A protection relay trips on the same fault current reading every time. Most engineers read that as trustworthy. It shouldn’t be, not on its own. A sensor can be repeatable and wrong at once, and a biased one doesn’t announce itself.

Inverter-based resources and data centers are adding high-frequency disturbances to the grid, and a biased sensor can miss them or report them incorrectly with total confidence. Averaging more readings never cancels the error.

So how do you know a sensor is correct? Accuracy has to be checked against something outside the device. G&W Electric tests its Accusense™ sensors that way, with temperature and humidity cycling that simulates more than 20 years in the field. They are built to operate without correction factors or field calibration.