How Singapore's electricity is generated and delivered to homes

From source to switch: How energy gets to your home
Timothy Goh finds out how Singapore's electricity is generated and delivered to homes
The Straits Times, 5 Oct 2019

STAGE 1: THE FUEL

Singapore's electricity journey begins overseas, from where its main source of fuel for electricity generation - natural gas - is imported.

Natural gas provides 95 per cent of the energy required for the nation's electricity generation needs. The rest comes from coal, petroleum and other sources such as solar energy.

In 2017, about 72 per cent of Singapore's natural gas was piped in from Indonesia and Malaysia, while the other 28 per cent was imported from other parts of the world in the form of liquefied natural gas (LNG).

Singapore LNG Corporation owns and operates Singapore's only LNG terminal.

LNG consists primarily of methane cooled to minus 161 deg C, which reduces its volume by 600 times and makes it cost-efficient to transport over long distances. It is also non-flammable, making it safer to handle than in its gaseous form.

ICEFALL IN SINGAPORE

Ships carrying the LNG dock at the LNG terminal's jetty on Jurong Island, where mechanical arms known as marine loading arms stand ready to connect to the vessel.

The LNG is pumped through these arms, which must first be cooled using very cold gas. This is because LNG itself is very cold, so if the arms are not cold enough, the temperature of the LNG will cause them to contract and get crushed.

The cooling process causes ice to form on the loading arms, even under Singapore's hot afternoon sun. A hazard sign in the area warns workers of falling ice.

The entire process of berthing the ship and unloading the LNG can take around 24 hours. The LNG is then stored in four massive storage tanks, each large enough to fit two Airbus A-380s inside. The largest tank has a capacity of 260,000 cubic m and can store the equivalent of a fortnight's energy consumption for Singapore.

Before the LNG can be used by the power plants, it first has to pass through vaporisers, where seawater is used to raise its temperature and turn it back into gas. During normal operations, seawater flows through some of the vaporisers at 4,000 cubic m an hour, which would fill an Olympic-sized swimming pool in 38 minutes.

Once the LNG has been turned back into gas, it is sent to power plants through a network of pipes.

STAGE 2: THE POWER PLANT

Electricity for mass consumption in Singapore is generated primarily by seven power plants, one of which is Keppel Merlimau Cogen (KMC). Located on Jurong Island, KMC generates electricity through what is known as combined cycle gas turbine technology and has the ability to inject 1,300MW of electricity into Singapore's energy grid.

Though there are slight differences in the way each power plant operates, they generally follow the same process: Oxygen from filtered ambient air is mixed with fuel - typically natural gas, but sometimes diesel - and ignited in a chamber.

This ignition creates a state of high pressure and temperature - over 1,000 deg C - and the hot, pressurised mixture of air and natural gas is channelled to the blades of a gas turbine, causing them to rotate. A generator converts the energy from the blades' rotation into electrical energy.

Hot exhaust gas that exits this turbine is further channelled into a heat recovery steam generator (HRSG), where it is used to heat treated water, turning it into superheated, high-pressure steam. This steam is sent into a steam turbine, causing its blades to rotate. The energy from this rotation is once again converted into electrical energy. The steam is then cooled with a stream of seawater, and the condensed water from this process is reused in the HRSG.

This combined cycle power plant system ensures that input energy is maximised and not lost at each stage of the process.

The electricity generated from this system travels through a transformer, where voltage is "stepped up" or increased to 230kV or 400kV in preparation for its injection into the main power grid. Though electrical sockets in Singapore are supplied with only 220V to 240V of energy, "stepping up" the voltage is necessary to reduce energy loss as the electricity travels long distances.

After passing through the power plant's electrical substation, which acts as a monitoring point and safety switch in case of an emergency, the electricity enters Singapore's main power grid.

STAGE 3: THE POWER LINES

A network of cables 27,790km long, more than the distance from Singapore to San Francisco and back, stretches throughout the island's underground, connecting consumers to the power plants.

If these cables serve as "roads" for electricity to travel through, then energy utility firm SP Group's underground transmission cable tunnel system can be thought of as a "highway" linking many of these roads.

While regular cables, also known as direct buried cables, are buried 3m underground, the underground transmission cable tunnel system is much deeper. At 60m to 80m below the surface - equivalent to the height of a 20-storey building - it does not conflict with MRT lines, sewerage systems or malls underground.



There are three tunnels in the system: the North-South Tunnel, which is 18.5km long; the 16.5km-long East-West Tunnel; and the 5km-long Jurong Island-Pioneer Tunnel, which connects power plants on Jurong Island to the mainland.

Each tunnel is between 6m and 11m in diameter, and their combined length of 40km is so long that people entering the tunnels have to wear radio frequency identification tags that track their location in case of emergencies. Maps and "road signs" are also located within the tunnels.

Eventually, the tunnels will be unmanned, watched over by a network of sensors and just 14 robots which can detect hazards such as fires and water leaks.

Though not all power cables run through the tunnel system, it houses 1,200km of extra-high-voltage 400kV and 230kV cables. The tunnel system makes it easier for engineers to access these cables, eliminating the need to dig up and cover the streets to do so.

The cables eventually exit the tunnel via various shafts and enter substations, where the energy flowing through them has its voltage "stepped down", and is distributed to consumers through the network.

This network of around 12,000 substations sees the power gradually "stepped down" from 400kV to 230kV, 66kV, 22kV, 6.6kV and eventually 230V in your home.

WATCHING OVER EVERYTHING: THE POWER SYSTEMS CONTROL CENTRE

Ensuring things run smoothly along the complicated energy journey is the Energy Market Authority's Power System Control Centre (PSCC), the nerve centre of the country's power system.

Its highly secured control room operates round the clock to manage the production and delivery of energy. It oversees the flow of energy from the time fuel enters Singapore until after electricity is stepped down from 66kV, at which point SP Group's distribution control centre takes over.

Three shifts of five to six systems officers each in the PSCC use a gas monitoring system to monitor the pressure and flow rate of natural gas into the power system. The system allows them to coordinate the responses of power grid operators, power stations and gas facility operators during disruptions.

The officers also use an energy management system to remotely monitor and control electricity generation plants and the transmission network. This system can forecast half-hourly system demand two weeks in advance and automatically adjust the output of generators .

Those working in shifts in the PSCC need to monitor a variety of alarms that go off throughout the day, and switch certain circuits off and on to allow workers to carry out maintenance.

Mr Chew Gim Wah, 49, a control manager in the PSCC for 17 years, said that it can be quite a stressful task. "It's 400kV (of energy in the circuits) and you can't see what's going on at the site. You need to depend on the officer there to tell you when things are clear... If anything goes wrong, it can be quite bad."

During a blackout, the officers need to restore power as quickly as possible by coordinating the responses of various agencies. For instance, if a generator trips, officers will contact generation companies to get them to ramp up their power generation to make up for the shortage. Dedicated phone lines to each of these companies are located in the control room for this purpose.

Being in the PSCC is a tiring job, but passion and a sense of duty keep Mr Chew and his team going.

He said: "Our duty is to ensure that 24 hours a day, seven days a week, we keep the lights on."

From blackouts to a bright future
It takes only a flick of a switch to turn the lights on in your home, but power is a luxury Singaporeans did not always have. Even now, electricity must first flow through a network that involves over 27,000km of cables, large amounts of seawater, robotic inspection vehicles and gas that burns at over 1,000 deg C. Timothy Goh looks at how Singapore's power network was built from scratch and how energy arrives at your doorstep.
By Timothy Goh, The Straits Times, 5 Oct 2019

Back in the day, coconut trees were one of the main culprits behind blackouts in rural Singapore.

"When it rained, the leaves would fall on the electrical wires and disrupt supply," Mr Chow Futt Yeow told The Straits Times.

Now a consultant in the electrical industry, the 83-year-old has been in Singapore's electrical industry for more than half a century.

When he joined the then Public Utilities Board (PUB) in 1963, live, exposed electrical wires ran directly underneath pavements - also known as five-foot ways - and were separated from pedestrians by a simple cast-iron cover.

Anyone working on the cables had to be very careful as accidents were common and it was easy to get an electric shock, or worse.

"You had to make sure you didn't have a pen or any potential electricity conductor in your pocket because if it dropped (onto the cables), there would be a short circuit and an explosion. You'd be gone," said Mr Chow.

He recalled how two engineers he knew were injured in explosions while replacing such power lines. In another incident, a senior engineer was injured when the meter he was using to measure the voltage of low-voltage cables accidentally touched a high-voltage cable and exploded.

Then the decision was made to switch to overhead cables, but these had their own risks.

Aside from falling branches and leaves that frequently damaged the power lines, there was a high risk of getting struck by lightning while working on the lines during a thunderstorm - and back then, there were hardly any safety procedures in place.

"Working with electricity was very dangerous. (It's) much safer nowadays... Last time, we learnt everything on the job. There were no instructions," said Mr Chow.

Mr Chow was once also a part of the PUB's rural electrification programme in the 1960s and 1970s.

The aim of the programme was to connect every kampung in Singapore to the main electricity grid. At the time, people living in then rural areas such as Potong Pasir, Tampines and Toa Payoh did not have access to much electricity.

Private operators would run diesel generators and sell electricity to households in villages for use mostly at night - to power lights.

In order to provide cheap electricity to these areas, simple overhead, bare copper wires mounted on poles were installed.

Mr Chow was involved in the planning of where and how to put up these lines so that energy could be delivered effectively.

As people at the time were very poor, some could not afford to pay for the electricity, which cost more the farther one lived from energy generation sites.

So in 1969, the PUB introduced a $1 million subsidy, which made it easier for such villagers to access electricity. The distance-based fee was also changed to a standard service fee.

Mr Chow said life in the kampungs changed as a result, with more people getting television sets and refrigerators.

By the time the programme concluded in 1974, more than 200,000 people had benefited from increased access to electricity.

Today, all of Singapore's power lines run underground, some as deep as 80m below the surface - and sophisticated machinery, sensors and robots all play a part in ensuring a safe and secure supply of power to all corners of the island.

Highly skilled workers are given the latest equipment to work on the cables, and power disruptions - if they occur at all - are resolved quickly, a far cry from the early years when Mr Chow would experience them once or twice a week.

He reflected that when he was starting out, he could not have imagined Singapore's power system being where it is today.

Tearing up, he said: "I have to say, I'm very proud... Singapore improved so fast compared with other countries. We are very lucky."



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