A transformer oil multi-stage filter membrane filtration purification method, system, device and medium

Abstract

The application discloses a transformer oil multi-stage filter membrane filtration and purification method, system, device and medium, and belongs to the technical field of transformer oil purification. The method comprises the following steps: determining the interception state of a front-stage membrane according to the interception progress of the front-stage membrane to impurities, and determining the removal state of a rear-stage membrane according to the removal progress of the rear-stage membrane to impurities; controlling the sequence of the interception treatment and the removal treatment of the oil liquid by the rear-stage membrane according to the combined state formed by the interception state of the front-stage membrane and the removal state of the rear-stage membrane, and determining the time when the interception treatment of the front-stage membrane ends; controlling the front-stage membrane to end the interception treatment when the time is reached; and ending the current batch of purification treatment when the purification degree of the oil liquid treated by the multi-stage membrane reaches a purification target after the front-stage membrane ends the interception treatment. The application makes the treatment sequence of the rear-stage membrane correspond to the impurity composition currently entering the rear-stage membrane, and makes the treatment of the front-stage membrane and the rear-stage membrane connect with each other in time sequence.

Description

Technical Field

[0001] This invention relates to the field of transformer oil purification technology, specifically to a method, system, equipment, and medium for multi-stage pressure filtration and purification of transformer oil. Background Technology

[0002] Transformer oil deteriorates during operation, producing solid mechanical impurities and polar dissolved impurities, requiring purification and regeneration for reuse. Multi-stage pressure filtration membrane systems are commonly used for transformer oil purification. These systems consist of multiple membrane stages connected in series along the oil treatment direction, with the oil passing through each stage sequentially. In adjacent stages connected in series, the preceding membrane retains solid mechanical impurities, while the subsequent membrane removes polar dissolved impurities from the oil treated by the preceding membrane. The retaining layer formed on the surface of the preceding membrane adsorbs and enriches the polar dissolved impurities in the oil.

[0003] In existing multi-stage filtration membrane purification methods, each membrane operates independently according to a fixed sequence, with the retention operation of the preceding membrane and the removal operation of the following membrane being independent of each other. However, polar dissolved impurities adsorbed and enriched by the retention layer on the surface of the preceding membrane can enter the following membrane along with the oil, causing a change in the content of polar dissolved impurities in the oil entering the following membrane. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention provides a method, system, equipment and medium for multi-stage pressure filtration and purification of transformer oil.

[0005] Therefore, the technical problem solved by the present invention is that in the process of purifying transformer oil with multi-stage pressure filtration membranes, the operation of each stage of the membrane is independent of each other. Changes in the retention state of the first stage membrane cannot be responded to in a timely manner by the next stage membrane. When the composition of impurities entering the next stage membrane changes, it still operates according to a fixed operating sequence, resulting in a decrease in purification effect.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a multi-stage pressure filtration membrane purifying method for transformer oil, comprising, The retention status of the preceding membrane is determined based on the progress of impurity retention by the preceding membrane. The removal status of the subsequent membrane is determined based on the progress of impurity removal by the subsequent membrane. Based on the combined state of the retention state of the pre-stage membrane and the removal state of the post-stage membrane, the order in which the post-stage membrane performs retention and removal treatments on the oil is controlled, and the time when the pre-stage membrane ends the retention treatment is determined. When the moment when the pre-membrane finishes its retention process is reached, the pre-membrane is controlled to finish its retention process. After the pre-membrane finishes its retention treatment, the purification treatment of this batch of transformer oil ends when the oil purified by the multi-stage membrane treatment reaches the purification target.

[0007] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil according to the present invention, the step of determining the retention state of the preceding membrane based on the retention progress of the preceding membrane and determining the removal state of the subsequent membrane based on the removal progress of the subsequent membrane includes: The transmembrane pressure difference at the inlet side of the fore-stage membrane is subjected to a second-order differential. When the sign of the second-order differential result is the same as the sign of the pre-calibrated retention reference, the fore-stage membrane is in a state where the retention progress conforms to the retention reference. When the sign of the second-order differential result is different from the sign of the retention reference, the fore-stage membrane is in a state where the retention progress deviates from the retention reference. A first-order difference is performed on the dielectric constant at the outlet side of the subsequent membrane. When the sign of the first-order difference result is the same as the sign of the pre-calibrated removal reference, the subsequent membrane is in a state where the removal progress conforms to the removal reference. When the sign of the first-order difference result is different from the sign of the removal reference, the subsequent membrane is in a state where the removal progress deviates from the removal reference.

[0008] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil according to the present invention, the step of controlling the order of retention and removal treatment of the oil by the subsequent membrane based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and determining the time when the retention treatment of the preceding membrane ends, includes: When the retention progress of the preceding membrane is faster than the retention reference, and the removal progress of the following membrane deviates from the removal reference, the removal process of the following membrane is adjusted to be performed before the retention process. The time when the dielectric constant of the outlet side of the downstream membrane changes from a negative value to a positive value is determined as the time when the downstream membrane removal process is completed. When the downstream membrane removal process is completed, the upstream membrane is controlled to end the retention process.

[0009] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil according to the present invention, the step of controlling the order of retention and removal treatment of the oil by the subsequent membrane based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and determining the time when the retention treatment of the preceding membrane ends, further includes: When the retention progress of the preceding membrane is slower than the retention benchmark, a backwashing process is inserted into the retention process of the following membrane. During the backwashing process, the retrieval status of the downstream membrane is paused, while the removal status of the downstream membrane is continuously updated. After the backwashing process is completed, the retention status of the downstream membrane is re-determined; When the retention progress of the downstream membrane recovers to meet the retention benchmark, the upstream membrane is controlled to end the retention process.

[0010] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil according to the present invention, the step of ending the purification treatment of this batch of transformer oil when the purification degree of the oil after multi-stage membrane treatment reaches the purification target includes: When the dielectric constant of the oil after the multi-stage membrane treatment is less than or equal to the reference value of the dielectric constant corresponding to the target purification depth, the purification treatment of this batch of transformer oil ends. When the dielectric constant of the oil after multi-stage membrane treatment is greater than the dielectric constant reference value, the retention state of the front membrane and the removal state of the back membrane are re-determined for this batch of transformer oil, the order of retention and removal treatment of the oil by the back membrane is re-controlled according to the combined state, the retention treatment of the front membrane is re-controlled to end, and the number of purification cycles is incremented by one. The purification process for this batch of transformer oil ends when the number of purification cycles exceeds the preset maximum number of purification cycles.

[0011] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil described in this invention, it further includes: After the purification treatment of this batch of transformer oil is completed and before the purification treatment of the next batch of transformer oil begins, the moment when the retention progress of the front membrane in this batch is faster than the retention benchmark is determined and recorded as the gel transition moment. Compare the gel transition time with the transition time corresponding to the retention benchmark; When the gel transition time is earlier than the transition time corresponding to the retention benchmark, a pre-retention operation is inserted at the beginning of the next batch of the pre-membrane purification operation. The pre-retention operation retains gel-like impurities in the oil. During the pre-retention operation, the transmembrane pressure difference at the inlet side of the front membrane is subjected to a second-order differential. When the sign change direction of the second-order differential result is the same as the corresponding change direction of the retention reference, the pre-retention operation is terminated. From the moment the pre-retention operation ends, operations are performed to determine the retention state of the preceding membrane and to control the order in which the subsequent membrane performs retention and removal treatments on the oil.

[0012] As a preferred embodiment of the multi-stage pressure filtration and purification method for transformer oil described in this invention, it further includes: During the pre-retention operation performed by the upstream membrane, the running time of the downstream membrane is paused, so that the retention and removal states of the downstream membrane remain at the values ​​before the pre-retention operation began. After the pre-retention operation of the preceding membrane is completed, the running time of the following membrane is synchronized with the running time of the preceding membrane and restarted. From the moment of restart, the retention and removal states of the subsequent membrane are restored and determined.

[0013] This invention provides a multi-stage pressure filtration membrane purification system for transformer oil.

[0014] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a transformer oil multi-stage pressure filtration membrane purification system, comprising: a state determination unit, used to determine the retention state of the upstream membrane and the removal state of the downstream membrane; The processing control unit is used to control the order in which the subsequent membrane performs retention and removal treatments on the oil based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and to determine the time when the preceding membrane ends the retention treatment. The retention termination unit is used to control the front-stage membrane to end the retention process when the time when the retention process of the front-stage membrane ends is reached. The purification termination unit is used to terminate the purification process of this batch of transformer oil when the oil purification level reaches the purification target after the pre-stage membrane has finished its retention treatment and after the multi-stage membrane treatment has completed its retention treatment.

[0015] The present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the multi-stage pressure filter membrane filtration and purification method for transformer oil.

[0016] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the multi-stage pressure filter membrane filtration and purification method for transformer oil.

[0017] The beneficial effects of the present invention are as follows: The present invention organizes the processing sequence of the subsequent membrane by combining the retention state of the preceding membrane with the removal state of the subsequent membrane, so that the processing sequence of the subsequent membrane corresponds to the composition of the impurities entering the subsequent membrane. When the composition of the impurities entering the subsequent membrane changes, the subsequent membrane no longer operates according to a fixed operating sequence, but processes the oil according to the order corresponding to the current impurity composition.

[0018] The present invention determines the moment when the pre-stage membrane ends its retention treatment by reversing the aforementioned combined state, so that the retention treatment of the pre-stage membrane ends when the subsequent membrane exhibits the corresponding changes affected by the pre-stage membrane treatment, and the retention treatment of the pre-stage membrane and the treatment of the subsequent membrane are sequentially connected. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a general flowchart of a multi-stage pressure filtration and purification method for transformer oil provided in one embodiment of the present invention.

[0021] Figure 2 This is a flowchart illustrating the process of accelerated gel blockage of the pre-stage membrane and deviation of the removal of the subsequent membrane in a multi-stage pressure filtration and purification method for transformer oil, provided in an embodiment of the present invention.

[0022] Figure 3 This is a flowchart illustrating the backwashing process of the subsequent membrane during the deceleration of the preceding membrane in a multi-stage pressure filtration and purification method for transformer oil, as provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0024] Example 1, referring to Figures 1-3 This is one embodiment of the present invention, which provides a multi-stage pressure filtration and purification method for transformer oil, comprising: S1, Determine the retention status of the front-stage membrane based on the progress of impurity retention by the front-stage membrane.

[0025] In the multi-stage filtration membrane system, among two adjacent membrane stages connected in series, the first membrane stage is called the pre-stage membrane, and the second membrane stage is called the post-stage membrane. The multi-stage filtration membrane system includes multiple membrane stages connected in series along the oil processing direction. In two adjacent membrane stages connected in series, the membrane stage that first performs oil retention treatment is called the pre-stage membrane, and the membrane stage that later performs oil removal treatment after the pre-stage membrane is called the post-stage membrane.

[0026] This embodiment takes the multi-stage pressure filtration membrane system, which includes three membranes connected in series, as an example. The membrane in the last stage of the three-stage membrane is the final stage membrane. Steps S1 to S5 are performed for each pair of adjacent membranes.

[0027] It is understood that the impurities in the oil include solid mechanical impurities and polar dissolved impurities, and the larger particles among the solid mechanical impurities are large particle impurities.

[0028] It is understood that the solid mechanical impurities accumulate on the surface of the pre-stage membrane to form a gel-like sludge, and the gel-like sludge forms a retention layer on the surface of the pre-stage membrane. The retention layer formed by the gel-like sludge on the membrane surface is referred to as the gel layer.

[0029] It is understood that the progress of the pre-film membrane in retaining impurities in step S1 refers to the degree to which the pre-film membrane forms the retention layer on the membrane surface and retains solid mechanical impurities in the oil.

[0030] It should be noted that the retention progress is reflected by the transmembrane pressure difference at the inlet side of the pre-stage membrane. The transmembrane pressure difference is the difference between the pressure at the inlet side of the pre-stage membrane and the pressure at the outlet side of the pre-stage membrane, which is obtained by subtracting the pressures collected by pressure sensors installed at the inlet and outlet sides of the pre-stage membrane.

[0031] It is understood that the thicker the retention layer formed on the membrane surface of the pre-membrane, the greater the resistance of the oil to passing through the pre-membrane, and the greater the transmembrane pressure difference; the faster the retention layer forms, the faster the transmembrane pressure difference rises.

[0032] It should be noted that the retention status of the pre-stage membrane in step S1 is a determination result of whether the retention progress is normal relative to the retention benchmark. The retention status is used in step S3 to form a combined status with the removal status of the post-stage membrane.

[0033] In some embodiments, the specific implementation of determining the retention state of the pre-stage membrane based on the progress of impurity retention by the pre-stage membrane in step S1 includes step S11, wherein: S11, perform a second-order differential on the transmembrane pressure difference at the inlet side of the pre-stage membrane. When the sign of the second-order differential result is the same as the sign of the pre-calibrated retention reference, the pre-stage membrane is in a state where the retention progress conforms to the retention reference. When the sign of the second-order differential result is different from the sign of the retention reference, the pre-stage membrane is in a state where the retention progress deviates from the retention reference.

[0034] It is understood that the multi-stage pressure filtration membrane system includes a controller, which collects the transmembrane pressure difference at the inlet side of the pre-stage membrane according to a preset calculation cycle during purification operation, thereby obtaining a time series of the transmembrane pressure difference at the inlet side of the pre-stage membrane. In some embodiments, the calculation cycle is 1 second.

[0035] It should be noted that the acquisition, differential analysis, determination and control of transmembrane pressure difference and dielectric constant in steps S1 to S5 are all performed by the controller.

[0036] It is understandable that performing second-order difference on the transmembrane pressure difference at the inlet side of the pre-membrane in step S11 means subtracting two adjacent sampled values ​​in the transmembrane pressure difference time series to obtain a first-order difference sequence, and then subtracting two adjacent values ​​in the first-order difference sequence to obtain a second-order difference result.

[0037] It should be noted that the sign of the second-order difference result represents the acceleration or deceleration of the rise in transmembrane pressure difference. A positive second-order difference result indicates that the rise in transmembrane pressure difference is accelerated, corresponding to faster formation of the trapping layer of the preceding membrane. A negative second-order difference result indicates that the rise in transmembrane pressure difference is decelerated, corresponding to slower formation of the trapping layer of the preceding membrane.

[0038] It should be noted that the pre-calibrated retention benchmark mentioned in step S11 is obtained by performing a calibration run on the multi-stage filter press system in advance. The calibration run is completed before the purification run and is not performed during the purification run.

[0039] It should be noted that, in the multi-stage pressure filtration membrane system, each stage membrane is subjected to second-order differential analysis of the transmembrane pressure difference at the inlet side of the stage membrane in the manner described in step S11 to obtain the retention benchmark of the stage membrane itself, and the stage membrane itself is divided into multiple stages based on the retention benchmark of the stage membrane. The multiple stages of the pre-stage membrane and the multiple stages of the post-stage membrane are the stages of the pre-stage membrane and the post-stage membrane, respectively.

[0040] Specifically, during the calibration operation, the transmembrane pressure difference at the inlet side of the pre-stage membrane is continuously collected and a second-order differential is performed. The time when the second-order differential result changes from a positive value to a negative value and from a negative value to a positive value is recorded. These times are arranged in chronological order to obtain the retention benchmark of the pre-stage membrane.

[0041] Furthermore, each moment in the intercepted reference includes two items: the temporal position of that moment in the calibration operation, and the sign transition direction of the second-order difference result at that moment.

[0042] Furthermore, the time interval between adjacent symbol transition times in the interception benchmark is divided into stages to obtain multiple stages of the front-stage membrane. The time interval from the start of the calibration operation to the first symbol transition time is the first stage, the time interval from the last symbol transition time to the end of the calibration operation is the last stage, and the time intervals between adjacent symbol transition times are the intermediate stages.

[0043] Furthermore, for each of the multiple stages of the pre-membrane, the sign of the second-order difference result within that stage is recorded as the sign of the retention reference for that stage.

[0044] Optionally, when the second-order difference result undergoes no sign transformation during the entire calibration run, the cutoff reference is an empty sequence, and the entire calibration run duration is treated as a single stage.

[0045] Optionally, when the second-order difference result is zero at the boundary time between a certain stage and an adjacent stage, the sign of the cutoff reference for that stage is taken as the sign of the cutoff reference of the stage with the longer time interval between the two adjacent stages; when the time intervals of the two adjacent stages are equal, the sign of the cutoff reference of the stage with the earlier time sequence is taken.

[0046] It is understood that the controller times the pre-stage membrane during the purification operation to obtain the running time of the pre-stage membrane, and uses the running time to locate the stage in which the running time is located among multiple stages of the pre-stage membrane, as the current stage in which the pre-stage membrane is located.

[0047] It should be noted that when the multi-stage filter press system is started, the running time of the membrane at the first stage is calculated from the moment the multi-stage filter press system is started; except for the membrane at the first stage, the running time of each membrane is calculated from the moment the membrane above it begins to normally supply oil to it.

[0048] It is understood that the normal delivery of oil from the upper-level membrane to the lower-level membrane means that the upper-level membrane delivers oil to the lower-level membrane after completing all pre-operations. The pre-operations include pre-retention operations and pre-separation operations.

[0049] Furthermore, the comparison of the sign of the second-order difference result with the sign of the retention benchmark in step S11 refers to finding the sign of the retention benchmark for the current stage of the upstream membrane in the retention benchmark at the current moment, and comparing the sign of the second-order difference result of the transmembrane pressure difference on the inlet side of the upstream membrane at the current moment with the sign of the retention benchmark for that stage.

[0050] For example, when the runtime is longer than the total runtime of the calibration run, the sign of the cutoff reference in the final stage is used as the sign of the cutoff reference used for comparison.

[0051] It is understood that when the sign of the second-order difference result at the current moment is the same as the sign of the retention benchmark, the retention progress of the front membrane is consistent with the retention progress under the calibration operation, the front membrane is in a state where the retention progress conforms to the retention benchmark, and the state where the retention progress conforms to the retention benchmark is the benchmark retention state.

[0052] Furthermore, the states in which the retention progress deviates from the retention benchmark include a gel-accelerated blocking state and a retention-decelerated state.

[0053] Specifically, when the second-order difference result is positive and the sign of the retention reference is negative, the retention progress of the fore-stage membrane is faster than the retention reference, and the fore-stage membrane is in a gel-accelerated plugging state. The gel-accelerated plugging state corresponds to the situation where the gel-state sludge of the fore-stage membrane accelerates the plugging of the membrane surface.

[0054] Specifically, when the second-order difference result is negative and the sign of the retention reference is positive, the retention progress of the front membrane is slower than the retention reference, and the front membrane is in a retention deceleration state. The retention deceleration state corresponds to the situation where solid mechanical impurities in the oil entering the back membrane are not sufficiently retained.

[0055] It should be noted that when the second-order difference result is equal to zero at the current moment, the retention state of the front-stage membrane remains unchanged from the value of the previous calculation cycle, so as to avoid misjudgment at the boundary moment of sign transition.

[0056] Through step S1, this embodiment uses the comparison result of the sign of the second-order difference result of the transmembrane pressure difference on the inlet side of the pre-membrane membrane with the sign of the retention benchmark as the retention state of the pre-membrane membrane. The sign change of the second-order difference result of the transmembrane pressure difference is different from the method of judging the membrane fouling state by the absolute value of the transmembrane pressure difference or a fixed numerical threshold. It can identify two different fouling situations: gel-accelerated blockage and retention-decelerated. It has adaptive capability to the differences in impurity composition of different batches of transformer oil and solves the problem of poor adaptability of fixed numerical thresholds to different batches of transformer oil.

[0057] S2, Determine the removal status of the subsequent membrane based on the progress of impurity removal by the subsequent membrane.

[0058] It is understood that the progress of the downstream membrane in removing impurities mentioned in step S2 refers to the degree to which the downstream membrane removes polar dissolved impurities in the oil.

[0059] It should be noted that the removal progress is reflected by the dielectric constant at the outlet side of the subsequent membrane, which is acquired by a dielectric constant sensor located at the outlet side of the subsequent membrane.

[0060] It should be noted that the dielectric constant of the oil changes with the temperature of the oil. When the controller collects the dielectric constant, it controls the temperature of the oil at a preset reference temperature, or compensates the collected dielectric constant to the dielectric constant at the reference temperature.

[0061] It is understood that the removal reference obtained from the calibration operation, the dielectric constant reference value, and the dielectric constant collected during the purification operation are all dielectric constants at the reference temperature, so that the comparison and difference of the dielectric constants are performed under the same temperature reference.

[0062] It is understood that the higher the content of polar dissolved impurities in the oil, the greater the dielectric constant of the oil; the removal of polar dissolved impurities by the subsequent membrane reduces the content of polar dissolved impurities in the oil, and the dielectric constant decreases accordingly.

[0063] It should be noted that the removal status of the downstream membrane in step S2 is a determination result of whether the removal progress is normal relative to the removal benchmark. The removal status is used in step S3 to form a combined status with the retention status of the upstream membrane.

[0064] In some embodiments, the specific implementation of determining the removal status of the subsequent membrane based on the progress of impurity removal by the subsequent membrane in step S2 includes step S21, wherein: S21, perform a first-order difference on the dielectric constant of the outlet side of the downstream membrane. When the sign of the first-order difference result is the same as the sign of the pre-calibrated removal reference, the downstream membrane is in a state where the removal progress conforms to the removal reference. When the sign of the first-order difference result is different from the sign of the removal reference, the downstream membrane is in a state where the removal progress deviates from the removal reference.

[0065] It is understood that the controller collects the dielectric constant of the downstream membrane outlet side according to the calculation cycle during the purification operation, and obtains the dielectric constant time series of the downstream membrane outlet side.

[0066] It is understood that performing a first-order difference on the dielectric constant at the outlet side of the subsequent membrane in step S21 means subtracting two adjacent sampled values ​​in the time series of the dielectric constant to obtain the first-order difference result of the dielectric constant.

[0067] It should be noted that the sign of the first-order difference result represents the increase or decrease of the dielectric constant on the outlet side of the subsequent membrane. A positive first-order difference result indicates that the dielectric constant increases, corresponding to an increase in the content of polar dissolved impurities in the oil. A negative first-order difference result indicates that the dielectric constant decreases, corresponding to the removal of polar dissolved impurities in the oil.

[0068] It should be noted that the pre-calibrated removal reference mentioned in step S21 is obtained through the calibration run, and the removal reference and the retention reference of the pre-stage membrane are obtained in the same calibration run.

[0069] Specifically, during the calibration operation, the dielectric constant of the outlet side of the downstream membrane is continuously collected and a first-order difference is performed. The moment when the first-order difference result changes from a negative value to a positive value is recorded. These moments are arranged in chronological order to obtain the removal benchmark of the downstream membrane.

[0070] It is understood that the multiple stages of the subsequent membrane are stages obtained by dividing the subsequent membrane according to the retention criteria of the subsequent membrane itself in the manner described in step S11.

[0071] It should be noted that the symbol of the removal reference of the subsequent membrane is recorded according to multiple stages of the subsequent membrane. The removal reference and the retention reference of the subsequent membrane come from the same calibration run and correspond to the same time axis. The symbol of the removal reference corresponds to multiple stages of the subsequent membrane according to the same time axis, so that the subsequent membrane has both the symbol of the retention reference used to determine the retention state and the symbol of the removal reference used to determine the removal state in the same stage.

[0072] Furthermore, for each of the multiple stages of the subsequent membrane, the sign of the first-order difference result of the dielectric constant of the outlet side of the subsequent membrane within that stage is recorded as the sign of the removal reference for that stage.

[0073] Optionally, when the first-order difference result of the dielectric constant is zero at the boundary time between a certain stage and an adjacent stage, the sign of the removal reference of that stage is taken as the sign of the removal reference of the stage with the longer time interval between the two adjacent stages; when the time intervals of the two adjacent stages are equal, the sign of the removal reference of the stage with the earlier time sequence is taken.

[0074] Optionally, when there is no moment during the entire calibration process when the first-order difference result of the dielectric constant changes from a negative value to a positive value, the removal reference is an empty sequence. In this case, the sign of the removal reference in each stage of the subsequent film is uniformly taken as the sign that appears more frequently in the first-order difference result of the dielectric constant during the entire calibration process; when the frequency of the first-order difference result being positive is equal to the frequency of it being negative, the sign of the removal reference is negative.

[0075] It is understood that the controller times the subsequent membrane to obtain the running time of the subsequent membrane, and uses the running time of the subsequent membrane to locate the current stage of the subsequent membrane among multiple stages of the subsequent membrane.

[0076] It should be noted that during the purification operation, the controller collects the transmembrane pressure difference on the inlet side of the downstream membrane according to the calculation cycle and performs second-order differential analysis. The second-order differential analysis result of the transmembrane pressure difference on the inlet side of the downstream membrane is used to determine the retention state of the downstream membrane in the manner described in step S11, and is used to trigger the backwashing treatment of the downstream membrane in step S321.

[0077] Furthermore, the comparison of the sign of the first-order difference result with the sign of the removal reference in step S21 refers to finding the sign of the removal reference for the current stage of the downstream membrane in the removal reference at the current moment, and comparing the sign of the first-order difference result of the dielectric constant of the downstream membrane outlet side at the current moment with the sign of the removal reference for that stage.

[0078] It is understood that when the sign of the first-order difference result at the current moment is the same as the sign of the removal benchmark, the subsequent membrane is in a state where the removal progress conforms to the removal benchmark.

[0079] Furthermore, when the sign of the first-order difference result at the current moment is opposite to the sign of the removal reference, the subsequent membrane is in a state where the removal progress deviates from the removal reference.

[0080] It is understood that the permeate is an oil that permeates through the pre-membrane into the post-membrane.

[0081] It should be noted that the state in which the downstream membrane deviates from the removal benchmark has a specific physical origin. The gel layer on the surface of the upstream membrane adsorbs and enriches polar dissolved impurities in the oil. The adsorbed and enriched polar dissolved impurities enter the downstream membrane with the permeate, causing the change in the dielectric constant at the outlet side of the downstream membrane to deviate from the removal law characterized by the removal benchmark. As a result, the sign of the first difference result of the dielectric constant at the outlet side of the downstream membrane is opposite to the sign of the removal benchmark.

[0082] It is understood that the state in which the removal progress of the downstream membrane deviates from the removal benchmark is an observable basis for the influence of the upstream membrane's retention treatment on the downstream membrane through oil transfer and reflected at the outlet side of the downstream membrane. The removal state is used to trigger the adjustment of the processing sequence of the downstream membrane in step S3.

[0083] It should be noted that when the first-order difference result of the dielectric constant is equal to zero at the current moment, the removal state of the subsequent film remains unchanged from the value of the previous calculation cycle, so as to avoid misjudgment at the boundary moment of sign transition.

[0084] Further, in step S21, a second-order difference is performed on the dielectric constant of the outlet side of the subsequent membrane to obtain the second-order difference result of the dielectric constant of the outlet side of the subsequent membrane. The second-order difference result of the dielectric constant is used to determine the time when the removal process of the subsequent membrane is completed in step S312.

[0085] In step S2, this embodiment uses the deviation between the sign of the first-order difference result of the dielectric constant at the outlet side of the downstream membrane and the sign of the removal benchmark as an observable basis for the enrichment and transfer effect of the upstream membrane gel layer on polar dissolved impurities. This transforms the physical effect of the upstream membrane gel layer on the enrichment and transfer of polar dissolved impurities into a state quantity that can be monitored online. This provides a basis for determining the order of the downstream membrane's retention and removal treatment of oil in step S3 based on the state quantity, thus solving the problem that existing methods do not identify and respond to this correlation between the upstream and downstream membranes.

[0086] S3, based on the combined state of the retention state of the pre-stage membrane and the removal state of the post-stage membrane, control the order in which the post-stage membrane performs retention and removal treatments on the oil, and determine the time when the pre-stage membrane ends the retention treatment.

[0087] It is understood that the combined state described in step S3 is composed of the retention state of the pre-stage membrane and the removal state of the post-stage membrane. The retention state of the pre-stage membrane is obtained in step S1, and the removal state of the post-stage membrane is obtained in step S2.

[0088] It should be noted that step S3 simultaneously governs two aspects in the aforementioned combined state: firstly, controlling the order in which the downstream membrane performs retention and removal treatments on the oil; and secondly, determining the moment when the upstream membrane ends its retention treatment.

[0089] It should be noted that the sequence of steps S3 includes not only changing the order of the subsequent membrane's oil retention and removal processes, but also inserting backwashing into the retention process of the subsequent membrane.

[0090] Under normal circumstances, the downstream membrane processes the oil in the order of retention treatment first and removal treatment second. Step S3 adjusts the order of the conventional treatment according to the combined state.

[0091] It should be noted that when the pre-stage membrane is in the reference retention state, regardless of the removal state of the post-stage membrane, the post-stage membrane processes the oil in the order of retention treatment first and removal treatment second, as is the case under normal circumstances. The retention treatment of the pre-stage membrane ends after the pre-stage membrane has undergone all sign changes recorded by the retention reference in the retention state. When the retention reference of the pre-stage membrane is an empty sequence, the retention treatment of the pre-stage membrane ends when the running time of the pre-stage membrane reaches the total time of the calibrated operation.

[0092] It should be noted that when the pre-stage membrane is in the gel-accelerated blocking state and the post-stage membrane is in a state where the removal progress meets the removal benchmark, the polar dissolved impurities adsorbed and enriched by the pre-stage membrane gel layer have not yet manifested on the outlet side of the post-stage membrane. The post-stage membrane processes the oil in the order described in the conventional case. The retention process of the pre-stage membrane ends after the retention state of the pre-stage membrane has undergone all the sign changes recorded by the retention benchmark, or ends when the removal state of the post-stage membrane changes to a state where the removal progress deviates from the removal benchmark.

[0093] It is understood that the retention state of the pre-stage membrane switches between the baseline retention state, the gel acceleration and blocking state, and the retention deceleration state, and the removal state of the post-stage membrane switches between the removal progress conforming to the removal baseline and the removal progress deviating from the removal baseline. Step S3 determines the organization of the processing sequence of the post-stage membrane and the time when the retention treatment of the pre-stage membrane ends, based on the current values ​​of the retention state of the pre-stage membrane and the removal state of the post-stage membrane.

[0094] It should be noted that when the retention state of the pre-stage membrane or the removal state of the post-stage membrane changes, causing the combined state to switch between the conditions corresponding to the baseline retention state, the accelerated sealing and removal of the gel, the conditions corresponding to step S31, and the conditions corresponding to step S32, the retention or removal process currently being performed by the post-stage membrane continues until the current process is completed, and then the oil is processed according to the method corresponding to the switched combined state, without reverting the processing already performed by the post-stage membrane.

[0095] In some embodiments, the specific implementation of step S3, which controls the order of oil retention and removal by the subsequent membrane based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and determines the moment when the preceding membrane ends its retention treatment, includes steps S31 to S32, wherein: S31, when the retention progress of the pre-stage membrane is faster than the retention reference, and the removal progress of the post-stage membrane deviates from the removal reference, the post-stage membrane is controlled to adjust the removal process to be performed before the retention process, and the moment when the pre-stage membrane ends the retention process is determined.

[0096] It is understandable that, such as Figure 2 As shown, in step S31, the retention progress of the pre-stage membrane is faster than the retention benchmark, that is, the pre-stage membrane is in the gel-accelerated blocking state, which indicates that the gel-state sludge of the pre-stage membrane accelerates the blocking of the membrane surface, and the gel layer of the pre-stage membrane enhances the adsorption and enrichment of polar dissolved impurities in the oil.

[0097] It is understandable that the removal progress of the downstream membrane in step S31 deviates from the removal benchmark, that is, the downstream membrane is in a state where the removal progress deviates from the removal benchmark, which indicates that the polar dissolved impurities adsorbed and enriched by the gel layer of the upstream membrane have entered the downstream membrane with the permeate and are reflected in the dielectric constant of the downstream membrane outlet side.

[0098] It should be noted that, under the combined condition that the retention progress of the pre-stage membrane is faster than the retention benchmark and the removal progress of the post-stage membrane deviates from the removal benchmark, the content of polar dissolved impurities in the oil entering the post-stage membrane increases. Therefore, the post-stage membrane is controlled to adjust the removal process to be performed before the retention process, so that the post-stage membrane preferentially removes the polar dissolved impurities that enter it.

[0099] In some embodiments, step S31 includes steps S311 to S312, wherein: S311, the removal process of the subsequent membrane is adjusted to be performed before the retention process.

[0100] It is understandable that in step S311, adjusting the removal process of the downstream membrane to be performed before the retention process means changing the order of the downstream membrane from retention process first and removal process second in the normal case to removal process first and retention process second, so that the downstream membrane performs the removal process before the retention process.

[0101] S312, perform a second-order difference on the dielectric constant of the outlet side of the downstream membrane, and determine the moment when the second-order difference result of the dielectric constant changes from a negative value to a positive value as the moment when the downstream membrane removal process is completed; when the downstream membrane removal process is completed, control the upstream membrane to end the retention process.

[0102] It is understood that the second-order difference result of the dielectric constant of the outlet side of the subsequent membrane in step S312 is the same as the second-order difference result of the dielectric constant of the outlet side of the subsequent membrane obtained in step S21.

[0103] It should be noted that the change from a negative to a positive value in the second-order difference result of the dielectric constant indicates that the downward trend of the dielectric constant on the outlet side of the downstream membrane has bottomed out and rebounded. This corresponds to the inflection point at which the downstream membrane has completed the removal process of polar dissolved impurities that enter with the permeate. Therefore, this moment is determined as the moment when the downstream membrane removal process is completed.

[0104] It is understood that when the downstream membrane removal process is completed, the influence of the upstream membrane retention process transmitted to the downstream membrane through the oil has been eliminated by the downstream membrane removal process. Therefore, the time when the downstream membrane removal process is completed is taken as the time when the upstream membrane ends its retention process, and the upstream membrane ends its retention process.

[0105] It should be noted that when determining that the second-order difference result of the dielectric constant changes from a negative value to a positive value, the time when the sign of the second-order difference result first changes from negative to positive during the waiting period of the pre-stage film is taken as the standard, and the time when the second-order difference result is equal to zero is not counted as the time of sign change; when the second-order difference result of the dielectric constant does not change from a negative value to a positive value during the waiting period of the pre-stage film, the timeout protection corresponding to the first timeout duration forcibly terminates the retention process of the pre-stage film.

[0106] It should be noted that in step S312, a timeout protection is set for the waiting of the pre-stage membrane. The timing starts from the moment the pre-stage membrane enters step S31. When the duration of waiting for the subsequent membrane removal process to complete exceeds a preset first timeout duration, the retention process of the pre-stage membrane is forcibly terminated. In some embodiments, the first timeout duration is twice the length of the time interval of the stage in which the pre-stage membrane enters step S31.

[0107] S32, when the retention progress of the pre-stage membrane is slower than the retention reference, control the post-stage membrane to insert a backwashing process during the retention process, and determine the time when the pre-stage membrane ends the retention process.

[0108] It is understandable that, such as Figure 3 As shown, in step S32, the retention progress of the pre-stage membrane is slower than the retention reference, that is, the pre-stage membrane is in the retention deceleration state. This indicates that the second-order difference result of the transmembrane pressure difference on the inlet side of the pre-stage membrane is negative while the sign of the retention reference is positive. The formation of the retention layer of the pre-stage membrane is slowed down, and the solid mechanical impurities in the oil entering the subsequent membrane are not sufficiently retained.

[0109] It should be noted that when the retention progress of the pre-stage membrane is slower than the retention benchmark, the content of solid mechanical impurities in the oil entering the post-stage membrane increases. Therefore, the post-stage membrane is controlled to undergo backwashing during the retention process in order to maintain the retention of solid mechanical impurities by the post-stage membrane.

[0110] It should be noted that the backwashing process in step S32 includes two determinations. The first is the determination of entering the backwashing process mode, which is based on the fact that the retention progress of the upstream membrane is slower than the retention benchmark. The second is the determination of triggering backwashing processes sequentially in the process mode, which is based on the fact that the sign of the second-order difference result of the transmembrane pressure difference on the inlet side of the downstream membrane is different from the sign of the retention benchmark of the current stage of the downstream membrane.

[0111] In some embodiments, step S32 includes steps S321 to S323, wherein: S321, a backwashing process is inserted into the retention process of the downstream membrane.

[0112] It is understood that the backwashing process described in step S321 is a process of cleaning the membrane surface of the downstream membrane and restoring the retention capacity of the downstream membrane.

[0113] It should be noted that after the retention progress of the upstream membrane is slower than the retention benchmark, causing the downstream membrane to enter the backwashing process, during the retention process of the downstream membrane, the backwashing process is triggered once every time the sign of the second-order difference result of the transmembrane pressure difference on the inlet side of the downstream membrane is different from the sign of the retention benchmark at the current stage of the downstream membrane.

[0114] S322, during the backwashing process, the update of the retention status of the downstream membrane is paused, and the update of the removal status of the downstream membrane continues; after the backwashing process is completed, the retention status of the downstream membrane is redefined.

[0115] It should be noted that the backwashing process is an action performed by the downstream membrane itself, and the backwashing process will cause disturbance to the transmembrane pressure difference on the inlet side of the downstream membrane.

[0116] It is understandable that if the retention state of the downstream membrane continues to be updated with the second-order difference result of the transmembrane pressure difference on the inlet side of the downstream membrane during the backwashing process, the disturbance will cause the retention state of the downstream membrane to be misjudged. Therefore, the update of the retention state of the downstream membrane is suspended during the backwashing process to keep the retention state of the downstream membrane at the value before the backwashing process started.

[0117] It is understood that the backwashing process disturbs the transmembrane pressure difference at the inlet side of the downstream membrane, but does not change the removal progress reflected by the dielectric constant at the outlet side of the downstream membrane. Therefore, the removal status of the downstream membrane continues to be updated during the execution of the backwashing process.

[0118] Furthermore, after the backwashing process is completed, starting from the moment the backwashing process is completed, the transmembrane pressure difference at the inlet side of the downstream membrane is re-acquired and the second-order differential is re-executed to redetermine the retention state of the downstream membrane.

[0119] S323, when the retention progress of the downstream membrane recovers to meet the retention benchmark, the upstream membrane is controlled to end the retention process.

[0120] It is understood that the retention progress of the downstream membrane in step S323 is restored to meet the retention benchmark, that is, the retention state of the downstream membrane is redefined as the benchmark retention state, which indicates that the retention of solid mechanical impurities by the downstream membrane has been fully restored, and the impact of the retention deceleration of the upstream membrane on the downstream membrane has been eliminated.

[0121] It is understood that the moment when the retention progress of the subsequent membrane recovers to meet the retention benchmark is taken as the moment when the retention process of the preceding membrane ends, and the retention process of the preceding membrane is controlled to end.

[0122] It should be noted that in step S323, a timeout protection is set for the waiting of the pre-stage membrane. The timing starts from the moment the pre-stage membrane enters step S32. When the waiting duration of the pre-stage membrane exceeds a preset second timeout duration, the retention process of the pre-stage membrane is forcibly terminated. In some embodiments, the second timeout duration is twice the length of the time interval of the stage in which the pre-stage membrane enters step S32.

[0123] Through step S3, this embodiment dynamically controls the order in which the downstream membrane performs retention and removal treatments on the oil by combining the retention state of the upstream membrane with the removal state of the downstream membrane. The downstream membrane also determines the moment when the upstream membrane ends its retention treatment by combining the upstream membrane with the downstream membrane, thus achieving a structural match between their operating rhythms. This solves the problem in the prior art where the upstream and downstream membranes operate independently and changes in feed composition are not responded to.

[0124] S4, when the moment when the pre-stage membrane finishes its retention process is reached, control the pre-stage membrane to finish its retention process.

[0125] It is understandable that the moment when the pre-membrane finishes its retention process in step S4 is determined by the combined state in step S3.

[0126] Specifically, in the combined state where the retention progress of the pre-stage membrane is faster than the retention benchmark and the removal progress of the post-stage membrane deviates from the removal benchmark, the moment when the retention process of the pre-stage membrane ends is the moment when the removal process of the post-stage membrane is completed as determined in step S312.

[0127] Specifically, in the combined state where the retention progress of the preceding membrane is slower than the retention benchmark, the moment when the retention process of the preceding membrane ends is the moment when the retention progress of the subsequent membrane, as determined in step S323, recovers to meet the retention benchmark.

[0128] It is understandable that the fore-stage membrane is controlled to stop the retention of oil when the moment when the retention process ends is reached.

[0129] It should be noted that in step S4, a total duration protection is set for the retention process of the pre-stage membrane. The total runtime of the retention process is accumulated from the moment the pre-stage membrane begins its retention process. When the total runtime exceeds a preset forced termination duration, the pre-stage membrane is controlled to end the retention process. In some embodiments, the forced termination duration is twice the total calibrated running time.

[0130] It should be noted that when the total runtime is greater than the forced termination duration, the front-stage membrane is controlled to terminate the retention process regardless of whether the moment when the front-stage membrane ends the retention process as determined by the joint state has been reached.

[0131] It should be noted that the timeout protection based on the stage time interval length in steps S312 and S323, and the total duration protection based on the calibrated total running time in step S4, are two independent and parallel protection layers. The retention treatment of the front membrane ends when the conditions of either of the two protection layers are met.

[0132] It should be noted that the final-stage membrane located at the last stage has no adjacent subsequent membranes, and the end time of the retention process of the final-stage membrane is not determined by the removal state of the subsequent membranes. When the retention reference of the final-stage membrane is not an empty sequence, the retention process of the final-stage membrane ends after the retention state of the final-stage membrane has undergone all the sign transitions recorded by the retention reference of the final-stage membrane; when the retention reference of the final-stage membrane is an empty sequence, the retention process of the final-stage membrane ends when the running time of the final-stage membrane reaches the total time of the calibrated operation.

[0133] It should be noted that when the total runtime of the final stage membrane's retention process is more than twice the total runtime of the calibrated operation, the final stage membrane is controlled to end the retention process.

[0134] Through step S4, this embodiment controls the front-stage membrane to end its retention process when the time determined by the combined state is reached. The time when the front-stage membrane ends its retention process is the time when the retention progress of the front-stage membrane is faster than the retention reference and the removal progress of the rear-stage membrane deviates from the removal reference. The time when the retention progress of the front-stage membrane is slower than the retention reference is the time when the retention progress of the rear-stage membrane recovers to meet the retention reference. This allows the termination time of the front-stage membrane retention process to be determined by the observable change in the influence of the rear-stage membrane on the front-stage membrane process, thus realizing the response of the termination time of the front-stage membrane retention process to the combined state.

[0135] S5, after the pre-stage membrane finishes its retention treatment, when the oil purification level after multi-stage membrane treatment reaches the purification target, the purification treatment of this batch of transformer oil ends.

[0136] It is understandable that the degree of purification of the oil after multi-stage membrane treatment in step S5 is reflected by the dielectric constant of the outlet side of the final membrane. The smaller the dielectric constant of the outlet side of the final membrane, the lower the content of polar dissolved impurities in the oil, and the higher the degree of purification of the oil.

[0137] It should be noted that the purification target mentioned in step S5 is the dielectric constant reference value corresponding to the target purification depth, and the target purification depth is a pre-set purification index.

[0138] It should be noted that the dielectric constant reference value is the dielectric constant of standard transformer oil at the reference temperature when the oil reaches the target purification depth, which is obtained by measurement and fixedly stored at the end of the calibration operation.

[0139] It is understood that the standard transformer oil is a qualified transformer oil that meets the corresponding transformer oil quality standards, and the dielectric constant reference value is obtained by measuring the dielectric constant of the standard transformer oil at the reference temperature.

[0140] In some embodiments, the specific implementation of step S5, where the purification process of this batch of transformer oil ends when the oil purification level after multi-stage membrane treatment reaches the purification target, includes steps S51 to S53, wherein: S51, when the dielectric constant of the oil after the multi-stage membrane treatment is less than or equal to the reference value of the dielectric constant corresponding to the target purification depth, the purification treatment of this batch of transformer oil ends.

[0141] It is understood that the dielectric constant of the oil after the multi-stage membrane treatment in step S51 is the dielectric constant of the outlet side of the final membrane.

[0142] It should be noted that when the dielectric constant at the outlet side of the final membrane is less than or equal to the dielectric constant reference value, the purification degree of the oil reaches the target purification depth, and the purification treatment of this batch of transformer oil is deemed to have met the standard, thus ending the purification process for this batch of transformer oil.

[0143] S52, when the dielectric constant of the oil after the multi-stage membrane treatment is greater than the dielectric constant reference value, steps S1 to S4 are repeated for this batch of transformer oil to increase the number of purification cycles by one.

[0144] It should be noted that when the dielectric constant at the outlet side of the final membrane is greater than the reference value of the dielectric constant, the purification degree of the oil has not reached the target purification depth. Therefore, steps S1 to S4 are repeated for this batch of transformer oil to perform the next purification cycle.

[0145] It is understood that the number of purification cycles is used to record the number of times the purification cycle is performed on this batch of transformer oil. The initial value of the number of purification cycles is 1, and the number of purification cycles is incremented by one each time a purification cycle is completed.

[0146] It should be noted that when steps S1 to S4 are re-executed for this batch of transformer oil, the running time of each membrane stage, as well as the timeout time in steps S312, S323 and S4, are all recalculated from the moment steps S1 to S4 are re-executed.

[0147] S53, when the number of purification cycles exceeds the preset maximum number of purification cycles, the purification process for this batch of transformer oil ends.

[0148] It is understood that the maximum number of purification cycles mentioned in step S53 is set and stored during the initialization of the multi-stage filter press system.

[0149] It should be noted that when the number of purification cycles exceeds the maximum number of purification cycles, regardless of the relationship between the dielectric constant at the outlet of the final membrane and the reference value of the dielectric constant, the purification process for this batch of transformer oil will be terminated, and the purification of this batch of transformer oil will be recorded as not meeting the standard.

[0150] It is understood that step S53 uses the maximum number of purification cycles as the termination condition for the purification cycle, so that the purification treatment of this batch of transformer oil ends within a limited number of purification cycles.

[0151] In step S5, this embodiment determines whether the purification of this batch of transformer oil meets the standard by comparing the dielectric constant of the outlet side of the final membrane with the reference value of the dielectric constant, and uses the maximum number of purification cycles as the termination condition of the purification cycle, so that the purification process ends within a limited number of purification cycles while ensuring that the purification of this batch of transformer oil meets the standard.

[0152] In some embodiments, the transformer oil multi-stage pressure filtration membrane purification method further includes, in addition to steps S1 to S5, a batch-to-batch initial operation sequence recombination process, wherein the recombination process is performed after the purification of the current batch of transformer oil is completed and before the purification of the next batch of transformer oil begins.

[0153] It is understood that the reorganization process adjusts the initial operation sequence of the next batch of the pre-stage membranes based on the timing of changes in the retention status of the current batch of pre-stage membranes relative to the retention baseline, in order to prevent the trend of premature contamination.

[0154] Specifically, the moment when the retention state of the pre-membrane in this batch changes from the baseline retention state to the gel accelerated blocking state is recorded, and this moment is recorded as the gel transition moment.

[0155] Furthermore, the gel transition time is used to find the stage in which the gel transition time is located among the multiple stages of the pre-membrane, and the stage in which the gel transition time is located is recorded as the gel transition stage, and the start time of the time interval of the gel transition stage is recorded as the gel transition reference time.

[0156] Furthermore, the gel transition time is compared with the gel transition reference time. When the gel transition time is earlier than the gel transition reference time, the accelerated blockage of the gel-state sludge in the pre-membrane occurs earlier than under the calibration operation, and a pre-retention operation is inserted at the beginning of the next batch of pre-membrane purification operation.

[0157] It is understood that the pre-retention operation is to retain gel-like impurities in the oil, which are solid mechanical impurities that form the gel-like sludge, in order to retain the gel-like impurities in advance in the next batch and inhibit the premature aggregation of the gel-like sludge on the film surface.

[0158] Furthermore, during the pre-retention operation, a second-order difference is performed on the transmembrane pressure difference at the inlet side of the preceding membrane. When the sign change direction of the second-order difference result is the same as the sign change direction recorded at the starting boundary of the gel transition stage, the pre-retention operation ends.

[0159] Furthermore, starting from the moment the pre-withholding operation ends, steps S1 and S3 are executed.

[0160] It should be noted that a timeout protection is set for the pre-withdrawal operation. When the execution duration of the pre-withdrawal operation exceeds a preset pre-withdrawal timeout duration, the pre-withdrawal operation is forcibly terminated. In some embodiments, the pre-withdrawal timeout duration is twice the length of the time interval of the gel transition stage.

[0161] Optionally, when the gel transition stage is the first stage, the execution time of the pre-withdrawal operation reaches the time interval length of the first stage as the exit condition for the pre-withdrawal operation, and the pre-withdrawal operation ends when the execution time of the pre-withdrawal operation reaches the time interval length of the first stage.

[0162] Optionally, when two or more batches of gel transition times have been accumulated, the stage with the highest frequency of occurrence in the gel transition stages of each batch is used as the reference stage for exiting the pre-withdrawal operation, and the pre-withdrawal timeout duration is twice the time interval length of the reference stage.

[0163] Furthermore, the recombination process also includes adjusting the initial operation sequence of the next batch of the pre-stage membranes based on the moment when the retention state of the current batch of pre-stage membranes changes from the baseline retention state to the retention deceleration state.

[0164] Specifically, the moment when the retention state of the pre-phase membrane in this batch changes from the reference retention state to the retention deceleration state is recorded, and this moment is recorded as the deceleration transition moment. The stage in which the deceleration transition moment is located is found among multiple stages of the pre-phase membrane based on the deceleration transition moment, and the stage in which the deceleration transition moment is located is recorded as the deceleration transition stage. The start time of the time interval of the deceleration transition stage is recorded as the deceleration transition reference moment.

[0165] Furthermore, the deceleration transition time is compared with the deceleration transition reference time. When the deceleration transition time is earlier than the deceleration transition reference time, a pre-separation operation is inserted at the beginning of the next batch of the pre-membrane purification operation, after the pre-retention operation. The pre-separation operation separates large particles of solid mechanical impurities with larger particle sizes in the oil.

[0166] Furthermore, during the pre-separation operation, a second-order differential is performed on the transmembrane pressure difference at the inlet side of the preceding membrane. When the sign change direction of the second-order differential result is the same as the sign change direction recorded at the starting boundary of the deceleration transition stage, the pre-separation operation ends.

[0167] It should be noted that a timeout protection is set for the pre-separation operation. When the execution duration of the pre-separation operation exceeds a preset pre-separation timeout duration, the pre-separation operation is forcibly terminated. In some embodiments, the pre-separation timeout duration is twice the length of the time interval of the deceleration transition phase.

[0168] Optionally, when the deceleration transition phase is the first phase, the execution time of the pre-separation operation reaches the time interval length of the first phase as the exit condition for the pre-separation operation, and the pre-separation operation ends when the execution time of the pre-separation operation reaches the time interval length of the first phase.

[0169] Optionally, when two or more batches of deceleration transition moments have been accumulated, the phase with the highest frequency of occurrence in each batch of deceleration transition phases is taken as the reference phase for exiting the pre-separation operation, and the pre-separation timeout duration is taken as twice the time interval length of the reference phase.

[0170] Furthermore, starting from the moment the pre-separation operation ends, steps S1 and S3 are executed.

[0171] It is understood that when the next batch of the preceding membranes is inserted into both the pre-retention operation and the pre-separation operation, the pre-retention operation is performed before the pre-separation operation.

[0172] By recombining the initial operation sequence between batches, this embodiment uses the time-series comparison of the change in the retention state of the pre-stage membrane in this batch with the retention benchmark to drive the recombination of the initial operation sequence structure of the next batch. This enables the multi-stage filter press system to prevent the trend of early fouling and solves the problem of the lack of an inter-batch experience transfer mechanism in existing methods.

[0173] In some embodiments, the transformer oil multi-stage pressure filtration and purification method further includes coordinated processing of inter-stage operation timing.

[0174] It is understood that the running time of the subsequent membrane is used to obtain the running time of the subsequent membrane, and the subsequent membrane uses the running time to locate the current stage among the multiple stages of the subsequent membrane.

[0175] Specifically, during the pre-retention operation performed by the upstream membrane, the running time of the downstream membrane is paused, so that the retention and removal states of the downstream membrane remain at the values ​​before the pre-retention operation began.

[0176] It is understandable that during the pre-retention operation performed by the pre-stage membrane, the pre-stage membrane has not yet normally delivered oil to the subsequent membrane. If the running time of the subsequent membrane continues to advance at this time, the stage positioned by the running time of the subsequent membrane will not correspond to the oil actually received by the subsequent membrane, causing a mismatch between the state timing reference of the subsequent membrane and the interstage oil delivery relationship. Therefore, the running time of the subsequent membrane is suspended.

[0177] Furthermore, after the pre-retention operation of the preceding membrane is completed, the running time of the following membrane is synchronized with the running time of the preceding membrane and restarted. From the restart time, the retention and removal states of the following membrane are restored.

[0178] It is understandable that after the pre-retention operation of the preceding membrane is completed, the preceding membrane begins to normally deliver oil to the following membrane, so that the running time of the following membrane is synchronized with the running time of the preceding membrane and restarted, so that the stage of the following membrane located by the running time corresponds to the oil actually received by the following membrane, and the state timing reference of the following membrane is consistent with the interstage oil delivery relationship.

[0179] It should be noted that during the pre-separation operation performed by the upstream membrane, the running time of the downstream membrane is also paused, so that the retention and removal states of the downstream membrane remain at the values ​​before the pre-separation operation began; after the pre-separation operation of the upstream membrane is completed, the running time of the downstream membrane is synchronized with the running time of the upstream membrane and restarted, and the retention and removal states of the downstream membrane are restored from the restart time.

[0180] Through the coordinated processing of the inter-stage operation timing, this embodiment ensures that the state timing reference of the subsequent membrane in the multi-stage filter press system is consistent with the inter-stage oil delivery relationship, thus solving the problem of timing reference mismatch of the subsequent membrane during the pretreatment operation of the preceding membrane.

[0181] Example 2 is an embodiment of the present invention, which provides a multi-stage pressure filtration and purification system for transformer oil, comprising: The state determination unit is used to determine the retention state of the upstream membrane and the removal state of the downstream membrane. The processing control unit is used to control the order in which the subsequent membrane performs retention and removal treatments on the oil based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and to determine the time when the preceding membrane ends the retention treatment. The retention termination unit is used to control the front-stage membrane to end the retention process when the time when the retention process of the front-stage membrane ends is reached. The purification termination unit is used to terminate the purification process of this batch of transformer oil when the oil purification level reaches the purification target after the pre-stage membrane has finished its retention treatment and after the multi-stage membrane treatment has completed its retention treatment.

[0182] This embodiment also provides an electronic device applicable to a transformer oil multi-stage pressure filtration membrane purification method, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the transformer oil multi-stage pressure filtration membrane purification method proposed in the above embodiment.

[0183] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements a transformer oil multi-stage pressure filter membrane filtration and purification method as proposed in the above embodiment.

[0184] The storage medium proposed in this embodiment belongs to the same inventive concept as the method for implementing a multi-stage pressure filtration and purification method for transformer oil proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0185] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0186] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for purifying transformer oil through multi-stage pressure filtration membranes, characterized in that, include: The retention status of the preceding membrane is determined based on the progress of impurity retention by the preceding membrane. The removal status of the subsequent membrane is determined based on the progress of impurity removal by the subsequent membrane. Based on the combined state of the retention state of the pre-stage membrane and the removal state of the post-stage membrane, the order in which the post-stage membrane performs retention and removal treatments on the oil is controlled, and the time when the pre-stage membrane ends the retention treatment is determined. When the moment when the pre-membrane finishes its retention process is reached, the pre-membrane is controlled to finish its retention process. After the pre-membrane finishes its retention treatment, the purification treatment of this batch of transformer oil ends when the oil purified by the multi-stage membrane treatment reaches the purification target.

2. The method for purifying transformer oil by multi-stage pressure filtration membrane as described in claim 1, characterized in that, The retention status of the preceding membrane is determined based on the progress of impurity retention by the preceding membrane. The removal status of the subsequent membrane is determined based on the progress of impurity removal by the subsequent membrane, including: The transmembrane pressure difference at the inlet side of the fore-stage membrane is subjected to a second-order differential. When the sign of the second-order differential result is the same as the sign of the pre-calibrated retention reference, the fore-stage membrane is in a state where the retention progress conforms to the retention reference. When the sign of the second-order differential result is different from the sign of the retention reference, the fore-stage membrane is in a state where the retention progress deviates from the retention reference. A first-order difference is performed on the dielectric constant at the outlet side of the subsequent membrane. When the sign of the first-order difference result is the same as the sign of the pre-calibrated removal reference, the subsequent membrane is in a state where the removal progress conforms to the removal reference. When the sign of the first-order difference result is different from the sign of the removal reference, the subsequent membrane is in a state where the removal progress deviates from the removal reference.

3. The method for purifying transformer oil using a multi-stage pressure filtration membrane as described in claim 2, characterized in that, The method of controlling the order of oil retention and removal by the subsequent membrane based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and determining the time when the preceding membrane ends the retention process, includes: When the retention progress of the preceding membrane is faster than the retention reference, and the removal progress of the following membrane deviates from the removal reference, the removal process of the following membrane is adjusted to be performed before the retention process. The time when the dielectric constant of the outlet side of the downstream membrane changes from a negative value to a positive value is determined as the time when the downstream membrane removal process is completed. When the downstream membrane removal process is completed, the upstream membrane is controlled to end the retention process.

4. The method for purifying transformer oil using a multi-stage pressure filtration membrane as described in claim 3, characterized in that, The purification process for this batch of transformer oil ends when the oil purification level reaches the target after multi-stage membrane treatment, including: When the dielectric constant of the oil after the multi-stage membrane treatment is less than or equal to the reference value of the dielectric constant corresponding to the target purification depth, the purification treatment of this batch of transformer oil ends. When the dielectric constant of the oil after multi-stage membrane treatment is greater than the dielectric constant reference value, the retention state of the front membrane and the removal state of the back membrane are re-determined for this batch of transformer oil, the order of retention and removal treatment of the oil by the back membrane is re-controlled according to the combined state, the retention treatment of the front membrane is re-controlled to end, and the number of purification cycles is incremented by one. The purification process for this batch of transformer oil ends when the number of purification cycles exceeds the preset maximum number of purification cycles.

5. The method for purifying transformer oil using a multi-stage pressure filtration membrane as described in claim 4, characterized in that, Also includes: After the purification treatment of this batch of transformer oil is completed and before the purification treatment of the next batch of transformer oil begins, the moment when the retention progress of the front membrane in this batch is faster than the retention benchmark is determined and recorded as the gel transition moment. Compare the gel transition time with the transition time corresponding to the retention benchmark.

6. The method for purifying transformer oil using a multi-stage pressure filtration membrane as described in claim 5, characterized in that, The comparison of the gel transition time with the transition time corresponding to the retention benchmark includes: When the gel transition time is earlier than the transition time corresponding to the retention benchmark, a pre-retention operation is inserted at the beginning of the next batch of the pre-membrane purification operation. The pre-retention operation retains gel-like impurities in the oil. During the pre-retention operation, the transmembrane pressure difference at the inlet side of the front membrane is subjected to a second-order differential. When the sign change direction of the second-order differential result is the same as the corresponding change direction of the retention reference, the pre-retention operation is terminated. From the moment the pre-retention operation ends, operations are performed to determine the retention state of the preceding membrane and to control the order in which the subsequent membrane performs retention and removal treatments on the oil.

7. The method for purifying transformer oil by multi-stage pressure filtration membrane as described in claim 6, characterized in that, Also includes: During the pre-retention operation performed by the upstream membrane, the running time of the downstream membrane is paused, so that the retention and removal states of the downstream membrane remain at the values ​​before the pre-retention operation began. After the pre-retention operation of the preceding membrane is completed, the running time of the following membrane is synchronized with the running time of the preceding membrane and restarted. From the moment of restart, the retention and removal states of the subsequent membrane are restored and determined.

8. A transformer oil multi-stage pressure filtration membrane purification system, employing the transformer oil multi-stage pressure filtration membrane purification method as described in any one of claims 1 to 7, characterized in that, include: The state determination unit is used to determine the retention state of the upstream membrane and the removal state of the downstream membrane. The processing control unit is used to control the order in which the subsequent membrane performs retention and removal treatments on the oil based on the combined state of the retention state of the preceding membrane and the removal state of the subsequent membrane, and to determine the time when the preceding membrane ends the retention treatment. The retention termination unit is used to control the front-stage membrane to end the retention process when the time when the retention process of the front-stage membrane ends is reached. The purification termination unit is used to terminate the purification process of this batch of transformer oil when the oil purification level reaches the purification target after the pre-stage membrane has finished its retention treatment and after the multi-stage membrane treatment has completed its retention treatment.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the transformer oil multi-stage pressure filter membrane filtration and purification method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the multi-stage pressure filter membrane filtration and purification method for transformer oil according to any one of claims 1 to 7.

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