Sequence number
Every fault record is given a sequence number. The sequence number runs from 1 to 65535 and then rolls over to one again. The client can check that the sequence numbers of the recorded data are sequential. During the fault record buffer overflow the client can notice a jump in the sequence numbers when some fault records are lost. The gap between the new and the previous sequence number reveals exactly how many records have been lost.
Unread records Left
This register shows how many unread fault records still remain unread for the client in question at a particular moment.
Time stamp registers
The time stamp registers usually hold two data values in the high and low byte of the registers: High byte value = RegisterValue DIV 256, Low byte value = RegisterValue MOD 256. An exception is the milliseconds register which contains the milliseconds 0...999 coded as such. Time stamp also contains a time quality register.
Time quality
|
Bit |
Meaning |
Values |
|
|---|---|---|---|
|
15 |
Event time stamp format |
0 = Local time |
1 = UTC time |
|
14 |
Time stamp source |
0 = Internal application |
1 = Modbus stack |
|
13 |
Clock not synchronized |
0 = Synchronized |
1 = Time not synchronized |
|
12 |
Clock failure |
0 = Clock OK |
1 = Clock failure |
|
11...0 |
Reserved |
0 |
|
Event time stamp format bit 15
The time stamp format can be selected with a Modbus parameter via the HMI or Parameter Setting.
Event time stamp source bit 14
The time stamp can be generated by the protection relay application, that is accurate time, or by Modbus. If generated by Modbus, the change values are detected by the Modbus background scan task. Since there is a latency time between the value change and the time when Modbus detects the change, in this case the time stamp is not accurate.
Clock not synchronized bit 13
The quality information bit is set in the protection relay's real-time clock if the protection relay has not been synchronized.
Clock failure bit 12
The quality information bit is set in the protection relay's real-time clock if the clock has a severe failure. Do not rely on this time stamp.