CN202815139U - Digital insulation monitoring sensor - Google Patents
Digital insulation monitoring sensor Download PDFInfo
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- CN202815139U CN202815139U CN 201220460319 CN201220460319U CN202815139U CN 202815139 U CN202815139 U CN 202815139U CN 201220460319 CN201220460319 CN 201220460319 CN 201220460319 U CN201220460319 U CN 201220460319U CN 202815139 U CN202815139 U CN 202815139U
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- electric capacity
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Abstract
The utility model discloses a digital insulation monitoring sensor, comprising an exciting unit and a measurement and control unit; wherein the exciting unit is used for enabling an exciting voltage source to periodically charge a capacitor forwardly or reversely through an inductance coil according to a charging indication emitted by the measurement and control unit; the measurement and control unit is used for emitting the charging indication to the exciting unit according to a set switching frequency, respectively obtaining first voltage rise time and second voltage rise time of the capacitor when the exciting voltage source charges the capacitor forwardly or reversely through the inductance coil, and calculating the size of a leakage current according to a difference between the first voltage rise time and the second voltage rise time. The digital insulation monitoring sensor of the utility model has the beneficial effects that: the technical scheme only adopts one voltage source, thereby simplifying a system structure, and reducing cost; by adopting the technical means of successively performing forward or reverse excitation, zero stability and linearity of a test result can be better, and a stronger anti-interference performance is achieved.
Description
Technical field
The utility model relates to sensor technical field, is specifically related to a kind of digital insulating monitoring sensor.
Background technology
The earth leakage stream that insulation monitoring and warning device is used for transformer station, current system in hydropower station bus and feeder line screen detects, and is the important core parts of realizing Design of DC System Grounding Fault Detection and localization of fault.For the insulating monitoring sensor of straight-flow system, magnetic modulation type, Voltage-output type, current-output type and PWM output type leakage current transformer are arranged in the market.
Wherein, Voltage-output type leakage current transformer needs negative and positive dual power power supply, poor anti jamming capability.Although the antijamming capability of current-output type leakage current transformer is slightly strong, also need the negative and positive dual power power supply, and power consumption is relatively large, cost is relatively high.In addition, the portioned product in above-mentioned two kinds of leakage current transformers is owing to having adopted amplifier to cause zero point drift, and the long-time stability that reach zero point are relatively poor.Pulse-length modulation (Pulse Width Modulation, PWM) output type leakage current sensor, use amplifier to form self-excited oscillator, also need dual power supply, and the sensor zero point drift is restive, signal output is affected by the distributed capacitance of cabling wiring easily, and consistance is relatively poor, is difficult to realize the good linearity of full scale.
To sum up, existing above-mentioned several leakage current sensor need to adopt the negative and positive dual power power supply, and cost is higher, and interference free performance is strong not, and the zero stability of monitoring result is poor, and the linearity is good not.
The utility model content
The utility model embodiment provides a kind of digital insulating monitoring sensor, and higher to solve existing leakage current sensor cost, interference free performance is strong not, the poor and imperfect technical matters of the linearity of the zero stability of monitoring result.
A kind of digital insulating monitoring sensor comprises: exciting unit and measurement and control unit;
Described exciting unit, comprise the excitation voltage source of series connection and electric capacity and be serially connected in telefault between described excitation voltage source and the electric capacity by the excitation change-over switch, described excitation change-over switch is connected with described measurement and control unit, the charging that described excitation change-over switch is used for sending according to measurement and control unit is indicated, the periodic access direction that changes described telefault is so that excitation voltage source is periodically charged to electric capacity by telefault forward or backwards;
Described measurement and control unit, be used for sending the charging indication according to the switching frequency of setting to described exciting unit, obtain the first voltage rising time and the second voltage rise time of described electric capacity, according to the size of described the first voltage rising time and the difference of second voltage rise time calculating leakage current;
Wherein, when described the first voltage rising time refers to that the excitation voltage source forward charges to electric capacity by telefault, the voltage rising time of described electric capacity; The described second voltage rise time is when referring to that excitation voltage source is oppositely charged to electric capacity by telefault, the voltage rising time of described electric capacity.
The digital insulating monitoring sensor that the utility model embodiment provides only adopts a voltage source, has simplified system architecture, has reduced cost; By adopting the technological means that encourages forward or backwards successively, make the zero stability of test result and the linearity better, interference free performance is stronger.
Description of drawings
Fig. 1 is the structural representation of the digital insulating monitoring sensor that provides of the utility model embodiment;
Fig. 2 is an emulation synoptic diagram among the utility model embodiment;
Fig. 3 is the synoptic diagram of a work wave mode among the utility model embodiment;
Fig. 4 is the schematic diagram of the current-loop communication circuit of the utility model embodiment.
Embodiment
The utility model embodiment provides a kind of digital insulating monitoring sensor, and it is high to solve existing leakage current sensor cost, and interference free performance is strong not, the imperfect technical matters of the zero stability of monitoring result and the linearity.Below be elaborated.
Embodiment one,
Please refer to Fig. 1, the utility model embodiment provides a kind of digital insulating monitoring sensor, comprises exciting unit and measurement and control unit.Described exciting unit, the charging that is used for sending according to measurement and control unit is indicated, and excitation voltage source is periodically charged to electric capacity by telefault forward or backwards.Described measurement and control unit, be used for sending the charging indication according to the switching frequency of setting to exciting unit, obtain the first voltage rising time and the second voltage rise time of described electric capacity, according to the size of described the first voltage rising time and the difference of second voltage rise time calculating leakage current.When described the first voltage rising time refers to that the excitation voltage source forward charges to electric capacity by telefault, the voltage rising time of described electric capacity; The described second voltage rise time is when referring to that excitation voltage source is oppositely charged to electric capacity by telefault, the voltage rising time of described electric capacity.
Optionally, described exciting unit comprises the excitation voltage source 6 of series connection and electric capacity 8 and is serially connected in telefault 1 between described excitation voltage source 6 and the electric capacity 8 by excitation change-over switch 2,3,4,5.Described excitation change-over switch 2,3,4,5 is connected with described measurement and control unit, is used for the charging indication according to measurement and control unit, periodically changes the access direction of described telefault 1.
Optionally, described excitation change-over switch comprises two positive incentive change-over switches 2,3 and two reverse energization change-over switches 4,5, wherein, described two positive incentive change-over switches 2,3 are used for described telefault 1 forward is serially connected between described excitation voltage source 6 and the electric capacity 8, and described two reverse energization change-over switches 4,5 are used for described telefault 1 oppositely is serially connected between described excitation voltage source 6 and the electric capacity 8.
Optionally, described measurement and control unit comprises: analog comparator 9, reference source 7, microprocessor 10, current loop communication circuit 11 and connection terminal 17; The positive input of described analog comparator 9 links to each other with the positive pole of described electric capacity 8, reverse input end links to each other with described reference source 7, output terminal links to each other with the outside input end 18 that catches of the timer of described microprocessor, described analog comparator 9 is used for obtaining and the voltage of more described electric capacity 8 and the voltage of described reference source 7, and gives described microprocessor 10 according to comparative result output trigger pip; Described microprocessor 10 and described excitation change-over switch, current loop communication circuit 11 and connection terminal 17 connect, be used for according to described trigger pip, generate and send the charging indication to described excitation change-over switch, and the first voltage rising time and the second voltage rise time of obtaining described electric capacity 8, calculate the size of leakage current according to described the first voltage rising time and the difference of second voltage rise time, are connected the checkout equipment that is connected with the outside with connection terminal by described current loop communication circuit 11 and communicate by letter.
Further, described excitation change-over switch can adopt electronic switch or multiplexer.
Further, the telefault in the described exciting unit, the second-order circuit that electric capacity and excitation change-over switch form is operated in overdamping state.
Further, the excitation frequency when described excitation voltage source is charged to electric capacity by telefault forward or backwards equates that phase differential is fixed.
Optionally, described microprocessor also can be used for adopting the state that voltage system detects feeder switch that detects.
To sum up, the utility model embodiment provides a kind of digital insulating monitoring sensor, and by only adopting a voltage source, it is simple to have system architecture, the advantage that cost is low; By adopting the technological means encourage forward or backwards successively, so that the more traditional same type of sensor of the zero stability of test result and the linearity has is better, and interference free performance is stronger.
Embodiment two,
In the present embodiment, the telefault in the described exciting unit adopts the permalloy ironcore choke, and the microprocessor in the described measurement and control unit adopts embedded microprocessor.So, the digital insulating monitoring sensor that present embodiment provides, comprise permalloy ironcore choke 1, positive incentive change-over switch 2,3, reverse energization change-over switch 4,5, excitation voltage source 6, charging capacitor 8, reference source 7, analog comparator 9, embedded microprocessor 10, current-loop communication circuit 11 and connection terminal 17.Annexation is as shown in Figure 1:
In the exciting unit: the positive pole of alloy core coil 1 does not link to each other with an end of positive incentive change-over switch 2 and reverse energization change-over switch 5 respectively, the negative pole of alloy core coil 1 does not link to each other with an end of positive incentive change-over switch 3 and reverse energization change-over switch 4 respectively, the other end of positive incentive change-over switch 2 and reverse energization change-over switch 4 links to each other with the positive pole of excitation voltage source 6, the other end of positive incentive change-over switch 3 and reverse energization change-over switch 5 links to each other with the positive pole of electric capacity 6, the minus earth of the negative pole of excitation voltage source 6 and electric capacity 6; Optionally, a resistance in parallel between the positive pole of electric capacity and the negative pole again.The alloy core coil 1, positive incentive change-over switch 2,3 or reverse energization change-over switch 4,5 and electric capacity 6 form the Second-Order RLC Filter Circuit series circuits.
In the measurement and control unit: the positive input of analog comparator 9 links to each other with the positive pole of electric capacity 8, the reverse input end of analog comparator 9 links to each other with the positive pole of reference source 7, the minus earth of reference source 7, the output terminal of analog comparator 9 links to each other with the outside input end 18 that catches of the timer of embedded microprocessor 10; Embedded microprocessor 10 also with excitation change-over switch 2,3,4,5, the pin 12 of current-loop communication circuit 11 and connection terminal 17 links to each other, the pin 15 of connection terminal 17,16 links to each other with external power source, is that digital insulating monitoring sensor is powered; The pin 14 of connection terminal 17,15 is connected with current-loop communication circuit 11 on one side, with external unit be connected on one side, by cheap electric current loop communication modes, realize receiving and sending data.
During normal operation, the periodic switching positive incentive change-over switch 2,3 of microprocessor (MCU) and reverse energization change-over switch 4,5, thus excitation voltage source is periodically charged by 1 pair of electric capacity 8 of telefault forward or backwards; Namely, MCU in a charge cycle with positive incentive change-over switch 2,3 closures, reverse energization change-over switch 4,5 is disconnected, excitation voltage source 6 forwards charge by 1 pair of electric capacity 8 of telefault, at this moment the flow direction responded in iron core of the flow direction responded in iron core of exciting current and leakage current is consistent, is referred to as positive incentive; In the adjacent charge cycle of the next one, MCU disconnects positive incentive change-over switch 2,3, with reverse energization change-over switch 4,5 closures, excitation voltage source 6 is oppositely charged by 1 pair of electric capacity 8 of telefault, at this moment the flow direction responded in iron core of the flow direction responded in iron core of exciting current and leakage current is opposite, is referred to as reverse energization.
By in MCU, setting suitable switching frequency, periodically control forward and reverse excitation change-over switch, can make the interior voltage U c to electric capacity 8 of each Energizing cycle is the zero state response of a second-order circuit; The differential equation of its simplification is:
————（1）
When the rlc circuit of exciting unit was operated in overdamping state, the time domain response of electric capacity 8 was:
Known by formula (3), the time domain response of electric capacity 8 and not the inductance L of alloy core coil direct relation is arranged, that is, the rise time of the voltage U c at electric capacity two ends is linear ratio relation with inductance L certain in interval during capacitor charging, L is larger, and the then rise time is larger, otherwise less.Shown in Figure 2 such as simulation result.
The computing formula of toroidal inductor is:
L=μ0·μr·Ae·N^2 / le ————（4）
Wherein, μ 0 is permeability of vacuum, and μ r is relative permeability, and le is effective magnetic circuit length, and Ae is the magnetic core sectional area.
The magnetic permeability formula is: μ r=B/H------(5)
Wherein, B is magnetic induction density, and H is magnetic field intensity.
The pass of magnetic flux and magnetic induction density is: B=Φ/S------(6)
Wherein, Φ is magnetic flux, and S is sectional area.
The inductance value of toroidal inductor and the magnetic flux of magnetic core have direct proportionate relationship as can be known by formula (4) (5) (6).
Again by Ampère circuital theorem:
-----------(7)
Can draw the inductance value L=K(Φ I of toroidal inductor ± Φ II)------(8)
Wherein, Φ I is the magnetic flux that exciting current is responded in magnetic core, and Φ II is the magnetic flux that leakage current I responds in magnetic core
In like manner can draw the charging voltage rise time t=J(Φ I of electric capacity 8 ± Φ II), namely the rise time is linearly proportional with (Φ I ± Φ II).
By formula (7), Φ II=U*I, namely Φ II and leakage current are directly proportional.
By above-mentioned inference as can be known, during positive incentive when the charging voltage rise time t+ of electric capacity 8 and reverse energization difference and the leakage current of the rise time t-of capacitor charging voltage linearly proportional, and (t+)-(t-)=n*I; I is leakage current.
Based on above-mentioned derivation, as long as periodic switching forward, reverse energization, with adjacent twice when excitation electric capacity 8 the charging voltage rise time carry out accurate timing, the charging voltage rise time in the time of just can be according to twice that obtains adjacent the excitation calculates the size of leakage current I.
The work wave of present embodiment numeral insulating monitoring sensor as shown in Figure 3.Positive incentive waveform 21, reverse energization waveform 22 be with identical frequency, fixing phase differential switching, and purpose is to be once zero state response in order to encourage electric capacity 8 at every turn.The Charge-discharge wave shape of electric capacity 8 is shown in 23, and straight line 24 is magnitudes of voltage of the reference voltage source 7 that connects of the reverse input end of comparer 9.Waveform 25 is the output of comparer 9, " T1+ " in the waveform 25, " T2+ " ... that reverse energization finishes the duration that behind the positive incentive voltage of electric capacity 8 rises to comparer reverse input end reference voltage; And " T1-", " T2-" ... that positive incentive finishes the duration that behind the reverse energization voltage of electric capacity 8 rises to comparer reverse input end reference voltage.Because positive incentive finishes to finish to equate to the duration that positive incentive begins with reverse energization to the duration that reverse energization begins, so the rise time difference of electric capacity 8 voltage when forward and reverse excitation is:
（Ti+）-（Ti-）=（）
Thereby, leakage current I=m*(Σ (Ti+-Ti-))/n, wherein i=1-n.
In sum, present embodiment numeral insulating monitoring sensor adopts the technological means that encourages forward or backwards successively, can be so that the more traditional same type of sensor of the zero stability of test result and the linearity has better effect.In addition, if simultaneously by adopting high magnetic permeability, magnetic core that remanent magnetism is few, then the zero stability of test result and the linearity can be better.
In above-described embodiment, microprocessor 10 can adopt a new generation's 32 8-digit microcontrollers with very high cost performance, this kind microcontroller is supported high primary frequency 25Mhz, can utilize analog comparator in the sheet and 32 bit timing devices to realize high precision collecting to leakage current.Forward and reverse excitation change-over switch can adopt cheaply four-way analog switch.Current-loop communication circuit can adopt solution as shown in Figure 4.During the utility model numeral insulating monitoring normal operation of sensor, forward and reverse excitation frequency is 10 ~ 50Hz, and the frequency that discharges and recharges of electric capacity is 20 ~ 100Hz.Use MCU timer 0 as pulser timer, be operated in outside catching mode, use the seizure that analog comparator 0 was exported as forward and reverse actuation duration in the sheet, namely the output terminal of analog comparator 0 links to each other with the outside seizure pin of T0.Electric capacity discharges immediately when reverse energization finishes, and the outside of setting before this T0 captures as negative edge and interrupts, and realizes that reverse energization begins timing when finishing, and the seizure of the outside of T0 is set as the rising edge interruption; When positive incentive begins and electric capacity is charged when making capacitance voltage rise to comparer reverse input end reference voltage, the comparer output switching activity is high level, trigger immediately T0 and catch current timer count value, deposit among the positive incentive time variable T+, simultaneously, the seizure interrupt routine is set as negative edge seizure interruption with the outside seizure of T0.After the seizure of finishing the positive incentive time, in the end positive incentive cycle, the comparer output switching activity is that 0 triggering T0 interrupts, and starts the timing of reverse energization time, and the seizure of the outside of T0 is set as the rising edge triggering.When reverse energization begins and electric capacity is charged when making capacitance voltage rise to comparer reverse input end reference voltage, the comparer output switching activity is high level, trigger immediately T0 and catch current timer count value, deposit among the reverse energization time variable T-, simultaneously, the seizure interrupt routine is set as the negative edge seizure with the outside seizure of T0.Repeat said process.Program with the difference of the T+ that obtains and T-as a sampled value.
Can average value filtering to above-mentioned sampled value, for example, sampled value added up to be averaged for 256 times again, has obtained more accurate result.Because the present embodiment technical scheme has the good linearity, can adopt 2 point calibration algorithms to obtain more accurate sample mean.
Two point calibration algorithms are respectively got any as check point at positive and negative terminal, carry out as follows:
Y1=A(X1+B)
Y2=A(X2+B)
Correction coefficient A, B are by drawing top formula simultaneous solution.
One of ordinary skill in the art will appreciate that all or part of step in the whole bag of tricks of above-described embodiment can finish by hardware, also can finish by the relevant hardware of programmed instruction, this program can be stored in the computer-readable recording medium, and storage medium can comprise: ROM (read-only memory), random-access memory, disk or CD etc.
More than digital insulating monitoring sensor that the utility model embodiment is provided and the method for test leakage current be described in detail, but the explanation of above embodiment just is used for helping to understand method of the present utility model and core concept thereof, should not be construed as restriction of the present utility model.Those skilled in the art are in the technical scope that the utility model discloses, and the variation that can expect easily or replacement all should be encompassed within the protection domain of the present utility model.
Claims (6)
1. a digital insulating monitoring sensor is characterized in that, comprising: exciting unit and measurement and control unit;
Described exciting unit, comprise the excitation voltage source of series connection and electric capacity and be serially connected in telefault between described excitation voltage source and the electric capacity by the excitation change-over switch, described excitation change-over switch is connected with described measurement and control unit, the charging that described excitation change-over switch is used for sending according to measurement and control unit is indicated, the periodic access direction that changes described telefault is so that excitation voltage source is periodically charged to electric capacity by telefault forward or backwards;
Described measurement and control unit, be used for sending the charging indication according to the switching frequency of setting to described exciting unit, obtain the first voltage rising time and the second voltage rise time of described electric capacity, according to the size of described the first voltage rising time and the difference of second voltage rise time calculating leakage current;
Wherein, when described the first voltage rising time refers to that the excitation voltage source forward charges to electric capacity by telefault, the voltage rising time of described electric capacity; The described second voltage rise time is when referring to that excitation voltage source is oppositely charged to electric capacity by telefault, the voltage rising time of described electric capacity.
2. digital insulating monitoring sensor according to claim 1 is characterized in that:
Described excitation change-over switch comprises two positive incentive change-over switches and two reverse energization change-over switches, wherein, described two positive incentive change-over switches are used for described telefault forward is serially connected between described excitation voltage source and the electric capacity, and described two reverse energization change-over switches are used for described telefault oppositely is serially connected between described excitation voltage source and the electric capacity.
3. digital insulating monitoring sensor according to claim 1 is characterized in that described measurement and control unit comprises: analog comparator, reference source, microprocessor, current loop communication circuit and connection terminal;
The positive input of described analog comparator links to each other with the positive pole of described electric capacity, reverse input end links to each other with described reference source, output terminal links to each other with the outside input end that catches of the timer of described microprocessor, described analog comparator is used for obtaining and the voltage of more described electric capacity and the voltage of described reference source, and gives described microprocessor according to comparative result output trigger pip;
Described microprocessor and described excitation change-over switch, current loop communication circuit and connection terminal connect, be used for according to described trigger pip, generate and send the charging indication to described excitation change-over switch, and the first voltage rising time and the second voltage rise time of obtaining described electric capacity, according to the size of described the first voltage rising time and the difference of second voltage rise time calculating leakage current, communicate by letter with the outside checkout equipment that is connected with connection terminal by described current loop communication circuit.
4. it is characterized in that according to claim 2 or 3 described digital insulating monitoring sensors:
Described excitation change-over switch adopts electronic switch or multiplexer.
5. it is characterized in that according to claim 2 or 3 described digital insulating monitoring sensors:
Telefault in the described exciting unit, the second-order circuit that electric capacity and excitation change-over switch form is operated in overdamping state.
6. it is characterized in that according to claim 2 or 3 described digital insulating monitoring sensors:
Excitation frequency when described excitation voltage source is charged to electric capacity by telefault forward or backwards equates that phase differential is fixed.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201220460319 CN202815139U (en) | 2012-09-11 | 2012-09-11 | Digital insulation monitoring sensor |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201220460319 CN202815139U (en) | 2012-09-11 | 2012-09-11 | Digital insulation monitoring sensor |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102788930A (en) * | 2012-09-11 | 2012-11-21 | 深圳市金宏威技术股份有限公司 | Digital insulation monitoring sensor and method for testing leakage current |
| CN104155507A (en) * | 2014-08-20 | 2014-11-19 | 上海正泰电源系统有限公司 | Leakage current detection circuit and method |
| CN104914289A (en) * | 2015-06-16 | 2015-09-16 | 国家电网公司 | Device for measuring direct current and method |
| CN111585244A (en) * | 2020-05-26 | 2020-08-25 | 芯海科技（深圳）股份有限公司 | Leakage protection circuit, integrated circuit, electronic device, and method |
-
2012
- 2012-09-11 CN CN 201220460319 patent/CN202815139U/en not_active Withdrawn - After Issue
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102788930A (en) * | 2012-09-11 | 2012-11-21 | 深圳市金宏威技术股份有限公司 | Digital insulation monitoring sensor and method for testing leakage current |
| CN102788930B (en) * | 2012-09-11 | 2014-08-06 | 深圳市金宏威技术股份有限公司 | Digital insulation monitoring sensor and method for testing leakage current |
| CN104155507A (en) * | 2014-08-20 | 2014-11-19 | 上海正泰电源系统有限公司 | Leakage current detection circuit and method |
| CN104914289A (en) * | 2015-06-16 | 2015-09-16 | 国家电网公司 | Device for measuring direct current and method |
| CN104914289B (en) * | 2015-06-16 | 2017-03-08 | 国家电网公司 | A kind of method of measurement DC current |
| CN111585244A (en) * | 2020-05-26 | 2020-08-25 | 芯海科技（深圳）股份有限公司 | Leakage protection circuit, integrated circuit, electronic device, and method |
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