Oxidation stability evaluation method, detection equipment and detection method for agent-free transformer oil

Abstract

The invention provides an oxidation stability evaluation method, detection equipment and a detection method for agent-free transformer oil, and belongs to the technical field of power grid power transmission and transformation. According to the method, copper wires are added into the agent-free transformer oil, air is introduced into the agent-free transformer oil at a preset experimental temperature in a preset experimental period, oxidation of the agent-free transformer oil is accelerated, and the conductivity value of volatile acid in the oil oxidation process is continuously monitored; and evaluating the oxidation stability of the transformer oil without the additive according to the conductivity value of the volatile acid in the preset experimental period. According to the method, the oxidation stability evaluation efficiency of the agent-free transformer oil is improved, the working intensity and technical requirements of operators are reduced, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of power grid transmission and transformation technology, and particularly to additive-free transformer oil for high-voltage and ultra-high-voltage power transformers. In particular, it relates to a method, testing equipment, and testing method for evaluating the oxidation stability performance of additive-free transformer oil. Background Technology

[0002] During operation, transformer oil in power transformers is subject to oxidation due to factors such as high-voltage electric fields, high temperatures, and catalysis by metallic materials. This oxidation leads to a decline in its insulation performance and reduces the transformer's service life. Therefore, the oxidation resistance of transformer oil is a very important indicator, a crucial basis for classifying transformer oil grades, and a primary criterion for transformer manufacturers when selecting transformer oil.

[0003] Currently, the main methods used domestically and internationally for evaluating the oxidation stability of transformer oil include NBSH / T0811, SH / T0206, ASTM D2440, and IEC 61125. The principle is as follows: at a specified temperature (100℃, 110℃, or 120℃), under the catalytic action of copper, and within a specified experimental period of 164 hours or 500 hours, an oxidation experiment is conducted by introducing oxygen or air. The acid value and precipitation or dielectric loss factor of the oxidized oil are measured. The oxidation stability of the transformer oil is determined by the magnitude of the acid value, precipitation, and dielectric loss factor of the oxidized oil.

[0004] According to NBSHT0811 or IEC61125 methods, the oxidation stability of unadulterated transformer oil is evaluated by conducting a 164-hour test at 120°C. The acid value and precipitation or dielectric loss factor of the oxidized oil are measured. The magnitude of these parameters determines whether the oxidation stability of the unadulterated transformer oil meets the corresponding standard requirements. Determining the acid value, precipitation, and dielectric loss factor of oxidized oil requires a large amount of reagents, making the process complex, increasing the workload of operators, and requiring higher technical skills, thus reducing the efficiency of transformer oil development and evaluation. Summary of the Invention

[0005] To address the problems of existing technologies and improve the efficiency of evaluating the oxidation stability performance of additive-free transformer oil, reduce the workload and technical requirements for operators, and lower costs, this invention provides a method, testing equipment, and testing method for evaluating the oxidation stability performance of additive-free transformer oil. The method utilizes a constant-temperature metal bath, oxygen tube, absorption tube, air source, and copper wire for experiments. During the experiment, the conductivity value of volatile acid values ​​during oil oxidation is continuously and automatically monitored. The oxidation stability performance of additive-free transformer oil is determined by the conductivity value of volatile acids over 164 hours, thus improving the efficiency of evaluating the oxidation stability performance of additive-free transformer oil, reducing the workload and technical requirements for operators, and lowering costs. The results show good consistency with those obtained using equipment employing the NBSH / T0811 method over 164 hours, providing technical support for the automatic evaluation of the oxidation stability performance of additive-free transformer oil.

[0006] This invention provides a method for evaluating the oxidation stability of additive-free transformer oil. Copper wire is added to the additive-free transformer oil, and air is introduced into the additive-free transformer oil at a preset experimental temperature and within a preset experimental period to accelerate the oxidation of the additive-free transformer oil. The conductivity value of volatile acids during the oil oxidation process is continuously monitored.

[0007] The oxidation stability of unadulterated transformer oil is evaluated by measuring the conductivity of volatile acids within a preset experimental period. If the conductivity of volatile acids within the preset experimental period is greater than or equal to a preset threshold, the oxidation stability of the unadulterated transformer oil is deemed to meet the requirements. If the conductivity of volatile acids within the preset experimental period is less than or greater than the preset threshold, the oxidation stability of the unadulterated transformer oil is deemed to meet the requirements.

[0008] This invention provides a testing device for evaluating the oxidation stability performance of additive-free transformer oil. Utilizing the aforementioned method for evaluating the oxidation stability performance of additive-free transformer oil, the device includes: a constant-temperature metal bath, an oxidation tube, an absorption tube, an air source, a conductivity probe, and a control and analysis system. The oxidation tube is inserted into the constant-temperature metal bath and is used to hold additive-free transformer oil and copper wire. The air source is connected to the oxidation tube. The absorption tube is positioned outside the constant-temperature metal bath and is also connected to the absorption tube. The conductivity probe is placed inside the absorption tube. The other end of the conductivity probe is connected to the control and analysis system, which processes and calculates the collected conductivity data of the water in the absorption tube.

[0009] Preferably, the oxidation tube includes a vent pipe and an oil filling pipe, wherein the vent pipe is inserted into the oil filling pipe.

[0010] Preferably, the absorption tube comprises an air guide tube, a water filling tube, and an end cap, wherein the air guide tube and the conductivity probe are fixed by the end cap and inserted into the water filling tube.

[0011] Preferably, the end cap is made of polytetrafluoroethylene.

[0012] Preferably, the constant temperature metal bath includes a metal bath controller, a multi-point temperature sensor, a metal aluminum block bath, an insulation box, a heat insulation plate, several heating strips and a heating plate. The metal bath controller is connected to the multi-point temperature sensor, the several heating strips and the heating plate. The metal bath controller, the multi-point temperature sensor and the metal aluminum block bath are all set inside the insulation box, and the heat insulation plate is set outside the insulation box.

[0013] Preferably, the oxide tube is made of glass.

[0014] Preferably, the absorption tube is made of glass.

[0015] This invention provides a method for evaluating the oxidation stability performance of additive-free transformer oil, utilizing the aforementioned testing equipment for evaluating the oxidation stability performance of additive-free transformer oil, and comprising the following steps:

[0016] S1. Take a sample of transformer oil without additives at a preset dosage and filter it with filter paper; cut copper wire to a preset length, polish it, and roll it into a copper coil for later use.

[0017] S2, add a sample of unadulterated transformer oil and a copper coil to the assembled oxide tube;

[0018] S3, place the oxidation tube in the constant temperature metal bath, and fix the absorption tube on the outside of the constant temperature metal bath;

[0019] S4, connect one end of the vent pipe in the oxidation tube to an air source, and connect the other end of the vent pipe to the air guide pipe in the absorption tube;

[0020] S5, insert one end of the conductivity probe into the water-filling tube in the absorption tube, and connect the other end of the conductivity probe to the control and analysis system;

[0021] S6, set the temperature of the constant temperature metal bath, and set the experimental temperature, gas flow rate, acquisition cycle, and conductivity judgment value on the control and analysis system to start the experiment;

[0022] S7. During the experiment, the conductivity in the absorption tube is collected and recorded periodically, and the experiment ends.

[0023] Preferably, in step S7, the conductivity value in the absorption tube at the end time of a set test cycle is used as the conductivity measurement result for that test cycle.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] The structure and material of the oxidation tube in this invention are consistent with the requirements of the NB SH / T 0811 method for evaluating the oxidation stability of transformer oil. The oxidation stability of the additive-free transformer oil is determined by monitoring the conductivity of the aqueous solution in the absorption tube and using the conductivity value after 164 hours. This method shows excellent consistency with the 164-hour oxidation results obtained using the equipment employing the NB SH / T 0811 method. It eliminates the need to test the acid value, precipitation, and dielectric loss factor of the oxidized oil, reducing the use of large amounts of reagents. The entire process is automated, reducing the complexity and intensity of the work and the higher technical requirements for operators, thus improving the efficiency of the development and evaluation of additive-free transformer oil. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a testing device for evaluating the oxidation stability performance of additive-free transformer oil according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram showing the connection between the oxidation tube and the absorption tube according to an embodiment of the present invention.

[0028] In the diagram, 1-constant temperature metal bath, 2-air source, 3-oxidation tube, 4-absorption tube, 5-conductivity probe, 6-control and analysis system, 7-vent pipe, 8-oil loading pipe, 9-vent pipe, 10-end cap, 11-water loading pipe. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below.

[0030] This invention provides a method for evaluating the oxidation stability of additive-free transformer oil. Copper wire is added to the additive-free transformer oil, and air is introduced into the additive-free transformer oil at a preset experimental temperature and within a preset experimental period to accelerate the oxidation of the additive-free transformer oil. The conductivity value of volatile acids during the oil oxidation process is continuously monitored.

[0031] The oxidation stability of unadulterated transformer oil is evaluated by measuring the conductivity of volatile acids within a preset experimental period. If the conductivity of volatile acids within the preset experimental period is greater than or equal to a preset threshold, the oxidation stability of the unadulterated transformer oil is deemed to meet the requirements. If the conductivity of volatile acids within the preset experimental period is less than or greater than the preset threshold, the oxidation stability of the unadulterated transformer oil is deemed to meet the requirements.

[0032] The working principle of this invention is as follows: At a stable temperature, copper wire and additive-free transformer oil are added, and air at a preset flow rate is introduced to accelerate the oxidation of the oil. Throughout the entire experimental cycle, the conductivity value of volatile acids during the oil oxidation process is continuously and automatically monitored. The oxidation stability performance of the additive-free transformer oil is determined by the conductivity value of volatile acids over 164 hours. If the conductivity value is greater than or equal to a preset threshold, the oxidation stability performance of the additive-free transformer oil is deemed to meet the requirements. If the conductivity value of volatile acids within the preset experimental cycle is less than or greater than the preset threshold, the oxidation stability performance of the additive-free transformer oil is deemed to meet the requirements.

[0033] This invention provides a testing device for evaluating the oxidation stability performance of additive-free transformer oil. Utilizing the aforementioned method for evaluating the oxidation stability performance of additive-free transformer oil, the device includes: a constant-temperature metal bath 1, an oxidation tube 3, an absorption tube 4, an air source 2, a conductivity probe 5, and a control and analysis system 6. The oxidation tube 3 is inserted into the constant-temperature metal bath 1 and is used to hold additive-free transformer oil and copper wire. The air source 2 is connected to the oxidation tube 3. The absorption tube 4 is located outside the constant-temperature metal bath 1, and the oxidation tube 3 is also connected to the absorption tube 4. The conductivity probe 5 is placed inside the absorption tube 4. The other end of the conductivity probe 5 is connected to the control and analysis system 6, which processes and calculates the collected conductivity data of the water in the absorption tube 4.

[0034] According to certain embodiments of the present invention, the oxidation tube 3 includes a vent pipe 7 and an oil filling pipe 8, wherein the vent pipe 7 is inserted into the oil filling pipe 8.

[0035] According to certain specific embodiments of the present invention, the absorption tube 4 comprises an air guide tube 9, a water filling tube 11 and an end cap 10, wherein the air guide tube 9 and the conductivity probe 5 are fixed by the end cap 10 and inserted into the water filling tube 11.

[0036] According to certain embodiments of the present invention, the end cap 10 is made of polytetraethylene.

[0037] According to certain specific embodiments of the present invention, the constant temperature metal bath 1 includes a metal bath controller, a multi-point temperature sensor, a metal aluminum block bath, an insulation box, a heat insulation plate, several heating strips and a heating plate. The metal bath controller is connected to the multi-point temperature sensor, the several heating strips and the heating plate. The metal bath controller, the multi-point temperature sensor and the metal aluminum block bath are all arranged inside the insulation box. The heat insulation plate is arranged outside the insulation box.

[0038] According to certain specific embodiments of the present invention, the oxide tube 3 is made of glass.

[0039] According to certain specific embodiments of the present invention, the absorption tube 4 is made of glass.

[0040] This invention provides a method for evaluating the oxidation stability performance of additive-free transformer oil, utilizing the aforementioned testing equipment for evaluating the oxidation stability performance of additive-free transformer oil, and comprising the following steps:

[0041] S1. Take a sample of transformer oil without additives at a preset dosage and filter it with filter paper; cut copper wire to a preset length, polish it, and roll it into a copper coil for later use.

[0042] S2, add a sample of unadulterated transformer oil and a copper coil to the assembled oxide tube 3;

[0043] S3, place the oxidation tube 3 in the constant temperature metal bath 1, and fix the absorption tube 4 on the outside of the constant temperature metal bath 1;

[0044] S4, connect one end of the vent pipe 7 in the oxidation pipe 3 to the air source 2, and connect the other end of the vent pipe 7 to the air guide pipe 9 in the absorption pipe 4;

[0045] S5, insert one end of the conductivity probe 5 into the water-filling tube 11 in the absorption tube 4, and connect the other end of the conductivity probe 5 to the control and analysis system 6;

[0046] S6, set the temperature of the constant temperature metal bath 1, and set the experimental temperature, gas flow rate, acquisition cycle, and conductivity judgment value on the control and analysis system 6, and start the experiment;

[0047] S7. During the experiment, the conductivity of the absorption tube 4 is collected and recorded periodically, and the experiment ends.

[0048] According to certain specific embodiments of the present invention, in step S7, the conductivity value in the absorption tube 4 at a set end time of the test cycle is used as the conductivity measurement result of the test cycle.

[0049] The working principle of this invention is as follows: At a stable temperature, copper wire and additive-free transformer oil are added, and air at a preset flow rate is introduced to accelerate the oxidation of the oil. Throughout the entire experimental cycle, the conductivity value of volatile acids during the oil oxidation process is continuously and automatically monitored. The oxidation stability performance of the additive-free transformer oil is determined by the conductivity value of volatile acids over 164 hours. If the conductivity value is greater than or equal to a preset threshold, the oxidation stability performance of the additive-free transformer oil is deemed to meet the requirements. If the conductivity value of volatile acids within the preset experimental cycle is less than or greater than the preset threshold, the oxidation stability performance of the additive-free transformer oil is deemed to meet the requirements.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An evaluation method for the oxidation stability of unadditive transformer oil, characterized in that: copper wire is added to the unadditive transformer oil, air is introduced into the unadditive transformer oil at a preset experimental temperature and for a preset experimental period to accelerate the oxidation of the unadditive transformer oil, and the conductivity value of volatile acid in the oxidation process of the oil is continuously monitored; the oxidation stability of the unadditive transformer oil is evaluated by the conductivity value of volatile acid within the preset experimental period, and when the conductivity value of volatile acid within the preset experimental period is greater than or equal to a preset threshold value, it is determined that the oxidation stability of the unadditive transformer oil meets the requirements; and when the conductivity value of volatile acid within the preset experimental period is less than the preset threshold value, it is determined that the oxidation stability of the unadditive transformer oil meets the requirements.

2. The evaluation method for the oxidation stability of unadditive transformer oil according to claim 1, comprising: a constant temperature metal bath, an oxidation tube, an absorption tube, an air source, a conductivity probe, and a control and analysis system, the oxidation tube is inserted into the constant temperature metal bath, the oxidation tube is used to contain unadditive transformer oil and copper wire, the air source is connected with the oxidation tube, the absorption tube is arranged outside the constant temperature metal bath, the oxidation tube is also connected with the absorption tube, and the conductivity probe is placed in the absorption tube; the other end of the conductivity probe is connected with the control and analysis system, and the control and analysis system processes and calculates the conductivity data of water collected in the absorption tube.

3. The oxidation tube according to claim 2, comprising an air pipe and an oil pipe, and the air pipe is inserted into the oil pipe.

2. An apparatus for evaluating the oxidation stability of an unadditivated transformer oil, characterized in that it comprises:

4. The absorption tube according to claim 2, comprising an air guide pipe, a water pipe and an end cap, and the air guide pipe and the conductivity probe are fixed and inserted into the water pipe through the end cap.

3. The apparatus for evaluating the oxidation stability of non-doped transformer oil according to claim 2, characterized by, 5. The end cap according to claim 4, which is made of polytetraethylene.

4. The apparatus for evaluating the oxidation stability of non- additive transformer oil according to claim 3, characterized by 6. The constant temperature metal bath according to claim 2, comprising a metal bath controller, a multi-point temperature sensor, a metal aluminum block bath, a heat preservation box, an insulation plate, a plurality of heating belts and a heating disc, the metal bath controller is connected with the multi-point temperature sensor, the plurality of heating belts and the heating disc, the metal bath controller, the multi-point temperature sensor and the metal aluminum block bath are arranged in the heat preservation box, and the heat preservation box is externally provided with the insulation plate.

5. The apparatus for evaluating the oxidation stability of non- additive transformer oil according to claim 4, characterized by 7. The absorption tube according to claim 2, which is made of glass.

6. The apparatus for evaluating the oxidation stability of non- additive transformer oil according to claim 4, wherein 8. The oxidation tube according to claim 2, which is made of glass.

7. The apparatus for evaluating the oxidation stability of non-doped transformer oil according to claim 4, wherein 9. The evaluation method for the oxidation stability of unadditive transformer oil according to any one of claims 4-8, comprising the following steps:

8. The apparatus according to claim 4, wherein S1. Filtering a preset amount of unadditive transformer oil sample with filter paper, cutting a copper wire of a preset length, polishing the copper wire, winding the copper wire into a copper coil, and reserving the copper coil; 9. A method for evaluating the oxidation stability of an unadditivated transformer oil, characterized in that, S2. Adding the unadditive transformer oil sample and the copper coil into the assembled oxidation tube; S3. Placing the oxidation tube in the constant temperature metal bath, and fixing the absorption tube outside the constant temperature metal bath; S4. Connecting one end of the air pipe in the oxidation tube with the air source, and connecting the other end of the air pipe with the air guide pipe in the absorption tube; S5. Inserting one end of the conductivity probe into the water pipe in the absorption tube, and connecting the other end of the conductivity probe with the control and analysis system. ​ ​ S6, set the temperature of the constant temperature metal bath, set the experimental temperature, gas flow, collection period, conductivity determination value on the control and analysis system, and start the experiment; S7, during the experiment, periodically collect and record the conductivity in the absorption tube, and end the experiment.

10. The method for evaluating the oxidation stability of non-doped transformer oil according to claim 9, characterized in that, In step S7, the conductivity value in the absorption tube at a set test period end time point is taken as the conductivity measurement result of the test period.

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