CN111474448B - Method for determining withstand voltage value of factory test after maintenance of converter transformer - Google Patents
Method for determining withstand voltage value of factory test after maintenance of converter transformer Download PDFInfo
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- CN111474448B CN111474448B CN202010111720.0A CN202010111720A CN111474448B CN 111474448 B CN111474448 B CN 111474448B CN 202010111720 A CN202010111720 A CN 202010111720A CN 111474448 B CN111474448 B CN 111474448B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
Abstract
The invention discloses a method for determining a withstand voltage value of a factory test of a converter transformer after overhaul, which relates to the technical field of high-voltage electrical equipment detection and comprises the following steps: sampling insulation paper with the highest lead temperature rise in each part of the converter transformer after maintenance, measuring the viscosity-average polymerization degree of a plurality of groups of cellulose electrical insulation materials on the insulation paper samples, and determining the factory test withstand voltage value of the converter transformer after maintenance based on the relation between the polymerization degree of the insulation paper and the factory test voltage value after maintenance. The method can accurately determine the factory test withstand voltage value of the converter transformer after overhaul as much as possible, can furthest test the overhaul quality of the converter transformer, ensures that the insulation of the converter transformer meets the operation and use requirements, avoids the irreversible damage of the overhigh test voltage value to the insulation inside the converter transformer which has been used for a long time, and can also avoid the situation that the overhigh test voltage value cannot fully and effectively detect the converter transformer which is just put into operation soon.
Description
Technical Field
The invention relates to the technical field of high-voltage electrical equipment detection, in particular to a method for determining a withstand voltage value of a factory test after a converter transformer is overhauled.
Background
The overhaul work needs to be carried out after major failure occurs to the converter transformer, and the factory test needs to be carried out after the overhaul is finished, wherein the factory test is the most important means for inspecting the overhaul quality of the converter transformer and is the most strict inspection checkpoint for judging whether the converter transformer can be put into operation or not. After the maintenance of the converter transformer is completed, the structure and the electrical performance of the converter transformer are reduced to a certain extent compared with those of a newly manufactured converter transformer, generally, conventional test items such as transformation ratio, direct current resistance, dielectric loss, insulation resistance and the like after the maintenance of the converter transformer are the same as the method and the judgment standard when the new converter transformer is subjected to factory test, but the conventional test items related to withstand voltage high-voltage test are generally processed in the following way: for example, a network side alternating current external voltage withstand test, a valve side alternating current external voltage withstand test, a direct current external voltage and polarity reversal test, a lightning and operation impact test and the like, which have certain destructiveness and can cause irreversible damage to the internal insulation of the converter transformer, the voltage withstand test is carried out by adopting a method for reducing the test voltage in the past, and the overhaul quality of the converter transformer is detected on the premise of protecting the internal insulation of the converter transformer as much as possible by adopting 80% of factory test values (the voltage withstand value after overhaul has no standard regulation and is generally determined by negotiation between a maintenance side and an operation and maintenance side).
The voltage withstanding value of the above-mentioned processing method is low to protect the internal insulation of the converter transformer, which has the following problems in practical operation: when the new converter transformer leaves the factory and is tested by a 100% test voltage value (namely a standard specified value), if 80% test voltage values are adopted after the converter transformer is overhauled after faults are finished under different operation years and different insulation material states, the assessment effect of the factory test on internal insulation is very limited, namely, the weak link of the internal insulation cannot be fully detected, such as extreme conditions, when the converter transformer is overhauled soon, the internal insulation materials have good states, and the new converter transformer is not greatly different from the internal insulation materials after the overhaul is finished, at the moment, the weak link of the internal insulation cannot be effectively detected if the 80% test voltage is still adopted, but if the converter transformer fails after nearly 20 years of operation, the test voltage is set to be 80% after the overhaul is finished, so that the test voltage is intuitively reasonable because the residual life of the converter transformer insulation materials and the like is in the final stage, the test voltage value can fully ensure that the insulating material is not damaged by the test voltage and can smoothly pass a field handover test.
Therefore, the prior art cannot effectively determine the factory test withstand voltage value of the converter transformer after overhaul.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for determining the withstand voltage value of a factory test of a converter transformer after overhaul, which is used for solving the current situation that the test voltage value is selected without basis, effectively determining the relation between the test voltage value selection and the state of an insulating material in the converter transformer and fully guiding the development of the factory overhaul factory test of the converter transformer.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a method for determining a withstand voltage value of a factory test after overhaul of a converter transformer comprises the following steps:
step 1: sampling insulation paper with the highest lead temperature rise in each part of the overhauled converter transformer under rated current, wherein before sampling the insulation paper, deoiling of a transformer body and stripping of the insulation paper and auxiliary insulation on the surface of a transformer winding or the lead are required to be completed;
step 2: the sampling quality of each insulating paper is greater than the set weight, the insulating paper samples are divided into a plurality of parts according to the quality, the collected insulating paper samples are classified and marked, and the insulating paper samples are placed into a self-sealing bag for vacuumizing storage; during testing, measuring the viscosity-average polymerization degrees of a plurality of groups of cellulose electrical insulation materials on an insulation paper sample, eliminating a failure measurement group and abnormal measurement data, and averaging the obtained insulation paper polymerization degree test data;
and step 3: and determining the factory test withstand voltage value of the repaired converter transformer based on the relation between the polymerization degree of the insulating paper and the factory test voltage value after the overhaul.
In the method for determining the withstand voltage value in the factory test after the converter transformer is overhauled, the polymerization degree D of the insulating paperpThe relation with the factory test voltage value V after maintenance is as follows:
in the formula, VsdIs a standard factory test voltage value, and V is a factory test voltage value after maintenance.
In the method for determining the withstand voltage value of the factory test after the overhaul of the converter transformer, each part of the converter transformer further includes: the highest point of temperature rise of the low-voltage winding and the lead wire, the highest point of temperature rise of the medium-voltage winding and the lead wire, the highest point of temperature rise of the high-voltage winding and the lead wire and the highest point of temperature rise of the voltage regulating winding and the lead wire.
According to the method for determining the withstand voltage value of the factory test after the overhaul of the converter transformer, further, the polymerization degree of the insulating paper can be obtained through the following formula:
in the formula, Dp1Degree of polymerization of the insulating paper at time t, Dp0The polymerization degree of the insulation paper at the time of shipment, t is the running time, and k is a coefficient related to the temperature.
Compared with the prior art, the invention has the beneficial effects that: the method can accurately determine the factory test withstand voltage value of the converter transformer after overhaul as much as possible, can furthest test the overhaul quality of the converter transformer, ensures that the insulation of the converter transformer meets the operation and use requirements, avoids the irreversible damage of the overhigh test voltage value to the insulation inside the converter transformer which has been used for a long time, and can also avoid the situation that the overhigh test voltage value cannot fully and effectively detect the converter transformer which is just put into operation soon.
Drawings
FIG. 1 is a graph showing the degree of polymerization of an insulating paper as a function of time;
FIG. 2 is a graph showing the relationship between the test voltage and the degree of polymerization;
FIG. 3 is a flow chart of the measurement of viscosity-average degree of polymerization of the cellulose electrical insulation material;
fig. 4 is a flowchart of the method for determining the withstand voltage value in the factory test according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and detailed description.
Example (b):
when a converter transformer (or simply referred to as a converter transformer) newly shipped from a factory is subjected to an alternating-current external withstand voltage test, a valve-side direct-current withstand voltage test, a lightning impulse voltage test and an operation impulse voltage test, the test voltage is generally carried out according to the test voltage (hereinafter referred to as a "standard specified value") specified in GB1094.3 or both protocols, and the shipped test after the overhaul of the converter transformer which has been operated is not suitable for adopting the 100% standard specified value. Because the insulation strength of the insulation part and the insulation oil in the running converter transformer are reduced in different degrees, if the insulation strength is still checked by adopting a 100% standard specified value, the equipment insulation is easy to be irreversibly damaged.
The transformer inner body contains a large amount of insulating paper materials for insulating and isolating the inner coils and the coils from the ground, and is an important component for ensuring the performance of the transformer, wherein the insulation faults of the transformer account for more than 80 percent of the total faults, and most of the insulation faults are aging faults of the insulating paper. Cellulose is a major constituent of insulating paper, and is a long-chain polymer formed by arranging a plurality of glucose chains end to end, each glucose monomer represents a bond length, and the number of bond lengths is the Degree of Polymerization (DP). In the operation process of the transformer, the solid insulating material can be slowly degraded along with various ways such as hydrolysis, pyrolysis, oxidation and the like, so that the cracking phenomenon of a high-polymerized long-chain structure in the transformer occurs, and the expression forms of the cracking phenomenon are that the polymerization degree of insulating paper is reduced, furfural and oil dissolved gas appear in oil and the like. The furfural and dissolved gas mode can be developed in an electrified mode, but the aging degree of the insulating paper cannot be accurately judged under the influence of other fault factors, so that the degree of polymerization is closely related to the electrical characteristics of the insulating paper and is a characteristic parameter which reflects the most reliable aging degree of the insulating paper.
Aiming at the fact that the polymerization degree is the most reliable parameter for feeding back the insulation state in the converter transformer, a factory test is carried out to check the state of an insulation material, after a new converter transformer is put into operation, the polymerization degree of the insulation material is reduced along with the operation time along the curve shown in the figure 1, and a voltage value which can be used for checking the maintenance effect to the maximum degree and can ensure that the insulation material is not damaged can be found by selecting factory test values linearly corresponding to different polymerization degrees.
Referring to fig. 4, a method for determining a withstand voltage value of a factory test after a converter transformer is overhauled includes the following steps:
step 1: sampling insulation paper with the highest lead temperature rise in each part of the overhauled converter transformer under rated current, wherein before sampling the insulation paper, deoiling of a transformer body and stripping of the insulation paper and auxiliary insulation on the surface of a transformer winding or the lead are required to be completed.
Referring to fig. 2, step 2: the sampling mass of each insulating paper is greater than the set weight, the insulating paper sample is divided into a plurality of parts according to the mass, the collected insulating paper samples are classified and marked, and the samples are placed into a self-sealing bag for vacuumizing storage; during testing, a plurality of groups of cellulose electric insulating material viscosity-average polymerization degrees are measured on an insulating paper sample, a failure measurement group is removed, abnormal measurement data are removed, and an average value is taken for obtained insulating paper polymerization degree test data. In this embodiment: the sampling mass of each part of insulating paper is more than the set weight, and the sampling mass is divided into 5 parts and about 40g of each part; the collected insulating paper is marked by classification, put into a self-sealing bag for storage (dustproof and moistureproof), and put into a new self-sealing bag for vacuum storage after arriving at a laboratory. The polymerization degree test is carried out on the insulation sample according to the GB/T29305-2012 standard, and the flow is shown in a figure 3. And finally, taking the minimum value of the average value and the eliminated abnormal data for evaluation and calculation.
And step 3: and determining the factory test withstand voltage value of the repaired converter transformer based on the relation between the polymerization degree of the insulating paper and the factory test voltage value after the overhaul.
The method can determine the factory test withstand voltage value of the converter transformer after overhaul as accurately as possible, can check the overhaul quality of the converter transformer to the greatest extent, ensures that the converter transformer insulation meets the operation and use requirements, avoids the irreversible damage of the overhigh test voltage value to the internal insulation of the converter transformer which has been used for a long time, and can also avoid the situation that the overlow test voltage value cannot fully and effectively detect the converter transformer which has just been put into operation.
Further, in step 3, in the case of pure nature, the degree of polymerization of the cellulose paper is about 10000, the initial DP of the cellulose paper after preparation of the insulation pulp is about 1400, the DP after processing into new insulation is about 1200, and the DP after drying is about 1000, it is widely believed that when the DP of the transformer insulation paper is reduced to 500, the overall insulation life of the transformer is reached in the middle stage, and when the DP is reduced to about 200, the insulation paper is reachedEnd of life. Therefore, the switching test needs to be carried out after the converter transformer is transported to the site, the voltage value of the switching test is 80% of the factory test value of a new product, and the factory test value after the converter transformer is overhauled cannot be lower than the value, so that the service life of the insulating paper and the site switching requirement are comprehensively considered. We propose the following relationship: the polymerization degree of the insulating paper of the new converter transformer is about 1000 when the new converter transformer leaves the factory, and the factory test value is 100 percent of the standard specified value; when the polymerization degree of the insulating paper is 200, the factory test value after the maintenance of the converter transformer is 80 percent of the standard specified value; if the insulation polymerization value DP1 is between 1000 and 200, the converter transformer factory test value insulation paper polymerization degree DpThe relation with the factory test voltage value V after maintenance is as follows:
in the formula, VsdIs a standard factory test voltage value, and V is a factory test voltage value after maintenance.
Further, each part of the converter transformer comprises: the highest point of the temperature rise of the low-voltage winding and the lead wire, the highest point of the temperature rise of the medium-voltage winding and the lead wire, the highest point of the temperature rise of the high-voltage winding and the lead wire, and the highest point of the temperature rise of the voltage regulating winding and the lead wire are the points where the insulation paper of the converter transformer is most prone to aging, and the insulation aging condition of the converter transformer can be better known.
Further, besides the polymerization degree of the insulating paper is obtained through an experimental mode, the change of the polymerization degree of the insulating paper can also be represented and calculated and evaluated by adopting a mathematical model, and the thermal aging kinetic process of the insulating paper can be obtained through the following formula:
in the formula, Dp1Degree of polymerization of the insulating paper at time t, Dp0In order to obtain the degree of polymerization of the insulation paper at the time of shipment, t is the running time, and k is a temperature-dependent coefficient, it is shown that the aging rate is faster as the temperature is higher.
The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.
Claims (3)
1. A method for determining a withstand voltage value of a factory test of a converter transformer after overhaul is characterized by comprising the following steps:
step 1: sampling insulation paper with the highest lead temperature rise in each part of the overhauled converter transformer under rated current, wherein before sampling the insulation paper, deoiling of a transformer body and stripping of the insulation paper and auxiliary insulation on the surface of a transformer winding or the lead are required to be completed;
step 2: the sampling quality of each insulating paper is greater than the set weight, the insulating paper samples are divided into a plurality of parts according to the quality, the collected insulating paper samples are classified and marked, and the insulating paper samples are placed into a self-sealing bag for vacuumizing storage; during testing, measuring the viscosity-average polymerization degrees of a plurality of groups of cellulose electrical insulation materials on an insulation paper sample, eliminating a failure measurement group and abnormal measurement data, and averaging the obtained insulation paper polymerization degree test data;
and step 3: and determining the factory test withstand voltage value of the repaired converter transformer based on the relation between the polymerization degree of the insulating paper and the factory test withstand voltage value after the overhaul.
Degree of polymerization D of insulating paperpThe relation with the withstand voltage value V of the factory test after the overhaul is as follows:
in the formula, VsdThe voltage value is a standard factory test voltage value, and V is a factory test voltage value after maintenance.
2. The method for determining the withstand voltage value of the factory test of the converter transformer after the overhaul of the converter transformer as claimed in claim 1, wherein each part of the converter transformer comprises: the highest point of temperature rise of the low-voltage winding and the lead wire, the highest point of temperature rise of the medium-voltage winding and the lead wire, the highest point of temperature rise of the high-voltage winding and the lead wire and the highest point of temperature rise of the voltage regulating winding and the lead wire.
3. The method for determining the factory test withstand voltage value of the converter transformer after the overhaul according to claim 1, wherein the degree of polymerization of the insulating paper is also obtained by the following formula:
in the formula, DP1Degree of polymerization of the insulating paper at time t, DP0The polymerization degree of the insulation paper at the time of shipment, t is the running time, and k is a coefficient related to the temperature.
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