High voltage switchgear charged detection

1. High Voltage Switchgear Charged Detection
Himalayal Co.,Ltd

2. 1.Damage of partial discharge
Partial discharge can lead to the deterioration of the insulation
condition of the medium and high voltage equipment. No test or
maintenance will cause the equipment failure. In many cases, the
accident occurs after the switch operation, which poses a great
risk to the safety of the operator.
Partial discharge is caused by the early insulation failure of
middle and high voltage, which is now regarded as the best early
indication of the reduction of insulation, providing an early
warning for the failure of insulation.

3. What is partial discharge?
Partial discharge is refers to the electrical equipment insulation
structure of a certain area in discharge. The discharge is
insulation structure was destroyed in the area, the main
insulation is not the occurrence breakdown, but if the long-term
existence of partial discharge, under certain conditions which can
cause the loss of insulated electrical strength of the main
equipment and damage. If insulation structure of local electric
field is higher (field intensity distribution), or manufacturing
process is not perfect. In the operation of the organic matter
decomposition, insulation of solid insulation by the mechanical
force cracking reason forming defects, such as running in these
areas is prone to insulation breakdown and partial discharge.

4. What is partial discharge?
 In addition to the sharp edges of the metal conductor (or
semiconductor) electrode, or the insulating layer with different
characteristics, it is also where the local discharge can occur
easily. Partial discharge is only partial puncture, but each
discharge has a slight damage to the insulation.
 The cause of the damage: The partial temperature rises in the
medium, the oxidation accelerates, and the electrical and
mechanical properties of the dielectric are reduced. The
charged particles hit the medium and cut off the molecular
structure. The reactive gas produced by discharge can react
with the medium and cause the dielectric property to
deteriorate. In order to ensure the reliability of electrical
equipment in operation, no partial discharge is allowed in
insulation, or only slight partial discharge is allowed.

5. What is partial discharge?
 Partial discharge is the electrical discharge that does
not make the electrode completely short. The
magnitude of the discharge is relatively small. But it
can cause the insulation to decline continuously and
cause the most common failures 。

6. Why do partial discharge online testing?
 According to IEC, IEEE and GB, partial discharge measurement
is an important method for evaluating the insulation quality of
electrical equipment.
 According to the IEEE recommended on-line partial discharge
test is the only effective insulation online experiment, the
partial discharge can be correctly identified, such as pollution,
thermal cracking, insulation defects caused by manufacturing
defect and so on.
 The on-line insulation test of the high voltage device can make
an early warning to the insulation fault, so that the
maintenance and maintenance of the planned downtime is
reasonable.

7. The type of partial discharge
1.Surface discharge
2.The corona discharge
3.The cavitation discharge

8. 1.Surface discharge
What is Surface discharge?
1) Surface discharge is caused by dirt, moisture and dust on the
surface of the insulator.
2) The pollutant causes high electric field stress around the
insulator and is distributed along the insulation surface.
3) The surface of an insulator becomes a conductive area during
the accumulation of long periods of pollutants.
4) When a continuous surface discharge occurs, the insulation
deteriorates.
5) The surface discharge value is higher to other discharge
values.

10. 2.The corona discharge
The cause of corona discharge
1) corona discharge usually occurs around the tip of the
electrode and is usually discharged at the tip of the high voltage
electrical equipment
2)When the electric field around the tip electrode is more than
30KV/cm or higher, a corona discharge will occur.

12. 3. Cavitation discharge
 The cause of cavitation discharge
1) Cavitation discharge occurs in the air gap between insulation
materials.
2) The air gap in the insulating material is usually caused by the
production of the product, the process of the installation
process and the ageing and degradation of insulation.
3)The air gap in the insulating material will cause a partial
insulation breakdown of the insulating material, resulting in
the whole insulation breakdown.

15. 4.What is the earth wave?
 When partial discharge activity in the high voltage switchgear
insulation, it produces radio frequency range of the
electromagnetic wave, it can only through an opening in a
metal case, from leaking to the outside surface from the
switchgear. These open holes may be the clearance of the
casing or seal washer or other insulation. When the
electromagnetic wave reaches the outer surface of the open
cabinet, it creates transient voltages on the grounding metal
shell. Transient voltage (TEV) in a range of several millivolts to
several volts, has a very short period of time, and only a few
nanoseconds rise. It is possible to put the probe outside the
open cabinet when the open ark is working, and use this non-
invasive way to detect the local discharge activity of the switch
cabinet.

16. Himalayal Corporation Limited
 ADD: 503, 1#, New Jinqiao RD,SHANGHAI, 201206CHINA
 TEL: +86 21 6101 6212
 FAX: +86 21 6101 6213
 Email: info@himalayal.com
 http://www.himalayal.com