A kind of insulation resistance detector and detection method thereof being applied to IT system
Technical field
The invention belongs to insulation resistance detection field, relate to the insulation resistance being applied to IT system and detect, especially a kind of insulation resistance detector and detection method thereof being applied to IT system.
Background technology
Traditional insulation resistance detection device, mainly contains bridge method, current sensor method of testing, self-adaptation impulse method.Wherein, bridge method is only suitable for direct current IT system, and measuring accuracy is lower, interference rejection ability is poor, narrow range, bridge method and current sensor detection method all need from system under test (SUT) power taking signal, and measuring accuracy and scope are limited by system under test (SUT), and self-adaptation pulse method has testing blind zone, the measuring accuracy of lower frequency range IT system can be affected or cannot detect at all.Above method or direct current IT system can only be applied to, or blind area is existed to the IT system of AC ripple, namely lower to system frequency range, can not accurately test out insulating resistance value.In addition, traditional insulation detector, the electric pressure of test is limited, often can not measure the insulation resistance of higher electric pressure system.
The patent document of analogous technical fields is found through retrieval:
A kind of DC electrical system insulation resistance detects and earth protective device (CN103701092A); comprise detection signal source module; multiple signal coupler; drain transformer; multiple residual current sensor; multiple phase-sensitive rectifier, multiple insulation resistance detector, multiple protection output unit and capacitance.Detection signal source module after testing signal bus is connected with signal coupler; Detection signal source module connects the positive and negative main bus-bar of DC electrical system through drain transformer; Residual current sensor connects phase-sensitive rectifier input end; the control end of phase-sensitive rectifier is connected with detection signal bus; phase-sensitive rectifier is with insulation resistance detector and protect output unit to be connected, and insulation resistance detector is connected with detection signal bus respectively with protection output unit.The present invention has reliable selectivity and accuracy to the insulation reduction of protection domain and earth fault.
Comparative analysis, above published patented technology and known public technology technology all required for protection from present patent application is different, and the technique effect produced also exists difference.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art part, provide a kind of structure simple, detect accurately, quickness and high efficiency, the reliable and stable insulation resistance detector being applied to IT system and detection method thereof.
The present invention solves its technical matters and takes following technical scheme to realize:
A kind of insulation resistance detector being applied to IT system, it is characterized in that: comprise controllable voltage generator, follower, low-pass filter, controlled two sampling holders, differential amplifier, MCU and sampling network, controllable voltage generator is communicated with sampling microwave network, this sampling microwave network is connected follower, low-pass filter, controlled two sampling holders, differential amplifier and MCU successively, this MCU connects controllable voltage generator, low-pass filter and controlled two sampling holders respectively by data line, and MCU is also connected with I/O terminal.
And described controllable voltage generator comprises gauge tap k21 and k22, control to export Uo by gauge tap k21 and k22, obtain ± pulse signal of Un or+Un or-Un d. c. voltage signal.
And described sampling microwave network comprises the inductor and resistor R1, R2, R3 of connecting successively, shares the voltage of AC high-voltage power supply; R1, R2 are the resistor of equivalence, and R3 is small resistor.
And described inductor is by being being composed in series of multiple inductor.
And, the concrete structure of described controlled two sampling holders, comprise three gate-controlled switch device k31, k32 and k33 controlled by MCU, memory cell C1 and C2, and follower B1 and follower B2, described derailing switch k31, memory cell C1 and follower B1 form one group of sampling hold circuit, and described derailing switch k32, memory cell C2 and follower B2 form another group sampling hold circuit, the gauge tap k33 in parallel of the B2 in this sampling hold circuit; These two groups of sampling hold circuits are in parallel, respectively corresponding output voltage signal u1 and u2.
And described I/O terminal comprises display, setting device and switching value circuit.
And, adopt low-frequency pulse probe method:
(1) produce voltage signal, MCU controls the voltage signal of controllable voltage generator generation ± Un with the signal of a low frequency;
(2) sample of signal, this signal is by the sampling microwave network sampling of L1, R1, R2 series connection;
For AC system, signal is generally greater than 50HZ, and L1 shares most of alternating voltage, and now, it is break-even by inductor that the voltage signal of ± Un is less than this voltage signal of 1HZ, and by resistor R1, R2, R3 dividing potential drop;
(3) signal is by low-pass filter, and MCU controls the cutoff frequency of low-pass filter, make ± voltage signal of Un is break-even to be passed through, the harassing and wrecking signal of filtering based on mains frequency;
(4) signal is by controlled pair of sampling holder, C1 for controlled pair of sampling holder sampling holder remembers the t1 moment Un of positive pulse Un generation and the coefficient voltage u1 of network system generation, the common effect u2 that the t2 moment-Un of the C2 memory negative pulse-Un generation of sampling holder and network system produce;
(5) signal is by differential amplifier, the output Uo=K* (u1-u2) of differential amplifier, and wherein K is the enlargement factor of differential amplifier,
This Uo has eliminated the effect of AC or DC network system, and Uo is proportional to the electric current I n that sample resistance R1, R2, R3 flow through;
(6) obtain Re result: by calculating I
nif, Rn=I
n, the series value of Rn insulation resistance Re and R1, R2, R3, obtains testing result Re=Rn-R1-R2-R3.
(7) report to the police or instruction: after MCU calculates insulating resistance value, when Re is less than the alarming value threshold of setting, exported by display or switching value circuit and indicated.
And, described step (3) in, the frequency of pulse producer is lower, and the cutoff frequency of low-pass filter is also along with reduction.
And, adopt direct voltage method:
(1) produce voltage signal, MCU clamp-pulse generator only produces the voltage signal of positive Un;
(2) sample of signal, this signal is by the sampling microwave network sampling of L1, R1, R2 series connection;
(3) signal is by low-pass filter, and MCU controls low-pass filter and produces alap cutoff frequency, and Un is that direct current signal can pass through in free of losses;
(4) signal is by controlled pair of sampling holder, and coefficient voltage u1, the gauge tap K33 of t1 moment Un and network system generation that the C1 for controlled pair of sampling holder sampling holder remembers positive pulse Un generation close and make u2=0;
(5) signal is by differential amplifier, the output Uo=K* (u1-u2) of differential amplifier, and wherein K is the enlargement factor of differential amplifier,
This Uo has eliminated the effect of AC or DC network system, and Uo is proportional to the electric current I n that sample resistance R1, R2, R3 flow through;
(6) obtain Re result: by calculating I
nif, Rn=I
n, the series value of Rn insulation resistance Re and R1, R2, R3, obtains testing result Re=Rn-R1-R2-R3;
(7) report to the police or instruction: carry out reporting to the police and indicating after MCU calculates insulating resistance value, when Re is less than the alarming value threshold of setting, exported by display or switching value circuit and indicated.
Advantage of the present invention and good effect are:
The present invention has wide range of applications, effective, can be applicable to the ac grid system of the pulsation of extremely low frequency, also the circuit of low-frequency pulse probe method and direct voltage method can be applied to respectively, can be widened by the choice for use of two kinds of method of testings can the frequency range of examining system, can also be applied in more high-tension AC system.
Accompanying drawing explanation
Fig. 1 is insulation resistance detector theory structure block diagram;
Fig. 2 is controllable voltage generator;
Fig. 3 is controlled two sampling holders.
Embodiment
Below in conjunction with accompanying drawing, also by specific embodiment, the invention will be further described, and following examples are descriptive, are not determinate, can not limit protection scope of the present invention with this.
A kind of insulation resistance detector being applied to IT system, comprise controllable voltage generator A1, follower A2, low-pass filter A3, controlled two sampling holder A4, differential amplifier A5, MCUA6 and sampling network A7, controllable voltage generator is communicated with sampling microwave network, the signal that this controllable voltage generator is produced is applied on sampling microwave network, sampling microwave network is connected follower successively, low-pass filter, controlled two sampling holders, differential amplifier and MCU, this MCU connects controllable voltage generator respectively by data line, low-pass filter and controlled two sampling holders, and, MCU is also connected with display, arrange, the circuit such as switching value,
Shown in accompanying drawing 1, insulation resistance detects and will obtain the insulating resistance value Re of AC and/or DC system to the equivalence of the earth in fact exactly, Re1 or Re2 namely shown in accompanying drawing.
Figure 2 shows that controllable voltage generator concrete structure see attached, export Uo by gauge tap k21 and k22, can obtain ± pulse signal of Un or+Un or-Un d. c. voltage signal.
See the attached concrete structure that Figure 3 shows that controlled two sampling holders, comprise three gate-controlled switch device k31, k32 and k33 controlled by MCU, memory cell C1 and C2, and follower B1 and follower B2, described derailing switch k31, memory cell C1 and follower B1 form one group of sampling hold circuit, described derailing switch k32, memory cell C2 and follower B2 form another group sampling hold circuit, and these two groups of sampling hold circuits are in parallel, respectively corresponding output voltage signal u1 and u2; MCU by gauge tap k31 and k32, thus obtains not voltage signal u1 and u2 in the same time on same circuit.A B2 gauge tap k33 controlled by MCU in parallel in another group sampling hold circuit, when k33 closes, u2 is 0.
Illustrating of critical piece:
A1 controllable voltage generator, the frequency that can control by MCU control generation and positive negative pulse stuffing, also only can produce positive or negative DC voltage;
A2 follower, holding signal is undistorted;
The low-pass filter that A3 low-pass filter adopts filter cutoff frequency controlled, this low pass filter cutoff frequency should be less than the interchange ac power system frequency of 1/10;
Two sampling holders that A4 is controlled, MCU control A4 obtains the signal u1 that t1 moment positive pulse acts on system, then obtains the signal u2 of t2 moment negative pulse effect;
A5 differential amplifier, obtains the signal delta u of the difference correlation connection of u1 and u2 through differential amplifier;
The AD channel reception Δ u of A6MCU samples; MCU controls the circuit such as display, setting, switching value simultaneously, once Re is less than warning threshold, export instruction by indicating circuit or switching value output circuit, setting device can be that keyboard etc. can operation setting alarm door threshold value.
A7 sampling microwave network, comprises inductor L1, resistor R1, R2, R3, and inductor shares most of voltage of AC high-voltage power supply, and inductance value should be enough large, and L1 can be the series connection of multiple inductor; R1, R2 shown in the present embodiment are the resistor of equivalence, and share most of DC voltage, R1, R2 also can adopt multiple resistant series; R3 is small resistor, and Main Function is sampled signal.
Inductor L1 is effective for ac grid system, and the inductance value strengthening L1 can be applicable to the network system of higher alternating voltage.
The detection method of above-mentioned detecting device, obtain insulation resistance Re as shown in Figure 1, can have two kinds of methods below:
Method one low-frequency pulse probe method
(1) produce voltage signal, MCU controls the voltage signal of controllable voltage generator generation ± Un with the signal of a low frequency;
(2) sample of signal, this signal is by the sampling microwave network sampling of L1, R1, R2 series connection; For AC system, signal is generally greater than 50HZ, and L1 shares most of alternating voltage, and now, it is break-even by inductor that the voltage signal of ± Un is less than this voltage signal of 1HZ, by resistor R1, R2, R3 dividing potential drop;
(3) signal is by low-pass filter, and MCU controls the cutoff frequency of low-pass filter, and fundamental purpose to allow the voltage signal of controllable voltage generator generation ± Un is break-even to be passed through, and the harassing and wrecking signal of filtering based on mains frequency;
The frequency of pulse producer is lower, and the cutoff frequency of low-pass filter is also along with reduction;
(4) signal is by controlled pair of sampling holder, the coefficient voltage u1 that the t1 moment Un occurred for C1 " memory " the positive pulse Un of controlled pair of sampling holder sampling holder and network system produce, the common effect u2 that the t2 moment-Un of C2 " memory " negative pulse-Un generation of sampling holder and network system produce;
(5) signal passes through differential amplifier, the output Uo=K* (u1-u2) of differential amplifier, wherein K is the enlargement factor of differential amplifier, and this Uo has eliminated the effect of AC or DC network system, and Uo is proportional to the electric current I n that sample resistance R1, R2, R3 flow through;
(6) obtain Re result: by calculating
if
the series value of Rn insulation resistance Re and R1, R2, R3, obtains testing result Re=Rn-R1-R2-R3.
When Re is less than the alarming value threshold of setting, indicated by display or output switch parameter.
Method two direct voltage method
MCU clamp-pulse generator only produces the voltage signal of positive Un;
MCU controls low-pass filter and produces alap cutoff frequency, and Un is that direct current signal can pass through in free of losses;
The K switch 33 that MCU controls controlled pair of sampling holder closes, and makes u2=0;
Other are with method one, obtain testing result Re=Rn-R1-R2-R3.
Method one is applicable to most of occasion, is not suitable for the system of the low-frequency pulse frequency close to its own transmission, such as, be less than the system of 50HZ;
Method two is applicable to pure AC system, comprises frequency system low especially, such as, be less than the system of 50HZ, but is not suitable for the network system of DC component.
Although disclose embodiments of the invention and accompanying drawing for the purpose of illustration, but it will be appreciated by those skilled in the art that: in the spirit and scope not departing from the present invention and claims, various replacement, change and amendment are all possible, therefore, scope of the present invention is not limited to the content disclosed in embodiment and accompanying drawing.