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Condition Assessmentof Medium & High Voltage

Electric Assets

Who is Techimp ?

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A world-leading company in advanced testing and monitoringsolutions for electrical assets including:

• High Voltage and Medium Voltage Underground Cable Systems

• Power & Distribution Transformers

• GIS (Gas Insulated Switchgear)

• MV Switchgears

• Motors and Generators

We are experts in partial discharges (PD) and we design andbuild testing equipment, sensors and analysis software.

Infantmortality

Randomfailure

Standardaging

time

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Reduced risk with

CBM and quality

control

without diagnostic&standard aging

On-line/Off-line assessment

Short term monitoring

Risk Management

The information provided here is for informational and educational purposes and current as of the date of publication. The information is not a substitute for legal advice and does not necessarily reflect the opinion or policy position of the Municipal Association of South Carolina. Consult your attorney for advice concerning specific situations.

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Electric System

o Reliability of the electric system is of utmost importance.

o The majority of assets fail as a consequence of a problem in the insulation

system.

o Challenge: the electric infrastructure is ageing and many critical assets are

approaching end of life. Failure can have costly consequences.

o Partial Discharge testing helps our clients understand the health of the

insulation and therefore the health of their electrical assets.

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Techimp Services

Factory Acceptance Tests

Commissioning Tests

Offline Testing (VLF or RTS)

Online Non-Destructive Testing

Monitoring Solutions of all Assets

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Partial Discharge

Partial discharge (PD)

Localized electrical discharge that only partiallybridges the insulation between conductors andwhich can or can not occur adjacent to aconductor.

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PD normally develop in air gapsor on insulation surfaces, due todefects in the insulation system.

PD is correlated to insulationageing, insulation degradation.

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Why Test for PD?

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PD is related to local defects within the insulation system

PD is the fastest insulation degradation mode

PD can be triggered by overvoltages

Internal PD

Surface PD

Corona PD

HA

RM

FU

LN

ES

S

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Identification of the different typeof PD can be done by PD Pattern analysis

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MAIN INSULATION

JOINTAND TERMINATION

SURFACE PD

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Techimp Technology Advantages

HardwareAcquires PD in UWB modeFull spectral content of each PD pulse available, allowing

for more powerful analysis

Analysis SoftwareProprietary T-F Map SoftwareReadily separates external noise and disturbancesCan separate different types and sources of PDMinimizes false positives or false negatives

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Techimp advantages

Separation

IdentificationDiagnosis

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Advanced noise rejection and Pulse UWB analysis

T-F map technology for separation of PD phenomena

Same PD detector for all electrical apparatus

Techimp Technology – Online Test

Online Partial Discharge testAssessment is performed online at operating system

voltageNo outages or switching operations are required

Non-destructiveNo signals are impressed on subject cablesNo over-voltage is appliedWill not activate harmless PD sitesSwitching transients are avoidedDoes not shorten the remaining life of the cable

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Techimp Online PD Advantages

RapidOnline data acquisition is performed in minutesAbility to assess ~50% more segments compared to

Offline Testing. SafeSubject cables are not disconnected from the systemExposure of personnel to energized environments is

minimized. CompleteAssessment results indicate the condition of the insulation

of the asset and its accessories, and can identify problemswith connected equipment.

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Cable Applications

Any voltage class from 2.4 kV

All types of insulation; PILC, EPR, HMWPE, XLPE, TRXLPE and Butyl Rubber

All conductor sizes

Laminar, extruded, armored and/or mixed cable circuits

Any circuit configuration: straight or branched

All installations - direct buried, conduit, or trays

Conduit

Direct buried

Concreteencased conduit

Laminar, extruded &mixed cable circuits

Branched circuit

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Data Acquisition

Portable Equipment

50’ Test Leads

May acquire data from one or multiple phases

5-8 minutes to record data for each placement

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Sensors

Techimp Proprietary Sensors

Signal activity is detected with proprietarycapacitive or inductive sensors

Both types of sensors have high sensitivityon PD detection

U-Cap sensors are available with differentsize openings (1.5 to 6 inch)

U-Cap sensor is operated with hot stick-safety

Easy and fast for sensor placement

Techimp U-Cap sensor

Techimp HFCT Clamp sensor

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Coupling Capacitor:Installed in parallel to the transformer bushings.

MV Transformers

HFCT 140mm:Installed around the MV cable connected to the

transformer.

HFCT 39mm:Installed around the ground lead of the MV

cable termination.

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MV Transformers

U-Cap sensor:Installed on the cable close to theaccessory (terminations and joints).

FMC:Installed on the cable close to theaccessory (terminations and joints).

Cables

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Cables

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HFCT 39mm:Installed around the ground lead of thecables (terminations and joints).

HFCT 140mm:Installed around cables, where ground leads are notavailable. (terminations and joints)

Cables

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Sensor Placements

Sensor placements Each end below

termination Each splice location

(when accessible) Mid-span for excessively

long segments

RF source incable insulation

RF signal path RF signal path

Sensor placement at device #1.

Sensor placement at device #2.

Detectioninformationacquired atboth devices,one after theother.

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Cables

Conduction

HFCT

PD EVENT

HFCT

Ucap

Cables

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Data Analysis

Data analysis is performed in both frequency and time domains.

T-F Map is employed for noise rejection and PD signal separation.

The defects are identified using the phase resolved discharge pattern.

The success rate of the online assessment is proved by the NEETRAC CDFIreport.

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PD Signal Attenuation

Defect

Location

Pulse direction

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pC

MHz

PD Signal Attenuation

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pC

pC

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The phase of PD pulse with respect to thevoltage applied

Typical PD pattern Repetitionrate and amplitude of PD

signal

PRDP pattern TF map

Different cluster of PD; possible toseparate all differentPD and noise

corresponding its PRDP pattern

Complete analysis of multiple PD sources

PD DATA ANALYSIS: T-F MAP

Signal Separation with T-F Map

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Corresponding Sub-PRDP patterns:

By separating different cluster showing in TF map,specific PD pattern corresponding PRDP can bepresented, which can be used for further analysis.

Black phenomenonBackground Noise

Example of points clustering separation inthe T-F map

PD DATA ANALYSIS : T-F MAP EXPLOITATION

Red phenomenonInternal PD

Blue phenomenonSurface PD

Signal Separation with T-F Map

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Phase Resolved Pattern

Phase Resolved Discharge Pattern Analysis

Signal Intensity

Pulse Repetition

Phase Angle

Signature

Synchronicity

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• Amplitude

Corona Discharge

HV

• Repetition Rate • Phase Resolved Pattern

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Surface Tracking Discharge

• Amplitude • Repetition Rate

• Phase Resolved Pattern

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1

0.5

0

-0.5

-1

• Amplitude • Repetition Rate

Insulation Cavity Discharge

• Amplitude • Repetition Rate • Phase Resolved Pattern

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Cable & Splice Degradation

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Partialdischarge

FAILURE

Partialdischarge

Partialdischarge

Partialdischarge

Electrical trees: Produce measurable PD

Partialdischarge

Partialdischarge

ContaminationElectricalTreeing

Protrusionor Cavity

InterfacialDischarge

or Tracking

SurfaceTracking

ExternalDamage

PD Levels

Level 1-The system is not degraded.

No immediate action needs to be taken.

Level 2-There is a small amount of aging related signals.Re-Test is recommended within two years.

Level 3-Component has a low to moderate level of deterioration.System has low probability of failure within the next two years.Re-Test is recommended within one year.

Level 4-System has medium probability of failure within the next two years.Further discussion is required with the customer to determine the viabilityof repair or replacement.

Level 5-Component is at the end of economic life and hasa high probability of failure within one year.Recommend immediate attention.

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Probability of Failure

NEETRACNatl Electric Energy Testing, Research

& Applications Center

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Report-Table

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Report-Diagram

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Summary

Advantages of Online PD Testing

Ensure electrical system reliability

Avoid unplanned outages & power quality problems

No outages or switching operations are required

Prioritize or defer electrical system maintenance andreplacement

Assess entire cable system & assets, regardless ofinsulation or circuit configuration

Ability to assess 50% more segments per day

Verification of craftwork in newly installed assets

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Questions?

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Case Study #1 - Utility

Performed Condition Assessment inOctober

Manhole to manhole segment of 3-phase500kcmil AL 175mil XLPE

Terminated to bus work in manhole with600amp T-bodies

Analysis of RF signal data identified strongdischarges in T-body on Phase C

Phase C terminator was assigned Level 4with a Moderate to High probability offailure and replacement of the terminationwas recommended in the report

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The terminator remained in service

The terminator failed in March

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Case Study #1 - Utility

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