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Wal Marshall - the 'Lines Condition Assessment Guy'

Felicity Wolfe - Fri, 11 Aug 2023 - Published on Energy News (

Lumen principal consulting engineer Wal Marshall is most proud of his work developing power line condition assessment standards for the industry during the establishment of Transpower in the late 1980s.

"I would be happy to be known as the ‘Lines Condition Assessment Guy'. It has had a huge positive impact on long-term reliability of the transmission line network.”

Following the industry reforms in the 1980s, Marshall was tasked with developing future maintenance costings for the nation’s transmission line assets. His work mapping and listing the condition of the multitude of parts of the national transmission line grid into a database and developing a forward projection of maintenance and replacement costs was industry-leading at the time.

Marshall spoke at a number of international conferences during his time with Transpower, including one in Kansas in 1997. Looking back at the presentation today, he says the concepts around using condition and environmental data to model future maintenance work and enable broad brush future costing was “definitely a world first for the lines industry and was received with great interest”.

Marshall retired from Lumen last month - “unless something interesting comes up”. He says the industry has developed considerably since he first joined the New Zealand Electricity Department as a cadet in 1971.

Early interest

Marshall’s interest in the electricity industry was sparked by a trip to the newly constructed Benmore power station as part of a school holiday programme – probably in late 1966, a year after it was commissioned.

“It was this brand-spanking new, great big power station. Everything was immaculate, it was huge, it was impressive - amazing stuff for any schoolboy.”

When considering career options after high school, he thought “what about the NZED – why not?”.

NZED offered cadetships and apprenticeships with on-the-job training and qualifications. The system worked well, Marshall says, releasing waves of young workers into the industry.

They all started with a year in one of the NZED technical training centres in Christchurch and Palmerston North learning the basics of technical drafting, machining, welding, and wiring - “so you would be useful when you came back out”.

He says it was a “fantastic system” teaching “young people how to do useful stuff”.

“There’s nothing like it today.”

The year group then dispersed across all the NZED districts – but they kept in touch throughout their careers.

Marshall, who spent the following year with the Dunedin District, says the “raw youngsters” were often tasked with digging holes and trenches. But there were also “some interesting jobs” that taught them the more technical details of their trade.

Wal Marshall - fourth from right - at a reunion of his NZED year-group in 2019: Photo supplied

Manapōuri diagnosis

When Manapōuri was fully commissioned in 1972, it became apparent a design problem was creating greater than anticipated friction between the water and the tailrace tunnel walls. The resulting excessive back pressure prevented the station running at its full rated capacity. This was resolved in 2002 with the completion of the second tailrace tunnel.

A less documented issue - that Marshall doubts many people now remember – was that the generator transformers kept overheating if run on full load.

In 1973, he was in his third year of training and working in the Dunedin electricity district for “on-site experience”. He was tasked with finding out why the Manapōuri unit transformers were overheating and told to take a car from the office pool to investigate.

“I think it was just a way of getting me out of the office for a while."

Marshall had never been to the power station before but drove to Manapōuri township and took the ferry across the lake to the new power station.

After going down the powerhouse tunnel to the generator floor he was then guided down further to the station sump - “a vast cavern I hadn’t envisaged even existed”.

He looked over the generator unit transformers which are “big metal-clad tanks”, examined the cooling system and thought about how it worked.

Water from the intake penstocks flowed through the transformers’ cooling system and then out into the tailrace.

“The pressure difference across the turbines drives water through - so it should be really reliable,” he says.

Everyone knew there was excess backpressure in the tailrace, but “there was still enough pressure difference to easily keep the transformers cool”.

“Yet there was still some problem with it.”

Air-bleed valves at the top of the transformers’ cooling system were designed to let trapped air bubbles escape. Marshall asked to see the transformer drawings to see how the bleed valves worked.

“I thought, well that’s straightforward - it's just a simple mechanical float valve.”

However, looking closely at the valves, he noted the American devices “were a fundamentally flawed design for thatlocation”. The valves could not open as the water in the cooling system was hundreds of PSI above the outside air pressure.

The system was filling with air at the top, depressing the water level and causing overheating

After a discussion with the "sceptical" fitters on site, it was agreed to test the theory by drilling a small bleed hole in the top of one valve to continuously expel a small amount of cooling water into the station sump and with it any trapped air.

“Then we put the machine on full load, and it stayed on all day – until then one of the few times that had ever happened, I believe.”

Holes were drilled in the tops of all the valves. Problem solved.

“It was as simple as that," he says. "Maybe they are still the same today.”

Back at district office, there was "more than a bit of surprise that I was back so soon with a potentially difficult problem sorted”.

Marshall says it was an example of how NZED trainees were dispersed across the wider network and "worked at the coalface”.

Substation experience

During this period, Marshall also worked on the expansion of the Roxburgh hydro dam’s 220 kV substation switchyard expansion and the building of a new 220 kV substation at Naseby.

A memorable project was rebuilding the 11 kV substation at Waitaki after a huge snowstorm caused one of the 220 kV transmission lines to sag down and flash-over to an 11 kV feeder.

The feeder switchgear was insulated with a liquid Penetrol product which “had the consistency of golden syrup”.

“Of course, put 220 kV onto 11 kV metal clad switchgear and it just blew the lid right off the bus chamber on top, and threw Penetrol everywhere. What a mess.”

Luckily, he says, no one was in the substation when the incident happened. When Marshall arrived, the substation was a concrete shell full of burnt and buckled equipment, covered in the sticky remnants of the Penetrol.

"So, we got stuck in and ripped out all that switchgear and cleaned up the interior of the building. As a temporary measure, we sourced some second-hand switchgear from the local power board, bolted it in, reconnected the old pitch terminated cables, tested and then livened it up.

“We were not sure how long it would last but it got the lights back on in the local town until new gear could be obtained.”

Then he was put to work in the district depot test-room helping build comms and protection panels. Other projects included the stator replacement in one of the Roxburgh hydro generators and later the commissioning of the Roxburgh - Three Mile Hill 220 kV line.

Working in the district office was a great experience as there were always things to do, problems to solve and solutions to think about, he says. “It was often challenging, problem-solving work - which is the type I love.”

NZED Head office

In 1976 Marshall’s final cadetship year saw him go to NZED’s Wellington head office.

After three “boring” months in the regulations section, he transferred into the Head Office Supply Branch Line Maintenance Section headed by Kevin Mackey. He ended up staying, as “head office wouldn’t approve my transfer back to Dunedin!”

Apart from a year doing his OE, he stayed in Wellington throughout his career, getting married, having a family - “all the usual things you do in life”.

Marshall says NZED at the time was “primarily a construction organisation” building power stations, substations and overhead lines.

“There was very little attention paid to transmission line maintenance,” he says.

“It was: build them and essentially walk away. If anything fails, we’ll fix it and at the end of their life we’ll just build a whole new, bigger and better one.”

That attitude radically changed following the electricity sector reforms in the 1980s. The grid had largely reached growth maturity and an entirely new approach was needed to keep it in service long term.

The change from NZED to ‘National Grid’ - later Transpower – saw his appointment as senior line support engineer in 1987. The revamped organisation applied a “completely different” focus on asset management.

From 1990 to 1997 Marshall was Transpower’s transmission line support manager, with up to eight full-time staff.

Mapping the grid

During this time Marshall oversaw the rapid development of overhead line maintenance policy, "so maintenance contractors had some guidance to work to". Additionally, the company needed a 10-year asset management plan – including matching forward-planned expenditure.

“Basically, there is an old adage which says, ‘if you can’t measure it, you can’t manage it’. We definitely couldn’t measure it and that needed fixing.”

The first task was to define exactly what the assets were, as the NZED had defined only electrical circuits which kept changing every time a new connection was made.

“We needed to define assets which would not change: This is a power line. It goes from here to here. There are X towers or poles, it is wired with this conductor and was built to a certain design and commissioned on a certain date.”

Some of this data existed in various forms. Some did not or was inaccurate.

“I can recall spending a full working day, naming every Transpower line as an asset for the first time.”

Asset conditions also needed to be defined. By then the NZED district offices had been disestablished, and there were few detailed and accessible asset lists. The only condition data that existed was in the heads of the remaining senior linemen.

“There was so little accurate line condition data. It was scandalous, really,” he says.

“Ultimately, we had to physically go to every pole, every tower, on every line, deciding how to best access them, and finding who the landowners were. Then we had to properly document everything and get it all recorded into the company database.”

Marshall also led the ongoing development within the company of standards and policies for contractors stating what was acceptable and what was not, including guidelines on tree clearances, and when poles and cross arms, conductor and all other components needed replacement.

Ongoing condition monitoring was also mandated for the first time.

“I said, ’Go out on a five-year rotation, look in detail at these assets – pole by pole, tower by tower, component by


A slide from one of Wal Marshall's asset condition presentations in the 1990s: Image supplied

The contractors were keen on the ongoing pipeline of condition assessment work ahead but, again, documentation had to be created around assessment criteria and condition coding.

“Eventually a detailed set of condition coding standards was developed and proved to be very successful.”

Building these new systems – a revolution for the company in thinking about line assets – “was a lot of work, by a lot of people both within Transpower, and also by the contractors that had to implement them".

“You would never get another opportunity like that again to really make total generational change in such a very short time frame on a nationally-owned, mission-critical set of assets.”

“Condition assessment is now routine on the transmission line network, and the basic approach developed then is still in place.”

Overseas conferences – such as the one in Kansas - were an opportunity to see how other countries were doing things – and how things could be improved back home.

Marshall says the design of equipment and loadings were done well internationally, “but long-term line maintenance management was still pretty raw”.

He decided it was possible to build a computer model using the asset register and the condition data combined with the rate of ageing of different components in different environments around the network, to help forecast future work and costs. This was possibly a “world first” at that time.

“We built for the first time a 50 -year programme of forward predicted costs built on actual structure by structure data that we knew, rather than past broad-brush guesses from field staff.”

“We were pushing the boat out a very long way.”

A 1990s presentation slide showing forward maintenance costs on the grid: Image supplied

The predictive model showed exactly what Marshall expected – a “big and growing bulge” of future spending ahead due to progressively ageing assets needing increasing maintenance to be kept in reliable service.

“I sent my cost prediction graph to the board, but never heard anything more. It was not what the board wanted to hear when the politicians were pressuring them to say how much Transpower was going to reduce its future costs.”

Live line school

During his time at Transpower, Marshall championed several other initiatives still in use today, including building and starting the Omaka Line Mechanic Training Centre in Blenheim.

“Prior to that, transmission linemen training was all on-the job, with little to no formal structure. At the end of three years’, you’re a trained lineman.”

He says establishing Omaka was made easier because Transpower planned to upgrade the interisland HVDC system and replace the original Mercury Arc Rectifiers with thyristors in the early 1990s. The DC line needed to be re-insulated to cope with the increased line voltage.

“In order to do that and not take the line out of service for six months, we needed to do the bulk of the work live line. But we had no live line skills.”

People with these skills were “imported from AB Chance in the USA” and the first courses at the Omaka centre were live line training for the project.

Training session at Omaka in 2002: Photo supplied

He also instigated the purchase of emergency transmission towers from Lindsey Systems in the United States.

Temporary towers allow fast restoration of storm-damaged and broken towers. These had frequently been used by the NZED, but mostly on the HVDC line. However as new designs, such as vertical double circuits became increasingly critical to system reliability, the older emergency structures were not always suitable.

The Lindsey tower system was quick to erect and adaptable to multiple line configurations. These have been used several times “including just a few months ago in Northland to bypass a slip-threatened tower”.

His experience with the Lindsey structures was of use to the Australian transmission utilities. As a past Electricity Supply Association of Australia transmission line engineering committee member, he was tasked with visiting each utility to explain the benefits for the companies and the transmission industry.

Marshall also took a "passionate interest" in developing tower painting.

“With so many towers in the transmission system needing to be maintained indefinitely, it was obvious to me the best long-term option was to start painting them.”

After looking overseas for the best technology, he instigated selected tower painting methods as a routine part of line maintenance.


Marshall left Transpower during an extensive reorganisation of the grid operator in 1998. At that time, management trends favoured outsourcing to consultants and contractors over in-house teams.

All his team faced forced redundancy, so Marshall decided it was time to leave as well. However, a newer team recruit, Trevor Jacobs, had only recently emigrated from South Africa with his family and didn’t qualify for much redundancy money, so was vulnerable.

He negotiated for Jacobs to stay with Transpower to oversee the maintenance contracting workflows. Marshall then set up Power Line Solutions with some of the team - Keith McCallum, Ian Baird, Ranjith de Silva, Stuart Becker, and Pat Wagner. As PLS they largely continued the work they had been doing for Transpower but as consultants.

“We worked from my home for the first 12 months.”

Early days of Power Line Solutions: Photo supplied

Marshall says a highlight of those early years was winning the best presentation award at the 2000 Electricity Engineers’ Association conference for a talk on the pros and cons of linemen attachment when tower climbing.

“I used to go to the EEA conference every year – it was a very good way of getting work, because you see everybody, and they see you.”

As a consultant, Marshall has been involved in due diligence inspections of Transpower transmission assets sold to distribution companies, and investigated line failure and safety incidents, including one fatal accident.

Marshall's transmission line condition assessment skills proved to be in demand internationally resulting in trips to Norway, Iceland and the Philippines to help local staff to develop skills, documentation and data structures required to manage their network maintenance to “state of the art” levels.

PLS was merged with Linelink in 2004, doubling their staff to 10, and the combined company was renamed LineTech.

“Linelink were guys we knew in Christchurch doing much the same work as we were in Wellington, so it made sense to get together."

LineTech broadened its work base to reduce its heavy dependence on Transpower. More engineering disciplines were brought into the company with a second rebrand to Lumen in 2019 reflecting that diversification.

“Because we had diversified, we couldn’t go too much longer with LineTech.”

Lumen, now headquartered in Christchurch, has more than 50 people across transmission, distribution, civil engineering, coatings, and energy and decarbonisation divisions.

A company office has also been set up in Adelaide.

As one of the firm’s founders, Marshall was a board member for 22 years, including a period as its chair. After stepping down he has remained as a Wellington-based principal consultant with the group.

The right industry

Marshall says he “chose the right industry” and recommends the electricity transmission and distribution sector to any trainee or engineering graduate.

“Other industries will come and go, but you still have to keep the lights on. From generation to consumer, there has to be a working system and that system requires people to drive it.”

The people in the power industry are also “very easy to work with” and usually open to new ideas.

Throughout his career, Marshall says he often presented his bosses and colleagues with new ideas that challenged previous ways of doing things. Largely, they were receptive to them.

“At the end of the day they will listen to your arguments about why this is needed and why it will improve.”

And while he is officially retiring, Marshall says he might still take on work that requires a bit of thinking outside of the box.

A fairly recent example was no-dig emergency pole foundations for Wellington Electricity. The Kaikōura earthquake highlighted the vulnerability of the distributor’s underground cables. It wanted a restoration option to quickly install temporary overhead lines between key connections if needed.

After mapping routes between the key substation locations throughout the city, it was clear some places were not appropriate for digging holes to install poles.

“For example, The Terrace. It’s just riddled with services everywhere and you’d be potentially digging them up and causing further damage.”

Instead, Marshall oversaw the design of transportable steel pole foundations that can be placed in car parks or other suitable spaces.

“You just arrive with the whole thing on a truck, place it, anchor block it down, put a pole in it and wire it.”

“Those are the sort of unusual jobs that interest me.”

Training exercise for the no dig emergency poles designed for Wellington Electricity: Photo supplied


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