What is islanding? The power grid is the backbone of our economy behind the scenes. It is an essential infrastructure that connects power generating stations, transmission lines and complex distribution networks powering our homes, industries, etc. That’s why the reliability of such a large system becomes critically important. There are numerous protection systems and equipment that ensures the stability and reliability of the power supply in the grid.
But what happens when a certain part of the grid experiences a major fault, or a natural disaster strikes? The smaller fault leads to a major fault threatening a nationwide blackout due to cascading effect. That’s why Islanding in power system steps in as a crucial technology to protect from cascading and major blackouts. In this detailed article, we will learn about Islanding and it’s importance in power systems.
What is Islanding?
Islanding refers to a condition where certain part of the grid, including both generators and load, gets isolated from the main grid but continues to be energized through the local Distributed Generators (DGs). It is an undesirable condition in the grid operation but in certain situations, Controlled Islanding can help prevent major blackouts and improve system reliability.
Islanding can occur intentionally as well as unintentionally. But whenever islanding occurs, it should persists only for a very brief period of time. Also during the islanding, it is necessary to maintain the outputs of all the distributed generators very close to the load demand of the islanded portion.
The isolated part of the grid during widespread grid disturbance is called an Island. The disturbance created in the grid does not affect this island as it is electrically isolated from it. Islanding allows critical loads, such as hospitals, airports, and essential administrative facilities, to remain operational during grid disruptions. This is extremely important in emergencies where continuous power supply is required.
How Islanding Works?
Islanding can be intentional as well as unintentional. In both ways, it ensures continuous power supply in the Islanded area. The Grid is an interconnected network of Generators and Transmission lines, which feeds power to the local power distribution networks. All the generators in the grid runs in synchronism connected through tie lines that can transfer power to various areas. Tripping of such transmission lines create unbalancing between the power generation and load demand causing swing in grid frequency beyond certain permissible values. This swing in parameters can cause cascaded tripping effect and can lead to major blackout.
Islanding system is designed in such a way that, during major grid disturbances, the essential portion of the network gets electrically isolated from the grid and continues to be energized by the local generators connected in the grid. This local generators can vary from small generators like DG sets, to large power stations.
Importance of Islanding in Power System
1. Increased System Reliability
Islanding allows critical loads, like hospitals, airports, local administrative services, etc. to remain operational even during grid disturbances. While major part of grid experiences outage due to disturbance, islanded continues to remain operational by being isolated from the grid and getting powered by local distributed generators.
2. Disaster Resilience:
In natural disasters prone regions, islanding capability acts like a lifeline. Communities with islanding capabilities can isolate themselves from the grid during the disasters like hurricane and earthquakes, and can run on local generation to maintain essential services.
3. Safeguarding Against Cyber Attacks
In an era where cyber threats are increasing rapidly, power grids are among the most critical infrastructures vulnerable to such attacks. Modern automated smart grids are prone to cyber attacks that targets sensitive areas causing disruption in supply to the critical services. Islanding capability in these areas can protect them against such threats and allow them to run on their own local power generation facility.
4. Grid Stability
During major faults or disturbances, intentional islanding can prevent cascading failures across the grid, limiting the scope and impacts of a major blackout. One major reason for large blackout is due to sudden swing in grid frequency, which is caused by unbalancing between the Power Generation and Power Demand.
5. Quick Restoration After Major Blackout
One major advantage of islanding is that some portion of the grid can still remain energized even during major grid disturbance. It can help supply startup power to the Power Stations in order to restore the system. As we know that major thermal power plants require electricity during the light-up process. Hence it is easier to start the system from islanded state compared to entire blackout state.
Challenges
While islanding offers numerous benefits, it also comes with certain challenges:
1. Maintaining Power Quality
In islanded mode of operation, it is difficult to manage load demand to the power generation balance. Mismatch between these two can cause fluctuations in voltage and frequency of the island.
2. Safety Concerns
Unintentional islanding can pose risks to utility workers during maintenance, if they are unaware that the section of the grid is still energized.
3. Grid Reconnection
Synchronizing the islanded portion with the main grid after the restoration requires precision. Any mismatch in the parameters during synchronization can cause equipment damage or power quality issues.
4. High Implementation Cost
Setting up islanding systems, advanced detection mechanisms and control systems is expensive, particularly for large scale applications.
Real-World Applications of Islanding
Hospitals, data centers, military bases, etc. often employs such microgrids with islanding capabilities to ensure uninterrupted power supply. Also, large industries with high energy demand often use islanding systems to prevent their production losses during grid disturbances. Off-Grid solar is also an example of islanding system for small scale applications.