The 140 NOP 850 00 module supports the Quantum Hot Standby function. In a Quantum Hot Standby system, the primary and standby PLCs continuously exchange data – including the state RAM – of the two 140 NOP 850 00 modules. This data is located in located (%MW) memory.
NOTE: When you configure the Hot Standby function of the Quantum CPU (in the Configuration → Hot Standby tab)), confirm that the State RAM → Non-Transfer Area does not include the %MW location of 140 NOP 850 00 module data.
IEC61850 Server Functions in a Quantum Hot Standby System
SCADA:
In a Quantum Hot Standby system, the primary PLC performs SCADA functions in the same manner as a standalone PLC. The standby PLC does not communicate with SCADA, but does monitor PLC memory each scan and generates reports.
On switchover, the primary PLC closes the connection with SCADA; the standby PLC starts to listen for and accept new connection requests from SCADA. The former standby PLC – now the primary – first applies the data values received from the former primary to its local database, and then begins to perform SCADA functions after a SCADA connection is established.
Report Functions:
On every PLC cycle, the two 140 NOP 850 00 modules synchronize the buffered report Entry ID value. After switchover, SCADA needs to explicitly set the Entry ID to the 140 NOP 850 00 module in the new primary PLC so that the module can continue to send buffered reports.
The Integrity Period setting is disabled for buffered and unbuffered reports in a Hot Standby system, because the 140 NOP 850 00 module in the standby PLC cannot generate periodic reports.
GOOSE:
Only the 140 NOP 850 00 module in the primary PLC can publish GOOSE transmissions.
The 140 NOP 850 00 modules in both the primary and standby PLCs receive GOOSE data from the remote IED. However, the data received by the standby PLC is not added to memory, but is only added to the local database.
On switchover, the 140 NOP 850 00 module in the standby PLC takes over the task of sending GOOSE. However, the stNum and sqNum fields are not synchronized.
IEC61850 Client Functions in a Quantum Hot Standby System
Connection with Remote IED:
Only the 140 NOP 850 00 module in the primary PLC communicates with the remote IED; the 140 NOP 850 00 module in the standby PLC does not establish a connection with remote IED.
The 140 NOP 850 00 modules in both the primary and standby PLCs synchronize data out values from PLC memory to the local database. However, because the standby PLC doesn't send output data to the remote IED, the remote IED receives output data only from the 140 NOP 850 00 module in the primary PLC.
GOOSE:
The 140 NOP 850 00 modules in both the primary and standby PLCs receive GOOSE data from the remote IED. However, the data received by the standby PLC is not added to memory, but is only added to the local database.
Report Functions:
It is recommended to automatically enable the report function for buffered and unbuffered report control blocks by setting the AutoEna field to 1 (auto enable). After switchover, the 140 NOP 850 00 module sets the Entry ID to the remote IED and automatically enables the report when establishing a connection with the remote IED.
Switchover:
On switchover, the 140 NOP 850 00 module in the primary PLC closes the connection with remote IED; the 140 NOP 850 00 module in the former standby – now the primary – PLC begins to communicate with remote IED.
If the execution of a report control block/GOOSE command, polling command, or control operation is interrupted by a switchover, the high byte of the Status element for that object returns a detected error bit. It is recommended to add an error handling procedure to your program logic that will manage this detected error by re-sending the command.
140 NOP 850 00 IP Address Recovery Time
Use the following formula to determine the 140 NOP 850 00 module IP address recovery time in a Quantum Hot Standby system:
500 ms (IP address swapping) + connection establishment time (3 s)
NOTE: The maximum swap time may increase if the end device does not respond in a timely manner.
NOTE: During the swap, there may be disruption in communication between the 140 NOP 850 00 module and the end device. Confirm that the application can tolerate this communication disruption.
