CN108398459A - A kind of distribution oil change winding material orientation thermal resistance temperature curve recognition methods - Google Patents

Abstract

The invention relates to a non-destructive detection technology for distribution transformer equipment, in particular to a method for identifying azimuth thermal resistance temperature curves of distribution oil transformer winding materials, which includes grouping and distributing points, and sequentially laying three groups of points on the top, front and left sides of the oil transformer box; Complete the wiring of the oil transformer short circuit and connect to the multi-channel temperature measuring device; conduct a temperature rise test and monitor the temperature changes at each point; Measure the direct resistance of the phase winding, and measure it at regular intervals; based on the azimuth estimation method, draw the temperature curves of the thermal resistance of the oil transformer under the three conditions of the top surface, the front surface and the left surface, discuss according to the situation, and obtain the winding material after comprehensive judgment . The method can effectively detect the winding material, and has the characteristics of economical routine, non-destructive and accurate.

Description

A Method for Recognition of Azimuth Thermal Resistance Temperature Curve of Distribution Oil Transformer Winding Material

technical field

The invention belongs to the technical field of non-destructive detection of distribution transformer equipment, and in particular relates to a method for identifying azimuth thermal resistance temperature curves of winding materials of distribution oil transformers.

Background technique

There are a large number of distribution transformers, which play a pivotal role in the rural distribution network and urban distribution network, and are closely related to life. In recent years, with the rising price of copper, the difference between the market price of copper and aluminum has gradually widened. In order to obtain greater profits, a few transformer manufacturers have worked hard on winding materials. There is a bad phenomenon of "substituting aluminum for copper" in the market. , which has seriously affected the actual operation of distribution transformers.

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

For formed distribution transformers, the windings are encapsulated in boxes or insulating materials and cannot be directly observed by the naked eye. The model identification on the nameplate is often different from the actual material, and the bushing lead-out material is often different from the winding material. If the winding material is aluminum wire or copper-clad aluminum wire, the extended joints can still be connected to the copper material by copper-aluminum welding. It is difficult to find material differences from conventional items such as short circuit, no-load, and insulation performance only by existing technical detection methods. In order to prevent the phenomenon of "replacing copper with aluminum" from further evolving into "substituting inferior products for better ones", 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.

Contents of the invention

The purpose of the present invention is to provide a method for non-destructive and accurate detection of winding material.

In order to achieve the above purpose, the technical solution adopted by the present invention is: a method for identifying the azimuth thermal resistance temperature curve of the winding material of the power distribution oil transformer, comprising the following steps:

Step 1. Distribute points in groups on the top, front and left sides of the oil transformer box respectively;

Step 2. Complete the oil transformer short-circuit wiring and connect to the multi-channel temperature measuring device;

Step 3. Conduct a temperature rise test and monitor the temperature changes at each point;

Step 4. When the temperature of each point tends to be stable, disconnect the power supply and connect the direct resistance measuring device to measure the direct resistance value of the phase winding to be tested, and measure it at regular intervals;

Step 5. Based on the azimuth estimation method, draw the oil transformer thermal resistance temperature curves on the top, front and left sides of the oil transformer box, and determine the distribution oil transformer winding material according to the oil transformer thermal resistance temperature curves.

The beneficial effects of the present invention are: on the basis of following the national standard and using the short-circuit method to carry out the temperature rise test on the oil transformer, the time required for the test is reduced, that is, it is not necessary to wait for the temperature to be completely stable, and only need to use the temperature rise of the distribution points to change rapidly. that period of time. A new non-all-round estimation method for winding temperature is proposed. Only when two or more of the top, front and left sides meet the requirements can the judgment be given. It is comprehensive and can reduce misjudgments. sex. The measurement time of the thermal direct resistance of the winding is reasonably extended (10 minutes according to the national standard), on the one hand, the data sample is enlarged, 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 an embodiment of the present invention for the short-circuit temperature rise test of the oil transformer;

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

Fig. 3 is a flowchart of a method for identifying the azimuth thermal resistance temperature curve of the winding material of the power distribution oil transformer according to an embodiment of the present invention;

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

Fig. 4 (b) is the front thermal resistance temperature fitting curve based on the azimuth estimation method of an embodiment of the present invention;

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

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

This embodiment is realized through the following technical solution, a method for identifying the azimuth thermal resistance temperature curve of the winding material of the power distribution oil transformer, which specifically includes the following steps:

S1. Group distribution points, three groups of points are sequentially arranged on the top surface of the oil transformer box (additional phase winding joint point to be tested), front side (additional back upper point) and left side (additional right middle point);

S2. Complete the wiring of the oil transformer short-circuit method and connect to the multi-channel temperature measuring device;

S3. Carry out a temperature rise test, and monitor the temperature changes at each point;

S4. When the temperature of each point tends to be stable, quickly disconnect the power supply and connect the direct resistance measuring device to measure the direct resistance value of the phase winding to be tested, and measure it at regular intervals;

S5. Based on the azimuth estimation method, the oil transformer thermal resistance temperature curves for the top, front and left sides of the oil transformer box are drawn, discussed by situation, and the winding material is obtained after comprehensive judgment.

In the specific implementation, as shown in Figure 1, the temperature rise test of the oil transformer of the model S(L)B11-M-200/10 was carried out by using the short circuit method. Do not connect the copper bars too tightly, it is easy to disassemble and measure the DC resistance in the later stage). The external 380V power frequency three-phase AC power supply is gradually boosted by the three-phase voltage regulating device. The transformer three-phase voltage and current measuring device can monitor the voltage and current of each phase of the transformer measured during the temperature rise process to avoid voltage asymmetry or excessive short-circuit current. Binding column "abc" indicates that the voltage is input from _the output terminal of the voltage regulator to _the tester; terminal "ABC" indicates that the current is input from the output terminal of the tester to the _high voltage side of the transformer under test; The output terminal of the tester inputs the voltage to the high voltage side of the transformer under test. Excluding the wiring where the three-phase air switch is located, this test requires 6 voltage lines and 3 current lines.

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

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

1. Distribute points in groups, and place three groups of points sequentially on the top surface of the oil transformer box (additional phase winding joint points to be tested), front side (additional back upper point) and left side (additional right middle point);

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

2. Complete the wiring of the oil transformer short-circuit method and connect to the multi-channel temperature measuring device;

Specifically, pressurize the high-voltage side, and short-circuit the low-voltage side with a copper bar. The copper bar should not be connected too tightly, so that it is easy to disassemble and measure the DC resistance later. The external 380V power frequency three-phase AC power supply is gradually boosted by a three-phase contact voltage regulator.

S3. Carry out a temperature rise test, and monitor the temperature changes at each point;

Specifically, the maximum total loss is first applied on the high-voltage side. At this time, the test voltage U and test current I on the high-voltage side can be calculated by formula (1) and formula (2):

After the temperature rise of each point tends to be stable, then reduce the test current to the rated current, and stop heating after the temperature rise of each point tends to be 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 under test work under rated current conditions, avoid damage to it caused by high current, and 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 the direct resistance measuring device to measure the direct resistance value of the phase winding to be tested, and measure it at regular intervals;

Specifically, in order to quickly connect to the direct resistance tester and avoid missing the best measurement time, certain disassembly and assembly skills need to be mastered: first, wear heat-insulating gloves to remove the short-circuit copper bar under high temperature, and each section of copper bar 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, the oil transformer thermal resistance temperature curves for the top, front and left sides of the oil transformer box are drawn, discussed in each case, and the winding material is obtained after comprehensive judgment.

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

top surface:

R _Cu ＝0.01714T+3.152 (3)

_RAl ＝0.01906T+3.012 (4)

front:

R _Cu ＝0.02256T+2.958 (5)

_RAl ＝0.02247T+2.930 (6)

left:

R _Cu ＝0.02417T+2.90 (7)

_RAl ＝0.02527T+2.896 (8)

In actual field application, for a distribution oil substation whose winding material is unknown, three thermal resistance temperature curves can be obtained according to the test of the azimuth estimation method, and they can be substituted into the corresponding cases for discussion. When two or more cases meet the requirements, it can be Judgment is given: when the number of curves biased towards copper is ≥ 2, it can be determined that the winding material is 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 of ordinary skill in the art should understand that these are only examples, and various variations or modifications can be made to these embodiments without departing from the principles and principles of the present invention. substance. The scope of the invention is limited only by the appended claims.

Claims (1)

1. A method for identifying azimuth thermal resistance temperature curves of distribution oil transformer winding materials, characterized in that it comprises the following steps: Step 1. Distribute points in groups on the top, front and left sides of the oil transformer box respectively; Step 2. Complete the oil transformer short-circuit wiring and connect to the multi-channel temperature measuring device; Step 3. Conduct a temperature rise test and monitor the temperature changes at each point; Step 4. When the temperature of each point tends to be stable, disconnect the power supply and connect the direct resistance measuring device to measure the direct resistance value of the phase winding to be tested, and measure it at regular intervals; Step 5. Based on the azimuth estimation method, draw the oil transformer thermal resistance temperature curves on the top, front and left sides of the oil transformer box, and determine the distribution oil transformer winding material according to the oil transformer thermal resistance temperature curves.