Application of power distribution monitoring system in Shengli Oilfield Geophysical Exploration Institute project

Abstract: This paper introduces an application based on digital intelligent instrument in the transformation of power distribution system. The field layer uses intelligent digital display instrument (SCADA) to collect U, I, P, COS¢, Ep and other electrical parameters and switch signals of the power distribution site; the field instrument network communication is remotely transmitted to the background monitoring system, and the output control relay of the intelligent instrument is used to remotely control the closing and opening operation of the circuit breaker to achieve the automatic comprehensive management of the low-voltage distribution system. Keywords: low-voltage intelligent power distribution system Acrel-2000 type three-remote RS485 communication power monitoring Overview The power distribution room of Shengli Oilfield Geophysical Exploration Institute was completed and put into operation in 1992 and has been operating safely for 16 years. The power distribution system is divided into high and low voltage parts. The high-voltage part has two 10KV incoming lines, Liaocheng Line A and Zibo Line A, and 6 1250KVA on-load voltage regulating transformers. The Institute of Geophysical Exploration is an important power load user, mainly including the processing room cluster on the second floor of the network and its supporting power equipment; the interpretation room on the third floor of the network, the LAN server and its supporting power equipment, the computer and its supporting power equipment in the ERP room of the Bureau Information Center; the power equipment in the processing and interpretation room of the comprehensive building; the refrigeration unit and its supporting power equipment, as well as the production and living electricity of the whole institute. The high and low voltage primary equipment was installed fourteen years ago. The original power distribution system used the MS-2801 database definition system, which used many spare parts, many communication line contacts, and was prone to failure. The operating system was Windows NT4.0, which was cumbersome to apply and maintain. In recent years, with the increase of power load in the institute and the expansion of SP2 group, the capacity and quantity of transformer and distribution circuit switch can no longer meet the current power load demand, and the equipment is seriously aged, and the circuit breaker breaking capacity is poor; in addition, the power supply company is boosting the oil field line, the original 6KV incoming line has been upgraded to 10KV, the original low-voltage bus and transformer outgoing line switch capacity is insufficient, and the capacitor compensation cabinet has also aged, which can not play the role of reactive power compensation. In order to ensure the normal operation of scientific research and production in the institute, we have carried out a comprehensive system transformation of the low-voltage distribution system. Since the Geophysical Exploration Institute is a first-level power supply user, the power supply system is required to be absolutely safe and reliable. According to the requirements of remote monitoring and centralized management of site equipment, the modified distribution system adopts the Acrel-2000 low-voltage intelligent distribution system to realize the telemetry, telesignaling and remote control of high and low voltage equipment, namely the "three remote" functions. The Acrel-2000 low-voltage intelligent distribution system makes full use of the latest developments in modern electronic technology, computer technology, network technology and field bus technology to conduct decentralized data collection and centralized monitoring and management of the transformer and distribution system. The secondary equipment of the distribution system is networked, and the scattered field equipment of the distribution station is connected into an organic whole through computers and communication networks to realize remote monitoring and centralized management of the power grid operation. 1 The composition of the distribution monitoring system This system adopts a hierarchical distributed computer network structure, namely the interval layer, communication layer and station control layer as shown in the following figure: Figure 1 The main equipment of the interval layer is: multi-functional network power meter, switch quantity, analog quantity acquisition module and intelligent circuit breaker, etc. 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 field MODBUS bus network to realize field data collection. The middle layer is mainly: communication server, whose main function is to collect the scattered field collection devices in a centralized manner and transmit them to the station control layer at the same time to complete the data interaction between the field layer and the station control layer. Station control layer: equipped with high-performance industrial computers, displays, UPS power supplies, printers, alarm buzzers and other equipment. The monitoring system is installed on the computer, and the operation status of the field equipment is collected and displayed 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, and the wiring is simple and convenient; the communication interface is half-duplex communication, that is, both parties of the communication can receive and send data, but can only send or receive data at the same time, and the maximum data transmission rate is 10Mbps. The RS-485 interface uses a combination of balanced drivers and differential receivers, and the anti-noise interference ability is enhanced. Up to 32 devices are allowed to be connected on the bus, and the maximum transmission distance is 1.2km. 2 Main functions of the monitoring system Data acquisition and processing Data acquisition is the basis of power distribution monitoring. Data acquisition is mainly completed by the underlying multi-functional network instrument collection to realize the 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, electricity Ep, remote equipment operation status and other data. Data processing is mainly to display the electrical parameters collected as required to the user in real time and accurately, so as to achieve the automation and intelligent requirements of power distribution monitoring, and at the same time store the collected data in the database for user query. The human-computer interaction system provides a simple, easy-to-use and good user interface. The full Chinese interface is adopted, and the CAD graphics display the primary electrical wiring diagram of the low-voltage distribution system, display the status of the distribution system equipment and the corresponding real-time operating parameters, and the screen is switched regularly; the screen is refreshed in real time and dynamically; analog quantity display; switch quantity display; continuous recording display and other fault alarms and accident recalls. When a distribution system fails, an audible and visual alarm will be issued in time to prompt the user to respond to the fault circuit in time, and the time and place of the event will be automatically recorded for the user to query and recall the cause of the fault. Database establishment and query mainly complete the timing collection of telemetry and telesignaling, and establish a database to generate reports regularly for users to query and print. User authority management sets different authority groups for users of different levels to prevent losses caused by human error in production and life, and realize the safe and reliable operation of the distribution system. Electricity cost management automatically performs daily, monthly and annual electricity statistics, and can set peak, peak, flat and valley time periods to realize the function of electricity time-sharing billing, and generate daily, monthly and annual reports at the same time. The operation load curve collects the current load parameters of the incoming line and important circuits regularly, and automatically generates the operation load trend curve, which is convenient for users to understand the operation load status of the equipment in time. 3 Case Analysis The low-voltage power distribution system of Shengli Oilfield Geophysical Exploration Research Institute mainly has 6 10kv/0.4kv distribution transformer, this system is mainly responsible for real-time dynamic monitoring of low-voltage incoming lines and corresponding distribution circuits. The incoming line uses ACR320EK multi-function network power meter, which is designed for 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, current, active power, reactive power, power factor, frequency, active electricity, reactive electricity and other electrical parameters. And this meter has 4-way photoelectric isolation switch input contacts and 2-way relay control output contacts, which can cooperate with intelligent circuit breakers to realize remote signaling and remote control operation of 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 ACR100K series network power meters, which mainly complete the measurement of three-phase current, three-phase voltage, active electricity, as well as the detection of switch signals and relay remote control output. 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 the telemetry value, circuit breaker operation status information, operation event alarm, screen quick switching, system function menu and other main functions in real time. Figure 2① Telemetry: mainly monitors the electrical parameters of the operating equipment, including: three-phase voltage, current, power, power factor, electric energy, frequency and other electrical parameters of the incoming line and the three-phase current of the distribution circuit; ② Telesignaling: realizes the display of the operation status of the field equipment, mainly including: the opening and closing operation status of the switch and the communication fault alarm; ③ Remote control: mainly realizes the remote opening/closing operation of the intelligent circuit breaker. All operations must pass strict authority verification to prevent operators from operating incorrectly. Report statistics function: mainly completes the event record report of the incoming line circuit (see Figure (3)); remote meter reading (see Figure (4)) and electricity consumption statistics report statistics (see Figure (5)), supports time query and report printing output. Load curve: collect the current parameters of the incoming line circuit regularly and generate trend curves (see Figure (6)) at the same time, so as to understand the equipment load status in real time and provide a basis for accident recall. Figure 3 System features There are few communication line contacts, the screen display is intuitive, the data is refreshed quickly, and the operating status of the on-site equipment is reflected in time. At the same time, the system operation is simple and convenient for users. Conclusion: At present, the system has been successfully put into operation for nearly half a year. The system runs safely and stably, which greatly facilitates the use of users. With the rapid development of society, users have higher and higher requirements for power supply and distribution automation and intelligence. Realizing unmanned distribution room has become a direction for the development of future distribution automation. ACREL-2000 low-voltage intelligent distribution system is one of the good 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 distribution system can be realized and guaranteed, and on this basis, the equipment operation cost can be reduced and the quality of distribution automation can be improved. References Ren Zhicheng and Zhou Zhong, Principles and Application Guide of Power and Electric Measurement Digital Instruments, China Electric Power Press, 2007.4 Zhu Liquan, Analysis of Intelligent Management System of Substation and Distribution System, Intelligent Building Electrical Technology, Vol. 1, No. 4, 2007 Wang Zhensheng, Analysis of "Computer Monitoring System of Substation and Distribution Station", Intelligent Building Electrical Technology, Vol. 5, No. 3, 2006