Application of New Pole-Mounted Circuit Breakers in Small Hydropower Stations in Mountainous Areas
Small hydropower refers to power stations with a single-unit installed capacity of less than 50,000 kV. The integration of small hydropower into the distribution network alters the system topology and power flow direction. Literature has analyzed and discussed the challenges in regulating regions rich in small hydropower, studied reclosing strategies for distribution network lines with small hydropower, and proposed a new type of automatic safety disconnection device for small hydropower.
1 Current Status of Small Hydropower in Mountainous Areas
The total area is 45,385 km², with mountainous terrain accounting for 98.3% of the region. There are 58 small hydropower stations with a total installed capacity of 41.45 MW, most of which have an installed capacity below 1 MW. These stations are widely distributed and suffer from poor communication conditions.
Due to their age, the stations primarily use mechanical control equipment and lack automation devices. Most gateway meters are pulse meters, relying on manual reading without remote transmission capabilities. Control protection devices and synchronization equipment lack communication interfaces, necessitating manual reporting of operational data to dispatchers via telephone.
The 10 kV lines of the grid's 35 kV substations often operate in a hybrid mode where small hydropower and load consumption coexist. The high-voltage side of the station's main transformer uses drop-out fuses, which are simple in structure and connected to the 10 kV grid-connected lines via T-connections.
2 Problem Analysis
2.1 Impact on the Activation of Line Automatic Control Devices
In active distribution networks, after a substation outlet circuit breaker trips, small hydropower stations may continue to supply power to the fault point, hindering fault arc extinction and reducing the success rate of reclosing. If distributed energy resources (DERs) remain connected during reclosing, asynchronous closing may occur, resulting in inrush currents that can cause reclosing failure and damage small hydropower units.
Some 10 kV grid-connected power plants lack under-voltage disconnection protection for both their grid-connected line protection and generator protection, failing to meet grid operation requirements. This severely impacts the grid's safe and reliable power supply and the operational lifespan of the generators.
When a fault occurs in the grid-connected channel of a small hydropower station, the generator fails to disconnect quickly after the system side clears the fault. This may lead to asynchronous grid reconnection after the system-side line reclosing action, preventing the system-side reclosing from activating and causing unnecessary power outages for public transformer users, resulting in significant negative social impact.
Thus, when a fault occurs in the grid-connected channel, the generator's inability to disconnect quickly severely affects the grid's safe and reliable power supply and may cause asynchronous grid reconnection.
2.2 Incomplete Transmission of Dispatch Information
Based on field surveys, most small hydropower stations are located in mountainous areas, far from the grid's central substations. Installing dedicated optical fiber cables through forests would be costly and unreliable. Upgrading automation equipment and transmitting data via secure wireless private networks after cybersecurity assessments also requires significant investment. Additionally, most small hydropower plants have limited capacity and low发电效益, reducing their incentive for upgrades. Communication channel limitations result in incomplete information being sent to the dispatch center.
However, the inability to transmit real-time operational data to the regional dispatch center affects the dispatchers' analysis of the grid and the reliability of 10 kV distribution transformers on grid-connected lines. The dispatch platform will be forced to operate blindly for small hydropower stations for extended periods, jeopardizing the safe operation of the regional grid.
3 Solutions
3.1 Solution Overview
To achieve effective monitoring and data acquisition for small hydropower units and enhance grid security and reliability, the drop-out fuses on the high-voltage side of the main transformers are replaced with new pole-mounted vacuum circuit breakers equipped with high-precision electronic sensors. These are paired with Feeder Automation Terminals (FTUs) featuring remote signaling, telemetry, remote control, and automatic disconnection functions to collect data at the 10 kV grid connection point and switch status.
The existing gateway pulse meters are replaced with three-phase electronic multifunctional energy meters to collect operational data from the generator units, which is transmitted to the FTU via fieldbus. The FTU is equipped with a dual-card communication vertical encryption module. Data is securely encrypted and uploaded to the integrated regional dispatch system via a dedicated public wireless network channel with strong signal coverage.
When a fault on the grid-connected line causes the substation outlet switch to trip, the FTU's loss-of-voltage protection activates, and the pole-mounted circuit breaker opens to disconnect the small hydropower station from the grid. Re-synchronization and reconnection occur after power supply restoration.
3.2 Digital Automation Package Equipment
The digital automation package includes ZW32-type pole-mounted circuit breakers, double-sided isolation disconnectors, power voltage transformers, and digital FTUs. The circuit breaker unit integrates three combined electronic sensors (EVCT) and a local digital unit (ADMU).
The overall structure is compact and lightweight, facilitating installation and maintenance. Compared to traditional intelligent via monitoring software of detection equipment, this system allows the monitoring software to obtain operational data from the operating systems of 32 units. It simultaneously captures file sizes from camera images and monitors whether the software of detection devices (small-package, bar-package, missing-bar-in-carton, five-wheel detection) is operating normally, along with rejection action information data. Specific manifestations include:
- The software sends rejected image data to the console.
- The software sends all image data to the console.
- The software sends all statistical data (including brand, date, time, unit information, etc.) to the console.
Leveraging the factory intranet server, when the monitoring software of detection equipment generates fault information data, it is transmitted to the server, triggering on-site alarms via the factory intranet server. Fault information data is also remotely alerted via PC and mobile terminals. Issues such as software crashes, camera disconnections, camera failure to capture images, faulty烟包到位检测 sensors, failure to receive defect images, and rejection device malfunctions trigger warning pop-ups on PC and mobile interfaces. The alarm page displays device fault information, location, occurrence time, and handling records.
3.3 Implementing Product Quality Early Warning Control
By analyzing detection data from the equipment, early warnings are issued when the number of defective cigarette packets exceeds thresholds or abnormal defect frequencies occur. The quality warning function alerts maintenance personnel to adjust or repair relevant parts of the main production equipment, promptly eliminating quality defects and preventing deterioration.
Data from small-package detection devices, five-wheel detection devices, missing-bar-in-carton detection devices, and bar-package detection devices are analyzed based on quality defect image name information (including the time of defect occurrence, quantity of defective products, and the camera location where the defect was detected). A product defect warning is issued when the defect count exceeds the warning threshold.
By analyzing the time and quantity of defective products, the frequency of defects over a certain period and long-term trends can be statistically analyzed. This provides a basis for equipment evaluation management, timely alerts maintenance personnel for adjustments, and enhances scientific maintenance management.
3.4 Centralized Management of Detection Equipment Status
Production management personnel (process quality staff, equipment managers) use the monitoring system to centrally compare and analyze the operational status of detection devices and product defect situations, achieving centralized management of detection equipment status. The detection equipment monitoring system can display real-time operational status, quality defect trends, and historical data statistical analysis for all detection equipment in the factory, enabling unified centralized management of all factory equipment.
Comprehensive historical fault records can analyze the proportion of faulty units, fault types, faulty equipment, and peak fault times. Planned maintenance management is implemented for units, fault types, and equipment with frequent failures to prevent occurrences.
4 Conclusion
In summary, the equipment detection system in the cigarette manufacturing workshop of a tobacco factory requires real-time online monitoring to ensure the operational status of detection devices is tracked, providing alarms and fault localization. This reduces during the production process of cigarette packets, ensures smooth production operations, and improves production efficiency.
