CN201184897Y - System for measuring earth network resistance and inductance using impact current - Google Patents

Abstract

The utility model relates to a system for measuring resistance and inductance of a ground grid by applying impact current, and aims to solve the problems of measurement of ground impedance, the resistance and the inductance when the ground grid is flowed by lightning current. The input of an impact current generator (B) is connected with the output of an isolation transformer (A), the input of the isolation transformer (A) is connected with an alternating current power supply, the output of the impact current generator (B) carries out the charge of a capacitor (I) through a silicon stack (C) and a protection resistor (D), a controllable silicon (G) controls the capacitor (I) to carry out the discharge of a test loop, a shunt resistor (F), an adjustable inductor (E) and an equivalent ground grid (H) are connected in a discharge loop of the capacitor (I) in series, a first voltage division resistor and a second voltage division resistor (M1, M2) which are connected in series are connected with the equivalent ground grid (I) in parallel. The shunt resistor (F) and the second voltage division resistor (M2) are connected with the input of an A/D converter (J), and the output of the A/D converter is connected with a microprocessor (K).

Description

The system of utilization impact current for measuring grounded screen electric resistance and inductance

Technical field:

The utility model is relevant with the measuring system and the method for the ground connection parameter of power system simulation when lightning current flows through earth mat.

Background technology:

In up-to-date measurement guide rule in 2006, regulation replaces the notion of stake resistance with impedance ground.This makes that the parameter notion of earthing device is more accurate, also for the electric system earthmeter new requirement proposed.We know that usually said stake resistance is not the pure resistance of earthing device, but contain reactive component at interior impedance ground, and it is divided into the power frequency impedance ground and impacts impedance ground.The impedance that the ground connection medium presented when power current loose stream to the earth is the power frequency impedance ground, and lightning current (dash current) flows through impedance that earthing device presents for impacting impedance ground.And the impedance that earthing device impact electric current is presented is different with power frequency impedance ground and direct current resistance.Present earth loop impedance test instrument generally can only be measured the power frequency impedance ground and the direct current resistance of earthing device, so development is necessary with impact current for measuring impedance ground system.

The utility model content:

It is strong that the purpose of this utility model provides a kind of antijamming capability, and the measuring accuracy height is measured the simple and practical utilization impact current for measuring grounded screen electric resistance and the system and method for inductance.

The utility model is achieved in that

The system of the utility model utilization impact current for measuring grounded screen electric resistance and inductance; the input of impulse current generator B is connected with the output of isolating transformer A; the input of isolating multiple pressure device A is connected with AC power; the output of impulse current generator B is dashed capacitor I through silicon stack C and protective resistance D; controllable silicon G control capacitance I discharges to test loop; shunt resistance F, controllable impedance E and equivalent grounding network H are series in the discharge loop of capacitor I, first, second divider resistance M of series connection ₁, M ₂I is in parallel with equivalent grounding network.The shunt resistance F and the second divider resistance M ₂Be connected with the input of A/D converter J, the output of A/D converter is connected with microprocessor K.

Impulse current generator B is 6 voltage-multiplying circuits, by six capacitor C of polyphone ₁-C ₆6 diode D with parallel connection ₁-D ₆Form.

First, second divider resistance M ₁, M ₂Resistance adjustable in 2-20K Ω scope, shunt resistance F and first, second divider resistance M ₁, M ₂Be noninductive resistor.

Inductance E is a controllable impedance.

The utility model uses the measurement electric current of dash current as the simulation thunder and lightning, and calculates the ground connection parameter with the newer computing method of a cover, and this method can be separated resistance and reactive component, and energy measurement goes out the impact impedance ground that other method can not be measured.Measurement mechanism is simple, is convenient to operation, and antijamming capability is strong, and the measuring accuracy height has higher engineering practical value.

Description of drawings:

Fig. 1 is circuit theory diagrams of the present utility model.

Fig. 2 is the circuit theory diagrams of impulse current generator.

Embodiment:

Hardware of the present utility model mainly is impulse current generator and data acquisition dress device.The design philosophy of impulse current generator is: under casing insulated enough situations, miniaturization as far as possible was easy to carry.According to the requirement of actual engineering, impulse current generator is designed to Adjustable Output Voltage, maximum voltage 5kV, the impulse current waveform that wave head is steeper.The impulse current generator power supply adopts the 220V communication power supply, (main frame electric capacity is 10 μ F to 1～10KV, 10～200 μ F through voltage doubling rectifing circuit, can and meet bigger external charge electric capacity L) capacitor I charging, after finishing, charging cuts off the electricity supply, control controllable silicon G conducting, capacitor I is discharged to discharge loop.Impulse current generator can obtain needed impulse current waveform by regulating divider resistance and inductance.Each components and parts among Fig. 1 of the present utility model are as follows:

A: isolating transformer

The B:6 voltage-multiplying circuit.6 of electric capacity (CJ41-2 630V-4 μ F), 6 of diodes;

C: silicon stack (2DL 1A10kV)

D: protective resistance (RX20-200W)

E: telefault (coil diameter 7cm, 7 circles)

F: shunt resistance (RX20-200W)

SCR control switch (discharge of control charging capacitor)

G: transwitch

H: equivalent grounding network

I: electric capacity (charging capacitor 5kV, 50uF)

J:10bitAD sampling thief (ADS805E)

K:586EX microprocessor (ELANSC520-133) carries out sequential logic control, data processing, and program is calculated (seeing the computed in software part)

L: external charge electric capacity

M ₁, M ₂: divider resistance (RX20-200W)

Measure electric current and take from 220V and exchange, self-isolation transformer A is transferred to B, amplifies after the C discharge through 6 times in B, and D is a loop protection resistance.E is a controllable impedance, and after charging capacitor I charging was finished, transwitch G controlled discharge.F is a shunt resistance, and H is an equivalent grounding network, and AD converter is through F, M ₂On adopt respectively electric current, voltage analog signal and be converted to digital signal after send into microprocessor K and carry out data analysis and calculate.

Collect voltage, current data by data acquisition unit and be sent to computing machine later on and handle, computer software should be able to calculate resistance, inductance and the impact impedance ground of grounding body.

For the calculating of impacting impedance ground, according to the definition of impacting impedance ground, the ratio of maximum voltage value and lowest high-current value is and impacts the impedance ground value.This method adopts frequency spectrum analysis method, and in frequency domain, the ratio of voltage and voltage dashes the impedance ground value under the frequency domain for this reason under the same frequency.Select it to ask its mean value under stable then.

How the resistance of impedance ground and reactive component being separated, draw the resistance and the inductance of grounding body, is the problem of shock measurement method primary study, and specific algorithm of the present utility model is as follows:

(1) computing machine reads in the binary voltage U signal of A/D converter output, and the electric current I signal data is converted to decimal data U (t through converting unit _i) and I (t _i), i is the ranking value of the number of data points of collection, the number of data points n of collection is determined by the sample frequency of A/D converter, and n=fT, wherein f is a sample frequency, T is the sampling period,

(2) the rapid fourier change unit is U (t _i) and I (t _i) be transformed to the frequency in the frequency domain and the corresponding relation U (ω of amplitude _i) and I (ω _i), ω is a fundamental frequency, $\mathrm{\ω}=\frac{f}{n},$

(3) the impedance computation unit calculates impact impedance $Z\left({\mathrm{\ω}}_i\right)=\frac{U\left({\mathrm{\ω}}_i\right)}{I\left({\mathrm{\ω}}_i\right)}$ i＝1，2，...n

(4) computing unit calculates one group of R (ω in the frequency domain _i) and L (ω _i)

$R\left({\mathrm{\ω}}_i\right)=\sqrt{(i^2{Z}_i^2-Z_{i+1}^2)/(i^2-1)}$

$L\left({\mathrm{\ω}}_i\right)=\sqrt{(Z_{i+1}^2-Z_i^2)/(i^2-1){\mathrm{\ω}}^2},$ i＝1，2，...n-1

(5) computing unit calculates R, L

$R=\frac{\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}R\left({\mathrm{\ω}}_i\right)}{n-1};$ $L=\frac{\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}L\left({\mathrm{\ω}}_i\right)}{n-1},$

Binary data is voltage U signal, the electric current I signal that A/D converter collects from divider resistance, shunt resistance.Computer software becomes decimal data U (t with binary U and I data after conversion _i), I (t _i), wherein i is 1MHz for the ranking value of the number of data points of collection as sample frequency, a power frequency period 0.02s is total to such an extent that gather 2 * 10 so ⁴Individual data point, n=2 * 10 so ⁴U (t _i), I (t _i) be time and amplitude corresponding relation in the time domain.After fast fourier transform, obtain frequency and amplitude corresponding relation U (ω in voltage, the electric current frequency domain _i), I (ω _i).Impact impedance $Z\left({\mathrm{\ω}}_i\right)=\frac{U\left({\mathrm{\ω}}_i\right)}{I\left({\mathrm{\ω}}_i\right)}.$ Calculate R (ω by formula _i) and L (ω _i) after, ask its mean value R, L.

Claims (4)

1, the system of utilization impact current for measuring grounded screen electric resistance and inductance; the input that it is characterized in that impulse current generator (B) is connected with the output of isolating transformer (A); the input of isolating multiple pressure device (A) is connected with AC power; the output of impulse current generator (B) is dashed electric capacity (I) through silicon stack (C) and protective resistance (D); controllable silicon (G) control capacitance (I) is discharged to test loop; shunt resistance (F), controllable impedance (E) and equivalent grounding network (H) are series in the discharge loop of electric capacity (I), first, second divider resistance (M of series connection ₁, M ₂) in parallel with equivalent grounding network (I), the shunt resistance (F) and the second divider resistance (M ₂) be connected with the input of A/D converter (J), the output of A/D converter is connected with microprocessor (K).

2, system according to claim 1 is characterized in that impulse current generator (B) is 6 voltage-multiplying circuits, by six capacitor C of polyphone ₁-C ₆6 diode D with parallel connection ₁-D ₆Form.

3, system according to claim 1 is characterized in that first, second divider resistance ((M ₁, M ₂) resistance adjustable in 2-20K Ω scope, shunt resistance (F) and first, second divider resistance (M ₁, M ₂) be noninductive resistor.

4, system according to claim 1 is characterized in that inductance (E) is a controllable impedance.

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