GB 1094.3-1985 Power transformer Part 3 Insulation level and insulation test
Some standard content:
National Standard of the People's Republic of China
Power Transformers
Part 3: Insulation levels and dielectric tests
Power transformers
Part 3: Insulation levels and dielectric testsUDC621.314.222.6| | tt | 1 Terms
See Chapter 3 of GB1094.1-85 "Power Transformers Part 1 General Provisions". 2 Overview
The insulation requirements and corresponding insulation tests of power transformers are specified according to the specified windings and their terminals. It should comply with the relevant provisions of national standards GB311.1~6-83. For oil-immersed transformers, these requirements apply only to the internal insulation. When additional requirements or tests are required for external insulation, they should be agreed upon by the manufacturer and the user department.
Note: Under appropriate circumstances, type testing can be carried out on a suitable structural model. When the wiring used by the user department on the transformer may reduce the original insulation distance of the transformer, it must be specially noted on the inquiry order and technical requirements form.
When the oil-immersed transformer needs to operate at an altitude exceeding 1000m, the insulation distance should be designed according to the requirements, and a bushing with a higher insulation level than the specified insulation level in the transformer can also be selected. Bushings and tap-changers must individually undergo type and factory tests to verify their internal and external insulation to earth. Although the bushings and tap-changers used are designed, manufactured and tested in accordance with relevant standards, insulation tests still need to be carried out on the fully assembled transformer to check whether the use and installation of these components are correct. Usually, the insulation test is carried out in the workshop of the manufacturer, with the transformer placed at approximately the specified test ambient temperature. During the test, the transformer shall be fully assembled as during operation, but for oil-immersed transformers, external cooling accessories and other accessories irrelevant to the test may not be assembled.
If the transformer test is affected by bushing failure, it is allowed to temporarily replace the faulty bushing with another bushing, and the transformer shall be tested immediately until the test is completed. When the transformer is specified to use this kind of bushing, and the partial discharge measurement makes the test difficult due to the high partial discharge amount in the bushing medium, the partial discharge qualified bushing can be used instead during the test ( See Appendix A). Transformers connected by cable boxes or directly connected to SF6 (sulfur hexafluoride) fully enclosed metal-enclosed electrical devices should be designed such that temporary bushings can be used for temporary connection when necessary to facilitate insulation testing. If under special circumstances, the manufacturer needs to use nonlinear components or arresters inside or outside the transformer to limit the transmitted transient overvoltage, the user should be alerted.
3 Maximum voltage and insulation level of equipment
The maximum voltage Um value of the equipment should be indicated for each winding of the transformer (see GB1094.1 Section 3.9.1). Depending on the size of Um, the insulation coordination rules of the transformer during transient overvoltage are different. When there is a conflict between the test rules for different windings in a transformer, the test rules suitable for the winding with the highest Um value shall apply. Approved by the National Bureau of Standards on November 22, 1985
Implemented on 1986-07-01
GB1094.3-85
Other rules applicable to special circumstances are in Chapter 4 of this standard given. The standard values ??of Um are listed in Table 2. The Um value for the transformer winding can be a value equal to or slightly greater than the rated voltage of the winding. Note: ① For single-phase transformers that are intended to be connected in a star connection to form a three-phase transformer group, it is indicated by the phase-to-ground rated voltage, such as 500/3kV. The phase-to-phase voltage value determines the selection of Um, here Um=550kV. ② For transformers with tap windings, for some reasons, the tap voltage of the selected winding may be slightly higher than the standard value of U, but the maximum voltage of the system connected to the winding remains within this standard value. Since the insulation requirements must match the actual system conditions, this standard value should be used as the Um value of the transformer instead of selecting the nearest larger value. The rated withstand voltage that constitutes the insulation level of the winding is verified by a set of insulation tests (see Chapter 5 of this standard) that changes with the Um value.
If the Um value and insulation level on each winding of the transformer is different from the provisions of GB311.1, it should be mentioned when making an inquiry or signing a contract. If the windings of the transformer are graded insulated and Um > 300kV, the test should be carried out according to "Method 1" or "Method 2" (see Table 1, Chapter 5 of this standard), and further information on the induction withstand voltage test (see Explanatory information on which method is used in Article 11.4 of this standard).
The rated withstand voltage values ??of all windings should be given on the nameplate. The abbreviation principle of the logo is as shown in the following examples. Note: The meanings of the abbreviations used are as follows:
LI - lightning impulse withstand voltage
SI - operating impulse withstand voltage:
AC - power frequency withstand voltage.
Example 1: A transformer with two windings. The winding Um values ??are 40.5kV and 11.5kV respectively. Both windings are fully insulated. The insulation level is expressed as follows:
Insulation level: The data of different windings in the LI200AC85/LI75AC35 box are separated by slashes, and the impact level is written in front. Example 2: Taiwan transformer has the following windings: high-voltage winding Um=252kV, graded insulation, star connection, neutral point not directly grounded, another winding Um=126kV, star connection, graded insulation; third winding Um= 11.5kV, delta connection. The insulation level is expressed as follows:
Insulation level: LI850AC360-LI400AC200/LI480AC200-LI250AC95/LI75AC35
For graded insulated windings in the box, the data at the line end is written in front, and the neutral point is written after the connection number. The data. Example 3: For an autotransformer, determine the specifications Um=363kV and 126kV according to method 2 (see Article 5.4 of this standard), and its neutral point is directly connected to the ground. The third winding Um=40.5kV. The insulation level is expressed as follows: Insulation level: SI950LI1175-AC85/
LI480-AC85/LI200AC85
In this case, the specification of method 2 also lacks the test of 126kV winding. For the wire of this winding The terminal does not need to specify the frequency withstand voltage separately. The induction withstand voltage test specified in Article 11.4 of this standard is applicable to two windings connected by auto-coupling. 4. Regulations applicable to some special types of transformers. In a transformer, when fully insulated windings with different Um values ??are connected together inside the transformer (usually an autotransformer), the external construction frequency withstand test voltage shall be as follows: The winding with the highest U value is determined. When the high-voltage winding of the transformer has Um>300kV, the lightning full-wave impact test is a factory test for all windings. For transformers with Um=252kV, see Note 1 of Table 1 of this standard. GB1094.3-85
For one or more graded insulated windings of a transformer, the Um value is lower because the voltage of the induction withstand test and the operating impulse test (if adopted) are determined based on the winding with the highest U value. The winding may not be able to withstand its corresponding test voltage, but this difference is generally acceptable. If the turns ratio between windings is changed by tapping, appropriate tapping should be used to make the test voltage value on the winding with a lower Um value as close as possible to its test voltage value. When operating a shock test, the voltages developed across different windings are roughly proportional to their turns ratios. If the rated impulse withstand voltages of several windings are determined, the relevant problems should be solved according to the above method. A tapped winding with a low Um value and an unspecified operating impulse withstand voltage is preferably connected in the main tap position when performing operating impulse tests. Although the rated voltage of the series coils of booster transformers, phase-shifting transformers, etc. is only a small part of the system voltage, its Um value is still a value equivalent to the system voltage. It is difficult to test this type of transformer strictly in accordance with these regulations. Therefore, the relevant test items should be agreed between the manufacturer and the user department. 5 Basic provisions for insulation requirements and insulation tests 5.1 Overview
The basic provisions of insulation requirements and insulation tests are shown in Table 1. Note: ① For fully insulated three-phase transformers, when the neutral point is not lead out, the full-wave impact test of the neutral point is a special test. When a full-wave impact is applied to three line terminals connected in parallel, its voltage value should be equal to 70% of the impulse withstand voltage value of the line terminal. However, for transformers with voltage levels of 20kV and below, the voltage applied to the line terminals The value should be equal to the line end impulse withstand voltage value minus 1/2 the rated voltage. ②For transformers with U㎡=252kV and a capacity equal to or greater than 120MVA, the lightning full-wave impact test is a factory test. For transformers with U=252kV, the induction withstand voltage test with partial discharge measurement is a factory test. For test conditions, see Article 11.4 of this standard. Inquiries and orders must provide information about the insulation requirements and insulation tests of the transformer, see Appendix A of GB1094.1. 5.2Um<300kV, insulation requirements and insulation test of fully insulated windings 5.2.1 Rated withstand voltage of windings:
a. The rated short-time power frequency withstand voltage is shown in Table 2; b. Rated lightning impulse at the line end The withstand voltage is shown in Table 2, c. The peak value of the rated impulse withstand voltage of the neutral point terminal is the same as that of the line terminal. 5.2.2 The rated withstand voltage is verified by the following insulation test: a. For the external withstand voltage test, see Chapter 10 of this standard (a factory test). This test is used to test the power frequency voltage withstand strength of the tested winding to other windings and to ground. For the induction withstand voltage test, see Article 11.2 of this standard (a factory test). b.
This test is used to test the power frequency voltage withstand strength of the tested winding to other windings and to ground. For the lightning full-wave and cut-wave impact tests at the line end, see Chapters 12 and 13 of this standard (type test). c.
This test is used to test the impulse voltage withstand strength of each line end to the ground, to other windings, and along the tested coil itself. d. For the lightning full-wave impact test of the neutral point terminal, see Section 12.3.2 of this standard (type test). This test is used to test the impulse voltage withstand strength of the neutral terminal to ground and other windings. Note: Distribution transformers installed in some areas will be subject to severe atmospheric overvoltage. At this time, after consultation between the manufacturer and the user department, a higher test voltage value or additional test items can be added. This standard does not provide specific provisions. 5.3Um<300kV, insulation requirements and insulation test of graded insulated windings 5.3.1 Rated withstand voltage of windings:
a. The rated short-time power frequency withstand voltage of the line end is shown in Table 2. The rated lightning impulse resistance of the line end See Table 2 for the voltage received. See Article 5.5 and Table 3 of this standard for the rated short-time power frequency withstand voltage of the b.
neutral point terminal. c.
d. The lightning full-wave impact test of the neutral point terminal is shown in Section 12.3.2 of this standard (type test). The lightning full-wave impulse withstand voltage of the neutral point terminal is shown in Table 3.
Winding
Type
Um<
300kv
Fully insulated
Um
300k
Grading
Insulation
Um
300
kw
Grading
Insulation
According to method
Method 1
(See
Section 5.
4.1
)
Determine the specifications of
norms||tt ||Um
300
kv
Grading
Insulation
According to the method
Method 2
(see || tt||No. 5.
4.2
section)
Determine the specifications of
GB1094.3—85|| tt||Table 1
The requirements and test guidelines for different types of windings constitute the withstand voltage of the insulation level and related terms and tables (1) Power frequency, see Article 5.2, Table 2
(2) Thunder lightning impact, see Article 5.2, Table 2 (3) Lightning full-wave impact on the neutral point terminal, see Article 5.5.3, Table 2
(1) Works on the line end Frequency, see Article 5.3, Table 2 (2) Lightning impulse on the line terminal, see Article 5.3, Table 2 (3) Power frequency on the neutral point terminal, see Article 5.5, Table 3 (4) Neutral Full-wave lightning impact on point terminals, see Section 5.5.3, Table 3
(1) Power frequency on the line terminal, see Section 5.4.1, Table 2 (2) Lightning on the line terminal Full-wave and cut-wave impact, see Clause 5.4.1, Table 2
(3) Power frequency at neutral point terminal, see Clause 5.5, Table 3
(4) For the lightning full wave impact on the line terminal, see Section 5.5.3, Table 3
(1) For the lightning full wave and cut wave impact on the line terminal, see Section 5.4.2, Table 2||tt || (2) Operational impact on the line terminal, see Section 5.4.2, Table 2
(3) Power frequency on the neutral point terminal, see Section 5.5, Table 3 (4) Neutral Lightning full-wave impact on point terminals, see Section 5.5.3, Table 3
Item and test clause number
Test item
Externally applied withstand voltage test, see Chapter 10
For lightning full-wave and chopped-wave impact tests on the line terminal, see Chapters 12 and 13
For lightning full-wave impact tests on the neutral terminal, see Section 12.3.2 ||tt| |Induction withstand voltage test, see Article 11.2
For withstand voltage test corresponding to the insulation level of the neutral point, see Chapter 10
For lightning full wave and chopped wave impact test on the line terminal, see Chapter 12 and 13
Lightning full-wave impact test on neutral point terminal, see Section 12.3.2
Induction withstand voltage test, see Section 11.3
and neutral For the withstand voltage test corresponding to the point insulation level, see Chapter 10
For the lightning full-wave impact test on the line terminal, see Chapter 12 For the lightning cut-wave impact test on the line terminal, see Chapter 13 Neutral point terminal Lightning full-wave impact test, see Clause 12.3.2
Induction withstand voltage test, see Clause 11.3
Induction withstand voltage test with partial discharge measurement, see Clause 11.4|| tt||Withstand voltage test corresponding to the insulation level of the neutral point, see Chapter 10
Thunder full-wave impact test on the line end, see Chapter 12 Lightning cut-wave impact test on the line end, see Chapter 12 Chapter 13 Lightning full-wave impulse test on the neutral point terminal, see clause 123.2
Operational impact test on the line terminal, see Chapter 14 Induction withstand voltage test with partial discharge measurement, see clause 11.4
Test
Category
Factory
Type
Type
Factory
Factory
Type|| tt||Type
Factory
Factory
Factory
Type
Type
Factory
Factory||tt| |Factory
Factory
Type
Type
Factory
Factory
Voltage
Level
kv
3
6
10
15
20
35
63
110|| tt | | 220 | | tt | | 330 | | tt | | 500 |
kV (effective value)
3.5
6.9
11.5
17.5
23.0
40.5||tt| |69.0
126.0
252.0
363.0
550.0
voltage level
kv
110
220
330
500
rated short-time power frequency withstand
voltage (effective value),kVbzxz.net
18
25
35
45
55
85
140
200| |tt||360
395
460
510
630
680
rated lightning impulse withstand voltage (peak value), kV full wave
40
60
75
105
125
200
325
480
850
950
1050
1175
1425
1550
Table 3
Grading Insulation level of neutral point of insulated winding Maximum voltage of equipment U.
(effective value), kV
126
252
363
550| |tt||neutral point grounding method
dead grounding
dead grounding
dead grounding
dead grounding
dead grounding
Small impedance ground
Cut
45
65
85
115
140
220||tt| |360
530
935
1050
1175
1300
1550
1675
rated Short-time power frequency withstand
voltage (effective value), kv
95
85
200
85
230|| tt||85
140
Rated operating impact resistance
voltage (phase to neutral
neutral point, peak value), kv
-| tt||850
950
1050
1175
Lightning full wave impact resistance
voltage (peak value),kv
250
185
400
180
550
180
325
5.3.2 Rated withstand voltage is given by The following is used to verify GB1094.385
a. For induction withstand voltage test, see Chapter 11 of this standard (factory test). This test is used to verify the power frequency voltage withstand strength of the tested winding wire end to the ground and other windings, as well as the power frequency voltage withstand strength between phases and along the tested winding itself. The test shall be carried out in accordance with Article 11.3. b. Lightning full-wave and cut-wave impact tests at the line end, see Chapters 12 and 13 of this standard (type inspection). The purpose of this test is the same as described in Article 5.2.2c. For the externally applied withstand voltage test on the neutral point terminal, see Chapter 10 of this standard (a factory test). c.
The purpose of this test is to verify the power frequency voltage withstand strength of the neutral terminal to the ground. d. For the lightning full-wave impact test on the neutral point terminal, see Article 12.3.2 of this standard (type test). The purpose of this test is the same as Section 5.2.2d.
5.4Um>300kV, insulation requirements and insulation tests for graded insulated windings. For transformers belonging to this type of windings, the relevant specifications and tests have the following two methods to choose from, which should be specified in the "Inquiry and Ordering" Which method to use is explained in "Technical Requirements to Be Made". For induction withstand voltage tests with partial discharge measurements, it should also be stated which of the two different specifications is selected. See Article 11.4 of this standard. 5.4.1 Method 1
5.4.1.1 Rated withstand voltage of winding:
The rated short-time power frequency withstand voltage of the line end is shown in Table 2; a.
b.|| The rated lightning impulse withstand voltage of tt|| line terminal is shown in Table 2; c. The rated short-time power frequency withstand voltage of neutral point terminal is shown in Table 3, d. The rated lightning full-wave impulse withstand voltage of the neutral point terminal is shown in Table 3. 5.4.1.2 The withstand voltage is tested by the following insulation test: The induction withstand voltage test is shown in Chapter 11 of this standard (a factory test), and the test method is as follows Article 11.3 of this standard is carried out. a.
The purpose of this test is as stated in Article 5.3 of this standard. For the lightning full-wave and cut-wave impact tests at the line end, see Chapters 12 and 13 of this standard (belonging to factory and type testing). b.
The purpose of this test is as stated in Article 5.2 of this standard. c. For the externally applied withstand voltage test of the neutral point terminal, see Chapter 10 of this standard (a factory test). The purpose of this test is as stated in Article 5.3 of this standard. d. For the lightning impulse test of the neutral point terminal, see Section 12.3.2 of this standard (type test). The purpose of this test is as stated in Article 5.2 of this standard. 5.4.1.3 For the induction withstand voltage test with partial discharge measurement, see Article 11.4 of this standard (a factory test). 5.4.2 Method 2
5.4.2.1 Rated withstand voltage of the winding:
The rated operating impulse withstand voltage of the line end is shown in Table 2; a.
The rated lightning impulse resistance of the line end The voltage received is shown in Table 2; b.
the rated short-time power frequency withstand voltage of the neutral point terminal is shown in Table 3, c.
d. the rated lightning impulse withstand voltage of the neutral point terminal See Table 3. 5.4.2.2 The rated withstand voltage is verified by the following insulation test: For the operating impact test at the line end, see Chapter 14 of this standard (a factory test). a.
This test is used to test the operational impact withstand capability between the line end and the ground and the three-phase transformer line end. For the lightning full-wave and cut-wave impact tests at the line end, see Chapters 12 and 13 of this standard (belonging to factory and type testing). b.
The purpose of this test is as stated in Article 5.2 of this standard. c. For the externally applied withstand voltage test of the neutral point terminal, see Chapter 10 of this standard (a factory test). The purpose of this test is as stated in Article 5.3 of this standard. d.． The impact test of the neutral point terminal is shown in Section 12.3.2 of this standard (type test). The purpose of this test is as stated in Article 5.2 of this standard. GB1094.3-85
5.4.3 Induction withstand voltage test with partial discharge measurement: From the perspective of the applied voltage under normal operating conditions and temporary overvoltage, the transformer should withstand this test. According to this Carry out in accordance with Article 11.4 of the standard (a factory test).
This test specifies two optional specifications, which should be determined when ordering. The test method applies to all windings of graded insulation transformers.
This test should be carried out after other insulation tests are completed. Note: When performing an operating impulse withstand voltage test on a three-phase transformer, the phase-to-phase test voltage is approximately 1.5 times the withstand voltage of the relative neutral point (see Article 14.3).
5.5 Insulation requirements and tests for neutral point terminals of graded insulated windings 5.5.1 General
The insulation level depends on whether the neutral point terminal is directly connected to the ground. If the neutral terminal is not directly connected to ground, in order to limit transient overvoltage, an overvoltage protection device must be installed between the neutral terminal and ground. Note: The following content involves determining the minimum withstand voltage required for the neutral terminal. Increasing this voltage value is sometimes easy to achieve and can improve the interchangeability of transformers in the system. In addition, due to the test wiring during the induction withstand voltage test, the neutral point insulation level of the winding may need to be designed to be higher (see 11.3).
5.5.2 Directly grounded neutral terminal
The neutral terminal must be firmly grounded, directly or through a current transformer, without any intentionally introduced impedance. During impact testing on the line terminal, the neutral terminal shall be connected directly to earth. 5.5.3 Neutral point terminal not directly grounded
The neutral point terminal is not directly grounded, it can be grounded through a considerable impedance (such as arc suppression coil). The neutral terminals of the individual phase coils can be connected to the regulating transformer. 5.5.4 The method of applying voltage according to the rated lightning impulse voltage method of the neutral point terminal is specified in Section 12.3 of this standard.Test by one of the two test methods described in paragraph 2. This standard does not recommend the neutral point intercepted wave impact test.
6 Tests of transformers with tapped windings
If the tap range is equal to or less than 5%, the insulation test shall be carried out with the transformer in main tap. If the tap range is greater than ±5%, the tap position during the test is selected according to the requirements of the induction withstand voltage test and operating impact test (see Chapter 4).
During the lightning impulse test, the field strength distribution in the insulation varies with the connections of the transformer taps and the overall design of the transformer. Unless the impulse test is required by agreement to be carried out on a particular tap, the impulse test shall be carried out at the two limit taps and the main tap position, on three separate phases of the three-phase transformer or three-phase group of the transformer. Use one of the taps in each case for testing. 7 For the insulation requirements and test conditions of dry-type transformers, please refer to the corresponding national standards.
8 Repeated insulation tests
If a transformer has fully withstood the insulation acceptance test specified in clause 5.2, 5.3 or 5.4 of this standard, and the test is subsequently repeated, then The test voltage should be reduced to 85% of the original value (unless otherwise agreed), and it must be provided that the internal insulation of the transformer has not changed during this period.
Note: This rule does not apply to the inductive withstand voltage test of transformers with partial discharge measurement (see Article 11.4). 9 Insulation of auxiliary wiring
GB1094.3-85
Unless otherwise specified, the wiring and control circuit of the auxiliary power supply should withstand a 2kV (effective value) 1min power frequency withstand voltage (to ground) test , the insulation requirements of motors and other electrical appliances of auxiliary equipment should comply with relevant standards (if the requirements of the standard are lower than the values ??specified for auxiliary wiring alone, these devices sometimes need to be temporarily removed in order to test the wiring). Note: The auxiliary equipment of large transformers is usually removed from the factory for transportation. After assembly at the operating location, it is recommended to use a 1000V megohmmeter for testing. || tt |
The test voltage value should be the peak value of the measured voltage divided by √2. The test should start from a voltage no greater than 1/3 of the specified test value and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be quickly reduced to less than 1/3 of the test value, and then the power supply should be cut off. The full voltage test value added between the winding under test and the ground terminal (including all terminals of the remaining windings and cores, clamps, box shells, etc. are connected together and grounded) should be applied for 60 s.
If no internal insulation breakdown or local damage is found, the test is qualified. Note: For graded insulated windings, only the test voltage specified for the neutral point terminal is tested. Therefore, the wire ends of the winding can only withstand the induced withstand voltage test described in Article 11.3 or 11.4 of this standard.
11 Induction withstand voltage test
11.1 Overview
There are three available methods for testing windings with different insulation types. These three methods are described in 11.2, 11.3 and 11.4. When an AC voltage is applied to the terminals of one winding of the transformer, its waveform should be as sinusoidal as possible. In order to prevent the excitation current from being too large during the test, the frequency during the test should be appropriately greater than the rated frequency. The test voltage value should be the peak value of the measured induced test voltage divided by 2. The test should start at a voltage less than 1/3 of the test voltage and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be reduced to less than 1/3 of the test value as quickly as possible, and then the power supply should be cut off. Unless otherwise specified, in the following items, when the frequency of the test voltage is equal to or less than 2 times the rated frequency, the application time at full voltage shall be 60S.
When the test frequency exceeds twice the rated frequency, the test time should be: 120 × [rated frequency] (s), but not less than 15s [test frequency]
11.2 The high-voltage winding is fully insulated The induction withstand voltage test of a transformer usually stipulates that the test voltage applied to both ends of the coil without tap is equal to twice the rated voltage, but the phase-to-phase test voltage of any three-phase coil should not exceed the value in column 3 of Table 2 Listed rated short-time I frequency withstand voltage. Three-phase coils are best tested using voltages induced in each phase from a symmetrical three-phase supply. If there is a neutral terminal in this winding, it may be connected to earth during the test.
If no internal insulation breakdown or local damage is found, the test is qualified. 11.3 The phase-to-ground induced withstand voltage test Um of transformers with high-voltage windings with graded insulation is <300kV (see 5.3) or ≥300kV, determined according to method 1 (see 5.4.1). The test voltage at the line end is shown in Table 2. Tests on single-phase transformers are usually carried out with the neutral terminal connected to earth. If the voltage ratio between windings can be changed by tapping, tapping can be used to meet the test voltage requirements on different windings at the same time as possible. In special cases (see Chapter 4), the voltage at the neutral terminal can be increased by connecting it to an auxiliary booster transformer, or another winding of the transformer under test can be connected to the high-voltage winding. in series. The test procedure of GB1094.3-85
three-phase transformer includes applying single-phase test voltage three times phase by phase, each time connecting different points of the winding to ground. The recommended test connection method shown in Figure 1 can avoid excessive terminal overvoltage. There are other possible ways. L
LL
Auxiliary booster transformer
L
Figure 1 Connection method for single-phase induction withstand voltage test of graded insulation transformer. The remaining independent windings in the transformer are as follows For star connection, the neutral point should be grounded. For delta connection, one of the terminals should be grounded.
During the test, the voltage of each turn will reach different values ??depending on the test connection method. The choice of test wiring method should be based on the characteristics of the transformer and test equipment. Note: When the coil layout of the transformer is complex, in order to make the test represent as much as possible the true combination of various electrical action intensities in actual operation, it is recommended that the manufacturer and the user department conduct a review of the wiring of all coils during the test during the contract signing stage. . If no internal insulation breakdown or local damage is found, the test is qualified. Connection methods a1, a2, .a3: When the neutral point terminal is designed to withstand a voltage of at least 1/3U, three different methods of connecting the generator to the low-voltage winding shown in the figure can be used. If the transformer has a magnetic circuit without a coil (shell type or five-column core), only a can be used. Connection method b: If the three-phase transformer is not equipped with a coil and serves as a magnetic circuit through which the magnetic flux of the core column under test flows, this connection method is recommended. If the transformer has delta-connected windings, the delta-connected windings must be open during the test. Connection method c: means that an auxiliary boosting transformer provides support voltage U to the neutral point end of the autotransformer under test. The rated voltages of the two auto-coupling connection windings are UN1 and UN2, and the corresponding test voltages are U, U2. The relationship is: U,-UtU,-Ut
UN1
UN2
Ut- U, .uni-u..un?
UNI-UN2|| tt||This connection can also be used for a three-phase three-column core with a coil magnetic circuit and a three-phase transformer whose neutral point insulation is less than 1/3U. 11.4 Partial discharge measurement of transformers with high-voltage windings with graded insulation under induced withstand voltage Um>252kV, see Section 5.4.3.
The test is applied to all graded insulated windings of the transformer, whether these windings are auto-coupled or independent.3—85
Unless otherwise specified, the wiring and control circuit of the auxiliary power supply shall withstand the 2kV (effective value) 1min power frequency withstand voltage (to ground) test, and the insulation requirements for the motors and other electrical appliances of the auxiliary equipment shall Comply with relevant standards (if the requirements of the standard are lower than the values ??specified for auxiliary wiring alone, in order to test the wiring, these devices sometimes need to be temporarily removed). Note: The auxiliary equipment of large transformers is usually removed from the factory for transportation. After assembly at the operating location, it is recommended to use a 1000V megohmmeter for testing. || tt |
The test voltage value should be the peak value of the measured voltage divided by √2. The test should start from a voltage no greater than 1/3 of the specified test value and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be quickly reduced to less than 1/3 of the test value, and then the power supply should be cut off. The full voltage test value added between the winding under test and the ground terminal (including all terminals of the remaining windings and cores, clamps, box shells, etc. are connected together and grounded) should be applied for 60 s.
If no internal insulation breakdown or local damage is found, the test is qualified. Note: For graded insulation windings, only the test voltage specified for the neutral point terminal is tested. Therefore, the wire ends of the winding can only withstand the induced withstand voltage test described in Article 11.3 or 11.4 of this standard.
11 Induction withstand voltage test
11.1 Overview
There are three available methods for testing windings with different insulation types. These three methods are described in Sections 11.2, 11.3, and 11.4. When an AC voltage is applied to the terminals of one winding of the transformer, its waveform should be as sinusoidal as possible. In order to prevent the excitation current from being too large during the test, the frequency during the test should be appropriately greater than the rated frequency. The test voltage value should be the peak value of the measured induced test voltage divided by 2. The test should start at a voltage less than 1/3 of the test voltage and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be reduced to less than 1/3 of the test value as quickly as possible, and then the power supply should be cut off. Unless otherwise specified, in the following items, when the frequency of the test voltage is equal to or less than 2 times the rated frequency, the application time at full voltage shall be 60S.
When the test frequency exceeds twice the rated frequency, the test time should be: 120 × [rated frequency] (s), but not less than 15s [test frequency]
11.2 The high-voltage winding is fully insulated The induction withstand voltage test of a transformer usually stipulates that the test voltage applied to both ends of the coil without tap is equal to twice the rated voltage, but the phase-to-phase test voltage of any three-phase coil should not exceed the value in column 3 of Table 2 Listed rated short-time I frequency withstand voltage. Three-phase coils are best tested using voltages induced in each phase from a symmetrical three-phase supply. If there is a neutral terminal in this winding, it may be connected to earth during the test.
If no internal insulation breakdown or local damage is found, the test is qualified. 11.3 The phase-to-ground induced withstand voltage test Um of transformers with high-voltage windings with graded insulation is <300kV (see 5.3) or ≥300kV, determined according to method 1 (see 5.4.1). The test voltage at the line end is shown in Table 2. Tests on single-phase transformers are usually carried out with the neutral terminal connected to earth. If the voltage ratio between windings can be changed by tapping, tapping can be used to meet the test voltage requirements on different windings at the same time as possible. In special cases (see Chapter 4), the voltage at the neutral terminal can be increased by connecting it to an auxiliary booster transformer, or another winding of the transformer under test can be connected to the high-voltage winding. in series. The test procedure of GB1094.3-85
three-phase transformer includes applying single-phase test voltage three times phase by phase, each time connecting different points of the winding to ground. The recommended test connection method shown in Figure 1 can avoid excessive terminal overvoltage. There are other possible ways. L
LL
Auxiliary booster transformer
L
Figure 1 Connection method for single-phase induction withstand voltage test of graded insulation transformer. The remaining independent windings in the transformer are as follows For star connection, the neutral point should be grounded. For delta connection, one of the terminals should be grounded.
During the test, the voltage of each turn will reach different values ??depending on the test connection method. The choice of test wiring method should be based on the characteristics of the transformer and test equipment. Note: When the coil layout of the transformer is complex, in order to make the test represent as much as possible the true combination of various electrical action intensities in actual operation, it is recommended that the manufacturer and the user department conduct a review of the wiring of all coils during the test during the contract signing stage. . If no internal insulation breakdown or local damage is found, the test is qualified. Connection methods a1, a2, .a3: When the neutral point terminal is designed to withstand a voltage of at least 1/3U, three different methods of connecting the generator to the low-voltage winding shown in the figure can be used. If the transformer has a magnetic circuit without a coil (shell type or five-column core), only a can be used. Connection method b: If the three-phase transformer is not equipped with a coil and serves as a magnetic circuit through which the magnetic flux of the core column under test flows, this connection method is recommended. If the transformer has delta-connected windings, the delta-connected windings must be open during the test. Connection method c: means that an auxiliary booster transformer provides support voltage U to the neutral point end of the autotransformer under test. The rated voltages of the two auto-coupling connection windings are UN1 and UN2, and the corresponding test voltages are U, U2. The relationship is: U,-UtU,-Ut
UN1
UN2
Ut- U, .uni-u..un?
UNI-UN2|| tt||This connection can also be used for a three-phase three-column core with a coil magnetic circuit and a three-phase transformer whose neutral point insulation is less than 1/3U. 11.4 Partial discharge measurement of transformers with high-voltage windings with graded insulation under induced withstand voltage Um>252kV, see Section 5.4.3.
The test is applied to all graded insulated windings of the transformer, whether these windings are auto-coupled or independent.3—85
Unless otherwise specified, the wiring and control circuit of the auxiliary power supply shall withstand the 2kV (effective value) 1min power frequency withstand voltage (to ground) test, and the insulation requirements for the motors and other electrical appliances of the auxiliary equipment shall Comply with relevant standards (if the requirements of the standard are lower than the values ??specified for auxiliary wiring alone, in order to test the wiring, these devices sometimes need to be temporarily removed). Note: The auxiliary equipment of large transformers is usually removed from the factory for transportation. After assembly at the operating location, it is recommended to use a 1000V megohmmeter for testing.
10 Externally applied withstand voltage test
The externally applied withstand voltage test should be conducted using a single-phase AC voltage with any appropriate frequency not less than 80% of the rated frequency and whose waveform is as close to a sine wave as possible.
The test voltage value should be the peak value of the measured voltage divided by √2. The test should start from a voltage no greater than 1/3 of the specified test value and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be quickly reduced to less than 1/3 of the test value, and then the power supply should be cut off. The full voltage test value added between the winding under test and the ground terminal (including all terminals of the remaining windings and cores, clamps, box shells, etc. are connected together and grounded) should be applied for 60 s.
If no internal insulation breakdown or local damage is found, the test is qualified. Note: For graded insulated windings, only the test voltage specified for the neutral point terminal is tested. Therefore, the wire ends of the winding can only withstand the induced withstand voltage test described in Article 11.3 or 11.4 of this standard.
11 Induction withstand voltage test
11.1 Overview
There are three available methods for testing windings with different insulation types. These three methods are described in Sections 11.2, 11.3, and 11.4. When an AC voltage is applied to the terminals of one winding of the transformer, its waveform should be as sinusoidal as possible. In order to prevent the excitation current from being too large during the test, the frequency during the test should be appropriately greater than the rated frequency. The test voltage value should be the peak value of the measured induced test voltage divided by 2. The test should start at a voltage less than 1/3 of the test voltage and should be increased to the test value as quickly as possible in conjunction with the measurement. After the test is completed, the voltage should be reduced to less than 1/3 of the test value as quickly as possible, and then the power supply should be cut off. Unless otherwise specified, in the following items, when the frequency of the test voltage is equal to or less than 2 times the rated frequency, the application time at full voltage shall be 60S.
When the test frequency exceeds twice the rated frequency, the test time should be: 120 × [rated frequency] (s), but not less than 15s [test frequency]
11.2 The high-voltage winding is fully insulated The induction withstand voltage test of a transformer usually stipulates that the test voltage applied to both ends of the coil without tap is equal to twice the rated voltage, but the phase-to-phase test voltage of any three-phase coil should not exceed the value in column 3 of Table 2 Listed rated short-time I frequency withstand voltage. Three-phase coils are best tested using voltages induced in each phase from a symmetrical three-phase supply. If there is a neutral terminal in this winding, it may be connected to earth during the test.
If no internal insulation breakdown or local damage is found, the test is qualified. 11.3 The phase-to-ground induced withstand voltage test Um of transformers with high-voltage windings with graded insulation is <300kV (see 5.3) or ≥300kV, determined according to method 1 (see 5.4.1). The test voltage at the line end is shown in Table 2. Tests on single-phase transformers are usually carried out with the neutral terminal connected to earth. If the voltage ratio between windings can be changed by tapping, tapping can be used to meet the test voltage requirements on different windings at the same time as possible. In special cases (see Chapter 4), the voltage at the neutral terminal can be increased by connecting it to an auxiliary booster transformer, or another winding of the transformer under test can be connected to the high-voltage winding. in series. The test procedure of GB1094.3-85
three-phase transformer includes applying single-phase test voltage three times phase by phase, each time connecting different points of the winding to ground. The recommended test connection method shown in Figure 1 can avoid excessive terminal overvoltage. There are other possible ways. L
LL
Auxiliary booster transformer
L
Figure 1 Connection method for single-phase induction withstand voltage test of graded insulation transformer. The remaining independent windings in the transformer are as follows For star connection, the neutral point should be grounded. For delta connection, one of the terminals should be grounded.
During the test, the voltage of each turn will reach different values ??depending on the test connection method. The choice of test wiring method should be based on the characteristics of the transformer and test equipment. Note: When the coil arrangement of the transformer is complex, in order to make the test represent as much as possible the true combination of various electrical action intensities in actual operation, it is recommended that the manufacturer and the user department conduct a review of the wiring of all coils during the test during the contract signing stage. . If no internal insulation breakdown or local damage is found, the test is qualified. Connection methods a1, a2, .a3: When the neutral point terminal is designed to withstand a voltage of at least 1/3U, the three different methods of connecting the generator to the low-voltage winding shown in the figure can be used. If the transformer has a magnetic circuit without a coil (shell type or five-column core), only a can be used. Connection method b: If the three-phase transformer is not equipped with a coil and serves as a magnetic circuit through which the magnetic flux of the core column under test flows, this connection method is recommended. If the transformer has delta-connected windings, the delta-connected windings must be open during the test. Connection method c: means that an auxiliary booster transformer provides support voltage U to the neutral point end of the autotransformer under test. The rated voltages of the two auto-coupling connection windings are UN1 and UN2, and the corresponding test voltages are U, U2. The relationship is: U,-UtU,-Ut
UN1
UN2
Ut- U, .uni-u..un?
UNI-UN2|| tt||This connection can also be used for a three-phase three-column core with a coil magnetic circuit and a three-phase transformer whose neutral point insulation is less than 1/3U. 11.4 Partial discharge measurement of transformers with high-voltage windings with graded insulation under induced withstand voltage Um>252kV, see Section 5.4.3.
The test is applied to all graded insulated windings of the transformer, whether these windings are auto-coupled or independent.1 style). The test voltage at the line end is shown in Table 2. Tests on single-phase transformers are usually carried out with the neutral terminal connected to earth. If the voltage ratio between windings can be changed by tapping, tapping can be used to meet the test voltage requirements on different windings at the same time as possible. In special cases (see Chapter 4), the voltage at the neutral terminal can be increased by connecting it to an auxiliary booster transformer, or another winding of the transformer under test can be connected to the high-voltage winding. in series. The test procedure of GB1094.3-85
three-phase transformer includes applying single-phase test voltage three times phase by phase, each time connecting different points of the winding to ground. The recommended test connection method shown in Figure 1 can avoid excessive terminal overvoltage. There are other possible ways. L
LL
Auxiliary booster transformer
L
Figure 1 Connection method for single-phase induction withstand voltage test of graded insulation transformer. The remaining independent windings in the transformer are as follows For star connection, the neutral point should be grounded. For delta connection, one of the terminals should be grounded.
During the test, the voltage of each turn will reach different values ??depending on the test connection method. The choice of test wiring method should be based on the characteristics of the transformer and test equipment. Note: When the coil layout of the transformer is complex, in order to make the test represent as much as possible the true combination of various electrical action intensities in actual operation, it is recommended that the manufacturer and the user department conduct a review of the wiring of all coils during the test during the contract signing stage. . If no internal insulation breakdown or local damage is found, the test is qualified. Connection methods a1, a2, .a3: When the neutral point terminal is designed to withstand a voltage of at least 1/3U, three different methods of connecting the generator to the low-voltage winding shown in the figure can be used. If the transformer has a magnetic circuit without a coil (shell type or five-column core), only a can be used. Connection method b: If the three-phase transformer is not equipped with a coil and serves as a magnetic circuit through which the magnetic flux of the core column under test flows, this connection method is recommended. If the transformer has delta-connected windings, the delta-connected windings must be open during the test. Connection method c: means that an auxiliary booster transformer provides support voltage U to the neutral point end of the autotransformer under test. The rated voltages of the two auto-coupling connection windings are UN1 and UN2, and the corresponding test voltages are U, U2. The relationship is: U,-UtU,-Ut
UN1
UN2
Ut- U, .uni-u..un?
UNI-UN2|| tt||This connection can also be used for a three-phase three-column core with a coil magnetic circuit and a three-phase transformer whose neutral point insulation is less than 1/3U. 11.4 Partial discharge measurement of transformers with high-voltage windings with graded insulation under induced withstand voltage Um>252kV, see Section 5.4.3.
The test is applied to all graded insulated windings of the transformer, whether these windings are self-coupling or independent.1 style). The test voltage at the line end is shown in Table 2. Tests on single-phase transformers are usually carried out with the neutral terminal connected to earth. If the voltage ratio between windings can be changed by tapping, tapping can be used to meet the test voltage requirements on different windings at the same time as possible. In special cases (see Chapter 4), the voltage at the neutral terminal can be increased by connecting it to an auxiliary booster transformer, or another winding of the transformer under test can be connected to the high-voltage winding. in series. The test procedure of GB1094.3-85
three-phase transformer includes applying single-phase test voltage three times phase by phase, each time connecting different points of the winding to ground. The recommended test connection method shown in Figure 1 can avoid excessive terminal overvoltage. There are other possible ways. L
LL
Auxiliary booster transformer
L
Figure 1 Connection method for single-phase induction withstand voltage test of graded insulation transformer. The remaining independent windings in the transformer are as follows For star connection, the neutral point should be grounded. For delta connection, one of the terminals should be grounded.
During the test, the voltage of each turn will reach different values ??depending on the test connection method. The choice of test wiring method should be based on the characteristics of the transformer and test equipment. Note: When the coil layout of the transformer is complex, in order to make the test represent as much as possible the true combination of various electrical action intensities in actual operation, it is recommended that the manufacturer and the user department conduct a review of the wiring of all coils during the test during the contract signing stage. . If no internal insulation breakdown or local damage is found, the test is qualified. Connection methods a1, a2, .a3: When the neutral point terminal is designed to withstand a voltage of at least 1/3U, three different methods of connecting the generator to the low-voltage winding shown in the figure can be used. If the transformer has a magnetic circuit without a coil (shell type or five-column core), only a can be used. Connection method b: If the three-phase transformer is not equipped with a coil and serves as a magnetic circuit through which the magnetic flux of the core column under test flows, this connection method is recommended. If the transformer has delta-connected windings, the delta-connected windings must be open during the test. Connection method c: means that an auxiliary booster transformer provides support voltage U to the neutral point end of the autotransformer under test. The rated voltages of the two auto-coupling connection windings are UN1 and UN2, and the corresponding test voltages are U, U2. The relationship is: U,-UtU,-Ut
UN1
UN2
Ut- U, .uni-u..un?
UNI-UN2|| tt||This connection can also be used for a three-phase three-column core with a coil magnetic circuit and a three-phase transformer whose neutral point insulation is less than 1/3U. 11.4 Partial discharge measurement of transformers with high-voltage windings with graded insulation under induced withstand voltage Um>252kV, see Section 5.4.3.
The test is applied to all graded insulated windings of the transformer, whether these windings are auto-coupled or independent.
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