This standard applies to three-phase and single-phase power transformers (including autotransformers). When there is no corresponding standard for small and special transformers (such as single-phase transformers with a rated capacity less than 1kVA and three-phase transformers with a rated capacity less than 5kVA; mutual inductors; converter transformers; electric locomotive traction transformers; starting transformers; test transformers; welding transformers), this standard can be used as a reference. GB 1094.1-1996 Power transformers Part 1 General provisions GB1094.1-1996 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Power transformers
Part 1. General
CB 1094.1—1996
Replaces GB1094-1—85Www.bzxZ.net
GB 1094-4—85
This standard is equivalent to [EC76-1-1993 Power transformers Part 1 General]. 1 Scope of application and conditions of use
1. 1 Scope of application
This standard applies to three-phase and single-phase power transformers (including autotransformers). When there is no corresponding standard for small and special transformers (such as single-phase transformers with a rated capacity of less than 1kVA and three-phase transformers with a rated capacity of less than 5kVA, mutual inductors, converter transformers, electric locomotive traction transformers, starting transformers; test transformers, welding transformers), this standard can be used as a reference.
1.2 Conditions of use
1.2.1 Normal conditions of use
The technical requirements of this standard for transformers are stipulated under the following conditions of use. a. Altitude
Altitude shall not exceed 1 000 tm.
b. Ambient temperature and cooling medium temperature
Highest temperature +40℃
Average temperature of the hottest month
+30℃,
Highest annual average temperature +20℃;
Lowest temperature -25℃ (applicable to outdoor transformers); Lowest temperature -5℃ (applicable to indoor transformers) The highest temperature of cooling water at the water inlet of the water cooler is +25℃. Waveform of power supply voltage
The waveform of power supply voltage is similar to a sine wave. Note: For public power supply systems, this requirement is not strict. However, when there are powerful inverter load equipment, it should be considered according to traditional rules. The total harmonic content in the distorted waveform is not more than 5%, and the even-order wave content is not more than 1%. At the same time, the influence of harmonic current on load loss and temperature rise should also be considered.
d. Symmetrical three-phase power supply voltage
For three-phase transformers, the three-phase power supply voltage should be roughly symmetrical. e. Installation environment
The installation environment has no obvious pollution (transformer bushings or transformer insulation do not need to be specially considered). Ground acceleration a caused by earthquake: less than 3m/s in the horizontal direction and less than 1.5m/g in the vertical direction (no special consideration is needed in the design. Approved by the State Administration of Technical Supervision on March 31, 1996 and implemented on December 1, 1996)1\).
1.2.2 Provisions for special use conditions
GB 1094.11996
Any special use conditions that need to be met in addition to the normal use conditions specified in Article 1-2.1 should be stated when inquiring and ordering (see Appendix A).
Under special use conditions, the transformer ratings and test rules are otherwise specified: a. Wet rise and cooling at higher ambient temperatures or high altitudes: Oil-immersed transformers shall comply with the provisions of GB1094.2, and dry-type transformers shall comply with the provisions of GB6450.
b. External insulation at high altitudes: Oil-immersed transformers shall comply with the provisions of GB1094.3 and GB10237, and dry-type transformers shall comply with the provisions of GB6450.
2 Reference standards
GB321-80 Priority numbers and priority number systems
GB1094.2-1996 Power transformers Part 2 Temperature rise 5 Power transformers Part 3 Insulation levels and insulation tests GB 1094. 3--85
GB 1094. 5-85
5 Power transformers Part 5 Ability to withstand short circuits GR 2900.15-82 Electrical terminology
Transformer Transformer Reactor Regulator
GB4208-93 Enclosure protection grade (IP code) GB4109-88 Technical conditions for high-voltage bushings
GB5582/T-93 External insulation pollution migration grade of high-voltage power equipment GB 6450—86 Dry-type power transformers
GB/T6451—1995 Technical parameters and requirements of three-phase oil-immersed power transformers GB7328—87 Determination of sound levels of transformers and reactors GB10237—88 Insulation levels and insulation tests of power transformers Air gaps of external insulation
GB/T13499—92 Guidelines for application of power transformers GB/T19001--94 Quality system Quality assurance model for design, development, production, installation and service GB/T 15164—94 Guidelines for loads of oil-immersed power transformers 3 Terms
The following terms apply to this standard, and other terms are in accordance with GB2900.15. 3.1 General terms
3.1.1 Power transformer
A stationary device with two or more windings, which, in order to transmit electrical energy, converts the AC voltage and current of one system into the voltage and current of another system at the same rated rate through electromagnetic induction, and usually the values ​​of these current and voltage are different. 3.1.2 Autotransformer
A transformer with at least two windings with a common part. 3.1.3 Booster transformer
A transformer with a series winding connected to the line to change the line voltage value and (or) phase and a magnetizing winding. 3.1.4 Oil-immersed transformer
A transformer with both the core and the winding immersed in oil. Note: Any insulating liquid (mineral oil or other products) is considered as oil. Instructions for use:
1] my country is located in an earthquake-prone area, so the requirements for ground acceleration are inconsistent with IEC. IEC stipulates that the ground acceleration a is less than 2 m/s3.1.5 Dry-type transformer
GB 1094.1—1996
A transformer with neither the core nor the winding immersed in insulating liquid. 3.1.6 Oil protection system
In oil-immersed transformers, an oil protection system is set to adapt to the thermal expansion of the oil to reduce or prevent the oil from contacting the outside air. 3.2 Terminals and neutral point
3.2.1 Terminals
Conductive parts used to connect windings to external conductors. 3.2.2 Line terminals
A type of terminal used to connect conductors in an electrical network. 3.2.3 Neutral point
A point in a symmetrical voltage system that is usually at zero potential. 3.2-4 Neutral point terminal
For three-phase transformers or three-phase groups composed of single-phase transformers, it refers to the terminal connected to the common point (neutral point) of a star connection or a zigzag connection. b. For single-phase transformers
It refers to the terminal connected to the neutral point of the network.
3.2.5 Corresponding terminals
Terminals marked with the same letters or corresponding symbols for different windings of a transformer. 3.3 Windings
3-3.1 Windings
A group of turns that constitute an electrical circuit corresponding to a certain voltage value marked on the transformer. Note: For three-phase transformers, it refers to the combination of three phase groups. 3.3.2 Tapped winding
A winding whose effective number of turns can be changed step by step. 3.3.3 Phase winding
A group of wires that form a three-phase winding. Note: The term "phase group" should not be confused with the assembly of all wires on a core. 3.3.4 High-voltage winding
The winding with the highest rated voltage:
3.3.5 Low-voltage winding
The winding with the lowest rated voltage.
Note that for step-up transformers, the lower rated voltage group may have a higher insulation level. 3.3.6 Intermediate winding
A winding in a multi-group transformer whose rated voltage is between the highest rated voltage and the lowest rated voltage. 3.3-7 Auxiliary group
A winding that only carries a load that is much smaller than the rated capacity of the transformer. 3.3.B Stable winding
In a transformer with star-star connection or star-zigzag connection, an auxiliary delta-connected winding specially designed to reduce the zero-sequence impedance of the star-connected winding. Note: This winding is called a stable winding only when the two phases are not connected to the external circuit. 3.3.9 Common winding
The common part of the relevant windings of the autotransformer. 3-3.10 Series winding
GB 1094.11996
For autotransformers, it refers to the winding connected in series with the line, and for booster transformers, it refers to the winding connected in series with the line. 3.3.11 Excitation winding
In a booster transformer, it refers to the winding that supplies electrical energy to the series winding. 3.4 Rated values
3.4.1 Rated values
Specified values ​​of certain parameters are used to limit the operation of the transformer under the conditions specified in this standard and serve as the test basis and the guaranteed value of the manufacturer.
3.4.2 Rated parameters
The values ​​are used to determine certain parameters (current, voltage, etc.) of the rated values. Note: ① For transformers with taps,Rated parameters refer to the main tapping, unless otherwise specified. Corresponding parameters with similar meanings to other specific tappings are called tapping parameters.
③Unless otherwise specified, voltages and currents are expressed in terms of their RMS values. 3.4.3 Rated voltage of winding (U,)
The voltage induced when no-load is specified by the voltage applied between the terminals of a tapped winding in the main tapping or between the terminals of a winding without a tap. For three-phase windings, it refers to the voltage between the line terminals. Note: ①When the voltage applied to one of the windings is the rated value, all windings appear at their respective rated voltage values ​​at the same time when no-load is applied. ②For single-phase transformers to be connected to form a three-phase group, the rated voltage is expressed by dividing the phase-to-phase voltage by 3. For example, iU,=500/ 3 kV.
③When the connected windings of a three-phase step-up transformer are designed as an open circuit system, their rated voltages can be expressed by connecting them in star connection. 3.4.4 Rated voltage ratio
The ratio of the rated voltage of one winding to the rated voltage of another winding with a lower or equal rated voltage. 3.4.5 Rated frequency
The operating frequency based on which the transformer is designed. 3.4.6 Rated capacity (S,)
It is the specified value of the apparent power of a certain winding, and together with the rated voltage of the winding, it determines its rated current. Note: ①The two windings of a double-cable transformer have the same rated capacity, which is the rated capacity of this transformer. ②For multi-group transformers, half of the arithmetic sum of the rated capacities of all its windings (independent windings not connected by autocoupling) is used to roughly estimate its actual size for comparison with double-winding transformers. 3.4.7 Rated current (I.)
The current flowing through the line terminals of the winding derived from the rated capacity (S.) and rated voltage (U.) of the transformer. Note: ① For a three-phase transformer group, the rated current is expressed as: J.-S./ 3U. (A). ② For a single-phase transformer winding to be connected in a delta connection to form a three-phase group, the rated current is expressed as the line current divided by 3 (e.g.: 1. = 500/3 A).
3.5 Taps
3.5.1 Taps
In a transformer with tapped windings, each tap connection of the winding indicates that the tapped winding has a certain value of effective turns, and also indicates that the tapped winding has a certain value of turns ratio with any other winding with unchanged values. Note: Among all the taps, one is the main tap, and the other taps are expressed in their relationship with the main tap by their respective tapping factors relative to the main tap. 3.5.2 Main tapping
The tapping corresponding to the rated parameters.
3.5-3 The tapping factor (corresponding to the specified tapping) refers to Us/U, (tap factor) or 100Ua/U, (tap factor expressed as a percentage). Where: U,—Rated voltage of the winding;
GE 1094.1--1996
U—The induced voltage between the terminals of the winding at the specified tapping position under no-load when the rated voltage is applied without a tapping cable.
Note: This definition does not apply to the series connection of step-up transformers. 3.5.4: Positive tapping
The tapping factor is greater than 1.
3.5.5 Negative tapping
The tapping factor is less than 1.
3.5.6 Tap level
The difference in tap factors between two adjacent taps expressed in percentage. 3-5.7 Tap range
The range of tap factors expressed in percentage compared to 100. Note: If the tap range changes from 100+ to 100+, then this tap range is +4%. If it is +1, then it is +3.5.8 Tap voltage ratio (of a pair of windings) When the tapped winding is a high voltage line group, its tap voltage ratio is equal to the rated voltage ratio multiplied by the tap factor of the winding. When the tapped winding is a low voltage winding, its tap voltage ratio is equal to the rated voltage ratio divided by the tap factor of the winding. Note: By definition, although the rated voltage ratio is at least equal to 1, when the rated voltage ratio is close to 1, the tap voltage ratio of some taps may be less than 1. 3.5.9 Tap working capacity
Specified values ​​of certain parameters of other taps other than the main tap, similar to the rated parameters 3.5.1D Tap parameter
Parameter indicating the tap working capacity of a certain tap (other than the main tap). Note: Any winding in the transformer (not just the winding with taps) has tap parameters. The tap parameters are!
Tap voltage (similar to the rated voltage) a.
b. Tap capacity (similar to the rated capacity), tap current (similar to the rated current). .
3.5.11 Full capacity tap
Tap capacity is equal to the rated capacity.
3.5.12 Reduced capacity tap
Tap capacity is lower than the rated capacity. 3.5.13 On-load tap changer
A device suitable for changing the connection position of a winding tap when the transformer is excited or loaded. 3.5.14 Tap voltage regulation 13
3.5.14.1 Constant flux voltage regulation (CFVV)
When changing from one tap to another, the tap voltage of the untapped winding is constant. The tap voltages of the tapped winding are proportional to the tap factor.
3.5.14.2 Variable flux voltage regulation (VFVV)
When changing from one tap to another, the tap voltages of the tapped winding are constant. The tap voltages of the untapped winding are inversely proportional to the tap factor.
3.5.14.3 Mixed voltage regulation (CbVV)
In practical applications, especially when the transformer tapping range is large, constant flux is used in different parts of the entire tapping range. Note:
11 The three terms in Article 3.5.14 are the definitions in Article 5.2 of 1EC 76-1. Because it is not appropriate to repeat the definitions in the main text, they are moved to this article. GB 1094.1—1996
Voltage regulation and variable flux voltage regulation form a combined voltage regulation (i.e. mixed voltage regulation). In mixed voltage regulation, the tap at the turning point is called the maximum voltage tap. 3.6 Losses and no-load current
Losses and no-load current values ​​refer to the main tap (except when other taps are specified) 3.6.1 No-load loss
The active power absorbed when the rated voltage (tap voltage) at the rated frequency is applied to the terminals of one winding and the other windings are open. 3.6.2 No-load current
The root mean square value of the current flowing through the winding terminals when the rated voltage (tap voltage) at the rated frequency is applied to the terminals of one winding and the other windings are open.
Note: ① For three-phase transformers, it is the arithmetic mean of the current flowing through the three-phase terminals. ② It is usually expressed as a percentage of the rated current of the group. For multi-phase transformers, it is based on the winding with the largest rated capacity. 3.6.3 Load losses
The active power absorbed at rated frequency and reference temperature (see 10.1) in a pair of windings when the rated current (tap current) flows through the line terminals of one winding and the other winding is short-circuited. At this time, the other winding (if any) should be open-circuited. Note: For two-winding transformers, there is only one pair of windings and one load loss value. For multi-winding transformers, there are multiple load loss values ​​corresponding to multiple pairs of windings. The total load loss value of the whole transformer corresponds to a specified winding load combination. It cannot be directly measured in the test. When the rated capacity of the two windings in the winding combination is different, the load loss is based on the rated current in the pair with the smaller rated capacity, and the reference capacity should be indicated.
3.6.4 Total losses
The sum of the empty losses and the load losses.
Note: Auxiliary equipment losses are not included in the total losses and should be stated separately. 3.7 Short-circuit impedance and voltage drop
3.7.1 Short-circuit impedance (of a pair of windings)
The equivalent series impedance 7R + this (Q) between the terminals of a winding in a pair of windings at rated frequency and reference temperature. When determining this value, the terminals of the other winding are short-circuited and the other windings (if any) are open-circuited. For three-phase transformers, it is expressed as the impedance of each phase (equivalent star connection). For transformers with tapped windings, it refers to the specified tap position. If not otherwise specified, it refers to the main tap. Note: This parameter can be expressed as a relative value without quantity, that is, it is expressed as a fraction of the parameter impedance Zr of the same winding in the pair of windings. If expressed as a percentage, then: z=100 2/Z
In the formula, U-2 and Zer belong to the voltage (rated voltage or tap voltage) S,——-rated capacity reference value.
(The above formula is applicable to both three-phase transformers and single-phase transformers) This relative value is also equal to the ratio of the voltage applied to produce the corresponding rated voltage (or tapping current) in the short-circuit test to the rated voltage (or tapping voltage). This voltage is called the short-circuit voltage of the pair of windings. It is usually expressed as a percentage. 3.7.2 Voltage drop or voltage rise under specified load conditions The arithmetic difference between the no-load voltage of a winding and the voltage produced by the same winding under specified load and power factor, when the voltage applied to the other winding should be the rated voltage (main tap) or the tap voltage (other taps). This difference is usually expressed as a percentage of the no-load voltage of the winding. Note: For multi-winding transformers, this voltage drop or voltage rise is not only related to the load and power factor of the winding, but also to the load and power factor of other windings.
3.7.3 Zero-sequence impedance (three-phase winding)
The impedance expressed in ohms per phase between the line terminals connected together and the neutral point terminal of a three-phase star or zigzag connected winding at rated frequency.
GB 1094. 1—1996
Note: ① Since the zero-sequence impedance also depends on the connection method and load of other windings, the sequence impedance can have several values. ② Zero-sequence impedance can vary with current and temperature, especially in transformers without any delta-connected windings. ③ Zero-sequence impedance can also be expressed as a relative value in the same way as positive-sequence short-circuit impedance. 3.8 Temperature rise
The difference between the temperature of the considered part and the temperature of the external cooling medium. 3.9 Insulation
The relevant terms for transformer insulation shall be in accordance with the provisions of GB1094.3. 3.10 Connection
3.10.1 Star connection (Y-connection)
One end of each phase winding of a three-phase transformer or one end of three windings with the same rated voltage of a single-phase transformer forming a three-phase group is connected to a common point (neutral point), and the other end is connected to the corresponding line terminal. 3.10.2 Delta connection (D-connection)
The three phase windings of a three-phase transformer or the three windings with the same rated voltage of a single-phase transformer forming a three-phase group are connected in series to form a closed circuit.
3.10.3 Open Delta Connection
The three phase windings of a three-phase transformer or the three windings of a single-phase transformer forming a three-phase group are connected in series, but one angle of the triangle is not closed.
3.10.4 Zigzag Connection (Z-Connection)
One end of each phase winding of a three-phase transformer is connected to a common point (neutral point), and each phase winding consists of two parts, and the phase of the induced voltage in each part is different.
Note: Usually the two parts have the same number of turns. 3.10.5 Open Winding
The phase windings that are not connected to each other inside a three-phase transformer. 3.10.6 Phase Rotation of Three-Phase Windings
The angular difference between the voltage phasors between the neutral point (real or assumed) of the low voltage (medium voltage) winding and the high voltage winding and the corresponding line terminal when positive sequence voltage is applied to the high voltage terminals marked in alphabetical or numerical order, these phasors are assumed to rotate in the counterclockwise direction. Note: Based on the phase quantity of the high voltage winding, the phase displacement of any other windings is expressed by the traditional clock sequence. That is, when the phase disc of the high voltage winding is at "12", the phase discs of other windings are expressed by clock sequence (the larger the clock sequence, the more delayed the phase). 3.10.7 Connection group number
A group of letters and clock sequences are used to indicate the connection method of the high voltage, medium voltage (if any) and low voltage windings: and a general number indicating the phase displacement relationship between the medium voltage and low voltage windings and the high voltage winding. 3.11 Test classification
3.11.1 Routine test
Tests that every transformer must undergo.
3.11.2 Type test
On a stage Tests performed on representative transformers to demonstrate that the transformers represented also meet the specified requirements (except routine tests).
Note: If the transformers are exactly the same in terms of rating and structure, one of them is considered to be representative. If the rating or other characteristics of a transformer are not much different from those of the other transformers, the type test performed on it can also be considered valid. The difference should be specified by the manufacturer and the user. 3-11.3 Special tests
Tests performed in accordance with the agreement between the manufacturer and the user, in addition to type tests and routine tests. 3. 12
Meteorological data related to galaxies
3.12. Average temperature in January
GB 1094.11996
The multi-year statistical value of half the sum of the average of the highest daily temperature and the average of the lowest daily temperature in a certain month. 3.12.2 Annual average temperature
1/12 of the sum of the average temperatures of each month in the whole year. 4 Rated value
4.1 Rated capacity
The rated capacity of each winding of the transformer should be specified and marked on the nameplate. The rated capacity refers to the continuous load. It is the basis of load loss and temperature rise, and it is also the guarantee of the manufacturer. If different apparent powers are specified for different conditions (for example, for different cooling methods), the highest value is taken as the rated capacity. The double-winding transformer has only one rated capacity value, and the rated capacity values ​​of the two windings are the same. In particular, when the voltage is applied to one of the soft windings of the transformer and a certain current flows through the terminals of only one of the two soft windings, the transformer bears the rated capacity corresponding to the pair of windings. Under normal use conditions (see Article 1.2), the transformer should be able to continuously deliver the rated capacity. The rated capacity of the transformer is not equal to the rated capacity. Because of the voltage drop (or voltage rise) inside the transformer, the voltage between the secondary terminals is not equal to the rated voltage. The allowable value of the voltage drop (related to the load power factor) is given in the technical specifications of the rated voltage and tapping range.
4.2 Load cycle
In the inquiry and contract, in addition to specifying the continuous load rated capacity, a temporary load cycle can also be specified. Under this load condition, the transformer should be able to operate normally under the conditions specified in GB1094.2. Note: The temporary load cycle is especially used as the basis for the design and guarantee of the temporary emergency load of large plastic power transformers. When there are no above provisions, the transformer load capacity shall comply with the provisions of GB/T15164 and relevant standards. The bushings, tap changers and other auxiliary equipment used in the transformer shall not limit the load capacity of the transformer. Note: These instructions are not applicable to transformers for special purposes. Some transformers do not need to exceed the rated load capacity. Special requirements should be specified for other types of transformers.
4.3 Priority number of rated capacity
The rated capacity value shall be selected from the R10 sequence in GB321 (100, 125, 160, 200, 250, 315, 400, 500, 630800, 1000, etc.).
4.4 When operating at a voltage higher than the rated voltage and (or) with unstable frequency, under load conditions (load capacity, power factor and corresponding line-to-line operating voltage), the method for determining the rated voltage and tap range shall be in accordance with GB/T 13499.
Within the specified value of the equipment's highest voltage (.), when the ratio of voltage to frequency exceeds the ratio of rated voltage to rated frequency, but does not exceed 5% of "overexcitation, the transformer should be able to operate continuously without damage. For special use cases (for example, the active power of the transformer can flow in any direction), at rated power, the user can specify that the transformer operates at a voltage higher than 105% of the rated voltage, but not more than 110% of the rated voltage. If there is no special requirement for the relationship between current and voltage, when the current is K (0≤K≤1) times the rated current, the voltage U is limited according to the following formula. U(%)=110-5K2
Adoption instructions:
1] [EC 76.1 does not have this paragraph (4.4 paragraph 3), which is added according to the operating conditions of my country. GB 1094. 1--1996
5 Technical requirements for transformers with one tapped winding This chapter applies to transformers with only one tapped winding. For multi-winding transformers, it only applies to combinations where only one of a pair of windings is a tapped winding. For autotransformers, when the tap is located at the grounded neutral point, the effective number of turns of the two windings is changing simultaneously. For such transformers, the requirements for the details of the tapping should be in accordance with the agreement, but as far as possible in accordance with the relevant provisions of this chapter. 5.1 Marking of the tapping range||tt| |The main tap should be located at the midpoint of the tap range (unless otherwise specified), and other taps are marked with tap factors. The variation range of the tap position number and voltage ratio is simplified by the deviation between the tap factor percentage and 10. Example: A transformer with a rated voltage of 220kV with tapped windings has 17 taps, arranged symmetrically, and its mark is: (220±8)×1.25%/35kV
If the specified tap range is not symmetrical with the rated voltage, its mark is: (220±)×1.25%/35kV
: This simplified symbol only indicates the tapping arrangement with tapping system, and does not reflect the actual change of the voltage applied to the winding in the line. For details, see Articles 5.2 and 5.3.
The data of each tapping parameter should be marked on the nameplate (see Chapter 7). Subject to the restrictions of tapping voltage and tapping current, some taps can be "reduced capacity tapping". The boundary tapping where these restrictions appear is called "maximum voltage tapping" or "maximum current tapping" (see Figure 1). 5.2 Standard types of tapping parameter changes and maximum voltage tapping The simplified symbols of the tapping range and tap position number indicate the range of changes in the transformer transformation ratio, but cannot fully represent the specified value of the tapping parameter. Some data must also be added, such as: the tapping capacity, tapping voltage and tapping current of each tap can be listed in a table, or the type of voltage regulation and the limit range of "full capacity tapping" can be described in words. The tap voltage regulation should choose constant flux voltage regulation (CFVV), variable flux voltage regulation (VFVV) and mixed voltage regulation (CbVV). See Figure 1 for tap voltage regulation.
Figure 1a: Constant flux voltage regulation (CFVV) indicates the selection point of the maximum current tap. Figure 1b: Variable flux voltage regulation (VFVV) indicates the selection point of the maximum current tap. Figure 1c: Mixed voltage regulation (CbVV) indicates the position of the tapping of the turning point (located in the positive tapping range), which is consistent with the maximum voltage tap U and the maximum current tap I Corresponding (IB is a constant, and after exceeding the turning point, it no longer rises). The figure also indicates the selection point of the maximum current tap (within the CFVV area).
The tap voltage regulation shall comply with the following provisions: a. Constant flux voltage regulation is applicable to each tap whose tap factor is lower than the maximum voltage tap factor, b. Variable flux voltage regulation is applicable to each tap whose tap factor is higher than the maximum voltage tap factor. 5.3 Tap capacity
Except as follows, all taps shall be full capacity taps. In independent winding transformers with a rated capacity of 2500kVA and below and a tap range within ±5%, the tap current in all negative tapped windings is equal to the rated current, which indicates that its main tap is the maximum current tap". In transformers with a tap range exceeding ±5%, it may be necessary to specify limits on their tap voltage or tap current, otherwise they will significantly exceed the rated value. When these limits are specified, certain taps are "reduced capacity taps". When the tapping factor is not equal to 1, for full-capacity tapping, the tapping current may exceed the rated current. This situation occurs in the negative tapping under constant flux voltage regulation (see Figure 1a) for tapped windings; in the positive tapping under variable flux (see Figure 1b) for non-tapped windings. To avoid the above situation, it is possible to specify the maximum current tapping, from which the tapping current of the winding should be set to a constant. This also means that the remaining tappings until the limit tapping are reduced capacity tappings (see Figures 1a, 1b, and 1c). Under mixed voltage regulation, the "maximum voltage tap" (i.e. the turning point between constant flux voltage regulation and variable flux voltage regulation) is also the "maximum current tap" (unless otherwise specified). The current of the untapped winding remains constant until the limit positive tap (see Figure 1c). 100+
Tap factor
Figure 1 Constant flux voltage regulation
In the figure: UA, IA—
Tap factor
Figure 1b Variable flux voltage regulation
Figure 1 Tap voltage regulation
Tap voltage and tap current in tapped winding, U,Is—Tap voltage and tap current in non-tapped winding; SaB——Tap capacity;
1—The range of maximum voltage tapping, maximum current tapping and reduced capacity tapping in full capacity tapping within the entire tapping range, 2
5.4 Requirements for tapping when inquiring and ordering
The following requirements are necessary for transformer design.
Which winding is the tapped winding:
Figure 1 Mixed voltage regulation
Tap factor||t t||The number of tap positions and tap levels (or tap range and number of tap positions). The tap range should be symmetrically distributed according to the main tap, and the number of tap levels should be equal. If otherwise specified, the special provisions should be clearly stated in the contract or bid! Type of voltage regulation. If mixed voltage regulation is specified, the turning point (maximum voltage tap) should be indicated; whether the maximum current limit (reduced capacity tap) needs to be specified, and if necessary, the tap position should be indicated. d.
Note: This can be replaced by a table on the nameplate. Text description of item a and item d (see Appendix B). For the above provisions, the user can clearly state all requirements in the inquiry. Alternatively, propose active power The load conditions of reactive power and reactive power (clearly indicating the power flow direction) and the corresponding load voltage. The limit values ​​of the voltage ratio at full capacity and reduced capacity should be indicated (see the "six-parameter method" of GB/T13499). The manufacturer should select the tapped winding and specify the rated parameters and tapping parameters according to the requirements of the contract or tender. 5.5 Short-circuit impedance
GB1094.1-1996
1. The short-circuit impedance of a pair of windings is specified according to the main tapping (unless otherwise specified). When the tapping range exceeds ±5%, the short-circuit impedance values ​​of the two extreme taps should also be given. During the short-circuit impedance test (see Article 10.4) , the three impedance values ​​of the main tap and the two extreme taps should be measured. When impedance values ​​are given for several taps, especially when a pair of groups has different rated capacitance, it is recommended to express the impedance value in ohms per phase (based on any winding of the pair) instead of percentage, which may cause confusion due to different reference values. When expressed in percentage, the corresponding reference capacity and reference voltage values ​​should be clearly indicated. Note: When the user selects the impedance value, he will avoid conflicting requirements: voltage drop limitation and overcurrent limitation during system faults; the best economic design for consumption reduction requires short-circuit impedance within a certain range. If it is operated in parallel with an existing transformer, matching impedance must also be considered (see GB/T13499). If the inquiry specifies not only the short-circuit impedance value of the main tap, but also the variation of short-circuit impedance within the range of other taps, this means that there are major restrictions on the design (mutual configuration between the windings), so these detailed provisions should be proposed. When making requirements for short-circuit impedance in the inquiry, leave appropriate freedom for the design, that is, give the acceptable upper and lower limits within the entire tapping range, which can be expressed through drawing and tabulation. There should be enough difference between the two limits to allow at least their middle value plus the positive and negative deviations specified in Chapter 9. (See the example given in Appendix C. The manufacturer shall select the short-circuit impedance value of the main tap and the limit tap, and ensure that it is between the upper and lower limits. According to the measured value in Chapter 9, it is allowed to be different from the design value, but it should not fall outside the upper and lower limits (no allowable difference). 5.6 Load loss and temperature rise || tt || Load loss and temperature rise shall comply with the following provisions: a. For transformers with a tap range of ±5% and a rated capacity not exceeding 2500kVA, the guarantee of load loss and temperature rise refers only to the main tap. The temperature rise test is carried out on the main tap. b. For transformers with a tap range exceeding ±5% or a rated capacity greater than 2500kVA, in addition to the main tap, the load loss of other taps that need to be guaranteed by the manufacturer should also be indicated. The load loss is based on the corresponding tap current. The temperature rise limit should apply to all taps at the corresponding tap capacity, tap voltage and tap current). When temperature rise is used as a type test, it is only carried out on one tap and should be carried out on the "maximum current tap" (usually the tap with the largest load loss) (unless otherwise agreed). The test capacity for determining the oil temperature rise should be the total loss of the selected tap, and the tap current of the tap is the reference current for determining the oil temperature rise of the winding. For temperature rise tests and regulations, see GB 1091.2. The purpose of the temperature rise test is to verify whether the transformer cooling system can dissipate the heat generated by the maximum total loss, and under all taps, the temperature rise of any winding above the ambient temperature should not exceed the specified temperature rise limit. For the second purpose, it is required to select the "maximum current tap", but in order to ensure the maximum oil temperature rise, the total loss to be applied should be the loss of the tap with the maximum total loss (even if this tap is not the tap selected by the test engine). For details, see Article 5.2 of GB1094.2: 6 Connection and connection group number of three-phase transformers When the three phase windings of a three-phase transformer or the three single-phase transformers that form a three-phase group are connected in star, triangle or zigzag shape, the capital letter Y should be used for the high-voltage winding.D or Z indicates that the medium voltage or low voltage winding is represented by the lowercase form of the same letter d or 2. For star or zigzag connections with neutral point lead-out, YN (yn) or ZN (zn) should be used to indicate that the open winding is not connected inside the three-phase transformer and both ends of each phase winding are led out, it should be represented as (high voltage winding) or (medium voltage or low voltage winding) respectively.
Note that the various groups of single-phase transformers are also represented by this number. For a pair of self-connected windings, the low voltage group is represented by auto or a (such as YNeuto or YNa or YNaO, ZNalI). The letter symbols of the high voltage, medium voltage, and low voltage group connection of the transformer should be marked in the order of decreasing rated voltage. After the connection letters of the medium voltage and low voltage windings, the phase shift clock sequence number is marked immediately (see Figure 2). When there is a stable winding (a delta-connected cable group not connected to an external load), it should be indicated by "+d\" after the letter of the negative winding. Dym11
GB 1094:1-1996
YNyods
Figure 2 Clock sequence number representation (three examples)
When the winding connection is variable (such as: Shen-parallel or YD), both connections together with the corresponding rated voltage should be marked. Example:
220(110)/10.5kv
110/11(6.35)kV
YN(YN)d1)
YNyo(di11)
The nameplate should have complete instructions (see 7.2 e). For general connection groups and connection diagrams, see Appendix D. 12
When there are terminal markings and built-in current transformers, the terminal markings and wiring diagrams can be marked on the nameplate together with the text instructions specified in Chapter 7.
The transformer winding connection diagram follows the traditional marking method, with the high-voltage winding located on the top and the low-voltage winding located on the bottom. The diagram should indicate the direction of the induced voltage.
The high-voltage winding phasor diagram should be with phase A pointing to 12 0 o'clock as the benchmark, the phase base of the low-voltage winding phase a is determined according to the induced voltage relationship. The rotation direction of the phasor diagram rotates counterclockwise, and the phase sequence is A-B-C. Example 1:
Distribution transformer, high-voltage winding 10kV, triangle connection low-voltage winding 400V, star connection, and neutral point lead-out low-voltage winding lags high-voltage winding 330°.
Its label is: Dyn11.
Example 2:
Three-winding transformer, high-voltage winding 121kV. Star connection, with neutral point lead-out; medium-voltage winding 38.5kV, star connection, with neutral point lead-out, and in phase with the high-voltage winding: low-voltage cable group 6. 6 kV, triangle connection, 150° behind. Its label is: YNynod5.
Example 3:
15°/22kV, auto-connected windings are connected in star connection; and with a third winding, three single-phase autotransformers form a three-phase group Y3/3
triangle connection, and lag the high-voltage winding by 330°. Its label is, YNautod1l or YNad1l.
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