by Alex Apostolov, Editor-in-Chief

It may not be what you think it is!

One of the main challenges with electric power systems protection and control devices is that they are not directly connected to the equipment that they are designed to protect. As a result what they see may not be what it really is.

The specification is the document that describes the user’s expectations. The quality of the specification has a very important role in ensuring that the system meets the expectations when put in service.

Any good specification shall be written by answering the three fundamental questions:

  • What are we doing?
  • Why are we doing it?
  • How are we going to do it?

The answer to the first question is the most important and is essential to any specification. It shall be answered as a result of detailed analysis of the specifics of the project by a team of experts covering all the basic function groups, such as protection, automation, control, communications, monitoring, recording, event reporting, power quality, etc.
The style of writing the specification is very important. It should be very clear, using short and specific sentences. It is important to describe every single detail without assuming that anything is common knowledge and obvious.
We need to make sure that there are no contradictory requirements in the specification and that all of them are achievable with the available technology.
For every requirement it is also necessary to define how it should be tested. If a requirement is not testable, it is not a valid requirement.

While we are writing the requirements answering the “What” question, we need to also keep in mind the “Why” question. Why do we need this feature? Is it essential or is it a good to have? What is the impact of having this feature on the complexity and cost of the system? Answering these questions will help improve the efficiency of the project.

The answer to the last question - “How?” as usual starts with “It Depends!”

We have two main categories of specifications - Open and Closed.
1. An open specification describes required functionality and performances without mandating how those performances are to be achieved. It leaves a great deal of freedom to the developer that designs a system to satisfy the specifications. For example, a substation protection, automation and control system specification may not specify the communications architecture and the devices to be used in order to meet the requirements. It focuses on “What” and not on “How.”
2.  A closed specification is completely different. It describes not only required functions and performances, but also IEDs from specific vendor, communications architecture, communications protocols and other technologies that must be used in the design of the system to meet the specification.

It is important to take the time and develop a complete and detailed specification by involving all the users of the future system.
Once the users and developers are satisfied that the specification is clear and the requirements can be met with the available technology, it should be frozen and submitted for implementation.  

"Walking on water and developing software from a specification are easy if both are frozen."

Edward Berard

Power. Flexible. Easergy.
Protecting your electrical assets? today and tomorrow