CN101499650A - Small current earthing wire selection protection apparatus and protection method based on GPRS - Google Patents

Abstract

The invention relates to a GPRS-based protection device of small-current grounding line selection and a protection method thereof. The protection method adopts zero-sequence compensation admittance line selection method. One device realizes the protection of the small-current grounding line selection under NUS and NES connection mode in a compatible way, thereby broadening the scope of application. Simultaneously, the protection device provides a switch output signal to the outside, and the GPRS wireless network is used for wireless communication. In the method, the judgment conditions for failure judgment under the condition of the NUS connection mode are increased; the errors are greatly reduced; the line selection accuracy is further improved; the misjudgment rate of the device is reduced and is lower than 1 percent under the ideal conditions; the misjudgment rate in the site test can be maintained within 5 percent; the device has the advantages of high reliability and long transmission distance; and the utilization of the GPRS module can reduce the construction cost, accelerate the access to the network and provide reliable communication.

Description

Small current earthing wire-selecting protective device and guard method based on GPRS

Technical field

The invention belongs to the electric power transfer field, be applied to the isolated neutral electrical network, be a kind of small current earthing wire-selecting protective device and guard method based on GPRS.

Background technology

At neutral nondirect earthing network, when claiming again in the small grounding current system single-phase earthing to take place, because the electric current of fault point is very little, and the line voltage between the three-phase still keeps symmetry, to not influence of load power supply, therefore, in the ordinary course of things, all allow to continue again to move 1～2 hour, and needn't trip immediately.But after single-phase earthing, the voltage to earth of other two-phases raises

Doubly, further be expanded into or multipoint earthing short circuit at 2 in order to prevent fault, the operations staff should in time take measures to be eliminated.

The isolated neutral electrical network is that neutral nondirect earthing network is a kind of.When distribution network generation low current grounding, can't predict and take the effective precautionary measures in advance, only can adopt open line method and artificial line walking ocular estimate to determine the accurate position of earth point afterwards, open line method need carry out a large amount of grid switching operations, bring very big loss to production, especially at the Production Regional of working continuously and some key equipments; And after accident takes place, take artificial line walking ocular estimate to seek earth point, all to expend great amount of manpower and material resources and time at every turn.Some technical staff have made a large amount of development work to this at present, and a kind of protective device of developing is to adopt colony than amplitude ratio phase method, but is subjected to the influence of zero sequence current mutual inductor unsymmetrical current, operational mode, differentiates unstable.

Summary of the invention

The problem to be solved in the present invention is: do not have suitable protective device in the isolated neutral electrical network at present; Breakdown Maintenance expends great amount of manpower and material resources and time; existing protective device is differentiated unstable, needs a kind of stabilizing effective small current earthing wire-selecting protective device and guard method.

Technical scheme of the present invention is: based on the small current earthing wire-selecting protective device of GPRS; comprise power module; electric quantity signal collecting module; display module; the switching value output module; one-chip computer module; communication module and GPRS module; power module; the output of electric quantity signal collecting module connects one-chip computer module; display module; the switching value output module is connected with the one-chip computer module two-wire with communication module; communication module is connected by RS232 with the GPRS module; electric quantity signal collecting module is by electric current; voltage transformer; operational amplifier and filter circuit are formed; filter circuit is a second order voltage controlled voltage source low-frequency filter circuit; one-chip computer module comprises the C8051F206 chip; corresponding crystal oscillating circuit and reset circuit; display module is made up of the LED display lamp; the switching value output module is by relay; drive triode and protective circuit and form, communication module is made up of RS232 level transferring chip and protective circuit.

In order to prevent that the interference on the communication line from entering controller, communicating circuit will with the single chip circuit electrical isolation.

The power module of protective device of the present invention is obtained the electric current of the Current Transformer Secondary side of electric quantity signal collecting module by the current/voltage converter; suppress circuit through common mode and differential mode; current rectifying and wave filtering circuit; integrated voltage stabilizing chip; decide the single output of the non-voltage stabilizing of the high isolation of voltage input and obtain required voltage; be specially: the electric current of the Current Transformer Secondary side of electric quantity signal collecting module is through common mode and differential mode suppresses circuit and current rectifying and wave filtering circuit inserts integrated voltage stabilizing chip 7805 and SPX1117M3_3.3; export the voltage of 5V and 3.3V respectively; guarantee the stable of output by decoupling capacitor and shunt capacitance; wherein the 5V power supply singly is output as the insulating power supply that communication module provides 5V through deciding the non-voltage stabilizing of the high isolation of voltage input, and 3.3V provides power supply for single-chip microcomputer C8051F206.

The present invention is based on the small current earthing wire-selecting guard method of GPRS, adopt the zero sequence compensation admittance method, under the single-phase earthing stable state, gather residual voltage, zero-sequence current, because residual voltage is U behind the single-phase earthing ₀∈ (30V 100V), starts the route selection program when monitoring after residual voltage surpasses 30V, and its discriminating step is as follows:

(1) initialization;

(2) the definite mode of connection that need carry out fault judgement is isolated neutral NUS or neutral by arc extinction coil grounding NES;

(3) if NUS under the single-phase earthing stable state, calculates the sinusoidal coefficient u of zero-sequence fundamental voltage _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1c, judge whether i _1su _1s+ i _1cu _1c＜0, i _1cu _1s-i _1su _1c＜0, if satisfy simultaneously, earth fault has then taken place, change step (6) over to, otherwise change step (7) over to;

(4), judge compensation admittance fiducial value Y if NES calculates the compensation admittance _Per, if satisfy | Y _Per|＜1.5% earth fault has taken place, and changes step (6) over to, otherwise judges whether | Y _Per| 20%, earth fault has then taken place if satisfy, change step (6) over to, if all do not satisfy | Y _Per|＜1.5% He | Y _Per| 20%, change step (5) over to;

(5) judge compensation admittance angle θ, if satisfy 180 °-θ, 1＜θ＜180 °+θ ₂, earth fault has then taken place, change step (6) over to, otherwise change step (7), wherein θ over to ₁Be overcompensation trip boundary angle, θ ₂Be undercompensation trip boundary angle;

(6) counter adds 1, and whether counter reports to the police if satisfy greater than setting threshold, calls the communication subprogram simultaneously; Otherwise change step (2) over to;

(7) return step (1);

The described setting threshold of step (6) is judged number of times for carrying out earth fault.

The communication subprogram of calling in the step (7) comprises following steps:

(1) the GPRS messaging format is provided with, initiation parameter;

(2) send the instruction that connects;

(3) judge whether the GPRS module connects, change step (4) over to if connected, otherwise change step (2) over to;

(4) send SMS message;

(5) judge whether short message sends success,, change step (6) over to, otherwise change step (4) over to if send successfully;

(6) return.

Can start interrupt service routine when in service automatically as interrupting, it interrupts package of service program draws together following steps:

(1) SWCINT interrupt requests;

(2), otherwise change step (5) over to if satisfy from GPRS module reception data;

(3) judged whether short message, extracted message if satisfy, otherwise change step (5) over to;

(4) judge whether separating brake according to short message, carry out separating brake if satisfy, otherwise change step (5) over to;

(5) interrupt returning.

The present invention adopts single-chip microcomputer C8051F206 as control chip, by voltage, current transformer, utilizes A/D converter collection residual voltage, zero-sequence current in the sheet, is handled by single-chip microcomputer, adopts zero sequence compensation admittance selection method.Protective device externally provides a switch output signal simultaneously, uses the RS232 PORT COM to be connected with GPRS note cat, utilizes the GPRS wireless network, realizes wireless telecommunications.

When single phase ground fault takes place when, the phase relation of residual voltage and zero-sequence current changes, and converts the voltage signal that single-chip microcomputer can be gathered through residual voltage, zero-sequence current after once changing to through the conversion of voltage transformer summation current transformer and the conditioning of operational amplifier.After single-chip microcomputer converts analog quantity to digital quantity, carry out calculation process fault is carried out the route selection judgement, dependent failure information is delivered to light-emitting diode display and switching value output circuit through the I/O port respectively.The input of dependent failure information input switch amount output circuit, promptly drive the base stage of triode, amplify the rear drive actuating of relay, produce the switching value signal through driving triode, this switching value signal can be imported the corresponding port of circuit breaker, and circuit breaker is controlled.Fault message also can be given GPRS note cat module by RS232 serial communication interface photos and sending messages, sends note is informed earth fault to the night shift room staff generation with wireless.

Also there were some to use the paper of zero sequence compensation node-pair method in the past; but all only analyzed the fault judgement of neutral by arc extinction coil grounding NES; the present invention has increased the method for differentiating isolated neutral NUS on the basis of zero sequence compensation node-pair method; and both are combined; can realize fault line detection by a covering device to two kinds of systems, more extensive on the scope of application.

The operation equation of zero sequence admittance selection method of the present invention need calculate the sinusoidal coefficient u of zero-sequence fundamental voltage _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1c, all be the generation of judging earth fault by residual voltage to NUS in the past, by zero-sequence current is carried out Fourier transform, extract fundametal compoment then, judge earth fault.But when breaking down, also contain attenuating dc component in the fault-signal owing to electric power system.Because attenuating dc component is typical nonperiodic signal, corresponding frequency spectrum is a continuous spectrum, thus with signal in the spectral aliasing of fundamental frequency, second harmonic component, can cause very big error during calculating, the error of calculation surpasses 10% under the serious situation.The inventive method is on the basis of fourier algorithm, considered the influence of attenuating dc component, simultaneously residual voltage and zero-sequence current are carried out Fourier transform, utilize the coefficient of voltage, two fundametal compoments of electric current to constitute discriminant, by the sinusoidal coefficient u of zero-sequence fundamental voltage _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1cJudge, can significantly reduce error like this, original fault distinguishing condition has only one: the zero-sequence current fundametal compoment, in case zero-sequence current is interfered, error will appear to failure judgment, the present invention now is by the characteristic of zero sequence admittance, two discriminants being utilized residual voltage and zero-sequence current fundametal compoment to judge simultaneously, the criterion refinement, error reduces significantly, has further improved the accuracy of route selection, make the False Rate of device reduce,, False Rate is lower than 1% under the perfect condition, and field test test False Rate also can remain in 5%.

In addition, one-chip computer module handle to need is first-harmonic and second harmonic signal in electric current, the voltage.Therefore, should adopt filter circuit to filter the harmonic wave more than three times in the signal.In filter circuit, passive filter circuit is simple, but is subjected to load effect bigger; The maximum attenuation slope of first-order filtering circuit has only-20dB/ ten frequencys multiplication in the active filter circuit, and the second-order circuit frequency of fadings raises and is-40dB/ ten frequencys multiplication, but bigger with desirable low frequency filtering characteristic difference.Apparatus of the present invention adopt second order voltage controlled voltage source low-frequency filter circuit, and it has-the maximum attenuation frequency of 40dB/ ten frequencys multiplication, and also in the unwanted signal of decaying to greatest extent, the influence that makes useful signal be subjected to is less.

The power supply that provides of independent power supply was provided the power supply of protective device in the past; out of doors under the environment; can not well utilize; range of application is narrow; there is certain limitation; device of the present invention mainly is used on the outdoor aerial circuit; there is not independent power supply power supply; simultaneously; it is used together with vacuum circuit-breaker again; therefore, the secondary current of the current transformer in the vacuum circuit-breaker is converted to the power supply that is suitable for this controller through the converter minitype CT, has solved the defective that device in the past can not be applied in outdoor environment.Because state be can not determine when this device powered on, and will cause the device cisco unity malfunction,, need a reset signal that one-chip computer module is initialized as definite state for addressing this problem.Though traditional rc reset circuit also can be than good berth, its reliability is not high; Along with the reduction on the voltage checking chip price, the advantage of high reliability is widely adopted gradually.The present invention adopts voltage checking chip to do reset circuit, improves the reliability of device, strong interference immunity, compared with traditional resistance-capacitance circuit be subject to disturb, the characteristics of poor stability, the chip that resets is anti-shake, the not misoperation easily with the fluctuation of power supply.

Existing protective device is single in the one-phase ground protection range of application; the present invention has adopted the zero sequence compensation admittance method to NUS system and NES system; one cover hardware unit can be realized; in NUS system, NES system, all be suitable for; and be not subjected to the influence of transition resistance; the protection algorithm accuracy height, the good reliability that adopt can improve the identification accuracy and the real-time of faulty line, adopt accurate zero sequence current mutual inductor to reduce the influence of unsymmetrical current to the route selection reliability simultaneously.The single-chip microcomputer of protective device is made of high-performance single-chip microcomputer C8051F206, can directly use and be equiped with the 10kV small current neutral grounding system of threephase current transformer or zero sequence current mutual inductor, as the automatic route selection protective device of single phase ground fault; Its power supply comes from the Current Transformer Secondary side, obtain through overcurrent-voltage transformer, the zero-sequence current identification range utilizes to carry in the single-chip microcomputer that residual voltage is gathered in A/D conversion, current conversion becomes digital quantity between 0.5A-5A, and its measuring principle figure as shown in Figure 4.The connector form is selected in the outlet wiring of apparatus of the present invention for use; making things convenient for the user to carry out wiring connects; and be provided with malfunction indicator lamp and normal running indicator; make things convenient for the whether normally operation of staff's finder; not needing the staff to climb on the circuit closely watches; whether the ruuning situation discriminating gear that only needs viewing apparatus indicator light below operate as normal; bring great convenience to the staff; use independent closed cell cabinet, good airproof performance, anti-interference; firm reliable; the anti-vibration ability is strong; the RS232 communication modes of protective device, the reliability height, protective device uses the GPRS module; can directly link existing mobile communications network; reduce the construction cost of communication network, have networking fast, the communication reliable characteristics.

Description of drawings

Fig. 1 is a protective device structured flowchart of the present invention.

Fig. 2 is protective device circuit theory diagrams of the present invention.

Fig. 3 is a protective device power circuit schematic diagram of the present invention.

Fig. 4 gathers measuring principle figure for zero-sequence current in the guard method of the present invention.

Fig. 5 is zero sequence compensation admittance action plane graph of a relation in the guard method of the present invention.

Fig. 6 is a protective device liquid crystal display circuit schematic diagram of the present invention.

Fig. 7 differentiates flow chart for protective device single-chip microcomputer of the present invention carries out the zero sequence compensation node-pair method; N among Fig. 7 is equivalent to a counter, and the frequency of record trouble prevents to disturb and causes erroneous judgement disconnected, and differentiation adds up.

Fig. 8 is the communication subprogram block diagram of step among Fig. 7 (6).

Fig. 9 is a guard method interrupt service routine block diagram of the present invention.

Embodiment

Apparatus of the present invention constitute as shown in Figure 1, form by power module, electric quantity signal collecting module, display module, switching value output module, one-chip computer module and communication module, the output of power module, electric quantity signal collecting module connects one-chip computer module, display module, switching value output module and communication module are connected with the one-chip computer module two-wire, and communication module is connected by RS232 with the GPRS module.

Power module as shown in Figure 3.By line current instrument transformer CT secondary side, obtain through overcurrent-voltage transformer, circuit CT secondary side current flows into the micro-transformer of current CT3 of the inner 5VA of power module, during minitype CT 3 secondary sides open circuit, its voltage saturation, and size is constant substantially; Power module is obtained the electric current of the Current Transformer Secondary side of electric quantity signal collecting module by current transformer CT3; suppress circuit, integrated voltage stabilizing chip, decide that the voltage input is high to be isolated single output of non-voltage stabilizing and obtain required voltage through common mode and differential mode; as shown in Figure 3; TVS1, TVS2, TVS3 are Transient Voltage Suppressor P6KE series, carry out between the two-phase respectively, A relatively, C protection relatively.CY1 and CY2 are common mode inhibition electric capacity, and selecting withstand voltage is 50V, and capacity is the ceramic condenser of 10nF, and its common port and TVS2, TVS3 common port insert the earth by controller housing.CX1 and CX2 are that differential mode suppresses electric capacity, and selecting withstand voltage is 63V, and capacity is the thin-film capacitor of 0.1 μ F.Because going up the accumulation of electric charge, CX1 can influence filtering characteristic, so on CX1 and the bleeder resistance RX of the United Nations General Assembly's resistance.Ensuing full-wave rectifying circuit, filter circuit make alternating voltage become the little 12V direct voltage of fluctuation, promptly can be the relay power supply.Start-up circuit, serial regulating circuit, protective circuit are contained in integrated voltage stabilizing chip 7805 inside; + 12V direct voltage is become stable+5V voltage; be the power supply of devices such as clock chip DS1307, amplifier; voltage stabilizing didoe Z1 with the overvoltage Limiting of circuit at certain level, protection relay coil and back level 7805 devices such as grade.Again+5V direct voltage being become stable+3.3V voltage, is the one-chip computer module power supply, and capacitor C 1 can suppress the noise that produces because of load variations, plays a part a low frequency disturbance filter, and output connects the E2 electrochemical capacitor and guarantees the stability exported.Adopt insulating power supply F0303S-1W to provide power supply for output stage, circuit as shown in Figure 3, F0303S-1W decides voltage to import single out-put supply module, input voltage is 3V～3.5VDC, output voltage is 3VDC, and isolation voltage can reach 3000VDC, maximum output current 200mA.

One-chip computer module, electric quantity signal collecting module, switching value output module and communication module as shown in Figure 2, display module is as shown in Figure 6.

Electric quantity signal collecting module comprises filter circuit, adopts second order voltage controlled voltage source low-frequency filter circuit, it has-and the maximum attenuation frequency of 40dB/ ten frequencys multiplication, and also in the unwanted signal of decaying to greatest extent, the influence that makes useful signal be subjected to is less.

The one-chip computer module of apparatus of the present invention adopts the single-chip microcomputer C8051F206 of Silicon Laboratories company, self have the A/D ALT-CH alternate channel, in the demonstration of Fig. 2, only used two-way, to the online detection single phase ground fault of a circuit, online detection when can realize at most to four circuits.The present invention adopts the shine voltage transformer TV19E summation current transformer TA1915LB of magnificent Dechang of Beijing, the small voltage signal that becomes single-chip microcomputer to detect with current transitions residual voltage.Use operational amplifier LM358, adopt see-saw circuit; Used reset circuit simultaneously, the voltage monitoring chip of employing is the MAX708RD of PHILIPS Co..MAX708RD is the voltage monitoring chip of a 3.3V of being used for power-supply system, and the threshold voltage that resets is 2.63V, has double loop power supply monitoring, power-fail alarm, auto-reset function and hand-reset function, as shown in Figure 2.When reset button SW1 closure, system have just powered on or the supply voltage of MAX708RD drops to 2.63V when following, low active homing output pin step-down, chip C8051F206 reliable reset.When electric circuit inspection arrives fault alarm, use button to carry out resetting again of equipment, detection line again.And used the relay output circuit, used fast diode IN4148, the electric current on the relay coil has been carried out the moment afterflow.When line failure, provide a switching signal.In order to realize communication function with the note cat of GPRS module, adopt the RS232 communicating circuit, its core is the LPC23 series processors of Philip, supports communication functions such as data, voice, short message and fax, have limit slope drive function simultaneously, can effectively contain the generation of interference.Use isolation technology to carry out the electrical isolation of communication module and control module simultaneously, improve communication and whole device reliability.

Adopt voltage transformer, current transformer that the big voltage and the big electric current in the external world are changed into the operable small voltage of single-chip microcomputer and little electric current in the protective device of the present invention; small voltage and little electric current insert the negative terminal of two operational amplifiers respectively; be transformed into voltage signal; by the output of two operational amplifiers directly insert the pin 37 of single-chip microcomputer C8051F206 and pin 38 A the D conversion port, realize the collection of extraneous analog signal.Reset circuit inserts the pin 14 low voltage resetting ports of single-chip microcomputer; The 16MHz crystal oscillator inserts the pin 9,10 of single-chip microcomputer respectively, for single-chip microcomputer provides clock; Single-chip microcomputer run indicator and malfunction indicator lamp insert the pin 34,35 of single-chip microcomputer respectively; The switching value output signal line of relay inserts the pin 36 of single-chip microcomputer by the electrical isolation of optocoupler.Communication module adopts RS232 level transferring chip and protective circuit to form; single- chip microcomputer pin 40,39 inserts 11,10 pins of RS232 level transferring chip, and the pin one 5,14,7,16 of RS232 level transferring chip is connected with power supply with power supply ground, semi-duplex serial port communication respectively.

The defencive function of protective device of the present invention is devoted oneself to work during greater than a setting value at zero-sequence current, residual voltage; setting value can be made amendment according to the requirement at scene; as the scene give given data at zero-sequence current less than 10A; residual voltage is during less than 30V; be considered as not being that low current grounding occurs; the setting value that zero-sequence current then can be set is 10A, and the setting value of residual voltage is 30V.Device provides two LED display lamps, is respectively single-chip data and calculates indication (green light) and faulty indication (red light).Whether normally after the unit protection function had dropped into, single-chip data calculated the flicker in indicator light meeting gap, make things convenient for the operation of staff's judgment means; When having single phase ground fault in the judgement system, the faulty indication lantern festival is lighted, and the prompting staff carries out trouble hunting.Device not only provides the malfunction indicator lamp indication after there is single phase ground fault in judgement, the relay switch signal externally is provided simultaneously.For the interference signal or the short-lived fault of preventing moment in the locking system makes the erroneous judgement of device generation disconnected, device provides memory function, continues to detect fault-signal in a setting time, and device just is judged as the generation single phase ground fault.This setting time can be made amendment according to field requirement.After device was judged fault, process personnel's maintenance made fault eliminating in the system, and the faulty indication lantern festival of device is extinguished automatically; Device also provides reset button, can the people be that the single phase ground fault that makes system drop into circuit again detects.Device provides the UART serial line interface RS232 and the RS485 of standard optional, and apparatus of the present invention adopt the RS232 communication port, and the function of antistatic and anti-thunderbolt is arranged.Adopt isolation technology to make communication part and the complete electrical isolation of kernel control chip simultaneously, the reliability of communication and the whole anti-interference of device effectively are provided.Communication function can be selected to use by customer requirements.

Mainly by chip microcontroller, as shown in Figure 7, its step is as follows in guard method of the present invention:

(1) initialization;

(2) determining the mode of connection, is isolated neutral NUS or neutral by arc extinction coil grounding NES;

(3) if NUS under the single-phase earthing stable state, calculates the sinusoidal coefficient u of zero-sequence fundamental voltage _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1c, judge whether i _1su _1s+ i _1cu _1c＜0, i _1cu _1s-i _1su _1c＜0, if satisfy simultaneously, earth fault has then taken place, change step (6) over to, otherwise change step (7) over to;

(4), judge compensation admittance fiducial value Y if NES calculates the compensation admittance _Per, if satisfy | Y _Per|＜1.5% earth fault has taken place, and changes step (6) over to, otherwise judges whether | Y _Per| 20%, earth fault has then taken place if satisfy, change step (6) over to, if all do not satisfy | Y _Per|＜1.5% He | Y _Per| 20%, change step (5) over to;

(5) judge compensation admittance angle θ, if satisfy 180 °-θ, 1＜θ＜180 °+θ ₂, earth fault has then taken place, change step (6) over to, otherwise change step (7), wherein θ over to ₁Be overcompensation trip boundary angle, θ ₂Be undercompensation trip boundary angle;

(6) counter adds 1, and whether counter reports to the police if satisfy greater than setting threshold, calls the communication subprogram simultaneously; Otherwise change step (2) over to;

(7) return step (1);

The described setting threshold of step (6) is judged number of times for carrying out earth fault, generally is made as 5 times.

Under the single-phase earthing stable state, the mathematical description f (t) of residual voltage, electric current belongs to non-sine cycle time-varying function, can be expressed as with fourier series:

In the formula, I ₀-DC component, i ₀=I ₀

The harmonic number of k-harmonic component;

The high order harmonic component number of times of K-harmonic component;

I _KmThe amplitude of-k subharmonic, and $I_{\mathrm{km}}=\sqrt{a_{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">k</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="b\; k"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">b</figure-callout>}}_k^{}};$

The initial phase angle of-k subharmonic, and

a _kThe cosine coefficient of-k subharmonic, and

b _kThe sinusoidal coefficient of-k subharmonic, and

After the elimination DC component, obtain zero-sequence fundamental voltage, the electric current of expressing with the Fu Shi coefficient under the single-phase earthing stable state:

Zero-sequence fundamental voltage u ₁=u _1cCos ω t+u _1sSin ω t

The fundamental wave zero sequence current i ₁=i _1cCos ω t+i _1sSin ω t

Then u _1mBe the amplitude of fundamental voltage, i _1mAmplitude for fundamental current.

When using on apparatus of the present invention, single-chip microcomputer calculates the sampled signal of discrete type, supposes that the sampling number in every-individual cycle is N, and sampling order is M=0～(N-1), then has formula to be:

$i_{\mathrm{kc}}=\frac{2}{N}\underset{M=0}{\overset{N-1}{\mathrm{\&Sigma;}}}f\left(\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">M</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\right)\cos \left(\mathrm{<figure-callout\; id="2"\; label="kM"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">kM</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\right)$

$i_{\mathrm{ks}}=\frac{2}{N}\underset{M=0}{\overset{N-1}{\mathrm{\&Sigma;}}}f\left(\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">M</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\right)\cos \left(\mathrm{<figure-callout\; id="2"\; label="kM"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">kM</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\right)$

For can calculate accurately, residual voltage when asking for k=1 simply and zero sequence Shen stream fundametal compoment, as get N=24, then have:

$i_{1c}=\frac{2}{24}\underset{0}{\overset{23}{\mathrm{\&Sigma;}}}f\left(M\frac{\mathrm{\&pi;}}{12}\right)\cos \left(M\frac{\mathrm{\&pi;}}{12}\right)$

$=\frac{1}{12}[(f_0-f_{12})+0.259(f_5-f_7-f_{17}+f_{19})+$

$0.5(f_4-f_8-{\mathrm{<figure-callout\; id="16"\; label="f"\; filenames="A200910025403E00181.png"\; state="\{\{state\}\}">f</figure-callout>}}_{16}+f_{20})+0.707(f_3-f_9-{\mathrm{<figure-callout\; id="15"\; label="f"\; filenames="A200910025403E00181.png"\; state="\{\{state\}\}">f</figure-callout>}}_{15}+f_{21})+$

$0.866(f_2-f_{10}-{\mathrm{<figure-callout\; id="14"\; label="f"\; filenames="A200910025403E00181.png"\; state="\{\{state\}\}">f</figure-callout>}}_{14}+f_{22})+0.966(f_1-f_{11}-{\mathrm{<figure-callout\; id="13"\; label="f"\; filenames="A200910025403E00181.png"\; state="\{\{state\}\}">f</figure-callout>}}_{13}+f_{23})]$

$i_{1s}=\frac{2}{24}\underset{0}{\overset{23}{\mathrm{\&Sigma;}}}f\left(M\frac{\mathrm{\&pi;}}{12}\right)\sin \left(M\frac{\mathrm{\&pi;}}{12}\right)$

$=\frac{1}{12}[(f_6-f_{18})+0.259({\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+f_{11}-f_{13}-f_{23})+$

$0.5({\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">f</figure-callout>}}_2+f_{10}-f_{14}-f_{22})+0.707({\mathrm{<figure-callout\; id="3"\; label="f"\; filenames="A200910025403E00181.png"\; state="\{\{state\}\}">f</figure-callout>}}_3+f_9-f_{15}-f_{21})+$

$0.866({\mathrm{<figure-callout\; id="4"\; label="f"\; filenames="A200910025403E00181.png,A200910025403E00192.png"\; state="\{\{state\}\}">f</figure-callout>}}_4+f_8-f_{16}-f_{20})+0.969({\mathrm{<figure-callout\; id="5"\; label="f"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">f</figure-callout>}}_5+f_7-f_{17}-f_{19})]$

F in the formula ₀～f ₂₃Residual voltage or zero-sequence current instantaneous value when being respectively M=0～23 time sampling.

According to the first-harmonic amount of residual voltage, zero-sequence current, calculate zero sequence and measure admittance ${\stackrel{\&CenterDot;}{Y}}_1=\frac{{\stackrel{\&CenterDot;}{I}}_1}{{\stackrel{\&CenterDot;}{U}}_1}.$ Behind the NUS system single-phase earthing, zero sequence is measured the third quadrant that admittance is positioned at the admittance complex plane, promptly Getting real part and imaginary part respectively can get:

$\mathrm{Re}\left({\stackrel{\&CenterDot;}{Y}}_1\right)=\mathrm{Re}\left(\frac{{\stackrel{\&CenterDot;}{I}}_1}{{\stackrel{\&CenterDot;}{U}}_1}\right)<0$

$\mathrm{Im}\left({\stackrel{\&CenterDot;}{Y}}_1\right)=\mathrm{Im}\left(\frac{{\stackrel{\&CenterDot;}{I}}_1}{{\stackrel{\&CenterDot;}{U}}_1}\right)<0$

Promptly

Top formula both sides be multiply by U respectively ₁I ₁, can get:

i _1su _1s+i _1cu _1c<0

i _1cu _1s-i _1su _1c<0

Top formula is in the NUS system, and the criterion of single phase ground fault in the NUS system, if above-mentioned two formula all satisfy, single phase ground fault has taken place then.Do not satisfy condition, single phase ground fault does not then take place.

Behind the NES system single-phase earthing,, need protect and adjust, as shown in Figure 5 according to operating space figure.Before judgement, earlier normalized is carried out in the compensation admittance, its fiducial value is elected the zero sequence susceptance of each bar circuit as:

Y _per＝Y _comp/b _set

Y _PerFiducial value, the Y of expression compensation admittance _CompFor the compensation admittance, work as Y _PerDuring greater than certain threshold value, directly be judged to line fault, otherwise, utilize operating space figure to judge.When compensation admittance when falling into the fault zone of left half-plane, be judged to line fault, otherwise it is normal to be judged to circuit.If the compensation admittance of all circuits is all at non-active region, after after a while, residual voltage is involution not yet, and fault is judged to busbar fault.

At first, the little radius of a circle of adjusting, promptly the electricity of arc suppression coil is led component, and the percentage that the active loss of arc suppression coil can account for compensation capacity is 1.5%～2%, generally is taken as 1.5%.According to formula

$Y_{\mathrm{comp}}=Y_k-Y_{\mathrm{set}}=-(g_L+\underset{i}{\mathrm{\&Sigma;}}{g}_i)-j[\mathrm{\&upsi;}\underset{i=2}{\overset{n}{\mathrm{\&Sigma;}}}{b}_i+(\mathrm{\&upsi;}-1)b_1]-{\mathrm{<figure-callout\; id="1"\; label="jb"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">jb</figure-callout>}}_1$

$=-(g_L+\underset{i}{\mathrm{\&Sigma;}}{g}_i)-\mathrm{j\&upsi;}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{b}_i$

Y _kBe system's admittance, b _iBe the admittance of i subharmonic zero sequence,

Be zero sequence admittance sum except that first-harmonic.

When each bar non-fault line is lossless line and bucking coil when operating in resonance point, the minimum modulus value will appear in faulty line compensation admittance, and the electricity that this minimum modulus value is an arc suppression coil is led component g _LGenerally speaking, the percentage that the active loss of arc suppression coil can account for compensation capacity is 1.5%～2%, promptly

g _L＝(1.5％～2％)×(1-υ)b _∑

Y _per＝g _L/b ₁＝[(1.5％～2％)×(1-υ)b _∑]/b ₁

Wherein, b _SetFor zero sequence susceptance, υ are off resonance degree, b _∑Be total susceptance,

Be that the total electricity of non-fault line is led.

By following formula as can be known: Y _PerThe condition of getting minimum value is the harmless and b of circuit ₁=b _∑, promptly the susceptance of faulty line has accounted for absolute specific gravity in total susceptance, υ under the resonance compensation state=0, and have this moment | Y _Per| _Min=1.5%.In fact, the satisfied simultaneously probability of above-mentioned condition is very little.Get 0.015 as the little radius of a circle of admittance action plane, then any faulty line admittance all can not fall in this circle.

Secondly, consider adjusting of active region border.Suppose when carrying out admittance measurement that the measure error of susceptance can not surpass 20%.If promptly | Y _Per| 20%, then directly declaring this circuit is faulty line; If | Y _Per|＜20%, for faulty line, lead part for negative because of electricity, the compensation admittance is positioned at the left-half on admittance plane all the time; For non-fault line, worst criterion is: circuit is harmless, and the susceptance error is then differentiated the result and depended on the positive and negative of error again more than 1.5%, and its admittance angle will be positioned on the positive and negative imaginary axis.And generally speaking, when the influence of line conductance can not be ignored, I or IV quadrant will be partial in the admittance angle.No matter be above which kind of situation, the compensation admittance of non-fault line all can not enter the left-half on admittance plane, and therefore, non-fault line and faulty line all can be realized distinguishing by compensation admittance angle.For strengthening the reliability of criterion, in conjunction with consideration, to inquire under the worst condition practical factor, the upper and lower limit that faulty line compensation admittance angle may reach is with this differentiation threshold as faulty line.

Can get by the front formula,

$Y_{\mathrm{per}}=-(g_L+\underset{i}{\mathrm{\&Sigma;}}{g}_i)/b_1-\mathrm{j\&upsi;}\frac{b_{\mathrm{\&Sigma;}}}{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="A200910025403E00181.png,A200910025403E00191.png"\; state="\{\{state\}\}">b</figure-callout>}}_1}$

Y _PerWith the angle of negative real axis be $\mathrm{\&theta;}=\arctan \left|\mathrm{\&upsi;}\right|b_{\mathrm{\&Sigma;}}/(g_L+\underset{i}{\mathrm{\&Sigma;}}{g}_i),$ Under a certain definite compensativity, line is harmless when perfecting, g _LGet hour, this phase angle maximum, promptly with the angle minimum of the imaginary axis, at this moment, g _Lmin=1.5% (1-υ) b _∑, therefore, θ is arranged _Max=arctan{| υ |/[1.5% * (1-υ)] }, when | υ | when maximum, promptly | υ |=20% o'clock, overcompensation trip boundary angle θ ₁=arctan{0.2/[1.5% * (1+0.2)]=84.86 °, the trip boundary angle that can try to achieve similarly under the undercompensation state is θ ₂=arctan{0.2/[1.5% * (1-0.2)]=86.57 °, so far, all faulty section trip boundaries are all definite.

Use when of the present invention; at first the single-chip microcomputer of protective device is carried out the initialization of each pin and function; detect residual voltage, zero-sequence current then; after electric current, magnitude of voltage are greater than a setting value; determine the mode of connection; if NUS, calculate the sinusoidal coefficient u of zero-sequence fundamental voltage according to the operation equation of zero sequence admittance selection method _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1cJudge whether

If satisfy simultaneously, start zero sequence compensation admittance fault line detection program and report to the police.If NES calculates compensation admittance and admittance angle, satisfy condition, start zero sequence compensation admittance fault line detection program and report to the police, step is as shown in Figure 7.In one-period, residual voltage and zero-sequence current by 12 points of all-wave sequential sampling, and be kept in the data storage, respectively sampled point is stored data and brought into the computing formula of having derived, calculate and judge needed four parameters, and provide the conversion of single-chip microcomputer relay indicating light, again calculating parameter is brought into the generation signal of judgment formula failure judgement.Disconnected for preventing the erroneous judgement that extraneous impulse disturbances causes, adopt the mode that adds up to guarantee the reliability service of program, i.e. the fault judgement threshold value of setting in the step (6).

Communication subprogram in the inventive method comprises following steps, as shown in Figure 8:

(1) the GPRS messaging format is provided with, initiation parameter;

(2) send the instruction that connects;

(3) judge whether the GPRS module connects, change step (4) over to if connected, otherwise change step (2) over to;

(4) send SMS message;

(5) judge whether short message sends success,, change step (6) over to, otherwise change step (4) over to if send successfully;

(6) return.

Be in operation as interrupting, can start interrupt service routine automatically.Interrupt service routine may further comprise the steps, as shown in Figure 9;

(1) SWCINT interrupt requests;

(2), otherwise change step (5) over to if satisfy from GPRS module reception data;

(3) judged whether short message, extracted message if satisfy, otherwise change step (5) over to;

(4) judge whether separating brake according to short message, carry out separating brake if satisfy, otherwise change step (5) over to;

(5) interrupt returning.

Claims (8)

1; small current earthing wire-selecting protective device based on GPRS; it is characterized in that comprising power module; electric quantity signal collecting module; display module; the switching value output module; one-chip computer module; communication module and GPRS module; power module; the output of electric quantity signal collecting module connects one-chip computer module; display module; the switching value output module is connected with the one-chip computer module two-wire with communication module; communication module is connected by RS232 with the GPRS module; electric quantity signal collecting module is by electric current; voltage transformer and operational amplifier; filter circuit is formed; filter circuit is a second order voltage controlled voltage source low-frequency filter circuit; one-chip computer module comprises the C8051F206 chip; corresponding crystal oscillating circuit and reset circuit; display module is made up of the LED display lamp; the switching value output module is by relay; drive triode and protective circuit and form, communication module is made up of RS232 level transferring chip and protective circuit.

2; small current earthing wire-selecting protective device based on GPRS according to claim 1; it is characterized in that described power module is obtained the electric current of the Current Transformer Secondary side of electric quantity signal collecting module by the current/voltage converter; suppress circuit through common mode and differential mode; current rectifying and wave filtering circuit; integrated voltage stabilizing chip; decide the single output of the non-voltage stabilizing of the high isolation of voltage input and obtain required voltage; be specially: the electric current of the Current Transformer Secondary side of electric quantity signal collecting module is through common mode and differential mode suppresses circuit and current rectifying and wave filtering circuit inserts integrated voltage stabilizing chip 7805 and SPX1117M3_3.3; export the voltage of 5V and 3.3V respectively; guarantee the stable of output by decoupling capacitor and shunt capacitance; wherein the 5V power supply singly is output as the insulating power supply that communication module provides 5V through deciding the non-voltage stabilizing of the high isolation of voltage input, and 3.3V provides power supply for single-chip microcomputer C8051F206.

3, the small current earthing wire-selecting protective device based on GPRS according to claim 1 and 2 is characterized in that reset circuit is the voltage checking chip MAX708RD of PHILIPS Co., connects the reset terminal of C8051F206 chip.

4, based on the small current earthing wire-selecting guard method of GPRS, it is characterized in that adopting the zero sequence compensation admittance method, under the single-phase earthing stable state, gather residual voltage, zero-sequence current, because residual voltage is U behind the single-phase earthing ₀∈ (30V 100V), starts the route selection program when monitoring after residual voltage surpasses 30V, and its fault judgement step is as follows:

(1) initialization;

(2) according to the earthing mode that will carry out fault judgement, determine to carry out isolated neutral NUS fault judgement or neutral by arc extinction coil grounding NES fault judgement;

(3) if NUS under the single-phase earthing stable state, calculates the sinusoidal coefficient u of zero-sequence fundamental voltage _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1c, judge whether i _1su _1s+ i _1cu _1c＜0, i _1cu _1s-i _1su _1c＜0, if satisfy simultaneously, earth fault has then taken place, change step (6) over to, otherwise change step (7) over to;

(4), judge compensation admittance fiducial value Y if NES calculates the compensation admittance _Per, if satisfy | Y _Per|＜1.5% earth fault has taken place, and changes step (6) over to, otherwise judges whether | Y _Per| 20%, earth fault has then taken place if satisfy, change step (6) over to, if all do not satisfy | Y _Per|＜1.5% He | Y _Per| 20%, change step (5) over to;

(5) judge compensation admittance angle θ, if satisfy 180 °-θ ₁＜θ＜180 °+θ ₂, earth fault has then taken place, change step (6) over to, otherwise change step (7), wherein θ over to ₁Be overcompensation trip boundary angle, θ ₂Be undercompensation trip boundary angle;

(6) counter adds 1, and whether counter reports to the police if satisfy greater than setting threshold, calls the communication subprogram simultaneously; Otherwise change step (2) over to;

(7) return step (1);

The described setting threshold of step (6) is judged number of times for carrying out earth fault.

5, the small current earthing wire-selecting guard method based on GPRS according to claim 4 is characterized in that the sinusoidal coefficient u of zero-sequence fundamental voltage among the NUS _1s, zero-sequence fundamental voltage cosine coefficient u _1c, the fundamental wave zero sequence electric current sinusoidal coefficient i _1s, the fundamental wave zero sequence electric current cosine coefficient i _1cAcquisition be: under the single-phase earthing stable state, the mathematical description f (t) of residual voltage, electric current is expressed as with fourier series:

In the formula, I ₀-DC component, i ₀=I ₀

The harmonic number of k-harmonic component;

The high order harmonic component number of times of K-harmonic component;

I _KmThe amplitude of-k subharmonic, and $I_{\mathrm{km}}=\sqrt{a_k^2+b_k^2};$

The initial phase angle of subharmonic, and

a _kThe cosine coefficient of-k subharmonic, and

b _kThe sinusoidal coefficient of-k subharmonic, and

After the elimination DC component, obtain zero-sequence fundamental voltage, the electric current of expressing with the Fu Shi coefficient under the single-phase earthing stable state:

Zero-sequence fundamental voltage u ₁=u _1cCos ω t+u _1sSin ω t

The fundamental wave zero sequence current i ₁=i _1cCos ω t+i _1sSin ω t

Then

u _1mBe the amplitude of fundamental voltage, i _1mAmplitude for fundamental current.

6, according to claim 4 or 5 described small current earthing wire-selecting guard methods, it is characterized in that the communication subprogram of calling in the described step (7) comprises following steps based on GPRS:

(1) the GPRS messaging format is provided with, initiation parameter;

(2) send the instruction that connects;

(3) judge whether the GPRS module connects, change step (4) over to if connected, otherwise change step (2) over to;

(4) send SMS message;

(5) judge whether short message sends success,, change step (6) over to, otherwise change step (4) over to if send successfully;

(6) return.

7, according to claim 4 or 5 described small current earthing wire-selecting guard methods based on GPRS, it is characterized in that can starting interrupt service routine automatically as interrupting when in service, it interrupts package of service program draws together following steps:

(1) SWCINT interrupt requests;

(2), otherwise change step (5) over to if satisfy from GPRS module reception data;

(3) judged whether short message, extracted message if satisfy, otherwise change step (5) over to;

(4) judge whether separating brake according to short message, carry out separating brake if satisfy, otherwise change step (5) over to;

(5) interrupt returning.

8, the small current earthing wire-selecting guard method based on GPRS according to claim 6 is characterized in that can starting interrupt service routine when in service automatically as interrupting, and it interrupts package of service program draws together following steps:

(1) SWCINT interrupt requests;

(2), otherwise change step (5) over to if satisfy from GPRS module reception data;

(3) judged whether short message, extracted message if satisfy, otherwise change step (5) over to;

(4) judge whether separating brake according to short message, carry out separating brake if satisfy, otherwise change step (5) over to;

(5) interrupt returning.

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