CN105929284A - Wireless tester and testing method for live-line measuring zinc oxide arrester - Google Patents

Abstract

The invention relates to a wireless tester and testing method for live-line measuring a zinc oxide arrester. The wireless tester comprises a transmitting unit and a receiving unit, wherein the transmitting unit acquires three-phase voltage signals of a power grid, calculates voltage amplitude and phase angle of the power grid, and transmits the voltage amplitude and phase angle information to the receiving unit through a wired or wireless means, the receiving unit acquires full leakage current and receives the voltage amplitude and phase angle information, of the power grid, sent by the transmitting unit, compares the full-leakage current phase angle with the received voltage amplitude of the power grid to obtain the phase difference, and calculates the resistive leakage current of the arrester to determine the performance of the arrester. Three-phase resistive leakage current can be simultaneously and synchronously measured in a short period of time, and the measurement precision is greatly improved.

Description

Wireless tester and detection method for live measurement of zinc oxide arrester

technical field

The invention relates to on-site debugging and detection of power system equipment, in particular to a wireless tester and a detection method for live-measuring zinc oxide arresters, which are mainly used for judging the performance of arresters and belong to the field of electric power applications.

Background technique

In recent years, there have been many new and renovated lines in various regions. As a high-reliability lightning protection unit, zinc oxide arresters play an important role in the safe operation of power systems. The current instruments for testing the performance of zinc oxide arresters are cumbersome in the field test process, and the wiring requires the cooperation of other departments. The interphase interference is relatively large, which affects and damages the instrument and seriously deviates the test data, which cannot provide true and effective test results.

Contents of the invention

Aiming at the above-mentioned problems in the prior art, the present invention provides a wireless tester for live measurement of zinc oxide arresters, which solves the problems of cumbersome wiring and relatively large phase-to-phase interference in the prior art during the test.

Another object of the present invention is to provide a detection method for a wireless tester for measuring zinc oxide surge arresters when charged.

Technical scheme of the present invention is as follows:

The wireless tester includes a sending unit and a receiving unit; the sending unit completes the acquisition of three-phase voltage signals of the power grid, and calculates the voltage amplitude and phase angle of the power grid at the same time, and transmits them to the receiving unit through wired or wireless methods, and the receiving unit completes the acquisition of the full leakage current and receiving The grid voltage amplitude and phase angle information sent by the sending unit, and compare the phase angle of the full leakage current with the received grid voltage phase angle to obtain the phase difference. And obtain the resistive leakage current of the arrester through calculation; the sending The voltage loop of the unit is connected to the secondary voltage terminal of the bus bar, the voltage transformer sends the signal to the amplifier circuit, the AD conversion circuit converts the received signal from the amplifier circuit, the converted data is sent to the CPU, and the CPU sends the operation result signal to Receiving unit; the receiving unit adopts a current transformer to measure the current signal at the lower end of the lightning arrester, and the current transformer sends the three-phase full leakage current signal to the amplifying circuit and the AD conversion circuit, and the data converted by the AD conversion circuit are processed by the CPU, to get the final resistive leakage current.

The current transformer feed-through current transformer.

The AD conversion circuit is a high-speed AD conversion circuit.

The wireless transmission uses a micro-power wireless data transmission module, which uses FEC combined with radio frequency IC CC1020, and the wireless communication module transmits through a 433M public frequency.

Both the sending unit and the receiving unit are equipped with AC interference suppressors.

In the receiving unit, the CPU is connected with an embedded industrial computer, and the embedded industrial computer is connected with a liquid crystal display and a mouse and keyboard input end.

The detection method includes the following steps: the sending unit first sends a synchronization command, and after the receiving unit receives the command, both sides simultaneously collect and FFT process, and then the sending unit sends the processed data to the receiving unit, and the receiving unit summarizes the data on both sides, Compensation is made according to the delay on both sides, and then the data is finally processed and the result is sent to the display.

The advantages and effects of the present invention are as follows:

The sending and receiving units communicate in a wireless or wired manner, and both units have data processing functions. The sending unit collects the voltage signal of the power grid, and obtains the phase and amplitude signals of the voltage through data processing. The receiving unit collects the full leakage current signal of the arrester and analyzes it with the voltage signal of the sending unit to obtain the phase difference between the grid voltage and the full leakage current of the arrester. Finally, by obtaining the resistive current component of the full leakage current, the performance of the arrester can be judged. The three-phase resistive leakage current can be measured simultaneously and synchronously in a short period of time, and the measurement accuracy is greatly improved.

It supports wired and wireless measurement methods and can simultaneously measure and display three-phase voltage and current, shorten test time, and facilitate the removal of phase-to-phase interference characteristic test equipment to meet site needs.

Description of drawings

Figure 1 is a schematic diagram of two sine wave signals.

Figure 2 is a vector diagram of the current signal.

Fig. 3 is a schematic structural diagram of the principle of the present invention.

Fig. 4 is a schematic diagram of the principle of the sending unit of the present invention.

Fig. 5 is a schematic diagram of the principle of the receiving unit of the present invention.

Fig. 6 is a schematic diagram of field wireless test wiring of the present invention.

Fig. 7 is a schematic diagram of field wired test wiring of the present invention.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments with reference to the accompanying drawings.

Example

As shown in the figure, the wireless tester includes a sending unit and a receiving unit; the sending unit completes the acquisition of the three-phase voltage signal of the power grid, and calculates the voltage amplitude and phase angle of the power grid at the same time, and transmits it to the receiving unit through wired or wireless means, and the receiving unit completes the whole process. Leakage current acquisition and receiving grid voltage amplitude and phase angle information sent by the sending unit, and comparing the full leakage current phase angle with the received grid voltage phase angle to obtain the phase difference. And through calculation to obtain the arrester resistive leakage current The voltage loop of the sending unit is connected to the secondary voltage terminal of the bus bar, the voltage transformer sends the signal to the amplifying circuit, the high-speed AD conversion circuit converts the received amplifying circuit signal, and the converted data is sent to the CPU, CPU Send the calculation result signal to the receiving unit; the receiving unit uses a feed-through current transformer to measure the current signal at the lower end of the arrester, and the feed-through current transformer sends the three-phase full leakage current signal to the amplifier circuit and high-speed AD conversion circuit , the data converted by the high-speed AD conversion circuit is processed by the CPU to obtain the final resistive leakage current.

Both the sending unit and the receiving unit are equipped with AC interference suppressors.

In the receiving unit, the CPU is connected with an embedded industrial computer, and the embedded industrial computer is connected with a liquid crystal display and a mouse and keyboard input end.

1. Measuring principle:

Consider two sine waves with the same frequency but different initial phases, as shown in Figure 1:

Signal 1 corresponds to the current signal, and signal 2 corresponds to the voltage signal. Their mathematical expressions are:

V＝Bsin(ωt) (2)

Expand the current signal:

The corresponding instantaneous value of the resistive current is:

Resistive current peak value:

The instantaneous value of the capacitive current is:

The peak capacitive current is:

If the voltage signal V is used as the phase reference, we can see the size of the resistive current and the capacitive current more clearly from the vector diagram, as shown in Figure 2.

As long as A, If the two parameters are measured accurately, the value of the resistive current can be completely calculated.

2. Design of zinc oxide detection method

The overall structure of the zinc oxide detection unit is shown in Figure 3.

It is mainly composed of sending unit and receiving unit. The sending unit mainly completes the acquisition of three-phase voltage signals of the power grid, and calculates the voltage amplitude and phase angle of the power grid at the same time, and transmits them to the receiving unit through wired or wireless methods. The receiving unit mainly completes the collection of full leakage current and receives the grid voltage amplitude sent by the sending unit. , Phase angle information, and compare the phase angle of the full leakage current with the phase angle of the received grid voltage to obtain the phase difference. And obtain the resistive leakage current of the arrester through calculation.

2.1 Measurement of grid voltage

The voltage loop of the sending unit is connected to the secondary voltage terminal of the bus bar, and sent to the amplifier circuit, high-speed hold, and sampling circuit through the voltage transformer for AD conversion. The converted data is mathematically operated by the CPU, and finally the result is sent to the receiving unit. . A high-speed AD conversion circuit ensures simultaneous measurement of three-phase voltage signals. The principle block diagram is shown in Figure 4.

2.2 Measurement of total leakage current

The receiving unit uses a through-type transformer to measure the current signal at the lower end of the arrester. The transformer has better shielding measures, otherwise, the external electromagnetic field interference during on-site measurement will make the instrument unable to work normally. The three-phase full leakage current signal is sent to the amplifier circuit and high-speed AD conversion circuit. The converted data is subjected to mathematical operations by the CPU, and phase calculation is performed with the three-phase voltage signal to obtain the final resistive leakage current. The principle block diagram is shown in Figure 5.

2.3 Measurement of phase angle difference

The measurement of the phase angle difference between the voltage signal and the current signal is the key to the measurement accuracy. From formula (5), we can see that the peak resistive leakage current is proportional to The peak value change of resistive current caused by phase angle measurement error is:

According to field experience, the phase angle difference of zinc oxide in normal operation is generally 83°. When the phase angle changes by 0.1° within this angle difference range, the resistive current change value is 1.42%. If the phase angle difference range is close to 90° , the resulting measurement error will be greater, therefore, the measurement of the phase angle difference must be accurate and reliable.

Simultaneous measurement of three-phase voltages is guaranteed by high-speed and high-precision AD converters. The measurement of three-phase currents is also very similar. Simultaneous measurement between voltage and current is guaranteed by wired or wireless transmission. The fundamental wave signal in the power system is 50Hz, the period is 20ms, and the corresponding phase is 360°. When it is required that the phase angle difference does not exceed 0.2°, and the measurement startup pulse error between voltage and current cannot exceed 11us, we use a series of hardware technologies such as high-speed AD conversion devices, high-speed data transmission, and large-scale programmable logic devices to eliminate delays Software technology that is relatively large and prone to accumulated errors ensures accurate measurement of phase angles between three-phase voltages, three-phase currents, and currents and voltages.

The wiring method of the test line is shown in Figure 6 and 7. First connect the ground wire of the sending unit and the receiving unit, then connect a 3-core current test line, and finally connect a 4-core voltage test line. The method of connecting the current test line, first, according to the current size, connect the current test line to the "0-2mA" or ">2mA" range file on the host end (>2mA file standard configuration is 2-10mA), and then connect the other end to the counter the upper end. The method of connecting the voltage test line is also to connect the PT voltage transmitter end first, and then connect the PT secondary test end.

The wireless module selects micro-power wireless data transmission module, adopts high-efficiency FEC forward error correction technology combined with high-performance wireless radio frequency IC CC1020, and combines with high-speed microprocessor. The wireless communication module has the characteristics of strong anti-interference ability, fully transparent transmission, small size, low power consumption and long transmission distance, and does not require any coding technology when used. The wireless module is through the 433M public frequency, no frequency band application is required.

The sending unit first sends a synchronization command. After the receiving unit receives the command, both sides collect and FFT processing at the same time, and then the sending unit sends the processed data to the receiving unit. The receiving unit summarizes the data on both sides and compensates according to the delay on both sides. The data is then subjected to final processing and the results are sent to the display.

In the no-voltage mode, the software simulates the phase angle difference between voltage and current without using a PT transmitter.

Claims (7)

1. The wireless tester for measuring zinc oxide surge arresters with electricity is characterized in that it includes a sending unit and a receiving unit; the sending unit completes the acquisition of three-phase voltage signals of the power grid, and calculates the voltage amplitude and phase angle of the power grid at the same time, and transmits them to the receiving unit through wired or wireless methods. The receiving unit completes the collection of the full leakage current and receives the grid voltage amplitude and phase angle information sent by the sending unit, and compares the phase angle of the full leakage current with the phase angle of the received grid voltage to obtain the phase difference. And obtain the resistive leakage current of the arrester through calculation; the voltage loop of the sending unit is connected to the secondary voltage terminal of the bus bar, the voltage transformer sends the signal to the amplifying circuit, and the AD conversion circuit converts the received amplifying circuit signal, converting The final data is sent to the CPU, and the CPU sends the calculation result signal to the receiving unit; the receiving unit uses a current transformer to measure the current signal at the lower end of the arrester, and the current transformer sends the three-phase full leakage current signal to the amplifying circuit, AD conversion circuit, the data converted by the AD conversion circuit is processed by the CPU to obtain the final resistive leakage current. 2. The wireless tester for live measurement of zinc oxide arrester according to claim 1, characterized in that said current transformer is a feed-through current transformer. 3. The wireless tester for live measuring zinc oxide arrester according to claim 1, characterized in that said AD conversion circuit is a high-speed AD conversion circuit. 4. The wireless tester for live measurement zinc oxide arrester according to claim 1, characterized in that the wireless transmission selects a micropower wireless data transmission module, adopts FEC in combination with radio frequency IC CC1020, and the wireless communication module passes 433M public frequency transmission. 5. The wireless tester for measuring zinc oxide surge arresters with live charging according to claim 1, characterized in that said sending unit and receiving unit are both provided with AC interference suppressors. 6. The wireless tester for live measurement zinc oxide arrester according to claim 1, characterized in that in the receiving unit, the CPU is connected with an embedded industrial computer, and the embedded industrial computer is connected with a liquid crystal display and a mouse and keyboard input. 7. The detection method of the wireless tester for live measurement zinc oxide arrester according to claim 1, characterized in that it includes the following steps: the sending unit first sends a synchronization command, and after the receiving unit receives the command, both sides simultaneously collect and FFT Processing, and then the sending unit sends the processed data to the receiving unit, and the receiving unit summarizes the data on both sides, compensates according to the delay on both sides, and then performs final processing on the data, and sends the result to the display.