Important Considerations for Transformer Protective Relay Settings

Digital protective relays for power transformers have evolved significantly over the past decades, bringing both reliability and stability in protecting these very expensive and critical assets. Software technology associated with digital relays offers engineers and technicians a means to easily set and configure these devices, and aid in the testing process. Even though these tools exist, many field technicians still experience misoperation during the commissioning process due to setting errors. In this session, we will go behind the scenes of transformer protective relays to understand how the transformer nameplate can dictate the relay settings, and how the wrong interpretation can cause bad settings. Since most relay testing software helps to automate the testing process, not all transformer relays use the same technologies, so we will investigate as examples, the SEL-787 and Beckwith M-3311. We will also go behind the scenes of automated relay testing to understand how the testing process functions.