Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T7088-1993
Partial Discharge Detector
1993-10-08 Issued
Ministry of Machinery Industry of the People's Republic of China
1994-01-01 Implementation
Mechanical Industry Standard of the People's Republic of China
Partial Discharge Detector
1 Subject Content and Scope of Application
JB/T7088-1993
This standard specifies the main technical requirements, test methods and inspection rules for partial discharge detectors. This standard applies to partial discharge detectors (hereinafter referred to as partial discharge detectors) that meet the requirements of GB7354 and adopt the pulse current method, and also includes partial discharge detection systems with electronic computers and digital recorders. 2 Reference standards
GB7354
GB4793
GB6593
CB3100
GB3101
3 Terms and definitions
Partial discharge measurement
High voltage test technology
Safety requirements for electronic measuring instruments
Inspection rules for electronic measuring instruments
Packaging, storage and transportation pictorial symbols
International System of Units and its application
General principles for quantities, units and symbols The terms and definitions used in this standard are consistent with those in GB7354. The following terms and definitions are only applicable to this standard. 3.1 Partial discharge detector Partial discharge detector is an instrument device that can measure the apparent charge 9 after calibration. It consists of a measuring impedance, an amplifier with a certain bandwidth and an indicating device. Among the indicating devices, an oscilloscope is usually indispensable. 3.2 Pulse peak response of partial discharge detector When a pulse signal is injected into the partial discharge detector (generally injected through the measuring impedance), its corresponding pulse amplitude output can be the pulse height on the time base sweep baseline of the oscilloscope screen; it can also be the corresponding reading on other indicating devices (pulse peak meter, digital recorder, etc.) (hereinafter referred to as pulse response).
3.3 Scale factor KScalefector
Multiplying the pulse response value of the calibrated partial discharge detector can obtain the corresponding apparent charge value. 3.4 Calibration pulse generator Calibrating pulse generator A pulse generator that can generate a known charge q. It consists of a pulse voltage generator with an amplitude of U. connected in series with a small known capacitor C. (injection capacitor). At this time, the calibration pulse value is equivalent to a discharge of 9. qo=CU.
The waveform of the calibration pulse generator should meet the requirements of Article 5.1.1 of GB7354. 3.5 Measuring impedance Measuring impedance Zm is a device that receives the current pulse generated by the test object when the partial discharge is generated and converts it into a voltage pulse. For a short-duration current pulse, the peak value of the voltage pulse on the measuring impedance is proportional to the apparent charge 9 of the test object. The measuring impedance is a four-terminal network, which can be composed of a resistor, a resistor in parallel with a capacitor, a tuned circuit or a more complex filter. 3.6 Upper cut-off frequency f2 and lower cut-off frequency f, Upper cut-off frequency fz and lower cut-off frequency f, approved by the Ministry of Machinery Industry on October 8, 1993
implemented on January 1, 1994
JB/T7088-1993
frequency f, and so is the frequency; at this frequency, the response to a constant sinusoidal input voltage drops to a certain extent, usually 3db from the stable value in the case of broadband amplifier circuits, and 6db from the peak value in the case of narrow-band amplifier circuits (bandwidth not greater than 10kHz).
3.7 Coupling capacitor C Coupling capacitor C is a capacitor that couples the current pulse generated by the partial discharge of the test piece to the measuring impedance to improve the detection sensitivity. Its own partial discharge should be small enough under the test voltage, the residual inductance should be small and the resonant frequency should be not less than 3f2. 3.8 Tuning capacitor Cr Resonance Capacitor Cr Tuning circuit type The total capacitance at the input end of the measuring impedance. When the tuning capacitance value Cr makes the resonant frequency of the measuring impedance fall within the frequency band of the partial discharge detector amplifier circuit, the measurement can be close to the highest sensitivity of the instrument. The tuning capacitance Cr is determined by the test piece capacitance Cx, coupling capacitance Ck, the distributed capacitance C of the transmission cable, and the stray capacitance C. When the tuning capacitance Cr is mainly determined by the test piece capacitance Cx and the coupling capacitance C, Cr is approximately the combined value of Cx and C. CxC
Cr=C,+C,+ Cx+C
3.9 Pulse resolution time Pulse resolution time (1)
The pulse resolution time is the minimum time delay between two consecutive pulses, during which the amplitude error caused by pulse overlap is less than 10%.
The pulse resolution time is inversely proportional to the bandwidth (f2-f,) of the partial discharge detector. 3.10 Non-linearity (of pulse response) The non-linearity of the pulse response of the calibrated partial discharge detector in its effective working range is a measure of the difference between the measured response characteristics and the ideal straight line characteristics, and is the main factor in the measurement error of the scale factor K. 3.11 Detection sensitivity qs Detectivityq The detection sensitivity of the apparent charge q$ refers to the minimum discharge charge value that can be detected by the partial discharge detector with a certain signal-to-noise ratio (usually the signal-to-noise ratio s/n=2) to remove external interference when the partial discharge detector is connected to the test sample, coupling capacitor and measurement impedance. 3.12 Time window device or gate unit Time window unit or gate unit is a device that enables the pulse response of the partial discharge detector to be selected in certain phase intervals within the test voltage cycle. Its purpose is to suppress the influence of fixed phase interference on partial discharge measurement. 3.13 Pulse peak meter Pulse peak meter is a device specially used in the partial discharge detector to indicate the pulse peak value of the pulse response output. Generally, it is controlled by the time window device. It should have a fast response and a certain peak holding ability. 3.14 Double pulse generator (for partial discharge measurement) Double pulse generator (for partial discharge measurement) can generate two identical response pulses with adjustable time delay △t when injected into the partial discharge detector. The overlapping of the two pulses can be observed by adjusting the time delay △t. The pulse wave rising edge and duration of the double pulse generator shall comply with the requirements of Article 5.1.1 of GB7354. 4 Technical requirements
General requirements
4.1.1 The partial discharge detector shall be manufactured according to the drawings and technical documents approved by the prescribed procedures. 4.1.2 The rated operating conditions of the partial discharge instrument are shown in Table 1. Under this condition, the partial discharge instrument shall be able to work normally. Table 1 Rated operating conditions
Ambient temperature
Relative humidity
Power supply voltage
Power supply frequency
5℃~40℃
20%~80%
220V (effective value)±10%
50Hz±3%
Note: The partial discharge instrument shall be able to work for a short period of time at 0℃. 4.2 Appearance quality
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4.2.1 The shell of the PD instrument should have no obvious defects, the coating should not be peeled or peeled, and the electroplating and oxide layers should be good. 4.2.2 There should be no sharp peaks on the outside.
4.2.3 The text symbols of various quantities and units on the panel should comply with the requirements of GB3100 and GB3101. The printing or engraving should be clear and obvious and not easy to be erased.
4.3 Oscilloscope scanning display characteristics
4.3.1 The oscilloscope scanning baseline is recommended to use elliptical or sine wave display. The rotation direction of the elliptical scanning should be specified in the technical documents. The elliptical scanning should be able to display the signal marking the zero crossing point or peak point of the test voltage. 4.3.2 Its focus should be able to be adjusted to the time base scanning line and pulse signal on the oscilloscope screen to be clearly distinguishable, and the trace width on the oscilloscope screen should not exceed 0.5mm.
4.3.3 The brightness adjustment should be able to ensure that the time base scan line and pulse signal have sufficient brightness for observation when there is no strong light directly on the oscilloscope screen. 4.4 Frequency band and cut-off frequency
4.4.1 The partial discharge instrument can have one frequency band or several optional frequency bands, and the upper and lower cut-off frequency values or frequency band range should be marked on the instrument panel. 4.4.2 The error E between the upper and lower cut-off frequencies and their nominal values shall not exceed ±10%. 4.5 Basic error of apparent charge q measurement
4.5.1 Nonlinear error E
Within the normal operating range of the PD instrument, the maximum nonlinear error in the effective range of its indication shall not exceed ±10%. 4.5.2 Asymmetric error Es of positive and negative pulse response. The error between the pulse response values of the PD instrument to two injected calibration pulses of equal amplitude and opposite polarity shall not exceed ±10%. 4.5.3 Range shift error Er
The error between the measured value of the gain difference between two adjacent gears of the PD instrument amplifier gain shift switch and its nominal value shall not exceed ±10%. 4.5.4 Low repetition rate pulse response error E
For injected pulses of the same amplitude, when the pulse repetition rate is reduced from 1000Hz to 25Hz, the change in its pulse response shall not exceed ±10%.
Pulse resolution time
The pulse resolution time and the corresponding test frequency band should be listed in the relevant technical documents, unless it is a narrow-band instrument, the pulse resolution time should not exceed 100μs. For a PD instrument with multiple cheek straps, the minimum and maximum pulse resolution times should be listed. 4.7 Detection sensitivity qs
The detection sensitivity value of the apparent charge must be listed in the relevant technical documents in text or diagram form, and its test conditions such as the serial number or parameters of the measured impedance, the tuning capacitance Cr (or the test sample capacitance Cx and the coupling capacitance C value), the test frequency band, etc. should be explained. 4.8 Repetition rate n
a. The measurement range of the repetition rate n should be indicated on the panel of the PD instrument. b. The measurement error En of the repetition rate n shall not exceed ±10%. Note: If the PD instrument does not have the function of measuring the repetition rate n, this item is cancelled. 4.9 Measurement impedance
4.9.1 The maximum allowable working current (effective value) should be indicated in the technical documents. At this power frequency current value, it should be able to last for 1 hour without damage. 4.9.2 The tuning capacitor Cr range shall be indicated on the technical documents and the measurement impedance panel (except for non-tuning measurement impedance). The technical documents shall describe the range of the test sample capacitance Cx and coupling capacitance C that are compatible with it in words or diagrams. 4.9.3 There shall be an overvoltage protection device, and its impulse voltage protection level shall not exceed 100V. 4.10 Stability
After the partial discharge instrument has been working for 8 hours, the change in the pulse response value of the calibration pulse signal injected with a constant amplitude shall not exceed ±10%. 4.11 Safety requirements
JB/T7088-1993
1 The safety requirements of the partial discharge instrument shall comply with the requirements of Class I instruments in GB4793 except for those that must meet the requirements of this standard. 4.11.1
4.11.2 The PD instrument should have good protection against electric shock. a.
Each easily accessible part should not be charged;
Each operating axis is not allowed to be charged;
The operating knobs and handles should be made of insulating materials; When designing the ventilation holes or other holes above the charged body, it should be ensured that the suspended debris entering the PD instrument cannot contact the charged parts inside the instrument. 4.11.3 When the PD instrument is in normal use, the temperature rise of each part should not exceed the specified value in Table 2. Table 2
Parts of the instrument only
Surface of the shell
Metal knobs, handles, etc.
Non-metal knobs, handles, etc.bzxz.net
Power transformer winding:
Note: ①The temperature rise limit is based on the ambient temperature of 40℃. ②The winding temperature rise is measured by the resistance method, and the rest is measured by the thermometer method. Allowable temperature rise, K
4.11.4 The leakage current from any pole of the partial discharge instrument power supply to the accessible surface of the instrument shall not be greater than 5mA. 4.11.5 The partial discharge instrument shall be able to withstand the moisture that may occur in normal use. After a 48h humidity test, the safety of the instrument shall not be damaged.
4.11.6 Insulation resistance and dielectric strength
4.11.6.1 The insulation resistance between the primary circuit of the power supply of the partial discharge instrument and the casing shall not be less than 2MQ. 4.11.6.2 The primary circuit of the power supply of the partial discharge instrument and the casing shall be able to withstand a test voltage of 50Hz, a real sine wave waveform, and a voltage of 1500V for 1min without breakdown or flashover. After the test, the partial discharge instrument shall be able to work normally. 4.11.7 Grounding protection
The PD instrument shall have a separate grounding terminal that is reliably connected to the casing and meets the following requirements a.
The grounding terminal shall be connected to the external grounding wire by screwing: The effective metal cross-sectional area of the grounding terminal shall not be less than 10mm, and the grounding terminal shall not cause corrosion when it contacts any other metal; The resistance between the grounding terminal and the metal required to be connected to it shall not be greater than 0.5α; The grounding mark shall be close to the grounding terminal and shall not be placed on detachable parts. The internal structure and circuit connection of the PD instrument shall meet the following requirements: To prevent short circuit caused by accidental loosening of wires, screws, etc. The strength of the wire connection point that bears mechanical stress shall not rely solely on welding; The length of the screws for fixing the back cover, bottom plate, etc. shall not reduce the creepage distance and electrical clearance between the accessible parts and the live parts to below the specified value,
The internal connection with the type glue wire shall comply with GB5013: e.
The creepage distance and electrical clearance between the components shall comply with the provisions of Article 9.5.4 of GB4793. Components directly connected to the grid power supply should meet the following requirements: 4.11.9
The power socket on the PD meter should meet the corresponding standards: The soft wire connecting the PD meter and the grid power supply must meet the requirements of GB5023.3, and its core wire section should not be less than 0.75mm, one of the core yellow-green two-color wires can only be connected to the grounding plug, and the length of the soft wire should not be shorter than 2500mm; 4
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The type of the plug connecting the grid power supply should meet GB11919; The type of the plug connecting the PD meter should meet the corresponding standards. C
4.12 Mechanical strength
The PD meter should have sufficient mechanical strength, the fastening of the parts and the electrical connection must be safe and reliable, the internal wiring method should not damage its insulation, and remain unchanged during normal use, and the PD meter should be able to withstand the following tests: a.
Drop test;
Impact hammer test.
After the test, the instrument shall be subjected to the withstand voltage test of Article 4.11.6. The live parts shall not become accessible parts, the casing shall not have obvious cracks, and the insulation shall not be damaged, loose or fall off. 4.13 Others
The power consumption, overall dimensions (width × height × depth) and weight shall be stated in the relevant technical documents. 5
Test method
Test environmental conditions
The various performances of the partial discharge instrument must be tested under the test environmental conditions specified in Table 3. Table 3 Test environment conditions
Ambient temperature
Relative humidity
Atmospheric pressure
Power supply voltage
Power supply rate
Waveform distortion
External electromagnetic field interference
(860-1080)mbar
220V (effective value)
Sine wave
Should be avoided
Allowable deviation
±5℃
Distortion coefficient β=0.05
Note: β is the distortion coefficient. That is, the distortion of the AC power supply voltage waveform should be kept within the envelope formed by (1+β)ASinat. 5.2 Test preparation
5.2.1 Before the partial discharge instrument is connected to the power supply, it should be placed under the conditions specified in Table 3 for more than 2 hours. 5.2.2 After power is turned on, preheat according to the specified preheating time. 5.3 Inspection of appearance quality
Use visual inspection and manual test.
The test results shall comply with Article 4.2.
5.4 Inspection of oscilloscope scanning display characteristics
After adjusting the corresponding control knob, visually inspect. The test results shall comply with Article 4.3.
In the case of elliptical scanning, use the following method to check the zero-crossing mark or peak mark: Use an artificial discharge needle and a ball as the test piece, the needle is connected to high voltage and the ball is grounded. When the test voltage rises to the starting discharge voltage and the first discharge pulse appears, the phase generated should be at the peak point of the negative half cycle (270°). 5.5 Testing of frequency band and cut-off frequency
5.5.1 The test circuit is shown in Figure 1. The test instrument used shall meet the following requirements: The frequency range of the audio (high) frequency signal generator shall be able to cover the maximum frequency band range of the inspected partial discharge instrument and extend more than twice at both ends; a.
The maximum error of the audio (high) frequency voltmeter shall not be greater than 2%; the maximum error of the frequency meter shall not be greater than ±1%. 5
Audio (high) frequency
Signal generator
JB/T7088-1993
Figure 1 Wiring diagram of frequency band and cut-off frequency test circuit PDD—tested PD instrument host; V—audio (high) frequency voltmeter; f-rated frequency meter Test steps
Saturation;
According to Figure 1, send the audio (high) frequency voltage output to the amplifier entrance of the PD instrument: PDD
If the PD instrument under test has multiple rated bands, the frequency band taken for the test should include the various values of the upper and lower cut-off rated rates of the PD instrument; the coarse gain adjustment gear of the PD instrument under test is set to a certain middle gear; the upper and lower cut-off frequency nominal values f2 of the tested PD instrument's frequency band are used to calculate its center frequency f. fo=Vfzexffe
The input frequency of the amplifier of the PD instrument under test is a sinusoidal voltage of f. The injection voltage should be large enough to make the PD instrument's oscilloscope respond with f. Record the output of the PD instrument at this time (output height on the oscilloscope screen or other output device readings), and normalize this output value to 1; g. Under the condition of keeping the input voltage value unchanged and the amplifier gain unchanged, gradually reduce the frequency of the signal generator and record the output of the PD instrument (normalized reading) until the output normalized value of the PD instrument drops to 0.707 (attenuation 3db point). The frequency at this time is the measured lower cutoff frequency f1. Conversely, the frequency point when the frequency increases from f. to the normalized value of the output drops to 0.707 is the measured upper cutoff frequency fz. For narrow-band amplifiers, the frequency at which the output normalized value drops to 0.501 (attenuation 6db point) is the cutoff frequency, and the record is filled in Table 4. Table 4
Frequency (kHz)
Output (normalized)
In the table; ff.
Nominal value of lower cutoff frequency;
Nominal value of upper cutoff frequency.
Note: The number of measurement points in Table 4 increases or decreases as the video bandwidth is narrow. 5.5.3 Calculation of error of upper and lower cutoff frequencies. The error between the upper and lower cutoff frequencies and their nominal values is calculated according to formula (3): Ee
Where: f. Nominal value of upper or lower cutoff frequency; f——measured value of upper or lower cutoff frequency.
This error shall meet the requirements of Article 4.4.2.
5.6 Test of nonlinear error
5.6.1 Test wiring is shown in Figure 2
=×100%
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Figure 2 Nonlinear error test wiring diagram
G-calibration pulse generator, the maximum amplitude error is not more than 2%; V-oscilloscope or pulse peak meter, the maximum error is not more than 2%, PDD
B. Measurement impedance;
PDD-partial discharge instrument under test.
Let Cx=C\, and make Cx/2 near the center of the tuning capacitance range of the measurement impedance Z. It is allowed to use small-volume electric guest devices used in radio technology as Cx and Ck, but the residual inductance should be small. C. Select according to 10pF≤C<0.1Cx.
The wiring in the loop should be as short as possible.
If the pulse response amplitude of the calibration pulse generator G when injected from both ends of Cx is insufficient, the method shown in the dotted box in Figure 2 can be used, that is, the calibration pulse generator G' is injected from both ends of the detection impedance Z through C. The selection of C. is the same as C. . Note: 1) If there are special provisions for Cx and C in the manufacturer's technical documents, the specified values shall be used during the test. 5.6.2 Test steps
8. The amplifier gain of the tested partial discharge instrument is roughly adjusted to a certain middle gear. If there are multiple frequency bands to choose from, it is set to a certain middle frequency band; b. Adjust the amplitude U. of the calibration pulse generator, and cooperate with the amplifier gain fine adjustment device to make the pulse response (pulse height or peak meter reading on the oscilloscope screen, etc.) full scale, and its reading is Af, and record the injected pulse amplitude U. value at this time; the injected pulse amplitude U. Decrease according to the linear law, and its attenuation ratio is, from 1 to 0.2. Take no less than 5 measurement points, C
Record the corresponding output reading A of the measured partial discharge instrument, and fill in the measurement results in Table 5. Table 5 Nonlinear error test table format example
Injection pulse ratio
Pulse response reading
Nonlinear error
5.6.3 Calculation of nonlinear error E1
The attenuation ratio of the injected pulse multiplied by the full-scale reading Ar is used as the standard value, so the nonlinear error E1 is calculated according to formula (4): E
×100%
Calculate E at each measurement point, and its maximum value should meet Article 4.5.1. 5.7 Test of asymmetric error and range shift error of positive and negative pulse response. ....
5.7.1 The test circuit is shown in Figure 2, but the calibration pulse generator G or G' used must be able to synchronize with the power supply, that is, the repetition rate is 100Hz and 7
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each cycle generates a positive pulse and a negative pulse with the same amplitude. If the partial discharge instrument has a time window and a peak meter device, it should be possible to obtain the corresponding readings of the positive and negative pulses by adjusting the time window. The amplitude of the calibration pulse generator G or G' should generally have an adjustment range of not less than 80db, and its maximum amplitude should generally be not less than 100V (in principle, it can cover the entire range of the partial discharge instrument under test). The requirements for Cx, C and C. are the same as those in Article 5.6.1.
The injection method shown in the dotted box in Figure 2 is allowed to be used to test multiple ranges of the partial discharge instrument. 5.7.2 Preparation for the test
8. If the PD instrument has multiple frequency bands to choose from, the selected frequency bands should cover all values of its upper and lower cut-off frequencies. However, during the factory test, an intermediate band can be selected to test the range shift error; b. The amplifier gain fine adjustment device is in a position close to the minimum position; c. If the PD instrument is equipped with multiple measuring impedances, if not specified, one of the measuring impedances with an intermediate serial number can be selected for this test. 5.7.3 Test steps
Set the gain coarse adjustment switch to the highest gain level and inject the calibration pulse U. , slightly adjust the gain fine adjustment device to make the pulse response (pulse height or peak meter reading on the oscilloscope screen) reach full scale. In subsequent tests, the gain fine adjustment position is not allowed to change; b. If the PD instrument under test does not have a peak meter, measure the positive and negative pulse heights on the oscilloscope screen (measure from the scanning baseline, if the pulse has oscillation, measure the maximum amplitude), and pay attention to the pulse shape and polarity, and fill in the results in Table 6; if the PD instrument under test has a time window and a peak meter, the response readings of the positive and negative pulses on the peak meter should be read again and filled in Table 6; C
Reduce the amplifier gain coarse adjustment switch by one gear, and then increase the calibration pulse amplitude U. accordingly, so that its pulse response is still close to full scale, then U. The increase multiple is the actual measured value of the gain change between the two gears of the amplifier. The error between it and the nominal value, that is, the range shift error between the two gears, should meet Article 4.5.3.
U can also be The amplitude increases according to the nominal value of the gain change between gears, and the pulse response value is read. The difference between it and the pulse response value of the lower gain gear is the range shift error between the two gears (the pulse response is not allowed to reach the saturation value during the test); e. Repeat step b (or c), repeat step d; f. Repeat step e until the gain coarse adjustment switch is at the lowest gear. Note: If the calibration pulse amplitude U. has reached the maximum value, this U. can be maintained during the test of the lower gain gear. Inject the calibration pulse and record its pulse response reading A1. Its ratio A/A to the pulse response reading A2 of the higher gain gear is the gain change value between the two gears, but the error is not counted. 5.7.4 Test table and error calculation
5.7.4.1 The test table for positive and negative pulse response asymmetry error and range shift error can refer to the example Table 6. In the "Gain Range" column of Table 6, range 5 is the highest gain range and range 0 is the lowest gain range. In this example, since there is a peak meter reading, the pulse response height on the oscilloscope screen can be omitted. However, the tester must still observe its size and shape during the test for reference. Table 6 Test Table Example
Positive and negative injection calibration pulse amplitude
Gain range
Time window
Left (+)
Left (+)
Right (-)
Left (+)
Right (-)
Response A
Pulse height on the oscilloscope screen
Peak meter reading
Positive and negative injection calibration pulse amplitude U
Test frequency band: (20200)kHz
Measurement impedance number: No. 7
5.7.4.2 Error calculation
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Continued Table 6
Gain gear
Time window
Left (+)
Right (-)
Left (+)
Right (-)
Left (+)
Right (-)
Pulse response A
Pulse height on the oscilloscope screen
5.7.4.2.1 The relative error 2[A(+)-A-)1 ×100%
of the difference between the pulse response readings A(+) and A(-) in the left and right time windows in Table 6 is the asymmetric error of the positive and negative pulse responses. A(+)+A(-)
Es of each gain level shall comply with 4.5.2 (in this example, the maximum Es is about 5%, less than 10%). Peak meter reading
++++++****(5)
Note: If the pulse response of a certain gain level is less than 20% of the full scale, the asymmetric error of the positive and negative pulse responses of this level shall not be taken into account (such as level 0 in this example). 5.7.4.2.2 There are two methods for calculating the gain shift error; a. If the pulse amplitude U is injected into two adjacent levels. When the gain changes according to the multiple between levels, the error of the pulse response of these two levels is the range shift error (when calculating the relative error Er by taking the larger error of the positive and negative pulse responses, the denominator is the average of the pulse response readings of these two levels). In the measurement example of Table 6, the calibration pulse amplitude U is injected into each level. According to the relationship of ten times the gain change between gears (i.e. 20db), the change of pulse response between two adjacent gears is about 5%, so the range shift error Er can be taken as 5%, which complies with Article 4.5.3. b. If the injected pulse amplitude U. is changed according to keeping the pulse response at full scale during gear shift, the change of U. between adjacent gears is the measured value of the gain change between adjacent gears, and the relative error between it and the nominal value of the gain change between gears is the range shift error Er. The largest error between adjacent gears is taken, which should comply with Article 4.5.3. 5.8 Low repetition rate pulse response error test
5.8.1 The test circuit diagram is shown in Figure 2, but the calibration pulse generator G must use a square wave generator with a duty cycle of about 50%, and the square wave frequency must be adjustable in the range of (10~1000) Hz and monitored by a frequency meter (with an accuracy of not less than 1%). 5.8.2 Test steps
If the PD under test has only multiple frequency bands, select an intermediate frequency band and any impedance to be measured. a.
b. Set the frequency of the square wave generator to 500Hz, and the square wave injection amplitude is U. , adjust the amplifier gain so that the pulse response reaches full scale, and the reading is A100
Keep the square wave amplitude U. unchanged, reduce the square wave frequency to 12.5Hz, observe and record its pulse response reading A2. e.
5.8.3 Calculation of low repetition rate response error
The low repetition rate response error EEa value calculated according to formula (5) should comply with Article 4.5.4.
5.9 Test of pulse resolution time
An-A0×100%
5.9.1 The test circuit is shown in Figure 2, but the calibration pulse generator G must use a double pulse generator (for partial discharge measurement) and connect an oscilloscope to view the waveform and measure the delay △t (in microseconds) between double pulses. 9
5.9.2 Test steps
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a. If there is no provision, select any measurement impedance; if there is no specification, place the multi-band partial discharge instrument in the narrowest band and the widest band and do it once each; b. The delay △t of the double pulse generator is set to the maximum first. Under a certain injection pulse amplitude, adjust the amplifier gain so that the pulse response reading is 90% full scale, and observe the shape and overlap of the two pulse responses on the oscilloscope screen of the partial discharge instrument: keep the injection pulse amplitude unchanged, gradually reduce the delay △ of the double pulse, observe the changes in the pulse response, and observe the changes in the overlap of the pulse response on the oscilloscope screen. When the pulse response reading increases or decreases by 10%, the double pulse delay value △t (in microseconds) at this time is the pulse resolution time under the measurement frequency band, and this value should not be greater than the value given by the manufacturer's technical conditions. 5.10 Test of detection sensitivity qs
5.10.1 The test circuit is shown in Figure 2. The injection method from both ends of the test product Cx should be adopted. The wiring should be as short as possible. To prevent external interference, the measurement impedance and Cx, C and Ce can be placed in a shielding box. 5.10.2 Test steps
Set the amplifier gain gear to the highest gear, and the gain fine adjustment to the near maximum position. For multiple bands, if there are no special provisions, set it to the widest a.
(or close to the widest) frequency band;
b. Inject the calibration pulse U. , observe the pulse response height on the oscilloscope screen of the tested PD instrument, and gradually reduce the U. amplitude until the pulse response height on the oscilloscope screen is twice the noise height of the tested PD instrument; c. Multiply the calibration pulse amplitude U. at this time by the injected capacitance Ce. That is, the minimum detectable charge qsqs=U.Ce
qs is the detection sensitivity of the apparent charge. (6)
d. Record the qs value, and note the Cx, C values and the frequency band used during the test, and the measurement impedance serial number. The 9s value should not exceed the value given in the manufacturer's technical documents.
5.11 Test of measurement error of discharge repetition rate n5.11.1 The test wiring diagram is shown in Figure 2, but the calibration pulse generator G uses a square wave generator with a duty cycle of about 50%, and is connected to a frequency meter with an error not exceeding ±1% (if the square wave generator is equipped with a frequency indicator, it can be omitted). 5.11.2 Test steps
If the PD instrument under test is a multi-band type, if there is no special provision, it is set to the narrowest frequency band, and the measurement impedance is optional; the frequency f of the square wave generator is set to make 2f equal to the full-scale value of the discharge repetition rate n meter of the PD instrument under test; b.
Input square wave, adjust the amplifier gain so that its pulse response is close to full scale, observe the reading on the repetition rate n meter of the PD instrument, and record the reading d. Reduce the frequency f of the square wave generator according to a linear relationship, select 5 points within the full range of n, the square wave amplitude remains unchanged, the amplifier gain remains unchanged, and when the square wave is injected with different frequencies f, record the corresponding reading n on the repetition rate meter and fill it in Table 7. Table 7 Repetition rate test record
square wave frequency +
repetition rate n
5.11.3 Calculation of test error En of repetition rate n Where f is the frequency of square wave generator;
is the reading of repetition rate meter of partial discharge instrument;
-2×100%
Fill in Table 7 after calculation. The maximum value of En in Table 7 shall meet the requirements of item b of 4.8. 5.12 Test of impedance measurement3 Calculation of low repetition rate response error
Calculation of low repetition rate response error EEa value according to formula (5) shall comply with 4.5.4.
5.9 Test of pulse resolution time
An-A0×100%
5.9.1 The test circuit is shown in Figure 2, but the calibration pulse generator G must use a double pulse generator (for partial discharge measurement) and connect an oscilloscope to view the waveform and measure the delay △t (in microseconds) between double pulses. 9
5.9.2 Test steps
JB/T7088-1993
a. If there is no provision, select any measurement impedance; if there is no specification, place the multi-band partial discharge instrument in the narrowest band and the widest band and do it once each; b. The delay △t of the double pulse generator is set to the maximum first. Under a certain injection pulse amplitude, adjust the amplifier gain so that the pulse response reading is 90% full scale, and observe the shape and overlap of the two pulse responses on the oscilloscope screen of the partial discharge instrument: keep the injection pulse amplitude unchanged, gradually reduce the delay △ of the double pulse, observe the changes in the pulse response, and observe the changes in the overlap of the pulse response on the oscilloscope screen. When the pulse response reading increases or decreases by 10%, the double pulse delay value △t (in microseconds) at this time is the pulse resolution time under the measurement frequency band, and this value should not be greater than the value given by the manufacturer's technical conditions. 5.10 Test of detection sensitivity qs
5.10.1 The test circuit is shown in Figure 2. The injection method from both ends of the test product Cx should be adopted. The wiring should be as short as possible. To prevent external interference, the measurement impedance and Cx, C and Ce can be placed in a shielding box. 5.10.2 Test steps
Set the amplifier gain gear to the highest gear, and the gain fine adjustment to the near maximum position. For multiple bands, if there are no special provisions, set it to the widest a.
(or close to the widest) frequency band;
b. Inject the calibration pulse U. , observe the pulse response height on the oscilloscope screen of the tested PD instrument, and gradually reduce the U. amplitude until the pulse response height on the oscilloscope screen is twice the noise height of the tested PD instrument; c. Multiply the calibration pulse amplitude U. at this time by the injected capacitance Ce. That is, the minimum detectable charge qsqs=U.Ce
qs is the detection sensitivity of the apparent charge. (6)
d. Record the qs value, and note the Cx, C values and the frequency band used during the test, and the measurement impedance serial number. The 9s value should not exceed the value given in the manufacturer's technical documents.
5.11 Test of measurement error of discharge repetition rate n5.11.1 The test wiring diagram is shown in Figure 2, but the calibration pulse generator G uses a square wave generator with a duty cycle of about 50%, and is connected to a frequency meter with an error not exceeding ±1% (if the square wave generator is equipped with a frequency indicator, it can be omitted). 5.11.2 Test steps
If the PD instrument under test is a multi-band type, if there is no special provision, it is set to the narrowest frequency band, and the measurement impedance is optional; the frequency f of the square wave generator is set to make 2f equal to the full-scale value of the discharge repetition rate n meter of the PD instrument under test; b.
Input square wave, adjust the amplifier gain so that its pulse response is close to full scale, observe the reading on the repetition rate n meter of the PD instrument, and record the reading d. Reduce the frequency f of the square wave generator according to a linear relationship, select 5 points within the full range of n, the square wave amplitude remains unchanged, the amplifier gain remains unchanged, and when the square wave is injected with different frequencies f, record the corresponding reading n on the repetition rate meter and fill it in Table 7. Table 7 Repetition rate test record
square wave frequency +
repetition rate n
5.11.3 Calculation of test error En of repetition rate n Where f is the frequency of square wave generator;
is the reading of repetition rate meter of partial discharge instrument;
-2×100%
Fill in Table 7 after calculation. The maximum value of En in Table 7 shall meet the requirements of item b of 4.8. 5.12 Test of impedance measurement3 Calculation of low repetition rate response error
Calculation of low repetition rate response error EEa value according to formula (5) shall comply with 4.5.4.
5.9 Test of pulse resolution time
An-A0×100%
5.9.1 The test circuit is shown in Figure 2, but the calibration pulse generator G must use a double pulse generator (for partial discharge measurement), and connect an oscilloscope to view the waveform and measure the delay △t (in microseconds) between double pulses. 9
5.9.2 Test steps
JB/T7088-1993
a. If there is no provision, select any measurement impedance; if there is no specification, place the multi-band partial discharge instrument in the narrowest band and the widest band and do it once each; b. The delay △t of the double pulse generator is set to the maximum first. Under a certain injection pulse amplitude, adjust the amplifier gain so that the pulse response reading is 90% full scale, and observe the shape and overlap of the two pulse responses on the oscilloscope screen of the partial discharge instrument: keep the injection pulse amplitude unchanged, gradually reduce the delay △ of the double pulse, observe the changes in the pulse response, and observe the changes in the overlap of the pulse response on the oscilloscope screen. When the pulse response reading increases or decreases by 10%, the double pulse delay value △t (in microseconds) at this time is the pulse resolution time under the measurement frequency band, and this value should not be greater than the value given by the manufacturer's technical conditions. 5.10 Test of detection sensitivity qs
5.10.1 The test circuit is shown in Figure 2. The injection method from both ends of the test product Cx should be adopted. The wiring should be as short as possible. To prevent external interference, the measurement impedance and Cx, C and Ce parts can be placed in a shielding box. 5.10.2 Test steps
Set the amplifier gain gear to the highest gear, and the gain fine adjustment to the near maximum position. For multiple bands, if there are no special provisions, set it to the widest a.
(or close to the widest) frequency band;
b. Inject the calibration pulse U. , observe the pulse response height on the oscilloscope screen of the tested PD instrument, and gradually reduce the U. amplitude until the pulse response height on the oscilloscope screen is twice the noise height of the tested PD instrument; c. Multiply the calibration pulse amplitude U. at this time by the injected capacitance Ce. That is, the minimum detectable charge qsqs=U.Ce
qs is the detection sensitivity of the apparent charge. (6)
d. Record the qs value, and note the Cx, C values and the frequency band used during the test, and the measurement impedance serial number. The 9s value should not exceed the value given in the manufacturer's technical documents.
5.11 Test of measurement error of discharge repetition rate n5.11.1 The test wiring diagram is shown in Figure 2, but the calibration pulse generator G uses a square wave generator with a duty cycle of about 50%, and is connected to a frequency meter with an error not exceeding ±1% (if the square wave generator is equipped with a frequency indicator, it can be omitted). 5.11.2 Test steps
If the PD instrument under test is a multi-band type, if there is no special provision, it is set to the narrowest frequency band, and the measurement impedance is optional; the frequency f of the square wave generator is set to make 2f equal to the full-scale value of the discharge repetition rate n meter of the PD instrument under test; b.
Input square wave, adjust the amplifier gain so that its pulse response is close to full scale, observe the reading on the repetition rate n meter of the PD instrument, and record the reading d. Reduce the frequency f of the square wave generator according to a linear relationship, select 5 points within the full range of n, the square wave amplitude remains unchanged, the amplifier gain remains unchanged, and when the square wave is injected with different frequencies f, record the corresponding reading n on the repetition rate meter and fill it in Table 7. Table 7 Repetition rate test record
square wave frequency +
repetition rate n
5.11.3 Calculation of test error En of repetition rate n Where f is the frequency of square wave generator;
is the reading of repetition rate meter of partial discharge instrument;
-2×100%
Fill in Table 7 after calculation. The maximum value of En in Table 7 shall meet the requirements of item b of 4.8. 5.12 Test of impedance measurement
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