by Alex Apostolov, Editor-in-Chief

The Grid of the Future Challenges for Protection, Automation and Control Systems

We have talked many times about the changing electric power system industry and now we are getting back to this topic from a different point of view. We are already seeing trends that give us a good idea about what the Grid of the Future will look like. And it will be very challenging for PAC systems as we know them.

The idea behind focusing this issue of the PAC World magazine on the Grid of the Future and its impact on protection, automation and control systems is to look at the new realities and emerging technologies which have not been considered at the time when the electric power grid was built as we know it. If we think about the characteristics of the existing grid, we can summarize them under two words - relative certainty.

What does that mean? Here are a few examples:

  • The non-variable generation is connected to the transmission system in order to deliver power from the generating stations to the load centers
  • The transmission and distribution systems have parameters determined by the construction of the transmission and distribution lines and their conductors
  • The distribution system is radial, with the only source being the transmission system connected on the high side of the substation transformers
  • The fault currents are determined by the synchronous generators, the system topology and its parameters

This made it possible to develop analysis tools that allow us to properly simulate and study the behavior of the electric power grid under short circuit faults and other abnormal conditions, as well as to create advanced protection algorithms that can detect these conditions and return the system to its normal state. 
When you look at the articles in this issue of the magazine you will see how this is all changing. The non-variable and centralized thermal power generation base on nuclear and coal is disappearing and being replaced with the variable and often distributed wind and solar generation with inverter based interfaces to the grid.

Existing protection principles simply are not designed to work in such non-deterministic environment when we do not know which resources will be in service at what time and what their fault contribution will be available for what period of time even when they are in service.
Emerging technologies that allow the system operator to control the power flow in the system by dynamically changing the line impedance represent a powerful tool.
However, this will have an impact on the main protection principle used globally at the transmission level - the distance protection.

The dynamically changing line impedance will need to be understood and communicated to the distance protection elements in order to allow them to adapt their characteristics in order to be able to perform the required protection functions.

The protection of the distribution systems will have to change as well. The traditional non-directional inverse time coordinated characteristics will have to be replaced with communications based protection schemes and supervised by directional elements in order to ensure the selectivity of the protection schemes and reduce the fault clearing time to support the ride-through characteristics of the distributed renewable generators.
These are just a few examples of the changes that protection, automation and control systems will need to make in order to meet the requirements of the grid of the future.

"The best way to predict the future is to create it!"

Abraham Lincoln

BeijingSifang June 2016