INTRODUCTION

The performance of a microprocessor-based relay is highly dependent

on the performance of the analog channels measurement of the relay,

as protection functions operate on these values.

The failure of an analog measurement channel, 

either due to a failure in the external measurement circuit,

or due to an internal failure inside a UR CT/VT module, 

can cause incorrect operation of protection functions.

The UR CT/VT modules with Enhanced Diagnostics (module types 8L, 8M, 8N, 8R, 8S, 8V)

can detect the failure of an analog channel measurement due to internal

failures of the CT/VT module, alarm for failure of the module,

and block tripping from any protection function associated with this module.

This feature is available when using firmware 5.20 or later within

the UR family and therefore field-proven since 2006.