Editorial

by Alex Apostolov, Editor-in-Chief

The Next PAC Revolution

The history of protection, automation and control of the electric power system is more than 170 years old. And we all know that an unavoidable part of history are revolutions.

At the beginning of the industrial revolution were the machines. Everything was mechanical until the invention of electricity. That was the second industrial revolution and the beginning of electric power systems and accordingly – power systems protection and control.  

The first protection devices were mechanical or electromechanical and over the years they became more and more advanced and sophisticated. And many of them we can still see on panels in thousands of substations around the world.

The first PAC revolution started with the invention of the transistor and other electronic components which allowed protection device designers to develop solid state relays with no moving parts. However, since these devices were not much smarter than the electromechanical relays and they were suffering components failure and other problems, their acceptance by the industry was not that enthusiastic.

Fortunately not long after that, the microprocessors were invented starting the new computer revolution that dramatically changed the world. Programmable logic controllers became commonly used for the control of industrial processes. The protection and control industry had a new set of tools to use to start the second PAC revolution – the transition from Dumb Electronic Devices (DEDs) to Intelligent Electronic Devices (IEDs).

Like any revolution it was not easy. While there were some people that were pushing it and being excited about it, there were still many that believed that protection should be done using electromechanical relays only. It took about two decades for multifunctional IEDs to become the typical PAC technology all over the world.

And just when many people thought that this is it, now we are going to spend the rest of our professional lives using protection IEDs, a new technology had started the third revolution in protection and control. This is as a result of the explosion of communications that has overtaken all aspects of our lives. We now have in our pockets intelligent electronic devices that do everything we need and can talk to anything we use (maybe not exactly, but this is where it is going.) And while with the microprocessor based PAC devices everything is still in a box, this new revolution is killing the box and replacing it with an App.

All of this is possible based on the IEC 61850 definitions of GOOSE and Sampled Values that allow function elements distributed between different IEDs or substation grade computers to talk to each other and based on this information exchange to work as a team implementing different distributed PAC functions.

The sampled values are one of the main components that provides the analog interface with the substation process by publishing the current and voltages samples over the substation process bus. Any device that needs to measure some electric system parameter can subscribe to any of the sampled values.

As a result now we can talk about the digital substation where all the copper cables used to bring the currents and voltages to the protection relays or IEDs are now replaced with fiber optic cables. These shared sampled values however require a shared understanding in the PAC community in order to overcome the fear of the new technology and take full advantage of the tremendous benefits it brings.  

“The revolution is not an apple that falls when it is ripe. You have to make it fall.”

Che Guevara

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