Double-command controls are performed towards DPC (controllable double point) IEC 61850 target objects, that is, circuit breakers and controllable disconnector objects. The command can be given with or without a time stamp (C_DC_NA_1, C_DC_TA_1).
If time-tagged commands are used, it is important to ensure the master and the relay times are synchronized. Also, time zone related settings need to be correct, such as the Time zone (UTC or local) setting and local time offset in general time settings if local time is used. The maximum accepted delay between the command time stamp and the relay time can be adjusted by the Command delay setting.
Each double-point DPC object has two predefined IEC 60870-5-104 control objects: one intended for direct operation and the other one for select-execute (select-before-operate) operation. The difference can be seen in the control object’s signal name trailing text.
…DPC-ctlVal-Direct
…DPC-ctlVal-SBO