CN103063926A - Test method and test device for low-voltage power line narrowband carrier access impedance - Google Patents

Abstract

The invention discloses a test method for a low-voltage power line narrowband carrier access impedance and a test device for the low-voltage power line narrowband carrier access impedance. The test device for the low-voltage power line narrowband carrier access impedance comprises a signal transmitting device, a signal receiving device and a signal processing device, wherein the signal processing device is connected with the signal receiving device, and the signal transmitting device and the signal receiving device are respectively mounted on a power line. The test method, corresponding to the test device, for the low-voltage power line narrowband carrier access impedance includes that the test device is mounted on the power line; the test device and a wire are calibrated; the test device transmits signals to the power line; and the test device receives data, fed back from the power line in a coupling mode, about access impedance, forms a frequency curve of the access impedance in a fitting mode based on the data, and then displays the frequency curve. The test method for the low-voltage power line narrowband carrier access impedance and the test device for the low-voltage power line narrowband carrier access impedance overcome the defect that only a single frequency point can be measured when the impedance is measured through a resonance method, and have universality. In addition, according to the test method for the low-voltage power line narrowband carrier access impedance and the test device for the low-voltage power line narrowband carrier access impedance, a high-speed acquisition card is used for discretizing collected analog signals so as to facilitate calculation of large amounts of data, and therefore alternating-current signal acquisition is realized.

Description

A test method and test device for low-voltage power line narrowband carrier access impedance

technical field

The invention belongs to the field of power systems, and in particular relates to a test method and a test device for the access impedance of a low-voltage power line narrowband carrier.

Background technique

Power line carrier communication refers to a communication method that uses power lines to transmit data, voice and other signals. Utilizing the existing power line resources for communication can not only meet the communication needs, but also solve the wiring difficulties, and the infrastructure investment and daily maintenance costs are low. Therefore, the power line carrier communication technology has high economy, convenience and practicability. However, the original intention of power line design is to complete power distribution rather than data transmission, so for data communication, its channel characteristics are very unsatisfactory. One of the main factors affecting the reliable communication of the power line is the access impedance characteristic of the power line. The access impedance of the power line carrier communication channel refers to the equivalent impedance of the low-voltage power line at the driving point of the signal sending device and the signal receiving device. The impedance characteristics of the power line carrier communication channel change with the time, frequency and signal access position, especially the 30-500kHz narrow-band carrier frequency band, which changes drastically and is obviously affected by the grid structure, lines, and user appliances. The stability parameter, which directly affects the coupling efficiency of the carrier signal and the transmission performance of the signal, is an important parameter of the power line communication channel. Therefore, it is of great significance to study and actually test the access impedance of the power line carrier to improve the performance of the power line carrier communication system. On the other hand, compared with weak current communication cables, power lines are asymmetrical lines and high-voltage strong current networks. It is difficult to actually test the impedance of power lines. The existing access impedance testing methods at home and abroad mainly include the double current probe method. , Ratio method, resonance method, and voltammetry. The ratio method can only measure the modulus value of the impedance, but cannot obtain the phase information of the impedance; the resonance method can only measure the impedance value of a single frequency point, and cannot obtain the impedance characteristics of the continuous spectrum; the circuit structure of the voltammetry method is complex, and the required There are many test instruments, the actual on-site measurement is difficult, and the required instruments are expensive, which is suitable for laboratory measurement; although the double current probe method can measure the modulus and phase information of the low-voltage power line impedance, but due to the frequency resolution of the network analyzer used Low, the accuracy of the measured results is not very high, and the on-site test is not convenient.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a test method and testing device for the access impedance of the narrowband carrier of the low-voltage power line, which can not only test the modulus value of the access impedance of the narrowband carrier of the power line, but also obtain the phase information of the impedance, and simultaneously measure The result is relatively accurate, and the method of testing impedance that can be easily applied to field measurement is of great significance for the further development and research of power line communication.

A kind of test method of low-voltage power line narrowband carrier access impedance provided by the present invention, its improvement is that, described test method comprises the following steps:

(1) Set up test equipment on the power line;

(2) Calibrate the test device and leads;

(3) The test device sends a signal to the power line;

(4) The test device receives the data of the access impedance coupled back from the power line, fits the frequency curve of the access impedance according to the data, and displays it.

Wherein, the wire described in step (2) refers to the wire connected between the test device and the power line;

Carry out calibration to described testing device and wire, its step comprises;

①Connect the test device to the two ends of the power line or short-circuit the two ends of the wire to obtain the voltage U _m1 at both ends of the impedance Z ₁ and the voltage U _n1 at both ends of the impedance Z ₂ , and the relationship between the impedance Z ₂ and the capacitance and The expression of impedance Z ₁ composed of fixed value resistors:

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ;</span>$

②A fixed resistor Z _D is connected to the two ends of the test device connected to the power line to obtain the voltage U _m2 at both ends of the impedance Z ₁ and the voltage U _n2 at both ends of the impedance Z ₂ , and obtain:

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ;</span>$

③ Obtained from steps ① and ②:

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}}{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ;</span>$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span>$

④ According to the values of impedance _Z1 and _Z2 obtained in step ③, determine the values of the parameters of the resistance and capacitance components of the signal transmitting device of the test device.

Wherein, the step of the testing device in step (3) sending a signal to the power line is;

1) The signal transmitting device of the test device generates a signal to the power amplifier;

2) The power amplifier amplifies the signal and transmits it to the coupler;

3) The coupler couples the signal to the power line.

Among them, step (4) includes the following steps:

A. The signal acquisition device collects the data on the power line through the isolation device, and transmits the data to the signal processing device;

B. The signal processing device obtains the real part, the imaginary part and the frequency of the access impedance according to the data, fits it into a frequency curve of the access impedance, and displays it.

The present invention provides a test device for a low-voltage power line narrowband carrier access impedance based on another purpose. The improvement is that the test device includes a signal sending device, a signal receiving device and a signal processing device; the signal processing device and The signal receiving device is connected;

The signal sending device and the signal receiving device are respectively installed on the power line.

Wherein, the signal sending device and the signal receiving device are integrated on one circuit board.

Wherein, the signal transmitting device includes a signal transmitting device, a power amplifier and a coupler connected in sequence; the output end of the coupler is connected to the power line.

Wherein, the signal receiving device includes a connected isolation device and a signal acquisition device;

The input end of the isolation device is connected to the power line;

The output end of the signal acquisition device is connected with the signal processing device.

Wherein, the signal acquisition device includes a high-speed data acquisition card.

Wherein, the signal processing device includes a computer; the computer has a signal processing function, adopts the U/I algorithm to obtain the modulus value, real part and imaginary part of the impedance, determines the relationship between the real part, the imaginary part and the frequency, and simulates composite curve.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The signal acquisition device of the present invention uses a high-speed acquisition card to discretize the collected analog signals so as to facilitate the calculation of a large amount of data and solve the problem of AC signal acquisition. This method is safe and has high calculation efficiency. The used The high-speed acquisition card improves the resolution of the acquisition signal device, and the measured frequency band range is wider (30KHZ~500KHZ), while the frequency resolution of the network analyzer used by the usual dual current probe method is lower, and the narrowband bandwidth range measured is (300KHZ~500KHZ), so that the measured results can more accurately reflect the actual situation.

(2) The U/I algorithm adopted in the present invention can not only measure the modulus value of impedance, but also test impedance, the relationship between real part and imaginary part and frequency, and their relationship with frequency can be fitted into a curve, which can The relationship between phase and frequency is calculated according to the obtained data, and the measured data has continuity with respect to the frequency, which overcomes the disadvantage that the resonance method can only measure a single frequency point for impedance measurement, and is universal.

(3) The calibration principle adopted in the present invention can eliminate the influence of the impedance generated by the internal components of the test device and the impedance generated by the external connection line on the impedance of the power line, making the test result more accurate.

(4) The present invention makes the carrier signal transmitter, power amplifier, narrowband coupler, high-speed acquisition card, and isolation device into the form of a circuit board, integrates five devices into one, and uniformly supplies power, which is easy to carry and is conducive to on-site test.

(5) The present invention utilizes the short-circuit method and the fixed-value resistor connection method to calibrate the internal components and external wiring of the test circuit to reduce test errors.

(6) The present invention proposes a new test method for low-voltage power line impedance. The method is based on the principle of voltammetry (U/I), adopts advanced high-speed signal acquisition technology, and is controlled by a computer to collect narrow-band carrier voltage signals in power lines. Calculate the access impedance modulus and phase, imaginary part, and real part information of the measured point through the computer-specific software algorithm, and fit the access impedance-frequency curve, which not only improves the frequency resolution of the test device, but also makes the measured The accuracy of the data is higher, and the measurement device is simple and easy to carry out field testing. In addition, a calibration method for low-voltage power line impedance testing is proposed, which is used to calibrate the influence of the test circuit internal and external wires on the power line access impedance.

Description of drawings

Fig. 1 is a circuit diagram of a test device connected to a low-voltage power line provided by the present invention.

Fig. 2 is a diagram of signal acquisition and processing provided by the present invention.

Fig. 3 is a calibration principle diagram provided by the present invention.

Fig. 4 is a structural diagram of a test device connected to a power line provided by the present invention.

Fig. 5 is a test result diagram of the real part, the imaginary part and the modulus value of the low-voltage power line access impedance provided by the present invention.

Fig. 6 is a graph of the phase angle-frequency test result of the access impedance of the low-voltage power line provided by the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

A test device for a low-voltage power line narrowband carrier access impedance provided in this embodiment includes a signal sending device, a signal receiving device, and a signal processing device; the signal processing device is connected to the signal receiving device;

The signal sending device and the signal receiving device are respectively connected to the power line through wires, as shown in FIG. 4 , and its circuit diagram is shown in FIG. 1 .

The signal sending device and the signal receiving device are integrated on one circuit board. The signal sending device includes a signal sending device, a power amplifier and a coupler connected in sequence; the output end of the coupler is connected with the power line. The signal receiving device includes an isolating device and a signal collecting device connected, the input end of the isolating device is connected to the power line, and the output end of the signal collecting device is connected to the signal processing device.

The signal acquisition device of this embodiment includes a high-speed data acquisition card. Since the measured signal is the access impedance of the power line, the measured signal is an AC signal, and the voltage and current cannot be directly measured with an AC voltmeter or an AC ammeter. The signals measured by them are effective values, which cannot meet the instantaneous value requirements we need. , and due to the large number of measured points, it is very inconvenient to calculate the impedance. The collected signal is an analog signal. We use a high-speed acquisition card to maintain and sample the collected analog signal, and transfer the obtained discrete signal to the PC. computer, using computer-specific software to write calculation programs, which not only solves the demand for instantaneous values, but also solves the difficulty that the data is too large and difficult to calculate. Moreover, this embodiment uses a high-speed acquisition card (RBW≈30HZ) to solve the problem of inaccurate test results caused by low frequency resolution. The size of the resolution bandwidth (RBW) can determine whether two adjacent signals can be separated, and the acquisition The lower the resolution bandwidth of the card, the higher the frequency resolution, but too high a frequency resolution will lead to a long acquisition and calculation time, so choosing a suitable RBW of the acquisition card can ensure the accuracy of the acquired signal. Accuracy, but also to ensure the speed of signal acquisition and calculation. The general method such as the double current probe method to test the impedance is that the RBW of the device used to collect the signal is relatively high;

The signal processing device of the present embodiment includes a computer; the computer has a signal processing function, adopts the U/I algorithm to obtain the modulus value, the real part and the imaginary part of the impedance, determines the relationship between the real part, the imaginary part and the frequency, and simulates composite curve.

Correspondingly, a method for testing the access impedance of a low-voltage power line narrowband carrier proposed in this embodiment includes the following steps:

(1) Set up test equipment on the power line;

Wherein, the test device is connected to the power line through a wire;

(2) Calibrate the test device;

There are two reasons for the calibration. (1) Since the impedance of the power line itself is very small, especially when the low-voltage section is connected to many household loads, the impedance of the power line channel on the low-voltage side of the distribution network is only a few ohms to a dozen ohms. Test the circuit The components in the test may make the test error larger; (2) Since the method of the present invention is aimed at the field test, the test line sometimes needs to be connected to a long wire or cable when it is connected to the power line. Since the signal we inject into the power line is high High-frequency signal, and the inductive reactance generated by high-frequency signal on the wire or cable is relatively large, this part of the inductive reactance will have a greater impact on the impedance of the measured power line, so the connected external wires or cables must be disconnected before testing. Calibrated to make the test results more accurate.

Calibrating the test device refers to calibrating the internal components of the test device and sometimes connecting a long wire or cable when the test line is connected to the power line,

In order to achieve the purpose of calibration, we need to determine the values of some circuit component parameters in the test device. As shown in Figure 3, the primary side of the transformer is connected to the AC signal source, its secondary side is connected to the wire, and the secondary side is connected to the The circuit is the circuit in the middle part of the coupling device and the high-speed acquisition card in Figure 1, and the principles used to determine the values of these parameters are as follows:;

①Short-circuit both ends of L and N to obtain U _m1 and U _n1 , Z ₂ is a fixed-value resistor, so that the impedance Z ₁ of the part composed of a capacitor and a fixed-value resistor can be obtained:

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ;</span>$

In the formula, U _m1 is the voltage at both ends of Z ₁ ; U _n1 is the voltage at both ends of Z ₂ ; Z ₂ is the unknown impedance; Z ₁ is the impedance of the components of capacitor and fixed value resistor;

②Connect a fixed resistor Z _D at both ends of L and N, and U _m2 and U _n2 can be obtained in the same way as (1), and get:

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ;</span>$

In the formula, U _m2 is the voltage at both ends of Z ₁ ; U _n2 is the voltage at both ends of Z ₂ ; Z ₂ is the unknown impedance; Z ₁ is the impedance of the capacitor and the fixed value resistor; Z _D is the known fixed value resistor;

From the above two steps can be obtained:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}}{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>$ ${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Z"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">Z</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span>$

In this way, the values and _{Z 2 of} the fixed-value resistor R 1 and the capacitor C in the impedance Z ₁ required in the test circuit are obtained. When conducting on-site testing, we must first short-circuit the signal line of the test device and then connect it to the fixed value resistor Z _D for calibration. When an external wire or cable is required, it is necessary to connect the external wire (cable) to the signal line and then perform the above operations , to eliminate the influence of the impedance on the test results caused by the internal components of the circuit and the external wires when the high-frequency signal flows.

(3) The test device sends a signal to the power line, and the steps include;

1) The signal transmitting device of the test device generates a signal to the power amplifier;

2) The power amplifier amplifies the signal and transmits it to the coupler;

3) The coupler couples the signal to the power line.

(4) The test device receives the data of the access impedance coupled back from the power line, fits the frequency curve of the access impedance according to the data, and displays it. The entire test process is shown in Figure 2. in,

Step (4) specifically includes the following steps:

A. The isolation device isolates the signal acquisition device from the power line of the power grid;

B. The signal acquisition device collects the data coupled back on the power line, and transmits the data to the signal processing device;

C. The signal processing device obtains the real part, the imaginary part and the frequency of the access impedance according to the data, fits it into a frequency curve of the access impedance, and displays it.

As shown in Figure 1, the voltage signals of point A and point B are collected through the high-speed acquisition card, and sent to the PC through the USB interface, and the calculation program is used to calculate the value of the impedance by using the software in the PC. The principle used is as follows:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;C</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

In the formula, U _A is the voltage signal at point A; U is the voltage at both ends of L and N; I is the current flowing through the test circuit; R ₁ is the fixed value resistor; ω is the angular frequency of the input signal; C is the fixed value capacitor ;

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; u</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="j"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">j</figure-callout></span>}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;\; C</span>}}<span\; class="notranslate">\; ;</span>$

In the formula, Z is the impedance of the power line to be measured;

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="j"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">j</figure-callout></span>}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;\; C</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&angle;</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&angle;</span><span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="j"\; filenames="HDA00002616615800031.png"\; state="\{\{state\}\}">j</figure-callout></span>}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;\; C</span>}}$

In the formula, _R2 is the fixed-value resistance in the signal transmitting device; U _B is the voltage signal at point B;

Using the above calculation formula, we can calculate the relationship between the modulus value, imaginary part, real part, phase and frequency of the impedance, and it is continuous, and the calculated data is fitted into a curve to analyze the change law of the impedance.

The schematic diagram of the test results of this embodiment is shown in Figure 5 and Figure 6. Figure 5 shows the impedance modulus, imaginary part, and real part of the access impedance of the test, and can use the real part and the imaginary part according to the test results obtained. According to the measured data, the relationship between phase and frequency is obtained, as shown in Figure 6. The invention can analyze the capacitive reactance and inductive reactance of the power line through the data of the impedance modulus, the imaginary part and the real part of the access impedance, and can monitor whether the power line is faulty.

The U/I calculation software used can simultaneously display the modulus value, real part and imaginary part information of the impedance. Because the power line distributes inductance and capacitance during high-frequency signal transmission, and the power line load itself and the resonance between the load and the power line appear in a certain frequency range, so it is necessary to understand the imaginary part of the impedance and the phase of the impedance. with frequency changes.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (10)

1. a test method of low-voltage power line narrowband carrier access impedance, is characterized in that, described test method comprises the steps: (1) Set up test equipment on the power line; (2) Calibrate the test device and leads; (3) The test device sends a signal to the power line; (4) The test device receives the data of the access impedance coupled back from the power line, fits the frequency curve of the access impedance according to the data, and displays it. 2. The testing method according to claim 1, characterized in that, the wire in step (2) refers to the wire connected between the testing device and the power line; Carry out calibration to described testing device and wire, its step comprises; ①Connect the test device to the two ends of the power line or short-circuit the two ends of the wire to obtain the voltage U _m1 at both ends of the impedance Z ₁ and the voltage U _n1 at both ends of the impedance Z ₂ , and the relationship between the impedance Z ₂ and the capacitance and The expression of impedance Z ₁ composed of fixed value resistors: $\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ;</span>$ ②A fixed resistor Z _D is connected to the two ends of the test device connected to the power line to obtain the voltage U _m2 at both ends of the impedance Z ₁ and the voltage U _n2 at both ends of the impedance Z ₂ , and obtain: $\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; ;</span>$ ③ Obtained from steps ① and ②: ${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}}}{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ;</span>$ ${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span>$ ④ According to the values of impedance _Z1 and _Z2 obtained in step ③, determine the values of the parameters of the resistance and capacitance components of the signal transmitting device of the test device. 3. The testing method according to claim 1, characterized in that, in step (3), the step of the testing device sending a signal to the power line is; 1) The signal transmitting device of the test device generates a signal to the power amplifier; 2) The power amplifier amplifies the signal and transmits it to the coupler; 3) The coupler couples the signal to the power line. 4. The test method according to claim 1, wherein step (4) comprises the following steps: A. The signal acquisition device collects the data on the power line through the isolation device, and transmits the data to the signal processing device; B. The signal processing device obtains the real part, the imaginary part and the frequency of the access impedance according to the data, fits it into a frequency curve of the access impedance, and displays it. 5. A test device for low-voltage power line narrowband carrier access impedance, characterized in that, the test device includes a signal sending device, a signal receiving device and a signal processing device; the signal processing device is connected to the signal receiving device; The signal sending device and the signal receiving device are respectively installed on the power line. 6. The test device according to claim 5, wherein the signal sending device and the signal receiving device are integrated on a circuit board. 7. The test device according to claim 5, wherein the signal transmitting device comprises a signal transmitting device, a power amplifier and a coupler connected in sequence; the output end of the coupler is connected to the power line. 8. The test device according to claim 5, wherein the signal receiving device comprises connected isolation devices and signal acquisition devices; The input end of the isolation device is connected to the power line; The output end of the signal acquisition device is connected with the signal processing device. 9. The test device according to claim 5, wherein the signal acquisition device comprises a high-speed data acquisition card. 10. testing device as claimed in claim 5 or 8, is characterized in that, described signal processing device comprises computer; Described computer has signal processing function, adopts U/I algorithm to draw the modulus value, real part and imaginary part of impedance Department, determine the relationship between the real part, imaginary part and frequency, and fit a curve.

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