I'm trying to learn protective relaying for power systems. More specifically, I want to learn how to calculate the settings that must be configured in the digital relays in order to build ANSI device functions, the ones described in IEEE Std C37.2-2008, such as ANSI-50, ANSI-51, ANSI-49, ANSI-87T and ANSI-21. I'm struggling to find formal references, especially references that are coherent with each other. Many book authors not only give different design rules, but they also use different vocabularies which is very confusing.

As someone who works in this field, how did you manage to gather the appropriate FORMAL knowledge (not just tips provided by some forum members) that is necessary for the design of protective relaying systems?

  • \$\begingroup\$ What is your end goal? Do you need to design a product that conforms to IEC saftey standards? \$\endgroup\$
    – Voltage Spike
    Commented Jul 24, 2023 at 16:02
  • \$\begingroup\$ My end goal is to be able to configure protective relays in order to build a protection system designed to protect a power system. \$\endgroup\$
    – A.Bukhari
    Commented Aug 1, 2023 at 19:26

1 Answer 1


I would recommend to choose one reference textbook to work your way through. Focus on the parts that you need to apply. There are also IEEE guides from the protective relaying committee that are practical and readable. Relay manufacturer documentation and application guides for the relays you would apply are also very helpful.

Besides reading, to really learn the craft of protective relaying, you should also have some technical mentors to talk design through with you and to review your work. Especially when you are starting out but in my opinion even as an experienced engineer, no consequential work (like relay settings) should be sent out without a peer review. Ideally this will be part of your organization's formal process. If not, take the initiative to seek it out.

If your organization has internal standards or templates to start from for relay settings, try to understand the reasons behind those standards or templates. Ideally these should be formally documented. If not, maybe you can be part of collecting the reasons for the settings from the people who came up with them and compiling it as written documentation, although this could be difficult to spearhead as a junior member of the team. At least you can ask some questions to try to understand the internal standards or templates. You have to understand the reasons behind a "standard" or "typical" setting in order to know when an exception to the standard might be called for.

The last thing I would mention for learning protective relaying is to review relay operations. After a trip or event, look at event reports from the relays to see what the fault looked like from their perspective. Find out what turned up in field investigation and compare it to what you inferred from looking at the relay records and what the textbook theory leads you to expect.


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