LineTech staff regularly contribute to industry conferences. Recently published technical papers are provided here.
We thank the Electricity Engineers' Association (EEA) for approval to publish papers presented at their conferences.
Tony Auditore, Low Voltage Conference 2016
Performing Low Voltage (LV) Arc-Flash-Hazard Assessments (AFHA) on various electrical networks presents some unique differences in the scope of network modelling and the outcome of arc-flash-risk assessment results. The paper emphasises the need to analyse all electrical supplies – normal and backup (or alternative supplies).
When calculating the overall low voltage (LV) fault current contribution to determine the incident energy under a normal operating configuration; this condition may present lower incident levels than when connected to backup distribution/transmission networks. Depending on the fault rating of the distribution/transmission networks; such contribution may be significant. This paper reviews a study case in which ‘backup’ supplies provide higher fault currents than. Provision for backup is either in the form of remote distribution systems or local diesel generation. Included in these essential supplies are DC
supply systems and uninterruptable power supply (UPS) systems. The arc- flash-hazard analysis process for this study case follows the nine steps prescribed in IEEE STD 1584–2002 and is performed in software ETAP Version 14.1.0.
Dan Tombleson, Christian Nolden, AMPEAK 2016
On Saturday, 7 February 2009, bushfires devastated Victoria, Australia, killing 173 and injuring 414. Black Saturday, as it has become known, combined extreme temperatures (46.4°C in Melbourne), high winds (over 100 km/h), and low atmospheric humidity levels (6%) at a time when Victoria was tinder dry. The subsequent Victorian Bushfires Royal Commission determined that many of these fires, including one of the most damaging, were caused by electrical infrastructure. These fires were estimated to have an economic cost over AU$4.4B.
Societal and financial impacts of this magnitude are very significant in relation to the regulated asset base of the Australian Transmission and Distribution Network Service Providers. Understanding the risk associated with such high impact low probability events is critical, yet extremely challenging for large, geographically dispersed network assets. The Directors of these businesses require a transparent view of bushfire risk management practices and their effectiveness. ElectraNet are attempting to achieve this by developing a bushfire risk model which links the potential causes, pivotal events and consequences of electrical flashovers.
An example of the value of this Asset Management tool is the highlighting of the significance of fauna as a fire start risk. This was an unexpected result. The bushfire risk model allows an entire transmission line asset base to be risk ranked using bushfire risk cost per annum. The bushfire risk model can be used to prioritise risk mitigation efforts.
Wal Marshall, Richard Steer, EEA 2016
As part of Wellington Electricity Lines Ltd’s (Wellington Electricity) ongoing work to provide cost effective risk based solutions to High Impact Low Probability (HILP) events, this paper provides an update of work between Wellington Electricity and LineTech to develop an emergency overhead lines system as a contingency plan to bypass any 33kV underground cables damaged during a major earthquake.
The concept envisaged was a set of pre-planned and fully designed emergency overhead routes between key substations, connected with overhead lines built with concrete poles.
Because the emergency line routes run in part across public parks, along paved streets etc., a system of surface mount pole foundations was envisaged to avoid excavating and damaging existing underground services, and speeding up construction of the line.
Staying of poles is not practical or desirable in many locations so a heavy duty foundation option is needed. The surface foundations will enable poles to be placed almost anywhere.
The foundations will be made of steel and weighted down with concrete anchor blocks.
Prototypes of both these foundations have been manufactured. As they are completely new and untested designs, physical load testing is needed to check if the designs would work as intended.
This paper sets out the results and lessons learned from the first round of prototype load testing on both the large and small foundation, carried out in Oct 2015 and summarises the plan to complete the emergency overhead lines system.
Richard Gibbons, EEA 2016
In the immediate past we have seen many articles, speeches and debate from the power industry on the disruptive technology the industry currently faces. Emotive claims (such as the poor will subsidise the rich) over the impact of photovoltaics (PVs) and battery storage coupled with lobbying to maintain profitability on investments appear to assume that the present industry is structured in the most logical and efficient arrangement and is deserving of protection from new competition.
The term disruptive technology was coined by professor Clayton M. Christensen from Harvard Business School in his 1997 best-selling book, "The Innovator's Dilemma". Christensen separates new technology into two categories:
- Sustaining technology - relies on incremental improvements to an already established technology. (LED Lighting could be put into this category).
- Disruptive technology - lacks refinement, often has performance problems because it is new, appeals to a limited audience, and may not yet have a proven practical application (PVs fall into this category - although they do clearly have a practical application).
Christensen argues that large corporations are designed to work with sustaining technologies. Conversely, they have trouble capitalizing on the potential of disruptive technologies, because it does not reinforce current company goals.
This paper starts when electricity was the disruptive technology and examines the structure of the industry from this time to the present against the prevailing political climate. In other words, how society impacted on the electricity industry. From this it may be possible to project a better plan for the future. Examples are drawn from the UK, the USA and NZ.
Richard Gibbons, EEA 2016
Presentation on The London Hydraulic Power Company, the first power distribution company.
Case study that accompanies the paper: Shaping the Future - Learning from the Past.
Mike Boardman, Dave Elder, EEA 2013
Historically, transmission towers were only climbed to repair or replace hardware or light members.
In recent years, formal condition assessment programmes have been introduced, whereby towers are climbed and inspected on an8 yearly cycle. This increased the amount of tower climbing considerably but it was not until tower painting of the galvanized lattice steel towers started in earnest in the mid 1990s that the numbers of workers on towers grew enormously.
The tower painting process includes a number of climbing operations including the initial assessment for painting, a number of quality assurance inspections, a final practical completion inspection and future defect liability inspections. Some of these inspections could be carried out using unmanned aerial vehicles (UAVs)
Unmanned aerial vehicles or drones have been developing in the last few years at an exponential rate. In the case of electric propulsion vehicles the advent of lighter lithium polymer power packs has helped increase payload sizes and flight duration.
The selection process for a suitable platform and accompanying recording/image capture equipment for the intended role was in itself an exhaustive exercise. Some of the aspects that were considered included the equipment cost, availability, durability, payload capacity and power consumption/flight duration.
There is a large number of helicopter type UAVs in operation around the world, with numerous configurations from single rotor (traditional helicopter style) through to multiple (up to 9) rotor platforms. The flight control systems range from a simple radio control through to complex multi facet arrangements with GPS, navigation and autonomous flight capability.
With the development of UAVs, aviation regulatory authorities have difficulty keeping up. Whilst there are no formal requirements in place currently, the company decided that working with the New Zealand Civil Aviation Authority (CAA) was essential, however it was an arduous task to finally obtain CAA approval.
Several examples of condition assessment survey work were carried out using the Cyberquad on transmission structures. There are considerable benefits of having a platform Operator (Pilot) and payload Operator who are both qualified inspectors and condition assessment specialists with many years industry experience.
Dr Tony Auditore, EEA 2013
This paper reviews the calculated electromagnetic field (EMF) values of 330kV and 500kV overhead towers for their various operating voltages and energy transfer capability. The calculated values are compared against the current Australian statutory guidelines for occupational limits. Occupational health concerns relating to live line work stem from the theory that biological effects are associated with exposure to power frequency EMF and that these occur as a result of electric current induced in the subject. Safety precautions for these frequencies are thus based on limiting field levels that may induce harmful electric current in the subject. Due to the close proximity of live line working, it is not always possible to limit these EMFs. These fields can be reduced by shielding such as live-line suits.
At the low frequency of 50 Hz, two fields exist that can be studied separately: electric fields and magnetic fields. Magnetic fields are produced by the current flowing (movement of electric charge) along a conductor. Electric current is measured in Ampere (A) and its magnitude varies depending on the power network delivery capability and number of customers (load) supplied by the system. As the load changes, the magnetic field will change. Magnetic fields are measured by both magnetic field strength (MFS) and Magnetic Flux Density (MFD). Reducing 50 Hz magnetic fields requires special engineering techniques and is generally addressed during the design phase of the overhead line. Electric fields may exist without the presence of magnetic fields. This occurs when a transmission line is energised without load – it has an applied voltage but is not conveying current.
The review assesses overhead line structure outlines and tower geometries for compliance to the Public Consultation Draft document issued by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) – Exposure Limits for Electric & Magnetic Fields – 0 Hz to 3 kHz.
A simulation model was derived overlaying the magnetic and electric field on the structure outline in sufficient resolution to assess occupational exposure at nominated positions on the structure climbing and inspection corridor as well as in other nominated positions for bare hand on conductor and working positions for live stick work. Calculated results are compared against the nominated occupational exposure limits in ARPANSA (2009 revision of draft). Several single circuit, double circuit suspension and strain pole types are provided for a narrative assessment.
Richard Gibbons, EEA 2013
This paper looks at various aspects of the power engineering industry and profession. It draws from the author’s experience and viewpoint. Topics covered include health and safety, education and training, the role of the engineer, and the status of engineers, and what is the future for engineers?
The paper draws on personal experience and knowledge as well as other sources. Personal experience goes back to 1952 when aged 4 I first visited a substation and was instantly addicted to the smell of insulating oil!
Dr Tony Auditore, Michael Swan, Earthing, Bonding, Lightning and Surge Protection 2012
LineTech Consulting was requested by New Zealand Sugar Co (NZS) to undertake a study to investigate the consequence of a direct lightning strike to the proposed replacement Stainless Steel Chimney (SSC) and insure the safety of personal working in this area. The objective of this study was not to protect the SSC from lightning. By its design, material composition, profile and location; there were no economic means of protecting the SSC against direct lightning strikes. However, this study attempted to quantify the magnitude of the possible risks that the surrounding plant and equipment were subjected to in the event of the SSC being struck by lightning. Furthermore, the study proposes mitigation measures against possible overvoltage damage in the form of effective earthing.
The CDEGS simulation concludes that an effective Lightning Protective System (LPS) as described in Scenario 2 as the best solution. That is earthing in the immediate area of the SSC with four 6m 38mm copper-coated earth electrodes. In addition, all SSC steelwork and reinforcing had to be solidly bonded.
The study proposed an effective LPS design. In addition, it proposed surge protection for all main power in-feeders that supply plant and equipment. Lastly, it also included operational safety guidelines that reduce the risk of injury to public and occupational persons.
The study included a risk assessment done in accordance with AS/NZS 1768:2007 Section 2 Assessment and Management of Risk Due to Lightning – Analysis of Need for Protection. As the acceptable risk was far less than the total risk 0.0238 > 0.00001 the results require the design of a shielding system for the SSC. It is emphasised that it is not feasible to shield the SSC from direct lightning strikes. Therefore mitigation measures have to be applied.
The above risk assessment is extremely conservative and does not take into account environmental shielding effects or any applied mitigation such as the installation of surge protection. Therefore a risk assessment based on a holistic approach has been adopted. This method applies the risk assessment process detailed in AS/NZS 1768:2007 and was calculated using the supplied calculation spreadsheet.
The spreadsheet calculations consider the following 4 scenarios:
- Lightning strikes to the SSC without any surge protection installed on the power supply or electrical equipment. Results were not acceptable with the Loss of Life risk = 3.17 E-5.
- Lightning strikes to the SSC with surge protection installed on the power supply and electrical equipment. Results were acceptable with the Loss of Life risk = 9.49 E-8.
- Lightning strikes to the Boiler House without any surge protection installed on the power supply or electrical equipment. Results were not acceptable with the Loss of Life risk = 3.74 E-5.
- Lightning strikes to the Boiler House with surge protection installed on the power supply and electrical equipment. Results were acceptable with the Loss of Life risk = 1.03 E-8.
Surge protection on the point of entry includes surge arresters at both the supply transformer (415 V side) and entry into the Boiler House 415 V mains board.
The surge protection for electrical equipment within the Boiler House is situated at the 415 V mains board. Any electrical equipment that is outside of the Boiler House and supplied from the Boiler House 415 V mains board requires additional surge protection at the equipment itself. For example: Surge protection will need to be installed on the drive of the chimney draught fan.
The boiler house adjacent to the SSC required adequate earthing. The condition of the existing earthing was not obvious due to the age of the premises and an accurate assessment would have been costly. An effective and low cost solution was to install earth electrodes on the outer four corners of the building.
Dr Tony Auditore, Tom Bammann, David Gianelly, EEA 2012
Consolidated Power Projects (Australia) was contracted by Leighton Contractors (Australia) to undertake the design for AGL/Meridian‟s Macarthur Wind Farm located approximately 14km North-West of Hawkesdale in rural Victoria Australia. The earthing studies and their detailed designs were subcontracted to LineTech Consulting (New Zealand). The wind farm comprises of one hundred-and-forty 3 MW wind turbine generators (WTG) and six 20 MVAr capacitor banks with a maximum nominal generation capacity of 420 MW. Included in this subcontract were the design of the earth grids for all 140 WTG, the Macarthur Wind Farm Substation, the 132/132 kV Tarrone Transition Station and part of the 132/500 kV Tarrone Substation. In addition to the earth grid designs, the magnetic coupling between the 132 kV Macarthur Wind Farm Tarrone 132 kV overhead line and the Port Campbell to Adelaide Pipeline needed to be studied. This examined unsafe induced voltage magnitudes on the pipeline during single phase to ground faults occurring along the overhead. The proposed paper documents the engineering process and calculation methodology for the Macarthur Wind Farm earthing designs, and lists the local and international design standards applied.
An engineering objective was to determine the distribution of fault current from the main national transmission grid 132/500 kV Tarrone Substation to each individual WTG. This fault current is distributed via two stations, two 33 kV overhead line-to-cable transition stations, and an array of 33 kV cable and overhead line networks between the Macarthur Substation and the WTG.
The final WTG design is based on a variable depth ring type of earth grid. The study concerns itself with conditions under single phase-to-earth fault operating conditions at TRTS and the due impact of induced voltage and distribution of fault current to interconnecting services such as underground cables (UGC) or neighbouring fences. The paper concludes with a summary of the salient earthing design considerations for a large scale wind farm such as Macarthur and highlights the importance of calculating the fault current distribution between UGC, overhead shield wires (OHSW) and earth return paths. A lightning frequency (Hz) sensitivity analysis is performed on various earth grid design options.
Wal Marshall, Geoff Douch, Gurjeet Malhi, EEA 2012
This paper discusses one aspect of the planning being undertaken by Wellington Electricity to prepare for a large earthquake disrupting one or more major 33kV cables in the Wellington CBD and surrounding areas. The planning includes developing conceptual emergency overhead line routes, and designing suitable poles & foundations, so the lines can be built in the shortest possible time with the least possible resource.
Dr Tony Auditore, Sam Viscovik, Chin Choo, Arc Flash Forum - IDC Technologies, 2011
Recent guidelines in NFPA 70E-2009 and IEEE Standards 1584 (2002 & 2004) regarding arc flash hazards have focused safety conscious New Zealand industries to quantify the dangers of potential arc flash events in their energised electrical assets. Contact Energy is no exception with the completion of their second power station to have undertaken an arc flash hazard analysis study. A third power station is currently under investigation.
This paper provides an overview of the process undertaken to conduct an arc flash hazard study at the Taranaki Combined Cycle Power Station. The process includes the calculation of the fault current by means of ETAP 7.5, calculation of arc flash, incident energy levels and flash-protection boundaries at the 6.6 kV switchgear bus, and mitigation proposals for reducing the arc flash hazard level. The implemented mitigation method of fast arc flash detection utilises fibre optic light sensors combined with fault current to initiate tripping which is faster than conventional time-graded relaying techniques.
Wal Marshall, EEA 2011
This paper examines the problems with the dual lanyard attachment method, and explains why permanent wire type fall-arrest systems have much better safety outcomes.
Wal Marshall, EEA 2000
To a background of change internationally, and increasing attention from OSH, the industry is re-examining the safety of traditional free climbing of power line structures.
Of the available attachment methods for towers, trials show the dual lanyard technique is the most practical. However this method comes with some significant disadvantages, not the least of which is an increased injury hazard due to added complexity.
A detailed study has shown there are no known cases of a properly trained line worker falling from a tower while using permanent climbing steps, over an estimated 3.3 million structure ascents. This makes the climb / descend process an extraordinary safe work activity. It also introduces the great difficulty that any change to current practice may impact adversely.
However falls are continuing to occur during “positioning” on the structure, and when attaching at the work position.
Therefore a partial attachment policy with the following general characteristics has been recommended for transmission line towers:
- Climbing workers to be fully trained and tested for competency.
- Workers not climbing or descending on permanent climbing steps, to be attached at all times when above 3m from ground level.
- Prior to free climbing, a risk assessment process is to be followed to determine if there are special circumstances, which elevate climbing fall risk. If the risk is significantly higher than normal, attachment would then be mandatory.
The position with regards to climbing poles is to be the subject of a separate EEA study.
Jeremy Neilson, Edward Hardie, EEA 2011
Among the many difficulties facing engineers when upgrading existing distribution lines or designing new lines the landscape often provides its share of challenges to overcome. Upon the commencement of each project or prospecting exercise up-to- date spatial information is the key to efficient and accurate analysis and decision making. Ground surveying is often difficult and costly and made more demanding by the fluid nature of route design caused by topographic or political obstacles. Satellite imagery and mapping may be timely but the accuracy will not be sufficient for the design stages. Airborne laser scanning (a.k.a. Airborne LiDAR) provides an in- between solution suitable for medium to large scale projects.
Aerial surveying is widely accepted as a means of fast and accurate data acquisition and permits applications from phase one route selection through to detailed design of new or upgraded networks. Equipment such as LiDAR with integrated camera systems enable very accurate, very detailed surveying but also has its limitations.
This paper reports on the techniques and challenges of airborne laser scanning, outlining the major benefits while identifying certain issues.
The paper then explains a couple of practicable applications where an experienced line designer has used LiDAR data to achieve accurate computer line modelling analysis. One application describes the effective use of LiDAR in a new line establishment process. The other application describes a process where LiDAR is effectively used to create an accurate model of an existing line where clearance violations are found and mitigated or where an increased electrical loading is desired for the line and legal clearance requirements are analysed.
Richard Gibbons, EEA 2011
A key issue for engineers is to understand what the board does, how it should operate and how to communicate meaningfully with directors though the senior management (CEO) of their organisation. I believe that engineers need to understand the “language” of governance and thus be able to present their engineering problems and solutions for considered review and to respond to directives/proposals so that the impacts are fully understood.
This paper considers the issue of Corporate Governance of a company and the relationship and impact this has on the activities of the engineer(s) working in that company.
The focus is companies in the electrical power industry, recognising they have their primary investment in “engineering works” be they generation plant: lines and substations; or metering and associated equipment.
Wal Marshall, EEA 2010
This paper rounds up three years of investigation, design, development, testing and field trialing of methods of earth bonding the reinforcing cages of older Vierendeel and hollow spun concrete poles which were manufactured without integral earthing systems.
Dr Tony Auditore, Chin Choo, EEA 2010
Condition based inspection prompted by thermal monitoring at Taranaki Combined Cycle (TCC) Power Plant in 2008 revealed an unexpected and abnormal buildup of pressure at the 220 kV cable sealing ends. A proactive investigation process led to a series of preliminary inspections and the application of sound engineering judgments to replace the 220 kV cable that linked between the power station and the substation.
This paper presents the initial findings from the condition monitoring inspection through to the commissioning of the high voltage cables. Despite the challenges that were encountered the cable was replaced in a timely period. The experience gained during the investigation and replacement of these cables emphasises the importance of condition monitoring and the correct analysis of results in weighing up the financial and operational risks.
Wal Marshall, EEA 2009
During 2008 the author was engaged by the Icelandic Consulting company Efla to act as consultant for a condition assessment trial project on a 220 kV transmission line in Iceland. The trial project was jointly funded by the Icelandic transmission company Landsnett, and the Norwegian national grid transmission company Statnett.
The objective of the work was to:
- Introduce a detailed condition assessment methodology to the two client companies and trial it on an actual line.
- Undertake a predictive modelling analysis on the results to see what the future work and cost profile was for the line.
The work was undertaken from October to November 2008. The author travelled to Iceland to help set up the trial and brief Landsnett and Statnett engineers. A final report was completed late December 2008.
Wal Marshall, EEA 2009
This paper updates an earlier paper presented to the 2008 EEA Conference.
It adds new information on high current testing and field installation experience.
Dr Tony Auditore, EEA 2009
Failure of overhead shield conductors in substations can result in costly plant damages and lengthy supply outages. From an international perspective, such a rare event has been witnessed within New Zealand resulting in thorough investigations into the cause and mitigation thereof. Configuring substation overhead earthconductors to eliminate busbar crossings or avoiding plant clearance reduction should an overhead shielding conductor fall is highly improbable. Possible mitigation is the replacement of existing overhead earth conductors with lightning masts.
Risk assessments rely on the probability of lightning strikes. Accurate probability estimates of lightning strikes can be made using site-specific, ground-flash density values that are based upon actual recordings of lightning data. However, results only provide an indication of lightning strike return frequency and these results cannot be considered as absolutes. Their most useful function is in determining the relative effects of lightning protection design changes made in the refurbishment of substations.
The change from overhead shielding conductors to lightning masts must effectively utilise the existing steel support structures and gantries. These structures although providing a base for attachments heights, do limit the overall design and layout of masts. Considering this, design options include the “rolling sphere method”.
Wal Marshall, EEA 2008
Part A of this paper examines the ability of preservative injection systems to increase the service life of driven timber piles.
Part B of this paper looks at methods to achieve a bond between the external and internal earthing systems.
Dr Tony Auditore, EEA 2008
The paper objectively reviews long-term planning considerations based on the concept of a “technical balance sheet” for introducing high voltage cables in distribution and transmission networks. System planning and operation has the objective of developing a transmission network of sufficient capacity with high availability and reliability at minimum cost. The installation of partial or complete underground cabling is a result of significant system planning and operational implications. Traditionally, technical limitations and cost factors of cable installations have been major considerations for installing cables. Additional considerations are: application and planning considerations; environmental constraints, comparative investments, and perspectives.
Mike Boardman, EEA 2008
The World Corrosion Organisation (WCO) places the worldwide annual cost of corrosion at US$1.8 trillion per annum, some 3% of the world’s GDP. The estimated cost of corrosion in the United States electrical power industry in 1998 was US$15.4 billion, representing about 7.9% of the cost of electricity to their consumers.
About 20% or US$3 billion of the corrosion costs were considered avoidable.
Whilst the issue of corrosion is generally understood within New Zealand industry, it is often disregarded or acknowledged to be an inherent problem with metals generally. If the avoidable cost of corrosion is established throughout the electricity industry it would help the participants to better manage their assets and benefit from longer-term cost savings.
Wal Marshall, Mike Boardman, EEA 2009
New Zealand’s transmission and distribution system relies heavily on line and substation support structures constructed using millions of tonnes of hot dipped galvanized steel. It collectively represents an industry investment worth billions of dollars. All this investment has a finite life before rusting sets in. With the average asset age now exceeding 40 years and some structures over 80 years old, zinc protection applied decades ago is now heavily depleted in many locations.
Every day hundreds of kilograms of galvanising corrodes away and is not replaced. Obviously this cannot continue forever and eventually these assets will have to be maintained or, they will have to be replaced. Either way, maintenance is set to become a growing and costly issue for the industry and a ramping up of maintenance and/or capital replacement budgets to cope is already inevitable unless reliability is to decline.
In considering the maintenance of galvanised structures, the industry has essentially three choices: It can maintain proactively, it can maintain reactively or it can replace. Depending on the circumstances of particular assets, each option has its proper place. The challenge facing the industry is to ensure that its asset management selects the correct choice for each situation. Unfortunately this rarely happens and the outcome is usually higher long-term costs; much higher in many cases.
The objective of this paper is to show that for most assets, the proactive maintenance option produces by far the lowest long-term cost; yet this is the least adopted option. This paper asks why that is and whether the industry should be adopting a more coordinated approach given the very large and growing sums involved.
Wal Marshall, Presentation to Iceland Grid Co 2009
The presentation examines the New Zealand experience of managing the maintenance of transmission lines using condition assessment and computer data analysis.
As lines age they not only deteriorate but become increasingly diverse in condition and construction, and the task of managing maintenance becomes evermore complex.
Maintenance must be able to manage diversity; detailed condition-assessment data is essential to enable sound forward planning in diverse systems without loss of reliability.
A computerised line model can give you a view of where you are going, and the costs, allow you to optimize your maintenance management to achieve the reliability and cost targets you want, allow you to value your assets consistently, and plan future resourcing.