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51312-01192-ASSESSMENT OF TELLURIC ACTIVITY IN THE AREA OF PROPOSED ALASKA HIGHWAY PIPELINE

The geomagnetic field fluctuations are accompanied by the geo-electric (telluric) field and telluric currents at the surface of the Earth and in the pipelines. These telluric activity indices were calculated for two areas in low latitude (Ottawa) and Alaska. Levels of telluric activity and rate of occurrences were calculated.

Product Number: 51312-01192-SG
ISBN: 01192 2012 CP
Author: Larisa Trichtchenko
Publication Date: 2012
$0.00
$20.00
$20.00

The geomagnetic field fluctuations are accompanied by the geo-electric (telluric) field and telluric currents at the surface of the Earth and in the pipelines. These telluric currents disturb pipeline cathodic protection levels creating pipe-to-soil potential (PSP) fluctuations with different amplitudes. Amplitudes of PSP fluctuations directly depend on the telluric activity in the area of the pipeline location. To estimate the amplitudes of PSP variations due to telluric activity pipeline circuit model based on Distributed Source Transmission Line Theory can be applied. The unknown and most important input into this model are values of driving ground electric fields i.e. telluric activity in the pipeline area. Two parameters define telluric electric fields in the particular area one is the geomagnetic field variations and other is the deep ground conductivity structure. The magnetotelluric theory was applied in order to calculate geo-electric telluric field variations in the pipeline area. For the Alaska area magnetic data from four Geomagnetic Observatories were used with one-dimensional Earth conductivity model for four different zones obtained on the basis of the geological surveys in order to find the telluric electric field. To properly evaluate effects of telluric activity on the scale of years a statistical study has been done. For the statistical analysis of telluric activity in the pipeline area we established two types of indices of telluric electric field: hourly maximum of the absolute value of the electric field and hourly standard deviation of the electric field. These hourly telluric activity indices were calculated for two different areas low latitude (Ottawa) and Alaska. Statistical distribution of these indices was used to derive the different levels of telluric activity of telluric activity and their rate of occurrences (number of days in the year). The results of the study are universal and can be applied for different pipeline configurations to estimate effectiveness of the cathodic protection.


Keywords: downloadable, Teluric currents,geomagnetic induction, cathodic protection

The geomagnetic field fluctuations are accompanied by the geo-electric (telluric) field and telluric currents at the surface of the Earth and in the pipelines. These telluric currents disturb pipeline cathodic protection levels creating pipe-to-soil potential (PSP) fluctuations with different amplitudes. Amplitudes of PSP fluctuations directly depend on the telluric activity in the area of the pipeline location. To estimate the amplitudes of PSP variations due to telluric activity pipeline circuit model based on Distributed Source Transmission Line Theory can be applied. The unknown and most important input into this model are values of driving ground electric fields i.e. telluric activity in the pipeline area. Two parameters define telluric electric fields in the particular area one is the geomagnetic field variations and other is the deep ground conductivity structure. The magnetotelluric theory was applied in order to calculate geo-electric telluric field variations in the pipeline area. For the Alaska area magnetic data from four Geomagnetic Observatories were used with one-dimensional Earth conductivity model for four different zones obtained on the basis of the geological surveys in order to find the telluric electric field. To properly evaluate effects of telluric activity on the scale of years a statistical study has been done. For the statistical analysis of telluric activity in the pipeline area we established two types of indices of telluric electric field: hourly maximum of the absolute value of the electric field and hourly standard deviation of the electric field. These hourly telluric activity indices were calculated for two different areas low latitude (Ottawa) and Alaska. Statistical distribution of these indices was used to derive the different levels of telluric activity of telluric activity and their rate of occurrences (number of days in the year). The results of the study are universal and can be applied for different pipeline configurations to estimate effectiveness of the cathodic protection.


Keywords: downloadable, Teluric currents,geomagnetic induction, cathodic protection

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