Woodward highprotec MRI4, User Manual

Page: 190 / 727

Communication Protocols
Modbus
®
Modbus
Modbus
®
Protocol Configuration
The time-controlled Modbus
®
protocol is based on the Master-Slave working principle. This means that the
substation control and protection system sends an enquiry or instruction to a certain device (slave address) which
will then be answered or carried out accordingly. If the enquiry/instruction cannot be answered/carried out (e.g.
because of an invalid slave address), a failure message is returned to the master.
The Master (substation control and protection system) can query information from the device, such as:
Type of unit version
Measuring values/Statistical measured values
Switch operating position
State of device
Time and date
State of the device’s digital inputs
Protection-/State alarms
The Master (control system) can give commands/instructions to the device, such as:
Control of switchgear (where applicable, i.e. each acc. to the applied device version)
Change-over of parameter set
Reset and acknowledgement of alarms/signals
Adjustment of date and time
Control of alarm relays
For detailed information on data point lists and error handling, please refer to the Modbus
®
documentation.
To allow configuration of the devices for Modbus
®
connection, some default values of the control system must be
available.
190 MRI4 DOK-HB-MRI4-2E