Liu Dacheng, Shanghai Acrel Electric Co., Ltd.
Abstract: With the development of technology, large enterprises are consuming more and more electricity. Therefore, how to conveniently manage electricity consumption and ensure the safe and stable operation of the power grid is of great concern. Substation automation control is a measure to improve the safety, reliability, and stability of substation operation, reduce operation and maintenance costs, improve economic efficiency, and provide users with high-quality power services. This paper introduces the important role of a monitoring system based on Acrel-2000 power monitoring software and ADL3000, ACR330ELH, and ACR320EL network power meters in optimizing production during peak electricity consumption periods in substations.
Keywords: High-energy-consuming power monitoring software, power meters, power management, peak shaving and valley filling
I. Overview
The Shanghai Electric power plant complex houses numerous production workshops, all high-energy-consuming facilities, particularly the nuclear power plant and resistance furnace workshops, which consume enormous amounts of electricity daily. The plant complex contains two high-voltage substations and three low-voltage distribution rooms, providing power for production, lighting, air conditioning, and other needs throughout the entire complex. Peak electricity consumption occurs during the hottest and coldest seasons, when the grid load approaches its peak. At these times, power rationing and time-of-use measures must be implemented for high-energy-consuming enterprises to maintain grid stability. The Shanghai Electric power plant is no exception; the power supply bureau has set a maximum load limit for the station. Exceeding this limit results in penalties. Therefore, balancing the needs of all manufacturers and users within the plant area—how to manage power rationing and meet their demands—is a critical issue. The persistent, irreconcilable conflict between the power supply load and production orders has placed significant pressure on the plant's power distribution department. Consequently, they sought a suitable solution from a professional power monitoring system developer. The following describes a highly successful solution.
II. Scheme Analysis
Acrel Electric Co., Ltd. provided Shanghai Electric Power Station with a solution combining active and passive modulation:
1. Active Modulation: Active modulation has a certain degree of compulsion. It requires considering various factors and then making subjective judgments and decisions. Active modulation is based on the Acrel-2000 power monitoring software and a monitoring system using ADL3000, ACR330ELH, and ACR320EL network power meters. These intelligent meters are installed in distribution cabinets, outgoing line cabinets, and metering cabinets. A hierarchical distributed computer communication network is then used to construct the system, which is divided into a bay layer, a communication layer, and a station control layer.
The main equipment in the mezzanine includes: multi-functional network power meters, digital and analog signal acquisition modules, and intelligent circuit breakers. These devices are installed in electrical cabinets corresponding to the primary equipment. All devices use RS485 communication interfaces and communicate via a field MODBUS bus network to achieve on-site data acquisition.
The middle layer mainly consists of a communication server, whose main function is to centrally collect data from the scattered field acquisition devices and transmit it to the station control layer, thus completing 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, centrally collecting and displaying the operating status of field equipment, presenting it to users in a human-machine interactive format. Users can also send commands to field equipment via system software to achieve remote control functionality.
The main functions of this system are:
1) Data Acquisition and Processing: Data acquisition is the foundation of power distribution monitoring. The signals that need to be acquired include: three-phase voltage U, three-phase current I, frequency Hz, power P, power factor COSφ, and electricity consumption EPI.
This function enables managers to understand important load parameters such as power, power factor, and current of each circuit, providing an accurate basis for active modulation.
2) The human-machine interface system provides a simple, easy-to-use, and user-friendly interface. It adopts a fully Chinese interface, displays the primary electrical wiring diagram of the low-voltage power distribution system, shows the status of the power distribution system equipment and corresponding real-time operating parameters, and features timed screen rotation and real-time dynamic screen refresh; it also displays analog quantities.
3) The power management system automatically performs daily, monthly, and yearly power consumption statistics, and generates daily, monthly, and yearly reports. This function provides managers with convenient and accurate reports, and the analysis of power consumption in each circuit provides detailed data for proactive power regulation.
4) The operating load curve is automatically generated by periodically collecting the current load parameters of the incoming line and important circuits, so that users can understand the operating load status of the equipment in a timely manner.
This function allows users to observe the load curves of each circuit during the same period in previous years, identifying patterns in electricity consumption for each circuit. This makes active modulation more accurate and reasonable.
5) Alarm Load Limit Setting: Upper limits can be set for the high-voltage incoming load and the load of each transformer. When real-time data exceeds the upper limit, the data changes from black to red, and a record is left in both real-time and historical alarms. (See figure)
This function allows setting a load limit for each transformer and for each outgoing circuit. If the load limit is exceeded, the system will trigger an alarm and record the event. Administrators can use this function to manage and limit power usage.
2. Passive modulation
Passive modulation primarily regulates electricity consumption through time-of-use and floating electricity costs. Some energy-intensive factories consume enormous amounts of electricity, yet electricity prices significantly impact the profits of their products. Therefore, we implement multi-tiered electricity metering based on active modulation.
Multi-rate meter reading: This feature allows for setting peak, off-peak, and valley time periods, enabling time-of-use electricity billing. The interface displays the multi-rate electricity usage for each circuit. By adjusting peak, valley, and off-peak rates and setting the meter reading time, electricity bills can be easily calculated.
Additional system features:
1) Fault alarm and accident recall: When an operational fault occurs in the power distribution system, an audible and visual alarm will be issued in a timely manner to prompt the user to respond to the faulty circuit. At the same time, the time and location of the event will be automatically recorded so that the user can query and recall the cause of the fault.
2) User access control allows for the addition and removal of software users and the setting of user permissions according to the buyer's requirements. Different permission groups can be set for different levels of users to prevent losses to production and daily life due to human error, and to ensure the safe and reliable operation of the power distribution system.
III. Features of the Solution:
This system was designed and implemented with a distributed data acquisition and centralized control management system, eliminating the tedious task of frequent on-site meter reading and analysis by on-duty personnel. Based on real-time and historical data, it accurately adjusts the power distribution system, thereby optimizing production during peak electricity consumption periods. This solution improves power supply quality and management level, and has advantages such as simplicity, practicality, and low investment.
IV. Conclusion
This active and passive modulation solution enables Shanghai Electric's power plants to continue production under maximum permissible load, maximizing profits. The system can measure the power quality parameters of the power plant, showing where the electricity is used, whether there is any waste, and whether energy-saving measures are effective—all clearly visible and monitorable to company managers. Substation automation is a complex system engineering project, and many technical challenges need to be overcome to achieve its full functionality. The author believes that in the not-too-distant future, easily manageable substation automation systems will experience a period of rapid development.
References
[1] Ren Zhicheng and Zhou Zhong, eds. Principles and Application Guide of Digital Instruments for Power Measurement, China Electric Power Press, 2007.4
[2] Zhu Liquan. Analysis of Intelligent Management System for Power Distribution System. Intelligent Building Electrical Technology, Vol. 1, No. 4, 2007.
[3] Wang Zhensheng's analysis of "Computer Monitoring System for Substations", Intelligent Building Electrical Technology, Vol. 5, No. 3, 2006
For more detailed information, please contact:
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