Presented at the Insulated Conductors Committee, San Antonio, Texas, October 26-29, 2008

Drapeau, Jean-Francois

Hernandez, J. C.

English

Scholarly Materials And Research @ Georgia Tech

Measurement of Cable System Losses using Time Domain and VLF TechniquesJ.-F. Drapeau, IREQJ.-C. Hernandez, NEETRAC2008-10-272OUTLINE1. VLF and TDS Principles 2. Correlation between Tan δ measurements at VLF and TDS3. Neutral issues for VLF4. Effect of polluted terminations5. “Arithmetic” of Tan δ at VLF and TDS (overview)6. Conclusions2.1  New cables2.2  Joints2.3  Field aged cables31 – VLF and TDS PrinciplesDielectric losses  - Tan δVIRI CI1tan( ) RCIDFI RCδ ω= = = VRIICIδθ• The cable insulation system is represented by an equivalent circuit• It consists of two parameters; a resistor and a capacitor [IEEE Std. 400]• When voltage is applied to the cable, the total current will be the contributions of the capacitor current and the resistor current41 – VLF and TDS PrinciplesDielectric losses  - VLF principle• Frequency domainVRIICIδθ• In this case, performed in AC (sine wave) "VLF"  (0.1 Hz to 0.02 Hz) • Derived from the phase angle difference between I and V51 – VLF and TDS PrinciplesDielectric losses  - TDS principle• Time domainPrincipleSchematic of TDS device(Grounded config.)( ) ( ) ( ) ( )titititi qcabscappol ++=( ) ( ) ( )tititi abscapdepol −−=M :  Multimeter             10 X 10-9 AE :  Electrometer 1 X 10-12 ASensitivity• Based on current measurements under DC voltage • Dielectric losses derived from the current contributions using Hamon approximation 61 – VLF and TDS PrinciplesIREQ's TDS system71 – VLF and TDS PrinciplesDielectric losses  - TDS principle• Example of current measurement( ) ( ) ( ) ( )titititi qcabscappol ++=( ) ( ) ( )tititi abscapdepol −−=200 s pol500 s depol81 – VLF and TDS PrinciplesDielectric losses  - TDS principle• Application of the Hamon approximation91 – VLF and TDS PrinciplesTan δ  : VLF vs TDSVLF• Frequency domain• Sinusoidal waveform• Computed from a phase difference• Tan δ at different frequencies requires different tests• Monitored withstandTDS• Time domain• DC waveform• Estimated using the Hamon approximation• One test at a particular test voltage provides Tan δ at different frequencies• Monitored withstand101 – VLF and TDS PrinciplesVLF & TDS Laboratory Setups112 – Correlation between Tan δ measurements at VLF and TDS2.1  New cables  - TR-XLPE122 – Correlation between Tan δ measurements at VLF and TDS2.1  New cables  - EPR132 – Correlation between Tan δ measurements at VLF and TDS2.2  Joints  - PIT3-C1142 – Correlation between Tan δ measurements at VLF and TDS2.2  Joints  - PIT3-C2152 – Correlation between Tan δ measurements at VLF and TDS2.3  Field aged cables  - S-1-3162 – Correlation between Tan δ measurements at VLF and TDSCorrelation  Tan δ - VLF  vs TDSTan-delta VLF [1e-3]Tan-delta TDS [1e-3]100.010.01.00.1100.010.01.00.1Field Aged CableOtherConditionValues at 0.02 Hz and UoNon-aged cables, field-aged joints and cable-joint combinations.Other includes: Tan-delta TDS [1e-3]IssuesNeutralEPR withTan-delta TDS [1e-3]172 – Correlation between Tan δ measurements at VLF and TDS – Interim Conclusions• Good correlation between Tan δ from  VLF and Tan δ from TDS for samples not evolving during test.• Spectrums seem to complement each other.183 – Neutral Issues for VLF193 – Neutral Issues for VLF203 – Neutral Issues for VLFEPR with Good neutral connection213 – Neutral Issues for VLFEPR with Bad neutral connection224 – Effect of highly polluted terminationsIt is normal practice in the field to thoroughly clean terminations. Insufficient cleaning can occur but is readily spotted by divergent behavior of the capacitance, loss and voltage dependence.Nevertheless there was an academic interest to investigate the magnitude of this effect on the cable system loss.234 – Effect of highly polluted terminationsNormal clean test terminations prior to pollutionPolluted test terminations244 – Effect of polluted terminationsTime [min]Tan-delta [1e-3]4321010001001013.8CleanPolluted - DryPolluted - HumidPolluted - WetCondition0.33 Uo 0.67 Uo 1.0 UoVLF of 0.1 HzflashoverTermination254 – Effect of polluted terminationsFailure channelHighly polluted surface265 – "Arithmetic" of Tan δ at  VLF  and  TDSTR-XLPE cable system without splive(Overvue)275 – "Arithmetic" of Tan δ at  VLF  and  TDSJoint PIT3-C1 alone(Overvue)285 – "Arithmetic" of Tan δ at  VLF  and  TDSTR-XLPE system cable  PLUS  Joint PIT3-C1As measured directly:(Overvue)295 – "Arithmetic" of Tan δ at  VLF  and  TDSTR-XLPE system cable  PLUS  Joint PIT3-C1As calculated by sum of individual contributions:(Overvue)306 – Conclusions• Good correlation between Tan δ from  VLF and Tan δ from TDS for samples not evolving during test.• Spectrums seem to complement each other.• Polluted terminations influence cable system loss measurements.• TDS seems less perturbed by neutral issues then VLF.• “Arithmetic” of cable system loss works for TDS as well as for VLF.

Measurement of Cable System Losses Using Time Domain and VLF Techinques

https://smartech.gatech.edu/bitstream/1853/27639/1/ICC_Fall_2008_Sub_F_TDS_%26_VLF.pdf

Measurement of Cable System Losses Using Time Domain and VLF Techinques

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