ensaios em alta tensão e diagnósticos de cabos s506
TRANSCRIPT
Energy Cables and Systems - Utilities
High Voltage Tests and Diagnostics in Cables
Pietro Corsaro – PIRELLIGianCarlo Montanari – University of Bologna
Energy Cables and Systems - Utilities
Contents
• European Scenarios
• Overview on measuring technique
• Conclusions
• Case Study
Energy Cables and Systems - Utilities
European Scenarios
Various approach within Europe, due to:
• Adoption of different testing standard:–Quality insurance approach;–High Stress Test;– IEC Standards.
Energy Cables and Systems - Utilities
European ScenariosFrance
• Power systems and installation condition highly standardized.
• Few installers qualified by EdF.• Extremely long qualification process.• Installed Systems are therefore
considered a priori failure proof.• EdF therefore does not see the need of
field tests.
Energy Cables and Systems - Utilities
European ScenariosThe Netherlands - Germany
Cables and accessories are factory tested at high voltage level
Vtest = 2.5*U0
Customers do not feel the need of any further test due to the high test level.
Energy Cables and Systems - Utilities
European Scenarios Spain
- After-Installation test in agreement with IEC standard (withstand test 1 hour/off-line);
- Increasing demand of PD monitoring from major utilities due to contingency:– Abnormal failure rate in the last year with
consequent increased interest of utilities in preventive diagnostic.
Energy Cables and Systems - Utilities
European ScenariosItaly
–After-Installation test in agreement with IEC standard (withstand test 1 hour/off-line);
– Increasing demand of accessories with embedded PD sensors (from 275 kV and higher) for new systems.
– Increasing demand of PD monitoring at commissioning stage and after repair.
Energy Cables and Systems - Utilities
Pirelli-TechImp Cooperation
In 1999 Pirelli started a collaboration with University of Bologna / TechImp to develop PD sensors and testing techniques on power transmission systems, particularly focused on accessories, to provide reliable information for Condition Based Maintenance.
Energy Cables and Systems - Utilities
Pirelli-TechImp CooperationMain outputs
A wide range of PD sources has beencharacterized for testing reference:–Cavity–Misalignment–Protrusion–…
Thanks to Pirelli cable expertise and TechImp technological know-how.
Energy Cables and Systems - Utilities
Pirelli-TechImp CooperationMain outputs
A number of sensors has been developed:–HFCT– Inductive Clamps–Capacitive embedded
to be capable to test in reliable way both new and existing installations
Energy Cables and Systems - Utilities
Detectable defects
All those non conformities causing an high electrical gradient and lack of material and consequent partial discharge:– Air gap– Not-compressed cuts– Semi-conductive elements mispositioning– Electrical trees– Protrusion– …
Energy Cables and Systems - Utilities
PD: Testing method
Main difference on voltage test source:• ON LINE: System under test is
energized by means of the grid
• OFF LINE: System under test isenergized by means of mobile resonant test set.
Energy Cables and Systems - Utilities
PD: Testing method - Pro & ConsOff-Line On-Line
Potential problem on the grid in case of failure
Induced noise from the grid
Induced noise from adjacent phase
Test Voltage level
Released power in case of failure
Costs
Energy Cables and Systems - Utilities
Mobile Test Sets Fleet
2 x150 kV
220 kV – 440 kV50 kV
100 kV
260 kV260 kV – In progress
160 kV
Energy Cables and Systems - Utilities
Testing Procedure
–If power system does not have embedded sensors, external sensors are applied on it;
–Sensors are calibrated;–The system is then energized @ no
load;–PD activity, if any, can be then
monitored on one or more accessories at the same time.
Energy Cables and Systems - Utilities
PD: SENSORSHFCT
Can be used in the earthing connection of the termination Can be used with LINK BOXGood sensitivityObject measured has to be sectionalised (can not be used on stright joint)
INDUCTIVE CLAMP A.C.M.S. (Around Cable Metallic Sheath)No limit in application (need just the cable)Easy to be appliedLow sensitvity
INDUCTIVE CLAMP U.C.M.S. (Under Cable Metallic Sheath)No limit in application (need just the cable)Can be embedded during the accessory assemblingGood sensitivityThe cable metallic sheath has to be cut
CAPACITIVE “EMBEDDED”Very High sensitivity PD Located immediatelyCan be applied ONLY during the accessory assembling
Energy Cables and Systems - Utilities
PD: Sensors Sensitivity
Sensitivity
HFCT
UCMS
ACMS
Embedded Capacitive
Energy Cables and Systems - Utilities
PD: embedded capacitive sensor
Energy Cables and Systems - Utilities
PD: embedded capacitive sensor
Energy Cables and Systems - Utilities
Testing Procedure
Feasibility of on-line or off-line energisation depends on the sensors used.
It is not technically correct to guarantee a priori a sensitivity level for on-site monitoring applicable to every installed system.
Sensitivity level for on-site measurement must be defined case by case
Energy Cables and Systems - Utilities
PD: METHODS“JUST A CHECK”
Can use the earthing connection of the terminationMeasurements performed only from the terminationNot applicable to Long Link
SEQUENTIALCan use LINK BOXCan be applied to OLD link without any problemsBreakdown can happen without any PD evidence on jointnot “on measurement”
SIMULTANEOUSAll the accessories measured in “ONE SHOT”PD Location easiestNO data “LOST”On old link can be used only with Inductive or embeddedSensors
MONITORINGGive an evaluation of the PD PATTERN TRENDVery helpful for condition base maintenanceCan be used only with Inductive or embedded Sensors
Energy Cables and Systems - Utilities
Pirelli-TechImpHow we act
We are able to provide an optimised configuration for PD testing:
– Mobile test-set world-wide (to avoid influence to/from the grid);
– Sensors for PD detection with ultra broad band frequency acquisition
– Acquisition tool capable to manage a large amount of data.
– Professional data analysis for reliable condition assessment.
Energy Cables and Systems - Utilities
PD MEASUREMENTS
2451
70
150 152
300
0
50
100
150
200
250
300
Tota
l leng
th o
f cab
les (k
m)
Num
ber o
f acc
esso
ries
2002 2003 2004 (first6 months)
Year
Partial Discharge MeasurementOn Site Activity: 2002÷2004
Cable lengthaccessories
Energy Cables and Systems - Utilities
PD MEASUREMENTS
0
10
20
30
40
50
60
70
80
Total
leng
th of
cable
s (km
)
2002 2003 2004 (first 6months)
Year
Partial Discharge MeasurementsOn Site Activity: 2002÷2004
< 150 kV220 kV400 kV
Energy Cables and Systems - Utilities
In SummaryBest results in diagnostics for HV systems
are obtained by:energizing the power system with mobile test-set (off-line method) for both withstand test and PD measurement;Using PD measurement to detect a wide range of defect undetectable with other testing methods;Performing PD measurement at every single accessory;Performing PD using capacitive embedded sensors;
Energy Cables and Systems - Utilities
Cases StudyTechnical notes
and Real Application
OfPD measurements for Power System
condition assessment