Intelligent anti-condensation and humidity control system and control method for electrical cabinet

Abstract

The application discloses an intelligent anti-condensation and humidity control system and control method for an electrical cabinet, and belongs to the technical field of electrical equipment protection. The system comprises a multi-node temperature and humidity sensor group, a main controller, a distributed local PTC heating array, a micro-ventilation device with a drying filter element and a power module; the sensor group collects the temperature and humidity at multiple points in the cabinet and the temperature and humidity outside the cabinet, the main controller calculates the dew point temperature of each point in real time, and automatically switches the working mode according to the condensation risk level. The application solves the problems of electronic component aging and high energy consumption caused by long-term heating of traditional overall heaters, has fast anti-condensation response speed, greatly reduces the energy consumption compared with the traditional heating mode, reduces the average working temperature in the cabinet by 6-8 DEG C, prolongs the service life of electrical components, and is suitable for moisture-proof and anti-condensation of various electrical cabinets such as outdoor switching stations, ring network cabinets and switch cabinets.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology for electrical equipment, specifically relating to an intelligent anti-condensation and humidity control system for electrical equipment such as outdoor switching stations, ring main units, and medium- and high-voltage switchgear, as well as the corresponding control method. Background Technology

[0002] Electrical cabinets are often installed outdoors, in basements, or in power distribution rooms. When the temperature inside the cabinet is lower than the air dew point temperature, water vapor will condense into dew on the cabinet walls, busbar joints, cable terminals, and other locations, leading to a decrease in insulation strength and causing electrical accidents such as flashover, short circuits, and grounding, which seriously threaten the safe operation of the power grid.

[0003] Current methods for preventing condensation in electrical cabinets commonly use integrated heaters. These heaters, ranging from tens to hundreds of watts, are installed inside the cabinet and controlled by temperature or humidity switches. They activate when the temperature is low or the humidity is high, raising the overall temperature inside the cabinet to prevent condensation. However, this method has three significant drawbacks: First, the heater is constantly powered on, resulting in an overall cabinet temperature that is 5-10°C higher than the ambient temperature. Electronic components and insulation work under these high temperatures for extended periods, accelerating aging and shortening their lifespan. The prolonged high-temperature environment also accelerates the aging of insulation components, significantly reducing their lifespan. Second, the overall heating system consumes a lot of energy. A single switchgear heater, constantly powered, can consume tens of kilowatt-hours annually, leading to considerable cumulative energy consumption across a large number of cabinets. Third, the temperature distribution inside the cabinet is uneven during overall heating. While the area near the heater is hot, areas far from the heater, such as cabinet walls, doors, and cable perforations (cold bridge locations), remain cold, resulting in condensation and an unsatisfactory anti-condensation effect.

[0004] Some products use ventilation and dehumidification, with exhaust fans installed on the cabinet. When the humidity is high, ventilation is activated to remove moisture. However, this method can actually draw humid air from the outside into the cabinet when the outside humidity is high (such as on rainy days or during the plum rain season), exacerbating condensation. Simply installing a dehumidifier is costly and bulky, making it unsuitable for small electrical cabinets.

[0005] Existing anti-condensation devices generally lack dew point prediction capabilities. They only activate heating or ventilation when the humidity is already high or condensation has already occurred, resulting in a delayed response. Moreover, they either heat or ventilate the entire system without localized control for areas prone to condensation, leading to significant energy waste and the side effect of component aging.

[0006] Furthermore, existing temperature and humidity sensors are typically installed only in the middle of the cabinet to measure the average temperature and humidity of the air inside, thereby calculating the dew point and controlling heating. However, electrical cabinets contain numerous metal cold bridge structures, with temperature differences of 3-5°C between different locations: the metal cabinet walls dissipate heat quickly to the outside, cables introduce cold energy from outside the cabinet, and metal busbars conduct heat quickly. The temperature at these cold bridge locations is much lower than the average temperature inside the cabinet, making them the first places where condensation occurs. When the average temperature measured by the middle sensor is still higher than the dew point, the actual temperature at the cold bridge location may already be lower than the dew point and condensation may have begun. By the time the sensor detects abnormal humidity, condensation has already formed, which is the core reason why many electrical cabinets equipped with anti-condensation devices still experience flashover accidents.

[0007] Most existing products rely on fixed relative humidity thresholds for control, such as activating heating when the relative humidity exceeds 65%. This control method inherently contains a fundamental error: relative humidity is a relative value that changes with temperature. At 70% relative humidity, there is a 6°C safety margin before condensation at 25°C, but only 2°C before condensation at 10°C. In summer, when temperatures are high, this leads to premature heating and wasted energy; in winter, when temperatures are low, condensation may have already occurred before activation, making precise control impossible. With the development of power distribution network automation, there is an urgent need for an intelligent anti-condensation system that is energy-efficient, does not raise the overall temperature inside the cabinet, has good anti-condensation effects, and provides accurate control, thus overcoming the inherent defects of traditional heating methods. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide an intelligent anti-condensation and humidity control system and method for electrical cabinets. By combining multi-node temperature and humidity acquisition, Magnus formula for accurate dew point calculation, distributed local heating and micro-ventilation with drying, condensation can be predicted in advance. Local heating is prioritized for areas prone to condensation, without raising the overall temperature of the cabinet. This ensures the anti-condensation effect, significantly reduces energy consumption, and avoids long-term high-temperature aging of components inside the cabinet.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: An intelligent anti-condensation and humidity control system for electrical cabinets includes a multi-node temperature and humidity sensor group, a main controller, a distributed local PTC heating array, a micro-ventilation device with a drying filter, and a power module.

[0010] The multi-node temperature and humidity sensor array comprises at least three internal temperature and humidity sensors and one external temperature and humidity sensor. This invention abandons the traditional method of measuring average temperature and humidity using a single sensor, instead placing each internal sensor directly at the location within the cabinet where the temperature is lowest and condensation first occurs (the cold bridge location). Firstly, the top of the inner wall of the cabinet is the lowest temperature point in the entire cabinet, as the metal cabinet wall has a strong ability to radiate heat outwards. The hot air inside the cabinet naturally rises to the top and is cooled, making it the lowest temperature point in the entire cabinet. Secondly, at the insulation support of the busbar compartment joint, the copper busbar conducts heat quickly, and the surface temperature of the insulation component changes with the busbar temperature. In winter or low-temperature environments, the temperature is significantly lower than the ambient air temperature. Third, at the cable compartment terminal, the cable enters the cabinet from the low-temperature environment outside the cabinet. The metal cable core is a significant cold bridge, and the surface temperature of the cable is often close to the temperature outside the cabinet, making it a high-risk location for condensation.

[0011] These locations represent the lowest temperatures within the entire cabinet. If the temperature at these locations is higher than their corresponding dew point, the temperature at all other locations within the cabinet will inevitably be higher than the dew point, preventing condensation. Each sensor corresponds to an independent condensation-prone area. The main controller calculates the dew point temperature for that area based on the sensor's measurement and directly controls the corresponding heating element, achieving point-by-point detection, calculation, and control. This completely eliminates control errors caused by average temperature measurements and effectively avoids the problem of condensation occurring at cold bridge locations without the controller taking action. External sensors are positioned outside the cabinet's ventilation openings to collect ambient temperature and humidity data to determine if ventilation is suitable.

[0012] The main controller is electrically connected to all sensors, heating devices, and micro-ventilation devices, and has a built-in dew point calculation unit. Most existing anti-condensation products rely on a fixed relative humidity threshold for triggering, such as heating when the humidity exceeds 65%. This control method has a large error—relative humidity is a relative value that changes with temperature. At the same 70% humidity, there is a safe distance of 6°C from condensation at 25°C, but only 2°C from condensation at 10°C. This means that in summer, heating may be premature and waste electricity, while in winter, condensation may have already occurred before activation.

[0013] Dew point temperature is the temperature at which water vapor in the air just reaches saturation. It is a physical quantity that is only related to the absolute water content. Dew will definitely form on any surface below the dew point, but not above it. This is the most direct basis for judging condensation. This invention uses the Magnus formula to calculate the dew point, a classic empirical formula used in the meteorological field for many years. The calculation is minimal and can be run on a standard STM32 microcontroller. There is no need to purchase expensive dedicated dew point sensors; a common digital temperature and humidity sensor can calculate a sufficiently accurate dew point value for engineering applications.

[0014] The calculation involves three steps: First, calculate the saturated water vapor pressure using the current location temperature. es=0.61078×exp (17.27T / (T+237.3)), Then calculate the actual water vapor pressure based on the relative humidity: e = es × RH / 100 Finally, the dew point temperature is calculated by reverse calculation: Td=237.3×ln (e / 0.61078) / (17.27-ln (e / 0.61078)), In the formula, T is the actual temperature at that location as measured by the sensor, and RH is the relative humidity at that location.

[0015] Each sensor's data is used individually in a formula to calculate its own dew point, avoiding the need for a uniform value based on average temperature and humidity, thus preventing calculation errors caused by low temperatures at cold bridge locations. After calculation, the difference between the current temperature and the dew point, T-Td, is used as the control variable. This difference represents the temperature margin before condensation, independent of ambient temperature. Regardless of winter or summer, a difference greater than 5°C indicates absolute safety, while a difference less than 2°C indicates a risk of condensation. The control threshold does not need to be adjusted seasonally, making it simple and reliable. The main controller determines the risk level based on the difference at each location and outputs the corresponding control signal, ensuring neither false alarms nor missed actions.

[0016] The distributed local PTC heating array consists of multiple independently controlled low-power PTC heating elements. Each heating element has its own power control circuit, and the main controller independently switches on and off and adjusts the power. The heating elements are not centrally installed in one location, but are individually attached and fixed to the inner wall of the cabinet, busbar joint insulation supports, cable terminal brackets, and other locations prone to condensation and cold bridges. When there is a risk of condensation at a certain location, only the heating element corresponding to that location is activated, heating only that localized area without heating the entire cabinet. This quickly raises the temperature at that location to prevent condensation without causing an overall temperature increase in the cabinet, effectively solving the problems of component aging and high energy consumption caused by traditional overall heating.

[0017] A micro-ventilation device with a desiccant filter is installed at the lower ventilation opening of the cabinet. It includes a miniature ventilation fan and a removable molecular sieve desiccant filter. Unlike ordinary ventilation fans, this device has a very small airflow, performing only minimal ventilation. Furthermore, outside air must pass through the desiccant filter for dehumidification before entering the cabinet, preventing the direct introduction of humid outside air. Micro-ventilation is only activated to expel humid air from the cabinet when the absolute humidity outside is indeed lower than inside, avoiding the problem of ventilation actually introducing moisture during rainy days or the rainy season.

[0018] The power module draws AC220V or DC24V power directly from the secondary circuit of the electrical cabinet, converts it to the voltage required by the system to power each component, and does not require additional wiring.

[0019] PTC heating elements use self-regulating heating elements with a Curie temperature setting of 45~55℃. Even in the event of a controller malfunction, the heating element's temperature will not exceed 55℃, preventing overheating that could damage insulation or cause a fire. Each heating element has a power consumption of only 5~20W, resulting in low power consumption and rapid heating. It only needs to heat a localized metal wall or insulation component, eliminating the need to heat the air. Thermal grease is applied between the heating element and the cabinet's metal wall to ensure rapid heat transfer to the heated components. A heat-reflective layer is attached to the outside of the heating element, ensuring heat is conducted only to the cabinet wall or heated components, preventing radiant heat dissipation into the cabinet's air and minimizing the impact on the overall temperature inside the cabinet.

[0020] The main controller has a built-in three-level condensation risk assessment method, which controls the condensation risk according to the difference between the temperature and the dew point at each location: Level 1 risk is a risk-free state. When the temperature at all locations inside the cabinet is more than 5°C above the corresponding dew point temperature, condensation will not occur, the system will enter a dormant state, retaining only the sensor data acquisition function, and the power consumption is extremely low.

[0021] Level 2 risk is a potential risk state. When the temperature at a certain location is 2-5°C higher than the corresponding dew point temperature, condensation will not occur for a short period of time, but if the humidity continues to rise, there is a risk. In this case, first determine the humidity inside and outside the cabinet. If the absolute humidity outside the cabinet is lower than inside, it means that the outside air is drier. Then, activate the micro-ventilation device to perform a small amount of air exchange to expel the humid air inside the cabinet and reduce the humidity inside the cabinet from the source. There is no need to activate the heating. If the outside humidity is higher than inside the cabinet, stop ventilation and continue monitoring.

[0022] Level 3 risk is a high-risk state. When the temperature at a certain location is less than 2°C above the corresponding dew point, condensation will quickly occur at that location. In this case, the PTC heating element corresponding to that location will be activated first to quickly heat the location, raising the temperature to 3-5°C above the dew point, thus disrupting the conditions for condensation. Heating is only applied to the localized high-risk location; heating elements in other locations will not be activated, and the overall temperature inside the cabinet will hardly increase.

[0023] The air exchange volume of the micro-ventilation device is controlled between 0.1 and 0.5 m³. 3 / h, which falls under the category of micro-ventilation, one 1m 3 The electrical cabinet only exchanges 10% to 50% of its air per hour, preventing significant temperature fluctuations and the introduction of large amounts of dust through airflow. The dryer filter is filled with 4A molecular sieve, reducing the relative humidity of the air entering the cabinet to below 30%. Even in high-humidity environments, only dry air enters the cabinet after passing through the filter, preventing the introduction of humid air. The filter has a drawer-style design and only needs to be replaced every 2-3 years under normal conditions, simplifying maintenance.

[0024] The main controller is also equipped with an overheat protection function. When the overall average temperature inside the cabinet exceeds 40°C, even if there is a risk of condensation in some areas, all heating elements will be forcibly shut down, and only the monitoring function will be retained. This will prevent the heating from further increasing the temperature inside the cabinet during the high temperatures of summer and accelerating the aging of components.

[0025] The main controller has an RS485 communication interface, which can be connected to a power distribution automation system to upload temperature and humidity data, dew point temperature, device operating status, and fault information from various locations to the backend. It supports remote adjustment of parameters such as temperature threshold and heating power without requiring on-site setup. When a sensor fails, the heating element is open-circuited, or the filter needs replacement, the system automatically uploads an alarm signal, facilitating maintenance.

[0026] The PTC heating elements are positioned to cover all areas prone to condensation and cold bridges: the four corners of the inner wall of the top of the cabinet, the inside of the sealing strip of the cabinet door, the surface of the busbar insulation support, the vicinity of the cable terminal terminal, and around the cable perforation on the bottom plate of the cabinet. These are the locations where the temperature is lowest and condensation occurs first when using traditional overall heating. Each location is equipped with a separate heating element to achieve precise heating.

[0027] The control method of the present invention includes the following steps: After the system is powered on, all temperature and humidity sensors collect temperature and relative humidity data at each location every minute and transmit the data to the main controller. Based on the temperature and relative humidity at each location, the main controller uses the Magnus formula to calculate the dew point temperature of the air at that location in real time, and simultaneously calculates the absolute humidity of the air inside and outside the cabinet, thus avoiding errors in relative humidity control in principle.

[0028] After the calculation is completed, all sensor locations inside the cabinet are traversed, the difference between the temperature at each location and the corresponding dew point temperature is calculated, and the current condensation risk level is determined according to the three-level risk standard.

[0029] If the temperature at all locations is more than 5°C above the dew point, it is classified as a Level 1 risk. All heating elements and ventilation devices are turned off, and the system enters a low-power sleep state, waiting for the next data collection cycle.

[0030] If the location temperature is 2-5°C above the dew point, it is classified as a level 2 risk. First, compare the absolute humidity inside and outside the cabinet. If the absolute humidity outside the cabinet is 1g / m³ lower than that inside, then... 3 The above indicates that the outside air is drier, so the micro-ventilation device should be activated at 0.2m. 3 Use a small airflow of / h to ventilate and dehumidify, gradually reducing the humidity inside the cabinet; if the outside humidity is higher, keep it in sleep mode and continue monitoring to avoid moisture ingress.

[0031] If the location temperature is less than 2°C above the dew point, it is classified as a level 3 risk. Immediately activate the corresponding PTC heating element at that location to quickly heat the location at its rated power. Once the temperature rises to 4°C above the dew point, reduce the heating power to maintain the temperature at 2-3°C above the dew point, thus avoiding condensation and reducing energy consumption. When the temperature rises to 5°C above the dew point, turn off the heating element.

[0032] Data is collected every minute, dew point and risk level are recalculated, and the working status of each heating element and ventilation device is dynamically adjusted to achieve real-time dynamic cyclic control.

[0033] When using localized heating, the principle of heating only the high-risk locations must be strictly followed. Only heating elements located near the dew point will be activated, while heating elements in other locations will remain off to prevent overall heating of the air inside the cabinet. During the heating process, the average temperature inside the cabinet will be monitored in real time. When the average temperature exceeds 40°C, all heating elements will be forcibly shut down regardless of whether there is a risk of condensation, to prevent high temperatures from affecting the lifespan of the components.

[0034] After the micro-ventilation device is activated, the humidity difference between the inside and outside of the cabinet is continuously monitored. When the absolute humidity difference between the inside and outside of the cabinet is less than 0.5 g / m³, the humidity will be maintained. 3 When the humidity reaches a certain level, it indicates that the dehumidification has reached equilibrium. Turn off the ventilation device promptly to avoid excessive air exchange. When the external relative humidity is detected to be higher than 90% (in rainy or foggy weather), forcibly lock the micro-ventilation device, prohibiting ventilation from starting, and rely solely on local heating mode to prevent condensation and avoid the entry of humid outside air.

[0035] Compared with the prior art, the present invention has the following beneficial effects: This invention changes the traditional approach of overall heating to prevent condensation in electrical cabinets. It proposes a combination of precise dew point calculation, precise local heating, and dry micro-ventilation. Only the areas prone to condensation are heated when condensation is about to occur, without raising the overall temperature of the cabinet. This effectively solves the problem of component aging caused by long-term heating with traditional heaters. The average operating temperature inside the cabinet can be reduced by 6-8°C compared to traditional heating methods, and the service life of insulating parts and electronic components is significantly extended.

[0036] This invention uses temperature difference instead of the traditional relative humidity threshold control method, which has high control accuracy and avoids problems such as accidental heating in summer and insufficient heating in winter. It can predict the risk of condensation in advance and start control before condensation occurs, with a fast response speed.

[0037] Multi-node sensors are directly placed at the cold bridge location, and each point calculates the dew point and controls the heating independently. This solves the problem of traditional average temperature measurement masking the low temperature of the cold bridge and effectively avoids the defect of condensation occurring at the cold bridge location before the controller takes effect.

[0038] The distributed local heating method used in this invention only heats the areas at risk of condensation. The power of a single heating element is only a few watts to a dozen watts, which greatly reduces energy consumption compared to traditional overall heaters with tens or hundreds of watts. The annual power consumption of a ring main unit can be reduced from tens of kilowatt-hours to a few kilowatt-hours, resulting in significant energy savings.

[0039] The micro-ventilation device with a drying filter solves the problem of moisture induction in ordinary ventilation. It automatically dehumidifies when the outside is dry, reducing the humidity inside the cabinet from the source, reducing the number of heating starts, and further reducing energy consumption. When the outside is humid, it automatically locks the ventilation and relies on local heating to prevent condensation, adapting to various weather conditions.

[0040] This invention has a simple structure, small heating element size, and convenient installation. It can be pre-installed during the production of new cabinets or used to modify existing operating electrical cabinets without altering the cabinet structure, making it widely applicable. This invention also supports communication uploading, which meets the current development requirements of power distribution network automation. Attached Figure Description

[0041] Figure 1 Overall structural block diagram of the anti-condensation system of the present invention; Figure 2 This is a flowchart illustrating the control method of the present invention; Figure 3 This is a schematic diagram showing the arrangement of the PTC heating element of the present invention within the electrical cabinet.

[0042] The markings in the diagram are: 1-Main controller, 2-Indoor temperature and humidity sensor, 3-Outdoor temperature and humidity sensor, 4-PTC heating element, 5-Micro ventilation device, 6-Drying filter element, 7-Power module, 8-RS485 communication interface, 9-Electrical cabinet body, 10-Busbar compartment, 11-Cable compartment, 12-Cable perforation. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1 This embodiment is an intelligent anti-condensation system for 10kV outdoor ring main units, which is suitable for preventing condensation in outdoor cabinets during the rainy season in the south and the winter in the north.

[0045] like Figure 1 and Figure 3As shown, the system is installed inside a standard 10kV ring main unit. The multi-node temperature and humidity sensor group uses SHT30 digital temperature and humidity sensors, with a total of four sensors 2 installed inside the cabinet. These sensors are located at the front left corner of the inner wall of the cabinet top, the rear right corner of the inner wall of the cabinet top, the busbar joint support in busbar compartment 10, and the cable terminal in cable compartment 11. Each sensor directly collects the temperature and relative humidity at its corresponding location, with accuracies controlled within ±0.2℃ and ±2%RH, respectively. The external temperature and humidity sensor 3 is installed outside the ventilation opening at the bottom of the cabinet, equipped with a rain cover, and collects the ambient temperature and humidity.

[0046] The main controller 1 uses a low-power microcontroller with a built-in dew point calculation program. All sensors are connected to the controller via I2C lines. The distributed local PTC heating array consists of 8 PTC heating elements 4, each with a power of 10W, a Curie temperature of 50℃, and self-limiting temperature. The heating elements are attached to: 4 at the four inner corners of the cabinet top, 1 in the middle of the inner side of the cabinet door sealing strip, and 3 each on the three-phase busbar insulation support. A 0.5mm thick layer of thermally conductive silicone grease is applied between the heating elements and the metal wall. An aluminum foil heat-insulating and reflective layer is attached to the back of the heating elements to prevent heat radiation into the cabinet.

[0047] A micro-ventilation device 5 with a drying filter element 6 is installed at the original ventilation hole location at the bottom of the cabinet. The micro ventilation fan uses a 30mm diameter axial flow fan with an air volume of 0.3m³. 3 / h, a drawer-type desiccant filter element 6 is installed inside the fan, filled with 100g of 4A molecular sieve. Air entering the cabinet from the outside must pass through the filter element for dehumidification. The power module 7 draws power from the cabinet's DC24V secondary power supply, converting it to 5V and 12V to power the controller, sensors, fan, and heating element. The controller has an RS485 communication interface 8, which connects to the ring main unit (DTU) to upload data to the distribution automation master station.

[0048] like Figure 2 As shown, the system control method is as follows: After power-on, temperature and humidity data from all sensors are collected every minute. The data from each sensor is then used individually in the Magnus formula to calculate the dew point temperature at that location. es=0.61078*exp(17.27*T / (T+237.3)) e = es * RH / 100 Td=237.3*ln(e / 0.61078) / (17.27-ln(e / 0.61078)) Where T is the actual temperature (°C) measured by the sensor, RH is the relative humidity (%) at the location, and Td is the dew point temperature (°C) at the location.

[0049] After the calculation is complete, iterate through all positions within the cabinet and calculate the difference between T and Td for each position: When T-Td > 5℃ at all locations, all outputs are turned off, the system enters sleep mode, and power consumption is less than 0.5W; When the temperature is 2℃≤T-Td≤5℃, calculate the absolute humidity inside and outside the cabinet. If the absolute humidity outside the cabinet is 1g / m³ lower than that inside the cabinet... 3 Above, turn on the micro ventilation fan at a speed of 0.3m. 3 / h air volume for ventilation, when the humidity difference is less than 0.5g / m³ 3 Turn off the fan when necessary; do not ventilate if the outside humidity is high. When T-Td < 2℃, the corresponding PTC heating element is immediately activated and heated at full power. When T-Td rises to 4℃, the heating element is switched to 50% power for heat preservation. When T-Td > 5℃, the heating element is turned off.

[0050] During the heating process, the average temperature inside the cabinet is monitored in real time. When the average temperature exceeds 40℃, all heating elements are forcibly shut down. When the external relative humidity is >90%, the micro ventilation fan is locked and cannot be started, relying solely on local heating to prevent condensation.

[0051] Actual measurements under low-temperature winter conditions showed that, under typical conditions of an ambient temperature of 10°C and an average air temperature inside the cabinet of 15°C, the actual temperature of the cabinet top inner wall was only 11.2°C, and the surface temperature of the cable terminals was only 10.8°C, which is 3.8~4.2°C lower than the average temperature. If a traditional single-sensor is used to measure the average temperature and humidity, and the relative humidity is calculated at 70%, it might mistakenly determine that the average temperature of 15°C is 3°C away from the dew point, indicating a no-condensation-risk state, and thus no heating would be activated. However, in reality, the temperature at the cabinet top and cable locations is only around 11°C, already below the dew point, and condensation would quickly form. This invention places sensors directly at the cold points, calculating the dew point of each cold point separately. When the temperature at the cold point is less than 2°C from the dew point, heating is activated at the corresponding location, avoiding this control error.

[0052] Field tests were conducted in the humid Jiangzhe region during the plum rain season. The relative humidity outside the cabinet was consistently between 85% and 95%, and the ambient temperature was between 20 and 28°C. After three months of continuous operation, no condensation occurred inside the ring main unit with this system installed. The average temperature inside the cabinet was 27.3°C, which was 5-8°C lower than that of a nearby ring main unit with a traditional 100W heater. The system's cumulative power consumption was 2.1 kWh, while the power consumption of the traditional heater in the same period was 6-8 kWh, resulting in a significant reduction in energy consumption. All electrical components operated at normal temperatures, with no risk of long-term high-temperature aging.

[0053] Example 2 This embodiment is an anti-condensation system for low-voltage switchgear, installed inside the low-voltage switchgear in the basement power distribution room.

[0054] The difference from Embodiment 1 is as follows: Six sensors are installed inside the cabinet, with additional sensors near the cable perforation 12 in the cable compartment and at the contact position in the circuit breaker compartment; a total of 12 PTC heating elements are used, including additional elements around the cable perforation and at the circuit breaker mounting plate position, each with a power of 5W and a Curie temperature of 45℃; the micro-ventilation device has an airflow of 0.2m³ / h. 3 / h, not connected to the power distribution automation system, operates independently.

[0055] The basement environment maintains a humidity level of 70%–90% year-round with minimal temperature fluctuations. The system operates primarily under Level 2 risk conditions, automatically ventilating to remove moisture when the outside humidity (inside the power distribution room) is lower than that inside the cabinet. Localized heating is only activated during sudden temperature changes at seasonal transitions. After six months of continuous operation, no condensation occurred inside the cabinet, with a cumulative power consumption of only 1.2 kWh. The temperature difference between the cabinet and the ambient temperature was less than 2°C, ensuring no impact on the normal operation of low-voltage components.

[0056] Example 3 This embodiment is an anti-condensation system for outdoor pole-mounted switches. It is smaller in size, with four heating elements arranged on the inner wall of the mechanism box and near the terminal blocks. Each element has a power of 5W and is powered by solar energy and a battery, eliminating the need to draw power from the cabinet. It is suitable for retrofitting pole-mounted equipment. The control method is the same as in Embodiment 1, with the addition of low-temperature protection. When the ambient temperature is below 0℃, the heating power is appropriately increased to prevent ice formation inside the box.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also fall within the protection scope of the present invention.

Claims

1. An intelligent anti-condensation and humidity control system for electrical cabinets, characterized in that: It includes a multi-node temperature and humidity sensor group, a main controller, a distributed local PTC heating array, a micro-ventilation device with a drying filter, and a power module; The multi-node temperature and humidity sensor group includes at least three cabinet-inside temperature and humidity sensors and one cabinet-outside temperature and humidity sensor. The cabinet-inside sensors are respectively arranged at the top of the cabinet inner wall, at the busbar compartment joint, and at the cable compartment terminal to collect real-time temperature and relative humidity at each location; the cabinet-outside sensor is arranged outside the cabinet ventilation opening to collect ambient temperature and humidity. The main controller is electrically connected to the sensor group, heating array, and micro-ventilation device respectively. It has a built-in dew point calculation unit. Based on the temperature and humidity data collected at each location, it uses the Magnus formula to calculate the dew point temperature at that location, determines the condensation risk level, and outputs a control signal. The distributed local PTC heating array includes multiple independently controlled PTC heating elements, which are respectively attached and fixed to the inner wall of the cabinet, the insulation support of the bus joint, the cable terminal bracket and other cold bridge positions that are prone to condensation. Each heating element is equipped with a separate power control circuit, which is independently switched on and off and the power is adjusted by the main controller. The micro-ventilation device with a drying filter is installed at the lower ventilation opening of the cabinet. It includes a micro ventilation fan and a detachable molecular sieve drying filter. During ventilation, the outside air enters the cabinet after being dehumidified by the drying filter. It is activated only when the absolute humidity outside the cabinet is lower than that inside the cabinet. The power module draws power from the secondary circuit of the electrical cabinet to supply power to the entire system.

2. The anti-condensation and humidity control system according to claim 1, characterized in that: The PTC heating element is a self-regulating heating element with a Curie temperature of 45~55℃ and a single heating power of 5~20W. Thermal grease is applied between the heating element and the metal wall of the cabinet, and a heat-insulating and reflective layer is attached to the outside of the heating element. Heat is conducted only to the cabinet wall or the heated component and does not radiate heat into the air inside the cabinet.

3. The anti-condensation and humidity control system according to claim 1, characterized in that: The main controller has a built-in three-level condensation risk assessment method: Level 1 Risk: If the temperature at any point inside the cabinet is more than 5°C above the corresponding dew point temperature, there is no risk of condensation, and the system will go into hibernation. Level 2 risk: The temperature at any point inside the cabinet is 2-5°C higher than the corresponding dew point temperature, which poses a risk of condensation. If the absolute humidity outside the cabinet is lower than that inside the cabinet, the micro-ventilation device will be activated to exchange and remove moisture; otherwise, the heating will not be activated. Level 3 risk: If the temperature at any location inside the cabinet is less than 2°C above the corresponding dew point temperature, the risk of condensation is high. In this case, the PTC heating element at the corresponding location will be activated first to provide local heating and raise the temperature at that location to 3-5°C above the dew point. Overall heating will not be activated.

4. The anti-condensation and humidity control system according to claim 1, characterized in that: The air exchange volume of the micro-ventilation device is 0.1~0.5m³. 3 / h, only a small amount of air is exchanged, which does not cause large fluctuations in the temperature inside the cabinet; the drying filter is a 4A molecular sieve filled filter, which can reduce the relative humidity of the air entering the cabinet to below 30%; the filter has a drawer-type structure and can be replaced regularly.

5. The anti-condensation and humidity control system according to claim 1, characterized in that: The main controller is also connected to an internal temperature sensor. When the overall average temperature inside the cabinet is higher than 40°C, all heating elements are forcibly shut down, leaving only the temperature and humidity acquisition function intact, to prevent heating at high temperatures from accelerating component aging.

6. The anti-condensation and humidity control system according to claim 1, characterized in that: The main controller is equipped with an RS485 communication interface, which can upload temperature, humidity, dew point, and working status data at various locations to the power distribution automation system, and supports remote parameter setting and fault alarm; when a sensor fails or the heating element is open-circuited, it automatically uploads a fault signal.

7. The anti-condensation and humidity control system according to claim 1, characterized in that: The PTC heating elements are arranged in the following locations: the four corners of the inner wall of the top of the cabinet, the inside of the sealing strip of the cabinet door, the surface of the busbar insulation support, near the cable terminal terminal, and around the cable perforation on the bottom plate of the cabinet. Heating elements are installed separately in all locations where cold bridging and condensation are likely to occur.

8. A control method for the intelligent anti-condensation and humidity control system for electrical cabinets as described in claim 1, characterized in that... Includes the following steps: S1. Data Acquisition: After the system is powered on, all temperature and humidity sensors collect temperature and relative humidity data at each location in a 1-minute cycle and transmit the data to the main controller. S2. Dew point calculation: The main controller calculates the air dew point temperature at each location in real time using the Magnus formula based on the temperature and relative humidity at each location, and also calculates the absolute humidity of the air inside and outside the cabinet. S3. Risk assessment: Check the location of all sensors in the cabinet one by one, calculate the difference between the temperature at each location and the corresponding dew point temperature, and determine the current condensation risk level. S4, Mode Control: When the temperature at all locations is more than 5°C above the dew point, it is judged as a Level 1 risk, the heating element and ventilation device are turned off, and the system enters a low-power sleep state. When the location temperature is 2-5°C higher than the dew point, it is classified as a level 2 risk. Compare the absolute humidity inside and outside the cabinet. If the absolute humidity outside the cabinet is 1 g / m³ lower than that inside the cabinet... 3 If the above is the case, then activate the micro-ventilation device at 0.2m. 3 / h airflow for ventilation and dehumidification; otherwise, remain in sleep mode. When the temperature at a location is less than 2°C above the dew point, it is determined to be a level 3 risk. Immediately activate the PTC heating element corresponding to that location and heat the location at the rated power until the temperature at that location rises to 4°C above the dew point. Then reduce the heating power and maintain the temperature at 2~3°C above the dew point. When the temperature at that location rises to 5°C above the dew point, turn off the heating element. S5. Cyclic Control: Data is collected again every minute, dew point is calculated, risks are assessed, and the working status of each heating element and ventilation device is dynamically adjusted.

9. The control method according to claim 8, characterized in that: During localized heating in step S4, only the heating element corresponding to the temperature close to the dew point is activated, while the heating elements in other locations remain closed, and the air inside the cabinet is not heated as a whole. The average temperature inside the cabinet is monitored in real time during the heating process, and all heating elements are forcibly shut down when the average temperature exceeds 40°C.

10. The control method according to claim 8, characterized in that: When the micro-ventilation device is activated, the humidity difference between the inside and outside of the cabinet is monitored simultaneously. When the absolute humidity difference between the inside and outside of the cabinet is less than 0.5 g / m³, the ventilation is activated. 3 When necessary, turn off the ventilation device to avoid excessive ventilation and the introduction of humid air from outside; on rainy days or when the relative humidity outside is higher than 90%, force the micro-ventilation device to lock and prevent condensation only through local heating mode.

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