Steel mill continuous casting shops are typical environments with extreme high temperatures. Continuous casting machines, molders, and high-temperature steel billets continuously emit intense thermal radiation outward, causing the shop's ambient temperature to far exceed conventional factory standards year-round, with peak temperatures in some areas reaching over 60°C. For power distribution equipment located in close proximity to these heat sources, the combined effects of continuous heat exposure, convective heat waves, and dust-laden hot air can easily cause internal temperature rises in switchgear to exceed safe limits. This leads to a series of potential hazards, including accelerated insulation aging, contact overheating, false tripping of protective devices, and a drastic reduction in equipment lifespan. Unlike ordinary residential, general industrial, or mining applications, continuous casting operations in steel mills impose the most stringent specialized requirements on equipment heat dissipation, temperature rise margins, and heat-resistant structures. Among the various types of switchgear adapted for high-temperature heavy industrial environments, specifically optimized 24 kV switchgear and heat-resistant upgraded air-insulated switchgear (AIS)-thanks to their customized temperature-control structures-have become the mainstream choices for power distribution systems in continuous casting shops, effectively resolving the issue of excessive temperature rises caused by high-temperature thermal radiation.
Many power distribution failures in steel mills are not caused by defects in the equipment itself, but rather by secondary failures resulting from uncontrolled temperature rises in high-temperature environments. Conventional switchgear, which is not heat-resistant, remains in a heat-radiation environment for extended periods, causing internal temperature rises to consistently exceed limits. This disrupts the equipment's rated operating conditions and ultimately leads to issues such as tripping, insulation breakdown, and mechanical jamming. This article addresses real operational challenges in steel mill continuous casting shops, analyzes the hazards of high-temperature thermal radiation to power distribution equipment, compares the heat resistance capabilities of different types of switchgear, and focuses on practical temperature rise control solutions for 24 kV switchgear and air-insulated switchgear (AIS), providing actionable guidance for power distribution design in high-temperature heavy industrial environments.
1. How Severe Is Thermal Radiation in a Continuous Casting Shop? The Core Hazards of Excessive Temperature Rise in Switchgear
The hazards posed by high temperatures in a continuous casting shop differ from the typical stifling heat found in ordinary factory buildings; the core issue lies in the combined effect of continuous, intense thermal radiation and high-temperature convective heat transfer. The entire process-from billet straightening and cooling to cutting-releases heat continuously, with no effective cooling buffer space. Power distribution cabinets located in close proximity to heat sources are subjected to prolonged passive heating, causing their external casings to continuously heat up. Heat constantly conducts inward and accumulates, resulting in temperature rises of internal components, insulating parts, and contact systems that far exceed the limits permitted by national standards.
The hazards posed by excessive temperature rises are highly insidious and extremely destructive: First, insulation materials age due to prolonged exposure to high temperatures, causing insulation margins to decrease year by year, which can easily lead to phase-to-phase short circuits and ground fault discharges; second, high-temperature oxidation of copper busbars and connection contacts increases contact resistance, creating a vicious cycle where "the higher the temperature rise, the greater the resistance, and the more severe the heat generation"; Third, secondary protection components are disrupted by high temperatures, causing parameter drift and abnormal sensitivity, which leads to false tripping and failure to operate, directly affecting the continuous production of the continuous casting line.
Different types of switchgear exhibit significant variations in their tolerance to high-temperature operating conditions, and standard off-the-shelf equipment is completely unsuitable for the conditions in a continuous casting shop. Conventional air-insulated switchgear (AIS), if it retains a standard heat dissipation design, is prone to drawing in high-temperature air currents due to its open structure, leading to severe internal heat buildup. The 24 kV switchgear responsible for the shop's main power supply carries high load currents and generates significant heat; when combined with external heat radiation, the risk of temperature rise exceeding limits is even higher, necessitating specialized heat resistance and heat dissipation optimization.
2. Differences in Equipment Suitability: Performance Weaknesses and Strengths of the Two Main Types of Switchgear Under High-Temperature Conditions
The power distribution architecture in steel mill continuous casting shops primarily features a hierarchical layout with medium-voltage trunk lines and branch loads. The 24 kV switchgear and air-insulated switchgear (AIS) commonly used on-site have different structural characteristics; consequently, the causes of temperature rise and the directions for optimization also differ. These are the two types of switchgear best suited for heavy industry retrofits.
Air-insulated switchgear (AIS) employs an air-insulated, naturally ventilated design with an open structure and no sealed compartments, providing excellent heat dissipation under normal conditions. However, in the high-temperature environment of a continuous casting shop, the open ventilation structure continuously draws in hot air from the shop, and external heat radiation penetrates directly through the cabinet, causing heat to accumulate inside with no escape, resulting in continuous temperature buildup. Unmodified AIS equipment operating near heat sources in continuous casting lines for 3 to 5 years will develop issues such as insulation aging and blackened, oxidized contacts. It is suitable only for areas at the far end of the workshop with good heat dissipation; when located adjacent to heat sources, specialized thermal insulation and heat dissipation modifications are required.
As the core power supply equipment for continuous casting lines, 24 kV switchgear supports critical loads such as the main drive, cooling water systems, and dust collection systems. The equipment generates significant heat during operation, and when combined with intense external heat radiation, this dual heat source can easily cause temperature rises to exceed limits. While its enclosed cabinet structure effectively blocks external heat radiation, it also has the drawback of making it difficult for internal heat to dissipate. As such, it is a critical piece of equipment for temperature rise control under high-temperature operating conditions and a key target for power distribution upgrades in steel mills.
3. Core Temperature Control Solution: Four Key Technical Measures to Keep the Temperature Rise Inside the Switchgear Within a Safe Range
To ensure the stable operation of switchgear in the continuous casting shop's persistent thermal radiation environment, reliance on natural convection alone is insufficient. A systematic approach combining "thermal insulation and heat blocking + directed heat dissipation + heat source optimization + upgraded heat-resistant materials" is required to specifically address the temperature rise challenges faced by 24 kV switchgear and air-insulated switchgear (AIS), while meeting the high-temperature operational requirements of all types of switchgear.
1. External Thermal Insulation Structure to Block External Heat Radiation
To address the intense heat radiation characteristic of continuous casting shops, high-temperature-resistant thermal insulation baffles and reflective insulation layers are installed on the exterior of the switchgear. By utilizing the principle of thermal reflection to block infrared heat radiation, the efficiency with which the cabinet absorbs heat is significantly reduced. For 24 kV switchgear located near core heat sources such as steel billets and straightening machines, insulation protection on the front and sides of the cabinet is prioritized to block external heat from penetrating inward, thereby reducing the baseline temperature rise at the source. For open-type air-insulated switchgear (AIS), removable thermal insulation and dust-proof screens are installed to filter high-temperature airflow without compromising ventilation, thereby mitigating the impact of thermal radiation.
2. Zone-Specific, Directional Ventilation for Heat Dissipation to Prevent Heat Accumulation Inside the Cabinet
Moving away from the disorderly natural ventilation design of standard cabinets, we adopt a "cold air intake at the bottom, hot air exhaust at the top" directional convection cooling logic. Low-temperature air inlets are installed at the bottom of the cabinet, and powerful exhaust devices are added at the top to form a stable convection channel for heat exchange. Ventilation is optimized by zoning the circuit breaker compartment, busbar compartment, and cable compartment-areas where heat generation is concentrated in medium-voltage switchgear-to ensure rapid dissipation of heat generated by the equipment, prevent internal heat buildup, and completely resolve the issue of cumulative temperature rise in 24 kV switchgear under heavy-load conditions.
3. Comprehensive Upgrade to Heat-Resistant Materials to Increase the Equipment's High-Temperature Tolerance Margin
Insulation components, seals, and secondary components within the cabinet have been upgraded for high-temperature compatibility, with all materials selected from high-temperature-resistant industrial-grade materials to raise the equipment's overall heat resistance threshold. Insulation components are made of high-heat-resistant epoxy resin, which withstands prolonged exposure to high temperatures without aging or deformation; sealing gaskets and lubricants for operating mechanisms have been upgraded to high-temperature-resistant formulations to prevent failure under high temperatures. This universal optimization solution is compatible with all types of switchgear on-site, comprehensively improving the equipment's stability during high-temperature operation.
4. Intelligent Temperature-Linked Control for Dynamic Balancing of Heat Dissipation Efficiency
A smart temperature-sensing monitoring and heat dissipation linkage system is installed inside the cabinet to collect real-time temperature data. Based on the temperature rise, the system automatically adjusts exhaust fan speed and controls the start/stop of cooling equipment. It operates at low power consumption under low-temperature conditions and switches to full-load forced cooling under high-temperature conditions. This dynamically matches heat dissipation efficiency to load and ambient temperature, eliminating wasted energy consumption while precisely limiting the maximum temperature rise. The system is designed to adapt to the complex operating conditions of continuous casting shops, including fluctuations in load and temperature.
5. Implementation Results and Industry Value: The Key to Stable Power Distribution Under High-Temperature Conditions
Following systematic temperature rise mitigation upgrades, the operational status of power distribution equipment in the continuous casting shop-located in close proximity to high-temperature heat sources-has been significantly optimized. Under full-load operation and continuous thermal radiation, the temperature rise inside the upgraded 24 kV switchgear is consistently maintained within the safety limits specified by national standards, with no issues of overheating, aging, or parameter drift; The optimized air-insulated switchgear (AIS) effectively addresses the heat accumulation issues inherent in open-frame designs, reducing equipment failure rates by more than 90%.
In heavy industrial settings such as steel mills, the stable operation of various types of switchgear is directly linked to the continuous production of continuous casting lines. Temperature rise control is not merely a matter of optimizing heat dissipation; it is the core safeguard for adapting to extreme operating conditions, preventing premature equipment failure, and minimizing downtime losses-an indispensable component of power distribution design in heavy industry.
Conclusion
The thermal radiation challenges in steel mill continuous casting shops serve as a rigorous test of power distribution equipment's engineering and adaptability. Standardized switchgear cannot withstand extreme high-temperature conditions; only targeted upgrades in thermal insulation, heat dissipation, materials, and intelligent control systems can ensure controllable temperature rises. From the core 24 kV switchgear to the branch-level air-insulated switchgear (AIS), all types of switchgear seeking to operate in high-temperature heavy industrial environments must adhere to the temperature control logic of "thermal insulation first, heat dissipation second, material selection as a safety net, and intelligent control." Through systematic technical solutions that withstand continuous heat radiation, they lay a solid foundation for power distribution safety in the steel industry's continuous and intelligent production processes.
About us
Zhejiang Lvma Electric Co., Ltd. (founded 2018) leverages 17 years of electrical manufacturing know-how with ISO 9001:2015 certification. Our product portfolio centers on intelligent switchgear systems and extends to oil-immersed and dry-type distribution transformers. We export globally to Europe, the Middle East, South America, Southeast Asia, and Africa.
With over 40 patents, our R&D team is driving the company's transformation into a provider of smart, sustainable power solutions. Digital production processes and real-time condition monitoring ensure that every piece of equipment meets the highest standards of safety, reliability, and operational efficiency.