The document discusses partial discharge (PD) testing of electrical equipment using a PD tester. It provides 18 diagrams of different types of PD patterns that could appear on the tester's screen during analysis. These include capacitive, internal insulation, contact, and corona discharge patterns that can help technicians correctly judge safety performance by identifying the source and nature of any discharges found during testing.

2. Partial Discharge (PD) Tester

3. Diagrams of Discharge Analysis and
Analysis of Interference Causes
• In order to ensure the safety of electrical equipment, we often use
partial discharge tester to test electrical equipment.
• After the test is finished, the diagram of partial discharge tester will
display on the screen based on the measurement results, which is
used to show the electrical equipment and the surrounding
discharge. How to determine whether it is in a safe range according
to the diagram, which requires the analysis of the causes of each
diagram.

4. • Next, we will list some of the waveform diagram of partial discharge
tester, so that the test personnel can correctly judge the results of the
test, and record the safety performance of the electrical equipment.

5. • Diagram 1
This is capacitive discharge waveform, which can occur in
insulation or solid insulation bubbles. It occurs in the oil
immersed capacitor , insulation or insulation plastic filler in
paper. The discharge amplitude and pulse number
increase with the voltage .

6. • Diagram 2
The internal discharge of the interlayer medium may also occur
in the carbonized discharge of the insulating board and the
climbing of the branches.

7. • Diagram 3
The discharge of an insulating medium that is in contact with
each other and the discharge in the oil impregnated paper
capacitor.

8. • Diagram 4
In the same medium, different sizes of bubbles may also form
this kind of circular, mainly in the epoxy casting insulation.
Discharge volume changes with the voltage, such as the gap
between the capacitor layer.

9. • Diagram 5
In the insulation of an electric motor, the discharge in the mica
insulation of the motor, and the amount of discharge varies with
the time and pressure of the copy.

10. • Diagram 6
The discharge occurs between the metal and the dielectric
surface ,which may be an air gap between the metal and the
medium, or the surface conductivity is uneven.

11. • Diagram 7
The surface of the metal electrode is discharged, and the
exposed metal surface and the medium are discharged. The air
bubbles between the metal and the medium or the air bubbles
in the lift may contain impurities such as metal or carbon.

12. • Diagram 8
A small part of a metal foil or metallized sheet in a capacitor can
move under an electric field.

13. • Diagram 9
Discharge of poor contact or suspended metal , and the test
circuit is not reliable connection. The pulse amplitude of the
discharge pulse is equal to the positive and negative half cycle of
the discharge. The oscilloscope can observe the discharge pulse
pairs, figure (a),(b) this is because the oscilloscope effect caused
by visual error caused by light.

14. • Diagram 10
Contact noise discharge, poor contact between metal or
semiconductor shielding layer. At the same time, the discharge
distribution of the noise is small on the two sides of the test
voltage. As the voltage increases, the noise discharge coverage
increases, as shown in figure (a). Motor carbon brush to form a
spark discharge may occur in this waveform figure (b).

15. • Diagram 11
The metal electrode discharge concentration field, the
amplitude distribution in the isometric peak voltage on both
sides, with the corona and air discharge in the same voltage, the
discharge AC voltage exists in both positive and negative half
weeks, but 2.5 weeks amplitude asymmetry, discharge pulse
amplitude larger in the positive half cycle, then discharge at high
potential, and vice versa in low potential. Similar in oil and gas.

16. • Diagram 12
Suspended discharge in oil insulation and creepage, pulse
number, the critical voltage, discharge is not stable. Sometimes
for a few seconds, or stop a few seconds without discharge. The
discharge is with large amplitude, but like the external random
disturbance which need combined with waveform and judge the
disturbance caused by the discharge of fluorescent lamp.

17. • Diagram 13
Discharge by fluorescent lamp.

18. • Diagram 14
The interference of silicon controlled rectifier is symmetrically
distributed, and sometimes it is a single pulse.

19. • Diagram 15
In the case of asynchronous induction motor, the response of
the motor is independent of the test voltage, which may be
caused by the large asynchronous motor, and may be caused by
the large load of the transformer. However, when the generator
is turned on for the test, the difference between the generator
frequency and the power supply of the system instrument will
cause the discharge display waveform to rotate.

20. • Diagram 16
Industrial high frequency equipment interference, industrial
high frequency equipment such as ultrasonic generator,
induction heater etc.

21. • Diagram 17
The interference of amplitude
modulated sine wave signal is
mainly caused by the high power
high frequency power amplification
or the radio emission or radiation
interference of the oscillator and
the interference of the radio
station.

22. • Diagram 18
corona discharge
Corona discharge occurs at the metal tip or
the edge of the electric field. The corona
discharge occurs only in the half of the test
voltage, and symmetrically distributed on
both sides of the voltage peak, figure (a). As
the voltage increases, the number of pulses
(width) increases symmetrically, as shown in
figure (b). If the discharge tip electrode is in a
high potential, the corona discharge occurs at
the negative half of the test voltage. If the tip
electrode is in the ground potential, the
discharge pulse appears in the positive half
cycle. On one electrode, the initial corona
appeared in 1.5 weeks, but when the voltage
rises above the initial voltage of many, in the
other 1.5 weeks will also appear in large
amplitude, discharge less pulses, as shown in
figure (c).

23. PD-Test-System

24. Know more information ,
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