Wireless load vector tester

Abstract

The present invention relates to a wireless load vector tester for the field of power measurement. It includes a voltage reference and a measuring host, and wireless communication is adopted between the two. The voltage reference and the measuring host are each equipped with a power supply, and synchronous instructions are used to realize the synchronous measurement and calculation of the voltage, current frequency, amplitude, phase and other electrical parameters of different measuring points based on the voltage reference. The measuring host can not only work independently and complete the measurement and calculation of various electrical parameters of three-phase voltage and three-phase current signals; it can also perform multiple separate measurements with the voltage reference as a reference, save data, and directly display all input measurement results on a display in a vector diagram after synthesizing and calculating them with the voltage reference, so as to perform PT phase core and load vector test. It is a convenient and fast handheld instrument suitable for intelligent substations, capable of measuring the amplitude and phase of signals between multiple different locations, performing load vector test, and directly displaying hexagonal diagrams.

Description

Technical Field

[0001] The invention relates to a wireless load vector tester used in the field of electric power measurement. Background Art

[0002] When new substation equipment is put into operation or equipment with modified current secondary circuits resumes power supply, it is necessary to perform a load vector test, that is, to measure the effective value of the three-phase load current and the phase relative to the reference voltage and determine the phase sequence to detect the correctness of the secondary current and voltage circuits, thereby ensuring the correct protection operation. In the test of conventional substations, the voltage and current analog quantities are all located behind the same protection device screen, which can be easily completed through a three-phase phase volt-ampere meter. However, in smart substations, there is no analog input of voltage and current behind the protection screen. The analog quantity of voltage is located on the bus voltage merging unit, and the analog quantity of current is located on each interval merging unit. The two are several meters or even tens of meters apart. Therefore, the test with load vector is a relatively difficult problem. In the conventional main transformer differential protection, it is also necessary to use the high voltage voltage as the reference, and measure the amplitude and phase of the current on the high, medium and low sides at the same time, so as to distinguish the secondary circuit wiring.

[0003] At present, the mainstream digital phase volt-ampere meters in China all adopt the method of one host and multiple inputs, which is only applicable to traditional substations with voltage and current analog quantities on the same screen. Research on long-distance phase measurement technology either uses GPS signal synchronization or uses a dedicated synchronization pulse line. Using GPS signal synchronization requires complex hardware and high cost; using a dedicated synchronization pulse line requires laying a dedicated cable, which is inconvenient to use. Therefore, there is no convenient and fast handheld instrument in China that is suitable for smart substations, can measure the amplitude and phase of signals between multiple different locations, perform load vector testing, and directly display hexagonal diagrams. Summary of the invention

[0004] In order to solve the above-mentioned situation, the present invention provides a wireless load vector tester. The wireless load vector tester includes a voltage reference and a measuring host, and wireless communication is adopted between the two. The voltage reference and the measuring host each have a power supply, and synchronous instructions are used to realize the synchronous measurement and calculation of electrical parameters such as the frequency, amplitude, and phase of the voltage and current at different measurement points based on the voltage reference. The measuring host can not only work independently and complete the measurement and calculation of various electrical parameters of three-phase voltage and three-phase current signals; it can also use the voltage reference as a reference to perform multiple separate measurements, save data, and after all input measurement results are synthesized and calculated with the voltage reference, they are unified in a vector diagram and directly displayed on the display, thereby performing PT phase core and load vector testing.

[0005] The voltage reference includes a voltage measurement circuit, a display, a processor, a clock module, a serial wireless communication module and a power supply circuit. The voltage signal is connected to the voltage measurement circuit through the input port for filtering, shaping, amplification and other processing; the output signal of the voltage measurement circuit is connected to the processor; the processor is connected to the display for displaying the measurement information; the clock module provides a system clock and is connected to the processor for the processor to control the start of each measurement signal; the serial wireless communication module is connected to the processor for communication between the voltage reference and the measurement host.

[0006] The measuring host includes a voltage measuring circuit, a current measuring circuit, a display, a processor, a memory, a clock module, a serial wireless communication module and a power supply circuit. The voltage and current signals are connected to the corresponding measuring circuit through the input port for filtering, shaping, amplification and other processing; the output signal of the measuring circuit is connected to the processor; the processor is connected to the display for displaying the measurement information; the memory is used to save each individual measurement result; the clock module provides a system clock and is connected to the processor for the processor to control the start of each measurement signal; the serial wireless communication module is connected to the processor for communication between the measuring host and the voltage reference.

[0007] When the tester of the present invention measures:

[0008] Before the measurement host starts the measurement, it first sends a synchronization command to the voltage reference through the serial wireless transceiver module, and records the time when the measurement host clock is sent. When the voltage reference receives the synchronization command, it also records the voltage reference clock time. After the voltage reference is received, it replies to the measurement host with a synchronization response command, which carries the receiving and sending clocks of the voltage reference. When the measurement host receives the synchronization response command, it records the measurement host receiving clock time. Using these four clock times, the clock offset and transmission delay of the measurement host and the voltage reference can be calculated. According to the clock offset, the clock of the measurement host is adjusted to synchronize with the clock of the voltage reference. According to the transmission delay, the next measurement start time is set. The measurement host sends a start measurement instruction to the voltage reference, and the measurement host and the voltage reference start the measurement synchronously at the start time. After the measurement is completed, the measurement host reads the voltage reference measurement result through the serial wireless communication module, calculates the relationship between the electrical parameters or signals such as the amplitude and phase of each channel between the voltage reference and the measurement host, and outputs the result to the display for display. Each measurement result can be saved in the memory, and multiple results can be directly displayed on the display in a unified vector diagram after being synthesized and calculated with the voltage reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The specific contents of the present invention are further explained below in conjunction with the accompanying drawings and embodiments:

[0010] Figure 1 : Schematic diagram of the overall structure of this embodiment;

[0011] Figure 2 : Schematic diagram of the voltage reference structure of this embodiment;

[0012] Figure 3 : Schematic diagram of the structure of the measurement host in this embodiment;

[0013] Figure 4 : Schematic diagram of measurement synchronization in this embodiment. DETAILED DESCRIPTION

[0014] Reference Figure 1 This embodiment includes a voltage reference 1 and a measuring host 6; wherein the voltage reference includes a voltage input terminal 3, a display 2, a transceiver antenna 4 and a power switch 5; wherein the measuring host includes a voltage input terminal 8, a current input terminal 9, a display 7, a transceiver antenna 10 and a power switch 11.

[0015] Reference Figure 2 , which is the voltage reference structure diagram, the voltage input terminal 3 is connected to the voltage measurement circuit 12; the output signal of 12 is connected to the processor 13, the processor is connected to the display 2 for displaying the measurement result, the clock module 14 is located inside the processor, the serial wireless communication module 19 is connected to the processor, the wireless transceiver antenna 4 is connected to 19, and the power module 20 provides working power.

[0016] Reference Figure 3 , is the structural diagram of the measurement host, three voltage input terminals 8 are connected to the voltage measurement circuit 21; three current input terminals 9 are connected to the current measurement circuit 22; the output signals of 21 and 22 are connected to the processor 23, the processor is connected to the display 7 for displaying the measurement results, the clock module 24 is located inside the processor, the memory 26 is connected to the processor, the serial wireless communication module 25 is connected to the processor, the wireless transceiver antenna 10 is connected to 25, and the power module 27 provides working power.

[0017] In the specific implementation, the processor can select any type of single-chip microcomputer with on-chip AD, such as stm32 series single-chip microcomputer or MSP430 series single-chip microcomputer; the voltage and current measurement circuit is a commonly used AC sampling amplification and filtering circuit; the display 2 can select a monochrome dot matrix LCD, and the processor can select an SPI serial interface, and the display 7 can select a TFT display screen with a touch function, and different screen resolutions can be selected according to one's needs; the serial wireless communication module can select 2.4G or 433MHz different power modules according to the communication distance, and the memory can select an external FLASH chip such as W25Q128; the power supply circuit can select a rechargeable lithium battery and a DCDC circuit.

[0018] Reference Figure 4, is a schematic diagram of measurement synchronization in this example, time axis 28 is the voltage reference clock, time axis 29 is the measurement host clock, the measurement host sends a synchronization command 32 to the voltage reference at time t1 35, when the voltage reference receives the synchronization command, it also records 36 the voltage reference clock time t2, after the voltage reference completes the reception, it replies to the measurement host with a synchronization response command at 37 the voltage reference clock time t3, the command contains t2 and t3, when the measurement host receives the synchronization response command, it records 38 the measurement host reception clock time t4, using these four clock times, the Offset clock offset 30 and the Delay transmission delay 31 of the measurement host and the voltage reference can be calculated.

[0019] t2-t1=Delay+Offset

[0020] t4-t3=Delay-Offset

[0021] Therefore: Delay = ((t2-t1) + (t4-t3)) / 2

[0022] Offset=((t2-t1)-(t4-t3)) / 2

[0023] According to the clock offset, the clock of the measuring host is adjusted to be synchronized with the clock of the voltage reference. According to the transmission delay, the start time 39 of the next measurement is set. The measuring host sends a start measurement instruction 34 to the voltage reference. The measurement instruction carries the start time. The measuring host and the voltage reference start the measurement synchronously at the start time. After the measurement is completed, the measuring host reads the voltage reference measurement result through the serial wireless communication module, calculates the relationship between the electrical parameters or signals such as the amplitude and phase of each channel between the voltage reference and the measuring host, and outputs the result to the display. Each measurement result can be saved in the memory, and multiple results can be directly displayed on the display in a unified vector diagram after being synthesized and calculated with the voltage reference.

[0024] Since there is a certain delay from sending to receiving in wireless communication, the specific delay is affected by the environment, air rate and size of the data packet, but the delay time is fixed under the same conditions. After calculation and actual measurement, this method is a stable and reliable synchronous measurement method, and the accuracy of the measurement results can meet the measurement requirements.

Claims

1. A wireless load vector tester for a power system, comprising a voltage reference and a measurement host; The voltage reference includes a voltage measurement circuit, a display, a processor, a clock module, a serial wireless communication module and a power supply circuit; the voltage reference can work independently to achieve measurement and calculation of the frequency and amplitude of the AC voltage signal; The measuring host comprises a voltage measuring circuit, a current measuring circuit, a display, a processor, a memory, a clock module, a serial wireless communication module and a power supply circuit; the measuring host can work independently to realize the measurement and calculation of the frequency, amplitude, phase and power parameters of the three-phase voltage and three-phase current signals; wireless communication is adopted between the voltage reference and the measuring host, and the voltage reference is used as a reference, and all the input multiple measurement results are unified in a vector diagram with the voltage reference and directly displayed on the display, so as to perform PT phase core and load vector test.

2. The wireless load vector tester according to claim 1, characterized in that: The voltage reference and the measurement host communicate wirelessly, the clock of the measurement host is adjusted to be synchronized with the clock of the voltage reference according to the clock offset, the next measurement start time is set according to the transmission delay, the measurement host sends a start measurement instruction to the voltage reference, and the measurement host and the voltage reference start the measurement synchronously at the start time.

3. The wireless load vector tester according to claim 1, characterized in that: There is wireless communication between the voltage reference and the measurement host. Using synchronization instructions, the measurement host reads the voltage reference measurement results through the serial wireless communication module to achieve synchronous measurement and calculation of the frequency, amplitude, and phase electrical parameters of the voltage and current between different measurement points based on the voltage reference.

4. The wireless load vector tester according to claim 1, characterized in that: All input multiple measurement results are unified in a vector diagram with a voltage reference and directly displayed on the display, including: multiple separate measurements are performed with the same voltage reference, data is saved, multiple saved results are synthesized and calculated with the same voltage reference, and the results are directly displayed in a vector diagram.

Images