GE 745 TRANSFORMER MANAGEMENT RELAY, Instruction Manual

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8-14 745 Transformer Management Relay GE Power Management
8.2 MODBUS PROTOCOL 8 COMMUNICATIONS
8
3. Setpoints may be written via the user map. In the example above, to change the value of Restrained Differ-
ential Pickup to 0.20 x CT through the user map, transmit the following Modbus message:
Field: Example (hex):
SLAVE ADDRESS 11 response message from slave 11
FUNCTION CODE 03 read register values
BYTE COUNT 0C 6 registers values = 12 bytes of data
DATA #1: high order byte 82 Relay Status
DATA #1: low order byte 01
DATA #2: high order byte 00 W3 Phase Time O/C Flag = not operated
DATA #2: low order byte 01
DATA #3: high order byte 00 W1 Phase A 4th Harmonic Content = 1%
ƒ
0
DATA #3: low order byte 01
DATA #4: high order byte 00 W1 Phase B 4th Harmonic Content = 1%
ƒ
0
DATA #4: low order byte 01
DATA #5: high order byte 00 W1 Phase C 4th Harmonic Content = 1%
ƒ
0
DATA #5: low order byte 01
DATA #6: high order byte 00 Percent Differential Pickup = 0.30
×
I
d
DATA #6: low order byte 1E
CRC: low order byte 80
CRC: high order byte F1
Master Query Message: Example (hex):
SLAVE ADDRESS 11 query message for slave 11
FUNCTION CODE 06 store single setpoint values
DATA STARTING ADDRESS: high order byte 01 data starting at address 0185
DATA STARTING ADDRESS: low order byte 85
DATA: high order byte 00 0014 = 0.30
×
I
d
DATA: low order byte 14
CRC: low order byte 9B
CRC: high order byte 40
Field: Example (hex):
SLAVE ADDRESS 11 response message from slave 11
FUNCTION CODE 06 store single setpoint values
DATA STARTING ADDRESS: high order byte 01 data starting at address 0185
DATA STARTING ADDRESS: low order byte 85
DATA: high order byte 00 0014 = 0.30
×
I
d
DATA: low order byte 14
CRC: low order byte 9B
CRC: high order byte 40