9.6 DISTURBANCE RECORD EXTRACTION
The IED provides facilities for both manual and automatic extraction of disturbance records.
Records extracted over MODBUS from Px40 devices are presented in COMTRADE format. This involves
extracting an ASCII text configuration file and then extracting a binary data file.
Each file is extracted by reading a series of data pages from the IED The data page is made up of 127
registers, giving a maximum transfer of 254 bytes per page.
The following set of registers is presented to the master station to support the extraction of uncompressed
disturbance records:
MODBUS registers
MODBUS Register Name Description
3x00001 Status register
Provides the status of the relay as bit flags:
b0: Out of service
b1: Minor self test failure
b2: Event
b3: Time synchronization
b4: Disturbance
b5: Fault
b6: Trip
b7: Alarm
b8 to b15: Unused
A ‘1’ on b4 indicates the presence of a disturbance
3x00800 No of stored disturbances
Indicates the total number of disturbance records currently stored in the
relay, both extracted and non-extracted.
3x00801
Unique identifier of the oldest
disturbance record
Indicates the unique identifier value for the oldest disturbance record stored
in the relay. This is an integer value used in conjunction with the ‘Number of
stored disturbances’ value to calculate a value for manually selecting
records.
4x00250
Manual disturbance record
selection register
This register is used to manually select disturbance records. The values
written to this cell are an offset of the unique identifier value for the oldest
record. The offset value, which ranges from 0 to the Number of stored
disturbances - 1, is added to the identifier of the oldest record to generate
the identifier of the required record.
4x00400
Record selection command
register
This register is used during the extraction process and has a number of
commands. These are:
b0: Select next event
b1: Accept event
b2: Select next disturbance record
b3: Accept disturbance record
b4: Select next page of disturbance data
b5: Select data file
3x00930 - 3x00933 Record time stamp These registers return the timestamp of the disturbance record.
3x00802 No of registers in data page
This register informs the master station of the number of registers in the
data page that are populated.
3x00803 - 3x00929 Data page registers
These 127 registers are used to transfer data from the relay to the master
station. They are 16-bit unsigned integers.
3x00934 Disturbance record status register
The disturbance record status register is used during the extraction process
to indicate to the master station when data is ready for extraction. See next
table.
4x00251 Data file format selection
This is used to select the required data file format. This is reserved for
future use.
MiCOM P747 Chapter 7 - SCADA Communications
P747-TM-EN-1 213
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