124) comprises a switch VT2 and a current meter A2 connected in series; the third measuring branch (126) comprises a sampling resistor R1 and a current meter A3 which are connected in series; the measurement accuracy of the current meter A2 and the current meter A3 is greater than that of the current meter A1;
a vacuum arc-extinguishing chamber (130) connected between the first output terminal (112) and the measuring circuit (120) for controlling the circuit connection and disconnection of the first output terminal (112) to the measuring circuit (120);
wherein the measuring circuit (120) is used for obtaining a first measuring result measured by the current meter A1 when the vacuum arc extinguish chamber (130) is closed, the switch VT1 is closed and the switch VT2 is opened; when the first measurement result is smaller than a first preset value, the switch VT1 is opened, and the switch VT2 is closed, the current meter A2 measures the current before zero; when the second measurement result is equal to a second preset value, the vacuum arc-extinguishing chamber 130 and the switch VT2 are controlled to be switched off, and the current after arc is measured by the current meter A3; the pre-zero current and the post-arc current constitute the zero zone current.
2. The zero zone current measuring device according to claim 1, further comprising:
and the controller is connected with the current meter A1, the current meter A2, the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber (130), and is used for acquiring the measurement results of the current meter A1 and the current meter A2 and controlling the on-off of the switch VT1, the switch VT2 and the vacuum arc-extinguishing chamber (130).
3. The zero zone current measuring device according to claim 2, characterized in that the second output (114) is connected to ground GND;
the measurement circuit (120) further comprises a thyristor SCR connected in parallel with the first measurement branch (122), the cathode of the thyristor SCR being connected to the first output (112); the anode of the thyristor SCR is connected with the second output end (114); and the gate pole of the thyristor SCR is connected with the controller so that the controller controls the conduction of the thyristor SCR.
4. The zero region current measuring device of claim 1, wherein the switch VT1 and the switch VT2 are insulated gate bipolar transistors.
5. The zero zone current measuring device of claim 1 or 4, wherein the current meter A1, the current meter A2, and the current meter A3 are differential current sensors.
6. The zero zone current measuring device of claim 5, wherein said current meter A1 has a range of 0 to 300 kiloamperes; the measurement accuracy of the current meter A1 is 15 amperes;
the current meter a2 and the current meter A3 range from 0 to 600 amps; the measurement accuracy of the current meter a2 and the current meter A3 was 150 milliamps.
7. The zero zone current measuring device according to claim 1, wherein the oscillating circuit (110) comprises a capacitor C1 and an inductor L1 connected in series with the capacitor C1, one plate of the capacitor C1 is connected to one end of the inductor L1, the other end of the inductor L1 is the first output terminal (112), and the other plate of the capacitor C1 is the second output terminal (114);
the zero zone current measuring device (10) further comprises:
a charging circuit (140), one end of the charging circuit (140) is connected to one plate of the capacitor C1, and the other end of the charging circuit (140) is connected to the other plate of the capacitor C1 to charge the capacitor C1.
8. A control method of a zero zone current measuring apparatus applied to the zero zone current measuring apparatus (10) according to any one of claims 1 to 7, characterized by comprising:
obtaining a first measurement of the current meter a1 and comparing the first measurement to a first preset value;
if the first measurement result is smaller than the first preset value, controlling the switch VT1 to be opened and controlling the switch VT2 to be closed;
obtaining a second measurement of the current meter a2 and comparing the second measurement to a second preset value;
and if the second measurement result is equal to a second preset value, controlling the vacuum arc-extinguishing chamber (130) and the switch VT2 to be disconnected.
9. The control method of the zero zone current measuring device according to claim 8, wherein if the second measurement result is equal to a second preset value, after controlling the vacuum interrupter (130) to open, the method further comprises:
a third measurement of the current meter a3 is taken and a graph of current versus time is plotted based on the first, second, and third measurements.
10. The control method of the zero zone current measuring device according to claim 9, wherein the first preset value is 500 amperes or more and 600 amperes or less; the second preset value is 0;
if the second measurement result is equal to the second preset value, after the vacuum interrupter (130) is controlled to be disconnected, the method further includes:
and after a preset time period, controlling the SCR to be conducted.
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