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PRCI PR-262-9913
- AC Grounding Effects on Cathodic Protection Performance of Pipeline Stations
- Report / Survey by Pipeline Research Council International, 12/01/2001
- Publisher: PRCI
$148.00$295.00
L51908e
CORRENG Consulting Service, Inc.
Need: Most AC powered equipment at pipeline stations and at motorized valve sites is required, by code, to be electrically grounded to one or more ground electrodes. These grounding systems are normally electrically bonded to the AC power distribution grid, which can be quite extensive. Piping, either intentionally or inadvertently, is often connected to the AC electrical grounding grid in pipeline stations. Grounding grid conductors are usually bare and composed of copper or tinned copper, and ground rod materials can consist of a wide variety of metals such as copper-clad steel, carbon steel, stainless steel, galvanized steel, and galvanic anode alloys of zinc and magnesium. The interconnection of these grounding materials to the piping can increase the current requirements of the cathodic protection system, distort the current distribution pattern and complicate the accurate measurement of the pipe potentials.
Benefit: The primary objective of this research project was to assess the impact of various types of grounding materials on the performance and testing of cathodic protection systems. The two major issues in this regard were the effects on current requirements and the accuracy of pipe-to-soil potential measurements. In addition, some related issues investigated as follows:
the electrical resistance of each groundrod-to-earth was to be measured to determine whether or not there were any changes in the resistance-to-earth as a result cathodic polarization;
the potential of galvanized steel was to be measured with increasing zinc consumption to determine if there is a well defined relationship between potential and zinc consumption;
the National Electrical Code (NEC) was to be reviewed with respect to the insertion of AC coupling/DC isolating devices in series between the piping and the electrical grounding network.
Result: The results of this investigation were intended to
provide information to design more effective cathodic protection facilities for piping in pipeline stations having electrical grounding systems, and
determine whether or not the resistance of the electrical grounding system increases as a result of receiving cathodic protection, and
recommend pipe-to-soil potential survey techniques to maximize measurement accuracy in the presence of an AC grounding grid, and
evaluate the use of DC isolators/AC couplers to interconnect the piping to either the secondary or primary AC grounding system.
CORRENG Consulting Service, Inc.
Need: Most AC powered equipment at pipeline stations and at motorized valve sites is required, by code, to be electrically grounded to one or more ground electrodes. These grounding systems are normally electrically bonded to the AC power distribution grid, which can be quite extensive. Piping, either intentionally or inadvertently, is often connected to the AC electrical grounding grid in pipeline stations. Grounding grid conductors are usually bare and composed of copper or tinned copper, and ground rod materials can consist of a wide variety of metals such as copper-clad steel, carbon steel, stainless steel, galvanized steel, and galvanic anode alloys of zinc and magnesium. The interconnection of these grounding materials to the piping can increase the current requirements of the cathodic protection system, distort the current distribution pattern and complicate the accurate measurement of the pipe potentials.
Benefit: The primary objective of this research project was to assess the impact of various types of grounding materials on the performance and testing of cathodic protection systems. The two major issues in this regard were the effects on current requirements and the accuracy of pipe-to-soil potential measurements. In addition, some related issues investigated as follows:
the electrical resistance of each groundrod-to-earth was to be measured to determine whether or not there were any changes in the resistance-to-earth as a result cathodic polarization;
the potential of galvanized steel was to be measured with increasing zinc consumption to determine if there is a well defined relationship between potential and zinc consumption;
the National Electrical Code (NEC) was to be reviewed with respect to the insertion of AC coupling/DC isolating devices in series between the piping and the electrical grounding network.
Result: The results of this investigation were intended to
provide information to design more effective cathodic protection facilities for piping in pipeline stations having electrical grounding systems, and
determine whether or not the resistance of the electrical grounding system increases as a result of receiving cathodic protection, and
recommend pipe-to-soil potential survey techniques to maximize measurement accuracy in the presence of an AC grounding grid, and
evaluate the use of DC isolators/AC couplers to interconnect the piping to either the secondary or primary AC grounding system.
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