Keywords: low-voltage intelligent power distribution system, Acrel-2000, three-remote RS485 communication 0 Overview 1 Distribution monitoring system composition This system uses a layered distributed computer network structure, that is, the bay layer, communication layer and station control layer as shown below: 2 Main functions of the monitoring system 3 Case analysis The low-voltage distribution system of Shengli Oilfield Geophysical Prospecting Institute mainly has 6 10kv / 0.4kv distribution transformers. This system is mainly responsible for real-time dynamic monitoring of low-voltage incoming lines and corresponding distribution circuits. Figure (1) Main monitoring screen â‘ Telemetry: It mainly monitors the electrical parameters of the operating equipment, including: incoming three-phase voltage, current, power, power factor, electrical energy, frequency and other electrical parameters and the three-phase current of the allocated circuit; Figure (2) Event record report Figure (3) Remote meter reading report Figure (4) Energy statistics report Load curve: collect the current parameters of the incoming circuit regularly, and generate a trend curve at the same time (see figure (5)) to understand the load status of the device in real time and provide a basis for accident recall. Figure (5) Trend curve 4 System characteristics The communication line has few contacts, the screen display is intuitive, the data is refreshed quickly, and the operation status of the field equipment is reflected in time. At the same time, the system is simple to operate and convenient for users to use. 5 Conclusion At present, the system has been successfully put into operation for nearly half a year. The system is safe and stable, which greatly facilitates the use of users. With the rapid development of society, users have higher and higher requirements for power distribution automation and intelligence. The realization of unattended power distribution rooms has become a direction for future development of distribution automation; ACREL-2000 low-voltage intelligent power distribution The system is one of the good power distribution systems to solve the high-quality operation of power supply and distribution. Through the operation of the system, the reliable, safe and stable operation of the power distribution system can be realized and guaranteed, and on the basis of this, the equipment operating cost is reduced and the power distribution is improved Automated quality. references About the Author: Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system
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The power distribution room of the Geophysical Exploration Institute of Shengli Oilfield was completed and put into production in 1992. It has been in safe operation for 16 years. The power distribution system is divided into two parts: high and low voltage. The high voltage part has two 10KV incoming lines of Liaocheng A Line and Zibo A Line, with 6 units. 1250KVA on-load voltage regulating transformer. The geophysical exploration institute is an important power load user, mainly including the computer room cluster on the second floor of the network and its supporting power equipment; the third floor of the network explains the computer room, LAN server and its supporting power equipment, ERP computer room computer and its supporting power equipment ; Comprehensive building processing and interpretation of electrical equipment used in the computer room; refrigeration units and supporting electrical equipment as well as the production and living electricity of the whole hospital.
The high and low voltage primary equipment was installed 14 years ago. The original power distribution system used the MS-2801 database definition system. It uses many spare parts, many communication line contacts, and is prone to failure. The operating system is Windows NT 4.0. Application and maintenance It's more complicated. In recent years, with the increase of the electrical load of the whole hospital and the expansion of the SP2 fleet, the capacity and number of transformers and distribution circuit switches have been unable to meet the current demand for electrical loads, and the equipment is seriously aging and the breaking capacity of the circuit breaker is poor; in addition The power supply company is working on boosting the oil field lines. The original 6KV incoming line has been upgraded to 10KV. The original low-voltage bus and transformer outlet switch capacity is not enough, and the capacitor compensation cabinet has also aged, which has no effect on reactive power compensation. In order to ensure the normal operation of the scientific research and production of the whole institute, we carried out a comprehensive system transformation of the low-voltage distribution system.
Because the geophysical exploration institute belongs to the first-level power supply user, the power supply system requires absolute safety and reliability. According to the requirements of site equipment for remote monitoring and centralized management, the transformed power distribution system adopts Acrel-2000 low-voltage intelligent power distribution system to realize the functions of remote measurement, remote signaling, and remote control of high and low voltage equipment.
Acrel-2000 low-voltage intelligent power distribution system makes full use of the latest developments in modern electronic technology, computer technology, network technology and field bus technology, and carries out decentralized data collection and centralized monitoring and management of the power distribution system. Network the secondary equipment of the power distribution system, and connect the field equipment of the distributed power distribution station into an organic whole through the computer and communication network to achieve remote monitoring and centralized management of the power grid operation.
The main equipment of the bay layer is: multi-function network power meter, switch, analog acquisition module and intelligent circuit breaker. These devices are installed in the electrical cabinet corresponding to the corresponding primary equipment. These devices all use RS485 communication interface and communicate through the on-site MODBUS bus to achieve on-site data collection.
The middle layer is mainly: the communication server, whose main function is to centrally collect the scattered collection devices, and at the same time remotely transmit to the station control layer to complete the data interaction between the field layer and the station control layer.
Station control layer: equipped with high-performance industrial computers, monitors, UPS power supplies, printers, alarm buzzers and other equipment. The monitoring system is installed on the computer, and collects and displays the running status of the field equipment in a centralized manner, and displays it to the user in the form of human-computer interaction. At the same time, the user can send instructions to the field equipment through the system software to realize the remote control function.
The above network instruments all use RS485 interface and MODBUS-RTU communication protocol. RS485 uses shielded wire transmission. Generally, two wires are used. The wiring is simple and convenient; the communication interface is half-duplex communication, that is, both parties to the communication can receive and send data. Only data can be sent or received at the same time, and the maximum data transmission rate is 10Mbps. The RS-485 interface is a combination of a balanced driver and a differential receiver, which enhances the ability to resist noise interference. Up to 32 devices can be connected to the bus, and the maximum transmission distance is 1.2km.
1) Data collection and processing Data collection is the basis of power distribution monitoring. Data collection is mainly completed by the bottom multi-function network instrument collection to achieve local real-time display of remote data. The signals that need to be collected include: three-phase voltage U, three-phase current I, frequency Hz, power P, power factor COSφ, electrical Ep, remote equipment operating status and other data.
Data processing is mainly to display the electrical parameters collected according to the requirements to users in real time and accurately, to achieve the automation and intelligence requirements of power distribution monitoring, and at the same time to store the collected data into the database for user query.
2) The human-computer interaction system provides a simple, easy-to-use and good user interface. Adopt full Chinese interface, CAD graphics display the main electrical wiring diagram of low-voltage power distribution system, display the status of the power distribution system equipment and corresponding real-time operating parameters, the screen regularly polling switch; real-time dynamic refresh of the screen; analog display; switch display; continuous Record display, etc.
3) Fault alarm and accident recall When an operation fault occurs in the power distribution system, an audible and visual alarm will be issued promptly to prompt the user to respond to the fault circuit in a timely manner, and at the same time automatically record the time and place of the event to be queried by the user to recall the cause of the fault.
4) Database establishment and query mainly completes the remote measurement and remote signal collection at regular intervals, and establishes a database, and regularly generates reports for users to query and print.
5) User authority management For different levels of users, set different authority groups to prevent losses caused by human misoperation to production and life, and realize safe and reliable operation of the power distribution system.
6) Electric energy cost management automatically performs daily, monthly, and annual electrical energy statistics, and can set the peak, peak, flat, and valley time periods to realize the time-sharing billing function of electrical energy, and generate daily, monthly, and annual reports at the same time.
7) The operating load curve regularly collects the incoming line and important loop current load parameters, and automatically generates the operating load trend curve, which is convenient for users to timely understand the operating load status of the equipment.
ACR320EK multi-function network power meter is used for incoming power. It is a network power meter designed for the power monitoring needs of power systems, industrial and mining enterprises, public facilities, and intelligent buildings. It can measure all conventional power parameters, such as: three-phase voltage, Various electrical parameters such as current, active power, reactive power, power factor, frequency, active power, reactive power, etc. In addition, the instrument has 4 photoelectric isolation switch input contacts and 2 relay control output contacts. These contacts can cooperate with intelligent circuit breakers to achieve remote signaling and remote control operations of the circuit breakers. This series of network power meters are mainly used in substation automation, distribution network automation, community power monitoring, industrial automation, energy management systems and intelligent buildings.
The important distribution circuit uses the ACR100K series network power meter, which mainly completes the measurement of three-phase current, three-phase voltage, active power, the detection of switching signals and the remote control output of the relay.
Generally, the distribution circuit adopts Pz42-AI / KC series network instrument, which mainly completes three-phase current measurement, switch signal detection and relay remote control output.
Figure (1) is the main monitoring screen of the system, which displays real-time telemetry values, circuit breaker operating status information, operating event alarm, quick screen switching, system function menu and other main functions.
â‘¡ Remote signaling: The display of the operating status of on-site equipment mainly includes: the opening and closing operating status of the switch and communication failure alarm;
â‘¢Remote control: Mainly realize the remote opening / closing operation of the intelligent circuit breaker, all operations must pass the strict authority verification to prevent the operator from misoperation.
Report statistics function: mainly complete the event record report (see figure (2)) of the incoming circuit; remote meter reading (see figure (3)) and electricity consumption statistical report statistics (see figure (4)), support time query and Report printout.
[1] Ren Zhicheng, Zhou Zhong, Principles and Application Guide of Electric Power Measurement Digital Instruments, China Electric Power Press, 2007.4
[2] Analysis of Intelligent Management System of Zhu Liquan Substation Distribution System Intelligent Building Electrical Technology 2007 Vol.1 No.4
[3] Wang Zhensheng analyzes "Substation Computer Monitoring System" Intelligent Building Electrical Technology 2006
Abstract: Introduce an application based on digital intelligent instruments in the transformation of power distribution system. The field layer uses intelligent digital display instruments (SCADA) to collect electrical parameters and switching signals such as U, I, P, COS ¢, Ep at the power distribution site ; On-site instrumentation network communication and remote transmission to the background monitoring system, at the same time through the intelligent instrument output control relay, remote control circuit breaker closing and opening operations, to achieve low-voltage power distribution system automation and comprehensive management.