CN201311463Y - Resistive current tester of high-current zinc oxide arrester - Google Patents

Abstract

The utility model relates to a resistive current tester of a high-current zinc oxide arrester, comprising a digital signal processor. A voltage sensor, a filtering and amplifying circuit and an A/D converter are sequentially cascaded to form a voltage channel, and a voltage signal is led from a PT secondary side by a voltage test line, processed and sent to the digital signal processor; a current transmitter, a filtering and amplifying circuit and an A/D converter are sequentially cascaded to form a current channel, and a current signal is taken out from the lower end of the arrester, processed and sent to the digital signal processor. The utility model has the advantages of high test precision, convenient use, safety and reliability.

Description

Resistive current tester for great current zinc oxide lightning arrester

Technical field

The utility model relates to the electric parameters testing instrument, particularly relates to measuring the isoparametric instrument of zinc oxide lightning arrester block property current active power under no cut-off condition.

Background technology

According to the 21st regulation of standard GB 50150-2006, topmost three the measurement projects of Zinc-Oxide Arrester (hereinafter to be referred as lightning arrester) are: 1, insulation resistance; 2, power frequency reference voltage and persistent current; 3, the leakage current under DC reference voltage and 0.75 DC reference voltage under the 1mA, wherein the 1, the 3rd, after having a power failure lightning arrester pulled down and measure, because its test labour intensity is too big, time-consuming oversize, be again to have a power failure to measure, so the measuring period all very long (being generally 3～6 years/time) that each department require.

Chinese patent literature CN87206423U discloses a kind of need not under the power-off condition, and a resistance in its testing tool directly and the lightning recorder parallel connection can be finished the live testing of lightning arrester.Defectives such as it exists the parameter testing error bigger, and precision is low.Chinese patent literature has also disclosed a kind of " multi-functional arrester resistance current detector " (CN2104453U), can measure loop total current peak value, effective value, current in resistance property peak value, effective value, active loss, six parameters such as alternating voltage, and have an oscillograph interface, and design concept system adopts discharge counter valve block resistance and both end voltage to carry out following calculation, and detector is directly and in the two ends of discharge counter during measurement.Its line design is comparatively complicated, and measuring accuracy still remains to be improved.

The utility model content

The purpose of this utility model provides a kind of measuring accuracy height, resistive current tester for great current zinc oxide lightning arrester easy to use, safe.

This novel purpose is achieved in that a kind of resistive current tester for great current zinc oxide lightning arrester, comprises digital signal processor; By voltage sensor, filter amplification circuit, AD converter in turn cascade form voltage channel, through voltage tester line extraction voltage signal, be delivered to digital signal processor from the PT secondary side after treatment; By current transducer, filter amplification circuit, AD converter in turn cascade form current channel, take out current signal from lightning arrester lower end discharge counter and be delivered to digital signal processor after treatment.

Above-mentioned voltage sensor is made up of the KT20/1.6V that is wound with 10 circle coils, and this coil has sealed in 120K Ω/1w resistance; The voltage 57.74V of PT secondary side directly inputs to voltage sensor through this coil, and voltage signal is become the AC5V signal; Described current transducer is used to handle 1 circle of 2-20mA and 0～2mA current signal and the KT20/1.6V of 10 circle coils forms by being wound with, and current signal is converted into AC0V～1.6V after treatment; Described filter amplification circuit mainly is made up of the AD620 amplifier; Also has high speed analog multiplexer AD7502; The current signal of the voltage signal of above-mentioned voltage sensor output and current transducer output all inputs to high speed analog multiplexer AD7502, again output after two AD620 amplifiers amplify respectively.

The interchange input impedance of above-mentioned voltage sensor is more than or equal to 120K Ω, and the interchange input impedance of current transducer is less than 5 Ω.

2 pin of above-mentioned voltage sensor KT20/1.6V are connected to 8 pin of AD7502, and 2 pin of current transducer KT20/1.6V are connected to 5,6,7 pin of AD7502; 12 pin of AD7502,4 pin are connected to 1 pin, 3 pin of AD620 respectively, and 6 pin of AD620 are connected to 3 pin of another AD620, the external output signal of 6 pin of another AD620.

Be in series with the 0.2A fuse respectively on the above-mentioned voltage tester line.

Above-mentioned AD converter is 10 bit parallel chip C196KC; Also has the very color LCD of the TFT that is connected with digital signal processor.

Compared with prior art, this novel beneficial effect is:

1, can be under the situation that need not have a power failure, primary connection just carries out the total current of three-phase oxidation zinc lightning arrester fast, current in resistance property, the first-harmonic current in resistance property, 3,5,7 subharmonic current in resistance property, capacity current, the phasing degree, the isoparametric test of fundamental active power, in time the discovering device built-in electrical insulation makes moist, valve block is aging and dangerous defective such as filth, avoids it to influence the transmission line of electricity security of operation because of apparatus overheat even Explosion of on Arrester accident that above-mentioned reason causes.

2, measurement range is the highest can reach 20mA, satisfies the test request of the variety classes test product that country variant produces, and the measuring accuracy that built-in alternating current rheology send device can satisfy tens μ A can satisfy the measuring accuracy of 20mA again.

3, high-speed figure sampling system, fourier transform technique, software filtering, Software Anti-interference has significantly reduced hardware spending, makes entire equipment reliable and stable, and failure rate is extremely low.

4, by to the high-speed sampling of two signals of electric current and voltage, the two phase relation of Accurate Analysis is separated the principal ingredient capacity current in the total current, thereby is measured current in resistance property, and important parameter such as active power.

Description of drawings

Fig. 1 is an electric theory diagram of the present utility model;

Fig. 2 is the test wiring diagram;

Fig. 3 is the voltage tester wiring schematic diagram;

Fig. 4 is the circuit diagram of voltage sensor shown in Figure 1 and the very big circuit of filtering, current transducer and filter amplification circuit;

Fig. 5 is that digital signal processor DSP shown in Figure 1 carries out digital filtering and arrester resistance current Program for Calculation process flow diagram to voltage and current signal.

Embodiment

Fig. 1 illustrates, and resistive current tester for great current zinc oxide lightning arrester comprises, digital signal processor; By voltage sensor, filter amplification circuit, AD converter in turn cascade form voltage channel, through voltage tester line 7,8 extraction voltage signals, be delivered to digital signal processor from the PT secondary side after treatment; By current transducer, filter amplification circuit, AD converter in turn cascade form current channel, lightning arrester 3,4, the 5 lower end discharge counter 3a on A, B, the C triple-phase line, 4a, 5a take out current signal and are delivered to digital signal processor after treatment.Is the model of digital signal processor? described AD converter is 10 bit parallel chip C196KC; Also has the very color LCD of the TFT that is connected with digital signal processor.Referring to Fig. 4, voltage sensor is made up of the KT20/1.6V that is wound with 10 circle coils, and this coil has sealed in 120K Ω/1w resistance; The voltage 57.74V of PT secondary side directly inputs to voltage sensor through this coil, and voltage signal is become the AC5V signal; Described current transducer is used to handle 1 circle of 2-20mA and 0～2mA current signal and the KT20/1.6V of 10 circle coils forms by being wound with, and current signal is converted into AC0V～1.6V after treatment; Described filter amplification circuit mainly is made up of the AD620 amplifier; Also has high speed analog multiplexer AD7502; The current signal of the voltage signal of above-mentioned voltage sensor output and current transducer output all inputs to high speed analog multiplexer AD7502, again output after two AD620 amplifiers amplify respectively.

Among Fig. 4, sensor T1 (being KT20/1.6V) is a voltage channel, the voltage 57.74V of PT secondary side directly inputs to T1, specifically around sending out be: T1 is around 10 circles, seal in 120k Ω/1W resistance simultaneously, minimum 120k is brought up in its input impedance, and T1 becomes the AC5V signal with signal and inputs to AD7502, exports to AD converter by 6 pin again after the AD620 processing and amplifying.T2 (being KT20/1.6V) is a current channel, specifically be: 1 circle and 10 circles around sending out, 1 circle is handled 2～20mA current signal, 10 circles are handled 0～2mA current signal, so the input impedance of its current channel is very low, only are the resistance of lead, the number of turn is selected by programmed control, automatically switch, current signal is converted into AC0V～1.6V through transmitter, passes through AD7502 equally, devices such as AD620, export to AD converter, AD7502 is that simulation transforms switch at a high speed, because the application of high-speed analog switch, make the public passage of voltage and current, this kind design can guarantee the consistance of voltage channel and current channel greatly, avoids by the inconsistent error of bringing of hardware.

The interchange input impedance of voltage sensor is more than or equal to 120K Ω, and the interchange input impedance of current transducer is less than 5 Ω.2 pin of voltage sensor KT20/1.6V are connected to 8 pin of AD7502, and 2 pin of current transducer KT20/1.6V are connected to 5,6,7 pin of AD7502; 12 pin of AD7502,4 pin are connected to 1 pin, 3 pin of AD620 respectively, and 6 pin of AD620 are connected to 3 pin of another AD620, the external output signal of 6 pin of another AD620.

Referring to Fig. 3, be in series with 0.2 A fuse 7a, 8a on the voltage tester line 7,8 respectively.

Fuse plays a protective role to PT (voltage transformer (VT)) when the measurement circuit short circuit.This kind design can be avoided the PT short circuit well.Current signal is taken from Zinc-Oxide Arrester lower end discharge counter, because the current signal sending-end impedance of instrument is very little, the discharge counter shunting is very little, can ignore, and electric current almost all passes through from instrument internal.

Referring to Fig. 5, the current in resistance property parameter test method that a kind of testing current in resistance property instrument is used, carry out according to the following steps in turn:

Show master menu behind the start-up routine;

According to 2～20mA and 0～2mA, two class input current signals, select by selecting acknowledgement key to select one;

Carry out the high-speed figure sampling according to actual waveform with 10KHz/s speed;

Carry out digital low-pass filtering;

According to formula 1: $I=\sqrt{\frac{1}{T}{\&Integral;}_0^{\mathrm{<figure-callout\; id="2"\; label="T\; i"\; filenames="Y20082014116100082.png,Y20082014116100084.png"\; state="\{\{state\}\}">T</figure-callout>}}{i}^{}{}^2\mathrm{dt}}$ Obtain the electric current and voltage effective value;

According to formula 2:

Isolate the amplitude and the phasing degree of first-harmonic and 3-5-7 subharmonic;

Obtain parameters such as current in resistance property according to Ir=Ix*cos Φ;

Show and printing;

Finish.

The theory diagram of this instrument is as shown in Figure 1: voltage sensor and the complete electromagnetic isolation of instrument internal circuit are not influenced by instrument with guard signal sampling end PT; the interchange input impedance of this signal end is very high simultaneously; this instruments design is more than or equal to 120k Ω; so the PT output current is very little, can not influence PT work.Current transducer also adopts isolation method, and model is KT20/1.6, and it exchanges input impedance less than 5 Ω, and its current handling capability minimum is a microampere order, is tens milliamperes to the maximum, and precision is 0.1 grade.Instrument adopts DSP technology and FFT technology (mathematical model is seen formula 1 and formula 2 respectively).

$I=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}^2\mathrm{dt}}$

. formula 1

Formula 2

So the hardware of amplification filtering unit need not special processing, the amplifier model is AD620.10 bit parallel chips are adopted in the AD conversion, and model is C196KC, and slewing rate is fast.The signal Processing major part is finished by software, significantly reduces hardware spending.Microprocessor adopts INTEL16 position high-speed chip.Display adopts the very color LCD of Mitsubishi 640 * 480 resolution TFT, makes things convenient for the output of data and waveform, the actual waveform of shows signal in the time of measurement parameter.

The core of this instrument is to have designed voltage sensor and current transducer, the two paths of signals at scene is delivered to signal processing unit, send into microprocessor by the ad converter after the simple amplification filtering, fully by controlling and calculate, at last by LCD and mini-printer output by software program.Wherein the gordian technique of Cai Yonging has: 1, Applied Digital signal Processing (DSP) technology, and sampling rate is 10kHz/s; 2, adopted Fourier transform (FFT) technology, extract various frequency contents and phase angle difference in the signal, the application of software engineering has been avoided by hardware circuit having improved stable testing with the data influence that the variation of frequency, temperature, time and humidity causes; 3, penalty method effectively overcomes because Zinc-Oxide Arrester spatial interference between phase and phase.Improve the accuracy of data; 4, the electric isolation technology of small-signal guarantees the safety of equipment under test.

Claims (6)

1. A resistive current tester for a high-current zinc oxide arrester, characterized by: comprising, digital signal processor; A voltage channel is composed of a voltage sensor, a filter amplifier circuit, and an AD converter cascaded in sequence, and the voltage signal is drawn from the secondary side of the PT through the voltage test line (7, 8), and sent to the digital signal processor after processing; The current channel is composed of a current transmitter, a filter amplifier circuit, and an AD converter cascaded in sequence, and the current signal is taken out from the discharge counter (3a, 4a, 5a) at the lower end of the arrester (3, 4, 5) and sent to a digital signal after processing processor. 2. According to claim 1, the high-current zinc oxide arrester resistive current tester is characterized in that: the voltage sensor is composed of KT20/1.6V wound with a 10-turn coil, and the coil is connected in series with 120KΩ/1w resistance; the voltage 57.74V on the secondary side of the PT is directly input to the voltage sensor through the coil, and the voltage signal is changed into an AC5V signal; KT20/1.6V composed of 10-turn and 10-turn coils, the current signal is converted into ACOV～1.6V after processing; the filter amplifier circuit is mainly composed of AD620 amplifier; it also has a high-speed analog conversion switch AD7502; the voltage signal output by the above voltage sensor And the current signal output by the current transducer is input to the high-speed analog conversion switch AD7502, and then output after being amplified by two AD620 amplifiers. 3. The resistive current tester for high-current zinc oxide arrester according to claim 2, characterized in that: the AC input impedance of the voltage sensor is greater than or equal to 120KΩ, and the AC input impedance of the current transmitter is less than 5Ω. 4. According to claim 3, the high-current zinc oxide arrester resistive current tester is characterized in that: the 2 pins of the voltage sensor KT20/1.6V are connected to the 8 pins of the AD7502, and the current transmitter KT20/1.6V Pin 2 is connected to pin 5, 6, and 7 of AD7502; pin 12 and pin 4 of AD7502 are respectively connected to pin 1 and pin 3 of AD620; pin 6 of AD620 is connected to pin 3 of another AD620; pin 6 of another AD620 External output signal. 5. According to any one of claims 1 to 4, the high-current zinc oxide arrester resistive current tester is characterized in that: 0.2A fuses (7a, 8a) are respectively connected in series on the voltage test lines (7, 8) ). 6. The resistive current tester for high-current zinc oxide arrester according to claim 5, characterized in that: the AD converter is a 10-bit parallel chip C196KC; it also has a TFT true-color liquid crystal display connected with a digital signal processor.

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