During the operation of high-voltage switch cabinets, excessive heat generation at bus connection points, cabinet internal contact points, and circuitry of moving and stationary contacts can easily lead to fire and power outage accidents. Therefore, it is crucial to monitor the temperature within high-voltage switch cabinets. Conventional temperature monitoring methods are insufficient to address insulation issues in high-voltage equipment due to the presence of exposed voltages. The wireless temperature monitoring system, which transmits information via radio waves, eliminates the need for wiring, the use of high-voltage equipment, and the requirement for insulation measures. It effectively resolves temperature monitoring issues in high-voltage equipment. This article analyzes and discusses the design and implementation of a wireless temperature measurement system for high-voltage switch cabinets.
The Importance of Designing a Non-Contact Temperature Measurement System
The 10kV high-voltage switchgear is an indispensable part of the power system, with its safe operation being a crucial guarantee for user load. High-voltage switchgears are characterized by high load currents and a tendency to overheat, necessitating regular temperature measurements. In terms of structural form, the 10kV high-voltage switchgear is divided into two types: the rotating knife switch type and the trolley type. The trolley-type high-voltage switchgear, due to its completely sealed contacts, cannot be observed or measured externally, so patrol personnel can only indirectly infer internal overheating by measuring the cabinet wall temperature. The transmission loss of temperature causes the accuracy to be extremely low and fails to detect subtle changes, which does not meet the requirements for safe operation.
Design Principle of a Wireless Temperature Measurement System for High-Voltage Switchgear Cabinets
2.1 Main Components of the System
The wireless temperature measurement system is composed of wireless temperature sensors, wireless temperature monitors, a control room master computer, and communication links. The wireless temperature sensors are primarily installed on switchgear panels to collect and process data from various sub-sensors, and store it. All wireless temperature monitoring instruments communicate with the control room master computer via the RS485 bus, thereby forming a distributed monitoring system.
2.2 Wireless Temperature Sensor
Wireless temperature sensors are primarily used to measure the surface temperature of live objects, such as monitoring the operating temperature of busbar connections and exposed electrical contacts in high-voltage switch cabinets. These sensors consist of a measuring circuit, temperature sensor, wireless modulation interface, logic control circuit, and power supply circuit, transmitting temperature signals to the wireless temperature monitor via a wireless network. Due to their compact size, wireless temperature sensors are ideal for measuring thermal contacts within switch cabinets, enabling the measurement of operating temperatures at cable joints, contacts, and busbar connection points.
2.3 Wireless Temperature Monitor
The Wireless Temperature Monitor primarily serves for data collection, storage, processing, and alarm signal output for temperature sensors, with communication between the control room PC and the RS485. The LCD human-machine interface is mainly used for displaying current wireless sensor temperature monitoring information and temperature data. Field users can control it through input and output operations, such as querying and setting the wireless sensors, while the Wireless Temperature Monitor can be used for running log queries and configurations.
2.4 EMI Resistance
During the design process, wireless sensors are placed on the contact arms near the switch terminals and junction surfaces of the busbar. When there is a high current flowing through the contact arms and busbar, a significant electromagnetic field is generated, which can affect the normal operation of the sensors. To ensure the proper functioning of the wireless sensors, shielding measures must be implemented. In addition to connecting the antenna externally during system design, circuits need to be arranged within the shielding box to reduce the impact of electromagnetic radiation during operation. Temperature sensors are arranged on the heat-sinking plate, and the remaining space in the other shielding boxes is filled with sealant. To ensure good insulation, the sensors must be wrapped with heat-shrink tubing.
Figure 1 illustrates the structural composition of a wireless temperature measurement system for a trolley-type switchgear, including a temperature sensor (2) mounted on the trolley's moving contact sleeve (1) and a current sensor (4) mounted on the terminal box module (3). Both the temperature sensor (2) and the current sensor (4) are connected to a data receiving processor (5), which is electrically connected to a display screen (7) mounted on the trolley-type switchgear (6). The data receiving processor (5) is also connected to a communication module (8), which in turn is connected to a remote alarm unit (9). The remote alarm unit (9) is electrically connected to terminal equipment. The data receiving processor (5) comprises an electrically interconnected data receiving unit (10) and a data processing unit (11). Additionally, the data receiving unit (10) includes a temperature data receiving unit and a current data receiving unit, both of which are connected to the data processing unit (11). The data processing unit (11) is connected to the communication module (8). Furthermore, the temperature sensor (2) is a bonded temperature sensor, mounted on the trolley's moving contact sleeve (1). The temperature sensor (2) is an insulated temperature sensor.
Actual Application of the Wireless Temperature Measurement System for High-Voltage Small Cars Switch Cabinets
In this technical solution, the temperature of the moving contact of the trolley is measured through the configuration of a temperature sensor, and the current flowing through the moving contact is measured through the configuration of a current sensor. The data receiver processor is set up to receive both temperature and current data, and it evaluates the correlation between the current and temperature data to ensure measurement accuracy, thus preventing false alarms from the remotely connected alarm unit via the communication module. Additionally, the trolley-style switchgear is equipped with a display screen, which can real-time show current and temperature data, facilitating maintenance personnel to monitor the screen and promptly understand the heating and current conditions of the moving contact within the trolley-style switchgear, ensuring its safe operation. Furthermore, the remote alarm unit is connected to terminal devices, which can be smartphones or other devices, making it convenient for maintenance personnel to promptly grasp the operational status of the trolley-style switchgear through these terminal devices.
The data receiving and processing unit includes inter-connected data receiving and processing modules. In this technical solution, the data receiving module is capable of receiving data measured by temperature and current sensors; the processing module can determine if the current and its corresponding temperature are within the normal range. If the current exceeds a certain value and the temperature is beyond the set threshold, the processing module will send the judgment instructions and the received current and temperature data to the communication module.
The data receiving unit includes a temperature data receiving unit and an electrical current data receiving unit, both of which are connected to the data processing unit separately. In this technical solution, the data processing unit can handle the electrical current data received by the electrical current data receiving unit and the temperature data received by the temperature data receiving unit, and then transmit the processed commands, current data, and temperature data to the communication module.
The data processing unit is connected to the communication module. In this technical solution, the communication module can send the instructions, current data, and temperature data processed by the data processing unit to the remote alarm unit. The temperature sensor is a bonded temperature sensor, which is fitted onto the moving contact sleeve of the trolley. The bonded temperature sensor can be adjusted according to the diameter of the trolley contact sleeve, facilitating the installation of the temperature sensor on trolleys of different specifications. The temperature sensor uses an insulated temperature sensor. This setup allows the temperature sensor to be as close as possible to the trolley contact, obtaining a more accurate temperature reading. It also prevents the current passing through the trolley contact from affecting the temperature sensor, ensuring the accuracy of the temperature measurement.
Ankorri Online Temperature Monitoring System 4
4.1 Overview
The electrical contact online temperature measuring device is suitable for monitoring the temperature of equipment such as cable joints, circuit breaker contacts, knife switches, high-voltage cable mid-sections, dry transformers, and low-voltage high-current devices within both high and low voltage switchgear cabinets. It prevents potential safety hazards caused by overheating due to oxidation, loosening, and dust, which can lead to excessive contact resistance. This device enhances equipment safety, ensures timely, continuous, and accurate reflection of equipment operation status, and reduces the rate of equipment accidents.
The Acrel-2000T Wireless Temperature Monitoring System communicates directly with equipment at the bay level via RS 485 bus or Ethernet. The system design adheres to international standards such as Modbus-RTU and Modbus-TCP, enhancing its security, reliability, and openness. The system features remote signaling, measurement, control, adjustment, setup, event alarms, curves, bar graphs, reports, and user management. It can monitor the operational status of wireless temperature measurement system devices, enabling rapid alarm response and preventing severe faults.
4.2 Application Sites
Temperature monitoring suitable for power equipment in various industries such as ubiquitous power Internet of Things, steel mills, chemical plants, cement factories, data centers, airports, power plants, coal mines, and transformation and distribution substations.
4.3 System Structure
Temperature Online Monitoring System Schematic Diagram
4.4 System Features
The Acrel-2000T temperature monitoring system is installed in the duty monitoring room, enabling remote monitoring of the operating temperatures of all switch devices within the system. The system boasts the following main functions:
1) Temperature Display: Shows the real-time values of each temperature sensing point within the power distribution system, and allows for remote data viewing via computer WEB or mobile APP.
2) Temperature Trend Curves: View the temperature trend curves for each temperature sensing point.
3) Operational Reports: Query and print temperature data at various temperature sensing points.
4) Real-time Alerts: The system can issue alerts for abnormal temperatures at various temperature measurement points. It features real-time voice alarm capabilities, enabling voice alerts for all events. Alerts can be delivered through pop-ups, voice alarms, and also via SMS or APP push notifications to promptly remind on-duty staff.
5) Historical Event Inquiry: Capable of storing and managing records of events like temperature limits, facilitating users to trace historical system events and alarms, and conduct inquiries, statistics, and accident analysis.
4.5 Hardware Configuration for System 4.5
The temperature online monitoring system is primarily composed of temperature sensors and temperature collection/display units at the equipment layer, edge computing gateways at the communication layer, and a temperature measurement system host at the station control layer, enabling real-time monitoring of critical electrical components in the power distribution and transformation system.
5 Conclusion
In summary, this wireless temperature measurement system is designed for use with mobile switchgear. Through the configuration of current and temperature sensors, it reflects the relationship between current and temperature, ensuring the reliability of the temperature data of the switchgear's moving contacts and the current data passing through them. With the setup of a data receiver processor, it can determine when the temperature data exceeds the set threshold under a constant current value, at which point the processor sends instructions, temperature, and current data to the communication module. The communication module then forwards the received data to the remote alarm unit, facilitating real-time remote monitoring of the switchgear's moving contacts. The system also features a display setup on the mobile switchgear to promptly show temperature and current information, making it easier for maintenance personnel to observe and understand the operational status of the moving contacts within the switchgear, thereby ensuring their safe operation.
