On-line versus Off-line_Practical Aspects of Sensitive On-site PD Detection in Power Cables.pdf

7/27/2019 On-line versus Off-line_Practical Aspects of Sensitive On-site PD Detection in Power Cables.pdf

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onsite hv solutions is an international organization with a team of highly qualified specialists, providing modern on-site solutions for an optimal use & maintenance of medium and high-voltage components

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completely bridged, breakdown will occur [3, 20].As a result the detection of partial discharges is a well accepted tool for conditionassessment of new and service aged power cables. Many years of good experiences infactory PD testing of new manufactured components, have resulted in the implementation of PD detection also for on-site testing. In the last 15 years depending on the type of component, the network levels different solutions have been developed and implemented forPD testing and diagnosis [8-16].

In this contribution with regard to the on-site PD detection on power cables practical aspectswill be discussed. In particular, based on practical experiences the fundamental issues of PD

occurrence in power cables as well as the interpretation aspects will be mentioned. The goalof this contribution is to provide realistic information to utility maintenance engineersapplying PD diagnosis.

Introduction

Although some in the electricpower industry may notrealize, all extruded cablesystem owners, have relied onpartial discharge (PD) testtechnology to assure thereliability for decades. Mostexperts would agree that themanufacturing process andproduction PD testing of cablesystem components havebecome so well developed overthe last 40 years that the vastmajority of defects on newlyinstalled systems are not likelyto be due to the manufacturingprocess but rather toworkmanship. Many cableowners see the value in theproduction PD test and are using PD diagnostics in the field to compare the results withknown baseline factory tests. In fact, [29] states that if the cable system can be tested in thefield to show that its partial discharge level is comparable with that obtained in the factory

tests on the cable and accessories, it is the most convincing evidence that the cable systemis in excellent condition. Although the reason to use PD diagnostics in the field is a natural

External voltage source

Level: e.g. up to 3.0Uo

IEC 60060-3

IEEE 400

PD detection

IEC 60270 / IEC 885-3

IEEE 400.3

External voltage source

Level: e.g. up to 3.0Uo

IEC 60060-3

IEEE 400

Radio frequency (RF)PD detection

Radio frequency (RF)PD detection

Radio frequency (RF)PD detectionRadio frequency (RF)

PD detection

(a)

(b)

Figure 2: Principles of off-line PD detection methods for power cables;

a) Standardized and calibrated PD detection (conventional)

applicable for both factory testing and on-site testing of cableinsulation and cable accessories,

b) Not-standardized and not-calibrated PD detection(unconventional) for on-site testing of cable accessories. (IEC62478 under preparation, Cigre D1.33 brochure underpreparation).


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choice for many applications, it is the general experience that the metrics used to assure thefield results can be compared with the factory results are widely misunderstood and oftenoverlooked. To sum up the typical misunderstanding, one might say that not all PD tests arecreated equal. This is especially true when comparing the factory PD test results with typicalon-site (conventional) PD diagnostic test results and (unconventional) PD measurements.

Much research has been performed over the last 15 years to determine the frequencydependence of PD tests [3]. Research indicates that changing the frequency by more than anorder of magnitude can significantly change the apparent inception voltage of a PD site.This is a concern, as some off-line PD tests use frequencies outside the range of 20Hz up to

300Hz as recommended in [26, 27] which is used in factory and on-site tests. According toa literature search by the author, decreasing the test frequency by an order of magnitude canchange the apparent inception voltage in a typical range from 5 to 30% when comparedwith the factory PD test [3, 6, 7].

PD diagnosis of power cables

Many breakdowns in thepower cables are causedby damages due todigging activities [3]. Butstill, more than half of the breakdowns in thecable network are causedby internal fault in theinsulation systems of thecable network. Visualinspection of the disturbed components may give insight in the different types of breakdownrelated insulation defects. Based on these visual inspections, a list of defects in differentcomponents of cable network can be made, as reflected in [3, 23].For many years, withstand testing (AC and DC) was the only testing method applied in thepower cables network, but nowadays also PD testing has become an accepted method. Asshown in [3, 20, 23, 41], partial discharges (PD) are sensitive and until now they are the bestsymptoms of discharging weak spots (insulation defects, degradation processes) in the HVinsulation.

It follows hat there is a large diversity on insulation defects which may occur not only in theaccessories of a cable but also in the insulation. Moreover, it is know that PD inception in allthese defects depends on the local electric field enhancement. As a result with regard to

insulation defects different situations may occur in a cable system (insulation and/oraccessories).

50(60) line vol tage

Level: 1Uo

RF PD detection RF PD detection

RF PD detection RF PD detection

Figure 3: Principles of on-line PD detection methods for power cables; on-line:non-standardized and not calibrated PD measurement in cable accessories of cable section in service.


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(a)

(b)

(c)

Figure 4: Principle of PD pulse propagation in power cablesa) just after PD ignition, both pulses travel in the opposite direction [3]b) after reflection at the remote end, both pulses travel in the samedirection

c) example of localisation of PD source by analysing the PD wave timedifferences; he first detected pulse is the incident wave of the PD event(A), after which the reflected wave ( B ) occurs. The incident wave isreflected at the detection side of the cable and if not attenuated to noiselevel, it will appear as A . From the time difference between the incidentand the reflected wave, together with the calibrated propagation velocityv , the PD origin location can be calculated: x i =( l- vt)/2

1. Cable system is PD-free; starting at higher than 1.7Uo electric stresses e.g. > 3Uo PDmay start to ignite in accessories; in that case temporary over-stresses will not produceany PD inception in defects.

2. Cable system containdischarging defectswith PD inceptionvoltage (PDIV) higherthan 1Uo but lowerthan 1.7Uo; in that casedue to temporary AC or

switching over-voltagesthe PD developmentcan be ignited and inthe case of PDextinction voltage(PDEV) < Uo it can stayduring networkoperation.

3. Cable system containsdischarging defect with

PDIV< 1.0Uo; in thatcase in the cableinsulation and/or cableaccessories PDprocesses are activeduring networkoperation. Dependingon the type of defectand the local electricfield concentrationbesides knowledgeabout PD presence alsothe information aboutthe decrease of PDIV,increase of PDmagnitude are essentialto evaluate thedegradation process.

It was already shown many years ago [1] that the best way of PD detection as well as therecognition of different discharging defects is related to changes of the applied electric field,


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see figure 1. This interaction between PD inception voltages (PDIV), PD extinction voltage(PDEV), and PD magnitude at different voltage stresses provides more detailed picture aboutthe PD processes in different types of cable insulation defects. Obtaining this information inits turn is important in interpretation of discharging defects:

1. The level of PDIV as compared to the nominal service stress is of absolute relevance indetermining the degradation ration; e.g. discharging defect with if PDIV = 0.3Uo ismostly more severe that a defect with PDIV =0.9Uo [2, 3, 6].

2. To declare a power cable PD-free the PDEV has to be at least 1.3Uo [ANSI ICEA].3. Analyzing the increase of PD level and PD intensity in function of the applied voltage e.g.

between PDIV and 1.7Uo is a good indicator of defect severity [2, 3, 6].

Summarizing it can beconcluded that due to

- diversity of dischargingdefects,

- complexity of cable systems

for sensitive PD diagnosis

of power cables the voltagedependence of PDprocesses is important.

To detect off-line partialdischarges in power cablestwo principal methods canbe considered (figures 2and 3):1. off-line detection

where the test object is energized from external voltage sources [28] and with regard toPD detection a distinction can be made between standardized so called conventionaldetection method [30, 31] and the not-standardized so called unconventional the radiofrequency (RF) method,

2. on-line detection where the test object is energized from the network and with regard toPD detection the unconventional RF detection is applicable only.

In the following paragraphs relevant aspects of sensitive PD detection and the practicalimplications by using these methods for PD detection and localization are discussed.

Figure 5: PD location in power cables using conventional PD detection.Practical example of PD mapping as obtained using TDR analysis of detected PD signals. Using this analysis multiple PD activity in the cableinsulation and in cable accessories can be localized.


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Off-line PD detection and localisation of discharging defects in power cablesConventional PD detection (IEC60270 recomm endations)

The so-called off-line method has been introduced many years ago for factory testing. Sincea few years this method has also been in use for on-site testing of new and service agedpower cables.This method can only be applied on cables systems which are disconnected from thenetwork. The off-line PD detection consists of an external voltage source [28], preferablysinusoidal AC voltage as recommended in the standards for testing power cables of differentvoltage classes:

a) IEC60502 for testing medium voltage cables [42] b) IEC60840 for testing high voltage cables [26]c) IEC62067 for testing extra high voltage cables [27]

To detect PD in the power cable standardized circuit different standards can be applied [30,31, 33].

Performing off-line PD detection using conventional method covers an important step inassessing the sensitivity of the particular circuit. The purpose of this step is to determine thevalue in pC of the smallestPD signal detectable underthe test conditions.

Following the calibrationprocedure the final PDdetection will be performedin [pC] which is importantstep for comparisons

between on-site testingand the factory teststandards. Due to fullstandardization of the PDmeasurement process:measuring circuit,calibration procedures,signal processing thismethod is also called conventional.Moreover, applying the conventional PD detection provides PD detection and localisation of

discharging defects in the whole cable system: cable insulation and cable accessories.

0.00

20.00

40.00

60.00

80.00

0 100 200 300 400

Frequency [MHz]

A m p l

i t u d e [ u V ]

7 uV/pc

25 uV/pc

Figure 6 : Problematic of RF detection systems. The systems can not becalibrated: [pC] / V ratio depends on the characteristics of the wholecircuit and the selected RF frequency band. Sensitivity in [pC] of the circuithas to be estimated.


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With regard to PD site localisation similar to factory testing procedure can be applied, seefigure 4. In particular after a discharge process occurred in a cable on location X, e.g. cableaccessories or in the cable insulation, one PD pulse will travel towards the near cable end,the other pulse travels in the opposite direction, and will reflect on the remote open cableend. Finally, this pulse will also arrive at the near end of the cable. When the velocity of thePD pulses is known from standardized calibration, the location of the PD can be determinedby measuring the time lag between the first pulse and its reflection. To determine thevelocity a calibration measurement is used where a calibration pulse is injected at the nearcable end. The time difference between the original pulse and its reflection, together withthe known length L of the cable determines the velocity v. This technique is known as Time

Domain Reflectometry (TDR). With a devoted software tool for TDR, one can analyse PDmeasurements to identify partial discharges, their reflections and thus their locations alongthe whole power cables. To improve this process, the software tool uses a heuristicalgorithm, correlation and digital band-pass filtering [3, 34-36]. After this identificationprocess, it is possible to create location mappings of partial discharges, see figure 5. Byspecifying a list of joint locations, a convenient graphical overview over a cable is obtained.Applying TDR for PD site localisation the PD detection sensitivity depends on the cablelength and the characteristic HF impedance of the particular cable section [18].

Unconventional PD detection

(non-standardized)

Since a few years, in addition toconventional PD detection, forafter laying tests of new installedcable accessories the radiofrequency (RF) signal processing(using e.g. narrow or wide bandamplifiers, spectrum analyzers)

have been introduced, see Figure2b. This method is called nonconventional because at thismoment no guidelines orstandards are available to definethe calibration and themeasuring procedures. These RFdevices are able to couple out byinductive or capacitive sensorsthe PD signals from the cable

accessories and to measure the

Off-line and on-line

Cable length 320m

(a)

(b) (c)

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Cable length 320m

(a)

(b) (c)


Cable length 320m

(a)

(b) (c)


Cable length 320m

(a)

(b) (c)


Cable length 320m

(a)

(b) (c)

12

Figure 7: Off-line and on-line PD detection as performed on bothterminations 1 and 2 of a 320m long 10kV PILC power cable:

a) PD mapping as made on the basis of off-line conventional,PD detection [30, 31] as connected to termination 1,

b) and c) phase resolved pattern as detected , on-line usingunconventional PD detection method on both terminations 1and 2


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Test Sensitivity Assessment and Calibration

At present, in the authors experience, pC sensitivity assessment and calibration are perhapsthe most overlooked aspects of PD field tests. In the factory, manufacturers go to greatlengths, including the erection of electromagnetically shielded test rooms, to assure that thetest sensitivity meets the standard requirement. They also perform special calibrationsequences to assure minimal pC magnitude measurement error with their limited bandwidthPD equipment. PD testing in the field requires the use of ultra-high bandwidth detectionsystems [38]. The most up-to-date guide for PD testing in the field with such systems is[30]. According to [30] calibration and sensitivity assessment are critical since poor test

sensitivity and incorrect pC magnitude assessment commonly lead to faulty test results. Thefollowing text describes a sensitivity assessment and calibration procedure which will assurethat field tests are in compliance with [30] and comparable with factory test standards.

The practical implications of a proper pC sensitivity assessment and calibration for eachcable test are significant. For example, an inaccurate apparent charge calibration and/oroutdated measurement equipment can lead to errors in the range of one order of magnitude.


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Implications for unconventional PD Tests

Sensitivity assessment is an especially critical procedure when comparing unconventional PDtest results with factory PD tests. The unconventional PD test has an obviously apparentadvantage in the field in that it can be applied to the accessories directly and theelectromagnetic disturbances and noises from the external voltage sources (off-line) or formthe network (on-line) can be suppressed by choosing for PD detection VHF or UHF frequencyranges. However, a sensitivity assessment in [pC] according to [30, 38] can not be performeddue to differences in detection principles.

Therefore, since the calibration of unconventional detection can not be performed, thepossibility of a false negative is significant. If, for example, a radio frequency (RF) currenttransformer (CT) is placed in proximity to an energized joint or termination location, it is notpractical to inject a pulse on the conductor of the cable system and determine an accurateattenuation (or gain) factor to correlate the voltage measurements to pC values. Althoughthis example discusses the challenges of unconventional tests, [39] recommends that asensitivity assessment be performed prior to any PD diagnostic test in the field. Otherwise,without a proper sensitivity assessment of unconventional PD detection the standardsrequirements are not followed and the cable owner should be aware of the risk that the testmay not detect all PD activity.

Practical Experiences

Referring to systematic research as performed in the field using on-line PD detection [3, 17,23-25] in this chapter the practical aspects of conventional and unconventional PD detectionwill be discussed. In particular the major goal of this discussion is to point out the technicaldifferences and specific aspects of using both PD detection methods.

Applying conventional PD detection provides sensitive PD localisation in length of powercables up to several kilometres [18].

Based on the fact that starting from 1520 MHz the attenuation of PD energy frequencycontent increases heavily with the cable length, the sensitivity of RF detection systemsoperating at higher frequencies is limited to a few hundred metres. In figure 7 an example isshown of a very short cable (320m), where based on conventional off-line diagnosis PDactivity has been observed in a cable joint at 65m location. Based on unconventionaldetection as performed on both cable ends the signal reduction of 25% per 100m wasobserved. As a result the applied on-line detection on cable terminations will experience

problems in detecting PDs on cables longer than 0.5km.


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On-line

Cable length 1950m

(b)(a)

12On-line

Cable length 1950m

(b)(a)

12

Figure 9: On-line unconventional PD detection asperformed at 1Uo network voltage level on bothterminations 1 and 2 of a 1950m long 10kV PILCpower cable:

Off-line PD detectionaccording to IEC 60270

Cable length 1950m

(a)

(b) (c)

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Off-line PD detectionaccording to IEC 60270

Cable length 1950m

(a)

(b) (c)

12

Figure 8: Off-line conventional PD detection asperformed up to 1.7Uo on terminations 1 and 2 of a1950m long 10kV PILC power cable:

a) PD site mapping: it follows from this graphthat at the location 1100m PD activity up to7.5nC has been observed in the joint;

b) and c) PD phase resolved pattern

This observation is also confirmed by comparing conventional and unconventional detectionas applied to a cable with a typical length of 1950m (PILC insulation), figures 8 and 9. Usingconventional PD detection PD activity has been analysed up to 1.7Uo. At PDIV below 1Uo twoareas of PD activity have been localised.a) The 1 st one PD up to 3.5nC in the cable

insulation: 0m up to 600m where no PDconcentrations have been observed.

b) The 2 nd one up to 7.5nC (phase blue) hasbeen observed at the position of 1100m(joint location).

Analysing the phase resolved patterns asobserved at both terminations the PDpresence has been also confirmed.

As shown in figure 8 PD signal attenuationhas less influence on PD detectionsensitivity. It follows from the example infigure 8 that applying conventional detection

the PD in a power cable can be detected atboth cable ends in a similar way.

The same cable has also been tested usingan unconventional system, see figure 9. Atthe network voltage Uo at both terminationsthe EM disturbances have been estimatedand at the frequency with the highestsignal/noise ration the PD signals have beendetected and processed to phase resolvedpatterns. Taking into account the actuallength of this cable 1950m and the in figure9 shown attenuation effects of 25%/100mno sensitive PD detection in cable insulationand in cable joint can be explained.

Condition assessment of service aged power cables

On-site diagnostics are more and more important tools to support the asset management(AM) of power cable networks. In particular, based on actual condition status AM can


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Conclusions

In this contribution different aspects of on-site PD detection have been evaluated. Based onthis discussion the following can be concluded:

1) For on-site PD detection three methods are in use:

a) Off-line (cable section is disconnected and energised by an external voltage source): formany years established conventional detection where PD activity in cable insulation andcable accessories is measured in accordance to standards [30, 31, 33] and the PD

magnitude can be evaluated in [pC] and the PD sites in the cable insulation and cableaccessories can be localized.

b) Off-line (cable section is disconnected and energised by an external voltage source):unconventional where PD activity in cable accessories only is measured in V or mV andwhere sensitivity checks are necessary to demonstrate the effectiveness of the method.

c) On-line (cable section is connected to the network and energised by the line voltage): thePD detection uses unconventional detection methods of PD signals by connecting PDsensors to the cable accessories [21, 22].

2) Applying the above mentioned PD detection methods, several practical sensitivity aspectsof unconventional methods have to be taken into account. Due to diversity of measuringparameters unconventional method is more complex and does not provide measurements in[pC] but in [ V]. As a result to demonstrate the sensitivity of the system, applying non-conventional PD detection requests sensitivity checks are necessary.

References

[1] F.H. Kreuger, Partial discharge detection in high voltage equipment, book 1969Heywood, London, 1989, Butterworths, London

[2] B. Quak, Information strategy for decision support in maintaining high voltageinfrastructures, ISBN 978-90-8559-334-8, PhD thesis TU Delft, 2007

[3] F.J. Wester, Condition Assessment of Power Cables Using PD Diagnosis at Damped ACVoltages, ISBN 90-8559-019-1, PhD theses TU Delft, 2004.

[4] CIGRE TF 15/33.03.05: PD Detection System for GIS: Sensitivity Verification for the UHFMethod and the Acoustic Method, Electra No. 183, April 1999

[5] S. Meijer, P.D. Agoris, E. Gulski, P.P. Seitz, T. Hermans, L. Lamballais, SimultaneousCondition Assessment of Accessories of Power Cables using a Wireless VHF/UHF PDDetection System, Conference Proceedings CMD2006, Changwon, Korea, 2006.


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[6] R. Bodega, A. Cavanelli, P.H.F. Morshuis and F.J. Wester, The effect of voltage frequencyon partial discharge activity, 2002 Conference on Electrical Insulation and DielectricPhenomena, pp.685-689

[7] W. Hauschild, W. Schufft, R. Plath and K. Polster, "The Technique of AC On-Site Testing of HV Cables by Frequency-Tuned Resonant Test Systems ", CIGRE 2002, Paris, paper 33-304

[8] Gulski, E, Lemke, E, Gamlin, M, Gockenbach, E, Hauschild, W, Pultrum, E . Experiences inpartial discharge detection of distribution power cable systems. Cigre Electra, 2003, p34-43.

[9] E. Gulski, F.J. Wester, J.J. Smit, P.N. Seitz, M. Turner, Advanced PD Diagnosis of MV

Power Cables using Oscillating Wave Test System, IEEE EI Magazine March/April 2000,Vol. 16 No.2

[10] P.P. Seitz, B. Quak, E. Gulski, J.J. Smit, P. Cichecki, F. de Vries, F. Petzold, NovelMethod for On-site Testing and Diagnosis of Transmission Cables up to 250kV,Proceedings Jicable '07. 7th International Conference on Insulated Power Cables, France,Versailles, June 2007, paper 16

[11] M.S. Mashikian, G. Valdes and C. Katz, PD location as a cable operating tool, Jicable1995, 4th International Conference on Insulated Power Cables, Versailles, France, 1995.

[12] S. Boggs, Partial Discharge Part II: Detection Sensitivity, IEEE Electrical InsulationMagazine, Vol.6 No.5, Sep/Oct 1990, pp.35-42

[13] C. Aucourt, W. Boone, W. Kalkner, R.D. Naybour and F. Ombello, Recommendationsfor a New After Laying Test Method for High Voltage Extruded Cable Systems, CIGRE,1990, paper 21-105

[14] Martin D. Judd, Owen Farish: A Pulsed GTEM System for UHF Sensor Calibration, IEEETRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 47, NO. 4, AUGUST1998

[15] N. Ahmed and N. Srinivas, On-line Partial Discharge Detection in Cables, IEEETransactions on Dielectrics and Electrical Insulation, Vol5, Issue2, April 1998, pp.181-188

[16] B.R. Hamerling, F.J. Wester, E. Gulski, J.J. Smit and E.R.S. Groot, Fundamental aspectsof on-line PD measurements on distribution power cables IEEE 7th InternationalConference on Solid Dielectrics, 2001, pp.408-411

[17] E. Gulski, J.J. Smit, B. Quak, R. Jongen, P.P. Seitz, PD site location by time-domainreflectometry in mv power cable, Proceedings CMD 2006 International Conference onCondition Monitoring and Diagnosis 2-5 April, 2006, Changwon, Korea

[18] E Lemke et al. Practical aspects of the detection and localisation of partial dischagrsin power cabels, Cigre brochure 297

[19] C.G.A. Koreman et. al. Development of a new 380 kV double circuit XLPE insulatedcable system in The Netherlands, Cigr 2006, B1-107

[20] Gulski, E, Allan, D, Blackburn, TR, Contin, A, Gockenbach, E, Lemke, E, Lundgaard, L,Mizutani, T, Montanari, GC, Muhr, M, Okamoto, T, Phung, BT, Sedding, H, Breen, HJ van,


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Wester, FJ . Knowledge rules for partial discharge diagnosis in service (Cigr Brochures,226). Paris: Cigr

[21] C Walton, PD monitoring a critical tool for condition-based assessment, T&D 2003[22] C Smith, P. Fleming, M. Michel, Advances in contnous PD monitoring, Cired 2007,

paper 276[23] E. Gulski, F.J. Wester, W. Boone, N. van Schaik, E.F. Steennis, E.R.S. Groot, J. Pellis, B.J.

Grotenhuis, Knowledge Rules Support for CBM of Power Cable Circuits, CIGRE 2002Session, paper 104

[24] Wester, FJ, Gulski, E, Groot, ERS, Vliet, MC van . Sensitivity on on-line PD detection fordistribution power cables. In JJ Smit (Ed.), High voltage engineering; Proceedings of the

XIIIth international symposium on high voltage engineering (pp. 1-4). Rotterdam:Millpress (ISBN 90-77017-79-8).

[25] F.J. Wester, E. Gulski, J.J. Smit and E.R.S. Groot, Sensitivity Aspects of On-line PDDiagnosis of MV Power Cables, Cired 2003, 17th International Conference on ElectricityDistribution, Barcelona, Spain, 2003.

[26] IEC 60840 Power cables with extruded insulation and their accessories for ratedvoltages above 30 kV (Um = 36 kV) up to 150 kV (Um = 170 kV) Test methods andrequirements

[27] IEC 62067, Standard Power cables with extruded insulation and their accessories forrated voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV) - Test methods

and requirements.[28] IEC 60060-3 High Voltage test techniques Part 3: Definitions and requirements for

on-site testing[29] IEEE 400 Guide for Field Testing and Evaluation of the Insulation of Shielded Power

Cable Systems[30] IEEE 400.3 Guide for PD Testing of Shielded Power Cable Systems in a Field

Environment[31] IEC 60270 Measurement of partial discharges, 2000[32] EPRI Accessory Project 0420002[33] IEC885-3 High-voltage test techniques - Test methods for partial discharge

measurement of extruded power cables. IEC Publication 885-3, 1988.[34] Quak B., F. Wester, E. Gulski, J.J. Smit, P.N. Seitz; Advanced partial discharge site

location in power cable using numeric data processing. In: ICSD'01: Proceedings. 2001IEEE 7th International Conference on Solid Dielectrics (Eindhoven, June 25-29, 2001),IEEE, Piscataway, 2001, p. 416-419. ISBN: 0-7803-6352-3,

[35] Quak, B,Gulski, E,Smit, JJ,Wester, FJ Seitz, PN . PD site location in distribution powercables. In Marsden, H (Ed.), Conference record of the 2002 IEEE international symposiumon electrical insulation: Proceedings. (pp. 83-86). Piscataway: IEEE.

[36] Quak, B, Gulski, E, Wester, FJ, Seitz, PN . Wavelet analysis of PD in power cables. In JJ

Smit (Ed.), High voltage engineering; Proceedings of the XIIIth international symposiumon high voltage engineering (pp. 1-4). Rotterdam: Millpress (ISBN 90-77017-79-8).


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[37] P.D.Agoris, S.Meijer, E.Gulski, J.J.Smit, T.J.W.Hermans and L. Lamballais Sensitivitycheck for on-line VHF/UHF PD detection on Transmission cables, ConferenceProceedings ICPADM 2006, Denpasar, Indonesia, 2006.

[38] IEC 60270:2000, 3 rd edition (CEI/IEC 60270:2000), International Standard, High-voltage test techniques Partial Discharge measurements, 2000

[39] M. Muhr, T. Strehl, E. Gulski, K. Feser, E. Gockenbach, W. Hauschild, E. Lemke,Sensors and sensing used for non-conventional PD detection Proceedings 41 CIGRE 2006Session International Council on Large Electric Systems, 27 th August 1 st September,2006 Paris, France

[40] E. Gulski, P.P. Seitz, R. Bodega, Th. Hermans, On-site Testing and PD Diagnosis of HV

Power Cables, in Proceedings of 2008 IEEE International Symposium on ElectricalInsulation, Vancouver, Canada

[41] J. Densley, Ageing Mechanisms and Diagnostics for Power Cables An Overview,IEEE Electrical Insulation Magazine, Vol. 17 Nr. 1 pp14-21, Jan/Feb 2001

[42] IEC60502 Power cables with extruded insulation and their accessories for ratedvoltages from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) - Part 1: Cables for ratedvoltages of 1 kV (Um = 1,2 kV) and 3 kV (Um = 3,6 kV)

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On-line versus Off-line_Practical Aspects of Sensitive On-site PD Detection in Power Cables.pdf