File Mechanism

Overview

The MicroLogic trip unit stores events and waveform in different files.

Access

These files can be read with the Modbus function code 20 (0x14): Read file record.

There are two types of files:

ofiles with dynamic number of records added in a FIFO stack and managed with sequence registers. In this case, the record number of the last record is defined with these sequence registers.

ofiles with a fixed number n of records. In this case, all record numbers and their descriptions are detailed. The Modbus function 20 (0x14) is handled n times on the n desired records numbers.

Structure

The following graphic shows the structure of a file:

 

 

A file is made up of records, with a maximum of 100 records. All records in a file have the same structure and size.

The descriptor is made up of the following two read zones:

oone read zone for file configuration (Header) that gives information about the size of file and records

oone read zone for file characteristics (Status) that gives information about record numbers

Descriptors are updated each time new record is added to the file.

Sequence Registers Description

The file characteristics (Status) make available to the supervisor two sequence registers that indicate the first and last records added in the file. They enable the supervisor to determine whether certain records were deleted before they could be read.

The sequence number for the last record increments from 1 to 8000 each time a new record is added to the file.

When the file is full (maximum of 100 records), the new record overwrites the oldest record. The sequence number for the last record continues to increment normally. When the oldest record is overwritten, the sequence number for the first record also increments.

When the sequence number reaches 8000, the next sequence number will be 1.

Read File Record Example

The Read File Record function is used to access in a standardized manner the file information. This example presents a request to read the most recent record in the event log of the protection manager.

The following table shows how to read the event log of the file number 20 (0x0014). This file is made up of 100 records. Each record is made up of 9 registers, thus the record length is 9 (0x0009). The Modbus address of the Modbus slave is 47 = 0x2F.

The sequence number of last record in the file (the most recent) is the content of register 9921. Consider 0x1234 for the content of register 9921.