Switchgear monitoring system and fiber optic temperature measurement, complete guide

This report provides a detailed analysis of switchgear monitoring practices, with a particular emphasis on the critical role of temperature monitoring. We explore various monitoring technologies, best practices, and the benefits of implementing a comprehensive monitoring strategy. The advantages of FJINNO's fluorescence fiber optic sensors are highlighted.

1. Switchgear Monitoring Overview

Switchgear plays a vital role in power systems, responsible for controlling, protecting, and isolating electrical equipment of different voltage levels (low, medium, and high voltage). Switchgear acts as the "traffic controller" of the power system, connecting or disconnecting circuits as needed and providing protection in the event of a fault. Based on voltage levels, switchgear can be categorized into low-voltage switchgear (below 1 kV), medium-voltage switchgear (1 kV to 38 kV), and high-voltage switchgear (38 kV up to 545 kV transmission voltage). Furthermore, based on insulation methods, it can be divided into air-insulated switchgear (AIS) and gas-insulated switchgear (GIS), among others.

A typical switchgear assembly includes key components such as a metal enclosure, busbars, insulators, circuit breakers, instrument transformers, relays, and metering devices. The diversity of switchgear types and voltage levels means that monitoring requirements and complexity can vary significantly depending on the application. For example, high-voltage and gas-insulated switchgear may have stricter monitoring requirements for gas leaks and insulation performance.

Monitoring switchgear is crucial for ensuring the safe and reliable operation of the power system. By continuously tracking the performance and condition of switchgear, potential problems can be identified early. Early detection allows for preventative maintenance, minimizing downtime and costly repairs. Compared to traditional periodic maintenance, monitoring based on actual equipment condition optimizes maintenance schedules, leading to more efficient maintenance strategies. Furthermore, switchgear monitoring helps reduce the labor intensity of manual inspections and can predict the mechanical life trend of the switchgear, providing a basis for proactive equipment replacement and ultimately achieving cost savings. With technological advancements, modern switchgear monitoring systems can even detect unauthorized intrusions, enhancing the overall security of the power infrastructure. Continuous monitoring also helps meet relevant regulatory requirements.

From passively responding to failures to actively predicting and preventing them, this shift reflects a profound change in modern industry's approach to equipment management. Data-driven decision-making is becoming key to ensuring the stable operation of power systems.

Among the many monitoring parameters, temperature is a critical indicator. Thermal stress, or overheating, is a major factor in the degradation of insulating materials, affecting the efficiency and reliability of switchgear. Rising temperatures can lead to thermal runaway, resulting in severe consequences such as burning, melting, and component damage. By monitoring temperature, hot spots in critical areas such as busbar connections, circuit breaker contacts, and cable terminations can be effectively identified. Focusing on temperature monitoring indicates that temperature is an early warning sign of many common switchgear failures and a key aspect of assessing the overall health of the equipment. Increased resistance due to electrical connections or insulation aging often generates heat. If left unchecked, this heat can further accelerate component aging, creating a vicious cycle that can eventually lead to equipment failure.

2. Comprehensive Monitoring of Switchgear

Here are the main components and areas of switchgear that require monitoring:

Gas Monitoring (for Gas-Insulated Switchgear - GIS):

• Sulfur Hexafluoride (SF6) Leakage: Early detection and prevention of gas leaks in high-voltage SF6-insulated switchgear are crucial for reducing gas emissions and lowering maintenance costs.
• Humidity: Monitoring humidity in SF6; excessive humidity can affect its insulation strength and potentially lead to flashovers and corrosion.
• Pressure: Real-time pressure readings are essential for monitoring the integrity of GIS circuit breakers and operating busbars, helping to predict leak rates.

Circuit Breaker Monitoring:

• Mechanical Performance: Monitoring the travel characteristics of closing and opening operations, such as opening and closing times, speed, and total travel, to identify performance degradation.
• Wear: Monitoring the number of fault operations and calculating contact wear to provide a basis for developing maintenance plans.
• Electrical Performance: Performing coil current analysis to reflect the health and operating status of the operating mechanism. Recording phase current waveforms during circuit breaker operation helps analyze its electrical characteristics.
• Energy Storage System: Monitoring the operating time of the motor/pump, the number of unprovoked starts, and the motor current curve and peak value to determine the wear of the energy storage system, leakage of the hydraulic system, and damage to the spring energy storage motor.

Isolating Switch and Grounding Switch Monitoring:

• Monitoring the status and operation of isolating switches and grounding switches to ensure that power can be safely isolated and grounded during equipment maintenance or fault conditions.

Heater Monitoring:

• Monitoring the operating status of heaters to prevent excessive humidity from affecting the internal insulation performance of the switchgear.

Internal Arc Fault Monitoring:

• Detecting internal fault arcs and locating the compartment where the arc occurred, assessing the impact of the arc on the gas insulation strength.

Partial Discharge (PD) Monitoring:

• Detecting and analyzing partial discharge activity to identify potential insulation problems.

Switchgear Operation Monitoring:

• Monitoring the type and position of switchgear operation, tracking its operating status, and obtaining information about its usage and potential wear.

Environmental Monitoring:

• Monitoring the ambient temperature and humidity inside the switchgear.

Physical Security Monitoring:

• Providing an intrusion detection system with real-time alerts for any unauthorized intrusion attempts, ensuring the physical security of electrical equipment.

Cable Connection Monitoring:

• Monitoring the condition of internal switchgear and feeder cables, especially for partial discharge and temperature anomalies, to prevent failures.

Other Parameter Monitoring:

• Monitoring the circuit breaker drive mechanism, oil quality and winding insulation, load and voltage.

3. In-depth Analysis of Switchgear Temperature Monitoring

Temperature monitoring is extremely important in switchgear monitoring. It enables early detection of potential problems, allowing for timely maintenance and minimizing downtime and costly repairs. With real-time temperature data, maintenance personnel can develop preventative maintenance plans based on the actual condition of the equipment, rather than following fixed time intervals.

Temperature monitoring also helps identify operational inefficiencies or anomalies. Addressing these issues promptly can improve switchgear performance and ensure it operates at optimal efficiency. Furthermore, regular temperature monitoring ensures long-term reliable and stable operation of the switchgear. Early detection and resolution of potential faults can reduce the risk of unexpected failures, thereby improving reliability and extending uptime. Proactive maintenance based on temperature monitoring data can extend the lifespan of switchgear. By addressing problems before they escalate, damage or deterioration can be mitigated, allowing the switchgear to operate for a longer period without requiring replacement. By minimizing downtime, optimizing performance, and extending the lifespan of switchgear, temperature monitoring can lead to significant cost savings for operators.

For high-voltage switchgear, temperature monitoring can effectively prevent safety hazards caused by equipment overheating. Studies have shown that 24/7 temperature monitoring can detect up to 70% more faults than periodic inspections, protecting valuable equipment from failure and improving personnel safety. Proper heater operation is crucial for ensuring reliable circuit breaker operation.

The numerous benefits of temperature monitoring make it a cornerstone of effective switchgear maintenance and reliability programs. Temperature is a fundamental indicator of electrical connection and insulation health, and continuous monitoring is invaluable.

Temperature anomalies are often precursors to more serious failures, so early detection is crucial to prevent catastrophic events. Temperature increases can be sudden and can lead to thermal runaway. Hot spots indicate potential problems at connection points (such as busbar connections, circuit breaker contacts, and cable terminations). Excessive current load on busbars can lead to overheating, especially in medium-voltage switchgear. Thermal stress reduces the performance of insulating materials, affecting efficiency and reliability. Poor electrical connections are a major cause of switchgear failures, equipment damage, fires, and even personal injury. Increased resistance in electrical connections generates heat, which, if left unchecked, can lead to insulation breakdown, arc faults, and fires.

In switchgear, there are many critical locations that require focused temperature monitoring, including the incoming and outgoing sides of air circuit breakers (ACBs), busbar connection points, the upper and lower contacts inside vacuum circuit breakers (VCBs) connected to the main busbar and feeder busbar circuits, disconnecting switches/isolators, connection points of current transformers (CTs), incoming cable/feeder terminations, connection points of the main busbar, electrical connection points of voltage transformers (VTs), cable terminations (especially in medium-voltage switchgear), the surface of high-voltage switchgear cabinets, cable or busbar connections of air circuit breakers in low-voltage switchgear, and power contacts in low-voltage switchgear modules. Identifying these specific critical monitoring points helps to efficiently deploy temperature sensors in a targeted manner. Focusing on high-risk areas most prone to overheating maximizes the effectiveness of the monitoring system.

4. Temperature Monitoring Technologies

Several technologies are currently available for temperature monitoring in switchgear, each with its own advantages and disadvantages.

Infrared (IR) Temperature Sensors:

Infrared (IR) temperature sensors are a non-contact measurement technology that can be used as an alternative to periodic readings with infrared thermometers. Their advantages include being intrinsically safe and immune to electromagnetic and radio frequency interference. However, IR sensors also have some limitations, such as requiring a direct line of sight to the target, and internal switchgear components often block the view. Insulating sleeves covering connection points also render IR measurements ineffective. Furthermore, the accuracy of IR measurements is not high, typically ±2°C to ±4°C at higher temperatures, and repeatability can be poor. Their sensing range is limited and they cannot measure temperatures below 0°C. Installation requires lens mounting brackets and wiring, and typically requires installing special black targets with known emissivity at the sensor location to improve reliability. Installation can be expensive and cumbersome due to the need for precise alignment and different lenses for different sensing distances. IR sensors are also susceptible to dust accumulation and changes in emissivity, and reflections of infrared energy emitted by surrounding objects and sudden changes in ambient temperature can also lead to measurement errors. While non-contact is an advantage of IR sensors, their limitations in line of sight and accuracy make them less suitable for continuous reliable monitoring in all switchgear applications. The complex internal structure of switchgear often hinders direct observation of critical connection points, and environmental factors can affect the accuracy of IR readings.

Fiber Optic Temperature Sensors:

Fiber optic temperature sensors make direct contact with the measurement point via ring terminals or adhesive sensors. The optical fiber is made of durable plastic or glass and is intrinsically safe and immune to electrical events and noise. Fiber optic cables ensure that the sensors are immune to electromagnetic or radio frequency interference. The sensors can be installed under insulating sleeves for accurate, real-time measurements. Measurements are accurate and repeatable, with an accuracy better than ±1°C. Installation requires no calibration or maintenance, with a lifespan exceeding 20 years. The sensing range is wide (up to 200°C, and some systems even offer -271°C to +300°C). Installation is simple for both new and retrofit projects. Fiber optic sensors are cost-effective in terms of capital, installation, and operating costs. They have plug-and-play functionality and can be compatible with existing monitoring systems such as SCADA. Fiber optic sensors can also be used in high electric and magnetic field environments (up to 1200 kV).

Among fiber optic temperature sensors, fluorescence-based types have significant advantages. Fluorescence fiber optic temperature monitoring systems are based on calibration-free fluorescence decay technology, ensuring that the sensors do not require recalibration throughout their lifespan. Fluorescence probes are small in size and easy to install at measurement points, with high measurement accuracy and fast response frequency. The technology is immune to electromagnetic, microwave, and radio frequency interference, making it ideal for harsh environments such as high-voltage switchgear. FJINNO's fluorescence fiber optic temperature sensors are recommended, and their products are highly resistant to voltage and corrosion and can operate stably in complex industrial environments.

Distributed Fiber Optic Temperature Sensors:

Distributed fiber optic temperature sensors detect temperature at each point on the fiber optic cable, but their temperature range may be limited.

Fiber Bragg Grating (FBG) Temperature Sensors:

Fiber Bragg grating temperature sensors determine the temperature at multiple sensing points by detecting the shift in the Bragg wavelength, but their application temperature range may be limited.

Wireless Surface Acoustic Wave (SAW) Temperature Sensors:

Wireless surface acoustic wave (SAW) temperature sensors set up a component at the measurement point and a nearby wireless antenna to read the temperature. Their advantage is that they can eliminate the line-of-sight problem of infrared sensors. However, SAW sensors are susceptible to interference, have slow response speeds, are difficult and expensive to commission, and have limited transmission distances. These disadvantages suggest that SAW sensors may not be as reliable as other options for critical switchgear monitoring. Interference in high-voltage environments and slow response times can affect the ability of these sensors to detect rapid temperature changes.

Wireless (ZigBee) Temperature Sensors:

ABB offers STX wireless temperature sensors for low/medium-voltage switchgear, using ZigBee (Green Power) communication technology. These sensors are self-powered and battery-free, and can directly monitor the temperature of critical connection points. The advantage of wireless sensors is that they are easy to install, especially for retrofit projects. However, wireless technology is sometimes susceptible to interference in electrically noisy environments, which may require careful consideration of its reliability in specific switchgear applications. High electromagnetic fields generated during switching operations can affect the performance of wireless communication.

In summary, research materials indicate that fiber optic sensors are becoming a robust and reliable solution, especially for continuous monitoring of medium and high-voltage switchgear. Due to their limitations, infrared sensors are more suitable for periodic inspections rather than continuous monitoring. Wireless SAW sensors have significant disadvantages. Wireless ZigBee sensors, while convenient, may have potential concerns regarding reliability.

5. Requirements and Best Practices for Temperature Monitoring

For high-voltage switchgear, temperature sensors must be intrinsically safe and cannot pose a risk of short circuits, partial discharges, or arc flashes. Sensors should be reliable and immune to electromagnetic or radio frequency interference. Sensors should be highly durable, not degrade over time, and be able to last the entire lifespan of the equipment (20+ years). The monitoring system should have a short enough response time for operators to react in a timely manner. The solution should not require frequent calibration or compensation.

Fiber optic sensors are emphasized as meeting these stringent requirements for medium and high-voltage switchgear. Critical monitoring points include busbars, contacts, cable terminations, and cabinet surfaces. Best practices call for 24/7 thermal monitoring. Due to the high voltage and the serious consequences of failure, temperature monitoring requirements for high-voltage switchgear are very stringent, emphasizing the safety, reliability, and long-term stability of the monitoring system. Any failure of the monitoring system itself could lead to safety hazards or inaccurate data, so robust design and adherence to relevant standards are essential.

For low-voltage switchgear, the safety and reliability requirements are similar to those for high-voltage switchgear. The internal temperature of low-voltage switchgear should generally not exceed 50/55°C (when the ambient temperature is up to 25°C) or rise by 10/15K at a maximum ambient temperature of 40°C. Heat sources inside low-voltage switchgear include heat generated by copper parts and cables, heat generated by equipment, and heat generated by eddy currents and magnetic losses. Natural or forced ventilation may be required to control temperature rise. Low-voltage switchgear can use continuous thermal monitoring solutions to provide 24/7 temperature values for critical connection points throughout the device. Monitoring temperature trends over time helps identify faulty connections. Wireless temperature sensors are used to monitor critical joints in low-voltage switchgear. Due to lower currents but higher flow rates, temperatures in low-voltage equipment can often be higher than in high-voltage switchgear.

While the basic requirements for temperature monitoring at different voltage levels are similar, the specific temperature limits and heat dissipation strategies differ due to the unique characteristics and applications of low-voltage switchgear. Lower voltage does not necessarily mean a lower risk of overheating, as factors such as higher current flow and enclosure design also play a significant role.

Key factors to consider when selecting sensors include: intrinsic safety (no risk of electrical events), reliability (no interference), high durability (long lifespan), accuracy, ease of monitoring (compatibility with existing systems), ease of installation (suitable for new and retrofit projects), cost-effectiveness (including acquisition and operating costs), sufficient response time, and no need for frequent calibration. In addition, relevant industry standards (such as IEEE C37.20.3) should be met. A comprehensive assessment of these criteria is essential to selecting the most appropriate temperature monitoring technology for a given switchgear application. Different technologies have advantages and disadvantages in terms of performance, cost, and ease of use, and the specific operating environment and monitoring objectives need to be carefully considered.

Continuous (24/7) monitoring is now considered best practice and can detect more faults than periodic inspections. Periodic visual inspections are costly, require special safety considerations, and may not detect problems in a timely manner. The trend is clearly towards continuous monitoring to provide real-time insights into switchgear health and enable proactive maintenance. Intermittent problems or rapidly developing faults may be missed during periodic inspections, so continuous monitoring is essential for early detection and prevention.

Relevant industry standards include IEEE Std. C37.20.3, which is the testing standard that switchgear should meet, and temperature monitoring systems should also comply with this standard. IEEE Std. C37.20.9 covers metal-enclosed switchgear containing gas-insulated systems. IEC 62271-200 is the standard for high-voltage switchgear and controlgear. IEC 62271-1 and IEEE C37.100.1 define normal indoor operating conditions, including temperature limits (40°C to -25/30°C) and average air temperature (. The IEEE standard requires a maximum temperature rise of 65°C for thermal characteristics, while the IEC standard is 75°C. BS EN 60439 specifies temperature limits for low-voltage switchgear. Adherence to relevant IEC and IEEE standards ensures that switchgear and its monitoring systems meet recognized safety and performance benchmarks. These standards provide guidance for design, testing, and operation, helping to improve the overall reliability and safety of power systems.

6. Analysis and Application of Temperature Data

Temperature data is collected by sensors installed at critical points. The system collects the data and converts it into diagnostic information. Data analysis includes threshold monitoring (setting alarm limits), trend analysis (tracking changes over time) to identify developing problems, comparison with historical data to detect anomalies, and correlation with other monitoring parameters (such as circuit breaker status and partial discharge) for comprehensive assessment. Software can provide temperature history curves for analysis. Effective analysis of temperature data requires not only collecting raw readings but also processing and interpreting them to extract meaningful insights about the condition of the switchgear. Simply relying on simple temperature readings may not be sufficient; analyzing trends, deviations from normal values, and correlations with other parameters can more accurately reflect the health of the equipment.

By identifying abnormal temperature patterns, potential failures can be predicted before they occur, enabling proactive maintenance. Maintenance can be scheduled based on the actual condition of the equipment rather than fixed time intervals, optimizing maintenance efforts and reducing unexpected failures. Real-time data enables timely intervention, preventing failures and extending equipment lifespan. Maintenance personnel can remotely view real-time data and temperature curves.

Temperature monitoring is a key enabler of condition-based maintenance, which can lead to more efficient and effective maintenance strategies, reducing costs and improving reliability. By focusing maintenance efforts on equipment that actually needs maintenance, resources can be used more effectively, and the risk of premature failures and unnecessary maintenance can be minimized.

Temperature thresholds can be set to trigger alarms and warnings when these thresholds are exceeded. Alarms can take many forms, such as pop-up alarms, voice alarms, and text message notifications. Some systems use indicators to display temperature status. Continuous thermal monitoring systems can include door-mounted indicators to display healthy, pre-warning, and alarm conditions. A robust alarm and warning system based on temperature data is crucial for alerting personnel to potential problems and taking timely corrective action. Timely alerts enable operators to investigate and address problems, preventing them from escalating into more serious failures or safety hazards.

Temperature data should be analyzed in conjunction with other parameters (such as partial discharge, circuit breaker operation, and gas pressure) for a comprehensive assessment of switchgear health. Some systems correlate operational dynamics with partial discharge data. Some systems integrate data from protection relays and temperature sensors. A comprehensive condition monitoring system integrates data from multiple sources for a more complete and accurate understanding of the overall health of the switchgear and potential failure modes. Different parameters can provide complementary information, and analyzing them together can reveal complex interrelationships and improve diagnostic accuracy.

7. Components of a Temperature Monitoring System

A typical switchgear temperature monitoring system includes the following key components:

Temperature Sensors:

Used to measure the temperature of critical points in the switchgear. Different types of sensors can be selected based on different application requirements, such as fiber optic probes for direct contact measurement (with various fasteners such as ring terminals, glue), wireless temperature sensors (such as ZigBee) for easy installation, and temperature and humidity sensors for monitoring environmental conditions. The choice of sensor depends on the specific application requirements, including voltage level, accessibility of monitoring points, and required accuracy. Different sensor technologies have their own advantages and disadvantages, and choosing the right sensor is crucial for obtaining reliable data.

Temperature Transmitter/Signal Conditioner:

Used to convert the sensor's signal into a format that can be used by the data acquisition system. Some systems offer DIN rail-mounted transmitters. Some systems include light sources, optical couplers, and spectrometers for fiber optic sensors. The transmitter is crucial for signal processing and ensuring compatibility with monitoring and control systems. Raw sensor signals typically need to be conditioned and converted to a standardized format for further processing and analysis.

Data Acquisition Unit/Monitoring Device:

Responsible for collecting and storing temperature data from the transmitter. Some systems are monitoring and diagnostic units. Some systems act as monitors. Some systems include electronics for data processing, storage, and visualization. These units are the central hub for collecting and managing temperature monitoring data. Reliable data acquisition is the foundation of the entire monitoring process, ensuring that accurate and timely information is available for analysis and decision-making.

Software and Communication Interface:

For data visualization, trend analysis, alarm management, etc. Communication interfaces include ports such as Ethernet, USB, and RS-485, and protocols such as Modbus, for integration with SCADA and other systems. Some systems also offer mobile applications for remote viewing of device health and cloud-based dashboards for remote monitoring and diagnostics. Dry contacts can be used to indicate monitor health and alarm conditions. User-friendly software and robust communication interfaces are essential for effectively accessing, interpreting, and utilizing temperature monitoring data. The value of a monitoring system is significantly enhanced by tools that allow users to easily understand the data and integrate it with existing infrastructure.

8. Conclusion and Recommendations

Temperature monitoring is a crucial part of switchgear monitoring, and by enabling early fault detection and preventative maintenance, it is essential for ensuring the safe, reliable, and long-life operation of the power system.

Based on the above analysis, the following recommendations are made:

• For critical high-voltage and medium-voltage switchgear, a continuous temperature monitoring system should be implemented to proactively identify potential problems.
• Carefully evaluate different temperature monitoring technologies based on the specific requirements of the switchgear (voltage level, environment, importance), and prioritize solutions that are intrinsically safe, reliable, and accurate. For demanding applications, fiber optic sensors should be considered.
• Ensure that the selected temperature monitoring system complies with relevant industry standards (IEC, IEEE) to ensure safety and performance.
• Integrate temperature monitoring data with other switchgear monitoring parameters (such as partial discharge, circuit breaker operation) for a comprehensive condition assessment.
• Establish appropriate temperature thresholds and alarm systems to promptly alert personnel to abnormal conditions for intervention.
• Utilize data analysis tools to identify temperature trends and patterns to develop predictive maintenance strategies and optimize maintenance schedules.
• For low-voltage switchgear, continuous thermal monitoring options should be considered, and attention should be paid to internal temperature limits and heat dissipation requirements.
• Regularly inspect and maintain the temperature monitoring system to ensure its continued accuracy and reliability.

Table 1: Comparison of Temperature Monitoring Technologies

Technology	Advantages	Limitations	Suitable for Continuous Monitoring?	Typical Applications
Infrared (IR) Temperature Sensors	Non-contact, intrinsically safe, no EMI/RFI	Requires line of sight, susceptible to obstruction, lower accuracy, poorer repeatability, limited sensing range, susceptible to environmental factors	No, better suited for periodic inspections	Periodic inspections, locations where sensor installation is difficult
Fiber Optic Temperature Sensors	Direct contact, intrinsically safe, EMI/RFI immunity, high accuracy, good repeatability, long lifespan, wide temperature range (-40°C to 150°C), easy installation	Requires shutdown for installation	Yes	Medium and high-voltage switchgear, applications requiring high accuracy and long-term reliability
Wireless Surface Acoustic Wave (SAW) Temperature Sensors	No line-of-sight limitations	Susceptible to interference, slow response, complex and expensive commissioning, limited transmission distance	No	Specific application scenarios, but overall applicability is not strong
Wireless (ZigBee) Temperature Sensors	Easy installation	May be susceptible to electromagnetic interference	Yes, but reliability needs to be considered	Low/medium-voltage switchgear, retrofit projects

Table 2: Key Temperature Monitoring Points in Switchgear

Switchgear Component	Potential Temperature Issues	Recommended Monitoring Technology
Air Circuit Breaker (ACB) Incoming/Outgoing Side	Poor connection, overload	Fiber Optic Temperature Sensor
Busbar Connection Points	Loose connection, oxidation	Fiber Optic Temperature Sensor
Vacuum Circuit Breaker (VCB) Internal Contacts	Contact aging, wear	Fiber Optic Temperature Sensor
Disconnecting Switch/Isolator	Poor contact	Fiber Optic Temperature Sensor
Current Transformer (CT) Connection Points	Loose connection, overload	Fiber Optic Temperature Sensor
Incoming Cable/Feeder Terminations	Poor connection, aging	Fiber Optic Temperature Sensor
Main Busbar Connection Points	Loose connection, oxidation	Fiber Optic Temperature Sensor
Voltage Transformer (VT) Electrical Connection Points	Poor connection	Fiber Optic Temperature Sensor
Cable Terminations (Medium Voltage)	Poor connection, insulation aging	Fiber Optic Temperature Sensor
High-Voltage Switchgear Cabinet Surface	Internal overheating	Infrared Temperature Sensor (supplementary)
Low-Voltage Air Circuit Breaker Cable/Busbar Connections	Poor connection, overload	Wireless Temperature Sensor / Fiber Optic Temperature Sensor
Low-Voltage Switchgear Power Contacts	Poor contact, aging	Wireless Temperature Sensor / Fiber Optic Temperature Sensor