The relay uses a standard equation to set TAPn, based on settings entered for the particular winding (n denotes the winding number. ): The ratio TAPmax / TAPmin ≤ 7. 5Protection Settings Calculations for Power Transformers i. SEL-787 Transformer Differential Protection The relay (SEL-787) use the transformer MVA rating as a common reference point, TAP scaling converts all sec-ondary currents entering the relay from the two windings to per unit values, thus. This guide focuses primarily on application of protective relays for the protection of power transformers, with an emphasis on the most prevalent protection schemes and transformers. Setting procedures are only discussed in a general nature in the material to follow. Like Differential, IDMT, overcurrent, REF, Earth fault E/F, Over flux, Over/Under voltage protection relay setting. In this technical article, we will delve into the comprehensive methodology of calculating the differential relay settings for the GE P642 relay. By following these calculations meticulously, engineers. Modern relays often have algorithms that enhance the security of elements that are otherwise susceptible to current transformer (CT) saturation.
