12.9.5 Operation principleDisturbance recording is based on the acquisition of binary and analog signals. Thebinary signals can be either true binary input signals or internal logical signalsgenerated by the functions in the IED. The analog signals to be recorded are inputchannels from the Transformer Input Module (TRM) through the Signal MatrixAnalog Input (SMAI) and possible summation (Sum3Ph) function blocks and someinternally derived analog signals.Disturbance recorder collects analog values and binary signals continuously, in acyclic buffer. The pre-fault buffer operates according to the FIFO principle; old datawill continuously be overwritten as new data arrives when the buffer is full. The sizeof this buffer is determined by the set pre-fault recording time.Upon detection of a fault condition (triggering), the disturbance is time tagged and thedata storage continues in a post-fault buffer. The storage process continues as long asthe fault condition prevails - plus a certain additional time. This is called the post-faulttime and it can be set in the disturbance report.The above mentioned two parts form a disturbance recording. The whole memory,intended for disturbance recordings, acts as a cyclic buffer and when it is full, theoldest recording is overwritten. Up to the last 100 recordings are stored in the IED.The time tagging refers to the activation of the trigger that starts the disturbancerecording. A recording can be trigged by, manual start, binary input and/or fromanalog inputs (over-/underlevel trig).A user-defined name for each of the signals can be set. These names are common forall functions within the disturbance report functionality.12.9.5.1 Memory and storageThe maximum number of recordings depend on each recordings totalrecording time. Long recording time will reduce the number ofrecordings to less than 100.The IED flash disk should NOT be used to store any user files. Thismight cause disturbance recordings to be deleted due to lack of diskspace.When a recording is completed, a post recording processing occurs.This post-recording processing comprises:• Saving the data for analog channels with corresponding data for binary signals• Add relevant data to be used by the Disturbance handling tool (part of PCM 600)• Compression of the data, which is performed without losing any data accuracy• Storing the compressed data in a non-volatile memory (flash memory)Section 12 1MRK 511 287-UEN AMonitoring462Technical manual
