Kinectrics Presentation - HV Cable Testing

8/17/2019 Kinectrics Presentation - HV Cable Testing

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Copyright © 2014 Kinectrics Inc. All rights reserved. Kinectrics - Proprietary and ConfidentialPage 1

life cycle management solutions

GENERATING SUCCESS --- FOR 100 YEARS

Transm iss ion & Dis t r ibu t ion Techno logies

Hassan Youn esTransm iss ion Cable & Subs ta t ions ,Service Line L ead 2014 / 2015


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GENERATING SUCCESS --- FOR 100 YEARS

Transmission Cable Testing

http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=eLL5upnu2bPAVM&tbnid=XjqDWk_bIVmy4M:&ved=0CAUQjRw&url=http://www.ehvpower.com/projects/central-and-south-america/panama/&ei=BpuRU73DBa-lsATY8IBA&bvm=bv.68445247,d.b2k&psig=AFQjCNG-CU9LeMjySUXqstPV-YU_tYKWaQ&ust=1402137622571341


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Testing Philosophy / Why Test ?

Manufacturing

D a m a g e

D u r i n g

T r a n s p o r t

I n s

t a l l a

t i o n

M i s t a

k e s

M e

t h o

d s

/ E x p e r

i e n c e

E f f e c

t o

f A g i n g

E n v

i r o n m e n t

A c c e p

t a n c e

T e s

t i n g

C o m m

i s s

i o n i n g

M a

i n t e n a n c e

T e s

t i n g

Transportation Installation

F a c

t o r y

T y p e

T e s

t i n g Tested at 50/60 Hz.

Operation @ 50/60 Hz.

Power Cable Life Cycle

M a n u

f a c

t u r i n g

M i s t a k e s

R a w

M a

t e r i a

l s

R e p a

i r s

/ U p g r a

d e


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24 Hr. Soak Test DC Hipot TestAC Hipot TestVLF Test (0.1Hz)VLF CR Test (0.1Hz)DAC /OSW Test

Partial Discharge TestDielectric Spectroscopy

Basic tests available in the industryAfter Laying Field Tests

4


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Test methods

Soak Test MethodEnergize Cable System at Uo for 24 or 48 hours

Withstand Testing (Hipot)DC HiPot Testing –

Not for XPLE type cable systems (Space Charge).

AC HiPot Testing – Recommended in combination with PD monitoring (IEC Standard).

VLF Testing – Limited to Transmission cables up to 69KV (IEEE 400.2).Very limited data on VLF withstand and nearly no data on PD diagnosis.

Diagnostic TestingDamped AC or Oscillating WavePartial Discharge Testing


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Factory Testing at Kinectrics’ Laboratory Type Test

Electrical and Material Testing is performed per

IEC 60840, 62067, 60229, 230, IEEE 404, IEEE48, AEIC, and ICEA standards.

Kinect r ics per form s an independent th i rdpar ty Labora tory tes t ing for mo st cablemanufacturers :

Electrical TestingPartial DischargeTan Delta at Uo @ 100ºCHeating Cycle @ 2Uo for 20 days / 100ºC PartialDischarge at Ambient & 100ºCSwitching Impulse @ 100ºCLightning Impulse at 100ºC

AC Withstand

Resistance of semi-conducting screen

PD Sensitivity of 5pC or better for cable sectionsand accessories

No PD activity should be detected above 1.5Uo Joint

4 3 2

CableSection

CableTermination

1

H V S o u r c e

Grounding

0

CableSection

CableTermination

MeasurementLocation

HV Divider +PD Sensor

V ref

C

HV

C LV

V PD

JointCable

Section


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Electrical testing is performed Onsite by

Kinectrics in compliance with various testingstandards.

Kinec t r i cs pe r forms an independentth i rd par ty o ns i t e t e s t ing se rv icewor ldwide :

AC Withstand with Partial DischargeOnline Partial DischargeTan Delta at UoDielectric SpectroscopySurge Voltage Limiter testing (SVL)Cross bonding – contact resistance testingSheath potential testingPositive and Zero sequence impedancetesting

Onsite Testing(Com miss ioning & Maintenance Tes t ing)

PD Sensitivity of 10pC or better for cable sections and 5pC or better for accessories.

No PD activity should be detected at 1.5 Uo However,

Some clients require NO PD activity at 1.7Uo (During Hipot).


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AC Hipot (Withstand) using Resonance Circuit

ProsComparable to factory testsProven test methodology withdecades of experienceEffective in identifying life limitingdefectsCan perform PD testing during

AC HiPot testsGets ‘soft’ failure so meaningfulforensics can be performed

ConsRequires heavy equipmentRequire Technical expertise

Compliant with IEC 60840 and IEC 62067 international testing standardsTesting at near power frequency from 20 Hz to 300 HzTest level range from 1.25Uo to 2Uo but typically 1.7Uo.Over voltage applied for 60 minute or by Cycles.

Accepted commissioning test methodology for HV & EHV


9/56Copyright © 2014 Kinectrics Inc. All rights reserved. Kinectrics - Proprietary and ConfidentialPage 9


Typical single RTS Circuit configuration 260KV / 83 A with an external power supply generator

External filter divider is required to besetup in the field to protect the RTS,measure applied voltage and filter outunwanted P from the RTS .

Outputs pure sinusoidal waveform at a Frequency 20 to 300 Hz.




Typical single RTS system configuration 260KV / 83 A with an external power supply generator




Resonance Test System units in Parallel260KV / 249A for testing long cables




Resonance Test System 4 unit configuration520KV / 166A for testing long cables

Four RTS units in series & parallelconfiguration to perform testing up to520KV test voltage and 166 A of load.




Multiplexed Daisy Chain System

Daisy Chained Multiplexer Systems, A Kinectrics designed partial

discharge monitoring multiplexer system that allows us to connect a largenumber of cable joints into a network that can be remotely andindividually controlled via fiber optics from test site.

This product is used exclusively by Kinectrics to offer in lieu of the Jointhopping which requires many extra activities such as additional staff,traffic diversion, police escort, barricades, etc … This translates to a moreexpensive process.


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Sheath Sensors

Partial Discharge Sheath Sensors: A Kinectrics Designed Sheath type

sensor to be used on cable system where cable joints have no crossbond links for a standard type HFCT (High Frequency CurrentTransformer type PD sensor).

Sheath Sensors are typically used near a joint or before and after a jointto detect PD activity with high accuracy in or near the accessory.

Sheath (Voltage) PD Sensor




Sheath Sensor (Voltage)

Sheath sensors are a unique type sensor designed and built by Kinectricsfor special straight thru joints without bond lead. They are designed tosense voltage variations in the sheath.

Typically use ultra wideband PD monitors

10kHz to 30 MHz10kHz to 50 MHz10kHz to 400 MHz




High Frequency CT’s.

Kinectrics ’ designed HFCT partial discharge

sensors to be utilized in cable systems where cable joints have exposed and accessible cross bondlinks.

Higher frequency bandwidth compared to othersensors on the market provides a much betteroverall performance.

HFCT PD Sensor




Power Frequency CT’s.

PFCT Power Frequency CurrentTransformer

Kinectrics uses power frequency partialdischarge sensors to be utilized in cablesystems where online Partial Dischargesensitivity is used to synchronize withapplied voltage zero crossing. Thesesensors are left on cable systems for

future online PD monitoring.




Joint

4 3 2

CableSection

CableTermination

1

HV Source

Grounding

0

CableSection

CableTermination

MeasurementLocation

HV Divider +PD SensorVref

CHV

CLV

VPD

JointCable

Section

Inject 2,000 pC

Sensitivity Assessment




Typical Installation Problems

Transportation Damage 2%o Improper Liftingo Improper Transportationo Improper Reel Orientationo Manufacturing

Pulling Damage 10%o Dents in sheatho Exceeding bending radiuso High Pulling Tensiono Torqueing cable

Workmanship 88%o Protrusions/dents at inner conductoro Knife cutso Lack of cleanlinesso Flat spots

o Misalignment of componentso Inadequate use of materialso Lack of Experience




Variable Frequency Resonance Test System (RTS)22MVA @ 83A / 260KV / 1650nF (20-300Hz)

Control Room

Exciting Transformer

Reactor

HV Filter

Tarp System

LC f

2

1

Meets IEC 60840 & 62067 standards for cable testing (up to 500KV cable class).

RTS testing combined with Partial Discharge monitoring, provides the ultimatediagnostic tools in the industry to determine the health condition of your cable system.




Applied Test Typical Voltage Profile

60 minutes Hipot – Typically at 1.7Uo

PD monitoring

Voltage Dwell & Frequency Sweeps (1Mhz to 20Mhz)




IEC 60840 Standard, for HV Cable (30KV to 150KV):




IEC 62067 Standard, for EHV Cable (150KV to 500KV)

226 KV

282 KV

339 KV

491 KV

491 KV

Requested Test Voltage is typically 1.7Uo of the HIGHEST voltage rating in a cable class

133 KV

166 KV

203 KV

289 KV

289 KV




Soak Test (24 Hr. or 48 Hr. at Uo)

Allowed by some specifications as an alternative testNo test equipment required: quick and cheap, but how effective ?Low Risk of a failure during testNo overvoltage stress, thus no accelerated ageing of defects

Can be combined with PD diagnosisKinectrics successfully performed PD diagnosis during 24 hr Soaktest on a Cable System in Wisconsin for ATC.Not a diagnostic tool

Competing Technologies


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Oscillating Wave / Damped AC / DAC / OSW

OSW / DAC Circuit

IEEE 400.4 Guide for Field testing of Shielded PowerCable Systems.

50+ Excitation ShotsNot a continuous AC test20 to 300 Hz. OscillationsMeets & Exceeds 1.7 Uo test voltage levels

Applicable for withstand testing with PD diagnosis Applicable for cable class 5KV and higher

Competing Technologies


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Long DC Charging Time up to 100s for each shot.Oscillations occur at 20-300Hz. for 10ms per shot.High risk of spare charges due to DC charging, especially in HV/EHV Cables.

Damping factor ~ 5% to 40%, capacitance dependent.50+ excitations yield ~ 2 seconds of AC stress, not a suitable withstand test.Risk of small but critical voids do not initiate PD activity due to inadequate AC Stress, thus weakpoints may not be detected.

IEEE 400.4 is a Guide – NOT AN IEC STANDARD , thus DAC is not a viable withstand solution.

Oscillating Wave / Damped AC / DAC / OSWCompeting Technologies


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IEEE 400.2 Standard for cable class 69KV and below, used for lower voltage cable

class.Hipotential Testing – very few zero crossings compared to 20 to 300 Hz test.Possible formation of space charges on HV and EHV class cableVery limited potential of electrical tree growth, thus requiring much longer test time.Portable with low power requirement, smaller test sets, however how effective on HV& EHV ?May be combined with PD or tan δ , not comparable to 20-300 Hz. test method.

VLF – Very Low Frequency (0.01 Hz. To 0.1 Hz.)Other Technologies


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Formation of Electrical TreesEffects of Frequency and Test Time on Tree Shape Formation.

Sinewave at 2 UoFew Branches / Less dischargeductsNote the long test time

Sinewave at 2 Uo@ 10 – 50 HzMore Branches / More dischargeductsLess test time

Sinewave at 2 Uo@ 100 – 500Hz.Numerous Branching / lots ofdischarge ducts

VL F

RTS

Sine wave @ 2Uo (0.1Hz to 500Hz)


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Time (hrs)# of PD pulses

20Hz 300Hz

VLF requires much longer test time interval until breakdownVLF shows significantly less PD pulses as compared to NPFVLF test time has to be active much longer to achieve same # of PD pulses as NPF

# of PD pulses collected at NPF is

at 1/3 of the VLF time

Total PD pulses collected @ Sine Wave 2Uo.From 0.1 Hz. (VLF) to 20-300 Hz. (NPF) test frequency


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What is Partial Discharge?

Partial Discharge measurement is a very important diagnostic tool in assessing theoverall health condition of the insulation in power cable systems.

IEC defines PD as: “ Localized electrical discharge that only par t ial ly br idges the insulation

between conductors and which can or cannot occur adjacent to a conductor .”

In XLPE

In OIL

In AIR


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Copyright © 2014 Kinectrics Inc. All rights reserved. Kinectrics - Proprietary and ConfidentialPage 34life cycle management solutions

Partial Discharge

PD is a Diagnostic tool to detect signs of distress in distributionand Transmission cable systems.PD gives us the opportunity to detect defects BEFORE failureCan be performed on-line or off-lineCan use multiple types of power supplies, we prefer NPF.

PD testing is a non destructive test to an insulation system.PD is typically measured during the Hipot test.PD is performed at near power frequency and at elevated voltagesto accelerate aging of defects

PD ACTIVITY RELATES DIRECTLY TO INSULATION INTEGRITY


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Partial Discharge (Equivalent Circuit)


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Partial Discharge

Electrical Field Conditions

-20

-15

-10

-5

0

5

10

15

20

0 45 90 135 180 225 270 315 360

Phase Angle

V o

l t a g e

/ E l e c

t r i c F i e l d

Appl. Voltage [kV]Background Field [kV/mm]Void Breakdown StrengthVoid Field [kV/mm]

InitialDischarge Return

Discharge SecondDischarge


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Terminal vs. Distributed PD measurements

Terminal PD MeasurementNo Joints

Distributed PD MeasurementJointed System


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Typical Partial Discharge Pattern

Phase Resolved PD Pattern (doble / Lemke, HPMT 03-06)


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PD Testing Online vs Offline

Off-Line

Requires cable system to bedisconnected

Guiding criteria is that the cablesystem should be PD free at thespecified test voltage

Requires external power source

Done at elevated voltages usuallyat 1.7Uo.

Measures PDIV, PDEV , PD level.

Localizes PD Source & Intensity

On-Line

Non-invasive testDone at rated voltage Uo

PDIV and PDEV cannot be measured Assess individual PD sourcesseparately

Often, multiple PD sources fromvarious types of HV equipment aredetected

Can only detect sources present atthe time of testing


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0.01

0.1

1

0 1000 2000 3000 4000 5000 6000 7000

Length [feet]

Corresponding Attenuation (Normalized)

PD Attenuation with Cable Length


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Water Tree Formation

High electrical field caused by voltage transients result in power dissipation in the micro

water channels that exist in the XLPE insulation. This raises the temperature of the waterand increases pressure in the water tree channel, generating cavities to support PD.

Water migration into the insulation leads to water trees which in turn decreases insulationresistance and increases leakage current

Water Trees form and with time convert to electrical trees producing partial discharge andultimately lead to failure

Insulation Failure Water Trees


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Insulation Shield

ElectricalTree Vented Water

Tree (VWT)

Water Trees (XLPE)

Lowers the AC breakdown voltageIncrease in dielectric loss TanDelta

Increased DC leakage currentCan only be detected via DielectricSpectroscopy ( Tan Delta at 0.01 to60 Hz. )


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Why test at 1.7Uo ?

0.00

0.25

0.50

0.75

1.00

0 .5 0 0 .6 0 0.7 0 0 .8 0 0 .9 0 1 .00 1 .1 0 1 .2 0 1 .3 0 1 .4 0 1 .5 0 1 .6 0 1 .7 0 1 .8 0 1 .90 2 .0 0

P e r c e n t i l e

Partial Discharge Inception Voltage (PDIV) [U 0]

Distribution of PDIV During HV Comm. Testing

0.90

(Constant PD Monitoring Only)

50% to 90% of PDEV occur at or above1.7Uo

Some go as high as 2Uo depending oncable class

IEC Standards 60840 & 62067 adopted 1.7Uo due to it’s higher confidence level and over30 years of testing experience; if PD source is present, it will ignite at or above 1.7Uo.

But wait, in what time frame……

Distribution of PDEV during Hipot Test


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0.00

0.25

0.50

0.75

1.00

0 10 20 30 40 50 60

P e r c e n t i l e

Time [minutes]

On-Set of PD During HV Commissioning Testing

0.90

Why test for 60 minutes ?

75% to 99% of the time PD ignites at orabove 20 minutes

Some increase test time depending ontest frequency, for 20Hz, test time is180 minutes.

IEC Standards 60840 & 62067 adopted 60 minutes test time due to it’s higherconfidence level and over 30 years of testing experience; if PD source is present, itwill ignite at or above 1.7Uo when applied between 25 min to 60 min.

(Constant PD Monitoring Only)


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Case Study – Feb. 2014 AC Hipot with Daisy Chained PD system

Using 2 RTS units in series to beable to successfully test and PDdiagnose a 345KV class cable.

* 4 major issues were found.


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345KV Cable System Tested at 1.7Uo with PD17 splices per phase (Feb 2014)

PD was detected at 339KV at Joint 6via PD sensor

Joint was replaced & retested, no PDpresent


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345KV Cable System Tested at 1.7Uo with PDXC Phase / Joint failed during testing (Feb 2014)

PD pulses started igniting a 318KV,then few seconds later the jointfailed.

Joint was replaced & retested


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345KV Cable System Tested at 1.7Uo with PDCascade System / Joint failed during testing (Mar 2014)


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138KV Cable System Tested at 1.7Uo with PDTermination showed PD activity near IGBT Pulse


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72KV Cable System Tested at 1.7Uo with PD6 Cables no splices per phase (Jun 2013)

PD was detected on all 3 phases near GIS terminationvia Kinectrics’ HFCT type PD sensor.

Cable section had to be replaced andretested to be PD Free


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72KV Cable System Tested at 1.7Uo with PD3 Cables no splices per phase (Mar 2013)

PD was detected on phase A open air termination viaKinectrics’ HFCT type PD sensor.

Orientation of PD Sensors allowed the location of thePD activity to be located – Note reversed polarity of Aphase.

All 3 phase were being tested simultaneously.

Workmanship issues while installing stress cone.

Termination had to bereplaced and retested tobe PD Free


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Sample of failures from 2012 - 2014

Test Date C a

b l e

C l a s s

T o t a

l

A c c e s s o r i e s

F a i l u r e s

F a i l u r e R a t e

December 2014 138 kV 18 1 5.5%

October 2014 230 12 1 8.3%

March 2014 138 kV 38 3 7.9%

February 2014 345 kV 102 4 3.9%June 2013 72 kV 48 4 8.3%

April 2013 115 kV 18 1 5.6%March 2013 72 kV 12 1 8.3%December 2012 138 kV 18 1 5.6%

December 2012 138 kV 18 1 5.6%

Totals: 284 17 5.99%

Selected few Jobs with actual failures due to Hipot and/or PD, shows a steadyfailure rate of 4% to 8% on the average – Failed components were replaced bycable manufacturers to ensure long term operation of PD free cable systems.


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Summary

Many IEC Studies and experiences prove a combination of AC HV

(Hipot) & PD is the Ultimate Diagnosis Tool in determining thehealth of underground cable systems.Test levels must be at 1.7Uo to provide higher confidence level thatall possible PD sources are addressed.Test duration likely need to be adjusted when testing at lowerfrequencies – Cigre ’ Workgroup B1.38 . Test Duration by cycles.Trends going towards constant monitoring via daisy chained PDSystems for commissioning testing.Testing with Near Power Frequency (20Hz. – 300 Hz.) @ 1.7Uosubjects the cable to similar stresses as operating frequency atelevated voltages to locate all possible PD sources, after all, thecable system will live the rest of it’s life at 50/60 Hz.


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Contact Information:

HASSAN YOUNESService Line LeaderTransmission Cables & Stations

800 Kipling Avenue, Toronto Ontario [email protected]

Mobile: 416.206.7528

Office: 416.207.6000 xtn 6347

Responsible for all HV & EHV Cable testing and PartialDischarge diagnosis in North America and Europe

mailto:[email protected]:[email protected]


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Questions?


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Thank you for your attention

Documents

Kinectrics Presentation - HV Cable Testing