Application of PLC and EDA9033 in low voltage dist

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The application of PLC and EDA9033 in low-voltage distribution

1. introduction

the development of modern science and technology has put forward higher requirements for the reliability and intelligent management of low-voltage distribution system. The rapid development of computer technology, communication technology and microelectronics technology has promoted the emergence of intelligent low-voltage electrical management system and will become the development trend of low-voltage distribution system in the future. The intelligent low-voltage distribution system makes full use of the technical achievements of the digital age. It takes the existing circuit breakers, contactors, relays, etc. as the control basis, and combines the new intelligent power instruments, monitoring modules, on-site and background monitoring devices, network i/o to realize the real-time monitoring of the voltage, current, active power, reactive power, power factor, frequency, electricity and other electrical parameters of the main distribution circuit and each branch circuit, Control and monitor the opening and closing of control appliances [1. At the same time, cooperate with communication to promote the extension and development of terminal product networks such as fine chemicals and textiles and various perfect remote monitoring software, so as to realize the "four remotes" of low-voltage distribution system Functions: remote measurement, remote control, remote signaling and remote adjustment. This paper will introduce how to use EDA9033 to collect various parameter data, and how to use the i/o interface of PLC to control and detect the contactors in the low-voltage distribution circuit to realize the intelligent management of the low-voltage distribution system

2. programmable controller (PLC)

programmable controller (PLC) was developed on the basis of relay control system in the late 1960s. After more than 30 years of development, its function and stability have been quite perfect. Modern PLC products integrate data processing, program control, parameter adjustment and data communication, It can meet the needs of most applications for monitoring and controlling industrial production [2.

PLC can be used to realize the remote terminal unit (RTU) function of medium and low voltage distribution automation, which can well meet the unique requirements of RTU. The discrete input points of PLC are used to realize remote signaling, the discrete output points of PLC are used to realize remote control, and the analog sampling input of PLC is used to realize telemetry (the telemetry work described in this paper is mainly collected by EDA9033 electrical parameters and sent to PLC for processing.) Use the communication function of PLC to realize the communication with the host [3. To complete these functions, there is no need for additional hardware. It is only necessary to simply program the PLC according to the actual situation of the switching value. This RTU implementation scheme for medium and low voltage distribution automation based on PLC has the following characteristics: simple hardware structure, completely maintenance free; large or small scale; the increase of remote control points, remote signaling points and telemetry points can be realized only by connecting the PLC expansion modules together; it is resistant to harsh environment; and it is highly reliable Sex; Programming to achieve various functions, free of hardware debugging; Low cost

3.eda9033 three-phase power frequency AC parameter data acquisition module

eda9033 is a fully digital three-phase power frequency AC parameter data acquisition module with wide application prospect. This module makes it very easy for computer to collect three-phase AC parameter data, simplifies the system, and improves the reliability. It can be used to measure the true effective value of three-phase voltage and current, active power, reactive power, power factor, accumulated electricity and other three-phase power frequency AC electrical parameters in three-phase three wire system or three-phase four wire system circuits, At the same time, its own RS-232 or RS-485 serial communication interface can be easily connected with PLC or microcomputer [4. EDA9033 can replace the current, voltage, power factor and electric quantity transmitters in various industrial control and power systems and the analog input module for measuring the output signals of these transmitters. It can reduce the system cost, facilitate field wiring and improve the reliability of the system.

eda9033 has a voltage range of 10 ~ 500V and a current range of 1 ~ 20A. At the same time, the module can correctly measure the input value 1.5 times the full range, exceeding the full range The input of 1.5 times of the range cannot be measured correctly, and more than 10 times of the full range value will cause damage to the module. According to these characteristics, when selecting the module range, the module with the nominal voltage and current value close to the module should be selected, and a certain margin should be reserved. At the same time, the range should not be too large, otherwise the measurement accuracy of the module will be reduced. The voltage and current measurement range of EDA9033 module is not wide. Therefore, when the module is applied to the power system with high voltage and large current, it should be equipped with corresponding current transformers for measurement according to the main wiring and secondary wiring of the power system

4.plc and ED are ideal choices to replace traditional epoxy and PP resins. Application design of a9033 in low-voltage power distribution

the following takes the low-voltage power distribution monitoring system in Wuhan Hankou jiangtan Park as an example to discuss the application design of PLC and EDA9033 in its low-voltage power distribution cabinet. The project is 7km long and about 200 wide. The total area of the park is 1.5 million square meters. The power load in the park is complex, scattered and diverse. There are more than 20 box transformers and more than 30 low-voltage distribution rooms along the line. Taking one of the distribution rooms as an example, this paper focuses on the application design of PLC and EDA9033

4.1 design of main distribution circuit

through low-voltage cables, 380/220v mains power from the low-voltage side of the box transformer is led to the low-voltage copper bus of the switchgear through the disconnector and circuit breaker, and then divided into several branches by the low-voltage circuit breaker. Each branch circuit is equipped with ordinary three-phase alternating current contactor and current transformer, and finally to the single-phase or three-phase electrical load. Each distribution cabinet has 14 three-phase distribution circuits in total. The capacity of a single distribution surface bonding strength cabinet is about 150KVA, and each branch three-phase circuit is about 10kW. The distribution system diagram of its distribution cabinet is shown in Figure 1

according to the distribution system diagram, the current of all three-phase distribution circuits is greater than the range (20a) of EDA9033. During the distribution design, 15 mutual inductors are configured for each distribution cabinet, l0 is the total current detection mutual inductor of the distribution cabinet, with a transformation ratio of 250/5, and l1-l14 is the current detection mutual inductor of 14 branch circuits, with a transformation ratio of 30/5; Km1-km14 are three-phase contactors for controlling the connection of branch distribution circuit, and the model is LCA 220VAC

4.2 selection of electrical parameter detection unit

15 EDA9033 electric quantity acquisition modules (developed and produced by Shandong Lichuang Technology Co., Ltd.) are selected for the project to detect the total current of the distribution cabinet and the current, voltage, power factors and other electrical parameters of each branch circuit. The module adopts electromagnetic isolation and photoelectric isolation technology to make the voltage input, current input and signal output complete

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