Dew-point temperature calculation method considering internal dirt of power switch cabinet

Abstract

A dew point temperature calculation method considering internal contamination of a power switch cabinet comprises the following steps: according to the internal environment temperature t of the power switch cabinet, calculating the saturated water vapor pressure ps at the current environment temperature; the relative humidity under the pollution is defined as equivalent relative humidity Ue, and the water vapor pressure p under the pollution is calculated by combining the equivalent relative humidity Ue with the saturated water vapor pressure ps under the current environment temperature; calculating a dew point temperature initial value td under the dirty condition according to the water vapor pressure p of the power switch cabinet under the condition of considering the dirty condition; iterative calculation of the dew point temperature value is carried out, and the final dew point temperature value is determined. According to the dew-point temperature calculation method considering the internal dirt of the power switch cabinet, the accuracy of dew-point temperature calculation can be improved.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a method for calculating dew point temperature considering internal contamination of power switchgear. Background Technology

[0002] As a critical component of the power distribution network, the reliability of power switchgear directly impacts the safety and stability of the entire power system. However, in environments with high humidity and large temperature fluctuations, condensation occurs on the surfaces of objects inside the switchgear when their temperature is below the dew point. Condensation in power switchgear can lead to decreased insulation performance of electrical equipment, causing problems such as insulation flashover and component corrosion. In severe cases, it can damage equipment and even cause system outages. The dew point temperature, as the threshold for determining condensation, is a crucial basis for the activation of condensation warning devices. Therefore, accurately calculating the dew point temperature of power switchgear is of great significance.

[0003] Currently, the dew point temperature of power switchgear is usually calculated using the Manus modified formula, such as in reference [1]: Pan Qize, Yang Fang, Yang Zhi. Discussion on the mechanism of condensation and key prevention technologies of 12kV high voltage switchgear [J]. Power System Protection and Control, 2019, 47(05): 160-172. Reference [2]: Huang Yong. Research on condensation mechanism and heating dehumidification strategy of high voltage switchgear [D]. Fuzhou: Fuzhou University, 2022. Reference [3]: Xu Yan. Research and prevention of condensation in 35 kV high voltage switchgear [J]. Jilin Electric Power, 2023, 51(06): 53-56. However, the above dew point temperature calculation methods only consider the temperature and humidity of the air and do not consider the influence of internal dirt on the dew point temperature of the power switchgear. In reality, electrical switchgear is not completely sealed. To allow air circulation within the cabinet, it typically has vents and openings. Suspended particulate matter from the external environment enters the cabinet through these vents or openings, thus forming dirt. Furthermore, prolonged operation and aging of the electrical equipment inside the cabinet also contribute to dirt formation. Dirt inside the electrical switchgear absorbs moisture and deliquesces even when the air humidity is not fully saturated, lowering the threshold for condensation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for calculating dew point temperature that takes into account the internal contamination of power switch cabinets, thereby improving the accuracy of dew point temperature calculation.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for calculating dew point temperature considering internal contamination of power switchgear includes the following steps: Step 1: Calculate the saturated water vapor pressure at the current ambient temperature t, based on the ambient temperature t inside the power switchgear. p s ; Step 2: Define the relative humidity under the soil as the equivalent relative humidity. U e Combined with the saturated water vapor pressure at the current ambient temperature p s Calculation considering water vapor pressure under pollution p ; Step 3: Based on the water vapor pressure of the power switchgear under contamination conditions p Calculate the initial value of the dew point temperature under polluted conditions. t d ; Step 4: Perform iterative calculations of the dew point temperature value to determine the final dew point temperature value.

[0006] In step 1, when the ambient temperature inside the power switchgear t>0℃, the saturated water vapor pressure p s The calculation formula is as follows: (1); In the formula, K w This is the proportionality coefficient of water vapor pressure under liquid conditions. a w , b w and c w The correlation coefficient for water vapor pressure under liquid conditions; When the ambient temperature inside the power switchgear is t≤0℃, the saturated water vapor pressure p s The calculation formula is as follows: (2); In the formula, K i This is the proportionality coefficient of water vapor pressure under icy conditions. a i , b i and c i The correlation coefficient for water vapor pressure under icy conditions; p s The saturated water vapor pressure t This refers to the internal temperature of the power switchgear.

[0007] In step 2, the equivalent relative humidity is: (3); In the formula, U e To account for the equivalent relative humidity inside the cabinet when it is dirty; U c The relative humidity under clean conditions inside the cabinet; Δ U This represents the effect of dirt on relative humidity.

[0008] In step 2, the power switchgear takes into account the water vapor pressure under pollution conditions. p for: (4); In the formula, p The water vapor pressure of the power switchgear is taken into account under pollution conditions.

[0009] In step 3, the initial value of the dew point temperature under polluted conditions. t d for: (5); In the formula, t d This is the initial dew point temperature, in °C. R , S This is the dew point temperature coefficient; p 0 represents the saturated water vapor pressure at 0°C.

[0010] In step 4, when iteratively calculating the dew point temperature value, the range of dew point temperature detection values ​​is first set according to the initial dew point temperature value. Then, the water vapor pressure value under different dew point temperature detection values ​​is calculated. Next, the water vapor pressure value is compared with the saturated water vapor pressure value. Finally, the dew point temperature detection value with the smallest difference is used as the new initial dew point temperature value, thus realizing the iterative calculation of dew point temperature.

[0011] The proposed upper and lower fluctuation values ​​of dew point temperature are used to determine the range of dew point temperature probe values ​​as follows: (6); In the formula, The range of dew point temperature probe values; Δ t d This represents the dew point temperature fluctuation value.

[0012] The formula for calculating the water vapor pressure at different dew point temperatures is as follows: (7); In the formula, These are the water vapor pressure values ​​at different dew point temperatures.

[0013] Water vapor pressure values ​​at different dew point temperatures With saturated water vapor pressure valuep s By comparing the values, we can find the water vapor pressure value corresponding to the smallest difference: (8); In the formula, This represents the water vapor pressure value corresponding to the minimum difference.

[0014] The water vapor pressure value corresponding to the smallest difference Substitute into equation (7) to determine the dew point temperature value during this detection. The determined dew point temperature value As the initial value of the new dew point temperature t d Repeat the iterative detection of dew point temperature; after multiple iterations, the final dew point temperature value can be obtained.

[0015] This invention provides a method for calculating dew point temperature considering internal contamination in power switchgear, offering the following technical advantages: The relative humidity under contaminated conditions inside the power switchgear is defined as the equivalent relative humidity, which is the relative humidity value under clean conditions inside the power switchgear plus the influence of contamination on the relative humidity. The influence of contamination on the relative humidity inside the power switchgear is a positive value. The water vapor pressure under contaminated conditions is calculated based on the equivalent relative humidity inside the power switchgear. Then, the initial value of the dew point temperature under contaminated conditions is calculated based on the water vapor pressure value under contamination conditions. Finally, the final dew point temperature is determined through iterative calculation. This invention can accurately calculate the dew point temperature of power switchgear, thus providing a theoretical basis for the action criteria of power switchgear condensation early warning devices and technical support for ensuring the safe and stable operation of power switchgear. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a flowchart of the present invention.

[0017] Figure 2 The results are calculated for dew point temperatures under different relative humidities when the amount of contamination is 5%RH in this invention.

[0018] Figure 3 The results are calculated for dew point temperatures under different relative humidities when the ambient temperature is 30°C, as per the present invention.

[0019] Figure 4 The results are calculated for dew point temperatures under different ambient temperatures when the relative humidity is 30%RH in this invention. Detailed Implementation

[0020] like Figure 1-4As shown, a method for calculating the dew point temperature considering internal contamination of a power switchgear includes the following steps: Step 1: Calculate the saturated water vapor pressure at the current ambient temperature based on the internal ambient temperature of the power switch cabinet.

[0021] When the internal ambient temperature of the power switchgear is above zero (>0℃), the formula for calculating the saturated water vapor pressure is as follows: (1); In the formula, p s This is the saturated water vapor pressure, expressed in hPa. t This refers to the internal temperature of the power switchgear, in °C. K w This is the proportionality coefficient of water vapor pressure under liquid conditions; a w , b w and c w This is the correlation coefficient of water vapor pressure under liquid conditions.

[0022] When the ambient temperature inside the power switchgear is below zero (≤0℃), the formula for calculating the saturated water vapor pressure is as follows: (2); In the formula, p s This is the saturated water vapor pressure, expressed in hPa. t This refers to the internal temperature of the power switchgear, in °C. K w This is the proportionality coefficient of water vapor pressure under icy conditions; a w , b w and c w This is the correlation coefficient of water vapor pressure under icy conditions.

[0023] Step 2: Consider the impact of internal contamination on relative humidity in the power switchgear, and define the relative humidity under contamination as the equivalent relative humidity; then combine this with the saturated water vapor pressure at the current ambient temperature. p s The calculation takes into account the water vapor pressure under pollution conditions.

[0024] The presence of contaminants will alter the relative humidity inside the power switchgear. The equivalent relative humidity inside the power switchgear at this time is: (3); In the formula, U eThe equivalent relative humidity inside the cabinet when it is dirty is taken into account, and the unit is %RH; U c The relative humidity inside the cabinet under clean conditions, expressed in %RH; Δ U This represents the effect of dirt on relative humidity; it is a positive value and is expressed in %RH.

[0025] Based on the saturated water vapor pressure at the current ambient temperature p s and equivalent relative humidity when considering dirt U e Calculate the water vapor pressure of the power switchgear under polluted conditions: (4); In the formula, p The water vapor pressure of the power switchgear under polluted conditions is expressed in hPa.

[0026] Step 3: Based on the water vapor pressure of the power switchgear under contamination conditions p Calculate the initial value of the dew point temperature under polluted conditions.

[0027] (5); In the formula, t d This is the initial dew point temperature, in °C. R , S This is the dew point temperature coefficient; p 0 represents the saturated water vapor pressure at 0℃, which can be calculated using equation (2).

[0028] Step 4: Based on the initial value of the dew point temperature under polluted conditions t d The range of dew point temperature probe values ​​is determined, and then the dew point temperature probe values ​​are successively substituted into equation (5) to calculate the water vapor pressure value under different dew point temperature probe values. The water vapor pressure value is then compared with the saturated water vapor pressure value calculated by equation (1) or equation (2). p s By comparing the values, the water vapor pressure value with the smallest difference is found, and the dew point temperature value at the time of the detection is determined based on the correspondence between the water vapor pressure value and the dew point temperature.

[0029] The proposed upper and lower fluctuation values ​​of dew point temperature are used to determine the range of probed dew point temperature values ​​as follows: (6); In the formula, The range of dew point temperature probe values; Δ t dThis represents the dew point temperature fluctuation value. Within the range of dew point temperature detection values, the dew point temperature detection value can be determined using a uniform sampling method.

[0030] Substituting equation (6) into equation (5), the water vapor pressure values ​​under different dew point temperature probe values ​​are calculated using the following formula: (7); In the formula, These are the water vapor pressure values ​​at different dew point temperatures.

[0031] The water vapor pressure values ​​at different dew point temperature probes are compared with the saturated water vapor pressure values ​​calculated by equation (1) or equation (2). p s By comparing the values, we can find the water vapor pressure value corresponding to the smallest difference: (8); In the formula, This represents the water vapor pressure value corresponding to the minimum difference.

[0032] The water vapor pressure value corresponding to the smallest difference Substitute into equation (7) to determine the dew point temperature value during this detection. .

[0033] Step 5: Set the dew point temperature value determined in Step 4 as follows. As the initial value of the new dew point temperature t d Repeat step 4 to iteratively detect the dew point temperature. According to the national standard GB / T 35226-2017, the final dew point temperature value can be obtained after 3 iterations.

[0034] like Figure 2 As shown in the example, this calculation yields the dew point temperature under different ambient temperatures and relative humidities when the pollution impact is 5%RH. Figure 2 It can be seen that, given a certain amount of dirt, the higher the ambient temperature and relative humidity, the higher the dew point temperature.

[0035] like Figure 3 As shown in the figure, this example calculates the dew point temperature under different levels of contamination and relative humidity when the ambient temperature is 30℃. (From...) Figure 3 It can be seen that, under a constant ambient temperature, the greater the amount of dirt and the higher the relative humidity, the higher the dew point temperature.

[0036] like Figure 4 As shown in the example, this calculation yields dew point temperatures under different levels of contamination and ambient temperature when the relative humidity is 30%RH. Figure 4 It can be seen that, under the condition of constant relative humidity, the greater the amount of dirt and the greater the ambient temperature, the higher the dew point temperature.

Claims

1. A method for calculating dew point temperature considering internal contamination of power switchgear, characterized in that, Includes the following steps: Step 1: Calculate the saturated water vapor pressure at the current ambient temperature t, based on the ambient temperature t inside the power switchgear. p s ; Step 2: Define the relative humidity under the soil as the equivalent relative humidity. U e Combined with the saturated water vapor pressure at the current ambient temperature p s Calculation considering water vapor pressure under pollution p ; Step 3: Based on the water vapor pressure of the power switchgear under contamination conditions p Calculate the initial value of the dew point temperature under polluted conditions. t d ; Step 4: Perform iterative calculations of the dew point temperature value to determine the final dew point temperature value.

2. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 1, characterized in that: In step 1, when the ambient temperature inside the power switchgear t>0℃, the saturated water vapor pressure p s The calculation formula is as follows: （1）； In the formula, K w This is the proportionality coefficient of water vapor pressure under liquid conditions. a w , b w and c w The correlation coefficient for water vapor pressure under liquid conditions; When the ambient temperature inside the power switchgear is t≤0℃, the saturated water vapor pressure p s The calculation formula is as follows: （2）； In the formula, K i This is the proportionality coefficient of water vapor pressure under icy conditions. a i , b i and c i The correlation coefficient for water vapor pressure under icy conditions; p s The saturated water vapor pressure t This refers to the internal temperature of the power switchgear.

3. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 1, characterized in that: In step 2, the equivalent relative humidity is: （3）； In the formula, U e To account for the equivalent relative humidity inside the cabinet when it is dirty; U c The relative humidity under clean conditions inside the cabinet; Δ U This represents the effect of dirt on relative humidity.

4. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 3, characterized in that: In step 2, the power switchgear takes into account the water vapor pressure under pollution conditions. p for: （4）； In the formula, p The water vapor pressure of the power switchgear is taken into account under pollution conditions.

5. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 4, characterized in that: In step 3, the initial value of the dew point temperature under polluted conditions. t d for: （5）； In the formula, t d This is the initial dew point temperature, in °C. R , S This is the dew point temperature coefficient; p 0 represents the saturated water vapor pressure at 0°C.

6. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 5, characterized in that: In step 4, when iteratively calculating the dew point temperature value, the range of dew point temperature detection values ​​is first set according to the initial dew point temperature value. Then, the water vapor pressure value under different dew point temperature detection values ​​is calculated. Next, the water vapor pressure value is compared with the saturated water vapor pressure value. Finally, the dew point temperature detection value with the smallest difference is used as the new initial dew point temperature value, thus realizing the iterative calculation of dew point temperature.

7. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 6, characterized in that: The proposed upper and lower fluctuation values ​​of dew point temperature are used to determine the range of dew point temperature probe values ​​as follows: （6）； In the formula, The range of dew point temperature probe values; Δ t d This represents the dew point temperature fluctuation value.

8. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 7, characterized in that: The formula for calculating the water vapor pressure at different dew point temperatures is as follows: （7）； In the formula, These are the water vapor pressure values ​​at different dew point temperatures.

9. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 8, characterized in that: Water vapor pressure values ​​at different dew point temperatures With saturated water vapor pressure value p s Compare the values ​​and find the water vapor pressure value corresponding to the smallest difference: （8）； In the formula, This represents the water vapor pressure value corresponding to the minimum difference.

10. The method for calculating dew point temperature considering internal contamination of power switchgear according to claim 9, characterized in that: The water vapor pressure value corresponding to the smallest difference Substitute into equation (7) to determine the dew point temperature value during this detection. The determined dew point temperature value As the initial value of the new dew point temperature t d Repeat the iterative detection of dew point temperature; after multiple iterations, the final dew point temperature value can be obtained.

Images