10kV High Voltage Switchgear Online Temperature Measurement System

Tang Xueyang

Ankerui Electric Co., Ltd. Shanghai Jiading 201801

Abstract:High voltage switchgear plays an important role in the operation of the power system, providing on/off, control, and protection during power generation, transmission, energy conversion, and consumption processes. As a critical electrical equipment, the safe operation of high-voltage switchgear is related to the operational efficiency of the entire power system.

Keywords: intelligent substation; 10kV high voltage switchgear; Temperature measurement technology

The function of online temperature measurement

Due to the universality of the structure of high-voltage switchgear, whether it is XGN or KYN type switchgear, the equipment configured by different manufacturers is basically consistent in architecture, and is also very similar in configuration, function, and structure. Therefore, there are many rules to follow in terms of heating of switchgear.

Through careful analysis of the actual heating situation of the switchgear, it was found that the heating faults mainly occurred in the knife switch joints and cable joints inside the switchgear. Therefore, the temperature measurement of the switchgear only needs to focus on certain key points, and the attention to other parts can be reduced. When the temperature rises, the changes in key points should be monitored in a timely and correct manner. A warning should be issued before the temperature exceeds the allowable limit to ensure that the operation and maintenance unit has sufficient time to prepare and take appropriate protective measures in a timely manner to avoid accidents.

Characteristics of online temperature measurement for 2 10kV high-voltage switchgear

2.1 Non contact temperature measurement technology is difficult to meet the requirements

Taking XGN and KYN switchgear, which are currently widely used, as an example, they contain electrical components such as circuit breakers, isolating switches, CTs, and cable heads inside. In order to avoid pollution flashover accidents caused by accumulation of dirt and moisture, as well as to prevent short circuits caused by small animals entering by mistake, the conductive parts inside the high-voltage switchgear are often insulated and heat shrink sealed. That is, almost all the parts inside the switchgear that need to be temperature measured are wrapped with insulation, making it difficult for infrared temperature measurement technology to play a role.

2.2 Temperature measuring devices require high voltage insulation

Under normal operation, the rated voltage of the 10kV high-voltage switchgear is 10kV. The temperature measuring device is installed on the live equipment at the temperature measuring point, while the temperature signal receiving device is located on or outside the switchgear body. This means that high-voltage isolation is required between the temperature measuring device and the receiving device, while also not affecting the safe distance of electrical components inside the switchgear. This can be said to be the primary issue that needs to be addressed when applying switchgear temperature measurement technology in practice, and it is also an important factor affecting the development of online temperature measurement technology.

2.3 Cannot affect the performance of existing electrical components inside the switchgear

Many electrical components inside the 10kV high-voltage switchgear need to be operated according to their operating mode, such as circuit breakers, isolating switches, etc. This requires that the installation and operation of online temperature measuring devices should not affect the performance of the existing electrical components inside the switchgear.

2.4 It should be able to adapt to the harsh working environment inside the switchgear

Due to the fully sealed structure of the 10kV high-voltage switchgear currently in use, the ventilation inside the switchgear is poor and the temperature is high; In addition, the working current of high-voltage switchgear is in the hundreds of amperes, and it is located in an environment with severe electromagnetic interference such as substations. Therefore, online temperature measurement technology is required to have good anti-interference ability to ensure the reliability of temperature measurement data.

Research Status of Online Temperature Measurement Technology for 3 10kV High Voltage Switchgear

3.1 Infrared temperature measurement method

One of the most representative direct contact measurement methods is infrared thermometry. The infrared temperature measurement method is mainly based on the black radiation principle proposed by Stefan Boltzmann, Planck, and others. A blackbody is an idealized radiator that can emit the same electromagnetic spectrum at the same temperature, regardless of its specific composition and shape characteristics. The temperature of an object's surface is closely related to the size and wavelength distribution of its infrared radiation energy. By measuring the infrared radiation energy of the object itself, the surface temperature can be determined. The basic components of current infrared thermometers are the optical system, infrared detector, signal amplifier, signal processing, and display output. The core element is the infrared detector, which can convert incident infrared radiation into other forms of electrical signals that can be measured. After being calculated and corrected by the amplifier and signal processor circuit according to the internal algorithm of the instrument, it is converted into the temperature value of the measured target, and then displayed on the optical system.

3.2 Wireless Temperature Measurement Method

Wireless temperature measurement method is an improvement of contact temperature measurement method, which is a new type of temperature measurement method developed to isolate high and low voltage between temperature measurement equipment and power system. A typical wireless temperature measurement system consists of distributed temperature measurement points, data receivers, and backend processing systems. Distributed temperature measurement points are directly installed at the location where temperature measurement is required, and the data receiver is placed at a certain distance from the switchgear. The transmission of data between the distributed temperature measurement points and the data receiver is achieved through wireless communication, thus realizing the isolation of high voltage and the collection of temperature measurement data, solving the problem of difficult monitoring of contact operating temperature in high voltage switchgear by infrared temperature measurement method. Although wireless temperature measurement method solves the safety problem of temperature measurement devices, many problems have also been found in practical applications, among which the problem is the stability of the temperature measurement device at the switch contact position. In practical applications, the power supply used by this module is a current induction power supply that obtains energy from the power line, and the size of the power line load determines the amount of energy obtained by the power supply, which varies greatly. Therefore, the module often experiences insufficient power supply. Some people suggest using batteries and reducing the power consumption of temperature measurement devices to address this issue. However, the drawback is that batteries need to be replaced regularly after consumption, and electromagnetic interference may occur due to low wireless transmission power, resulting in errors in temperature measurement data transmission. Replacing the device battery requires the high-voltage switchgear to stop supplying power, which cannot meet the requirements for continuous operation of the high-voltage switchgear.

3.3 Fiber optic temperature measurement method

With the development of fiber optic communication and integrated optical technology, fiber optic sensing technology has shown remarkable activity in the field of sensors. Unlike traditional sensing technology, the advantage of fiber optic sensors is not their functional characteristics, but their own physical properties. Because fiber optic sensors have the advantages of light fiber weight, thin diameter, resistance to electromagnetic interference, corrosion resistance, high temperature resistance, low signal attenuation, and integration of information sensing and transmission, they can solve some measurement problems that conventional detection techniques cannot solve. Firstly, as optical fibers are excellent insulation materials, they isolate the high voltage between the power system and measurement equipment, thereby avoiding equipment safety accidents caused by temperature measurement devices. At the same time, using optical fibers as carriers for transmission and sensing signals solves the problem of strong electromagnetic interference in data transmission in the power system environment, making measurement results more accurate. Secondly, due to its good flexibility, small diameter, and light weight, optical fibers can detect areas that conventional sensors cannot reach. These advantages make fiber optic sensors stand out in temperature measurement in power systems and can be used as the main means suitable for temperature measurement in high-voltage switchgear.

Countermeasures for Abnormal Heating of 4 10kV High Voltage Switchgear

4.1 Emphasize the preventive testing work of 10kV high-voltage switchgear

We should attach importance to the preventive testing of 10kV high-voltage switchgear and its internal switchgear. Through preventive testing, the actual operation of the high-voltage switchgear can be reliably judged. When conducting preventive trials, it is necessary to strictly follow the corresponding regulations and specifications. If there are abnormalities in the data obtained during the trial, scientific and reasonable analysis should be conducted, and compared with previous preventive trial data to draw convincing conclusions. It is worth noting that the conclusion cannot be solely based on a set of data obtained, and multiple data should be combined to judge and determine the hidden dangers of high-voltage switchgear. After completing the preventive test, promptly carry out the restoration work of the high-voltage switchgear. During the restoration process, special attention should be paid to the good contact of each contact point and contact surface inside the switchgear to avoid abnormal heating caused by poor contact.

4.2 Pay attention to the daily maintenance and upkeep of 10kV high-voltage switchgear

The improvement of operating efficiency and the reduction of failure rate of 10kV high-voltage switchgear cannot be achieved without daily maintenance and repair work. In actual maintenance and repair work, special attention should be paid to the maintenance and repair of the contacts of the internal switchgear, and regular inspections should be carried out. Firstly, it is necessary to ensure its structural stability and that the spring is not loose or detached; Secondly, it is necessary to check whether there are signs of oxidation and discoloration on the appearance of the contacts, as well as the smoothness of the surfaces of the contacts and contact blades. After completing the above inspection work, a layer of conductive paste specialized for the power industry needs to be applied to the contacts to effectively reduce the resistance value between the contacts, increase the conductivity of the internal switch equipment of the switchgear, and ensure the working efficiency and service life of the high-voltage switchgear and its internal switch devices.

4.3 Accelerate the development and upgrading of new technologies for 10kV high-voltage switchgear

With the continuous development of new technologies and the promotion and application of new products in the power industry, various important power equipment is showing an increasingly fast pace of upgrading. For 10kV high-voltage switchgear, it is important to keep up with the trend and accelerate the research and development of new technologies and updates. Specifically, it is necessary to vigorously apply the currently developed and advanced automatic control technology and new low resistivity materials in 10kV high-voltage switchgear. In addition, the operation and management departments of the 10kV distribution network in power enterprises should change their mindset and attach importance to the replacement of outdated 10kV high-voltage switchgear. They should realize that only new and reliable power equipment can better ensure the safe and reliable operation of the 10kV distribution network, while also bringing good economic and social benefits to the enterprise, which is the guarantee for the long-term safe operation of the power system.

4.4 Promote the application of online temperature monitoring technology for 10kV high-voltage switchgear

To promote the application of temperature online monitoring technology in 10kV high-voltage switchgear, although this technology has only begun to develop in recent years, its foundation is currently mature computer technology, detection technology, and automatic control technology. Moreover, practical research has shown that temperature online monitoring technology has good effects in the application of 10kV high-voltage switchgear, so it is worth further developing and promoting its application at an appropriate time. By online monitoring of the temperature of key equipment such as switch joints, contacts, busbars, connecting wires, and related accessories inside the high-voltage switchgear, operators can real-time control the operation of the 10kV high-voltage switchgear, respond promptly to abnormal temperature rises in the switchgear, and avoid the expansion of faults and more serious accidents.

5 Ankerui wireless temperature measurement system

5.1 System Structure

The Acrel-2000T wireless temperature monitoring system communicates directly with devices in the interval layer through RS485 bus or Ethernet. The system design follows international standards such as Modbus RTU and Modbus TCP transmission protocols, greatly improving safety, reliability, and openness. The system has functions such as remote signaling, telemetry, remote control, remote adjustment, remote setting, event alarm, curve, bar chart, report, and user management. It can monitor the operation status of wireless temperature measurement system equipment, achieve rapid alarm response, and prevent serious faults from occurring.

Suitable for temperature monitoring of power equipment in ubiquitous power Internet of Things, steel mills, chemical, cement, hospitals, airports, power plants, coal mines and other industrial enterprises, as well as substations and distribution stations.

Structure diagram of temperature online monitoring system

5.2 System Functions

The temperature measurement system host Acrel-2000T is installed in the duty monitoring room and can remotely monitor the operating temperature status of all switchgear in the system. The system has the following main functions:

1. Temperature display: Display real-time values of each temperature measurement point in the power distribution system, and also enable remote viewing of data through computer WEB/mobile APP.

Temperature curve: View the temperature trend curve of each temperature measurement point.

Run report: query and print temperature data for each temperature measurement point at different times.

Real time alarm: The system can issue alarms for abnormal temperatures at various temperature measurement points. The system has real-time voice alarm function, which can issue voice alarms for all events. The alarm methods include pop ups, voice alarms, etc. It can also push alarm messages through SMS/APP to remind duty personnel in a timely manner.

Historical event query: It can store and manage event records such as temperature exceeding limits, facilitating users to trace the history of system events and alarms, query statistics, accident analysis, etc.

5.3 System Hardware Configuration

The online temperature monitoring system is mainly composed of the temperature sensor and temperature acquisition/display unit on the equipment layer, the edge computing gateway on the communication layer and the host of the temperature measurement system on the station control layer, to realize the online temperature monitoring of key electrical parts of the power transformation and distribution system.

6 Conclusion

In order to ensure the safe and reliable operation of 10kV high-voltage switchgear in intelligent unmanned substations, with the continuous development and application of new technologies, the status maintenance technology of electrical equipment in intelligent substations will be widely used. At the same time, the online temperature measurement technology of 10kV high-voltage switchgear will also be further applied and promoted.

10kV High Voltage Switchgear Online Temperature Measurement System

10kV High Voltage Switchgear Online Temperature Measurement System