The MOM + MCD bits available on the Modbus interface in the protection relay detect the fast indication data transitions. It is possible to receive also SPA events from the protection relay interface. The SPA events are derived from user enabled Modbus events.
Every Modbus indication data can separately be enabled to produce a time tagged event on either both its transitions (ON-OFF) or only on the activating transition (ON). If this is done, then the Modbus events are automatically converted to SPA events for the SPA interface. The Modbus/SPA events need not to be enabled for the MOM + MCD operations to work. The Modbus/SPA event generation can be optimized to include only the required events.