Reading Phase Current Values - GE Multilin 850 Communications Manual

CHAPTER 12: ABOUT THE MODBUS MEMORY MAP

Reading Phase Current Values

Table 12-9: Modbus Map entries for Phase Currents
Modbus Hex Description
Address Address
31270 0x04F5 J1 Ia
31272 0x04F7 J1 Ib
31274 0x04F9 J1 Ic
8 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
When the voltage is present on the Trip Contact voltage monitor (Von), the Element Status
21 register will read: 0x2002 (8194). The masked value is then 0x0002, corresponding to
Von in the preceding table.
When the voltage is not present on the Trip Contact voltage monitor (Voff), the Element
Status 21 register will read: 0x2004 (8196). The masked value is then 0x0004,
corresponding to Voff in the preceding table.
Element Status 26 is used to monitor the Critical Fail contact.
When the relay is in service, the "IN SERVICE" LED on the front panel is green.
The Element Status 26 (Critical Fail) register reads: 0x2000 (8192). The masked value is then
0x0000, indicating Critical Fail Op is not present.
When the relay is not service, the "IN SERVICE" LED on the front panel is orange.
The Element Status 26 (Critical Fail) register reads: 0x2002 (8194). The masked value is then
0x0002, corresponding to Cristical Fail Op in the preceding table.
In this example a PLC is accessing the 6 sequential values beginning at Modbus address
31270 (Phase A current) in an 850 relay.
The following Modbus registers are assigned to Phase Currents:
• 31270 (0x04F5) J1 Ia - Phase A current
• 31272 (0x04F7) J1 Ib - Phase B current
• 31274 (0x04F9) J1 Ic - Phase C current
These Modbus Registers are listed in the Modbus memory map table as follows:
Min
0
0
0
In this case the format code used is F13, which is described in the Format Code table as
follows:
Table 12-10: Format Code entries for Phase Current
Code Type
F13 unsigned 32 bits
1st 16 bits
2nd 16 bits
The phase current metering values read by the PLC should match the values shown on the
relay. Validating the received values in the PLC against the real values observed on the 850
relay front panel or read via 8 Series EnerVista Setup is recommended.
PLCs can use two different word orders for reading 32-bit registers. As a result, a 32 bit
value of aabbccdd may be read as aabb ccdd, or as ccdd aabb.
A word-swap may be necessary to read the proper data from 850 relay current registers.
Once the correct word order is set, the obtained value needs to be divided by 1000 to get
the decimal point.
Register: 31270
Max Step Units Format
Code
0xFFFFFFFF 1 A F13
0xFFFFFFFF 1 A F13
0xFFFFFFFF 1 A F13
Definition
Unsigned Long Value, 3 Decimal Places
High Order Word of Long Value
Low Order Word of Long Value
Register: 312701
USING THE MEMORY MAP
Factory Size in 8 8 8
Default Words 5 6 8
0 9 9
0 2 Y Y Y Y
0 2 Y Y Y Y
0 2 Y Y Y Y
850 869 889 845
Y Y Y Y
Y Y Y Y
12-11
8
4
5