Thursday 21 December 2017

Deepest tunnel system to ensure power supply to Singapore

Transmission Cable Tunnel Project: Giant tunnels to safeguard power supply network
$2.4 billion effort to house 1,200km of cables is among deepest such projects worldwide
By Jose Hong, The Straits Times, 20 Dec 2017

A warren of giant tunnels which will safeguard Singapore's electricity supply network for the future has been completed.

The multibillion-dollar effort to house 1,200km of extra-high-voltage cables - more than thrice the distance between Singapore and Kuala Lumpur - is one of the world's deepest electricity supply projects.

Singaporeans will begin tapping this electrical source from next year, said energy utility company SP Group yesterday.

Given the depth, it will be easier to monitor and replace cables inside these tunnels and carry out upgrading works in the future, experts said.

Most tunnels will be about 60m beneath the earth - the height of a 20-storey Housing Board building - but some will be at 80m, the deepest among any tunnels here.

"We had to build 60m deep because Singapore lacks space. We had no choice," said Mr Michael Chin, SP Group's managing director of infrastructure and projects.

"If you look at the profile of Singapore, we have the MRT, which is 30m to 40m deep, then you have your Deep Tunnel Sewerage System, which is between 20m and 55m, so we 'choped' (saved) our space at 60m," said Mr Chin.

The three tunnels are named the North-South, East-West and Jurong Island-Pioneer tunnels, and work on the $2.4 billion project started in 2012.

SP Group said the high-voltage cables in the tunnels will mainly replace eight circuits running north and south or east and west across the country. These eight circuits, built in the 1980s, are the oldest transmission cables still in use here.

The laying of cables, which will begin early next year, is projected to be completed by 2022. The first cables will go online by the end of next year.

About 500km of cables will be laid, which is less than half the capacity of the tunnels.

They will supply about 20 per cent of Singapore's peak demand, which last year was 7,149MW, according to Energy Market Authority (EMA) data.

EMA also projected electricity demand to rise by about 2 per cent a year. The impact of the project on electricity prices is expected to be minimal.

Mr Chin said: "The immediate goal of the cable tunnels is to replace our ageing cables."

But, referring to the extra cable distance they can provide, he added: "We are also meeting Singapore's future needs."

For most of their distance, the tunnels are 6m in diameter, about two storeys high, but at junctions, they swell to 11m - the height of about three storeys.

The cables' lifespan is 30 years, and they can be replaced up to four times inside the tunnels.

Crucially, they will be much easier to replace than cables that currently run under roads and require traffic to be disrupted as engineers dig up and cover the streets.

Said engineer Teo Chor Kok, a council member of The Institution of Engineers, Singapore: "With the cable tunnels, it is very easy for SP Group to do any cable works or upgrading with minimal disruption to traffic and Singaporeans."

He added: "It is very difficult to monitor cables when they're under a road... Now, you can just go inside the tunnels with your equipment."

He said that one way SP Group could make the tunnels even better was through leasing space inside to telecommunications companies.

"They could lay optic fibre cables inside to allow massive kinds of infrastructure for other services," said Mr Teo.

Tunnel system replaces ageing network of the 1980s
By Jose Hong, The Straits Times, 20 Dec 2017

Eight circuits of the power cable network, which were built in the 1980s, will soon become too old to maintain and will be left in place while being gradually replaced with the new tunnel system.

These cables were installed just below roads, and repairs and replacement work would cause traffic jams and increase the risk of accidents - problems that the new underground tunnel network will avoid, said SP Group managing director of infrastructure and projects Michael Chin.

He added that the existing cables are so old that they need to be inspected once every three months, which adds to maintenance costs.

Singapore's land scarcity means that SP Group had "no choice" but to build the tunnel system 60m below ground, said Mr Chin.

He said that the 60m-deep tunnels mean that cable checks will not disrupt ground-level life.

Reflecting long-term planning, Mr Chin said the 40km tunnel project is designed to last 120 years. This refers to the concrete segments and the structural reinforcements.

However, he said that there is no knowing what will happen once the system ends.

"I will not be around and you will not be around," he chuckled, adding that Singapore could end up with a completely different system of transmitting electricity.

Robots on the lookout for water leaks and fires
Automatic inspection vehicles will be traversing the length of the 40km tunnels
By Jose Hong, The Straits Times, 20 Dec 2017

Singapore's new electricity supply tunnels have the latest high-tech sensors to detect water seepage, fires and infiltration that could harm the electricity network.

Robots, or automatic inspection vehicles (AIVs), traversing the length of the 40km tunnels, will look out for changes in the colour of the concrete walls, a warning sign for water leaks.

Mr Michael Chin, managing director of infrastructure and projects at energy utility company SP Group, said yesterday that water leaks are the most common problem in tunnels, and AIVs can detect concrete patches that suddenly turn a different colour.

He said the AIVs will also eventually be able to detect fires using infrared cameras.

Each of the three tunnels also has a firefighting system that uses a superior "water mist system", instead of sprinklers, said Mr Chin.

He explained that the system shoots very fine water mist which evaporates faster and removes heat quickly from fire. The water mist also displaces air and suffocates the flames.

Smoke particles will dissolve into the fine water droplets and sink, leaving a fine mist and making it safe for firefighters to enter the tunnel to put out the fire, said Mr Chin.

The system also sends an alarm signal to the Singapore Civil Defence Force.

Another set of sensors in the tunnels can detect pollutants and abnormal concentrations of gases.

Most parts of the multibillion-dollar Underground Transmission Cable Tunnel Project are about 60m beneath the earth, but some will be at 80m, making the electricity project one of the world's deepest.

The tunnels - named the North-South, East-West and Jurong Island-Pioneer tunnels - will be able to house 1,200km of extra-high-voltage cables. Singaporeans will begin tapping this source from next year, said SP Group yesterday.

About 500km of cables will be laid, which is less than half the capacity of the tunnels.

There will be 17 equipment buildings spanning the 40km network, and each of them will have two electric bicycles to allow staff to quickly move to parts of the tunnels that require attention.

Mr Chin said that anyone trying to enter the tunnels will need to break through three layers of security at the equipment buildings.

"All these systems protect the cables and the people working in the tunnel and so, in the long run, maintain the reliability of the system," he said.

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