Sampling system and sampling device based on oil level monitoring

Abstract

The invention relates to the field of transformer on-load tap-changer insulating oil sampling, in particular to a sampling system and device based on oil level monitoring, and the system comprises an acquisition module which is used for equipment parameter identification and environment parameter acquisition; the processing module is used for calculating the current oil level according to the collected parameter data and judging a safe sampling flow threshold value according to the interval where the current oil level is located; the execution module is used for adjusting the sampling speed in real time according to the current safe sampling flow threshold value; by combining the real-time liquid level of the insulating oil in the on-load tap-changer of the transformer, the real-time sampling speed in the sampling process is adjusted, the problem of oil flow disturbance caused by too high sampling speed when the real-time liquid level of the insulating oil is low is solved, the probability of heavy gas protection maloperation is reduced, and the operation stability of equipment during sampling is improved.

Description

Technical Field

[0001] This invention relates to the field of sampling insulating oil for on-load tap changers of transformers, and in particular to a sampling system and sampling device based on oil level monitoring. Background Technology

[0002] Currently, the power system needs to conduct insulating oil sampling on a large number of on-load tap changers of transformers in 35kV and above substations every year to perform tests such as trace moisture, breakdown voltage, and gas chromatography to ensure the healthy operation of the equipment.

[0003] When sampling insulating oil from the on-load tap changer of a transformer, the existing sampling equipment maintains a constant flow rate of insulating oil in the sampling pipeline. It cannot adjust the sampling flow rate of insulating oil according to the real-time oil level inside the on-load tap changer of the transformer. When the real-time oil level inside the on-load tap changer of the transformer is low, a higher sampling rate will cause a larger oil flow disturbance under the low oil level condition, which may trigger the heavy gas protection to malfunction, resulting in unnecessary power outages and risks. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is: how to adjust the sampling speed according to the real-time oil level inside the on-load tap changer of the transformer to reduce oil flow disturbance.

[0005] The above-mentioned technical problems are solved by the following technical solution: This invention proposes a sampling system based on oil level monitoring, including: a data acquisition module for identifying equipment parameters and acquiring environmental parameters; a processing module for calculating the current oil level based on the acquired parameter data and determining the safe sampling flow rate threshold based on the current oil level range; and an execution module for adjusting the sampling speed in real time based on the current safe sampling flow rate threshold.

[0006] In a preferred embodiment of the sampling system based on oil level monitoring described in this invention, the equipment parameters include the equipment voltage level, the equipment rated oil volume reference value, the cross-sectional area of ​​the sampling outlet, and the cross-sectional area of ​​the sampling pipeline.

[0007] In a preferred embodiment of the oil level monitoring-based sampling system of the present invention, the environmental parameters include the current real-time pressure at the oil outlet, the current ambient temperature, and the current ambient relative humidity.

[0008] In a preferred embodiment of the oil level monitoring-based sampling system of the present invention, real-time adjustment of the sampling speed includes real-time monitoring of the flow rate of insulating oil in the sampling pipeline, with a sampling frequency of 10 times per second. When the flow rate of more than 20 sampling points exceeds the safe sampling flow rate threshold within 3 consecutive seconds, the flow rate of insulating oil in the sampling pipeline is adjusted so that the flow rate of insulating oil in the sampling pipeline is less than the safe sampling flow rate threshold.

[0009] In a preferred embodiment of the oil level monitoring-based sampling system described in this invention: the formula for calculating the current oil level is as follows: In the formula, V t The current oil level is given, V0 is the rated oil volume of the equipment (reference value), k1 is the pressure correction factor, and P... t P0 is the current real-time pressure at the oil outlet, which is the standard pressure value, taken as 101.325 kPa. k2 is the volumetric thermal expansion coefficient of the insulating oil. T1 is the current ambient temperature, which is the standard temperature value, taken as 20℃. k3 is the humidity correction factor, RH. t The current relative humidity is RH0, which is the standard relative humidity value, taken as 50%RH.

[0010] In a preferred embodiment of the oil level monitoring-based sampling system described in this invention: the formula for calculating the pressure correction coefficient k1 is as follows: Where S is the cross-sectional area of ​​the sampling oil outlet, ρ is the density of the insulating oil (0.89 g / cm³ for mineral oil and 0.98 g / cm³ for vegetable oil), g is the gravitational acceleration (9.8 m / s²), and V0 is the rated oil capacity.

[0011] In a preferred embodiment of the oil level monitoring-based sampling system described in this invention: for mineral insulating oil, at a temperature between 20-50°C, k2 is taken as 7.0-7.8 × 10⁻⁶. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 9.5-10.5×10. -4 ℃ -1 For mineral insulating oil, at temperatures between 50-90℃, k2 is taken as 7.8-9.0 × 10⁻⁶. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 10.5-12.0 × 10. -4 ℃ -1 .

[0012] In a preferred embodiment of the oil level monitoring-based sampling system described in this invention: the formula for calculating the humidity correction coefficient k3 is as follows: In the formula, a and b are coefficients related to the type of insulating oil. For mineral insulating oil, a = 1.0 and b = 1.5 × 10⁻⁶. - 4 RH -1 For vegetable insulating oil, a = 1.5, b = 2.0 × 10⁻⁶ -4 RH -1 RH t This represents the current relative humidity.

[0013] In a preferred embodiment of the oil level monitoring-based sampling system of the present invention: the safe sampling flow rate threshold is the maximum allowable sampling flow rate at the current oil level, wherein the formula for calculating the maximum allowable sampling flow rate at the current oil level is: Q set =k safe ×A×v base ×f(V) t ) In the formula, Q set k is the maximum allowable sampling flow rate at the current oil level. safe The basic safety factor is taken as 0.6, where A is the cross-sectional area of ​​the sampling pipeline, and v base The reference flow velocity is determined based on the equipment voltage level: 0.3 m / s for 110 kV, 0.25 m / s for 220 kV, and 0.2 m / s for 500 kV. f(V) t The value is the oil level adaptive adjustment factor. It is 0.5 when the current oil level is 30% below the rated oil volume of the equipment, 0.7 when the current oil level is between 30% and 50% of the rated oil volume of the equipment, and 1.0 when the current oil level is 50% above the rated oil volume of the equipment.

[0014] The present invention also proposes a sampling device for sampling insulating oil of on-load tap changers of transformers, including a sampling system based on oil level monitoring.

[0015] The beneficial effects of this invention are as follows: by combining the real-time liquid level of the insulating oil inside the on-load tap changer of the transformer, the real-time sampling speed during the sampling process is adjusted, reducing the oil flow disturbance caused by excessive sampling speed when the real-time liquid level of the insulating oil is low, reducing the probability of false tripping of heavy gas protection, and improving the operational stability of the equipment during sampling. When calculating the real-time liquid level of insulating oil inside the on-load tap changer of a transformer, the influence of environmental factors, such as ambient temperature and current relative humidity, is introduced to improve the accuracy of insulating oil level calculation. Compared with the traditional single pressure calculation, the oil level calculation error is reduced from the traditional 10%-15% to less than 3%. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention. Wherein: Figure 1 A block diagram of a sampling system based on oil level monitoring is shown. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0018] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0019] This specific embodiment provides a sampling system based on oil level monitoring, including: The data acquisition module is used for equipment parameter identification and environmental parameter acquisition. Specifically, equipment parameters include equipment voltage level, equipment rated oil volume reference value, sampling outlet cross-sectional area, and sampling pipeline cross-sectional area. By inputting the equipment model, the module identifies the equipment voltage level, equipment rated oil volume reference value, and sampling outlet cross-sectional area. By inputting the sampling pipeline diameter, the module calculates the sampling pipeline cross-sectional area. Environmental parameters include the current real-time pressure at the oil outlet, current ambient temperature, and current ambient relative humidity. The current real-time pressure at the oil outlet is measured by a pressure sensor installed at the oil outlet, and the current ambient temperature and current ambient relative humidity are measured by a thermometer and a hygrometer, respectively. The processing module is used to calculate the current oil level based on the collected parameter data, and determine the safe sampling flow rate threshold based on the current oil level range. The execution module is used to adjust the sampling rate in real time based on the current safe sampling flow threshold.

[0020] This includes real-time adjustment of the sampling rate, The flow rate of insulating oil in the sampling pipeline is monitored in real time, with a sampling frequency of 10 times per second. When the flow rate of more than 20 sampling points exceeds the safe sampling flow rate threshold within 3 consecutive seconds, the flow rate of insulating oil in the sampling pipeline is adjusted so that the flow rate of insulating oil in the sampling pipeline is less than the safe sampling flow rate threshold.

[0021] The formula for calculating the current oil level is: In the formula, V t The current oil level is given, V0 is the rated oil volume of the equipment (reference value), k1 is the pressure correction factor, and P... t P0 is the current real-time pressure at the oil outlet, which is the standard pressure value, taken as 101.325 kPa. k2 is the volumetric thermal expansion coefficient of the insulating oil. T1 is the current ambient temperature, which is the standard temperature value, taken as 20℃. k3 is the humidity correction factor, RH.t The current relative humidity is RH0, which is the standard relative humidity value, taken as 50%RH.

[0022] In the current oil level calculation method, ambient temperature affects the thermal expansion characteristics of insulating oil, and humidity affects the hygroscopicity of insulating oil. Both of these factors have a significant impact on oil level measurement. By using an oil level accuracy calculation algorithm that couples operating pressure, oil capacity, temperature, and humidity, dynamic oil level calculation can be achieved. This algorithm breaks through the limitations of traditional single-parameter calculation. Compared with traditional single pressure calculation, the oil level calculation error has been reduced from the traditional 10%-15% to less than 3%.

[0023] In the above formula, the formula for calculating the pressure correction coefficient k1 is as follows: Where S is the cross-sectional area of ​​the sampling oil outlet, ρ is the density of the insulating oil (0.89 g / cm³ for mineral oil and 0.98 g / cm³ for vegetable oil), g is the gravitational acceleration (9.8 m / s²), and V0 is the rated oil capacity.

[0024] For the volumetric thermal expansion coefficient k2 of insulating oil, in the temperature range of 20-50℃, for mineral insulating oil, k2 is taken as 7.0-7.8×10. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 9.5-10.5×10. -4 ℃ -1 For mineral insulating oil, at temperatures between 50-90℃, k2 is taken as 7.8-9.0 × 10⁻⁶. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 10.5-12.0 × 10. -4 ℃ -1 .

[0025] The formula for calculating the humidity correction factor k3 is as follows: In the formula, a and b are coefficients related to the type of insulating oil. For mineral insulating oil, a = 1.0 and b = 1.5 × 10⁻⁶. - 4 RH -1 For vegetable insulating oil, a = 1.5, b = 2.0 × 10⁻⁶ -4 RH -1 RHt represents the current ambient relative humidity.

[0026] The safe sampling flow rate threshold is the maximum allowable sampling flow rate at the current oil level. The formula for calculating the maximum allowable sampling flow rate at the current oil level is as follows: Q set =k safe ×A×v base×f(V) t ) In the formula, Q set k is the maximum allowable sampling flow rate at the current oil level. safe The basic safety factor is taken as 0.6, where A is the cross-sectional area of ​​the sampling pipeline, and v base The reference flow velocity is determined based on the equipment voltage level: 0.3 m / s for 110 kV, 0.25 m / s for 220 kV, and 0.2 m / s for 500 kV. f(V) t The value is the oil level adaptive adjustment factor. It is 0.5 when the current oil level is 30% below the rated oil volume of the equipment, 0.7 when the current oil level is between 30% and 50% of the rated oil volume of the equipment, and 1.0 when the current oil level is 50% above the rated oil volume of the equipment.

[0027] Based on the calculated current dynamic precise oil level V t It intelligently adjusts the safety flow threshold to achieve adaptive protection based on oil level perception. Compared with the traditional single-flow insulating oil sampling method, it greatly reduces the problem of high frequency of false tripping of heavy gas protection caused by excessive flow rate under the current real-time oil level conditions, and maintains the stability of equipment operation during sampling.

[0028] This specific embodiment also provides a sampling device for sampling insulating oil from an on-load tap changer of a transformer, including the above-mentioned sampling system based on oil level monitoring.

[0029] Example 1: The on-load tap changer of the main transformer in a 220kV substation has a rated oil capacity of 150L and uses mineral insulating oil. It is equipped with a DN25 sampling pipeline (cross-sectional area A=491mm²). The maintenance personnel are performing insulating oil sampling operations. The ambient temperature is 35℃ and the relative humidity is 70%RH.

[0030] During initial sampling, the current real-time pressure P at the oil port is measured by a pressure sensor. t =28.5kPa, under the conditions of an ambient temperature of 35℃, a relative humidity of 70%RH, and the use of mineral oil as the insulating oil. , k2 = 7.5 × 10 -4 ℃ -1 , k3 = 1.0 - 1.5 × 10 -4 ×70=0.9895; During the initial sampling, the current real-time oil level can be determined as follows: The current real-time oil level V is calculated. t=151.65L, which is 101.1% of the rated oil capacity of the on-load tap changer of the main transformer in the substation. The oil quantity is sufficient. f(V) t Taking 1.0, we can then derive the maximum allowable sampling flow rate during the initial sampling. Q set =0.6×491×10 -6 ×0.25×1.0=7.365×10 -5 m 3 / s=4.42L / min; The initial flow velocity in the sampling tube is controlled at 0.12 m / s. Based on the cross-sectional area of ​​the sampling tube, A = 491 mm², the initial sampling flow rate is Q. t =0.12×491×10-6=5.892×10-5m3 / s=3.54L / min, which is below the safe sampling flow rate threshold. The current sampling rate can be maintained, and monitoring and adjustment will be implemented during subsequent sampling processes.

[0031] Example 2: A 110kV substation's on-load tap changer has a rated oil capacity of 80L, uses vegetable insulating oil, and is equipped with a DN20 sampling pipeline (cross-sectional area A=314mm²). 2 The ambient temperature was 22℃ and the humidity was 55%RH.

[0032] The real-time pressure P at the oil port is measured by a pressure sensor. t =15.2kPa, the current real-time oil level V is calculated. t =25.32L, which is 31.65% of the rated oil capacity, falling within the 30-50% range, f(V t Taking 0.7, we can then derive the maximum sampled flow rate Q at this point. set =2.37L / min, the sampling flow rate is controlled at 0.1m / s, which corresponds to a sampling flow rate of 2.26L / min. This is below the safe sampling flow rate threshold, and the current sampling rate can be maintained. Real-time monitoring and adjustment will be carried out during subsequent sampling.

[0033] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A sampling system based on oil level monitoring, characterized in that: include, The data acquisition module is used for device parameter identification and environmental parameter acquisition. The processing module is used to calculate the current oil level based on the collected parameter data, and determine the safe sampling flow rate threshold based on the current oil level range. The execution module is used to adjust the sampling rate in real time based on the current safe sampling flow threshold.

2. The sampling system based on oil level monitoring according to claim 1, characterized in that: The equipment parameters include the equipment voltage level, the equipment rated oil volume reference value, the cross-sectional area of ​​the sampling outlet, and the cross-sectional area of ​​the sampling pipeline.

3. The sampling system based on oil level monitoring according to claim 2, characterized in that: Environmental parameters include the current real-time pressure at the oil outlet, the current ambient temperature, and the current ambient relative humidity.

4. The sampling system based on oil level monitoring according to claim 3, characterized in that: Real-time adjustment of sampling speed includes, The flow rate of insulating oil in the sampling pipeline is monitored in real time, with a sampling frequency of 10 times per second. When the flow rate of more than 20 sampling points exceeds the safe sampling flow rate threshold within 3 consecutive seconds, the flow rate of insulating oil in the sampling pipeline is adjusted so that the flow rate of insulating oil in the sampling pipeline is less than the safe sampling flow rate threshold.

5. The sampling system based on oil level monitoring according to claim 4, characterized in that: The formula for calculating the current oil level is: In the formula, V t The current oil level is given, V0 is the rated oil volume of the equipment (reference value), k1 is the pressure correction factor, and P... t P0 is the current real-time pressure at the oil outlet, which is the standard pressure value, taken as 101.325 kPa. k2 is the volumetric thermal expansion coefficient of the insulating oil. T1 is the current ambient temperature, which is the standard temperature value, taken as 20℃. k3 is the humidity correction factor, RH. t The current relative humidity is RH0, which is the standard relative humidity value, taken as 50%RH.

6. The sampling system based on oil level monitoring according to claim 5, characterized in that: The formula for calculating the pressure correction factor k1 is as follows: Where S is the cross-sectional area of ​​the sampling oil outlet, ρ is the density of the insulating oil (0.89 g / cm³ for mineral oil and 0.98 g / cm³ for vegetable oil), g is the gravitational acceleration (9.8 m / s²), and V0 is the rated oil capacity.

7. The sampling system based on oil level monitoring according to claim 6, characterized in that: For mineral insulating oil, at temperatures between 20-50℃, k2 is taken as 7.0-7.8×10⁻⁶. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 9.5-10.5×10. -4 ℃ -1 For mineral insulating oil, at temperatures between 50-90℃, k2 is taken as 7.8-9.0 × 10⁻⁶. -4 ℃ -1 For vegetable insulating oil, k2 is taken as 10.5-12.0 × 10. -4 ℃ -1 .

8. The sampling system based on oil level monitoring according to claim 7, characterized in that: The formula for calculating the humidity correction factor k3 is as follows: In the formula, a and b are coefficients related to the type of insulating oil. For mineral insulating oil, a = 1.0 and b = 1.5 × 10⁻⁶. -4 RH -1 For vegetable insulating oil, a = 1.5, b = 2.0 × 10⁻⁶ -4 RH -1 RH t This represents the current relative humidity.

9. The sampling system based on oil level monitoring according to claim 8, characterized in that: The safe sampling flow rate threshold is the maximum allowable sampling flow rate at the current oil level. The formula for calculating the maximum allowable sampling flow rate at the current oil level is: Q set =k safe ×A×v base ×f(V t ) In the formula, Q set k is the maximum allowable sampling flow rate at the current oil level. safe The basic safety factor is taken as 0.6, where A is the cross-sectional area of ​​the sampling pipeline, and v base The reference flow velocity is determined based on the equipment voltage level: 0.3 m / s for 110 kV, 0.25 m / s for 220 kV, and 0.2 m / s for 500 kV. f(V) t The value is the oil level adaptive adjustment factor. It is 0.5 when the current oil level is 30% below the rated oil volume of the equipment, 0.7 when the current oil level is between 30% and 50% of the rated oil volume of the equipment, and 1.0 when the current oil level is 50% above the rated oil volume of the equipment.

10. A sampling device for sampling insulating oil from an on-load tap changer of a transformer, characterized in that: The sampling system based on oil level monitoring as described in any one of claims 1 to 9 is included.

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