A STUDY TO IDENTIFY CONDITION MONITORING TESTS FOR …

A STUDY TO IDENTIFY CONDITION MONITORING TESTS

FOR

LOW AND MEDIUM VOLTAGE NUCLEAR CABLES

Koksal Tonyali and Roy Haller

EQTM-2014 Meeting – November 2014

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The majority of this work was conducted at an independent test laboratory, Kinectrics, Inc.

Disclaimer:

This presentation is an overview of General Cable’s many years of product development efforts. The test data provided in this presentation applies to specific materials and should not be used to predict the performance of other materials unless they are independently tested and verified. Further, the presented data is only partial in nature and is not a qualification report.

Acknowledgment:

©General Cable Corporation 2014, all rights reserved.

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• Why is a Condition Monitoring Test Important?

• Test Methods Employed

• Cable Type Tested

• Cable Test Results

• Is a Single Test Method Sufficient?

• Summary & Conclusion

Outline


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• Monitor the cable aging process while the cable is in use

• New 60-year life cables being installed – More stringent requirements

– Higher radiation exposure

– Cable jacket performance is more critical

– Studies of uninstalled cables vs. installed of cables

• Life extension studies of existing nuclear plants –When do you pull the plug?

• How do you correlate cable qualification testing to actual aged cable performance?

Why Need a Test?


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• Select cable samples for monitoring • Install reference cable samples in areas that represent

typical or critical areas based on temperature and/or radiation

• Perform testing on the samples for trending by use of a combination of methods

• Data obtained would: – Be representative of cables installed in a specific location – Provide a comparison of condition monitoring methods – Provide actual trending data of cable condition based on location

How Can You Perform Condition Monitoring in the Field?


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Fresh cables were aged to different cable life simulations by thermal method, gamma radiation and a combination of thermal + radiation aging.

The condition of the aged samples was assessed using the techniques of:

1. Retained Elongation-at-break

2. EPRI Indenter Modulus (IM)

3. Near Infrared Spectroscopy (NIR)

4. Oxygen Induction Time at 230⁰C or 240⁰C (OIT)

Test Methods


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ULTROL® 60+ LV and MV Cables

LV Cable Constructions:

• 16 AWG 1/C 600V XLPE Insulation

• 22 AWG 1-pair 300V XLPE Insulation and XLPO Jacket

• 12 AWG 7/C 600V XLPE Insulation and XLPO Jacket



MV Cable Construction:

• 1/0 AWG 1/C 15KV LACT Shield with EPR Insulation and XLPO Jacket

Cables Tested


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Elongation and OIT (Raw Data)

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Elongation and Indenter Data

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• OIT data was obtained at 230⁰C for Insulation and 240⁰C for Jacket to obtain reasonable degradation times.

• Although some trend was observed, it does not appear to be useful to make a quantitative assessment.

• It is likely that at very high degradation temperatures, other potential reaction mechanisms can occur leading to misinterpretation.

OIT Data Summary


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• EPRI documents exist.

• IM trending was not reliable when harder compounds like XLPE or XLPO were tested. Changes are small.

• EPR Insulation (softer) was tested but again the changes were small upon aging, not yielding a quantitative method.

EPRI Indenter Modulus (IM)

Data Summary


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• We tested light colored insulations to eliminate color interaction.

• Spectra were obtained to monitor strong NIR absorbers like C-H, O-H, N-H, C-O, COOH and aromatic C-H groups, i.e., relative concentration as a function of aging.

• Data was plotted vs. elongation to correlate.

Near Infrared (NIR) Spectroscopy


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NIR Spectra - Example

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• Relatively good correlation was obtained between the aged specimen elongations and predicted elongation values using NIR spectra measurements.

• Additional testing is recommended to improve the model.

NIR Data Summary


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• Best condition monitoring method is testing the elongation of the cables as they age – requires large samples and not user-friendly.

• NIR test method has some promise for predicting aging – more data is needed to improve the modeling.

• OIT or Indenter might be used qualitatively but requires careful evaluation before making prediction.

• Combination of methods may be helpful.

Summary & Conclusions


A STUDY TO IDENTIFY CONDITION MONITORING TESTS FOR …

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