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Power transmission line monitoring system design and implementation

In Electronic Infomation Category: P | on April 15,2011

Abstract: This paper describes the MSP430 microcontroller as the core of the power transmission line monitoring system, working principle and MAX792LCSE datasheet and the software and MAX792LCSE price and hardware design. System consists of voltage, current transformers, DSP power chip, the signal processing circuit, LCD large character LCD display, keyboard, sound and MAX792LCSE suppliers and light alarm circuit, U disk memory and MSP430 MCU host circuits, power line parameter for automatic monitoring and collection storage function has been studied to realize a long time, without interruption of power transmission lines in the current, voltage, zero sequence current, power factor, active power, reactive power, apparent power, fundamental and harmonic energy monitoring, recording and storage.

0 Introduction

Manual adjustments to address the partial-phase power transmission lines is difficult observation, recording difficult, difficult calibration of the three problems. The design of hardware and software through the design, implementation for a long time, without interruption of power transmission lines in the current, voltage, zero sequence current, power factor, active power, reactive power, apparent power, fundamental and harmonic energy monitoring, recording and storage. The design uses a MSP430F135 microcontroller for the control of the core, with the voltage, current transformers, DSP power chip, man-machine interface, sound and light alarm circuit and signal processing circuit to achieve the monitoring of power transmission line parameters, the system can use stored in the U disk data collected in the time machine in the upper curve analysis, the load line for the adjustment of the power sector to provide scientific and reliable basis.

1 system design

1.1 DSP power chip select The design uses DSP

power chip, the chip has seven second-order 16-bit sigma-delta ADC, the reference voltage output, voltage and current sampling, fundamental, harmonics and frequency measurement of the energy signal processing circuit, both SPI communication interface, and supports all-digital domain gain and phase correction. Can automatically calculate active power, reactive power, apparent power and power factor load. Internal voltage monitoring circuit with, can guarantee the power and power-down work normally.

High-precision measurements of the design to the input dynamic range of 1000:1, while ensuring that non-linear measurement error within 0.1%. Gain and phase compensation, low current non-linear compensation. Voltage and current RMS accuracy of better than 0.5%.

1.2 single chip select

MSP430 microcontroller for low-power 16-bit microcontroller, the SOC has the typical characteristics of a large number of integrated peripherals. In particular, the baud rate is fine-tuning its internal integrated device, the MCU can not less than 32 768 Hz in any of the crystal (the crystal, but can not exceed the maximum allowed limit on MCU) work, select the communication baud rate may not with fractional baud rate factor does not limit, namely: the baud rate can be allowed to use any frequency within the crystal. In addition, the MSP430 MCU integrates a temperature sensor, can be more easily achieve the level of the pressure sensors measuring temperature compensation. And the MSP430 family of microcontrollers for different applications by a variety of different modules, the microcontroller used in low power consumption, by an ordinary battery to work, to achieve long without a break normal use.

2 overall composition of the system structure and working principle

Shown in Figure 1 the whole system mainly consists of the host microcontroller circuit, control circuit, signal measurement, sound and light alarm circuit, the key circuits, LCD character display circuit, power circuit and communication circuit. P1 port data lines as a system, DSP power chip MCU P3.0 P3.1 P3.2 port access to the system used to input data, the work of sound and light alarm module output signal an alarm through the P2.5 port sound. Keyboard module P2.0, P2.1 and P2.2 port MCU is used to control access to the 6 buttons. System through the port P1 and P5.0, P5.1 control LCD display, serial communication from the P3.6 and P3.7 through the communication interface circuit control U disk read and write, the systems power module produces 3.3 V, +5 V voltage for the system provide a stable voltage.

Figure 1 system overall composition

The system uses voltage and current through the differential transformer power conversion and enter the DSP chip for signal analysis and processing, the output value of high-precision three-phase voltage, phase current, zero sequence current, active power, reactive power, apparent power, power factor, fundamental and harmonic energy values ??and other data, the data read through the SPI communication interface chip DSP energy expenditure data was calculated, data were converted into the LCD display [4-5 ]. When the system time to run to the U disk write time specified, the system automatically records all data collected. Users can enter the settings through the acquisition time interval of the keyboard. The system can be set in the device number. Meanwhile, the system also can display the temperature of the working environment and system time.

3 systems main hardware circuit design

3.1 signal differential input circuit design

A differential input signal input, the input current and voltage sensor signal is sampled by the sampling resistor R17, C5, C6 filtering, reduce interference, REFO through the 10K current limiting resistor to provide a standard 16-bit AD reference voltage. Voltage and current signal input circuit shown in Figure 2.

Figure 2 voltage and current signal input circuit

3.2 Communication Control Circuit

Functionality of the system to complete the communication circuit with TTL-level CMOS level conversion. Passive input stage without communication is not power, only when the power of communication, so that the whole system of great help to achieve low power consumption, which is dedicated conversion chip on the market do not have the features. The control circuit shown in Figure 3.

communication control circuit in Figure 3

3.3 sound and light alarm circuit design

Sound and light alarm circuit by the transistor, light emitting diodes, resistors, capacitors, components and other components buzzer, when the measured level is less than the set warning value, the microcontroller will send alarm signals alarm, upon receipt of the alarm signal LED is lit, the buzzer sound, a sound and light alarm effect.

4 Software Design

Modular software design is divided into seven modules: system initialization module, LCD display module, key identification and processing module, SPI analog communication module, serial communication module, U disk read-write module. Time, the working environment temperature detection module.

Initialize the modules main role is to set the display buffer, stack pointer, the work unit, the operation flag and working registers, the I / O ports, and the work of CMU clock module settings, set the system timer module, communication module , DSP power chip module interrupt initialization and system settings; LCD display module displays the main role is to collect the data and system operating parameters and other data; keyboard module is responsible for the identification and keys were keys, call to action when the corresponding button The key processing subroutine for processing. Can be realized on the system time, storage interval, the device number be set; SPI module communication module main role is to complete the power MCU and DSP chip data exchange. Serial communication module to send data to the U disk module in preparation for data storage; U disk reader modules role is to transfer the data to write MCU U disk and storage; time, the working environment is the role of temperature detection module completed on time calculation, while the temperature of the working environment real-time acquisition.

5 Conclusion

The instrument can be widely used in electric power, petroleum and chemical industry, real-time detection and record the various parameters of power lines, and in a timely manner to the U disk storage, to facilitate the actual situation of technical staff under the line to adjust equipment. The instrument has a stable and reliable performance, small size, low cost, and measurement and control is accurate, sensitive, easy to install, low power consumption with high practical value.

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