LINE SECTIONALIZING USING A PLC AND ABB PROTECTIVE RELAY
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Figure 26. Read in Reply to Wattage Data Request and Store in PLC Registers
Figure 27. Read in Reply to Alarm Data Request and Store in PLC Registers
Segment 2 – Data Gathering from the PCD2000 and DPU2000R
The DPU2000R and the PCD2000 are both located some distance from the PLC. Attachment to these
relays is accomplished using simple SCATTER RADIO MODEMS. The radio modems are able to
communicate over a distance of 15 miles and retrieve information from them via a 10 bit protocol. The
SCATTER RADIO MODEMS have the advantage that no special licensing is required for connection to
the devices.
The ladder logic required for data retrieval is located in the ladder logic segment 2 and is based upon the
XMIT instruction which turns the PLC’s RS232 port into a MODBUS master. This enables the PLC to
query attached devices and poll for data. In this way the PLC is able to determine the loading of the
remote feeder and breaker status of the feeders being monitored and protected by the DPU2000R and
the PCD2000.
The PLC queries both the PCD and DPU via the command parameterization of the XMIT instruction. The
topology of the installation is illustrated in Figure 28 as follows in this discussion.
Содержание REL 356
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