This document discusses voltage testing and partial discharge measurement techniques for power cable accessories. It provides: 1) An overview of the objective to compare cable testing best practices and determine cable defects using partial discharge methods. 2) A description of an ACRF test system used, including its components like an HV reactor, control unit, and voltage divider. 3) Details on partial discharge measurement methods like using high frequency current transformers and coupling capacitors to detect discharges in cables. 4) The conclusion that resonant testing between 20-300Hz along with partial discharge detection reduces risks from cable systems after installation by locating faults.

1. EE-471 HIGH VOLTAGE ENGINEERING
Voltage Testing & Partial Discharge
Measurement For Power Cable Accessories
PRESENTED BY : SYED ATIF CHISHTI
SUBMITEDTO : PROF DOC :BULENT BILIR
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2. PRESENTATION SEQUENCE
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 OBECTIVE
 INTRODUCTION
 ACTESTAFTER INSTALLATION
 ACRF TEST SYSTEM
 SCHEMATIC DIAGRAM OFTEST SYSTEM
 PARALLEL OPERATION MODE OFTEST SYSTEM
 PARTIAL DISCHARGE METHODS & PRINCIPLE.
 DISCUSSION & CONCLUSION.
OBJECTIVE :
 To compare best practices for cable testing.
 Predictive diagnostic programs to aging cable.
 To determine the faulty joints cable defects

3. INTRODUCTION
 Using Frequency tuned resonance
Test system (20-300 Hz) to calculate
PD measurement.
 PD measurement method are
necessary to trace defect and
insulation of cable.
 Voltage testing provide information
about defect in the insulation is
dangerous or not for later operation.
 Calibration is done through PD
calibrator on the cable termination.
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 Power Cables importance in
Transmission & Distribution
system
 Consist of :
 Cable
 Joint
 Termination
 Identification & Localization of
partial discharge.

4. AC TEST AFTER INSTALLATION
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 Follow the international standards IEC 60840 and IEC
62067 for testing of Power cable insulation and their
accessories.
 Apply : sinusoidal waveform, frequency: 20 and 300 Hz,
voltage applied for 1.7 U0 /1 hour

5. Methods of Voltage Generated
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 By a reactor with variable inductance and fixed excitation
frequency 50 or 60 Hz (ACRL) test system.
 By a reactor with fixed inductance and frequency tuned
voltage excitation (ACRF) test systems.

6. ACRF TEST SYSTEM
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 HV Reactor
 ExciterTransformer
 Control Unit
 Feeding Unit
 Blocking Impedance
 Voltage Divider & Software
 Frequency Convertor + Protection Impedance.

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SCHEMATIC DIAGRAM OF TEST
SYSTEM

8. PARALLEL OPERATION MODE OF TEST
SYSTEM
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9. OPERATING RANGE OF THE RESONANT TEST
SYSTEM (ACRF)
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10. PARTIAL DISCHARGE
 Partial discharges are a sensitive measure of local electrical
stress and the measurement is often used as a quality check of
the insulation.
Cable has small voids, cavities, insulating contaminant
conductive protrusions in different interfaces or mechanical cuts.
 Erosion by ion bombardment and chemical effects gradually
change small defects to electrical trees with consequent final
breakdown.
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11. METHODS OF PD MEASUREMENTS
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 HIGH FREQUENCY CURRENTTRANSFORMER
HFCT method at cross bonding box for 220 kV or earth wire of 66 kV for XLPE cable
systems Showed high sensitivity and calibration is possible using PD calibrator on the
cable terminations.
 COUPLING CAPACITOR
PD detection of high frequency signal generated from PD activities. Measurement by use of
a coupling capacitor is physically limited to a maximum detectable cable length of
approximately 2 km, depending on cable parameters and PD background noise.

12. WORKING PRINCIPLE
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 The sensitivity of the partial discharge detector has to be modified until the
detector shows the calibration charge.
 For 220 kV, PD measurements carried out during HV tests, using a test
sequence providing several increase the voltage in steps of 127 Kv (U0) and take
a PD-measurement recording during 1 minute and afterwards increase the voltage in
further steps until 216 kV
 At each step note the measured PD value.
 Once reaching 216 kV leave this voltage applied for 1 hour and observes if
there is a change in the recorded PD pattern and value.
 While ramp the test voltage down, take another PD measurement for 1 minute
at 127 kV.

13. Time characteristic of the 216 kV
Voltage test
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14. PARTIAL DISCHARGE
MEASUREMENT
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 Internal sensors integrated in each accessory or external
sensors HFCT placed inside bonding link boxes.
 The PD sensitivity using HFCT the central measuring
frequency is recommended is to lie between 2 MHz and 10
MHz in a flat zone of the frequency spectrum.

15. CROSS BONDING LINKS WITH MOUNTED THREE
HFCT SENSORS FOR PD
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 Test carried out on two cables having specification
1x3x1600 mm2,CU /XLPE/LEAD/HDPE ,220 kV with approximately 13 km long,19
joints/phase, 3 straight joint box and 16 insulated joint box which are divided into two
sections by means of joints and it is terminated by composite three outdoor and three
GIS sealing ends per circuit.
 The result was a resonant frequency of 35.53 Hz for test voltage 216 kV.
 Inject a calibration pulse with known quantity of charge at the outdoor system
termination (i.e., between HV and ground terminals), the sensitivity of the PD detector
has to be modified until the detector shows the calibration charge.
 PD pulses occur in very short time, the width and rise time of the pulses are in the
nanosecond region. Consequently, PD pulses with energy frequency up to hundred
MHZ are generated these PD pulses will travel through the cable earth conductor and
finally can be recorded by the sensors
TEST RESULT & DISCUSSION

17. PARTIAL DISCHARGE RESULTS FOR
CIRCUIT 1 & 2
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18. variation OF PC pattern during
PD measurement
PD measurement OF pattern
with some noise
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EXAMPLE OF JOINT FAILURE DURING
WITH STAND TEST BY USING RESONANT TEST
SYSTEM

20. CONCLUSION
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 After installation of cable , test for HV/EHV XLPE cables system
by using resonant test system of (20 Hz -300 Hz) combined with
PD detection is performed by using HFCT sensors at each cross
bonding (CB) link boxes reduces the risk from the service.
 After detecting the location of fault and repair the cables and
their accessories was done exactly in the same place given good
results.
 The experiences also show that the test voltage with U0 for 24 h
is not feasible for incidence of failure after the test could be
occurred.

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