Protective Relay Coordination Study at a Petrochemical Complex

As part of a substation upgrade project, a relay coordination study was performed to determine the settings for the new microprocessor-based protective relays in accordance with the latest international standards. The project included old electromechanical relays that were changed out with new microprocessor-based protective relays.This paper will include the relay coordination study that involved a systematic approach. The steps included the transfer of the old electromechanical relay settings into the new replacement relays, and the development of temporary settings to be able to put the switchgear back in service. The final step included the continuation of the relay coordination study after the plant shutdown.The paper will also include international and plant standards and assumptions for collecting the field data in order to build the software model. The available maximum and minimum short circuit current had to be defined. The coordination study generated time current curves that were reviewed in accordance with the agreed upon international and plant standards. When the review was completed, the relay settings were put in a setting table that was used in the uploading of the new settings into the microprocessor-based protective relays already in service. The chosen field implementation techniques will also be discussed.The paper will also include a discussion of the steps essential to make the completion of the study a success.