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MR-REF & MR-REF3 Technical Manual
Issue 3, November 2013
4. Inputs and Outputs.
4.1. Power Supply Live.
The MR-REF & MR-REF3
requires a permanent AC or DC Voltage to supply the unit as specified by the relay rating
label. This auxiliary live is also used as the source voltage to power the digital inputs.
4.3. Current Transformer Inputs.
The MR-REF has provision to allow connection for one of standard protection class 1 amp or 5 amp secondary rated
current transformers with 1-2.5VA, or MR-REF-3 which allows for three standard protection class 1 amp or 5 amp
secondary rated current transformers with 1-2.5VA
4.4. Output Relays.
The MR-REF & MR-REF3 has 4 output relays which can be assigned depending upon the required function.
Each output relay is a changeover contact with Common (C) and Normally Open (NO) and Normally Closed (NC)
contacts.
4.5. Digital Inputs.
The MR-REF & MR-REF3 has 2 digital inputs which provide remote reset function and blocking input for the use
with protection functions.
The condition of all these inputs can be viewed at any time via the Display Scroll page of the relay, this enables
complete wire checking without the need to disconnect or even gain access to the rear panel wiring. The source
voltage for the digital inputs is derived from the auxiliary power supply, when power is connected, these terminals
may be live.
4.6. RS485 Rear Port.
The RS485 port utilises a half duplex RS485 protocol allowing up to 32 units to be daisy-chained together with a
single shielded twisted pair cable.
The host system can interrogate the unit to monitor status, running loads, historical data and fault data as well as
control functions such as reset of fault / alarm conditions. Setting parameters may also be changed or read.
The MR-REF & MR-REF3
is available with P&B network gold (P&B protocol) installed for use with the Xcell Data
Concentrator for fully Integrated Protection, Control & Monitoring Systems with full dual redundancy or with a Slave
implementation of Modbus RTU protocol for small systems and direct Modbus access to devices where data
concentration is not required.
4.7. RS232/USB Front Port.
The front mounted RS232/USB port allows access to historical and running data without disturbing the rear RS485
network. This port can be used for direct programming.
Summary of Contents for MR-REF
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