Some standard content:
National Standard of the People's Republic of China
On-load tap-changers
On-load tap-changers
This standard is equivalent to the international electrotechnical standard IEC214 "On-load tap-changers" (1987 edition). Part I General
1·Scope
GB10230-—88
This standard applies to on-load tap-changers and their motor-driven mechanisms for power transformers. It is mainly applicable to tap-changers immersed in transformer oil in accordance with GB2536, but can also be used for gas-insulated tap-changers under very suitable conditions. Note: This standard considers synthetic insulating liquids to be a kind of oil. Synthetic insulating liquids can only be used in tap-changers when the design of the tap-changer is compatible with synthetic insulating liquids.
This standard does not include tap-changers installed in transformers for railway traction vehicles. Conditions of use
Ambient temperature of tap-changers
Unless the orderer has more stringent requirements, the tap-changer should be able to operate within the temperature range specified in Table 1. Table 1 Ambient temperature of the tap changer
Ambient temperature of the tap changer
Note: ① The environment of the tap changer refers to the medium that closely surrounds the entire tap changer, that is, if the tap changer is installed in a separate external container and installed outside the transformer tank, its environment is "air"; if the entire tap changer is installed in the transformer main tank instead of in a separate external container, its environment is oil (i.e. the oil in the transformer tank). ② The value of 100℃ quoted above is based on the maximum atmospheric temperature of 40℃ specified in GB1094.1~1094.5 "Power Transformer". ③ The use of on-load tap changers below -25℃ should be negotiated between the orderer and the manufacturer. b.bzxz.net
Ambient temperature of the motor mechanism
Unless the orderer has more stringent requirements, the motor mechanism should be suitable for operation at any atmospheric temperature from -25℃ to 55℃. Note: The use of the motor mechanism below -25℃ should be negotiated between the orderer and the manufacturer. Overload conditions
The tap changer that complies with this standard is suitable for the load that the transformer can withstand under various oil temperatures specified in the standard "Load Guidelines for Oil-Immersed Transformers".
3 Data required for bidding and ordering
The data required for bidding and ordering shall be in accordance with the provisions of the agreement between the two parties. Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on December 12, 1988 and implemented on January 1, 1990
GB10230-88
Part II Definition
4 Definition of on-load tap changer (excluding electric mechanism) 4.1 On-load tap changer
A device that can be operated when the transformer is excited or loaded to change the tap connection position of the coil. It usually consists of a diverter switch (see Article 4.3 of this standard) with transition impedance (see Article 4.6 of this standard) and a tap selector (see Article 4.2 of this standard) with or without a change-over selector (see Article 4.5 of this standard). The entire switch is operated by a drive mechanism (see Article 4.7 of this standard). In some types of tap changers, the functions of the diverter switch and the tap selector are combined into a selector switch (see Article 4.4 of this standard).
Note: This standard only involves on-load tap changers, which are referred to as tap changers below. 4.2 Tap selector
A device that can carry but cannot connect or disconnect current, used in conjunction with the diverter switch to select the tap connection position. 4.3 Diverter switch
A device used in conjunction with the tap selector to carry, connect and disconnect the current in the selected circuit. Note: A spring-operated diverter switch includes an independent energy storage device for operating the switch. 4.4 Selector switch
A device that has the functions of a tap selector and a transfer switch and can carry, connect and disconnect current (i.e., a combined switch). 4.5 Changeover selector
This device is designed to carry current but cannot connect or disconnect current. It is used in conjunction with a tap selector or a selector switch, and when it is moved from one extreme position to another, the contacts of the tap selector or the selector switch and the tap connected to the contacts can be used more than once.
4.5.1 Coarse selector
A changeover selector that connects the tap winding to the coarse adjustment winding or to the main winding. 4.5.2 Polarity selector
A changeover selector that connects one end or the other end of the tap winding to the main winding. 4.6 Transition impedance
A resistor or reactor consisting of one or more units, bridged between the tap in use and the tap to be used, in order to achieve the purpose of transferring the load current from one tap to another without interruption or significant change. At the same time, the circulating current is limited during the period when the two taps are bridged.
4.7 Driving mechanism
A device that drives the tap changer.
Note: This mechanism may include an energy storage control mechanism. 4.8 Contact group
It is essentially a moving and static contact pair or a combination of moving and static contact pairs that act simultaneously. 4.9 Contacts of transfer switch and selector switch
4.9.1 Main contact
A contact group that carries the through current, is connected to the transformer winding without passing through the transition impedance, and cannot connect or disconnect any current.
4.9.2 Main on-off contact
A contact group connected to the transformer winding without passing through a transition impedance and capable of making and breaking current. 4.9.3 Transition contact
A contact group connected to the transformer winding through a series transition impedance and capable of making and breaking current. GB10230-88
Note: If it is a tap changer with reactance transition, this contact group is mostly used to carry the through current in the normal tap position. 4.10 Circulating current
In tap change, when two taps are "bridged", the part of the current generated by the voltage difference between the taps and flowing through the transition impedance.
4.11 Breaking current
When tap change, the current that each main on-off contact group or transition contact group contained in the diverter switch or selector switch is expected to break.
4.12 Recovery voltage
The working voltage that appears between the moving and static contacts of each main on-off contact group or transition contact group of the diverter switch or selector switch after the breaking current is cut off.
4.13 Tap change (operation)
The entire process of the through current starting from one tap of the winding and completely transferring to the adjacent tap. 4.14 Operation cycle
The action of the tap changer changing from one extreme position to another extreme position and then returning to the starting position. Insulation level
The withstand voltage value of the impulse and power frequency test between the ground, multi-phase phases and other parts that need insulation. 5 Rated through current I
The current that flows to the external circuit through the tap changer, which can be transferred from one tap to another by the tap changer under the relevant step voltage, and can be continuously carried by the tap changer and meet the requirements of this standard. Note: For the relationship between the rated through current and the relevant step voltage, see Article 6.2 of this standard. 4.17 Maximum rated through-current I
Rated through-current used for contact temperature rise test (Article 8.1 of this standard) and working load switching test (Article 8.2.1 of this standard).
Rated step voltage U
For each rated through-current, the maximum permissible voltage between the terminals of the tapchanger connected to adjacent taps of the transformer. Note: The rated step voltage given for a certain rated through-current is called "related rated step voltage". 9 Maximum rated step voltage U
The maximum value of the rated step voltage designed for the tapchanger. D Rated frequency
The AC frequency designed for the tapchanger.
4.21 Number of tap positions of the tapchanger
4.21.1 Number of inherent tap positions
The maximum number of tap positions that a tapchanger can use in half an operating cycle in design. 4.21.2 Number of working tap positions
The number of tap positions of the tapchanger in the transformer in half an operating cycle. Note: ① In the description of Articles 4.21.1 and 4.21.2 of this standard, the positive and negative values of related numbers are generally expressed, such as ±11 position; but it is more convenient to use continuous numbers for indication on the product, such as marking the ±11 position as the 23 position. The same is true for the position indication of the motor. ② The term "tap position number" used in transformers usually refers to the working tap position number of the tap changer. 4.22 Type test
A test conducted on a tapchanger or on some components of a tapchanger, or on a series of tapchangers or components all based on the same design to prove whether they comply with the standard. Note: A series of tapchangers are tapchangers based on the same design and with the same performance (insulation level to ground, insulation level between phases of multiple phases, number of levels and transition impedance values are excluded).
4.23 Factory test
GB1023088
A test conducted on each finished product of a tapchanger that has passed the type test in order to determine that the tapchanger has no manufacturing defects. 5 Definition of motor-drive mechanism
5.1 Motor-drive mechanism
A drive mechanism composed of the drive mechanism specified in Article 4.7 of this standard combined with the motor and control circuit. 5.2 Step-by-step control
An electrical and mechanical device that can stop the motor-drive mechanism after a tap change is completed, regardless of the way the command is issued. 5.3 Tap position indicator
An electrical and (or) mechanical device that can indicate the tap position of the tap changer. 5.4 Indication of tap change in progress
A device that indicates that the electric mechanism is running. 5.5 Limit device
5.5.1 Limit switch
A device consisting of an electrical switch and an operating mechanism that can prevent the operation of the tap changer from exceeding any limit position, but allows the tap changer in the limit position to rotate in the reverse direction. 5.5.2 Mechanical limit stop device
A mechanical device that mechanically prevents the operation of the tap changer from exceeding any limit position, but allows the tap changer in the limit position to rotate in the reverse direction.
5.6 Parallel control device
An electrical control device that can move all the tap-changers of a number of on-load tap-changing transformers operating in parallel to a specified position, while avoiding uncoordinated operation of the motor mechanisms.
Note: For single-phase transformers forming a three-phase group, such a device is also required when each single-phase tap-changer has its own motor mechanism. 5.7 Emergency release device
An electrical and (or) mechanical device that can stop the motor mechanism in an emergency. Whenever a situation occurs in which the tap-changer can no longer be operated, it is used to stop the motor mechanism so that special treatment can be carried out. 5.8 Overcurrent blocking device
An electrical device that can prevent or interrupt the operation of the motor mechanism during the period when the overcurrent flowing through the transformer winding exceeds a predetermined value. Note: For a transfer switch operated by a spring energy storage system, as long as the release mechanism has been actuated, interrupting the operation of the motor mechanism will not prevent the operation of the transfer switch.
5.9 Restarting device
A mechanical and/or electrical device that can restart the motor drive and complete a tap change operation that has been started after the interrupted operating power supply is restored.
5.10 Counter
A device that indicates the number of completed tap changes. 5.11 Manual operation of the motor drive
A mechanical device that can be turned by hand to operate the tap changer and can lock the operation of the motor at the same time. 5.12
Motor drive box
Motor drive base box.
Part III Technical Requirements for On-load Tap Changers (excluding Electric Mechanisms) 6 Ratings
6.1 Rated Characteristics
The rated characteristics of a tap changer are:
- Rated through-current;
- Maximum rated through-current;
- Rated step voltage:
- Maximum rated step voltage;
Rated frequency:
- Rated insulation level.
GB10230-88
6.2 Relationship between rated through-current and rated step voltage Within the maximum rated through-current range of the tap changer, the rated through-current and the corresponding rated step voltage values of the tap changer may have several given combinations. A rated step voltage value corresponding to a specified value of the rated through-current is called the relevant rated step voltage. 7 Design and Structure
7.1 Oil Chamber of Diverter Switch and Selector Switch
The oil chamber of a diverter switch and selector switch with a separate oil chamber shall be sealed. Note: If the transformer oil is monitored by chromatographic analysis, an oil conservator should be provided for the oil compartment of the diverter switch or selector switch during the design of the transformer structure. This oil conservator is neither oil- nor air-conducted with the transformer oil conservator. 7.2 Oil level gauge
The diverter switch and selector switch oil compartment with fixed expansion volume, or the dedicated oil conservator for the diverter switch and selector switch oil compartment should be equipped with an oil level gauge.
Note: The dedicated oil conservator for the diverter switch or selector switch, which is separate from the diverter switch or selector switch, is provided by the transformer manufacturer. 7.3 Overpressure protection device
To prevent overpressure, one or more of the following protection devices can be used. The tap changer for transformers with gas relays shall have at least one of the relay protection devices specified in Articles 7.3.1 and 7.3.2 of this standard. 7.3.1 Oil flow control relay
It is installed in the connecting pipe between the top of the tap changer and the oil conservator, and operates at a predetermined oil flow rate and can cause the transformer to be disconnected. 7.3.2 Overpressure relay
It operates when the pressure in the oil chamber of the diverter switch or selector switch exceeds a predetermined value and can cause the transformer to be cut off. 7.3.3 Pressure relief device
It opens when the predetermined pressure is exceeded to protect the oil chamber of the diverter switch or selector switch. 7.4 Overvoltage protection of tap changer
For tap changers equipped with overvoltage limiting devices, the protection characteristics should be fully explained by the manufacturer of the tap changer. When a spark gap is used, it must be ensured that the spark can be automatically extinguished after discharge. 8 Type test
The following type tests should be carried out on the final trial samples of the relevant tap changer or on some equivalent components. The so-called equivalent component refers to the component used for testing, which, in terms of its relevant test conditions and test results, has been proven to be able to replace the test carried out on the entire tap changer.
- Contact temperature rise test (Article 8.1 of this standard);- Switching test (Article 8.2 of this standard);- Short-circuit current test (Article 8.3 of this standard);- Transition impedance test (Article 8.4 of this standard);- Mechanical test (Article 8.5 of this standard);- Insulation test (Article 8.6 of this standard);
- Pressure and vacuum test (Article 8.7 of this standard). 8.1 Contact temperature rise test
GB10230—88
Various types of contacts that continuously carry current during operation shall be tested with 1.2 times the maximum rated through current. When the contact temperature reaches a stable state, the temperature rise of the surrounding medium shall not exceed the specified value in Table 2. Meeting this condition proves that the tap changer has the overload capacity as stated in Chapter 2 of this standard. Table 2 Contact temperature rise limit
Contact material
Steel with silver plating
Other materials
In air
Temperature rise limit
In oil
When the surrounding medium is oil, the test should be carried out at room temperature, and the temperature of the surrounding medium should be measured at a distance not less than 25mm below the contact.
Use a thermocouple or other appropriate means, placed on the surface of the contact and as close as possible to the actual contact point, to measure the temperature. When the temperature difference between the contact and the surrounding medium does not exceed 1K per hour for 2 consecutive hours, the temperature is considered to have reached stability. Note: During the test, the cutting surface and insulation of the current-carrying leads connected to the tap changer or some components should be explained. 8.2 Switching test
The switching test includes the working load switching test and the breaking capacity test. The test shall simulate the most severe conditions produced by the tap changer under the design rating. When it comes to the transition switching of the reactor, the most severe conditions shall be negotiated by the manufacturer and the ordering parties. In the case of asymmetric pennant cycle [see Table A1 in Appendix A (Supplement) of this standard], it is assumed that there is no reverse power flow during operation. In Appendix A (Supplement), the most severe conditions of most contact circuits of the resistance tap changer are pointed out. The switching test can be carried out independently with the diverter switch or the selector switch, but it must be proved that the independent test does not affect the operating conditions of the contacts. If the diverter switch or the selector switch has several contact groups, which operate according to a certain procedure, it is not allowed to test each contact group separately from other contact groups. Unless it can be proved that the switching operating conditions of any group of contacts are not affected by the switching operation of other contact groups. For the resistance tap changer, if it is necessary for the structure of the tap changer or the test circuit, the resistor can be placed outside the equipment, and it can also have a larger thermal capacity than the resistor used in the product. Unless otherwise specified. The value and type of transition impedance shall be stated. The oil and contacts in the oil-immersed tap-changer shall not be replaced in each test. In the case of a three-phase switch, only the contacts of one phase shall be tested. If a tap-changer has several combinations of rated through-current and rated step voltage, the breaking capacity test shall be carried out at least under two combinations of the maximum rated through-current 1 and its related step voltage U, and the maximum rated step voltage U and its related rated through-current I. The curve point X of the average current between the two end points of the curve can be easily obtained by interpolation as follows: tl(U.) = Vul× Uul.
The test circuit shall be such that the breaking current, recovery voltage and the product of these numbers of the contacts of the tested tap-changer vary within a range of -5% to +10% compared with the values calculated for the tap-changer at the equivalent through-current and the related rated step voltage according to the corresponding switching cycle (see Table A1).
8-2.1 Working load switching test
This test shall be carried out in accordance with one of the following provisions. After the test, the contacts shall be checked for burnout and the results shall confirm that the tap-changer is suitable for use. Note: The number of operations that the manufacturer declares the contacts for making and breaking current can achieve without replacing the contacts at rated through-current and relevant step voltages, can be demonstrated by the test results. 8.2.1.1 Working load switching test at rated step voltage GB10230-88
The contacts of the diverter and selector switches shall be subjected to a normal working load switching test equivalent to 50,000 times at not less than the maximum rated through-current and relevant step voltage.
The selector switch shall be tested in not more than 8 tap change positions (excluding the end positions) to make it close to the use state. If the tap-changer is designed with a change-over selector, these positions shall be arranged with the change-over selector as the center. During the test, the oscillograms shall be taken at a certain interval and compared. No significant changes that endanger the operating characteristics of the tap-changer shall be found. At the beginning of the test, 20 oscillograms shall be taken, and 20 oscillograms shall be taken after each 12,500 operations, for a total of 100 oscillograms.
Note: It is usually sufficient to compare the oscillograms taken at the beginning and end of the test. 8.2.1.2 Working load switching test at reduced rated step voltage Working load switching test can be carried out at reduced rated step voltage, but the following conditions must be met: a. The tap changer with new contacts shall be immersed in clean transformer oil and 100 operations shall be carried out at the maximum rated through current and the relevant rated step voltage. Each operation shall be recorded oscillographically. In the case of s, the working load shall be carried out according to item d. b. In all oscillograms taken in item a, if the arcing time does not exceed the number of operations of the switching test, it shall be 50,000. c. In all the oscillograms taken in item a, if the arcing time exceeds the length s, the number of operations of the working load switching 2
test performed in item d should be increased by the following increment: 100×50000
s. Here S is equal to the total number of half cycles of arc current that appear in 100 operations in item a. The working load switching test of 50000 times plus the number of operations that may be increased from item c of this clause shall be carried out with a current not less than the maximum rated through-current and at a reduced step voltage. This reduced voltage shall make the switched current not less than the current that occurs when operating at the rated step voltage, and no current interception occurs. In order to obtain the specified test conditions, the transition impedance shall be appropriately changed. e. After the test in item d of this clause, 100 operations shall be carried out at the maximum rated through-current and the relevant rated step voltage without replacing the contacts and oil, and each operation shall be recorded oscillographically. These oscillograms shall be compared with the series of oscillograms taken in the test of item a of this clause. There shall be no changes in the characteristics of the tap-changer that may endanger the operation of the equipment. The test procedure specified above is intended to make the contact erosion essentially the same as the contact erosion when 50,000 operations are performed at the maximum rated through-current and the relevant rated step voltage. 8.2.1.3 Working load switching test of selector switch The test may be carried out in accordance with the provisions of 8.2.1.1 or 8.2.1.2 of this standard. When the selector switch is designed for asymmetrical flag cycle switching, the most severe switching tasks of the main make and break contacts occur at full load and no load (see Table A1 of Appendix A (Supplement)) because the load current and the circulating current and their combined recovery voltage are vectorially subtractive. In use, most transformers do not often operate at full load, so the arc erosion of the contacts is always reduced. Therefore, the test should be carried out for 25,000 operations at full load and no load to make it closest to the use conditions. 8.2.2 The breaking capacity test
shall be carried out for 40 operations at twice the maximum rated through-current and the relevant rated step voltage. In the oscillogram taken for each operation, the arcing time shall not show any phenomenon that endangers the operation of the equipment. The thermal capacity and ohmic value of the transition impedance used for the breaking capacity test shall be the same as those used in operation. If this is not possible, the impedance used in operation shall be tested separately in accordance with Article 8.4.1 of this standard, but only one conversion operation is carried out with twice the maximum rated through-current. 8.2.3 Simulation test circuit
Tests belonging to Articles 8.2.1.1, 8.2.1.2 and 8.2.2 of this standard may be completed using a simulation test circuit whose test conditions have been proven to be equivalent to the actual ones. Two available test circuits are listed in Appendix C (Supplement). 8.3 Short-circuit current test
GB10230—88
All continuously current-carrying contacts of different designs shall be subjected to short-circuit current tests, each lasting 2 (10%) s. For oil-immersed tap changers, the test shall be carried out in transformer oil. Unless otherwise specified, for three-phase tap changers, only one phase of the contact shall be tested. The initial peak current of the three tests shall reach 2.5 (5%) times the root mean square value of the short-circuit test current. Between several tests, the contacts shall not be moved.
When there is no synchronous closing device and it is impossible to meet the above requirements, the test may be carried out in the following way: increase the root mean square value of the short-circuit test current so that the peak current can be reached in the three tests and the test duration shall be reduced. When this method is used, the duration of each test is as follows: t>s
Where: n-
The multiple of the test current increase.
The value of the short-circuit test current applied shall comply with the provisions in Figure 1:20
The open-circuit voltage of the short-circuit current test circuit in Figure 1 expressed as a multiple of the maximum rated through-current shall be at least 50V. After the test, the contacts shall not have any damage that prevents them from continuing to operate correctly at the rated current. Other parts carrying the current shall not show any signs of permanent mechanical deformation.
8.4 Transition impedance test
8.4.1 Transition resistor
The transition resistor shall be tested at the relevant rated step voltage with 1.5 times the maximum rated through-current to determine whether it meets the overload requirements of Chapter 2, Item c of this standard.
The resistor shall be installed in the tap-changer as used on the product. The resistor shall be loaded by the operation of the tap-changer. The number of tap-changing operations shall be equivalent to half of an operating cycle (see Article 4.14 of this standard). The test shall be carried out by the motor-drive mechanism operating uninterruptedly at normal speed. The resistor temperature is recorded and determined at the last tap-change operation.At 5 times the maximum rated through-current, the temperature rise of the resistor to the surrounding medium shall not exceed 400°C for tap-changers in air environments and 350°C for tap-changers in oil environments. However, the temperature of the resistors and some of their adjacent parts shall be limited to values that do not affect the performance of the assembly. If it is not practical to determine the temperature of the transition resistor in the above manner, the method in Appendix B (Supplement) may be used. Note: If the rated through-current or the relevant rated step voltage is different from the maximum rated through-current and the relevant rated step voltage, it is allowed to calculate the thermal rating of the resistor from the type test results.
8.4.2 Transition Reactor
GB10230-88
The test of the transition reactor should usually be carried out in accordance with the specifications of the transformer for which the tap-changer is intended to be used. Note: Measures should be taken in the design of the transition reactor to avoid high inrush currents during switching. 8.5 Mechanical tests
8.5.1 Mechanical life test
When the oil-immersed tap-changer is tested, it shall be installed, filled with oil or immersed in an oil-filled test tank and operated as in normal use. The test shall be carried out for 500,000 tap-change operations with the contacts de-energized and with the full range of tapping. At least 50,000 tap-change operations shall be tested on the change-over selector. For tap-changers with air as the environment, this test may be carried out at room temperature. For tap-changers with oil as the environment, half of the test shall be carried out at a temperature not less than 75°C; the other half at a lower temperature, e.g. during heating or cooling, where daily temperature cycle variations are permitted.
At the beginning and end of the mechanical life test, 10 unloaded oscillograms of the diverter switch and tap selector or selector switch and installed change-over selector shall be taken. When these oscillograms are compared, there shall be no significant differences. Regardless of whether the environment of the tap-changer is air or oil, the diverter switch or selector switch shall be subjected to 100 operations at -25°C, each operation being recorded by an oscilloscope. Comparison of these oscillograms with those obtained in the previous paragraph shall show that the tap-changer is suitable for low temperature use.
During the test, there shall be no failure or excessive wear of the mechanical parts. During the test, normal maintenance of the tap-changer in accordance with the manufacturer's manual is permitted. Mechanical life tests may be conducted separately on the diverter switch, tap selector or other components of the tap-changer, but each case shall be operated in exactly the same manner as in its normal use. 8.5.2 Sequence test
The sequence test shall be conducted over the entire operating cycle. During the test, the tap-changer shall be installed as used, and the oil-immersed type shall be placed in clean transformer oil. The test shall record the exact time sequence of the tap selector, change-over selector and diverter switch or selector switch actions with the working voltage of the recording device applied to the contacts. 8.5.3 Pressure and vacuum test
After the mechanical life test, the oil chamber and bushing of the tap changer shall be subjected to appropriate tests to check their tightness. The pressure and vacuum tolerance values shall be stated by the manufacturer. 8.6 Insulation test
8.6.1 General
The insulation requirements of the tap changer depend on the transformer winding connected to it. The transformer manufacturer shall not only be responsible for selecting a tap changer with an appropriate insulation level, but also for the insulation level of the connection between the tap changer and the transformer winding.
The oil-immersed tap changer shall be filled with clean transformer oil or immersed in a test oil tank filled with clean transformer oil before the tests specified in Article 8.6.3 of this standard can be carried out.
8.6.2 Classification
In order to select the appropriate voltage test, the tap changer shall be classified according to Table 3. Table 3 Classification of tap changers
8.6.3 Nature of test
For neutral point of winding
For positions other than neutral point of winding
The insulation level of the tap changer shall be verified by insulation tests carried out at the following insulation distances: a. To earth;
Between phases of multiple phases:
GB10230-88
Between the first and last contacts of the tap selector or selector switch and the change-over selector installed; c.
d Between any two adjacent contacts of the tap selector or selector switch, or any other contacts related to the line connection of the tap changer contacts:
Between the contacts of the diverter switch in the final open position. e.
8.6.4 Test voltage
Category 1
For test a, the test voltage shall fully comply with the provisions of Table 4. For tests b, c, d and e, the corresponding lightning impulse withstand value and short-time power frequency voltage withstand value shall be stated by the manufacturer of the tap-changer. Category
For tests a and b, the test voltage shall fully comply with the provisions in Table 4. For tests c, d and e, the corresponding lightning impulse voltage withstand value and short-time power frequency voltage withstand value shall be stated by the manufacturer of the tap-changer. Table 4 Insulation level
Maximum working voltage
Rated lightning impulse withstand voltage (peak value)
550(480)
Note: The values in brackets are only applicable to old products. 8.6.5 General requirements for applied test voltage
620(530)
Imin power frequency withstand voltage
230(200)
Rated switching impulse withstand voltage
(peak value)
For voltage test, the tap-changer shall be assembled, arranged and dried as in use, but it is not necessary to include the leads. The test may be carried out on separate components as long as it can be shown that the pressure is applied under the same insulation conditions. For the first and second tests of the first category tap-changer, the live parts of each phase shall be short-circuited and, where appropriate, connected to the power supply or ground.
For tap-changers with external insulation to earth, its external insulation parts shall be tested according to the relevant test items in GB4109 "Technical Conditions for High Voltage Bushings".
8.6.6 Power frequency voltage test
Use single-phase AC voltage and conduct the test at the required withstand voltage value in accordance with the relevant provisions in Chapter 3 of GB311.3 "High voltage test technology part 2 test procedure". The duration of each test is 1 minute. 8.6.7 Lightning impulse voltage test
The full wave and chopped standard wave of the lightning impulse voltage test shall comply with the relevant provisions in Chapter 4 of GB311.3 and high voltage test technology, but the voltage over-order coefficient of the chopped waveform is allowed to be less than 0.25. Each test shall be conducted according to the specified withstand voltage value. Three tests shall be conducted at positive polarity voltage and negative polarity voltage respectively.
8.6.8 Operation impulse test
GB10230-88
This test is applicable to the Class I tap-changer at any line end of a transformer of 300kV and above, and the test shall be conducted between the live part and the grounded part of the tap-changer. The test circuit connection method shall be explained by the tap changer manufacturer. The impulse waveform and test sequence shall comply with the provisions of Articles 14.1 and 14.2 of GB1094.3. The impulse voltage shall be selected from Table 4. 8.6.9 Partial discharge measurement
For a type I tap changer installed on an autotransformer with U.=252kV or above and operating at a maximum operating voltage of U\126kV or above, partial discharge measurement shall be carried out between its live parts and grounded parts. Note: 1) U. See the definition in Article 3.9.1 of GB1094.1. The test connection method shall be explained by the tap changer manufacturer. Close the switch at the level of No. U., and the time sequence of increasing the voltage to apply the test voltage shall be as shown in Figure 2. During the test, when the voltage is not higher than Uz, it lasts for 5 minutes, then the voltage is increased to U, and it lasts for 5 seconds, and then the voltage is immediately and continuously reduced to U., and it lasts for 30 minutes, and then the voltage is reduced to below No. U, and the switch is closed.
Test duration is independent of test frequency. U
Figure 2 Time sequence for applying test voltage
Partial discharge should be monitored during the entire process of applying test voltage. The "apparent charge" q shall not be higher than the specified value. U. should be 3U.//3=U.
U. It should be 1.5U./√3, at which time q is not greater than 50pC. Note: 9 is a provisional value and needs to be revised based on experience. The observation and evaluation of partial discharge should be as follows (see GB1094 for detailed information).Appendix A of 3): The background noise level should be recorded before and after the application of the test voltage. The background noise level should be less than half of the specified limit of the apparent charge. When the voltage rises to level U, and then falls from U, the discharge start voltage and extinction voltage should be recorded. A reading should be taken and recorded during the first stage of voltage U,. When the voltage U, is applied for a short time, the value of the partial discharge must be recorded, but it is not used for judgment. During the whole process of the second stage of voltage U, the level of partial discharge should be continuously observed and its readings should be recorded or recorded at regular intervals.
During the above observation process, if the test voltage does not produce a sudden drop and the continuous level of apparent charge remains below the specified limit and there is no obvious and steady increase trend during the last 29 minutes of the 30 minutes of application of U. voltage, the test is considered to be qualified. If the apparent charge reading exceeds the specified limit and returns to below this level after a significant period of time, the test can be continued without interruption until an acceptable reading is obtained during the 30 minutes. Accidental high pulses should be ignored.
Note: The above test process is equivalent to the partial discharge measurement specified in Article 11.4 of GB1094.3. b. The type " tap changer does not need partial discharge measurement. 8.7 Pressure and vacuum test
Unless otherwise specified by the orderer, the oil chamber of the diverter switch and selector switch should be able to withstand the pressure and vacuum test of 6×10\Pa. The test is carried out before the mechanical life test. The test should be carried out before and after the vacuum drying treatment. The vacuum dried oil chamber should be
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.