This standard applies to dry-type power transformers (including autotransformers) with voltage levels of 35kV and below. This standard does not apply to the following small and special dry-type transformers: single-phase transformers with a rated capacity less than 1kVA and multi-phase transformers with a rated capacity less than 5kVA; transformers for static converters; starting transformers; test transformers; explosion-proof and mining transformers ; Welding transformer; Voltage regulating transformer; Special small safety power transformer. When there are no corresponding standards for the above transformers or other special transformers, this standard may be quoted in part or in full. GB 6450-1986 Dry-type power transformer GB6450-1986 standard download and decompression password: www.bzxz.net

General
National Standard of the People's Republic of China
Dry-type power transformers
Dry-type power transformers
This standard is equivalent to the international standard IEC726 (1982) "Dry-type Power Transformers" . 1.1 Scope
UDC 621.314
.211
GB6450—86
This standard applies to dry-type power transformers (including autotransformers) with voltage levels of 35kV and below. . This standard does not apply to the following small and special dry-type transformers: single-phase transformers with a rated capacity less than 1kVA and multi-phase transformers with a rated capacity less than 5kVA: transformers for static converters;
starting transformers: ||tt| |Test transformer;
Locomotive transformer;
Flameproof and mining transformer;
Welding transformer;
Regulating transformer,
Special small safety Power transformer.
When there are no corresponding standards for the above transformers or other special transformers, this standard can be quoted in part or in full. The relevant clauses in each part of GB1094 "Power Transformer" quoted in the provisions of this standard should be understood as the corresponding clauses of the following standards:
GB1094.1-85 "Power Transformer
GB1094.285" Power transformer
GB1094.3-85《Power transformer
GB1094.4-85》Power transformer
GB1094.5-85《Power transformer
1.2 Conditions of use| |tt||1.2.1 Normal use conditions
Part 1,
General provisions》,
Part 2
Temperature rise》,
and insulation test》
Part 3
Tap and connection method》,
Part 4
Part 5
Use that meets the following requirements Conditions are those of normal use. Altitude
a.
The altitude does not exceed 1000m.
Note: When the altitude exceeds 1000m, see Section 1.2.2. b. Ambient temperature
Maximum temperature
+40℃,
Maximum daily average temperature +30℃;
Ability to withstand short circuit》.
Maximum annual average temperature +20℃;
-30℃ (applicable to outdoor transformers) 3 Minimum temperature
Minimum temperature
-5℃ (applicable to indoor internal transformer). Note: Above these temperatures, see paragraph 1.2.2. Released by the National Bureau of Standards on 1986-05-29
Implemented on 1987-05-01
c. Waveform of the power supply voltage
The waveform of the power supply voltage is approximately a sine wave. d. Symmetry of multi-phase power supply voltage
GB6450-86
The power supply voltage connected to the multi-phase transformer should be approximately symmetrical. 1.2.2 Provisions on special conditions of use
Users should specify in the inquiry form the conditions of use that are not included in the normal conditions of use in Section 1.2.1 (see Appendix A and Appendix B).
For transformers designed for normal use conditions that do not meet the requirements of Article 1.2.1, such as higher cooling air temperatures or altitudes exceeding 1000m, the supplementary requirements for ratings and testing (within the specified range) are provided in Clauses 3.2.2, 3.2.3 and 4.2. For temperature conditions and special operating conditions exceeding the limits specified in the supplementary requirements, such as when the cooling air circulation is restricted, the temperature rise shall be determined by the manufacturer and the user through consultation.
1.3 Definitions
The following definitions apply to this standard. Other nouns and predicates used in this standard can be found in the provisions of "Electrical Terminology" such as GB1094.1 or GB2900.1-82, GB2900.1582 and GB2900.19-82. 1.3.1 Dry-type transformer
A transformer in which the core and coil are not immersed in insulating liquid. 1.3.1.1 Dry-type transformer with enclosed coil
Dry-type transformer with one or several coils enclosed by solid insulation. 1.3.1.2 Dry-type transformers without encapsulated coils Dry-type transformers without any coils encapsulated by solid insulation. 1.3.2 Dry-type transformers are classified by shell
1.3.2.1 Sealed dry-type transformer
The transformer has a sealed protective shell, and the shell is filled with air or some kind of gas. The sealing performance of its shell should prevent the air or certain gases in the shell from exchanging with the outside world, that is, it is a non-breathing transformer. NOTE: The inflatable transformer must remain inflated throughout its operation. 1.3.2.2 Fully enclosed in-type transformer
An air-filled dry-type transformer in which the protective shell of the transformer prevents external air from circulating to cool the core and coils, but the air in the shell can still exchange with the atmosphere. | | tt | 1.3.2.4 Non-enclosed in-type transformer
The transformer does not have a protective shell, and its core and coil are a dry-type transformer that are cooled by outside air. 1.4 Tap
Same as Chapter 1 of GB1094.4. When using a non-excited tap changer or connecting piece, the preferred tap range is ±5%: 5% per level is ±5%, and 2.5% per level is ±2×2.5%. 1.5 Connection method
See Chapter 2 of GB1094.4. | | tt |
2 Rating
Insulation heat resistance grade
A
B
c
F and H
2.1 Rating
2.1.1 Overview
GB6450-86
Table 1 The maximum allowable value of the coil average temperature θ after short circuit ?2, ℃
Copper
180
250
350
350
aluminum
180
200
200
manufacturing plant Various ratings of the transformer should be specified and marked on the nameplate (see Article 2.2). These ratings should ensure that the transformer can output rated current without exceeding the rated voltage and frequency of this standard when the external voltage is the rated voltage and rated frequency. Temperature rise limits specified in Chapter 3. 2.1.2 Rated capacity
The rated capacity shall be subject to the use conditions specified in Article 1.2, and shall be expressed as the product of the rated voltage, rated current and the corresponding phase coefficient (as shown in Table 2).
Table 2 phase coefficient
Number of phases
1
3
Phase coefficient
1
This rated capacity is Equivalent to continuous operation capacity. However, dry-type transformers that comply with this standard can be overloaded, and the overload guidelines will be proposed later, which will serve as a supplement to this standard. 2.1.3 The priority number of rated capacity
is the same as GB1094.1 Article 4.3.
2.1.4 Operation when voltage is higher than rated voltage
Same as GB1094.1 Article 4.4.
2.2 Nameplate
Each transformer must be equipped with a weatherproof nameplate. The nameplate should be installed in a conspicuous location. The following items should be indicated on the nameplate, and the content of the mark must be permanently kept clear (it can be marked by etching, engraving or printing) transformer name (see definition in Article 1.3), model, and product code; a.
b.
c.
d.
standard code;
manufacturer name (including country name);
Iduhiro serial number,
e .
f.
g.
h.
1.
j.
k.
1.
m.
n.
0.
p.
q.
r.
GB6450-86
Year and month of manufacture;
Insulation system temperature (or grade) and maximum allowable temperature rise for all coils or each coil (if necessary) (see 3.2.1 model); number of phases;
rated capacity of various cooling methods;
rated frequency;
rated voltage, including tap voltage (if there is a tap); each Rated current of cooling method;
connection group label, winding connection diagram (for 2000kVA and below, the connection diagram does not need to be drawn); impedance voltage under rated current, determined according to GB1094.1 Article 8.4; cooling method, use Conditions (indoor, outdoor use, altitude exceeding 1000m, etc.); filling medium (only applicable to sealed structure); operating pressure range (only applicable to sealed structure) maximum and minimum absolute pressure based on the shell design (only applicable to sealed structure) type structure), the pressure and temperature of the filling medium during sealing (only applicable to sealed structure), total weight,
s.
insulation level (the rated withstand voltage values ??of all coils should be marked On the nameplate. For standard marking principles, see Chapter t.
3 of GB1094.3).
3 Cooling method and temperature rise
3.1 Marking of cooling method
3.1.1 Letter code
The transformer should be marked according to the cooling method used. The letter codes used for various cooling methods are given in Table 3. Table 3 letter code
type of cooling medium
empty
gas
gas
body
circulation type
natural Cycle
Forced cycle
Generation
G
No.
N
F
3.1.2 Arrangement of letter codes
Transformers that do not have a protective shell or that cooling air can circulate through the interior of the shell only use a two-letter code to identify the cooling medium (air) in contact with the coil or the coating surface of the coil. Each cooling method of various other transformers (the ratings specified by the manufacturer are based on the cooling method) should be marked with a four-letter code.
The order of the letter codes used is as listed in Table 4. For different cooling methods of the same equipment, the letter code components are separated by slashes. The first letter
GB6450-86
The order of the letter codes in Table 4
The second letter
indicates the cooling medium in contact with the coil
Type of cooling medium
Circulation type
The third letter
The fourth letter
indicates the type of cooling medium in contact with the external cooling system|| tt||Circulation type
For example: a self-cooling transformer without a protective casing or in which cooling air can circulate through the interior of the casing is marked AN. For a transformer in which the cooling air cannot circulate through the protective shell and is self-cooled by air inside and outside the shell, its mark is ANAN.
For a transformer installed in a sealed enclosure, the inside of the enclosure is naturally cooled by nitrogen and has two cooling methods: self-cooling or air cooling outside the enclosure. Its mark is GNAN/GNAF. || tt | When a transformer is designed not to exceed the value specified in item b of Clause 1.2.1, when tested in accordance with Clause 5.11, the temperature rise of its coil, core and metal parts shall not exceed the specified limit in Table 5.
For the coil temperature rise specified in column 3 of Table 5, the permissible hottest spot temperature is as shown in column 2, which applies only to the insulation of electrical equipment within the scope of this standard.
Various insulation materials may be used individually or in combination, as long as the temperature in the insulation system does not continuously exceed the specified value when operating under rated conditions.
In addition, for a specified insulation system, its permissible maximum point temperature shall not be such that the electrical and mechanical properties of the coil insulation are compromised. Note: The letters in column 2 of Table 5 indicate the temperature grade of the insulating material. Table 5 Temperature rise limit value
1
Part
Coil
(Temperature rise measured by resistance method)
Core, metal parts and related components adjacent material 2
insulation system temperature, ℃
105(A)
120(E)
130(B)
155(F)
180(H)
220(C)
3
Maximum temperature rise, K
60
75||tt| | 80 | |tt||GB6450-86
3.2.2 The temperature rise of transformers designed for higher ambient temperatures or for special air cooling conditions is reduced if the transformer is designed according to the following conditions. That is, the temperature of the cooling air exceeds one of the maximum values ??stipulated in item b of Section 1.2.1, but the excess value is not greater than 10K, then the allowable temperature rise of the coil shall be reduced according to the following conditions: When the exceedance When the temperature is less than or equal to 5K, it should be reduced by 5K. When the exceeded temperature is greater than 5K but less than or equal to 10K, it should be reduced by 10K. When the temperature exceeds one of the values ??specified in item b of Section 1.2.1, and this exceeds the value When it is greater than 10K, the allowable temperature rise should be determined by the manufacturer and the user through consultation.
Any site conditions that may restrict cooling air or may produce higher ambient air temperatures should be addressed by the user. 3.2.3 Reduction in temperature rise of transformers designed for high altitudes Unless otherwise specified by the manufacturer and user, for transformers operating at an altitude exceeding 1000m but still being tested at normal altitudes, the temperature rise limits listed in Table 5 The value must be decremented accordingly. For parts where the altitude of the operating location exceeds 1000m, the temperature rise is reduced by every 500m level:
2.5%,
self-cooling transformer
air-cooled transformer||tt| |5%.
Note: ① When using the transformer provided by the department in a high-altitude operating location, the ambient temperature is lower than the maximum temperature, daily average temperature and annual average temperature specified in Section 1.2.1, and it complies with the altitude. When the temperature decreases by 5K or more for every 1000m increase, it is considered that the increase in temperature rise of the transformer due to poor heat dissipation when the transformer is operated at high altitude has been compensated by the decrease in ambient temperature. Therefore, the temperature rise limit during normal altitude testing is No correction will be made.
② If the operating altitude of the transformer is lower than 1000m, and the altitude of the test site is higher than 1000m, the measured temperature rise should be based on the part of the test site with an altitude exceeding 1000m in steps of every 500m according to the above-mentioned data. reduce. 4 Insulation level
4.1 Overview
The insulation level of transformers used in general distribution networks or industrial systems should comply with the requirements of Series I or Series II in Table 6. The insulation level of Series I or Series II should be selected according to the degree of lightning overvoltage and operating overvoltage of the transformer, the neutral point grounding method and the type of overvoltage protection device (see GB311.1-83 "High-voltage power transmission and transformation equipment"). Insulation coordination"). However, when the transformer is used in a special system with lower insulation requirements than the general situation and does not need to be subjected to lightning impulse tests, as long as experience proves feasible, its rated short-time power frequency withstand voltage is allowed to be lower than the value specified in Table 6. In this regard Reduced test voltage values ??are not recommended by this standard.
voltage level
kv
3
6
10
15
20
35| |tt||Table 6 Insulation Level
Rated short-time power frequency withstand voltage (effective) Maximum voltage U (effective value) of the equipment
kv
1.1||tt| |3.5
6.9
11.5
17.5
23
40.5
kv
3
10
20
28
38
50
70
rated lightning impulse withstand voltage (peak value)
kv
1
20
40
60
75
95
145
40|| tt||60
75
95
125
170
GB6450-86
4.2 Transformers operating at high altitude
When the transformer operates at an altitude between 1000 and 3000m, but the test is conducted at a normal altitude, its rated short-time power frequency withstand voltage value shall be based on the installation location exceeding 1000m. The part increases by 6.25% every 500m. Note: The above requirements do not apply to sealed dry-type transformers, but special considerations should be made for bushings. 5 Test
5.1 General requirements for testing
Unless otherwise agreed between the manufacturer and the user, the test shall be conducted at the manufacturer. The transformer shall withstand the test items specified below. Periodic type tests should be carried out at least once every five years. When conducting insulation tests according to Articles 5.6, 5.7 and 5.8, the temperature of the transformer should be close to the ambient temperature. During the test, all parts and components that may affect the performance of the transformer should be assembled. Unless otherwise agreed between the manufacturer and the user, the tapped coil should be in the main tap position.
Unless otherwise specified in the relevant test provisions, the test of all characteristics of the transformer except insulation is based on rated conditions. Load loss, impedance voltage and short-circuit impedance should be corrected to the reference temperature, which is the maximum temperature rise of the coil in column 3 of Table 5 plus 20K.
Note: When each winding of the transformer is composed of different insulation system temperatures, the transformer only uses one reference temperature, which corresponds to the higher insulation system temperature.
5.2 Winding resistance measurement (factory test)
See Section 8.2.1 in GB1094.1. The temperature during measurement should be the average of the readings of several thermometers (at least 3) placed on the surface of the coil. The resistance and temperature of the coil should be recorded simultaneously, and the coil temperature measured with a thermometer should be approximately equal to the temperature of the medium around it. 5.3 For the calibration of voltage ratio test and voltage vector relationship (factory test), see Article 8.3 of GB1094.1.
5.4 Impedance voltage (main tap), short-circuit impedance and load loss measurement (factory test) see Article 8.4 in GB1094.1.
5.5 No-load loss and no-load current measurement (factory test) see Article 8.5 in GB1094.1.
5.6 Externally applied withstand voltage test (factory test)
See Chapter 10 in GB1094.3.
If other values ??have not been agreed upon between the manufacturer and the user, the test voltage shall comply with the provisions of Table 6. The test voltage shall be applied between the winding under test and the earthed enclosure. During the test, all other windings, cores, and clamps are connected together and grounded. The test voltage application time is 60s. 5.7 Induction withstand voltage test (factory test)
5.7.1 Overview
Apply an AC voltage to one winding terminal of the transformer, and its waveform should be a sine wave as much as possible. In order to prevent the excitation current from being too large during the test , the frequency should be appropriately greater than the rated frequency during the test. The peak value of the induced test voltage should be measured, and the peak value divided by 2 should equal the test value. The test should start from less than 1/3 of the test voltage value and should be increased to the test value as quickly as possible in conjunction with the measurement. At the end of the test, 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, 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 60 s. When the test frequency exceeds 2 times the rated frequency, the test duration should be: 120× (rated frequency)
(test frequency)
5.7.2 Test voltage
(s) , but not less than 15s. Www.bzxZ.net
GB6450-86
It is usually stipulated that the test voltage applied to both ends of the coil without tap is equal to twice the rated voltage, but the same test voltage of any three-phase coil should not exceed the table 6Rated short-time withstand voltage listed in column 3. Three-phase coils are best tested with voltages induced in each phase of a symmetrical three-phase supply. If there is a neutral terminal in the winding, it can be connected to earth during the test.
If no abnormal phenomena occur during the test, the test is deemed to be qualified. 5.8 Lightning impulse test (type test)
See Chapter 12 in GB1094.3.
The test voltage should comply with the requirements of series I or series II voltage values ??in Table 6. The test shock wave should be the standard lightning shock full wave: 1.2±30%/50±20%μs
The test voltage generally adopts negative polarity. The test sequence for each line terminal is: first conduct a verification shock between 50% and 75% of the full voltage, and then conduct 3 full voltage shocks. When ordering, after consultation between the manufacturer and the user, the positive polarity can also be used for the test, but sudden changes in polarity must be avoided at this time. Note: During the lightning impulse test of dry-type transformers, capacitive partial discharge in the air may occur, which does not cause harm to the insulation. This partial discharge will cause the current waveform to change, but the voltage waveform will not change or only slightly. Variety. 5.9 Repeated insulation test
If the transformer has been subjected to the insulation acceptance test in accordance with the provisions of 5.6, 5.7, and 5.8, and the test is subsequently repeated, the test voltage will be reduced to 85% of the original test value, and at the same time here During this period, the internal insulation of the transformer must not be changed in any way. 5.10 Partial discharge measurement (special test) 5.10.1 Overview
Partial discharge measurement is carried out in accordance with the corresponding national standards and Appendix A in GB1094.3. This test can be carried out on various dry-type transformers, and it is especially suitable for transformers with encapsulated coils. 5.10.2 Basic measurement circuit (typical circuit only) The basic measurement circuit for the partial discharge test is shown in Figures 1 and 2. Measuring Instruments
Low-voltage winding
High-voltage winding
Figure 1 Basic measurement circuit of single-phase transformer partial discharge test Measuring Instrument Alliance
Low-voltage winding
High-voltage winding
(delta connection or star connection)
Figure 2 Basic measurement circuit for partial discharge test of three-phase transformer GB6450-86
C in the figure is a capacitor without partial discharge (its capacitance The value should be large enough compared to the capacitance C. of the correction generator). C is connected in series with the measurement impedance B and connected to each high-voltage terminal to be measured. 5.10.3 Correction of the measuring circuit
The attenuation of the discharge pulse will occur in both the winding and the measuring circuit. Calibration is based on the provisions of Appendix A of GB1094.3, and the simulated discharge pulse generated by a standard-compliant calibration device is applied to the transformer terminals. The repetition frequency of the correction pulse is on the order of 2 times the frequency of the excitation voltage.
5.10.4 Method of applying voltage
Partial discharge measurement should be carried out after all insulation tests are completed. Depending on whether the transformer is three-phase or single-phase, it determines whether its low-voltage winding is powered by three-phase or single-phase power. The voltage waveform should be as close to a sine wave as possible and its frequency should be appropriately higher than the rated frequency to avoid excessive excitation current during the test. The test procedures are according to item 5.10.4.1 or 5.10.4.2 respectively. Note: When the operating voltage of the transformer is significantly lower than the maximum voltage value of the equipment, the reduction value of the pre-applied voltage and the measured voltage can be selected according to the agreement between the manufacturer and the user.
5.10.4.1 Three-phase transformer
a. When the winding is connected to a system that is directly grounded or grounded through a small impedance:
1.5Um
J3
line-to-ground preconditioning
1.1Um should be added first | |tt | . Line pair
b. When the winding is connected to a system that is not grounded or grounded through a considerable impedance (such as an arc suppression coil): a pre-voltage of 1.5Um relative to the phase should be added first, and the induced voltage withstand time is 30s. At this time, there is a line Terminal ground. Then apply a relative phase voltage of 1.1Um for 3 minutes without cutting off the power supply, and the partial discharge amount during this period should be measured. The test is then repeated with the other line terminal connected to ground.
5.10.4.2 Single-phase transformers
Single-phase transformers used in three-phase systems are tested in the same way as three-phase transformers. At this time, it should be noted that the maximum voltage Um of the equipment represents the voltage of the phase.
If a single-phase transformer is operated in star connection and the test is carried out in accordance with item 5.10.4.1 b, repeated testing with the other line terminal grounded is not necessary.
5.10.5 Allowable value of partial discharge
The allowable value of partial discharge measured according to the above method shall be determined by the manufacturer and the user through consultation. In case of dispute, Appendix A of GB1094.3 shall be used Detailed study procedures are addressed. 5.11 Temperature rise test (type test)
See sections 3.1.1, 3.1.2, 3.1.3, 3.3, 3.9.1, 3.9.2 and 3 in GB1094.2.9.3 and other terms. 5.11.1 Method of applying load
Any one of the following methods can be selected by the manufacturer. 5.11.1.1 Direct load method *
Excite one winding of the transformer, preferably the inner winding, at the rated voltage, and connect an appropriate load to the other winding so that both windings pass the rated voltage. current. 5.11.1.2 Mutual loading method*
This is a better method and is suitable for situations where two identical transformers are available. Connect two transformers in parallel, one of which is the transformer under test. It is best to excite the internal winding at the rated voltage of the transformer under test. Use different voltage ratios or input a certain voltage value to make the rated current flow through the tested transformer. 5.11.1.3 Simulated load method (according to the agreement between the manufacturer and the user) * Before passing the test current to each coil, in order to reduce the test time, the core can be excited for a period of time (preferably not less than 12h).
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