Abstract
The introduction of high performance, fusion bond coatings provide pipeline structures with excellent isolative characteristics. These high performance coatings are of great benefit to the industry as they increase the efficiency and performance of the cathodic protection systems. However, when pipelines are collocated along high voltage AC power transmission lines, the high dielectric effect of fusion bond coatings may have a detrimental effect resulting in induced AC voltage. These induced voltages may create safety hazards to operating personnel and the general public and are known to cause corrosion at varying voltage levels and operating environments.
It is essential to design and install an adequate grounding system capable of lowering and maintaining induced AC voltage at safe operating levels, and ensuring that AC currents discharging to the soil at coating faults are not exceeding current densities known to cause corrosion. Due to the variables affecting induced AC voltage and AC current levels, and the potential safety concerns of exceeding permissible levels, continual verification of the effectiveness of the AC mitigation system is a necessary part of a complete AC mitigation solution.
Methods of tracking these levels through periodic measurements or data logging at test-point sites provide an incomplete picture with data retrieved after the fact rather than real time. Tests were done with remote monitoring equipment designed to capture induced AC voltage fluctuations in real-time and send immediate notification of out-of-range readings, as well as continually logging the readings in the internal memory for upload retrieval over the web at user defined intervals. The conclusion is this method of benchmarking and verification of AC mitigation performance provides superior information through the transmission of actionable alarm data and increased frequency of logged data retrieval. This method is designed to be a permanent, ongoing verification of mitigation system effectiveness as the influences contributing to AC induction on pipelines continually change.
