Cable Aging Assessment and ConditionMonitoring with LIRA

Paolo F. FantoniOECD Halden Reactor Project

Institutt for energiteknikkHalden, Norway

IEEE SC2 Meeting, Newport Beach, CA, 7-8 November 2006

2 December 2006

HRP Project on Cable AgingThe LIne Resonance Analysis (LIRA)

method• Based on frequency domain analysis of high

frequency resonance effects of unmatched transmission lines.

• Sensitive to small changes of wire electric parameters, mainly the insulation permittivity, that are a significant condition indicator of the cable state (thermal and radiation aging, humidity, insulation defects, mechanical damage).

• Possibility to detect and localize small insulation cracks, in spite of different structures (insulation type, geometry) and not-aging related effects.

2 December 2006

Electric parameters in a cable

2 December 2006

LIRA as a Condition Indicator

Analysis of the line input impedance amplitude/phase provides:

• Accurate estimation of the phase velocity, correlated to the global cable condition

• Detection and localisation of one/many hot spots along the cable

2 December 2006

Hot spot detection in LIRA

2 December 2006

Global Condition Indication

• Phase Velocity (PV) in LIRA is estimated with 4 precision digits (0.XXXX). PV is a decreasing function of global insulation degradation.

• PV can be correlated to any other accepted Condition Indicator (ie EAB), for condition assessment and residual life estimation (EPRI tests, November 2006)

Velocity ratio vs. capacitance

7400

7500

7600

7700

7800

7900

8000

56 57 58 59 60 61

Capacitance (pF/m)

Vel

. rat

io *

E+4

2 December 2006

Wirescan, implementing the LIRA engine

• 3 SW modules:• Generator controller• Analyzer• Simulator

• 3 HW modules:• AWG Generator (NI-PXI)• DSO Digitizer (NI-PXI)• Modulator (Wirescan)

2 December 2006

Wirescan beta version (Aug. 2006)

2 December 2006

Wirescan in a field experiment

2 December 2006

Projects/Experiments

• EPRI (2005 – 2006)• Norsk Hydro (2005)• NKS, Ringhals, Barseback (2005 2006)• PETROMAKS (NFR, Hydro, Shell, 2006-2008)• NEXANS, 2006

2 December 2006

EPRI Tests

• September 2005: preliminary, feasibility tests on Okonite and Rockbestos specimen

• May 2006: detection of cuts and gouges(EPR and XLPE)

• November 2006: local and bulk degradation. Effect of wet vs. dry

2 December 2006

EPRI Tests (September 2005)

• 10 EPR and XLPE specimens have been tested at EPRI, Charlotte, on September 15th and 16th

• The cable samples had passed bulk accelerated aging and local spots in different positions

• LIRA was used to identify both severity and position of the local thermal spots and the bulk aging.

2 December 2006

EPRI Experiment (May 2006)

• EPR and XLPE I&C cables from several vendors (Brand Rex, Rockbestos,Dekoron, Okonite) were tested for detection of cuts and gauges, both in dry and wet conditions.

• Initial measurements on good cables were taken. These cables will go through accelerated thermal aging in the period June-September 2006. New tests on these cable will be carried on in November, to evaluate the LIRA performance in assessing local and bulk thermal degradation.

2 December 2006

EPRI Experiment, May 2006

2 December 2006

XLPE Brand Rex. Cut (at 24m) down to the insulation, 2 wires, dry

2 December 2006

Specimen XBC1, LIRA spot detection

2 December 2006

XLPE Rockbestos. Gouge (at 24m) down to the insulation,2 wires, dry

2 December 2006

Specimen XRG1

2 December 2006

EPRI tests, May 2006, conclusions

• LIRA performed well in detecting hot spots in both Okonite and Rockbestos cables (September tests).

• The localization accuracy is lower than 0.5%.• Tests with cuts and gauges showed that LIRA can

detect mechanical defects in wet and dry conditions.• Reference measurements were taken with cables

that will be locally and globally aged (used in November 2006 tests)

2 December 2006

EPRI tests, November 2006

2 December 2006

Thermal hot spots at 8m (22.5m)

2 December 2006

Hot spots (22.5m), 4 aging times, EPR

EIL1: 216hrs at 150CEIL2: 479hrs at 150CEIL3: 527 hrs at 150CEIL4: 575 hrs a 150C

1m thermal agingAt 8m (22.5)

2 December 2006

Hot spots (22.5m), 4 aging times, XLPE

1m thermal agingAt 8m (22.5)

XRL1: 1002hrs at 150CXRL2: 1150hrs at 150CXRL3: 1300hrs at 150CXRL4: 1450hrs at 150C

2 December 2006

Hot spots, correlation with aging, EPR (BIW)

LIRA indication vs. aging, EPR

30.0

32.0

34.0

36.038.0

40.0

42.0

44.0

0 24.1 53.5 58.8 64.2Years at 80C

Nor

m d

B

2 December 2006

Hot spots, correlation with aging, XLPE (Rockbestos)

LIRA indicator vs. aging, XLPE

60.0

61.0

62.0

63.0

64.0

65.0

66.0

67.0

68.0

0 12.0 13.8 15.6 17.4Years at 100C

dB n

orm

To be evaluated

2 December 2006

Tests on 5kV, EPR, aged and wet

2 December 2006

5kV EPR cable (12B), aged, wet

2 December 2006

5kV EPR cable (15A), aged, wet

2 December 2006

Bulk aging tests

2 December 2006

Bulk aging, XLPEPhase Velocity Ratio vs. aging, XLPE (Rockbestos)

0

584

800

0.61

0.615

0.62

0.625

0.63

0.635

0.64

0.645

0.65

0 100 200 300 400 500 600 700 800 900

Time at 150C (hr)

Phas

e Ve

loci

ty R

a

2 December 2006

Wet vs. dry, EPR

No change in VR

Hot spot at 22.5m

2 December 2006

Wet vs. dry, XLPE

Much lower VR in wet conditions

Hot spot at 22.5m

2 December 2006

Ringhals experiment, June 2006

2 December 2006

Ringhals Experiment

Low voltage, 140m triaxial cable with PVC insulation, 20-25 years aging condition.

Verify that cable extraction and reinsertion does not cause jacket/insulation damage

Line impedance signature

2 December 2006

First on-site test

• Top signature: analysis of the 140m cable with penetration at 105m

• Bottom signatures: analysis of the 105m disconnected cable (at the penetration), before and after relocation

No detectable damage as a consequence of cable movement

2 December 2006

Recent Reports on Cable Aging

• IAEA TECDOC 1188, December 2000, Assessment and management of ageing of major nuclear power plant components important to safety

• Report of the IAGE Task Group on Wire System Aging (NEA). Final report released August 2004 ( NEA/CSNI/R(2004)12 ).

• State-of-the-art report ( HWR-746 ) released April 2004 (Halden Reactor Project Report).

• Workshop on Wire System Assessment and Condition Monitoring, Zurzach (CH), October 29-30, 2004 (HWR-787)

• LIRA Technology (HWR-788), October 2005