For context, when power grid engineers talk about relays, they're not talking about physical switching of the electricity itself, but instead the control and monitoring system for the grid. Traditionally this was done using specialised electomechanical devices (like the common electronic relay, but with special functions/construction).

The relays control actual power flow on the grid indirectly, using devices like breakers, tap changers, etc.

This article is talking about the digitalisation of relays, which basically means microprocessors or adapting industrial PLCs to do the same basic functions as the electromechanical relays but better (smaller, less maintenance, advanced features like fault localisation, remote control, etc.).

Interestingly, some power grids have resisted digitalisation out of concern that new electronics will have unknown fault characteristics that could lead to blackouts. Take this in contrast to railway signalling, which has if anything a more severe fault condition (would you rather be in a train crash or a blackout!) yet digital signalling was enthusiastically adopted by almost all systems.

The relay itself is digital rather than electro-mechanical. (I went to WSU and, like many Cougs, interned at SEL.)

It's sensors and a control system. The article is a bit misleading.