A comprehensive review: Evaluation of AC Induced Voltage on Buried Pipeline Near Overhead Transmission Lines and Mitigation Techniques Comparison

Steel pipelines used to transport gas and other petroleum products are protected by insulating coatings as well as cathodic protection systems. These pipelines sometimes are passed near the power lines, causing induced AC voltage on them. Increasing the AC voltage amplitude on the buried pipelines will increase the risk of electric shock, electric sparking between the equipment connected to the pipeline and the ground or adjacent metal structures, increasing the rate of insulation damage to the pipelines, disrupting the functioning of the cathodic protection system as well as increasing the AC corrosion of pipelines. Therefore, it is necessary to study and evaluate the factors affecting the inductive AC voltage level and provide effective solutions to reduce its destructive effects. In this paper, the inductive voltage of overhead lines on buried metal pipeline has been investigated under normal conditions of power system. The amount of induced voltage on the pipelines depends on some factors such as the current of the transmission line, the number of transmission line circuits, the arrangement of the phases, and the distance between the transmission line and the underground pipeline

Stability Assessment of Pipeline Cathodic Protection Potentials under the Influence of AC Interference

Abstract: Metallic pipelines are protected from induced corrosion by the application of coating and Cathodic Protection (CP) systems. The latter is achieved by keeping the pipeline at a constant Direct Current (DC) voltage in relation to the surrounding soil. While this is conventionally meant to arrest corrosion, the Alternating Current (AC) interference from high voltage transmission lines has been a major problem to the CP potential systems of buried steel pipelines. Several research studies dealing with this problem have been published, and a lot of research work is still on going. This work focuses on assessing the stability of the CP potentials under the influence of AC interference. Seven different CP potentials varying from −800 mV to −1200 mV were applied on steel pipe specimen exposed to the AC interference with a varying AC voltage from 0–50 V. The results of the laboratory investigation revealed that CP potential of −1150 mV was more stable under the influence of AC interference, with just a minimal shift from the set value. The results from the corrosion morphology tests on the pipelines using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) reveal the need for optimising the CP potential to provide adequate or optimum protection to the pipelines. Thus, more research studies involving simulation and field studies may lead to a major breakthrough in improving protection potentials

Induced voltage on gas pipeline due to alternating current total inteference of faulted overhead transmission line

In locations where a buried gas pipeline (PL) shares the same right-of-way with a high voltage overhead transmission line (TL), a relatively higher voltage than normally allowed may be induced in the pipeline due to the alternating current (AC) total interference between the TL and PL. The increase may damage the pipeline coating, connected pipeline equipment, as well as may pose a safety threat to pipeline service personnel. Key questions to be answered are how to evaluate, and minimise the AC total interference made up of inductive and conductive components and their related effects in the event of a power system fault occurring in the TL. This research investigated the pipeline induced voltage behaviour while simultaneously considering the inductive and conductive interferences. Different observation point profiles were considered to obtain various types of induced voltages such as metal ground potential rise (GPR), touch voltage, coating GPR, coating stress and earth surface GPR. A performance comparison between two computational methods, namely electromagnetic field (solutions to Maxwell's equations) and circuit-based (solutions to circuit equivalents of network configuration) approaches were carried out. The TL-PL AC total interference behaviour under various conditions were studied. These included the influence of complex soil structure, soil resistivity, defective pipeline coating, and several other critical parameters. A 30-kIn long, 115 kV TL and a 10 krn long, 24-in PL were used. Results showed that the circuit-based approach performed as good as the field approach (within 5% error). The close agreement between the two approaches shows that the simulation and modelling works carried out in this work are valid. The TL-PL inductive interference increased with the fault current, but decreased with the TL-PL separation distance, the surrounding soil resistivity, and the tower footing resistance. Nevertheless, the conductive interference had to be considered when computing the pipeline induced voltages especially when the soil resistivity was low « 10 Q-m), the fault current was high (> 10 kA), the tower footing resistance was low « 5 Q), and the separation distance between the TL and PL was small « 20 m). In addition, the effect of pipeline coating condition on the induced voltages was dependent on pipeline coating resistivity as well as the soil resistivity. High touch voltage poses threat to human and equipment safety, while high coating stress may accelerate pipeline coating deterioration and corrosion . The results also showed that the variation of the induced voltages in the pipeline buried in complex soil structure depended mainly on the thickness of the first horizontal layer, or the width of the middle vertical layer, or both. The complex soil structure can be replaced with a three-vertical-layer equivalent structure when the width of the middle layer is above 16 krn and the thickness of the first horizontal layer is above 100 m. Adequate soil resistivity measurements must therefore be performed to provide the complete soil resistivity data for the complex as well as non-uniform soil models

Blackstarting the North American power grid after a nuclear electromagnetic pulse (EMP) event or major solar storm

The electric power grid is our most critical infrastructure. This key resource provides the energy required for all other infrastructures to function. In modern times, electricity has become necessary to sustain life. The power grid in the U.S. is a target for terrorists and is vulnerable to naturally-occurring events. Numerous assessments have been performed on the vulnerability of our national power grid to both manmade and natural events.1 Two significant wide-area threats against our power grid are solar storms and electromagnetic pulse (EMP) attacks. Solar storms are naturally-occurring events that have the potential to create large-scale blackouts that could potentially affect more than 50% of the U.S. population.2 EMP attacks occur when nuclear weapons are detonated at high altitudes; although there is no threat of direct blast or radiation dangers to humans, EMP events can wreck power grids. Although numerous studies have been conducted on the effects of EMP events and solar storms on the U.S. power grid, little has been done to plan for restarting or “blackstarting” the power grid after such an event. If electricity from unaffected areas is not available, the blackstart process becomes much more challenging. The procedures required to blackstart the power grid following a wide area outage are very different from the procedures used to restart the power grid following the major but limited blackouts that have occurred to date such as the 2003 Northeast blackout. This document develops a starting point for blackstarting the U.S. power grid based on likely effects on critical infrastructures caused by solar storms and EMP events. Previous regional blackstarts were assessed to glean empirical information on aspects that could be extrapolated to a national blackstart contingenc

Prevention of electrical accidents with safe personal protective bonding and earthing

Working on powerlines is an inherently dangerous occupation. Powerline construction and maintenance can be performed whilst the power line is energised or de-energized. Although working with the powerline switched off is logically safer, a lineworker may still be exposed to lethal electrical hazards with causes such as lightning, induction or accidental energisation. Sadly, there are numerous examples where line workers have been electrocuted working on de-energised powerlines. The title of this project is 'Prevention of electrical accidents with safe personal protective bonding and earthing'. Personal Protective Bonding and Earthing (PPBE) is a safety technique employed by line workers to protect themselves against the the risk of an electric shock. The technique aims to ensure the worksite is maintained at equipotential conditions at all times. This is attempted by the installation of bonding cables at or near the work area to ensure all conductive surfaces are electrically connected together. The project aim is to identify unsafe conditions that may exist for the application of PPBE. If unsafe conditions are identified it may be possible to determine solutions which will make working on powerlines safer. The electrical principles which underpin the use of PPBE can be applied to all forms of electrical work. However, the focus of this project is on high voltage distribution powerlines

Evaluation of Gas Insulated Lines (GIL) for long distance HVAC power transfer

Offshore wind power is a key element in EU policies to reduce the greenhouse effect and secure energy sources. In order to accomplish the EU’s target of a 20% share of energy from renewable sources by 2020, some of the planned projects have to be placed far away from the shoreline to benefit from the high wind speeds in the open sea area. However, a traditional transmission system for offshore wind farms based on a High Voltage Alternating Current (HVAC) utilizing conventional cables is not appropriate for long distances. In contrast, a High Voltage Direct Current (HVDC) can transmit electrical power over such distances, but the complicated concept of converting the HVAC offshore generated power into DC and then converting the DC power at the onshore grid back to AC requires sophisticated and expensive converter stations at both ends. Therefore, developing a new infrastructure solution based on HVAC transmission technology, which has been in operation for more than a century and which runs almost entire electrical systems, to support and advance the development of offshore wind energy is a highly desirable outcome. This research work was conducted to examine and determine the suitability of using an HVAC gas-insulated transmission line (GIL) as a long-distance transmission system for offshore wind farms in terms of technical and economic costs. A computer model of GIL has been built using the Electromagnetic Transient Program (EMTP) to assess the suitability of GIL and quantify the voltage, current and power transfer characteristics of the GIL under different steady state conditions. Furthermore, a suitable model has been developed for the simulation of the switching transient during energisation of the GIL transmission system and various wind farm components. The development concept of GIL as a submarine Power Transmission Pipeline (PTP) is described, and the practical side of installing the PTP technology and the special design requirements of the offshore wind farms were illustrated. The PTP components, the maximum transmission capacity of the PTP system and the layout options were addressed. In addition, the challenges facing this technology were discussed. An economic comparison of the total cost for both HVAC-GIL and HVDC-VSC transmission systems is made, including annual costs (operation, maintenance, and losses) during the lifetime of the projects. The initial investment costs are added to the annual costs in order to obtain the total cost for the assumed project. Furthermore, the Power Transmission Cost (PTC) is calculated for each MVA-km being delivered to the receiving end of the GIL transmission line

Investigation of wireless power transfer-based eddy current non-destructive testing and evaluation

PhD ThesisEddy current testing (ECT) is a non-contact inspection widely used as non-destructive testing and evaluation (NDT&E) of pipeline and rail lines due to its high sensitivity to surface and subsurface defects, cheap operating cost, tolerance to harsh environments, and capability of a customisable probe for complex geometric surfaces. However, the remote field of transmitter-receiver (Tx-Rx) ECT depends on the Tx-Rx coils gap, orientation, and lift-off distance, despite each coil responding to the effect of sample parameters according to its liftoff distance. They bring challenges to accurate defect detection and characterisation by weakening the ECT probe’s transfer response, affecting sensitivity to the defect, distorting the amplitude of the extracted features, and responding with fewer feature points at non-efficient energy transfer. Therefore, this study proposed a magnetically-coupled resonant wireless power transfer (WPT)-based ECT (WPTECT) concept to build the relationship between Tx-Rx coil at maximum energy transfer response, including shifting and splitting (resonance) frequency behaviour. The proposed WPTECT system was investigated in three different studies viz., (1) investigated the multiple resonance point features for detection and characterisation of slots on two different aluminium samples using a series-series (SS) topology of WPTECT; (2) mapped and scanned pipeline with a natural dent defect using a flexible printed coil (FPC) array probe based on the parallel-parallel (PP) topology of WPTECT; and (3) evaluated five different WPTECT topologies for optimal response and extracted features and characterised entire parameters of inclined angular Rolling Contact Fatigue (RCF) cracks in a rail-line material via an optimised topology. Multiple feature extraction, selection, and fusion were evaluated for the defect profile and compared in the study, unattainable by other ECT methods. The first study's contribution investigated multiple resonances and principal component analysis (PCA) features of the transfer response from scanning (eight) slots on two aluminium samples. The results have shown the potential of the multiple features for slot depth and width characterisation and demonstrated that the eddy-current density is highest at two points proportionate to the slot width. The second study's contribution provided a larger area scanning capability in a single probe amenable to complex geometrical structures like curvature surfaces. Among the extracted individual and fused features for defect reconstruction, the multi-layer feed-forward Deep learning-based multiple feature fusion has better 3D defect reconstruction, whilst the second resonances feature provided better local information than the first one for investigating pipeline dent area. The third study's contribution optimised WPTECT topology for multiple feature points capability and its optimal features extraction at the desired lift-off conditions. The PP and combined PP and SS (PS-PS) WPTECT topologies responded with multiple resonances compared to the other three topologies, with single resonance, under the same experimental situation. However, the extracted features from PS-PS topology provided the lowest sensitivity to lift-off distances and reconstructed depth, width, and inclined angle of RCF cracks with a maximum correlation, R2 -value of 96.4%, 93.1%, and 79.1%, respectively, and root-mean-square-error of 0.05mm, 0.08mm, and 6.60 , respectively. The demonstrated magnetically-coupled resonant WPTECT Tx-Rx probe characterised defects in oil and gas pipelines and rail lines through multiple features for multiple parameters information. Further work can investigate the phase of the transfer response as expected to offer robust features for material characterisation. The WPTECT system can be miniaturised using WPT IC chips as portable systems to characterise multiple layers parameters. It can further evaluate the thickness and gap between two concentric conductive tubes; pressure tube encircled by calandria tube in nuclear reactor fuel channels.PTDF Nigeri

Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Ground fault current: Calculation of magnitude and its distribution in the neutral and ground paths

This thesis focuses on the ground fault current distribution and presents a method that enables a high accuracy in its calculation: starting from the model based on multi-conductor representation developed in Matlab, simulations are carried out to analyse which parameters influence the current distribution. These simulations, applied even on the portion of a real network, are also carried out on the commercial software Neplan and OpenDSS to validate the model