Understanding Electrical Power System
The National Electricity Market is an ever evolving market that is designed to ensure market competitiveness and consumer benefits. Its complex mechanism makes it difficult for more people to understand at a glance. I’ll make it simple by focusing on the electrical aspect of the power generation.
In any electricity market, the core components are generator (e.g. gas fired, waste to energy, solar), power system operator (Singapore Power), and energy consumers.
This is power system in its simplest form. To make up the entire electricity network, consider the situation with more generators and consumers. The power system will look like this.
This model is dangerous as the power system relies on one single path to distribute electricity to the consumer, therefore, an additional distributor is required to ensure redundancy.
This is the typical power system that you would expect in the islanded environment with centralized electricity generation. This power system is unreliable and unscalable. In the event where there are more generator connecting into the system, the upfront system investment is heavy. To solve these problems, we introduce a transmission layer, which is an inter-connected high voltage network (e.g. 132kV) to transmit power over long distance. The distribution lines will be used to transmit power at lower voltage level.
The transmission layer will connect all the generators to all the distribution network via high voltage network. This is akin to expressway where cars can travel at higher speed. There is also an option to connect power from two different transmission stations into one distribution station. This is usually the case for power-critical situation, such as military, airport, etc.
This is the traditional model of electricity distribution, which needs to change with the penetration of solar power, wind power, and smaller local onsite generation. In this case, I will introduce a new component called electrical bus bar.
So what is electrical bus bar? Many of you will be familiar with the distribution box at home.
This is how the wiring diagram looks like internally
Imagine this for the distribution network, this is how it will look like (simplified). Note that I’m leaving out many other electrical components for ease of explanation.
Supposed I install solar panel on my rooftop (5kW solar panel), and my power consumption is 3kW. This means that I’m exporting 2kW out to the distribution network. Assuming that you are allowed to export power to the grid, this is what happens.
As you can see, using solar panel not only reduces the demand from the grid, but it also supplies surplus power supplies to neighboring houses. The pre-requisite is to have 2-way energy meter and approval from grid operator. This concept is similar for wind turbine. (I’m converting all DC output to AC output before connecting to the bus bar). For the case in urban environment, wind turbine is not cost effective and hence not a suitable energy source in Singapore.
Putting renewables, power generators, consumers, transmission and distribution network, the resultant power system is as below.
In Singapore, the main power generators are Senoko Energy, Tuas Power and Power Seraya (~60% of electricity market). The transmission and distribution lines are owned and operated by Singapore Power Power Grid. Residential solar panels are built onto the rooftop, which may or may not be owned by the building owner. Despite significant growth rate, renewable penetration in Singapore remains at low level — less than 3.2% of total electricity generated, as shown below extract from Energy Market Authority — Singapore Energy Statistics 2016.
I’ll elaborate more on the renewable energy, electricity pricing, and other power-related issues in the next few weeks. Subscribe to the news article via my RSS feed.
Feel free to leave any questions in the comment section. I’ll answer accordingly.
