Seminar for eight semester electrical engineering on Conventional and Un-Conventional Partial Discharge Detection Methods in High Voltage XLPE Cable Accessories

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Conventional and
Un-Conventional Partial Discharge
Detection Methods in High Voltage
XLPE Cable Accessories
Presented By:
Harshit Bhandari
8th
Sem Electrical
Guided by:
Prof. Harish Khyani

2. CONTENTS
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 What Is XLPE ?
 Problem with XLPE cables
 Detection of Faults
 Partial discharge
 What causes partial discharge ?
 Partial discharge detection methods
 Classification
 Conventional Method
Conclusion

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What is XLPE ?
 XLPE stands for Cross-linked Polyethylene cables .
These are most extensively used power cables for
transmission of High voltages
 They are frequently used for both overhead and
underground high voltage transmission system

4. XLPE Cable
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 Power cable system basically consists of cables
themselves and their accessories.
Cable accessories consist of joint and termination.
As the extensive application of Cross-linked
Polyethylene (XLPE) cable in power grid, power
accidents caused by insulation faults in cable
equipments are increasing constantly.

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 Insulation faults occur more often in cable accessories and
the existence of insulation faults, can lead internal partial
discharge (PD) to occur.
 The cable laying method is mainly concerned with
underground, which brings. problems on state testing and
fault localization in cable systems
 Therefore, how to judge the cable insulation
situation effectively and locate the fault site accurately is of
great practical significance

7. Partial Discharge
 Partial discharges are in general a consequence of local
electrical stress concentrations in the insulation or on the
surface of the insulation.
 Generally, such discharges appear as pulses having a
duration of
much less than 1 ps.
More continuous forms can, however, occur, such as the so-
called pulse-less discharges in
gaseous dielectrics.
For eg:- Corona Discharge
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9. What causes Partial Discharge?
 After installation or long time use, the insulation of cable or
accessories may include small voids and cavities, conductive
or insulating contaminants, or conductive protrusions in
different interfaces.
 The installation may also cause other defects like mechanical
cuts.
During the service the temperature variation and other
environmental stresses as well as electric filed and heating
due to load current may enlarge these defects, and partial
discharges may be incepted.
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10. These effects may also introduce cavities in originally sound cable
insulation or enlarge original micro voids.
 Partial discharge measurement methods are most important and
preferred and they have received much attention in recent years.
Cont…
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Partial discharge (PD) measurement methods are most
important and preferred in testing of underground high voltage
cables and they have received much attention in recent years.
 Apparent charge, partial discharge inception voltage as well
as number and distribution of PD pulses are most important
quantities for the determination of the insulation quality.
 Identification with certain PD patterns and localization of PD
are most important aspects.

12. Classification
 Partial discharge detection method can be classified into
two techniques
 Conventional and
 Un-conventional
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13. Conventional Method
 Conventional PD detection is a standardized method for PD
measurement as described in IEC 60270.
 This method based on measurement of apparent charge
displacement q in the leads of the sample. This charge is usually
expressed in Pico-Coulombs (pC)
Unconventional Method
 Un-conventional PD measurement is based on detection of
high frequency PD activities.

14. Conventional Method
Partial discharges that occur in the test object will produce
current or voltage pulses.
Output PD pulse magnitude is more or less a measure of the
PD current amplitude and not for the apparent charge
This method based on measurement of the charge
displacement q, expressed in (pC), from the pulses which
generated from partial discharge
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15.  The tests are carried out in the Extra High Voltage Research
Centre (EHVRC) PD Lab. In these PD measurements, 50Hz
continuous AC voltage is used as an energizing method.
 Using this PD detector several important parameters of PD
occurrence can be obtained such as:
• PD inception voltage (PDIV)
• PD magnitude in pC at PDIV
• PD magnitude as a function of voltage applied
• PD pattern
 The PD measurements have been carried out according to IEC
for the XLPE cable sample 220 kV -1600 mm2
with two different
type of joint and termination as shown in figure
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16. PD measurement is carried out in 2 minutes for each test
voltage. During this period three quantities are recorded:
The number of PD pulses,
The maximum value of PD magnitudes and
The average value of PD magnitudes
.
 These three quantities are plotted as a function of phase
angle of sinusoidal AC voltage. 1 and the PD measurements
results as shown in next Figure
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Phase-position quantities Hqmax
(φ), Hqn
(φ) and Hn
(φ)processed for discharges
at a test voltage 190 kV for 2 minutes

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3D distribution as obtained at 190 kV

19. PD pattern for a joint at 127 kV
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20. Unconventional Method
Un-conventional PD detection is used to provide result with
suppressed noise or high signal to noise ratio.
Basically there are two main methods,
High Frequency/Very High Frequency/ Ultra High Frequency (HF/
VHF/ UHF)
Acoustic method.
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21. Fault Detection
in Cable
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Fault Detection in Underground
cable

22. This methods use HFCT (High Frequency Current Transformer).
Using ultrasonic detector acoustic waves due to partial discharge are
detected .
This method does not requires any testing lab or heavy equipments
On-site detection of faults can be done easily with a semi skilled
person
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Unconventional Method
CB Link with mounted three
HFCT (PD Sensor)

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25. Query??
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