A fault record is created by the protection relay as a set of registrations during a detected fault period. The registration includes the selected peak values and the global duration value of the protection stages, the time of recording and a sequence number for the fault record.
The size of the protection relay's internal Modbus fault record buffer is 100 records. The 100 latest fault records are at any time readable from the protection relay. The Modbus fault record is Modbus dependent and the data organization and buffer size differ from the protection relay's initial system level registrations. When the Modbus fault record buffer becomes full, the protection relay overwrites the oldest records in the buffer.
Multiple clients support
Several Modbus clients can independently of one another read out the Modbus fault records from the protection relay. The Modbus fault record buffer keeps track of where in the buffer the different clients are reading at the moment. Clients are identified either by the serial port from where the requests are issued or by the client's IP address in the TCP/IP network.