Presented by: Craig Goodwin

Medium Voltage

Cable Testing Technologies

Energization Sources:

• DC and DC Leakage Methods (Insulation

Resistance)

• Damped AC (20-300 Hz)

• AC – Power Frequency

• AC – Low Frequency (VLF – 0.1 Hz)

Most Commonly Used Cable Testing

Methods

Cable Diagnostic Technique:

• Withstand

• Tan Delta / Dissipation Factor

• Partial Discharge (Online and Offline)

• TDR (Time Domain Reflectometry)

• Thermal Imaging

• Others

• Combination of the Above - Smart

Most Commonly Used MV Cable Testing

Methods

Online versus Offline • Online testing is generally easier to

carry out, and is so called “non-destructive” its effectiveness is also limited..

• Offline testing, while requiring more preparation and setup, provides more insight into the cables true condition.

IEEE MV Cable Field Testing Chart

IEEE 400 (OmniBus) - 2012 Guide for Field Testing & Evaluation of the Insulation of Shielded Power Cable Systems Rated 5kV and above

IEEE 400.1 Field Testing of Laminated Cables Rated 5kV and above using DC.

IEEE 400.2 – 2013 Field Testing of Shielded Power Cables using Very Low Frequency VLF

IEEE 400.3 PD Testing of Shielded Power Cables in the Field Environment

Note 1 – there is no IEEE 60Hz field withstand testing

standard for MV Cables

Note 2 – there is no IEEE DC field testing standard for any

extruded cables.

• Potential Negative Impact on the Service

Reliability of Extruded Cables

• Ineffectiveness to Detect Serious Defects in

Cable Insulation

The Demise of the DC Hipot for Testing

MV Cables

Ref: IEEE400-2012

Concentric Neutral Design Vs. Tape Shielded

Cable Design Can Impact the Effectiveness and Usability

of Certain Diagnostic Techniques That are Rich in

Frequencies.

Which Energization Source and

Diagnostic Method/s to use and

when……….

IEEE 400 has an Informative Table in the

Appendix on the Applicability of Various Testing

Methods.

Comments

• Some Methods Were Not Analyzed Due to

Lack of Information / Data.

• Some Methods were shown to be useful and

some were Not.

• Table Does Not Address Tape Shielded

Cables and Mainly Focuses on Utility Style

CN Type.

Applicability Of Testing Methods

Test and Diagnostic Selection Matrix:

Expanded from IEEE 400 - 2012

Method New Extruded

Acceptance

Old Extruded

Maintenance

PILC

Laminat

ed

Old

Hybrid

Combo

Unjacket

ed

Accessories

(Splice &

Term)

Shield Type Tape CN Tape CN Mixed Mixed CN Mixed

DC Withstand

Testing

X X X X X X Limited

VLF AC Withstand

Test

Tan Delta /

Dissipation Factor

Test

Partial Discharge

Test – Offline

Limited

Limited Limited

Partial Discharge

Test – Online Limite

d Limited Limited Limited

Limited Limited

Smart VLF W/S Test

- combination with

TD

Smart VLF W/S Test

- combination with

PD

Limited

Limited Limited

TDR (Time Domain

Reflectometry) Useful Useful Not

Useful Useful Useful Limited Useful

• Testing Organizations Need to Be Aware of the

Changes in Standards and Guides

• A Need to Inform and Educate Customers / End

Users

• Careful Consideration When DC is Requested

• Choice of Test Method Often Determined By Age

and Type of Cable and the Intended Defect

Diagnosis

• Often, a Testing Strategy Involving a Combination

of Tests is Most Appropriate.

Conclusions