 | 345 kV and 500 kV AC Design Studies: Completed conductor optimization studies based on electrical losses, electric and magnetic fields, and corona performance. Calculated optical ground wire thermal and Coulomb ratings based on short circuit levels and lightning characteristics. Performed electromagnetic transient studies to optimize insulation levels based on transmission line switching and lightning performance. Assessed insulator contamination performance. Calculated OSHA minimum approach distance and NESC electrical clearances.
(Keywords: AC, Overhead, Electromagnetics, HV, EHV, Transmission, High Voltage, Studies, Design). | |
 | AC DC Joint Use Corridor and AC Transmission Line Conversion to DC: Calculated electric fields (including space potential effects), magnetic fields, radio noise, and audible noise to assess the electromagnetic compatibility of a transmission corridor containing both 500 kVAC and ±600 kVDC circuits. Analyzed geometry and clearances of an existing 500 kVAC transmission line to determine what DC voltage the line could accommodate if the AC insulators were replaced with DC insulators.
(Keywords: HV, EHV, Transmission, Overhead, Joint, Corridor, AC, HVDC, Conversion). | |
 | 500 kV and 765 kV Electrical Specifications: Completed preliminary studies to establish detailed electrical design and performance specifications regarding electric and magnetic fields, reactive compensation, electrical losses, steady-state unbalance, switching and lightning performance, insulator contamination, OSHA and NESC clearances, and conductor and hardware corona (including audible noise an radio interference).
(Keywords: EHV, Transmission, Overhead, High Voltage, Specifications, Studies, Design). | |
 | Environmental Permitting Support: Calculated electric and magnetic fields to support environmental permitting for various overhead and underground AC and DC transmission projects. Prepared reports comparing field levels to applicable state or industry guidelines within and outside the right-of-way.
(Keywords: Electromagnetics, Transmission, Permitting, Environmental, Electric, Magnetic, Fields). | |
 | Hardware Corona Performance: Completed 3D electromagnetic finite element analysis of high voltage hardware for 138 kV, 230 kV, 345 kV, and 500 kV insulator assemblies. Models included detailed conductor attachment hardware, insulator strings, and yoke plate assemblies. The models also accounted for the electric field influence from the earth, support structures, shield wire, and all three phases. Results were used to determine if corona rings were necessary and to reduce the extent of high voltage testing.
(Keywords: EHV, Transmission, Overhead, Hardware, Corona, Testing). | |
 | Investigation of Nuisance Shocks: Investigated reports of nuisance shock by children playing in a residential playground near a 230 kV transmission line right-of-way. Prepared a finite element model and calculated electric field results to compare with on-site measurements and industry maximum permissible exposure limits. Once field levels were confirmed to be the source of electrostatically induced shock, options for mitigation were identified and assessed for feasibility. Results were presented to the client who then developed specific plans for implementation.
(Keywords: Transmission, Nuisance, Public, Shock, Right-of-Way, Right of Way, ROW, Contact, Electric, Magnetic, Fields). | |
 | High Voltage Testing Support: Developed 500 kV hardware corona test specifications and witnessed testing to ensure adequacy. Early in the testing, problems with the laboratory process were identified that would have led to an inadequate test regimen. Developed additional test procedures to confirm the problem. Prepared an impromptu analysis and presentation to explain the problem to the laboratory staff and made recommendations to mitigate the situation. The staff were convinced of the issue and altered their procedures and laboratory setup.
(Keywords: EHV, Transmission, Overhead, Corona, Hardware, Testing, Witness, Representative, Owner’s). | |
 | Expert Witness in Public Utility Commission Hearings: Provided expert witness testimony regarding project electric and magnetic fields during public outreach meetings and during formal hearings before the South Dakota Public Utility Commission (PUC). Collaborated with clients and their legal representatives to prepare statements and answers to anticipated questions from opposing groups. Topics included EMF induction, impact on health and medical implants, radio communications, and impact on dairy and farm operations. Testimony contributed to a successful outcome with the PUC approving the transmission project.
(Keywords: Overhead, Transmission, Public, Testimony, Outreach, PUC, Expert). | |
 | ±320 kV, ±500kV, and ±600 kV DC Studies: Completed DC line insulation coordination studies for lightning, contamination, and bipole failure coupled transients. Completed conductor optimization based on electrical losses and voltage drop. Analyzed electric and magnetic fields and corona performance.
(Keywords: HVDC, Transmission, Overhead, Studies, Design, Analysis, Insulation, Coordination, Optimization). | |
 | EHV Underground Cable Derating due to Steel Pipe: Performed studies to estimate ampacity reduction of 5000 KCMIL underground cable due to enclosing steel pipe required for a railroad crossing. Finite element simulations were performed to calculate eddy current and hysteresis losses in the steel pipe. The thermal impacts from these losses resulted in significant derating of the cable. Options for mitigation were then evaluated.
(Keywords: Underground, Cable, Rating, Derating, Capacity, Steel, Pipe, Transmission, Studies, Design, Analysis). | |
 | Short Circuit Force Analysis: Calculated short circuit forces and displacement for closely spaced overhead wires with special clamp-on devices. The manufacturer was interested in swing severity for a compact catenary installation of their devices. A numerical simulator was developed which modeled electromagnetic and kinematic equations to determine conductor and device acceleration, velocity, and position based on dynamic forces from asymmetrical fault currents. Results were validated with independent software.
(Keywords: Short Circuit, Forces, Transient). | |
 | Cable Termination Failure Analysis: Performed root-cause analysis for failure of an EHV cable terminator. Prepared a detailed 3D model of the cable terminator and completed finite element electromagnetic analysis to evaluate the failure hypothesis of other experts. Presented findings and successfully refuted the hypothesis. As a result, the company represented was not named in subsequent litigation.
(Keywords: Underground, Cable, Termination, Equipment, Failure, Investigation, Root Cause, Litigation). | |
 | Power Transformer Failure Analysis: Performed root cause analysis for failure of a 300 MVA power transformer. This involved detailed finite element analysis and transient simulation to assess interactions between the interconnected grid and transformer windings. The study successfully ruled out external system factors and allowed the client to focus their attention on other causes, ultimately finding the cause to be manufacturing deficiencies.
(Keywords: Transformer, Equipment, Failure, Investigation, Root Cause, Litigation). | |
 | 230 kV Cable Termination Construction Error: A cable termination construction error left questions about the long-term viability of the resulting hardware configuration. However, correcting the problem would delay construction. On short notice Mr. Leman performed a 3D electromagnetic field analysis of the new configuration to confirm that it would not be a problem and that construction could proceed.
(Keywords: Construction, Error, Investigation, Cable, Termination, Field Analysis). | |
 | Lightning Performance of Unprotected Spans: The shield wire of one span of an existing 115 kV line had to be removed to allow crossing of a proposed 345 kV transmission line. This left the span only partially shielded from lightning strike. A detailed statistical analysis was completed to confirm a negligible drop in reliability of the overall line segment given statistical lightning data for the region.
(Keywords: Lightning, Performance, Flashover, Reliability). | |
 | Parallel Circuit Interactions: Performed analysis to evaluate electromagnetic interactions between four parallel circuits carried on the same structure for several miles. Despite better shielding from direct lightning strike, insulation on the lower voltage circuits had to be increased and arresters had to be installed to prevent a drop in reliability one the lower voltage circuits due to lightning back-flashover and 345 kV switching transients.
(Keywords: Lightning, Parallel, Circuit, Transient, Induced Voltage, Backflashover, Insulation, Reliability). | |
 | NESC 5 mA rule Analysis: Completed electric field analysis to determine the minimum clearances to meet NESC 232C.1.c for vehicles parked under a proposed 500 kV transmission line at a highway crossing and over agricultural land. Researched vehicles sizes allowed by the Department of Transportation and worked with client to determined credible cases for study. Calculated the contact currents to which people could be exposed if touching the ungrounded chassis of the vehicle while standing on the ground.
(Keywords: Overhead, Transmission, Electric, Fields, NESC, 5 mA, Rule, Contact, Current, Induced, Capacitive). | |
 | Offshore to Underground Cable Transition Magnetic Field Assessment: Calculated magnetic field strength for various configurations of a high voltage cable as it transitioned from offshore, under a beach, into a vault, and to terrestrial underground trench. Analyzed various means of shielding to minimize field exposure to pedestrian traffic.
(Keywords: Underground, Cable, Offshore, Magnetic, Fields, Shielding). | |
 | 345 kV Parallel Circuit Resonance: Proposed line connected shunt reactors on a 345 kV transmission line had the possibility of 60 Hz series resonant coupling with capacitance to parallel lines. This could have resulted in dangerous voltages on the shunt compensated lines, even when terminal breakers were open. Analysis was performed to identify resonant frequencies and determine what voltages could be present on the deenergized lines. Results were used to inform shunt reactor sizing.
(Keywords: Overhead, Transmission, Parallel, Resonance, Reactive, Compensation, Shunt, Reactor, Line-Connected) | |
 | Cable Splice Failure Investigation: Investigated the cause of failure of a 69 kV cable splice. The splice of one phase failed after about 10 years of operation. This was replaced by the owner. A short time later the splice on another circuit failed. Investigation found that the sheath was improperly grounded resulting in a floating potential condition that exposed portions of the splice to potentials and electric fields above rating. This was demonstrated with simulation.
(Keywords: Underground, Cable, Splice, Failure, Investigation, Sheath Voltage Limiter, SVL, Bonding, Electric, Field). | |
 | Substation Insulation Coordination: Completed analysis to identify BIL/BSL levels at a nuclear power plant substation. Time domain transient simulations were completed to identify overvoltages from switching operations and lightning strikes to the incoming transmission line. Identified protective margins and impact of distance between arresters and protected equipment.
(Keywords: Substation, Insulation, Coordination, Lightning, Transients, Protective, Margin). | |
 | High Voltage Corona Impacts on Radio Telescope: Calculated the radio noise from an HVDC transmission line and from DC field enhanced corona on a parallel AC transmission line. Provided design recommendations to minimize noise and reduce risk of impact to a nearby radio telescope research station.
(Keywords: Overhead, Transmission, Radio, Interference, HVDC, AC). | |
 | Parallel Pipeline Induced Voltage Screening Study: The proposed route of a 345 kV underground transmission line paralleled a gas pipeline for about 500 feet. Induced voltage analysis was completed to determine if more detailed study was necessary to assess the risk of step and touch potentials and AC corrosion effects.
(Keywords: Underground, Cable, Parallel, Pipeline, AC Intereference, Screening). | |
 | Perpendicular Pipeline Crossing: The proposed route of a 34.5 kV windfarm collection feeder crossed under the right-of-way of an existing CO2 pipeline. Electromagnetic analysis was completed which identified the soil resistivity conditions and spacing constraints to prevent exceeding corrosion thresholds for induced current in the pipeline.
(Keywords: Underground, Cable, Perpendicular, Pipeline, Crossing, Induced Voltage, Corrosion). | |
 | Subtransmission Reliability Assessment: An unshielded subtransmission line was experiencing a high outage rate. A statistical flashover analysis using detailed historical lightning data near the line route identified direct lightning strike as the cause. Adding a shield wire was not cost effective so analysis was completed to specify arresters to mitigate the reliability problems.
(Keywords: Overhead, Transmission, Lightning, Reliability, Arresters, Shielding). | |
 | Induced Voltage Arcing Severity: Electromagnetic coupling from a parallel 345 kV line caused induced voltages on a nearby 230 kV line, even when the 230 kV line was deenergized. Induced voltages and currents were calculated. A model of air arcing was used to estimate the size of arcs expected when removing personal safety grounds and opening switches or cutouts after completing work on the deenergized line.
(Keywords: Overhead, Transmission, Induced, Voltage, Arcing, Worker, Safety, Parallel). | |
 | Electrostatic Impacts on Metal Clad Building: Completed analysis to assess the electrostatic effects from a 138 kV line on a metal-clad manufacturing building in the proposed right-of-way. This involved calculating the expected contact currents that could be experienced by someone touching the building after the line was constructed. The utility was advised on required clearances and options for mitigating contact currents.
(Keywords: Overhead, Transmission, NESC, 5 mA, Building, Metal Clad, Contact, Current, Short Circuit). | |
 | Fuel Ignition Risk Assessment: The proposed route of a 230 kV circuit with 69 kV under-build passed over a gas station. A 3D electromagnetic analysis was completed to identify conditions that could result in risk of fuel ignition due to electric discharge caused by capacitive effects from the overhead lines.
(Keywords: Overhead, Transmission, Fuel, Ignition, Spark, Electric, Field). | |
 | Industrial Transformer Failure Analysis: Assessed a series of industrial transformer failures at a chlorine processing facility. The most likely cause was high-frequency re-ignition transients due to interaction between the transformer and nearby vacuum circuit breakers. A detailed computer model was developed to confirm that system electrical behavior matched observed failure characteristics. This allowed the transformer manufacturer to show it was an operational problem, not a manufacturing problem. Mitigation with snubbers was then demonstrated in simulation.
(Keywords: Transformer, Industrial, Equipment, Failure, Investigation). | |
 | Research: Analysis of Transient Overvoltages Accounting for Corona Loss: Developed a program to efficiently compute transmission line transient overvoltages while accounting for corona loss attenuation. The calculations are based on the finite difference time domain (FDTD) method which inherently returns a detailed voltage profile along the line at each time step. The program was used to create detailed switching overvoltage statistics.
(Keywords: Research, Switching, Transients, Bulk, Overvoltage, Profile, Corona, Lossess). | |
 | Research: Quasi-electrostatic Simulation Method: Developed a charge simulation approach called the Fourier Enhanced Charge Simulation Method (FEnCSM) which efficiently solves charge distributions given voltage boundary conditions. The method allows explicit modeling of each subconductor in high voltage transmission lines.
(Keywords: Electromagnetics, Charge, Simulation, Electric Field). | |
 | Research: Improved Critical Flashover Voltage Calculation: Used the Fourier Enhanced Charge Simulation Method to model leader and streamer propagation between phases of high voltage transmission lines. The simulations allowed detailed calculation of transmission line phase-to-phase critical flashover voltages. These results were related to steady-state transmission line capacity via Poynting’s theorem in order to provide a more explicit link between flashover performance and transmission line capacity.
(Keywords: Overhead, Transmission, Critical, Flashover, Voltage, Leader, Streamer, Breakdown, Reliability, CFO). | |
