CN108398459B - Distribution oil variable winding material azimuth thermal resistance temperature curve identification method - Google Patents

Abstract

The invention relates to a nondestructive testing technology of distribution transformer equipment, in particular to a distribution oil transformer winding material azimuth thermal resistance temperature curve identification method, which comprises the steps of distributing points in groups, and sequentially distributing three groups of points on the top surface, the front surface and the left surface of an oil transformer tank body; completing the wiring of an oil-to-short circuit method and connecting the oil-to-short circuit method into a multi-channel temperature measuring device; carrying out a temperature rise test, and monitoring the temperature change condition of each point; when the temperature of each point tends to be stable, quickly disconnecting the power supply and connecting a direct resistance measuring device to measure the direct resistance value of the phase winding to be measured, and measuring once every certain time; and (3) making oil heating resistance temperature curves under the top surface, the front surface and the left surface based on an azimuth estimation method, discussing according to the situation, and obtaining the winding material after comprehensive judgment. The method can effectively detect the winding material and has the characteristics of economy, routine performance, no damage and accuracy.

Description

A method for identifying the thermal resistance and temperature curve of the distribution oil-varying winding material orientation

technical field

The invention belongs to the technical field of non-destructive testing of distribution transformer equipment, and in particular relates to a method for identifying a thermal resistance and temperature curve of a distribution oil-varying winding material orientation.

Background technique

There are a large number of distribution transformers, which play an important role in rural distribution networks and urban distribution networks, and are closely related to life. In recent years, with the rising copper price, the market price difference between copper and aluminum has gradually widened. A few transformer manufacturers have worked hard on winding materials in order to obtain greater profits. , which has a serious impact on the actual operation of distribution transformers.

Relevant literatures have also done a lot of research, such as thermoelectric method, temperature coefficient of resistance method, X-ray method, data statistics method, frequency response method, digital eddy current method, metal detection method and other nondestructive testing methods. As far as the most widely used temperature coefficient of resistance method is concerned, there are various methods for determining the definition formula of the temperature coefficient of resistance after various transformations, such as establishing a resistance temperature indexing table to compare the direct resistance value of the winding at different temperatures and the difference between them. The temperature coefficient of resistance is reversed and a certain margin space is taken, but the ideal effect has not been achieved in actual application.

For molded distribution transformers, the windings are encapsulated in the box or insulating material, which cannot be directly observed by the naked eye. The model identification on the nameplate is often different from the actual material, and the casing lead material and winding material are often different. If the winding material is aluminum wire or copper-clad aluminum wire, the extended joint can still be connected to the copper material by copper-aluminum welding method. It is difficult to find material differences from conventional items such as short circuit, no-load, insulation performance, etc. only by the existing technical testing methods. In order to prevent the phenomenon of "substituting aluminum for copper" from becoming "shoddy charging", it is particularly necessary to increase the intensity of investigation and punishment. Timely identification of distribution transformer winding materials is of great significance for improving the safety of distribution networks.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method that can accurately detect the winding material without damage.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a method for identifying the thermal resistance and temperature curve of the distribution oil variable winding material orientation, comprising the following steps:

Step 1. Arrange points in turn on the top, front and left sides of the oil change box;

Step 2. Complete the oil-to-change short-circuit method wiring and connect to the multi-channel temperature measurement device;

Step 3. Carry out the temperature rise test and monitor the temperature change at each point;

Step 4. When the temperature of each point tends to be stable, disconnect the power supply and connect it to the direct resistance measuring device, measure the direct resistance value of the phase winding to be measured, and measure it every certain time;

Step 5. Based on the azimuth estimation method, make the oil-to-change thermal resistance temperature curves on the top, front and left sides of the oil-change box, and determine the distribution oil-to-oil variable winding material according to the oil-to-heat resistance temperature curve.

The beneficial effects of the invention are: on the basis of using the short-circuit method to carry out the temperature rise test on the oil change in accordance with the national standard, the time required for the test is reduced, that is, it is not necessary to wait for the temperature to be completely stabilized, and it is only necessary to use the distribution point with a faster overall temperature rise change. that period of time. A new comprehensive estimation method for winding temperature is proposed. Only when two or more of the top, front and left sides meet the requirements, the judgment can be given. The comprehensiveness is strong and the misjudgment can be reduced. sex. The measurement time of the thermal direct resistance of the winding is reasonably extended (the national standard is 10min), on the one hand, the data samples are amplified, and on the other hand, the data utilization rate is improved when fitting the straight line.

Description of drawings

Fig. 1 is the wiring diagram of the short-circuit temperature rise test of oil transformer according to an embodiment of the present invention;

Fig. 2 is the wiring diagram of oil variable thermal resistance temperature acquisition according to an embodiment of the present invention;

3 is a flowchart of a method for identifying the thermal resistance temperature curve of the distribution oil variable winding material orientation according to an embodiment of the present invention;

Fig. 4 (a) is a top surface thermal resistance temperature fitting curve based on the azimuth estimation method according to an embodiment of the present invention;

FIG. 4(b) is a frontal thermal resistance temperature fitting curve based on the orientation estimation method according to an embodiment of the present invention;

FIG. 4( c ) is a left thermal resistance temperature fitting curve based on the azimuth estimation method according to an embodiment of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The present embodiment is realized through the following technical solutions, a method for identifying the thermal resistance temperature curve of the distribution oil-to-winding material orientation, which specifically includes the following steps:

S1. Arrange points in groups, and arrange three groups of points in turn on the top surface of the oil transformer box (with the connection point of the phase winding to be measured), the front side (with the upper point on the back) and the left side (with the middle point on the right side);

S2. Complete the oil change short-circuit method wiring and connect to the multi-channel temperature measurement device;

S3. Carry out the temperature rise test and monitor the temperature change at each point;

S4. When the temperature of each point tends to be stable, quickly disconnect the power supply and connect to the direct resistance measuring device to measure the direct resistance value of the phase winding to be measured, and measure it every certain time;

S5. Based on the azimuth estimation method, make the oil-changing thermal resistance temperature curves of the top surface, front and left side of the oil-changing box, discuss each situation, and obtain the winding material after comprehensive judgment.

During the specific implementation, as shown in Figure 1, the temperature rise test was carried out on the oil transformer model S(L)B11-M-200/10 by using the short-circuit method. Do not connect the copper bar too tightly, it is easy to disassemble and measure the direct resistance later). External 380V power frequency three-phase AC power supply, and step-up through the three-phase voltage regulator. The transformer three-phase voltage and current measurement device can monitor the voltage and current of each phase of the transformer measured during the temperature rise process, so as to avoid the situation of voltage asymmetry or excessive short-circuit current. The terminal "abc" means input voltage from the output of the voltage regulator to the tester, the terminal "ABC" means the input current from the output terminal of the tester to the high-voltage side of the transformer under test, and the terminal "U _A U _B U _C " means that the The output terminal of the tester inputs the voltage to the high-voltage side of the transformer under test. Except for the wiring where the three-phase air switch is located, this test requires 6 voltage wires and 3 current wires.

As shown in Figure 2, in the cooling process after the completion of the temperature rise test, it is necessary to measure and collect the temperature of each point and the thermal resistance of the low-voltage side b-phase winding. The temperature of each point was measured by attaching a thermocouple probe and insulating tape, and collected by a multi-channel temperature acquisition device with an accuracy of 0.05°C and a resolution of 0.01°C. The thermal resistance of the b-phase winding is measured by connecting to the DC resistance measuring device. The wiring method is four-wire system, the inner side is the voltage electrode, and the outer side is the current electrode. The degree is 0.2% and the resolution is 1μΩ. In order to make the wiring diagram clear at a glance, only the acquisition wiring of the top point (black dot) is drawn in the figure, and the acquisition wiring of the front point (regular triangular dot) and the left point (inverted triangular dot) should be added during the actual measurement. .

As shown in Figure 3, a method for identifying the thermal resistance and temperature curve of the distribution oil variable winding material, specifically includes the following steps:

1. Arrange points in groups, and arrange three sets of points in turn on the top surface of the oil transformer box (additional phase winding joint point to be measured), front side (additional upper point on the back) and left side (additional right middle point);

Specifically, the top surface point refers to the three points on the left, middle and right of the top surface of the box plus the winding joint points, the front point point refers to the upper, middle and lower points on the side of the box where the nameplate is attached plus the upper point on the back, and the left side point refers to the middle and bottom points on the left side of the box. Three points plus the middle point on the right, the exact attachment position of each point is shown in Figure 2.

2. Complete the oil change short-circuit method wiring and connect to the multi-channel temperature measurement device;

Specifically, pressurize on the high-voltage side, and use the copper bar for short circuit on the low-voltage side. External 380V power frequency three-phase AC power supply, and step up the voltage through the three-phase contact voltage regulator.

S3. Carry out the temperature rise test and monitor the temperature change at each point;

Specifically, first apply the maximum total loss on the high-voltage side, at this time, the test voltage U and test current I of the high-voltage side can be calculated by formula (1) and formula (2) respectively:

After the temperature rise at each point becomes stable, reduce the test current to the rated current, and stop heating when the temperature rise at each point becomes stable again. The purpose of the first stabilization is to speed up the heating rate of the winding, and the purpose of the second stabilization is to make the transformer to be tested work under the rated current condition, to avoid damage to it by high current, and to facilitate the measurement of thermal direct resistance in the later stage. .

4. When the temperature of each point tends to be stable, quickly disconnect the power supply and connect to the direct resistance measuring device to measure the direct resistance value of the phase winding to be measured, and measure it every certain time;

Specifically, in order to quickly connect to the direct resistance tester and avoid missing the best measurement time, it is necessary to master certain disassembly skills: first, put on heat insulating gloves to remove the short-circuit copper bars under high temperature, and each section of copper bars only needs to be removed. At one end, just ensure that the external connection of the three-phase winding is disconnected, and then connect to the direct resistance tester.

5. Based on the azimuth estimation method, make the oil-changing thermal resistance temperature curves of the top, front and left sides of the oil-changing box, discuss each situation, and obtain the winding material after comprehensive judgment.

Here is an example of the test of two oil transformers with the same shape, SB11-M-200/10 and SLB11-M-200/10, respectively. The thermal resistance-temperature curves of the two obtained from the test are shown in Figure 4. , the fitting functions are:

Top:

R _Cu = 0.01714T+3.152 (3)

R _Al = 0.01906T+3.012 (4)

front:

R _Cu = 0.02256T+2.958 (5)

R _Al = 0.02247T+2.930 (6)

left:

R _Cu = 0.02417T+2.90 (7)

R _Al = 0.02527T+2.896 (8)

In actual field application, for a distribution oil transformer with unknown winding material, three thermal resistance temperature curves can be obtained according to the azimuth estimation method test, and they are respectively substituted into the corresponding situations for discussion. When two or more situations meet the requirements, the Judgment is given: when the number of curves biased towards copper is ≥ 2, the winding material can be determined to be copper, otherwise it is aluminum.

It should be understood that the parts not described in detail in this specification belong to the prior art.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, those skilled in the art should understand that these are only examples, and various modifications or changes may be made to these embodiments without departing from the principles and principles of the present invention and substance. The scope of the present invention is limited only by the appended claims.

Claims (1)

1. A distribution oil becomes winding material position thermal resistance temperature curve identification method, characterized by, including the following steps:

step 1, sequentially grouping and distributing points on the top surface, the front surface and the left surface of an oil transformer tank body respectively;

the top surface distribution indicates that three points on the left, the middle and the right of the top surface of the box body are additionally provided with winding joint points, the front surface distribution indicates that the box body is adhered with a nameplate, three points on the upper side, the middle side and the lower side are additionally provided with upper points on the back surface, and the left surface distribution indicates that three points on the upper side, the middle side and the lower side are additionally provided with middle points on the;

step 2, completing the wiring of the oil-to-short circuit method and connecting the oil-to-short circuit method to a multi-channel temperature measuring device;

step 3, performing a temperature rise test, and monitoring the temperature change condition of each point;

step 4, when the temperature of each point tends to be stable, disconnecting the power supply and connecting the direct resistance measuring device, measuring the direct resistance value of the phase winding to be measured, and measuring once every certain time;

step 5, making oil heating resistance temperature curves of the top surface, the front surface and the left surface of the oil transformer tank body based on a position estimation method, and judging the material of the power distribution oil transformer winding according to the oil heating resistance temperature curves;

three thermal resistance temperature curves are obtained according to the test of the azimuth estimation method and are respectively substituted into corresponding conditions for discussion, and when two or more conditions meet the requirements, the judgment can be given: when the number of the curve strips which are changed towards the copper is more than or equal to 2, the winding material can be judged to be copper, otherwise, the winding material is aluminum.

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