JB/T 7070.3-2002 Test Guidelines for Voltage Regulators Part 3: Test Guidelines for Magnetic Voltage Regulators
Some standard content:
ICS29.180
Machinery Industry Standard of the People's Republic of China
JB/T7070.3—2002
Replaces JB/T7070.3-1993
Test guide for voltage regulator
Part 3: Test guide for magnetic control voltage regulator
Test guide for voltage regulatorPart 3: Test guide for magnetic control voltage regulator2002-07-16Promulgated
Implementation on 2002-12-01
Promulgated by the State Economic and Trade Commission of the People's Republic of ChinaForeword
Normative references
Terms and definitions.
General requirements for tests
Test procedures.
Routine tests.
Type tests,
Special tests.
Appearance inspection
Test purpose.
Inspection method,
Sealing performance test
Overview,
Static oil column method
Static air pressure method,
Insulating oil test.
Insulation characteristic test
Overview,
Test preparation,
Test steps and requirements
Result judgment,
Winding resistance measurement
Circuit mutation method measurement
Bridge method measurement
Resistance conversion,
Power frequency withstand voltage test,
Test requirements Request
Test voltage determination
Other regulations.
Induction withstand voltage test
Test method,
13 No-load test.
Test steps and methods
JB/T7070.3—2002
JB/T7070.3—2002
13.3 Selection of line loss value
13.4 No-load loss correction...
Single-phase test and correction
14 Load test.
14.1 Overview
Impedance voltage and load loss measurement||tt ||Impedance voltage and load loss correction
15 Oil tank mechanical strength test,
Output voltage asymmetry determination,
Measurement method
Output voltage range test,
Voltage regulation characteristic curve test
Overview,
Test requirements.
Other requirements.
Short-circuit characteristic curve test
Test requirements,
Other requirements.
Load external characteristic curve test
Overview,
Test requirements,
Other requirements.
Temperature rise test,|| tt||Environmental conditions
Test requirements..
Determination of voltage regulation time constant
Measurement requirements.
Other requirements
23 Test of over-nameplate operating capacity (overload capacity), 24 Sound level measurement
Power frequency withstand voltage test circuit diagram
Induction withstand voltage test circuit diagram
No-load test and load test circuit diagram
Schematic diagram of three-column core..
Voltage regulation characteristic curve test circuit diagram,
Figure 6 Wiring diagram for voltage regulation time constant determination Table 1 Measurement location of insulation resistance,
Air density P. Relationship with factor P: Table 3
Ratio of hysteresis loss, eddy current loss and total no-load loss 000..0000006...
JB/T7070.3—2002
This standard is revised on the basis of JB/T7070.3-1993 "Guidelines for voltage regulator test Part 3: Guidelines for magnetic voltage regulator test". This standard replaces JB/T7070.31993.
Compared with JB/T7070.3-1993, this standard has the following major changes: The editorial revision is made according to the writing format specified in GB/T1.1-2000 "Guidelines for Standardization Work Part 1: Structure and Numbering Rules of Standards";
The referenced standards are adjusted according to the actual situation of this standard: - The test items in the test procedure are divided by category, and adjusted according to JB/T10092-2002 "Magnetic Voltage Regulator": The "Main Symbols" chapter is cancelled, and the explanation of the main symbols is decomposed into the references of formulas in each chapter; - Six chapters of "Terms and Definitions", "General Requirements for Tests", "Appearance Inspection", "Mechanical Strength of Oil Tanks", "Output Voltage Range Test" and "Over Nameplate Operation Capacity (Overload Capacity) Test" are added. This standard is proposed by the China Machinery Industry Federation. This standard is under the jurisdiction of the National Technical Committee for Transformer Standardization. The drafting units of this standard are: Shenyang Transformer Research Institute, Zhangjiagang Special Transformer Factory. The main drafters of this standard are: Lu Wanlie, Shao Zuyi, Pan Yuxiang. This standard was first issued in 1993.
1 Scope
Guidelines for voltage regulator testing
Part 3: Guidelines for magnetic voltage regulator testing
JB/T7070.3—2002
This standard specifies the methods and test procedures for routine tests, type tests and special tests of oil-immersed magnetic voltage regulators and dry-type magnetic voltage regulators.
This standard applies to magnetic voltage regulators with voltage levels of 10kV and below and rated capacities of 5kVA to 1000kVA for continuous operation. Tests of special types of magnetic voltage regulators can also be carried out in accordance with this standard. 2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version shall apply to this standard. GB311.1-1997 Insulation coordination of high voltage transmission and transformation equipment (neqEC60071-1:1993) GB/T311.6-1983 High voltage test technology Part 5 Measurement of ball gap (neqIEC60052:1960) GB/T507-1986 Dielectric strength determination method of insulating oil (neqIEC60156) GB/T64511999 Technical parameters and requirements for three-phase oil-immersed power transformers GB7595 Quality standard for transformer oil in operation Guidelines for oil-immersed power transformer loads (idtIEC60354:1991) GB/T15164-1994 GB/T16927.1-1997 High voltage test technology Part 5: General test requirements (eqvEC6 0060-1:1989) GB/T17211—1998 Guidelines for loading of dry-type power transformers (eqvEC60905:1987) GB/T19001-1994
Quality system - Quality assurance model for design, development, production, installation and service (idtISO9001:1994) JB/T501—1991
Guidelines for testing power transformers
General technical requirements for voltage regulators
JB/T8749—1998
JB/T10092-—2000
3 Terms and definitions
Magnetic voltage regulator
The terms and definitions in JB/T8749—1998 and JB/T10092-—2000 apply to this standard. 4 General requirements for testing
The test shall be carried out at any ambient temperature between 10℃ and 40℃. 4.1
4.2 The relative humidity shall be below 90%.
The temperature of the test piece shall not differ significantly from the ambient temperature. The test site must have separate working grounding and protective grounding. 4.4
Unless otherwise agreed between the manufacturer and the user, all tests shall be carried out at the manufacturer. 4.6 During the test, all external components and devices that may affect the operation of the magnetic voltage regulator shall be installed in the specified position. Except for the insulation test, all performance tests shall be based on the rated conditions (unless otherwise specified). 4.7
4.8 The test measurement system shall ensure accuracy in accordance with the requirements of GB/T19001-1994. 49 There shall be no gas or medium that seriously affects the insulation of the magnetic voltage regulator in the test site. 1
JB/T7070.32002
4.10 There shall be no severe vibration in the test site.
4.11 When the test measurement data needs to be corrected to the reference temperature, the reference temperature of the magnetic voltage regulator is: 75℃ for oil-immersed type; 20K for dry type according to the winding temperature rise limit under the corresponding insulation heat resistance grade. 4.12 The magnetic voltage regulators that need to undergo type tests can be randomly selected from the batch of products, and the number of units selected is generally not less than two. After the test, if one unit fails in one item, it should be returned for retesting. If it still fails in the retesting, the batch of products is considered unqualified and can only be produced after the defects are eliminated and the test is qualified.
5 Test procedures
The tests specified in this standard are divided into routine tests, type tests and special tests. The following items are sorted as the specified test sequence. 5.1
Routine tests
Before each product leaves the factory, routine tests should be carried out: Appearance inspection:
Sealing performance test:
Insulating oil test:
Insulation characteristics test:
Winding resistance measurement:
Power frequency withstand voltage test:
Induction withstand voltage test;
No-load test:
Load test.
5.2 Type test
Type test shall be carried out for new products or when there are major changes in the structure, process and materials of the product: oil tank mechanical strength test;
output voltage asymmetry measurement:
output voltage range test:
voltage regulation characteristic curve test:
short circuit characteristic curve test:
load external characteristic curve test;
temperature rise test.
5.3 Special test
Special test shall be carried out to verify the special performance of the product or when requirements are put forward in the agreement. Voltage regulation time constant measurement:
over-nameplate operating capacity (overload capacity) test: b)
sound level measurement.
6 Appearance inspection
6.1 Test purpose
Inspect the appearance of the test product for obvious defects. 6.2 Inspection method
In advance, conduct a comprehensive inspection of the raw materials, parts, and purchased parts of the test product. Their performance should comply with the provisions of the corresponding standards or technical conditions. Conduct a comprehensive inspection of the whole machine and accessories of the test product. The lead wires and terminals, wiring terminals, shell protection level, oil protection and oil temperature measuring devices, and oil tank surface quality of the test product should be correct and intact and meet the requirements of their own quality and the matching of the whole machine. 2
7 Sealing performance test
7.1 Overview
JB/T7070.32002
The sealing performance test should be carried out on the assembled magnetic voltage regulator (with oil storage cabinet). The removable radiator and oil storage cabinet can also be tested for sealing performance separately. Before the sealing test pressure is released, all welds and sealing surfaces of the oil tank should be fully and carefully inspected, and no oil leakage should occur.
The test can be carried out using either method 7.2 or 7.3. 7.2 Static oil column method
When the static oil column method is used for testing, a vertical oil filling hanging tank can be added above the magnetic voltage regulator box cover or oil storage cabinet if necessary, and then the static pressure generated by the oil level in the hanging tank or oil storage cabinet can be used to make the magnetic voltage regulator oil tank reach the pressure value and duration specified in GB/T6451-1999. 7.3 Static air pressure method
For the test product without oil storage cabinet, the static air pressure method should be used for sealing test at normal oil level. When the static air pressure method is used for testing, a pressure gauge is connected to the box cover of the magnetic voltage regulator or the oil storage cabinet, and a valve should be installed outside the vent plug of the oil storage cabinet. Dry air is filled through the valve to apply static air pressure to the oil tank. The applied pressure and duration should comply with the provisions of GB/T6451-1999.
8 Insulating oil test
The transformer oil breakdown voltage test is carried out in accordance with GB/T507-1986. The test requirements and qualified judgment shall comply with the provisions of GB7595--1987. 9 Insulation characteristic test
9.1 Overview
The insulation characteristic test is an important reference for evaluating the insulation performance of the magnetic voltage regulator, conducting high-voltage tests and operating. The insulation characteristic test of the magnetic voltage regulator mainly measures the insulation resistance Ro (resistance at 60s) and the absorption ratio R6/Ris (i.e. the ratio of insulation resistance 60s to 15s). The measurement locations of the insulation resistance are shown in Table 1. Table 1 Measurement location of insulation resistance
9.2 Test preparation
Measurement location
Low voltage winding
High voltage winding
Control winding
Grounding location
High voltage winding, control winding and shell
Low voltage winding, control winding and shell
High voltage winding, low voltage winding and shell
For 10kV magnetic voltage regulator, the insulation resistance Rso should be measured. When measuring, a 2500V high resistance meter with an indication limit of no less than 10MQ should be used, and its accuracy should be higher than 1.5%. When measuring, first put the high resistance meter in a horizontal position, and without connecting the test product, turn on the power supply of the high resistance meter, and its indication should be "80": When the test connection cable is connected, there should be no obvious difference in the indication of the high resistance meter. When using the megohmmeter, the E end must be grounded, the L end must be connected to the phase line, and the G end must be shielded. 9.3 Test steps and requirements
The measurement should be carried out one by one according to the measurement parts listed in Table 1, and the winding temperature should be between 10℃ and 40℃. Use hand crank to make the speed of the megohmmeter reach about 120r/min, and then connect the line measurement after the megohmmeter is at the rated voltage, and start timing at the same time. After each test, the phase line should be disconnected first to avoid the reverse impact of the megohmmeter due to the discharge of the measured winding after power failure. Before the test, the measured winding should be fully discharged to eliminate the influence of residual charge on the measurement results. When a certain part is tested, the measured winding should be discharged again, and then another measured winding should be connected. When the air humidity is high, causing serious leakage on the outer insulation surface, the outer insulation surface should be shielded during the measurement. 3
JB/T7070.32002
The conversion of resistance values at different temperatures shall be in accordance with the provisions of GB/T6451-1999 9.4 Result judgment
Whether the insulation resistance is qualified shall be judged in accordance with the provisions of JB/T10092-2000. 10 Winding resistance measurement
10.1 Overview
The determination of winding resistance is to check the welding quality of the internal wire and lead wire of the coil and the coil, whether the specifications of the wire used in the coil meet the design, and whether the contact of the current-carrying parts such as the lead copper bar and the casing is good. The resistance of each winding of the single-phase magnetic voltage regulator should be measured at the wire end of each winding; the three-phase magnetic voltage regulator should measure its line resistance. When measuring the winding resistance, a power source such as a type A dry battery, a storage battery or a constant current source can be used. The power supply should have sufficient capacity to avoid measurement errors caused by changes in the internal resistance of the power supply due to excessive discharge current or prolonged time during the measurement process. 10.2 Determination by circuit mutation method
During the measurement, the test current or the sensitivity of the zeroing instrument should be adjusted so that when the measured resistance changes by 1/1000, the measuring instrument or bridge galvanometer has a clear indication.
In order to shorten the time, a battery can be used for power supply. When using a battery for power supply, it is recommended to connect an additional resistor of 4 to 6 times the measured resistance in series in the power supply circuit. During the charging process of the winding, the additional resistor is short-circuited to make the current rise faster. When the test current reaches the expected value or slightly exceeds it, the short-circuit switch is disconnected. This measurement method is called the circuit mutation method. When measuring the winding resistance, the winding temperature must be accurately recorded. For dry-type magnetic voltage regulators, the winding temperature should be the average temperature of no less than 3 points on the winding surface. For oil-immersed magnetic voltage regulators, after the body is immersed in oil for 3 hours (without excitation), it is considered that the average temperature of the winding is the same as that of the oil; the average temperature of the oil should be the average of the top temperature of the oil (the thermometer is placed in the oil thermometer seat on the top of the box) and the inlet and outlet temperatures of the radiator. When the difference between the test product temperature and the ambient temperature is less than 3°C, the top oil temperature can be used as the winding temperature. For products with forced oil circulation, the cold resistance (winding resistance and temperature) before the temperature rise test should be measured when the oil pump is working. 10.3 Bridge method determination
During the test, the resistance can be measured using a bridge with an accuracy of 0.2 or 0.5 depending on the capacity of the product. The cold and hot resistance of the temperature rise test should be measured using a bridge with an accuracy higher than 0.5 and a galvanometer with a current constant less than 10~. When using the bridge method, the standard 10.1 and measure according to the instructions for use of the bridge. During the measurement, the galvanometer should be turned on after the current stabilizes. After the bridge reaches equilibrium, record the reading and turn on the galvanometer. If possible, the test current should be reduced to the minimum before cutting off the power supply.
A double-arm bridge should be used to measure the measured resistance of 112 and below. For the measured resistance above 11Q, either a double-kidney bridge or a single-arm bridge can be used. When using a single-arm bridge for measurement, the influence of the connection resistance should be considered. When using a double-arm bridge for measurement, the current connection and the potential connection must be connected to the measured line end respectively. The current connection should have a large enough cross-sectional area. During the measurement, the current change should not be caused by the heating of the connection: the resistance of the potential connection should be as small as possible. Even if it is connected, the bridge arm resistance should not change significantly and can be ignored. When a standard resistor is used for the double-arm bridge, the connection between the standard resistor and the measured resistor should have a large enough cross-sectional area, and its connection should not affect the accuracy of the bridge.
10.4 Conversion of resistance
The unbalance rate of three-phase resistance is calculated with the difference between the maximum and minimum values of the three-phase resistance as the numerator and the average value of the three-phase resistance as the denominator.
When the unbalance rate of the three-phase line resistance is less than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection
Where:
Rxs—phase resistance of three phases, unit is 2;—line resistance of three phases, unit is 2.
When the three-phase resistance unbalance rate is greater than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection (ay:bzicx)
Where:
R, =Rs +Ra -Rs
Rg =Rg +Rg -Ra
R. = Rs +Ra -Ra
R, =(Rea -R)-
Rab×Re
Rea-R,
Rea×R
Rg=(Rab -R,)-4
Rab -Rp
Rab×Ra
R=(RxR)-4
R, =Ra +Re +Ra
Rab, Rre, Rea line resistance between each phase, unit is 2; phase resistance of each phase, unit is 2;
Ra, Rp, R.
R—average value of phase resistance, unit is 2.
When converting winding resistance at different temperatures, calculate according to the following formula: R=K,×R
Where:
R. —Resistance when temperature is ℃, unit is Q; —Resistance when temperature is t℃, unit is Q: R,
—Resistance temperature coefficient:
—Temperature coefficient, copper winding is 235, aluminum winding is 225: Reference temperature, unit is ℃:
JB/T7070.3—2002
JB/T7070.3—2002
9—Actual temperature, unit is ℃.
11 Power frequency withstand voltage test
11.1 Overview
The power frequency withstand voltage test is used to assess the withstand voltage strength of the main insulation of the magnetic voltage regulator. The test circuit is shown in Figure 1. R
TR——Voltage regulator: T—Test transformer: TA-—Current transformer: A-—Ammeter: V, V2—Voltmeter V-Peak voltage meter. R--Discharge resistor: R.—Protection resistor: R2 Damping resistor: C--—Capacitor voltage divider main capacitor C—Voltage divider capacitor: C—Test product: Q—Ball gap (or electrostatic voltmeter. For products with voltage levels below 35kV Figure 1 Power frequency withstand voltage test circuit diagram
112 Test requirements
During the power frequency withstand voltage test, the core and shell of the tested product must be reliably grounded. And the oil level indication of the test product must be high In the cable bushing or bushing riser. Before the test, the bushing connected to the main oil and the low-voltage terminal board, hand hole cover, riser and other raised parts should be deflated until the oil is visible.
All terminals of the tested winding of the test product should be connected to the live wire, and all terminals of the non-tested winding should be grounded. The frequency of the power frequency withstand voltage test should not be less than 80% of the rated frequency, preferably between 45Hz and 55Hz. Its voltage waveform should be close to sine (the two half-waves are exactly the same, and the ratio of the peak value to the root mean square value is equal to 2±0.07), or the root mean square value of each harmonic is not greater than 5% of the root mean square value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should not be less than 0.1A. For products with larger capacity, the steady-state short-circuit current should not be less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and the voltage should be kept constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the root mean square value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
The test voltage is recommended to be measured by a capacitive voltage divider calibrated by the metrology department in combination with a peak voltage meter, or it can be measured using a spherical gap. When using a spherical gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The spherical gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: the spherical gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the spherical gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the spherical gap is discharged, the voltage boost speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, take the average value of 3 discharge voltages. Each discharge gap is not less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%:
e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: 6
f) The distance between the ball gap cannot exceed 0.5 times the ball diameter: JB/T7070.3—2002
The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density g)
should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and the voltage (U, or U) closest to the neutral voltage U of U, in V: U,--test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequency of the test voltage should not be less than 100Hz (preferably between 150Hz and 400Hz). The duration is calculated as follows: t=120×blood
Where:
t—test time, in seconds:
f.--rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration should be not less than 15s: 130% of the rated input voltage can also be applied for a duration of 3min. 1--Rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration shall be not less than 15s: 130% rated input voltage may also be applied for a duration of 3min.--Rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration shall be not less than 15s: 130% rated input voltage may also be applied for a duration of 3min.4 Resistance conversion
The unbalance rate of three-phase resistance is calculated with the difference between the maximum and minimum values of the three-phase resistance as the numerator and the average value of the three-phase resistance as the denominator.
When the unbalance rate of the three-phase line resistance is less than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection
Where:
Rxs—phase resistance of three phases, unit is 2;—line resistance of three phases, unit is 2.
When the three-phase resistance unbalance rate is greater than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection (ay:bzicx)
Where:
R, =Rs +Ra -Rs
Rg =Rg +Rg -Ra
R. = Rs +Ra -Ra
R, =(Rea -R)-
Rab×Re
Rea-R,
Rea×R
Rg=(Rab -R,)-4
Rab -Rp
Rab×Ra
R=(RxR)-4
R, =Ra +Re +Ra
Rab, Rre, Rea line resistance between each phase, unit is 2; phase resistance of each phase, unit is 2;
Ra, Rp, R.
R—average value of phase resistance, unit is 2.
When converting winding resistance at different temperatures, calculate according to the following formula: R=K,×R
Where:
R. —Resistance when temperature is ℃, unit is Q; —Resistance when temperature is t℃, unit is Q: R,
—Resistance temperature coefficient:
—Temperature coefficient, copper winding is 235, aluminum winding is 225: Reference temperature, unit is ℃:
JB/T7070.3—2002
JB/T7070.3—2002
9—Actual temperature, unit is ℃.
11 Power frequency withstand voltage test
11.1 Overview
The power frequency withstand voltage test is used to assess the withstand voltage strength of the main insulation of the magnetic voltage regulator. The test circuit is shown in Figure 1. R
TR——Voltage regulator: T—Test transformer: TA-—Current transformer: A-—Ammeter: V, V2—Voltmeter V-Peak voltage meter. R--Discharge resistor: R.—Protection resistor: R2 Damping resistor: C--—Capacitor voltage divider main capacitor C—Voltage divider capacitor: C—Test product: Q—Ball gap (or electrostatic voltmeter. For products with voltage levels below 35kV Figure 1 Power frequency withstand voltage test circuit diagram
112 Test requirements
During the power frequency withstand voltage test, the core and shell of the tested product must be reliably grounded. And the oil level indication of the test product must be high In the cable bushing or bushing riser. Before the test, the bushing connected to the main oil and the low-voltage terminal board, hand hole cover, riser and other raised parts should be deflated until the oil is visible.
All terminals of the tested winding of the test product should be connected to the live wire, and all terminals of the non-tested winding should be grounded. The frequency of the power frequency withstand voltage test should not be less than 80% of the rated frequency, preferably between 45Hz and 55Hz. Its voltage waveform should be close to sine (the two half-waves are exactly the same, and the ratio of the peak value to the root mean square value is equal to 2±0.07), or the root mean square value of each harmonic is not greater than 5% of the root mean square value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should not be less than 0.1A. For products with larger capacity, the steady-state short-circuit current should not be less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and the voltage should be maintained constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the root mean square value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
It is recommended to use a capacitive voltage divider calibrated by the metrology department to measure the test voltage with a peak voltage meter, or it can be measured with a spherical gap. When using a spherical gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The spherical gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: the spherical gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the spherical gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the spherical gap is discharged, the voltage boost speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, take the average value of 3 discharge voltages. Each discharge gap is not less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%:
e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: 6
f) The distance between the ball gap cannot exceed 0.5 times the ball diameter: JB/T7070.3—2002
The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density g)
should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and a voltage (U, or U) closest to the neutral voltage U of U, in V: U,-test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequency of the test voltage should not be less than 100Hz (preferably between 150Hz and 400Hz). The duration is calculated as follows: t=120×blood
Where:
t—test time, in seconds:
f.--rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration should be not less than 15s: 130% of the rated input voltage can also be applied for a duration of 3min. 14 Resistance conversion
The unbalance rate of three-phase resistance is calculated with the difference between the maximum and minimum values of the three-phase resistance as the numerator and the average value of the three-phase resistance as the denominator.
When the unbalance rate of the three-phase line resistance is less than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection
Where:
Rxs—phase resistance of three phases, unit is 2;—line resistance of three phases, unit is 2.
When the three-phase resistance unbalance rate is greater than 2%, the conversion between line resistance and phase resistance is calculated according to the following formula: Y-type connection
D-type connection (ay:bzicx)
Where:
R, =Rs +Ra -Rs
Rg =Rg +Rg -Ra
R. = Rs +Ra -Ra
R, =(Rea -R)-
Rab×Re
Rea-R,
Rea×R
Rg=(Rab -R,)-4
Rab -Rp
Rab×Ra
R=(RxR)-4
R, =Ra +Re +Ra
Rab, Rre, Rea line resistance between each phase, unit is 2; phase resistance of each phase, unit is 2;
Ra, Rp, R.
R—average value of phase resistance, unit is 2.
When converting winding resistance at different temperatures, calculate according to the following formula: R=K,×R
Where:
R. —Resistance when temperature is ℃, unit is Q; —Resistance when temperature is t℃, unit is Q: R,
—Resistance temperature coefficient: www.bzxz.net
—Temperature coefficient, copper winding is 235, aluminum winding is 225: Reference temperature, unit is ℃:
JB/T7070.3—2002
JB/T7070.3—2002
9—Actual temperature, unit is ℃.
11 Power frequency withstand voltage test
11.1 Overview
The power frequency withstand voltage test is used to assess the withstand voltage strength of the main insulation of the magnetic voltage regulator. The test circuit is shown in Figure 1. R
TR——Voltage regulator: T—Test transformer: TA-—Current transformer: A-—Ammeter: V, V2—Voltmeter V-Peak voltage meter. R--Discharge resistor: R.—Protection resistor: R2 Damping resistor: C--—Capacitor voltage divider main capacitor C—Voltage divider capacitor: C—Test product: Q—Ball gap (or electrostatic voltmeter. For products with voltage levels below 35kV Figure 1 Power frequency withstand voltage test circuit diagram
112 Test requirements
During the power frequency withstand voltage test, the core and shell of the tested product must be reliably grounded. And the oil level indication of the test product must be high In the cable bushing or bushing riser. Before the test, the bushing connected to the main oil and the low-voltage terminal board, hand hole cover, riser and other raised parts should be deflated until the oil is visible.
All terminals of the tested winding of the test product should be connected to the live wire, and all terminals of the non-tested winding should be grounded. The frequency of the power frequency withstand voltage test should not be less than 80% of the rated frequency, preferably between 45Hz and 55Hz. Its voltage waveform should be close to sine (the two half-waves are exactly the same, and the ratio of the peak value to the root mean square value is equal to 2±0.07), or the root mean square value of each harmonic is not greater than 5% of the root mean square value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should not be less than 0.1A. For products with larger capacity, the steady-state short-circuit current should not be less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and the voltage should be maintained constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the root mean square value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
It is recommended to use a capacitive voltage divider calibrated by the metrology department to measure the test voltage with a peak voltage meter, or it can be measured with a spherical gap. When using a spherical gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The spherical gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: the spherical gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the spherical gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the spherical gap is discharged, the voltage boost speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, take the average value of 3 discharge voltages. Each discharge gap is not less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%:
e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: 6
f) The distance between the ball gap cannot exceed 0.5 times the ball diameter: JB/T7070.3—2002
The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density g)
should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and a voltage (U, or U) closest to the neutral voltage U of U, in V: U,-test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequency of the test voltage should not be less than 100Hz (preferably between 150Hz and 400Hz). The duration is calculated as follows: t=120×blood
Where:
t—test time, in seconds:
f.--rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration should be not less than 15s: 130% of the rated input voltage can also be applied for a duration of 3min. 1=Ra +Re +Ra
Rab, Rre, Rea Line resistance between each phase, unit is 2; Phase resistance of each phase, unit is 2;
Ra, Rp, R.
R—Average value of phase resistance, unit is 2.
When converting winding resistance at different temperatures, calculate according to the following formula: R=K,×R
Where:
R. —Resistance when temperature is ℃, unit is Q; —Resistance when temperature is t℃, unit is Q: R,
-Resistance temperature coefficient:
-Temperature coefficient, copper winding is 235, aluminum winding is 225: Reference temperature, unit is ℃:
JB/T7070.3—2002
JB/T7070.3—2002
9-Actual temperature, unit is ℃.
11 Power frequency withstand voltage test
11.1 Overview
The power frequency withstand voltage test is used to assess the withstand voltage strength of the main insulation of the magnetic voltage regulator. The test circuit is shown in Figure 1. R
TR——Voltage regulator: T—Test transformer: TA-—Current transformer: A-—Ammeter: V, V2—Voltmeter V-Peak voltage meter. R--Discharge resistor: R.—Protection resistor: R2 Damping resistor: C--—Capacitor voltage divider main capacitor C—Voltage divider capacitor: C—Test product: Q—Ball gap (or electrostatic voltmeter. For products with voltage levels below 35kV Figure 1 Power frequency withstand voltage test circuit diagram
112 Test requirements
During the power frequency withstand voltage test, the core and shell of the tested product must be reliably grounded. And the oil level indication of the test product must be high In the cable bushing or bushing riser. Before the test, the bushing connected to the main oil and the low-voltage terminal board, hand hole cover, riser and other raised parts should be deflated until the oil is visible.
All terminals of the tested winding of the test product should be connected to the live wire, and all terminals of the non-tested winding should be grounded. The frequency of the power frequency withstand voltage test should not be less than 80% of the rated frequency, preferably between 45Hz and 55Hz. Its voltage waveform should be close to sine (the two half-waves are exactly the same, and the ratio of the peak value to the root mean square value is equal to 2±0.07), or the root mean square value of each harmonic is not greater than 5% of the root mean square value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should not be less than 0.1A. For products with larger capacity, the steady-state short-circuit current should not be less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and the voltage should be kept constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the root mean square value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
The test voltage is recommended to be measured by a capacitive voltage divider calibrated by the metrology department in combination with a peak voltage meter, or it can be measured using a spherical gap. When using a spherical gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The spherical gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: the spherical gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the spherical gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the spherical gap is discharged, the voltage boost speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, take the average value of 3 discharge voltages. Each discharge gap is not less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%:
e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: 6
f) The distance between the ball gap cannot exceed 0.5 times the ball diameter: JB/T7070.3—2002
The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density g)
should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and a voltage (U, or U) closest to the neutral voltage U of U, in V: U,-test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequency of the test voltage should not be less than 100Hz (preferably between 150Hz and 400Hz). The duration is calculated as follows: t=120×blood
Where:
t—test time, in seconds:
f.--rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration should be not less than 15s: 130% of the rated input voltage can also be applied for a duration of 3min. 1=Ra +Re +Ra
Rab, Rre, Rea Line resistance between each phase, unit is 2; Phase resistance of each phase, unit is 2;
Ra, Rp, R.
R—Average value of phase resistance, unit is 2.
When converting winding resistance at different temperatures, calculate according to the following formula: R=K,×R
Where:
R. —Resistance when temperature is ℃, unit is Q; —Resistance when temperature is t℃, unit is Q: R,
-Resistance temperature coefficient:
-Temperature coefficient, copper winding is 235, aluminum winding is 225: Reference temperature, unit is ℃:
JB/T7070.3—2002
JB/T7070.3—2002
9-Actual temperature, unit is ℃.
11 Power frequency withstand voltage test
11.1 Overview
The power frequency withstand voltage test is used to assess the withstand voltage strength of the main insulation of the magnetic voltage regulator. The test circuit is shown in Figure 1. R
TR——Voltage regulator: T—Test transformer: TA-—Current transformer: A-—Ammeter: V, V2—Voltmeter V-Peak voltage meter. R--Discharge resistor: R.—Protection resistor: R2 Damping resistor: C--—Capacitor voltage divider main capacitor C—Voltage divider capacitor: C—Test product: Q—Ball gap (or electrostatic voltmeter. For products with voltage levels below 35kV Figure 1 Power frequency withstand voltage test circuit diagram
112 Test requirements
During the power frequency withstand voltage test, the core and shell of the tested product must be reliably grounded. And the oil level indication of the test product must be high In the cable bushing or bushing riser. Before the test, the bushing connected to the main oil and the low-voltage terminal board, hand hole cover, riser and other raised parts should be deflated until the oil is visible.
All terminals of the tested winding of the test product should be connected to the live wire, and all terminals of the non-tested winding should be grounded. The frequency of the power frequency withstand voltage test should not be less than 80% of the rated frequency, preferably between 45Hz and 55Hz. Its voltage waveform should be close to sine (the two half-waves are exactly the same, and the ratio of the peak value to the root mean square value is equal to 2±0.07), or the root mean square value of each harmonic is not greater than 5% of the root mean square value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should not be less than 0.1A. For products with larger capacity, the steady-state short-circuit current should not be less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and the voltage should be kept constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the root mean square value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
The test voltage is recommended to be measured by a capacitive voltage divider calibrated by the metrology department in combination with a peak voltage meter, or it can be measured using a spherical gap. When using a spherical gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The spherical gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: the spherical gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the spherical gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the spherical gap is discharged, the voltage boost speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, take the average value of 3 discharge voltages. Each discharge gap is not less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%:
e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: 6
f) The distance between the ball gap cannot exceed 0.5 times the ball diameter: JB/T7070.3—2002
The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density g)
should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and a voltage (U, or U) closest to the neutral voltage U of U, in V: U,-test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequency of the test voltage should not be less than 100Hz (preferably between 150Hz and 400Hz). The duration is calculated as follows: t=120×blood
Where:
t—test time, in seconds:
f.--rated frequency, in Hz;
ftest frequency, in Hz;
If the test frequency exceeds 400Hz, the duration should be not less than 15s: 130% of the rated input voltage can also be applied for a duration of 3min. 107), or the RMS value of each harmonic is not greater than 5% of the RMS value of the fundamental wave).
The steady-state short-circuit current of the test transformer under the test voltage should be no less than 0.1A. For products with larger capacity, the steady-state short-circuit current should be no less than IA.
The initial value of the test voltage should be lower than 1/3 of the test voltage value, and it should be added to the test voltage value as soon as possible in coordination with the measurement, and its voltage should be kept constant for 60s. Then the voltage is quickly reduced to less than 1/3 of the test voltage value, and the power supply is finally cut off. When the voltage waveform meets the requirements, the voltage can be applied according to the RMS value. Otherwise, the voltage should be applied according to 1/2 of the peak voltage. 11.3 Test voltage determination
It is recommended to use a capacitive voltage divider calibrated by the metrology department to measure the test voltage in combination with a peak voltage meter, or it can be measured with a ball gap. When using the ball gap for measurement, the provisions of GB/T311.6-1983 should be followed, and the following items should be noted: a) The ball gap damping resistance can usually be selected at 1Q/V at a frequency of 50Hz: The ball gap must be discharged to measure the voltage, usually at 80% of the test voltage. During the test, the ball gap should be adjusted to a distance of 120% of the test voltage to protect the test product:
When the ball gap is discharged, the voltage increase speed is not limited before 40% of the pre-discharge voltage. The subsequent voltage increase speed is required to be uniform, and the voltage increase per second is about 2% of the expected discharge voltage:
In each measurement, the average value of the three discharge voltages is taken. Each discharge gap shall not be less than 1min, and the ratio of the discharge voltage to the average value shall not be greater than 3%: e) If there is dust or fiber in the air that causes abnormal discharge, several pre-discharges should be performed before formal discharge: f) The distance between the ball gaps shall not exceed 0.5 times the ball diameter: JB/T7070.3—2002 The air density P has a direct impact on the discharge voltage. The air density during the test is often different from the standard situation, so the air density should be corrected. The method is in accordance with the relevant provisions of GB/T16927.11997; when P. is significantly different from 1 (i.e. P<0.95 or P>1.05), use: instead of P. (see Table 2). When the discharge voltage and the corresponding spherical gap distance cannot be directly found out according to GB311.1, the two adjacent voltages and corresponding distances shall be used to calculate according to the formula (h):
S, =s-(S-SXU-u)
Wherein:
Sy——spherical gap distance of test voltage U,, in cm: S
spherical gap distance corresponding to U (S or S2), in cm: S, the spherical gap distance when the voltage is U, (U, is greater than U,), in cm: S2—spherical gap distance when the voltage is U2 (Uz is less than U), in cm; U——U, and a voltage (U, or U) closest to the neutral voltage U of U, in V: U,-test voltage, in V;
test input voltage, in V:
test output voltage, in V.
Table 2 Relationship between air density Pa and factor P
114 Other provisions
In order to reduce the capacity of the power supply or eliminate the self-excitation phenomenon of the generator, an appropriate reactor can be connected in the test circuit to compensate for the capacitive current.
During the test, if the voltage does not drop suddenly, the current indication does not swing, and there is no discharge sound, the test should be considered qualified: if there is a slight discharge sound, it disappears in the repeated test, and the test should also be considered qualified: if there is a large discharge sound, it disappears in the repeated test, it is necessary to hang the core for inspection, find the discharge location, and take necessary measures, and decide whether to retest based on the discharge location. 12 Induction withstand voltage test
12.1 Overview
The induction withstand voltage test is used to assess the insulation strength between turns, layers, sections and phases of the product winding. The test circuit is shown in Figure 2 and should be carried out after the power frequency withstand voltage test.
12.2 Test method
The induction withstand voltage test usually applies twice the rated voltage. In order to reduce the excitation capacity, the frequ
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