A test electrode and method for measuring the electric field of oil-paper insulation space under temperature gradient

Abstract

The invention discloses a test electrode and a test method suitable for measuring the electric field of an oil-paper insulation space under a temperature gradient, comprising a test electrode pipeline joint (1), an insulating sheath (2), a shielding ring (3), an upper electrode (4), a guide rod sheath (5), a low-temperature circulating oil circuit (6), a high-voltage guide rod (7), an insulating pad (8), a ceramic heating plate (9), a heating plate lead wire (11), an aviation plug (12), a sealing flange (13), a lower electrode (14), a circulating oil pump (15), a low-temperature heat exchanger (16), a limit screw (17), and a low-voltage guide rod (18); the test electrode is placed in a test cavity (10) for testing. When performing actual measurement, by adjusting the real-time temperature of the upper and lower electrodes and the electrode spacing, a temperature difference with a gradient that can be adjusted over a wide range is formed between them, thereby realizing the electric field measurement of the oil-paper insulation space under the temperature gradient.

Description

Technical Field

[0001] The invention belongs to the field of electrical measurement, and in particular relates to a test electrode and a method for measuring the electric field of oil-paper insulation space under temperature gradient. Background Art

[0002] As a key equipment in the high-voltage direct current transmission system, the performance of the converter transformer can have an unignorable impact on the safe and stable operation of the power system. As the main insulation structure of the converter transformer, the insulation performance of the oil-paper insulation plays a vital role in the operation of the converter transformer. As one of the most critical characteristics of its insulation performance, the spatial and temporal distribution characteristics of the electric field of the oil-paper insulation have become a research hotspot for scholars and related practitioners at home and abroad in recent years. Under actual working conditions, stray losses and Joule heat will be generated when the converter transformer is running under load, which will lead to an increase in the oil temperature inside the transformer. The imbalance between the increase in oil temperature and the heat dissipation process will cause the temperature of the oil-paper insulation space to be distributed in a gradient. Therefore, the study of the distribution law of the electric field in the oil-paper insulation space under the temperature gradient is of great significance to insulation design, verification and fault diagnosis.

[0003] At present, test electrodes under temperature gradient are mostly used for measuring the spatial charge of small-sized insulating paper at the micron or sub-millimeter level. There is a lack of test electrodes for directly measuring the spatial electric field of oil-paper composite insulation structure under temperature gradient. In addition, most existing electrodes are small electrodes that cannot form a uniform electric field and temperature gradient field in a practical sense, and they are quite different from the large-sized oil-paper insulation structure of the actual converter transformer. For example, the temperature gradient test electrode given in the utility model patent "A spatial charge measurement device suitable for wide temperature gradient" (application number 201620227225.5) uses an aluminum rod as the upper electrode, and the contact area between the upper and lower electrodes is very small, so there is no uniform electric field between the upper and lower electrodes. Moreover, the thickness of the sample to be tested is only at the sub-millimeter level. After removing the influence of the edge effect, the area where the temperature gradient is actually formed is extremely small. Therefore, it is urgent to develop a test electrode and measurement method that can directly measure the spatiotemporal distribution characteristics of the spatial electric field under large gradient temperature for oil-paper composite insulation structure.

[0004] Purpose of the Invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and to provide a test electrode for measuring the electric field in the oil-paper insulation space under a temperature gradient, which can form a good large-range temperature gradient, has excellent thermal conductivity, and a large temperature gradient region, and is suitable for direct measurement of the electric field in the oil-paper insulation space under a temperature gradient. Summary of the invention

[0006] According to one aspect of the present invention, there is provided a test electrode for measuring the electric field of oil-paper insulation space under temperature gradient, comprising a pipeline joint, an insulating sheath, a shielding ring, an upper electrode, a guide rod sheath, a low-temperature circulating oil circuit, a high-voltage guide rod, an insulating pad, a ceramic heating plate, a heating plate lead wire, an aviation plug, a sealing flange, a lower electrode, a circulating oil pump, a low-temperature heat exchanger, a limit top screw, and a low-voltage guide rod; the test electrode is placed in a test cavity for electric field measurement;

[0007] The pipe joint serves as a connection device between the low-temperature circulating oil circuit and the upper electrode to prevent the cooling medium oil from leaking out from the connection;

[0008] The insulating sheath wraps the guide rod sheath and the bottom of the high-voltage guide rod to prevent discharge from occurring there when voltage is applied;

[0009] The shielding ring is located at the center above the upper electrode and surrounds the pipe joint, and the top end is chamfered to prevent the generation of tip corona discharge;

[0010] The upper electrode is hollow inside, and the inside of the electrode is filled with cooling medium oil. Heat is exchanged through the low-temperature circulating oil circuit to achieve the function of continuous low temperature. The upper electrode can be wrapped with insulating paper or fixed with insulating paperboard by coating or gluing, and form an oil-paper composite insulation structure with the transformer oil inside the cavity; the upper end is connected to the high-voltage guide rod to introduce high voltage and cooperate with the lower electrode to achieve the establishment of an electric field in the space between the electrodes;

[0011] The guide rod sheath is a metal sheath, the lower end of which is welded to the upper electrode, and the middle part is connected to the high-voltage guide rod by threads, so as to achieve the connection between the high-voltage guide rod and the upper electrode;

[0012] The two ends of the low-temperature oil circulation loop are connected to the upper electrode through the pipe joints, and the circulating oil pump and the low-temperature heat exchanger are used to realize the circulation and cooling treatment of the cooling medium oil inside the upper electrode;

[0013] The high-voltage electrode guide rod is connected to the upper electrode to achieve the introduction of high voltage;

[0014] The insulating pad is placed at the bottom of the test cavity and is an adjustable height pad that supports and fixes the ceramic heating plate;

[0015] The ceramic heating plate is located at the bottom of the lower electrode to heat the lower electrode;

[0016] The test cavity is used as a receiving device for the test electrode, and is filled with insulating dielectric oil to perform a spatial electric field measurement test in oil;

[0017] The lead wires of the heating plate, including the temperature control wire and the heating wire, are introduced into the test cavity through the aviation plug to realize the temperature control of the ceramic heating plate;

[0018] The aviation plug is located at the bottom of the test cavity to enable the access of the lead wire of the heating plate;

[0019] The sealing flange performs sealing treatment on the aviation plug and the low-voltage guide rod to prevent the insulating medium oil inside the test cavity from leaking through the bottom;

[0020] The lower electrode is connected to the low-voltage guide rod and cooperates with the ceramic heating plate as a high-temperature electrode. The lower electrode can be wrapped with insulating paper or fixed with insulating paperboard by coating or gluing to form an oil-paper composite insulation structure with the transformer oil inside the cavity;

[0021] The circulating oil pump is located in the low-temperature circulating pipeline to drive the circulation of the cooling medium oil;

[0022] The low-temperature heat exchanger is located in the low-temperature circulation pipeline to achieve temperature reduction and heat exchange treatment of the cooling medium oil;

[0023] The limit screw is located at the top of the test chamber to fix the high-voltage guide rod and the low-temperature circulation oil circuit to the upper electrode connecting pipe, ensuring the level of the upper electrode; the limit screw is used to control the distance between the upper electrode and the lower electrode to meet the requirements of electric field measurement;

[0024] The low-voltage guide rod is connected to the lower electrode and is fixed and sealed by the sealing flange to ensure the sealing of the test cavity; the low-voltage guide rod extends to the outside of the test cavity for inputting AC modulation signals.

[0025] According to another aspect of the present invention, there is provided a method for measuring the space electric field of oil-paper insulation using the above-mentioned test electrode, comprising the following steps:

[0026] Step 1: According to the test requirements, wrap the insulating paper or fix / stick the insulating paperboard so that it is attached to the upper electrode (4) or the lower electrode (14), or is placed between the upper and lower electrodes to form an oil-paper composite insulating structure, fix the lower electrode, and adjust the height of the insulating spacer so that the ceramic heating plate is in close contact with the bottom surface of the lower electrode;

[0027] Step 2: Adjust the limit screw to control the distance between the upper electrode and the lower electrode to meet the measurement requirements;

[0028] Step 3, injecting cooling medium oil into the low-temperature heat exchanger; controlling the ceramic heating plate through the heating plate lead wire to increase the temperature of the lower electrode to the temperature required for the test;

[0029] Step 4, starting the circulating oil pump to drive the cooling medium oil to circulate in the low-temperature circulating oil circuit and the upper electrode, and cooling the upper electrode through the low-temperature heat exchanger to maintain a low temperature;

[0030] Step 5: Under the combined action of the low-temperature circulating oil circuit and the ceramic heating plate, a large-range temperature gradient field is formed between the upper electrode and the lower electrode, and the temperature gradient is adjustable; a DC high voltage is applied to the high-voltage guide rod, and an AC modulated voltage is applied to the low-voltage guide rod, and then non-contact electric field measurement technology such as the Kerr electro-optical effect can be used to measure the oil-paper insulation space electric field under the temperature gradient. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a front view of the overall structure of the test electrode for measuring the oil-paper insulation space electric field under temperature gradient according to the present invention.

[0032] Figure 2 The present invention is a front view of the upper electrode and cooling circuit of the test electrode for measuring the oil-paper insulation space electric field under temperature gradient.

[0033] Figure 3 It is a top view of the upper electrode of the test electrode for measuring the oil-paper insulation space electric field under temperature gradient according to the present invention.

[0034] Reference numerals:

[0035] 1- pipe joint, 2- insulating sheath, 3- shielding ring, 4- upper electrode, 5- guide rod sheath, 6- low-temperature circulation oil circuit, 7- high-pressure guide rod, 8- insulating pad, 9- ceramic heating plate, 10- test chamber, 11- heating plate lead wire, 12- aviation plug, 13- sealing flange, 14- lower electrode, 15- circulating oil pump, 16- low-temperature heat exchanger, 17- limit top screw, 18- low-pressure guide rod. Specific implementation plan

[0036] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. The figure numerals listed in the accompanying drawings run through the entire text of this specification and represent the same components.

[0037] Figure 1 This is a front view of the overall structure of the test electrode for measuring the oil-paper insulation space electric field under temperature gradient according to the present invention. Figure 2 This is a front view of the upper electrode and cooling circuit of the test electrode for measuring the oil-paper insulation space electric field under temperature gradient according to the present invention. Figure 3 This is a top view of the upper electrode of the test electrode for measuring the space electric field of oil-paper insulation under temperature gradient according to the present invention. Figure 1 , Figure 2 and Figure 3The specific implementation modes of the present invention are further described in detail.

[0038] The present invention provides a test electrode for measuring the space electric field of oil-paper insulation under temperature gradient, comprising an upper electrode and a lower electrode. Figure 1 , Figure 2 and Figure 3 As shown, the test electrode comprises a pipeline joint (1), an insulating sheath (2), a shielding ring (3), an upper electrode (4), a guide rod sheath (5), a low-temperature circulating oil circuit (6), a high-voltage guide rod (7), an insulating pad (8), a ceramic heating plate (9), a heating plate lead wire (11), an aviation plug (12), a sealing flange (13), a lower electrode (14), a circulating oil pump (15), a low-temperature heat exchanger (16), a limit screw (17), and a low-voltage guide rod (18); the test electrode is placed in a test cavity (10) to perform electric field measurement.

[0039] The present invention also provides a method for measuring the oil-paper insulation space electric field using the above test electrode, comprising the following steps:

[0040] Step 1: According to the test requirements, wrap the insulating paper or fix / stick the insulating paperboard so that it is attached to the upper electrode (4) or the lower electrode (14), or is located between the upper and lower electrodes to form an oil-paper composite insulating structure, fix the lower electrode (14), and adjust the height of the insulating spacer (8) so that the ceramic heating plate (9) is in close contact with the bottom surface of the lower electrode (14);

[0041] Step 2: adjusting the limit screw (17) to control the distance between the upper electrode (4) and the lower electrode (14) to meet the measurement requirements;

[0042] Step 3, injecting cooling medium oil into the low-temperature heat exchanger (16); controlling the ceramic heating plate (9) through the heating plate lead wire (11) to increase the temperature of the lower electrode (14) to the temperature required for the test;

[0043] Step 4, starting the circulating oil pump (15) to drive the cooling medium oil to circulate in the low-temperature circulating oil circuit (6) and the upper electrode (4), and cooling the upper electrode (4) through the low-temperature heat exchanger (16) to maintain a low temperature;

[0044] Step 5: Under the combined action of the low-temperature circulating oil circuit (6) and the ceramic heating plate (14), a temperature gradient field is formed between the upper electrode (4) and the lower electrode (14); a DC high voltage is applied to the high-voltage guide rod (7), and an AC modulated voltage is applied to the low-voltage guide rod (18), thereby utilizing non-contact electric field measurement techniques such as the Kerr electro-optical effect to perform oil-paper insulation space electric field measurement under temperature gradient.

Claims

1. A test electrode for measuring the space electric field of oil-paper insulation under temperature gradient, characterized in that: It comprises a pipe joint (1), an insulating sheath (2), a shielding ring (3), an upper electrode (4), a guide rod sheath (5), a low-temperature circulating oil circuit (6), a high-voltage guide rod (7), an insulating pad (8), a ceramic heating plate (9), a heating plate lead wire (11), an aviation plug (12), a sealing flange (13), a lower electrode (14), a circulating oil pump (15), a low-temperature heat exchanger (16), a limit screw (17), and a low-voltage guide rod (18); the test electrode is placed in a test cavity (10) to perform electric field measurement; The pipe joint (1) serves as a connection device between the low-temperature circulating oil circuit (6) and the upper electrode (4) to prevent the cooling medium oil from leaking out from the connection; The insulating sheath (2) wraps around the guide rod sheath (5) and the bottom of the high-voltage guide rod (7) to prevent discharge from occurring there when voltage is applied; The shielding ring (3) is located at the center above the upper electrode and surrounds the pipe joint (1), and the top end is chamfered to prevent the generation of corona discharge at the tip; The upper electrode (4) is hollow inside and filled with cooling medium oil. Heat is exchanged through the low-temperature circulating oil circuit (6) to achieve a continuous low-temperature function. The upper electrode (4) can be wrapped with insulating paper or fixed with insulating paperboard by means of coating or gluing to form an oil-paper composite insulation structure with the transformer oil inside the cavity. The upper end is connected to the high-voltage guide rod (7) to introduce high voltage and cooperate with the lower electrode (14) to establish an electric field in the space between the electrodes. The guide rod sheath (5) is a metal sheath, the lower end of which is welded to the upper electrode (4), and the middle part of which is connected to the high-voltage guide rod (7) by means of a thread, thereby achieving communication between the high-voltage guide rod (7) and the upper electrode (4); The two ends of the low-temperature circulating oil circuit (6) are connected to the upper electrode (4) via the pipe joints (1), and the circulating oil pump (15) and the low-temperature heat exchanger (16) are used to implement circulating cooling treatment of the cooling medium oil inside the upper electrode (4); The high-voltage guide rod (7) is connected to the upper electrode (4) to achieve the introduction of high voltage; The insulating pad (8) is placed at the bottom of the test cavity (10) and is a pad with adjustable height, which plays a supporting and fixing role for the ceramic heating plate (9); The ceramic heating plate (9) is located at the bottom of the lower electrode (14) to achieve heating of the lower electrode (14); The test cavity (10) serves as a receiving device for the test electrode and is filled with insulating dielectric oil to perform a spatial electric field measurement test in oil; The heating plate lead wire (11), comprising a temperature control wire and a heating wire, is introduced into the test cavity (10) through the aviation plug (12) to achieve temperature control of the ceramic heating plate; The aviation plug (12) is located at the bottom of the test cavity (10) to enable the connection of the lead wire (11) of the heating plate; The sealing flange (13) performs sealing treatment on the aviation plug (12) and the low-voltage guide rod (18) to prevent the insulating medium oil inside the test cavity (10) from leaking out through the bottom; The lower electrode (14) is connected to the low-voltage guide rod (18) and cooperates with the ceramic heating plate (9) to serve as a high-temperature electrode; the lower electrode (14) can be coated with insulating paper or fixed with insulating paperboard by means of coating or gluing, and form an oil-paper composite insulation structure with the transformer oil inside the cavity; The circulating oil pump (15) is located in the low-temperature circulating oil circuit (6) and drives the circulation of the cooling medium oil; The low-temperature heat exchanger (16) is located in the low-temperature circulating oil circuit (6) to achieve temperature reduction and heat exchange processing of the cooling medium oil; The limit screw (17) is located at the top of the test chamber (10) to fix the high-voltage guide rod (7) and the low-temperature circulation oil circuit (6) to the connecting pipe of the upper electrode (4), thereby ensuring the level of the upper electrode (4); the limit screw (17) is used to control the distance between the upper electrode (4) and the lower electrode (14) to meet the requirements of electric field measurement; The low-voltage guide rod (18) is connected to the lower electrode (14) and is fixed and sealed by the sealing flange (13) to ensure the sealing of the test chamber (10); the low-voltage guide rod (18) extends to the outside of the test chamber and is used for inputting AC modulation signals.

2. A method for measuring the electric field of oil-paper insulation space using the test electrode as claimed in claim 1, characterized in that: The following steps are involved: Step 1: According to the test requirements, wrap the insulating paper or fix / stick the insulating paperboard so that it is attached to the upper electrode (4) or the lower electrode (14), or is placed between the upper and lower electrodes to form an oil-paper composite insulating structure, fix the lower electrode (14), and adjust the height of the insulating spacer (8) so that the ceramic heating plate (9) is in close contact with the bottom surface of the lower electrode (14); Step 2: adjusting the limit screw (17) to control the distance between the upper electrode (4) and the lower electrode (14) to meet the measurement requirements; Step 3, injecting cooling medium oil into the low-temperature heat exchanger (16); controlling the ceramic heating plate (9) through the heating plate lead wire (11) to increase the temperature of the lower electrode (14) to a temperature required for the test; Step 4, starting the circulating oil pump (15) to drive the cooling medium oil to circulate in the low-temperature circulating oil circuit (6) and the upper electrode (4), and cooling the upper electrode (4) through the low-temperature heat exchanger (16) to maintain a low temperature; Step 5: Under the combined action of the low-temperature circulating oil circuit (6) and the ceramic heating plate (14), a temperature gradient field is formed between the upper electrode (4) and the lower electrode (14); a DC high voltage is applied to the high-voltage guide rod (7), and an AC modulated voltage is applied to the low-voltage guide rod (18), thereby using the Kerr electro-optical effect non-contact electric field measurement technology to perform oil-paper insulation space electric field measurement under temperature gradient.

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