CN103176049B - For circuit, apparatus and method that the insulation against ground of earth-free straight-flow system is monitored - Google Patents

Abstract

The present invention is directed to the insulation against ground that accurately can not detect earth-free straight-flow system at present, circuit, the apparatus and method of the insulation against ground of the earth-free straight-flow system of the monitoring overcoming this shortcoming are provided.Comprise resistor R1 in a circuit according to the invention, resistor R2, resistor R0, resistor Rs, voltage sensor and signal generator, the first terminal of resistor R1 connects the positive bus-bar of earth-free straight-flow system, the first terminal of resistor R2 connects the negative busbar of earth-free straight-flow system, first input end of voltage sensor and the second input terminal and lead-out terminal electric isolution, second terminal of first input end sub-connection resistor R1, second terminal of the second input terminal contact resistance device R2, lead-out terminal exports the voltage between positive bus-bar and negative busbar measured, the first terminal of resistor R0 connects negative busbar, the first terminal of the second connecting terminals termination resistor Rs, second terminal of the first terminal contact resistance device Rs of signal generator, second terminal ground, 3rd terminal reception control signal.

Description

For circuit, apparatus and method that the insulation against ground of earth-free straight-flow system is monitored

Technical field

The present invention relates to insulating monitoring field, particularly relate to circuit, the apparatus and method of a kind of insulation against ground for earth-free straight-flow system monitoring.

Background technology

Current DC power-supply system generally all adopts the method for operation of insulation against ground, when there is one point earth, can't cause any harm; but must process in time; otherwise when there is another one point earth, just likely make relay protection generation mistake action and rejecting action, so that damage equipment.Therefore the insulation against ground monitoring of earth-free straight-flow system is very important.

At present, following several technology is adopted to the insulativity monitoring of earth-free straight-flow system is main.

The first technology is that classical bridge method detects, its schematic diagram as shown in Figure 1, wherein, voltage between positive and negative busbar is E, and resistor R1, R2 are balance resistance and its general value is below 100k Ω, and resistor R+, R-are respectively positive and negative busbar insulation against ground resistance, K is overcurrent relay, Is is the reometer for detecting the electric current flowing through overcurrent relay K, and when ground current reaches setting valve, K action makes to send grounding alarm signal.Certainly, current measurement sampling resistor also can be adopted to replace K to record the voltage of a point.Voltage U ab in Fig. 1 between a, b 2 can be represented by the formula:

U _ab＝E*[R ₁/(R ₂+R ₁)-R ₊/(R ₊+R _-) (1)

Can find out: 1. when positive and negative busbar insulation against ground is good, bridge balancing, Uab=0; 2., when grounding phenomenon appears in positive bus-bar or negative busbar insulation against ground decline, Uab > 0 or Uab < 0, occurs " just over the ground " or " bearing over the ground ", and when Uab reaches threshold value alarm.But, the function of this detection technique is too dull, it only can be reported to the police to system earth, but usually can not indication fault place branch road and grounding resistance, if R+ and R-equal proportion declines thus occurs symmetry earth fault, also cannot report to the police even if then out-of-limit, and when there is high resistance ground but R+ and R-difference is larger, but can false alarm.

The second technology is low-frequency signal injection detection method, and as shown in Figure 2, wherein kx is low frequency generator to its Cleaning Principle figure, and Is is the reometer for detecting electric current.After earth fault appears in straight-flow system, between fault bus and ground, injecting the low frequency 30V alternating signal of 5Hz, 10Hz or 20Hz, detecting ground connection branch road by detecting current amplitude change.Low-frequency current flows out from signal generator kx, returns, as shown in Figure 2 via straight-flow system from earth point.Detect with the pointwise of clamp current probe, low-frequency current trend is followed the trail of, first finds ground connection branch road, then find earth point along this branch road, determine earth point position according to the low-frequency current difference before and after earth point.This detection technique needs power failure to search earth point, and its correctness detected and sensitivity affect very large by system distributed capacitance.Straight-flow system positive and negative busbar and feed out each duplexure and there is distributed capacitance over the ground, reach several μ F, such as an electric station DC system total capacitance can reach several 10 μ F when branch road distributed capacitance is maximum.When popping one's head at certain point, because capacitance current flows through, make to be difficult to determine capacitance current or stake resistance electric current.When there is earth point in a certain branch road of system busbar, if the total equivalence value of distributed capacitance all after this branch road is 1 μ F, if signal frequency is 20Hz, electric capacity capacitive reactance is about 8k Ω, when branch resistance is greater than 8k Ω, the electric current flowing to subsequent conditioning circuit, by close with the electric current flowing through fault branch, is difficult to distinguish ground connection branch road.

The third detection technique is table tennis bridge method detection technique, and as shown in Figure 3, wherein R1=R3, R2=R4, forms 3 kinds of circuit states by the on off state of switch S 1, S2 to its Cleaning Principle figure, to sample to the voltage between V+ and V-2 respectively.As Closing Switch S1, S2, the voltage between note V+ and V-2 is U _v+V-1; As Closing Switch S1, cut-off switch S2, the voltage between note V+ and V-2 is U _v+V-2; As cut-off switch S1, Closing Switch S2, the voltage between note V+ and V-2 is U _v+V-3; Then solve according to Ohm law and circuit theory and obtain:

U _+-＝U _V+V-1*(R1+R2+R3+R4)/(R2+R3) (2)

R+＝(R1+R2)*(U _V+V-1-U _V+V-2-U _V+V-3)/U _V+V-3(3)

R-＝(R4+R3)*(U _V+V-1-U _V+V-2-U _V+V-3)/U _V+V-2(4)

The third detection technique substantially overcomes the shortcoming existed in the first detection technique, but when busbar voltage existence fluctuation and system under test (SUT) have obvious distributed capacitance over the ground, can because sampling make the deviation that final result appearance is very large less than correct voltage.

Summary of the invention

The present invention is directed to the above-mentioned shortcoming existed in prior art, a kind of circuit, the apparatus and method that can overcome the monitoring of the insulation against ground for earth-free straight-flow system of above-mentioned shortcoming are provided.

The invention provides the circuit of a kind of insulation against ground for earth-free straight-flow system monitoring, the positive bus-bar of this earth-free straight-flow system is Ry relative to the insulation resistance of the earth, described positive bus-bar is Cy relative to the distributed capacitance of the earth, the negative busbar of this earth-free straight-flow system is Rx relative to the insulation resistance of the earth, described negative busbar is Cx relative to the distributed capacitance of the earth, this circuit comprises resistor R1, resistor R2, resistor R0, resistor Rs, voltage sensor and signal generator, wherein: the first terminal of described resistor R1 is connected to described positive bus-bar, the first terminal of described resistor R2 is connected to described negative busbar, described voltage sensor has first input end, second input terminal and lead-out terminal, the first input end of described voltage sensor is sub and the second input terminal is all electrically isolated from one with described lead-out terminal, and the first input end sub-connection of described voltage sensor is to second terminal of described resistor R1, second input terminal of described voltage sensor is connected to second terminal of described resistor R2, the lead-out terminal of described voltage sensor is for exporting the voltage between described positive bus-bar and described negative busbar measured, the first terminal of described resistor R0 is connected to described negative busbar, second connecting terminals of described resistor R0 receives the first terminal of described resistor Rs, second connecting terminals of described resistor Rs receives the first terminal of described signal generator, second terminal ground of described signal generator, 3rd terminal of described signal generator controls for receiving the control signal that described signal generator produces signal.

The device that the present invention also provides a kind of insulation against ground for earth-free straight-flow system to monitor, this device comprises above-mentioned circuit, and this device also comprises the first sample circuit and processor, wherein:

Described processor controls described signal generator and produces direct current signal;

Described first sample circuit is used for sampling to the DC voltage at described resistor Rs two ends under the control of described processor, and sampled result is fed back to described processor;

Described processor also for receiving the voltage between described positive bus-bar and described negative busbar that described voltage sensor collects, and calculates the resistance value of described insulation resistance Ry and insulation resistance Rx and value in parallel thereof based on the described positive bus-bar that described voltage sensor collects with the sampled result of the voltage between described negative busbar and described first sample circuit.

The present invention also provides a kind of method of monitoring the insulation against ground of earth-free straight-flow system, and the method is based on above-mentioned circuit, and the method comprises:

Control described signal generator and produce the first direct current signal;

Sampling is carried out to the DC voltage at described resistor Rs two ends and obtains the first sampled result;

Be the first voltage by described voltage sensor to the voltage collected between positive bus-bar and negative busbar of the voltage between positive bus-bar and negative busbar;

Control described signal generator and produce the second direct current signal;

Sampling is carried out to the DC voltage at described resistor Rs two ends and obtains the second sampled result;

Be the second voltage by described voltage sensor to the voltage collected between positive bus-bar and negative busbar of the voltage between positive bus-bar and negative busbar;

The resistance value of described insulation resistance Ry and insulation resistance Rx and value in parallel thereof is calculated based on described first sampled result, the first voltage, the second sampled result and the second voltage.

Because the circuit of the insulation against ground for earth-free straight-flow system according to the present invention monitoring, apparatus and method consider the voltage fluctuation of positive and negative busbar when detecting insulation against ground resistance Rx, Ry of earth-free straight-flow system and value in parallel thereof, and eliminate the impact of distributed capacitance on accuracy of detection, thus improve accuracy of detection, enhance antijamming capability.

Accompanying drawing explanation

Fig. 1 is the schematic diagram that in prior art, classical bridge method detects the insulation against ground of earth-free straight-flow system;

Fig. 2 is the schematic diagram that prior art medium and low frequency signal injection method detects the insulation against ground of earth-free straight-flow system;

Fig. 3 is the schematic diagram of the insulation against ground detecting earth-free straight-flow system in prior art by table tennis bridge method;

Fig. 4 is the circuit diagram according to the monitoring of the insulation against ground for earth-free straight-flow system of the present invention;

Fig. 5 is the reduced graph of the circuit diagram in Fig. 4;

Fig. 6 is the equivalent circuit diagram of the circuit diagram in Fig. 5;

Fig. 7 is the vector triangle figure of three;

Fig. 8 is U _aB, U _a, U _bthe triangular graph that three is formed;

Fig. 9 is according to the block diagram of the device for detecting the insulation against ground of earth-free straight-flow system of the present invention;

Figure 10 is the process flow diagram that the insulation resistance of device according to the present invention to earth-free straight-flow system detects;

Figure 11 is the voltage waveform at resistor Rs two ends;

Figure 12 is the process flow diagram of adaptively sampled technology;

Figure 13 is the circuit diagram of the second sample circuit.

Embodiment

Describe in detail according to circuit, apparatus and method for monitoring the insulation against ground of earth-free straight-flow system of the present invention below in conjunction with accompanying drawing.

Fig. 4 shows the circuit according to the monitoring of the insulation against ground for earth-free straight-flow system of the present invention.In shown circuit diagram, earth-free straight-flow system 1 will be carried out the system under test (SUT) of insulativity detection, and the positive bus-bar KM+ of earth-free straight-flow system 1 is Ry relative to the insulation resistance of the earth, this positive bus-bar is Cy relative to the distributed capacitance of the earth, the negative busbar of earth-free straight-flow system 1 is Rx relative to the insulation resistance of the earth, this negative busbar is Cx relative to the distributed capacitance of the earth, and resistor RL is the load of earth-free straight-flow system 1.Then the part shown in dotted line frame in Fig. 4 according to the circuit of the insulation against ground for earth-free straight-flow system of the present invention monitoring, this circuit comprises resistor R1, resistor R2, resistor R0, resistor Rs, voltage sensor 2 and signal generator 3, wherein: the first terminal of described resistor R1 is connected to described positive bus-bar KM+, the first terminal of described resistor R2 is connected to described negative busbar KM-, described voltage sensor 2 has first input end, second input terminal and lead-out terminal, the first input end of described voltage sensor is sub and the second input terminal is all electrically isolated from one with described lead-out terminal, and the first input end of described voltage sensor 2 is connected to second terminal of described resistor R1, second input terminal of described voltage sensor 2 is connected to second terminal of described resistor R2, the lead-out terminal of described voltage sensor 2 is for exporting the voltage U between described positive bus-bar and described negative busbar measured _kM+KM-the first terminal of described resistor R0 is connected to described negative busbar KM-, second connecting terminals of described resistor R0 receives the first terminal of described resistor Rs, second connecting terminals of described resistor Rs receives the first terminal of described signal generator 3, second terminal ground of described signal generator 3, the 3rd terminal of described signal generator 3 controls for receiving the control signal that described signal generator 3 produces signal.In addition, in this circuit diagram, EGND represents the earth, and the ground GND of signal generator 3 is connected to the earth EGND.

According in a preferred embodiment of the present invention, the resistance value of resistor R0 preferably meets certain standard to guarantee that this circuit according to the present invention can not cause the insulation against ground of earth-free straight-flow system 1 to reduce when monitoring the insulation against ground of earth-free straight-flow system 1, but this standard is different because of the difference of application in a circuit according to the invention, usually, when being applied to electric automobiles, the resistance value of resistor R0 and the ratio of bus rated voltage are preferably not less than 100 Ω/V, and when being applied in photo-voltaic power generation station, the resistance value of resistor R0 and the ratio of bus rated voltage are preferably not less than 500 Ω/V.

According in a preferred embodiment of the present invention, resistor R1 and R2 can be power resistor, and voltage sensor 2 is preferably Hall voltage sensor.

According in a preferred embodiment of the present invention, the resistance of resistor Rs is smaller, resistor R0 is then the powerful resistor of large resistance, the resistance of such as resistor Rs and resistor R0 can be respectively 2K and 500K, but those skilled in the art are to be understood that, the resistance value of given resistor Rs and R0 is only example, is not construed as limiting the invention.

When adopting the insulation against ground of circuit to earth-free straight-flow system 1 shown in Fig. 4 to monitor, signal generator 3 can produce direct current signal under the control of its control signal received, the direct current signal produced successively through resistor Rs and R0, afterwards from the negative busbar KM-of earth-free straight-flow system 1 enter earth-free straight-flow system 1, afterwards through earth-free straight-flow system 1 to the earth insulation resistance Ry and Rx get back to GND, thus formed loop.When signal generator 3 produces direct current signal U ₁time, the voltage between the positive and negative busbar remembering earth-free straight-flow system 1 is U _kM+KM-1, the voltage at note resistor Rs two ends is U _rs1, and obtain equation (5) by Ohm law and superposition theorem; When signal generator 3 produces direct current signal U ₂time, in like manner can obtain equation (6), simultaneous equations (5) and (6) also solve, and can obtain resistance value and the parallel resistance value thereof of insulation against ground resistance Rx and Ry of earth-free straight-flow system 1.Certainly, in order to simplify calculated amount, one of them direct current signal (such as U that signal generator 3 can be made to produce ₂) equal 0.Wherein, simultaneous equations (5) and (6) solve the formula (7), formula (8), the formula (9) that obtain is exactly at U ₂obtain when equaling 0.In addition, about the voltage how obtaining resistor Rs two ends, be described combining the device for detecting the insulation against ground of earth-free straight-flow system according to the present invention hereinafter.

$U_{\mathrm{Rs}1}=U_1\&times;\frac{R_s+R_0}{\frac{R_x\&times;R_y}{R_x+R_y}+R_s+R_0}\&times;\frac{R_s}{R_s+R_0}+U_{\mathrm{KM}+\mathrm{KM}-1}\&times;\frac{\frac{(R_s+R_0)\&times;R_x}{(R_s+R_0)+R_x}}{\frac{(R_s+R_0)\&times;R_x}{(R_s+R_0)+R_x}+R_y}\&times;\frac{R_s}{R_s+R_0}---\left(5\right)$

$U_{\mathrm{Rs}2}=U2\&times;\frac{R_s+R_0}{\frac{R_x\&times;R_y}{R_x+R_y}+R_s+R_0}\&times;\frac{R_s}{R_s+R_0}+U_{\mathrm{KM}+\mathrm{KM}-2}\&times;\frac{\frac{(R_s+R_0)\&times;R_x}{(R_s+R_0)+R_x}}{\frac{(R_s+R_0)\&times;R_x}{(R_s+R_0)+R_x}+R_y}\&times;\frac{R_s}{R_s+R_0}---\left(6\right)$

$R_x=\frac{U_{\mathrm{KM}+\mathrm{KM}-1}\&times;(R_s+R_0)\&times;\frac{R_x\&times;R_y}{R_x+R_y}}{U_{\mathrm{KM}+\mathrm{KM}-1}\&times;(R_s+R_0)-U_{\mathrm{Rs}1}\&times;\frac{{(R_s+R_0)}^2}{R_s}-U_{\mathrm{Rs}2}\&times;\frac{R_s+R_0}{R_s}\&times;\frac{R_x\&times;R_y}{R_x+R_y}}---\left(7\right)$

$R_y=\frac{R_x\&times;\frac{R_x\&times;R_y}{R_x+R_y}}{R_x-\frac{R_x\&times;R_y}{R_x+R_y}}---\left(8\right)$

$\frac{R_x\&times;R_y}{R_x+R_y}=(R_s+R_0)\&times;(\frac{U_1}{\frac{R_s+R_0}{R_s}\&times;U_{\mathrm{Rs}2}-\left(\frac{U_{\mathrm{Rs}1}\&times;\frac{R_s+R_0}{R_s}\&times;U_{\mathrm{KM}+\mathrm{KM}-2}}{U_{\mathrm{KM}+\mathrm{KM}-1}}\right)}-1)---\left(9\right)$

As can be seen from formula (9), the value Rx//Ry after resistor Rx with Ry is in parallel contains the magnitude of voltage U between the positive and negative busbar of twice acquisition _kM+KM-1, U _kM+KM-2thus serve the effect of correcting and detecting zero point, that is, when busbar voltage exists fluctuation, when adopting this circuit according to the present invention to carry out insulation against ground detection to earth-free straight-flow system 1, its testing result can not be subject to the impact of busbar voltage fluctuation, therefore, according to this circuit of the present invention, not only structure is simple, and accuracy in detection is high, and antijamming capability is strong.

In the resistance value of insulation against ground resistance Rx, Ry obtaining earth-free straight-flow system 1 and the basis of value in parallel thereof, just can obtain the parallel connection value of the Cx of distributed capacitance over the ground of earth-free straight-flow system 1 and the capacitance of distributed capacitance Cy further, and, when the parallel connection value of the capacitance of Computation distribution electric capacity Cx and distributed capacitance Cy, the circuit shown in Fig. 4 can be reduced to the circuit shown in Fig. 5.The parallel connection value how obtaining the capacitance of discrete capacitor Cx and Cy will be described in detail below.

First, signal generator 3 produces the AC signal (such as sinusoidal signal) with certain frequency f under the control of its control signal received, wherein, the AC signal that signal generator 3 produces enters earth-free straight-flow system 1 from the negative busbar KM-of earth-free straight-flow system 1 successively after resistor Rs and R0, get back to GND through isolation resistor Ry, the Rx of earth-free straight-flow system 1 and discrete capacitor Cx and Cy afterwards, thus form loop.When signal generator 3 produces AC signal, for signal generator 3, earth-free straight-flow system 1 is equivalent to short circuit, and the circuit equivalent therefore shown in Fig. 5 is the circuit shown in Fig. 6.

The AC signal produced for signal generator 3 below illustrates the capacitance how obtaining distributed capacitance Cx and distributed capacitance Cy for sinusoidal signal.First, the voltage of A point is designated as vector the voltage of B point is designated as vector voltage between AB is designated as vector by the vector triangle relation existed between electric circuit knowledge their threes known as shown in Figure 7, namely and the length of side on three limits of vector triangle in Fig. 7 represents each vector field homoemorphism respectively.Because these three vectors all carry out the AC sine signal that automatic signal generator 3 produces, so the effective value U of this ac voltage signal representated by three vectors _aB, U _a, U _bbetween form a triangle similar to the vector triangle shown in Fig. 7, as shown in Figure 8.Can to obtain from the triangular relationship shown in Fig. 8 in conjunction with the cosine law:

$U_{\mathrm{AB}}=\sqrt{{U_A}^2+{U_B}^2-2\&times;U_A\&times;U_B\&times;\cos \mathrm{\&phi;}}---\left(10\right)$

Relevant knowledge from circuit: the effective value of singly-terminal pair port voltage equals the mould of impedance with the ratio of port effective value, namely and the circuit AB section in Fig. 6 is the purely resistive circuit be made up of resistor R0 and Rs, therefore:

$\left|Z\right|=R_0+R_s=\frac{U_{\mathrm{AB}}}{I_{\mathrm{AB}}}---\left(11\right)$

If the impedance over the ground of B point is Z _b, from electric circuit knowledge:

$\left|Z_B\right|=\left|\frac{R_x//R_y\&times;\frac{1}{\mathrm{jw}(C_x+C_y)}}{R_x//R_y+\frac{1}{\mathrm{jw}(C_x+C_y)}}\right|---\left(12\right)$

Again by can obtain:

$\left|Z_B\right|=\frac{U_B}{I_{\mathrm{AB}}}---\left(13\right)$

Simultaneous formula (10), (11), (12), (13) can obtain:

$C=\sqrt{\frac{{U_A}^2+{U_B}^2-2\&times;U_A\&times;U_B\&times;\cos \mathrm{\&phi;}}{4\&times;{\mathrm{\&pi;}}^2\&times;f^2\&times;{U_B}^2{(R_0+R_s)}^2}-\frac{1}{4\&times;{\mathrm{\&pi;}}^2\&times;f^2\&times;{(R_x//R_y)}^2}}---\left(14\right)$

Like this, the value (equivalence value namely Cx in parallel Cy after) of earth-free straight-flow system 1 to the distributed capacitance of the earth is just obtained.In addition, about the voltage effective value U how obtaining A point _a, B point voltage effective value U _band the cosine value cos φ of phase differential between AB two point voltage signal, be described combining the device for detecting the insulation against ground of earth-free straight-flow system according to the present invention below.

Describe in detail according to the device 90 for detecting the insulation against ground of earth-free straight-flow system of the present invention below in conjunction with Fig. 9.As shown in Figure 9, the device 90 that insulation against ground for earth-free straight-flow system according to the present invention is carried out monitoring is except comprising the circuit shown in Fig. 4, also comprise the first sample circuit 902 and processor 901, wherein: described processor 901 controls described signal generator 3 and produces direct current signal; Sampled result for sampling to the DC voltage at described resistor Rs two ends under the control of described processor 901, and is fed back to described processor 901 by described first sample circuit 902; Described processor 901 is also for receiving the voltage between positive bus-bar and negative busbar that described voltage sensor 2 collects, and the sampled result of the positive bus-bar collected based on described voltage sensor 2 and the voltage between negative busbar and described first sample circuit 902 calculates the insulation resistance Ry of earth-free straight-flow system and the resistance value of insulation resistance Rx and value in parallel thereof.

According in a preferred embodiment of the present invention, signal generator 3 can be made up of digital to analog converter and operational amplifier, wherein, digital to analog converter receives digital signal from processor 901, and convert this digital signal to analog signal output to operational amplifier, the output signal of this operational amplifier to analog to digital converter amplifies rear output, thus obtains the signal needed for insulation against ground detection of earth-free straight-flow system.

According in a preferred embodiment of the present invention, can also analog to digital converter be had between the first sample circuit 902 and processor 901, convert with the simulating signal collected by the first sample circuit 902 digital signal that processor 901 can identify to.Certainly, the first sample circuit 902 itself also can integrated analog-to-digital function.In addition, the first sample circuit 902 is preferably difference sample circuit, and make the present invention can be applicable to high-tension earth-free straight-flow system insulativity and detect, such as the present invention goes for the system under test (SUT) up to 1000V.

Wherein, processor 901 is when calculating the resistance value of insulation resistance Ry and insulation resistance Rx and value in parallel thereof, can based on realizing with reference to the algorithm described by Fig. 4 above, the resistance value of its calculating insulation resistance Ry and insulation resistance Rx and the process flow diagram of value in parallel thereof as shown in Figure 10, comprise the following steps:

S101, processor 901 control described signal generator 3 and produce the first direct current signal;

S102, the first sample circuit 902 DC voltage to described resistor Rs two ends is carried out sampling and is obtained the first sampled result U _rs1;

S103, be the first voltage U by the voltage of described voltage sensor 2 pairs between positive bus-bar and the negative busbar voltage collected between positive bus-bar and negative busbar _kM+KM-1;

S104, processor 901 control described signal generator 2 and produce the second direct current signal;

S105, the first sample circuit 902 again carry out sampling to the DC voltage at described resistor Rs two ends and obtain the second sampled result U _rs2;

S106, be the second voltage U to the voltage collected between positive bus-bar and negative busbar of the voltage between positive bus-bar and negative busbar again by described voltage sensor 2 _kM+KM-2;

S107, processor 901 are based on described first sampled result U _rs1, the first voltage U _kM+KM-1, the second sampled result U _rs2with the second voltage U _kM+KM-2calculate the resistance value of described insulation resistance Ry and insulation resistance Rx and value in parallel thereof.

In order to earth-free straight-flow system insulating resistance value Rx//Ry, Rx, Ry to the earth more accurately can be obtained, the first sampled result U _rs1, the first voltage U _kM+KM-1, the second sampled result U _rs2with the second voltage U _kM+KM-2the accurate sampling of these four voltage datas just seems particularly.The present invention by adopt Hall voltage sensor 2 to realize positive and negative busbar between voltage U _kM+KM-1, U _kM+KM-2in real time accurately sampling.Electrical isolation between the input terminal of Hall voltage sensor 2 and lead-out terminal, and the first input end of Hall voltage sensor 2 and the second input terminal are connected respectively to second terminal of resistor R1 and second terminal of resistor R2, and Hall voltage sensor 2 can not affect earth-free straight-flow system insulativity over the ground, when reality uses, by implementing in the voltage range applied at it to demarcate, to guarantee the voltage U that the application obtains _kM+KM-1, U _kM+KM-2accuracy.

How following explanation guarantees the first sampled result U _rs1with the second sampled result U _rs2accuracy.First the voltage waveform at resistor Rs two ends in analyte detection process, as shown in figure 11.Can be clear that by Figure 11, because (in fact earth-free straight-flow system exists distributed capacitance to the earth, generally all there is distributed capacitance to the earth in earth-free straight-flow system, just either large or small difference), so the voltage at resistor Rs two ends has obvious capacitor charge and discharge characteristic, and in fact capacitor charge and discharge process terminate after the voltage at (the CD section namely in Figure 11 or GH section) resistor Rs two ends be only required actual value.But the length of charge and discharge process duration is different and different because of distributed capacitance and insulating resistance value, therefore accurately sampling can not be realized by method such after time delay a period of time simply, for this reason, the application provides a kind of adaptive voltage Sampling techniques to meet this needs, detailed process is as follows: in AD section (or EH section) in fig. 11, the DC voltage of per interval t1 to resistor Rs two ends is sampled until N number of sampled value of sampling, first sampled value and N number of sampled value are compared, if both are equal, show that voltage sample point is arranged in the CD section (or GH section) shown in Figure 11, thus show that capacitor charging (or electric discharge) process completes, therefore the voltage obtained of sampling from resistor Rs two ends is exactly required real voltage, if both are unequal, then continue the DC voltage of per interval t1 to resistor Rs two ends to sample until the N number of sampled value first sampled value and N number of sampled value are compared of sampling.By such sampling flow process, improve efficiency to greatest extent, automatically can either adapt to the different distributions electric capacity of different earth-free straight-flow system, the insulation against ground of earth-free straight-flow system can not be affected again, and also not sacrifice the ageing of monitoring.The process flow diagram of adaptive voltage Sampling techniques as shown in figure 12.

The structure of the application to the first sample circuit 902 does not limit, as long as it can meet the precision needed for detecting the insulation against ground of earth-free straight-flow system.

As shown in Figure 9, the device for detecting the insulation against ground of earth-free straight-flow system according to the present invention also comprises the second sample circuit 903, wherein: described processor 901 also produces AC signal for controlling described signal generator 3; Described second sample circuit 903 for sampling to the alternating voltage at the second terminal place of the first terminal place of described resistor R0 and described resistor Rs and sampled result fed back to described processor 901 under the control of described processor 901; Described processor 901 is also for calculating the parallel connection value of described distributed capacitance Cy and Cx capacitance based on the resistance value of described insulation resistance Rx and Ry and the sampled result of value in parallel and described second sample circuit 903 thereof.According to device of the present invention can Measurement accuracy up to the distributed capacitance of tens μ F, this also provides good foundation by for the field maintemance of system and follow-up design improve.

According in a preferred embodiment of the present invention, the circuit diagram of the second sample circuit 903 as shown in figure 13, wherein, by capacitor C120 and resistor R121, AC signal is sampled, the signal sampled carries out computing by chip CS5464 after being amplified by amplifier 1201 again, finally exports the cosine value of the voltage phase difference in the voltage effective value of the AC signal sampled and Fig. 9 between A, B at 2.Wherein, capacitor C120 preferably high withstand voltage thin-film capacitor.

As shown in Figure 9, device for detecting the insulation against ground of earth-free straight-flow system according to the present invention also comprises the first switch S 1, second switch S2 and the first resistor R10, wherein said first switch S 1 is connected between the earth EGND and the ground GND of this device 90, described second switch S2 is connected between the first terminal of described negative busbar KM-and described first resistor R10, second terminal ground of described first resistor R10, and the break-make of described first switch S 1 and described second switch S2 is controlled by described processor 901.This partial circuit is mainly used in startup self-detection function according to device 90 of the present invention and button self-checking function, and whether the function namely detecting this device 90 when starting shooting is normal.Wherein, the flow process of startup self-detection is as follows: processor 901 controls the first switch S 1 and disconnects, second switch S2 closes, thus disconnect according to the ground GND of the device 90 of the present invention and the earth EGND of earth-free straight-flow system, and simulate the insulation resistance of earth-free straight-flow system to the earth with the resistor R10 of this device 90 inside, then the flow process of the insulation resistance of the earth-free straight-flow system of above-described detection is adopted to detect, if testing result is correct, then processor 901 controls the first switch S 1 and closes, second switch S2 disconnects to start to detect the insulation resistance of earth-free straight-flow system, otherwise, export fault-signal, and self-inspection again.Certainly, ask to carry out self-inspection according to device of the present invention according to the button on device of the present invention if user starts, then device according to the present invention receive user by the signal of key-press input after just carry out self-inspection, its flow process is the same with the flow process of startup self-detection.

According in a preferred embodiment of the present invention, as shown in Figure 9, device 90 according to the present invention also comprises display 904, for the parallel connection value of the capacitance of the resistance value and value in parallel and distributed capacitance Cy and Cx that show insulation resistance Ry and Rx monitored.

According in a preferred embodiment of the present invention, device 90 according to the present invention also comprises the alarm unit 905 be connected with processor 901, and described processor 901 is also reported to the police lower than indicating described alarm unit 905 during threshold value for the parallel connection value at described insulation resistance Ry and Rx.Preferably, can arrange two-stage threshold value, namely first threshold is used for reminding, and Second Threshold is then for reporting to the police.

Between according to a preferred embodiment of the present invention, device 90 according to the present invention can also comprise the communication unit 906 be connected with processor 901, this communication unit 906 is for the parallel connection value of the capacitance of the resistance value and value in parallel and distributed capacitance Cy and Cx that receive insulation resistance Ry and Rx from described processor 901, and they are delivered to outside (such as, passing to host computer).

Except advantage of the present invention above-mentioned, the present invention also has the following advantages: can be applicable to the system having large distributed capacitance over the ground or have counnter attack fly-wheel diode (photovoltaic system); No matter be that one pole insulativity declines or two-stage insulativity declines simultaneously, can detect accurately in real time.

Below only in conjunction with the preferred embodiment of the present invention to invention has been detailed description, but when not deviating from spirit and scope of the invention, various changes and modifications can be carried out to the present invention.

Claims (13)

1. the circuit of the monitoring of the insulation against ground for earth-free straight-flow system, the positive bus-bar of this earth-free straight-flow system is Ry relative to the insulation resistance of the earth, described positive bus-bar is Cy relative to the distributed capacitance of the earth, the negative busbar of this earth-free straight-flow system is Rx relative to the insulation resistance of the earth, described negative busbar is Cx relative to the distributed capacitance of the earth, this circuit comprises resistor R1, resistor R2, resistor R0, resistor Rs, voltage sensor and signal generator, wherein: the first terminal of described resistor R1 is connected to described positive bus-bar, the first terminal of described resistor R2 is connected to described negative busbar, described voltage sensor has first input end, second input terminal and lead-out terminal, the first input end of described voltage sensor is sub and the second input terminal is all electrically isolated from one with described lead-out terminal, and the first input end sub-connection of described voltage sensor is to second terminal of described resistor R1, second input terminal of described voltage sensor is connected to second terminal of described resistor R2, the lead-out terminal of described voltage sensor is for exporting the voltage between described positive bus-bar and described negative busbar measured, the first terminal of described resistor R0 is connected to described negative busbar, second connecting terminals of described resistor R0 receives the first terminal of described resistor Rs, second connecting terminals of described resistor Rs receives the first terminal of described signal generator, second terminal ground of described signal generator, 3rd terminal of described signal generator controls for receiving the control signal that described signal generator produces signal, the signal that wherein said signal generator produces comprises direct current signal and AC signal.

2. circuit according to claim 1, wherein, described voltage sensor is Hall voltage sensor.

3. circuit according to claim 1, wherein, described resistor R1 and described resistor R2 is power resistor.

4., for the device that the insulation against ground of earth-free straight-flow system is monitored, this device comprises the circuit any one of claims 1 to 3 described in claim, and this device also comprises the first sample circuit and processor, wherein:

Described processor controls described signal generator and produces direct current signal;

Described first sample circuit is used for sampling to the DC voltage at described resistor Rs two ends under the control of described processor, and sampled result is fed back to described processor;

Described processor also for receiving the voltage between described positive bus-bar and described negative busbar that described voltage sensor collects, and calculates the resistance value of described insulation resistance Ry and described insulation resistance Rx and value in parallel thereof based on the described positive bus-bar that described voltage sensor collects with the sampled result of the voltage between described negative busbar and described first sample circuit.

5. device according to claim 4, wherein, this device also comprises the second sample circuit, and:

Described processor also produces AC signal for controlling described signal generator;

Described second sample circuit then for sampling to the alternating voltage at the second terminal place of the first terminal place of described resistor R0 and described resistor Rs and sampled result fed back to described processor under the control of described processor;

Described processor is also for calculating the parallel connection value of the capacitance of described distributed capacitance Cy and described distributed capacitance Cx based on the resistance value of described insulation resistance Rx and described insulation resistance Ry and the sampled result of value in parallel and described second sample circuit thereof.

6. the device according to claim 4 or 5, wherein, described device also comprises the first switch, second switch and the first resistor, wherein said first switch is connected between the earth and the ground of this device, described second switch is connected between the first terminal of described negative busbar and described first resistor, second terminal of described first resistor connects the ground of this device, and the break-make of described first switch and described second switch is controlled by described processor.

7. device according to claim 6, wherein, this device also comprises display, for the parallel connection value of the capacitance of the resistance value and value in parallel and distributed capacitance Cy and distributed capacitance Cx that show described insulation resistance Ry and the described insulation resistance Rx monitored.

8. device according to claim 6, wherein, described device also comprises the alarm unit be connected with described processor, and described processor is also reported to the police lower than indicating described alarm unit during threshold value for the parallel connection value at described insulation resistance Ry and described insulation resistance Rx.

9. device according to claim 6, wherein, described device also comprises the communication unit be connected with described processor, and this communication unit is used for receiving from described processor and exporting the parallel connection value of the resistance value of described insulation resistance Ry and described insulation resistance Rx and the capacitance of value in parallel and distributed capacitance Cy and distributed capacitance Cx thereof.

10., to the method that the insulation against ground of earth-free straight-flow system is monitored, the method is based on the circuit described in claim any one of claims 1 to 3, and the method comprises:

Control described signal generator and produce the first direct current signal;

Sampling is carried out to the DC voltage at described resistor Rs two ends and obtains the first sampled result;

Be the first voltage by described voltage sensor to the voltage collected between described positive bus-bar and described negative busbar of the voltage between described positive bus-bar and described negative busbar;

Control described signal generator and produce the second direct current signal;

Sampling is carried out to the DC voltage at described resistor Rs two ends and obtains the second sampled result;

Be the second voltage by described voltage sensor to the voltage collected between described positive bus-bar and described negative busbar of the voltage between described positive bus-bar and described negative busbar;

The resistance value of described insulation resistance Ry and described insulation resistance Rx and value in parallel thereof is calculated based on described first sampled result, the first voltage, the second sampled result and the second voltage.

11. methods according to claim 10, wherein, the DC voltage at described resistor Rs two ends is sampled and obtains the first sampled result and carry out sampling to the DC voltage at described resistor Rs two ends obtaining the second sampled result and comprising:

A () per interval t1 DC voltage to described resistor Rs two ends is sampled until sample N number of sampled value;

B () judges that whether first sampled value be equal with N number of sampled value;

If c () is equal, then N number of sampled value is required sampled result, if unequal, then returns step (a).

12. methods according to claim 10 or 11, wherein, after the resistance value calculating described insulation resistance Ry and described insulation resistance Rx based on described first sampled result, the first voltage, the second sampled result and the second voltage and value in parallel thereof, the method also comprises:

Control described signal generator and produce AC signal;

Sampling is carried out to the alternating voltage at the first terminal place of described resistor R0 and the second terminal place of described resistor Rs and obtains the first AC sampling voltage and the second AC sampling voltage;

The parallel connection value of the capacitance of described distributed capacitance Cy and distributed capacitance Cx is calculated based on the resistance value of described insulation resistance Rx and described insulation resistance Ry and value in parallel thereof and described first AC sampling voltage and the second AC sampling voltage.

13. methods according to claim 12, wherein, the method also comprises:

When the parallel connection value of described insulation resistance Ry and described insulation resistance Rx is reported to the police lower than during threshold value.