Current transformer adaptive fault early warning method and system based on pressure detection

Abstract

The application discloses a current transformer adaptive fault early warning method and system based on pressure detection, which comprises collecting the operation environment temperature, internal pressure and load current of the current transformer through a pressure detection system; obtaining a linear relationship expression of the internal pressure and internal oil temperature of the current transformer before the current transformer is put into operation; based on the linear relationship expression, using the data collected during normal operation of the current transformer, obtaining a load temperature rise fitting calculation formula of the internal oil temperature of the current transformer; during operation of the current transformer, using the load temperature rise fitting calculation formula to calculate the internal oil temperature calculation value of the current transformer according to the collected current transformer data; comparing the linear relationship slope of the internal pressure measurement value and the internal oil temperature calculation value of the current transformer with the linear relationship slope obtained before the current transformer is put into operation, and if the two are different, it is determined that the current transformer has defects, and an early warning is sent. The application solves the problem that the internal fault of the current transformer cannot be accurately and reliably warned.

Description

Technical Field

[0001] This invention relates to the field of power equipment fault early warning technology, specifically to an adaptive fault early warning method and system for current transformers based on pressure detection. Background Technology

[0002] In my country, 110kV and above oil-immersed current transformers have a capacitor core made of cable paper and aluminum foil electrodes, which is then impregnated with oil to form an oil-paper insulation structure. The amount of oil is relatively small, and faults and aging are inevitable during long-term operation. Once a current transformer experiences a discharge or overheating fault, the insulating oil will decompose, producing characteristic gases. If the defect is not detected in time and continues to deteriorate, it will lead to insulation breakdown of the current transformer, and in severe cases, explosions and fires. This not only damages the equipment itself and causes power outages, but the debris from the explosion will also damage nearby equipment, expanding the power outage area, and in extreme cases, potentially causing personal injury to maintenance personnel. In recent years, there have been several major accidents caused by explosions due to insulation damage of current transformers within the power grid system, seriously affecting the safe and stable operation of the power grid.

[0003] Existing pressure-based fault warning methods for current transformers utilize the PV (internal pressure - insulating oil volume) curve of the current transformer expander and the highest and lowest ambient temperatures throughout the year to calculate the range of internal pressure changes caused by ambient temperature, and use this as the upper and lower limits of the pressure under normal operating conditions. If the measured pressure of the transformer exceeds this range during operation, the current transformer issues a fault warning. However, these existing technical solutions do not consider the differences in expander and internal oil volume between individual current transformers, nor the impact of heat generation and dissipation under different operating loads. In field applications, the following problems may occur: under high temperature and high load conditions, the sensor-measured internal pressure of the transformer may exceed the upper limit of the pressure setting range, causing false alarms; under low temperature and low load conditions, fault warnings may be delayed or missed; and some current transformers may fail to effectively identify faults due to excessive or insufficient oil filling and expansioner processing deviations, frequently resulting in false alarms, delayed or missed faults.

[0004] Therefore, existing technologies cannot adaptively issue effective fault warnings based on the characteristics and operating status of the current transformer itself. The existence of these problems severely restricts the accuracy of current transformer operating status monitoring and interferes with fault identification by maintenance personnel. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing technology does not take into account the differences in the expander and internal oil volume between individual current transformers, as well as the influence of heat generation and heat dissipation under different operating conditions of the transformers. Therefore, it is impossible to issue effective fault warnings accurately, reliably and adaptively based on the characteristics and operating status of the current transformer itself.

[0006] The purpose of this invention is to provide an adaptive fault early warning method and system for current transformers based on pressure detection. This invention considers the combined effects of ambient temperature, load heat generation, and heat dissipation on the internal oil temperature of the current transformer. It combines the characteristics of data collected before and during normal operation of the current transformer. Before commissioning, a linear relationship expression between the internal oil temperature and internal pressure of the transformer is obtained. Based on this linear relationship expression, a fitting calculation formula for the internal oil temperature of the transformer is obtained using the load current, ambient temperature, and internal pressure collected during normal operation. During transformer operation, if the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature differs from the slope obtained before commissioning, the current transformer is deemed to have a defect, and an early warning is issued. When the internal oil volume of the current transformer changes due to maintenance or other reasons, the linear relationship before commissioning and the fitting formula for the internal oil temperature during normal operation are re-obtained. The method of this invention takes into account the operating conditions and individual differences of current transformers, and can adaptively adjust the warning value of the transformers so that different transformers have different warning values; this invention solves the technical problem in related technologies that cannot accurately and reliably warn of internal faults in current transformers.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides an adaptive fault early warning method for current transformers based on pressure detection, the method comprising:

[0009] The operating ambient temperature T0, internal pressure P1, and load current I of the current transformer are collected through a pressure detection system.

[0010] Before the current transformer is put into operation, obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer;

[0011] Based on the linear relationship expression, the load temperature rise fitting calculation formula of the oil temperature inside the current transformer is obtained by using the load current I, ambient temperature T0 and internal pressure P1 collected during the normal operation of the current transformer.

[0012] During the operation of the current transformer, the calculated value of the internal oil temperature of the current transformer is calculated using the load temperature rise fitting calculation formula based on the operating ambient temperature T0, internal pressure P1 and load current I of the current transformer collected by the pressure detection system.

[0013] Compare the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that there is a defect in the current transformer and an early warning is issued.

[0014] Furthermore, the method also includes:

[0015] When the internal oil volume of a current transformer changes due to maintenance or other reasons, the linear relationship expression before the current transformer was put into operation and the fitting calculation formula for the internal oil temperature during normal operation of the current transformer should be obtained again.

[0016] Furthermore, each current transformer is equipped with a pressure detection system, which is used to measure and collect the operating ambient temperature T0, internal pressure P1 and load current I of the current transformer, and to perform data storage, data transmission, mathematical analysis and calculation functions.

[0017] Furthermore, the linear relationship between the internal pressure and internal oil temperature of the current transformer is expressed as: P1=kT1+b, where P1 is the internal pressure of the current transformer; T1 is the internal oil temperature of the current transformer, and before the current transformer is put into operation, its internal oil temperature T1 is the same as the ambient temperature T0; k is the slope of the linear relationship obtained before the current transformer is put into operation; b is a constant; k and b are fitting parameters.

[0018] Before commissioning and under normal operating conditions, the internal pressure and internal oil temperature of the current transformer always satisfy the above linear relationship expression.

[0019] Furthermore, based on the linear relationship expression, using the load current I, ambient temperature T0, and internal pressure P1 collected during the normal operation of the current transformer, a load temperature rise fitting calculation formula for the internal oil temperature of the current transformer is obtained, including:

[0020] The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system.

[0021] The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using a linear relationship expression.

[0022] Subtracting the internal oil temperature T1 from the ambient temperature T0, we obtain the load temperature rise of the current transformer ΔT = T1 - T0.

[0023] Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

[0024] Furthermore, when the current transformer is running under load, the internal oil temperature T1 is equivalent to the sum of the ambient temperature T0 and the temperature rise ΔT of the insulating oil caused by the heat generated and dissipated by the load: T1 = T0 + ΔT. Under normal operating conditions of the current transformer, since the thermal conductivity and heat dissipation area of ​​the transformer material remain constant, ΔT is only related to the load current I of the current transformer and the ambient temperature T0.

[0025] The calculated value of the internal oil temperature T1 of the current transformer is calculated using the load temperature rise fitting calculation formula. The formula is: T1 = f(I, T0) + T0.

[0026] Furthermore, the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer is compared with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that the current transformer has a defect and an early warning is issued, including:

[0027] The slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer is calculated as k1 = (P1-P0) / (T1-T0), where T1 is the calculated internal oil temperature of the current transformer calculated using the load temperature rise fitting formula during the operation of the current transformer; T0 is the ambient temperature before the current transformer is put into operation; P1 is the internal pressure of the current transformer during operation, i.e., the measured pressure value; and P0 is the internal pressure obtained by interpolation using the linear relationship expression before the current transformer is put into operation when the internal temperature is T0.

[0028] Compare the slope k1 of the linear relationship during the operation of the current transformer with the slope k of the linear relationship obtained before the current transformer is put into operation.

[0029] If k1≠k, and k1 changes monotonically with time (the defect continues to develop), then it is determined that the current transformer has a defect and the system issues a fault warning.

[0030] If k1 increases monotonically, the current transformer is judged to be in the form of an electrical heating fault warning, such as partial discharge.

[0031] If k1 decreases monotonically, the current transformer is identified as having a structural sealing fault warning, such as equipment oil leakage.

[0032] Secondly, the present invention also provides a pressure-detection-based adaptive fault early warning system for current transformers, which uses the aforementioned pressure-detection-based adaptive fault early warning method for current transformers; the system includes:

[0033] The data acquisition unit is used to acquire the operating ambient temperature T0, internal pressure P1, and load current I of the current transformer through the pressure detection system.

[0034] The linear relationship expression acquisition unit is used to obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer before it is put into operation.

[0035] The load temperature rise fitting calculation formula is obtained by using the load current I, ambient temperature T0 and internal pressure P1 collected during the normal operation of the current transformer based on the linear relationship expression to obtain the load temperature rise fitting calculation formula of the oil temperature inside the current transformer.

[0036] The slope calculation unit during operation is used to calculate the calculated value of the internal oil temperature of the current transformer based on the operating ambient temperature T0, internal pressure P1 and load current I collected by the pressure detection system during the operation of the current transformer, and to calculate the slope of the linear relationship between the measured value of the internal pressure of the current transformer and the calculated value of the internal oil temperature using the load temperature rise fitting calculation formula;

[0037] The defect judgment unit is used to compare the slope of the linear relationship between the measured internal pressure value and the calculated internal oil temperature value of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that there is a defect in the current transformer and an early warning is issued.

[0038] Furthermore, the system also includes:

[0039] The update unit is used to re-acquire the linear relationship expression of the current transformer before it was put into operation and the fitting calculation formula of the internal oil temperature of the current transformer during normal operation when the internal oil volume of the current transformer changes due to maintenance or other reasons.

[0040] Furthermore, the execution process of the unit obtained by the load temperature rise fitting calculation formula is as follows:

[0041] The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system.

[0042] The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using a linear relationship expression.

[0043] Subtracting the internal oil temperature T1 from the ambient temperature T0, we obtain the load temperature rise of the current transformer ΔT = T1 - T0.

[0044] Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] 1. This invention relates to an adaptive fault early warning method and system for current transformers based on pressure detection. This invention considers the combined effects of ambient temperature, load heat generation, and heat dissipation on the internal oil temperature of the current transformer. It combines the characteristics of data collected before and during normal operation of the current transformer. Before commissioning, a linear relationship expression between the internal oil temperature and internal pressure of the transformer is obtained. Based on this linear relationship expression, a fitting calculation formula for the internal oil temperature of the transformer is obtained using the load current, ambient temperature, and internal pressure collected during normal operation. During transformer operation, if the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature differs from the slope obtained before commissioning, the current transformer is deemed to have a defect, and an early warning is issued. When the internal oil volume of the current transformer changes due to maintenance or other reasons, the linear relationship before commissioning and the fitting formula for the internal oil temperature during normal operation are re-obtained. The method of this invention takes into account the operating conditions and individual differences of current transformers, and can adaptively adjust the warning value of the transformers so that different transformers have different warning values; this invention solves the technical problem in related technologies that cannot accurately and reliably warn of internal faults in current transformers.

[0047] 2. This invention relates to an adaptive fault early warning method and system for current transformers based on pressure detection. This invention clarifies that the internal pressure and internal oil temperature of a current transformer satisfy a linear relationship, and obtains this linear relationship by collecting ambient temperature and internal pressure data before the current transformer is put into operation. Collecting data before operation can eliminate the influence of transformer load heating and heat dissipation on the internal oil temperature.

[0048] 3. This invention relates to an adaptive fault early warning method and system for current transformers based on pressure detection. This invention combines the unique characteristics of data collected before and during normal operation of each transformer to derive a formula for calculating the internal oil temperature of the transformer under normal operation, considering load heating and heat dissipation, and proposes fault criteria. The proposed fault identification method considers the individual differences between transformers, the influence of transformer load heating, heat dissipation, and the amount of oil in the transformer body. The fault identification method is accurate, reliable, and adaptive.

[0049] 4. The present invention provides an adaptive fault early warning method and system for current transformers based on pressure detection. The present invention uses the slope changes of the internal oil temperature and internal pressure of the transformer to identify electrical heating and insulation sealing faults, which has higher sensitivity and accuracy. Attached Figure Description

[0050] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0051] Figure 1 This is a flowchart of the adaptive fault early warning method for current transformers based on pressure detection in Embodiment 1 of the present invention;

[0052] Figure 2 PV curves for current transformer expanders of different voltage levels;

[0053] Figure 3 This is a fitted curve of the linear relationship between the internal oil temperature and internal pressure of the current transformer of the present invention before it is put into operation.

[0054] Figure 4 This invention describes the process of calculating the equivalent temperature rise ΔT caused by load and heat dissipation during normal operation of a current transformer.

[0055] Figure 5 This is a schematic diagram illustrating the present invention's function of providing early warning of current transformer overheating faults.

[0056] Figure 6 This is a schematic diagram of the pressure detection system of the present invention;

[0057] Figure 7 This is a block diagram of the adaptive fault early warning system for current transformers based on pressure detection according to the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0059] Existing pressure-based fault warning methods for current transformers utilize the PV (internal pressure - insulating oil volume) curve of the current transformer expander and the highest and lowest ambient temperatures throughout the year to calculate the range of internal pressure changes caused by ambient temperature. This range is then used as the upper and lower limits of the pressure under normal operating conditions. If the measured pressure of the current transformer exceeds this range during operation, a fault warning is issued.

[0060] The existing technical solutions described above do not consider the differences in expander and internal oil volume between individual current transformers, nor the impact of heat generation and dissipation under different operating loads. In field applications, the following problems may occur: under high temperature and high load conditions, the internal pressure measured by the sensor may exceed the upper limit of the pressure setting range, causing false alarms; under low temperature and low load conditions, current transformer fault warnings may be delayed or missed; some current transformers may fail to effectively identify faults due to excessive or insufficient oil filling and expansion device machining deviations, frequently resulting in false alarms, delayed or missed warnings; and they may not be able to accurately, reliably, and adaptively issue effective fault warnings based on the characteristics and operating status of the current transformer itself.

[0061] Therefore, this invention designs an adaptive fault early warning method and system for current transformers based on pressure detection. This invention considers the combined effects of ambient temperature, load heat generation, and heat dissipation on the internal oil temperature of the current transformer. It combines the characteristics of data collected before and during normal operation of the current transformer. Before commissioning, a linear relationship expression between the internal oil temperature and internal pressure of the transformer is obtained. Based on this linear relationship expression, a fitting calculation formula for the internal oil temperature of the transformer is obtained using the load current, ambient temperature, and internal pressure collected during normal operation. During transformer operation, if the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature differs from the slope obtained before commissioning, the current transformer is determined to have a defect, and an early warning is issued. When the internal oil volume of the current transformer changes due to maintenance or other reasons, the linear relationship before commissioning and the fitting formula for the internal oil temperature during normal operation are re-obtained. The method of this invention takes into account the operating conditions and individual differences of current transformers, and can adaptively adjust the warning value of the transformers so that different transformers have different warning values; this invention solves the technical problem in related technologies that cannot accurately and reliably warn of internal faults in current transformers.

[0062] Specifically, a pressure detection system is installed in each current transformer. This system can measure and collect the load current I, ambient temperature T0, and internal pressure P1 of the current transformer, and has data storage, data transmission, and mathematical analysis functions. Before the current transformer is put into operation, its internal oil temperature T1 is the same as the ambient temperature T0. At this time, based on the collected ambient temperature T0 and internal pressure P1, a linear relationship expression between the internal pressure P1 and the internal oil temperature T1 of the current transformer is obtained, i.e., P1 = kT1 + b, where k and b are fitting parameters. When the current transformer is running under load, the internal oil temperature T1 of the current transformer is equivalent to the sum of the ambient temperature T0 and the temperature rise ΔT of the insulating oil caused by load heating and heat dissipation (T1 = T0 + ΔT). Under normal operating conditions, since the thermal conductivity and heat dissipation area of ​​the transformer material remain constant, ΔT is determined only by the load current I and the ambient temperature T0. Therefore, the internal pressure P1 of the current transformer under normal operating conditions is further collected, and the internal oil temperature T1 corresponding to the internal pressure P1 is obtained by interpolation through a linear relationship expression. The corresponding load temperature rise ΔT = T1 - T0 is then calculated. Using the data collected during normal operation, the least squares method is used to obtain a fitted calculation expression for ΔT: ΔT = f(I, T0). When the current transformer is operating, the pressure detection system, based on the collected load current I and ambient temperature T0, uses the above fitted calculation expression to calculate the internal oil temperature T1 = ΔT + T0 of the current transformer. If the slope k1 of the linear relationship between the calculated oil temperature T1 and the internal measured pressure P1 is different from the slope k of the linear relationship expression obtained before commissioning, and k1 changes monotonically with time, the pressure detection system determines that there is a defect and issues a fault warning. When the internal oil volume of a current transformer changes due to maintenance or other reasons, in order to ensure the reliability of fault warning, the pressure detection system should re-acquire the linear relationship expression between the internal pressure and internal oil temperature of the transformer before it was put into operation, and during normal operation, fit the formula for calculating the internal oil temperature of the current transformer.

[0063] Example 1

[0064] like Figure 1 As shown, the present invention provides an adaptive fault early warning method for current transformers based on pressure detection. This method includes:

[0065] The operating ambient temperature T0, internal pressure P1, and load current I of the current transformer are collected through a pressure detection system.

[0066] Before the current transformer is put into operation, obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer;

[0067] Based on the linear relationship expression, the load temperature rise fitting calculation formula of the oil temperature inside the current transformer is obtained by using the load current I, ambient temperature T0 and internal pressure P1 collected during the normal operation of the current transformer.

[0068] During the operation of the current transformer, the calculated value of the internal oil temperature of the current transformer is calculated using the load temperature rise fitting calculation formula based on the operating ambient temperature T0, internal pressure P1 and load current I of the current transformer collected by the pressure detection system.

[0069] Compare the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that the current transformer has a defect and an early warning is issued.

[0070] When the internal oil volume of a current transformer changes due to maintenance or other reasons, the linear relationship expression before the current transformer was put into operation and the fitting calculation formula for the internal oil temperature during normal operation of the current transformer should be obtained again.

[0071] Specifically, each current transformer is equipped with a pressure detection system. This system measures and collects data on the operating environment temperature T0, internal pressure P1, and load current I of the current transformer, and performs data storage, data transmission, mathematical analysis, and calculation. For example... Figure 6 As shown, Figure 6 This is a structural diagram of a pressure detection system.

[0072] Specifically, before the current transformer is put into operation, its internal oil temperature T1 is the same as the ambient temperature T0 (at which time the load current is 0). Based on the collected ambient temperature T0 and internal pressure P1, the linear relationship expression between the internal pressure P and the internal oil temperature T1 of the transformer is obtained as P1=kT1+b, where P1 is the internal pressure of the current transformer; T1 is the internal oil temperature of the current transformer, and before the current transformer is put into operation, its internal oil temperature T1 is the same as the ambient temperature T0; k is the slope of the linear relationship obtained before the current transformer is put into operation; b is a constant; and k and b are fitting parameters.

[0073] As a further implementation, the proof that the linear relationship between the internal pressure and internal oil temperature of the current transformer satisfies the linear relationship is as follows:

[0074] The internal pressure P1 of the current transformer can be calculated using formula (1):

[0075] (1)

[0076] In the formula, P0 is atmospheric pressure, ρgh is oil pressure, and P a This refers to the pressure of the instrument transformer expansion tank. The atmospheric pressure P0 remains essentially constant and can be considered a constant value. During normal operation of the instrument transformer, the internal insulating oil expands and contracts with temperature changes, but the total mass remains constant, i.e.:

[0077] (2)

[0078] In the formula, ρ1, ρ2, h1, and h2 represent the density and height of the insulating oil at times t1 and t2, respectively. Since the bottom area s of the oil tank is constant, ρ1h1 = ρ2h2. Because the bottom area s of the oil tank is constant, the thermal expansion and contraction of the insulating oil caused by the internal oil temperature will not change the internal oil pressure of the current transformer (ρgh is a constant value). The internal pressure P1 of the current transformer during operation can be further simplified as:

[0079] (3)

[0080] Furthermore, tests show that the transformer expander pressure P a It has a linear relationship with the volume V of insulating oil, such as Figure 2 As shown, (a) the PV fitting curve of the 110kV current transformer expander, (b) the PV fitting curve of the 220kV current transformer expander, and (c) the PV fitting curve of the 5000kV current transformer expander:

[0081] (4)

[0082] In the formula, k0 and b0 are fitting parameters. The relationship between the volume of insulating oil and the temperature of insulating oil is as follows:

[0083] (5)

[0084] In the formula, V0 and V are the volumes of insulating oil before and after the temperature change, respectively. Let x represent the change in oil temperature, and x be the coefficient of thermal expansion of the insulating oil. If 0K is taken as the reference value, and V0 is the volume of the insulating oil at 0K, then:

[0085] (6)

[0086] In the formula, T1 is the internal oil temperature of the current transformer. Combining formulas (4) to (6), we can obtain:

[0087] (7)

[0088] In summary, the internal pressure and internal oil temperature of the current transformer satisfy a linear relationship. Before the current transformer is put into operation, the internal oil temperature T1 of the current transformer is the same as the external ambient temperature T0. At this time, based on the internal pressure P1 and ambient temperature T0 of the current transformer collected before operation, the linear relationship expression between the internal pressure and internal oil temperature of the current transformer can be obtained by fitting formula (7), as follows: Figure 3 As shown. Before commissioning and during normal operation, the internal oil temperature and internal pressure of the current transformer always satisfy the above linear relationship expression.

[0089] Specifically, when a current transformer is operating under load, its internal oil temperature is affected by the combined effects of ambient temperature, load heat generation, heat convection, heat conduction, and heat radiation. Therefore, the internal oil temperature T1 can be equivalently represented as the sum of the ambient temperature T0 and the temperature rise ΔT of the insulating oil caused by load heat generation and heat dissipation: T1 = T0 + ΔT. Under normal operating conditions, since the thermal conductivity and heat dissipation area of ​​the transformer material remain constant, ΔT is only related to the load current I of the current transformer and the ambient temperature T0.

[0090] To calculate the load temperature rise ΔT of the current transformer, the method of this invention continues to collect the load current I, ambient temperature T0, and internal pressure P1 during the normal operation of the current transformer. Using the aforementioned linear relationship expression (formula (7)), the internal oil temperature T1 corresponding to the internal pressure P1 of the transformer is obtained by interpolation. The corresponding load temperature rise ΔT = T1 - T0 is then calculated. The specific operation method is as follows: Figure 4 As shown. Using data collected during the normal period, the least squares method is used to obtain the load temperature rise fitting calculation expression for ΔT: ΔT = f(I, T0). The specific steps are as follows:

[0091] The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system.

[0092] The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using a linear relationship expression.

[0093] Subtracting the internal oil temperature T1 from the ambient temperature T0, we obtain the load temperature rise of the current transformer ΔT = T1 - T0.

[0094] Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

[0095] Specifically, the slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer is compared with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, the current transformer is determined to have a defect, and a warning is issued, including:

[0096] The slope of the linear relationship between the measured internal pressure and the calculated internal oil temperature of the current transformer is calculated as k1 = (P1-P0) / (T1-T0), where T1 is the calculated internal oil temperature of the current transformer during operation using the load temperature rise fitting formula, T1 = T0 + f(T0,I); T0 is the ambient temperature before the current transformer is put into operation; P1 is the measured internal pressure during the operation of the current transformer, i.e., the pressure measurement value; and P0 is the internal pressure obtained by interpolation using the linear relationship expression before the current transformer is put into operation when the internal temperature is T0, P0 = kT0 + b.

[0097] Compare the slope k1 of the linear relationship during the operation of the current transformer with the slope k of the linear relationship obtained before the current transformer is put into operation.

[0098] If k1 ≠ k, and k1 monotonically changes with time (the defect continues to develop), then the current transformer is judged to have a defect and the system issues a fault warning. The specific operation method is as follows: Figure 5 As shown;

[0099] If k1 increases monotonically, the current transformer is judged to be in the form of an electrical heating fault warning, such as partial discharge.

[0100] If k1 decreases monotonically, the current transformer is identified as having a structural sealing fault warning, such as equipment oil leakage.

[0101] Specifically, to ensure the reliability of fault information early warning for current transformers, when the internal oil volume of the current transformer changes due to maintenance or other reasons, the linear relationship expression before the current transformer was put into operation and the fitting calculation formula of the internal oil temperature during normal operation of the current transformer are re-acquired.

[0102] The specific implementation is as follows:

[0103] Step S101: Install a pressure detection system for each current transformer. This system can measure and collect the load current I, ambient temperature T0, and internal pressure P1 of the current transformer, and has data storage, data transmission, and mathematical analysis functions.

[0104] Step S102: Before the current transformer is put into operation, obtain the linear relationship expression between the internal pressure P1 and the internal oil temperature T1 of the current transformer, P1=kT1+b, where k and b are fitting parameters.

[0105] Step S103: Using the load current I, ambient temperature T0, and internal pressure P1 data collected during normal operation of the current transformer; and combining the linear relationship expression from step 102, interpolate to obtain the transformer internal oil temperature T1 corresponding to P1, and further calculate the load temperature rise ΔT = T1 - T0. Using the large amount of the above data collected during normal operation, the least squares method is used to fit and obtain the formula for calculating ΔT, i.e., ΔT = f(I, T0).

[0106] Step S104: During operation of the current transformer, the pressure detection system collects the load current I and ambient temperature T0 of the current transformer. The internal oil temperature T1 of the transformer under normal operating conditions is calculated using the above fitting expression: T1 = T0 + f(T0,I).

[0107] Step S105: Interpolate the internal pressure P0 of the current transformer when the internal oil temperature is the ambient temperature T0 using the linear relationship expression between the internal pressure and internal oil temperature obtained before commissioning. Further calculate the slope k1 = (P1-P0) / (T1-T0) of the internal pressure and internal temperature during transformer operation. If k1 ≠ the slope k obtained before commissioning, and k1 monotonically changes with time (defects continuously develop), pressure detection determines that the current transformer has a defect and the system issues a fault warning. Specific operation methods are as follows... Figure 5 As shown. When k1 monotonically increases, it is judged as an early warning of an electrical heating fault, such as partial discharge; when k1 monotonically decreases, it is judged as an early warning of a structural sealing fault, such as equipment oil leakage.

[0108] Step S106: To ensure the reliability of the fault information early warning for the current transformer, when the internal oil volume of the current transformer changes due to maintenance or other reasons, the pressure detection system should re-acquire the linear relationship expression between the internal pressure and the internal oil temperature before the transformer is put back into operation, and refit the calculation formula for the internal oil temperature of the transformer during normal operation.

[0109] Example 2

[0110] like Figure 7 As shown, the difference between this embodiment and Embodiment 1 is that this embodiment further provides a pressure-detection-based adaptive fault early warning system for current transformers. This system uses the pressure-detection-based adaptive fault early warning method for current transformers from Embodiment 1. The system includes:

[0111] The data acquisition unit is used to acquire the operating ambient temperature T0, internal pressure P1, and load current I of the current transformer through the pressure detection system.

[0112] The linear relationship expression acquisition unit is used to obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer before it is put into operation: P=kT1+b.

[0113] The load temperature rise fitting calculation formula is obtained by using the load current I, ambient temperature T0 and internal pressure P1 collected during the normal operation of the current transformer based on the linear relationship expression to obtain the load temperature rise fitting calculation formula of the oil temperature inside the current transformer.

[0114] The slope calculation unit during operation is used to calculate the calculated value of the internal oil temperature of the current transformer based on the operating ambient temperature T0, internal pressure P1 and load current I collected by the pressure detection system during the operation of the current transformer, and to calculate the slope of the linear relationship between the measured value of the internal pressure of the current transformer and the calculated value of the internal oil temperature using the load temperature rise fitting calculation formula;

[0115] The defect judgment unit is used to compare the slope of the linear relationship between the measured internal pressure value and the calculated internal oil temperature value of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that there is a defect in the current transformer and an early warning is issued.

[0116] As a further implementation, the system also includes:

[0117] The update unit is used to re-acquire the linear relationship expression of the current transformer before it was put into operation and the fitting calculation formula of the internal oil temperature of the current transformer during normal operation when the internal oil volume of the current transformer changes due to maintenance or other reasons.

[0118] As a further implementation, the execution process of obtaining the unit using the load temperature rise fitting calculation formula is as follows:

[0119] The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system.

[0120] The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using a linear relationship expression.

[0121] Subtracting the internal oil temperature T1 from the ambient temperature T0, we obtain the load temperature rise of the current transformer ΔT = T1 - T0.

[0122] Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

[0123] The execution process of each unit can be carried out according to the steps of the adaptive fault early warning method for current transformer based on pressure detection in Example 1, and will not be described in detail in this example.

[0124] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0125] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0126] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0128] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An adaptive fault early warning method for current transformers based on pressure detection, characterized in that, The method includes: The operating ambient temperature, internal pressure, and load current of the current transformer are collected through a pressure detection system. Before the current transformer is put into operation, obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer; Based on the linear relationship expression, the load temperature rise fitting calculation formula of the internal oil temperature of the current transformer is obtained by using the ambient temperature, internal pressure and load current collected during the normal operation of the current transformer. During the operation of the current transformer, the calculated value of the internal oil temperature of the current transformer is calculated based on the operating ambient temperature, internal pressure and load current of the current transformer collected by the pressure detection system, using the load temperature rise fitting calculation formula. Compare the slope of the linear relationship between the measured internal pressure value and the calculated internal oil temperature value of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that the current transformer has a defect and an early warning is issued. Based on the aforementioned linear relationship expression, using the ambient temperature, internal pressure, and load current collected during normal operation of the current transformer, a load temperature rise fitting calculation formula for the internal oil temperature of the current transformer is obtained, including: The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system. The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using the linear relationship expression. Subtracting the internal oil temperature T1 from the ambient temperature T0 yields the load temperature rise of the current transformer ΔT = T1 - T0. Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

2. The adaptive fault early warning method for current transformers based on pressure detection according to claim 1, characterized in that, The method also includes: When the internal oil volume of a current transformer changes due to maintenance, the linear relationship expression before the current transformer was put into operation and the fitting calculation formula for the internal oil temperature during normal operation of the current transformer are re-obtained.

3. The adaptive fault early warning method for current transformers based on pressure detection according to claim 1, characterized in that, Each current transformer is equipped with a pressure detection system, which is used to measure and collect the operating environment temperature, internal pressure and load current of the current transformer, and to perform data storage, data transmission, analysis and calculation.

4. The adaptive fault early warning method for current transformers based on pressure detection according to claim 1, characterized in that, The linear relationship between the internal pressure and internal oil temperature of a current transformer is expressed as follows: P1 = kT1 + b; Where P1 is the internal pressure of the current transformer; T1 is the internal oil temperature of the current transformer. Before the current transformer is put into operation, its internal oil temperature T1 is the same as the ambient temperature T0; k is the slope of the linear relationship obtained before the current transformer is put into operation; b is a constant; k and b are fitting parameters. Before commissioning and under normal operating conditions, the internal pressure and internal oil temperature of the current transformer always satisfy the above linear relationship expression.

5. The adaptive fault early warning method for current transformers based on pressure detection according to claim 1, characterized in that, When a current transformer is running under load, the internal oil temperature T1 is equivalent to the sum of the ambient temperature T0 and the temperature rise ΔT of the insulating oil caused by the heat generated and dissipated by the load: T1 = T0 + ΔT. Under normal operating conditions, ΔT is only related to the load current I of the current transformer and the ambient temperature T0. The calculated value of the internal oil temperature T1 of the current transformer is calculated using the load temperature rise fitting calculation formula. The formula is: T1 = f(I, T0) + T0.

6. The adaptive fault early warning method for current transformers based on pressure detection according to claim 1, characterized in that, Compare the slope of the linear relationship between the measured internal pressure value and the calculated internal oil temperature value of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that the current transformer has a defect and a warning is issued, including: The slope of the linear relationship between the measured internal pressure of the current transformer and the calculated internal oil temperature is calculated as k1 = (P1 - P0) / (T1 - T0), where T1 is the calculated internal oil temperature of the current transformer calculated using the load temperature rise fitting formula during the operation of the current transformer; T0 is the ambient temperature before the current transformer is put into operation; P1 is the internal pressure of the current transformer during operation, i.e., the measured pressure value; and P0 is the internal pressure obtained by interpolation using the linear relationship expression before the current transformer is put into operation when the internal temperature is T0. Compare the slope k1 of the linear relationship during the operation of the current transformer with the slope k of the linear relationship obtained before the current transformer is put into operation. If k1≠k and k1 changes monotonically with time, then the current transformer is judged to have a defect and the system issues a fault warning. If k1 increases monotonically, then the current transformer is judged to be a fault warning of electric heating type. If k1 decreases monotonically, then the current transformer is identified as having a structural sealing fault warning.

7. A current transformer adaptive fault early warning system based on pressure detection, characterized in that, The system includes: The data acquisition unit is used to acquire the operating ambient temperature, internal pressure, and load current of the current transformer through a pressure detection system. The linear relationship expression acquisition unit is used to obtain the linear relationship expression between the internal pressure and internal oil temperature of the current transformer before it is put into operation. The load temperature rise fitting calculation formula acquisition unit is used to obtain the load temperature rise fitting calculation formula of the internal oil temperature of the current transformer based on the linear relationship expression and using the ambient temperature, internal pressure and load current collected during the normal operation of the current transformer. The slope calculation unit during operation is used to calculate the calculated value of the internal oil temperature of the current transformer based on the operating ambient temperature, internal pressure and load current of the current transformer collected by the pressure detection system during the operation of the current transformer, and to calculate the slope of the linear relationship between the measured value of the internal pressure of the current transformer and the calculated value of the internal oil temperature using the load temperature rise fitting calculation formula; and to calculate the slope of the linear relationship between the measured value of the internal pressure of the current transformer and the calculated value of the internal oil temperature. The defect judgment unit is used to compare the slope of the linear relationship between the measured internal pressure value and the calculated internal oil temperature value of the current transformer with the slope of the linear relationship obtained before the current transformer was put into operation. If the two are different, it is determined that there is a defect in the current transformer and an early warning is issued. The execution process of the unit obtained by the load temperature rise fitting calculation formula is as follows: The ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer are collected by a pressure detection system. The internal oil temperature T1 corresponding to the internal pressure P1 of the current transformer is obtained by interpolation using the linear relationship expression. Subtracting the internal oil temperature T1 from the ambient temperature T0 yields the load temperature rise of the current transformer ΔT = T1 - T0. Based on the load temperature rise ΔT and the ambient temperature T0, internal pressure P1, and load current I during normal operation of the current transformer, the least squares method is used to obtain the load temperature rise fitting calculation formula ΔT=f(I,T0).

8. The current transformer adaptive fault early warning system based on pressure detection according to claim 7, characterized in that, The system also includes: The update unit is used to re-acquire the linear relationship expression of the current transformer before it was put into operation and the fitting calculation formula of the internal oil temperature of the current transformer during normal operation when the internal oil volume of the current transformer changes due to maintenance.

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