Alstom MiCOM P846, Техническое руководство

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Firmware Design P846/EN FD/D
MiCOM P846
(FD) 9-15
FD
1.4.6.2 Event and fault recording
A change in any digital input signal or protection element output signal causes an event
record to be created. When this happens, the protection and control task sends a message
to the supervisor task to indicate that an event is available to be processed and writes the
event data to a fast buffer in SRAM which is controlled by the supervisor task. When the
supervisor task receives either an event or fault record message, it instructs the platform
software to create the appropriate log in battery backed-up SRAM. The operation of the
record logging to battery backed-up SRAM is slower than the supervisor’s buffer. This
means that the protection software is not delayed waiting for the records to be logged by the
platform software. However, in the rare case when a large number of records to be logged
are created in a short period of time, it is possible that some will be lost if the supervisor’s
buffer is full before the platform software is able to create a new log in battery backed-up
SRAM. If this occurs then an event is logged to indicate this loss of information.
1.4.6.3 Disturbance recorder
The disturbance recorder operates as a separate task from the protection and control task.
It can record the waveforms for up to 8 analog channels and the values of up to 32 digital
signals. The recording time is user selectable up to a maximum of 10 seconds. The
disturbance recorder is supplied with data by the protection and control task once per cycle.
The disturbance recorder collates the data that it receives into the required length
disturbance record. The disturbance records can be extracted by MiCOM S1 that can also
store the data in COMTRADE format, thus allowing the use of other packages to view the
recorded data.
1.4.6.4 Fault locator
The fault locator task is also separate from the protection and control task. The fault locator
is invoked by the protection and control task when a fault is detected. The fault locator uses
a 12-cycle buffer of the analog input signals and returns the calculated location of the fault to
the protection and control task which includes it in the fault record for the fault. When the
fault record is complete (i.e. includes the fault location), the protection and control task can
send a message to the supervisor task to log the fault record.
1.5 Fault locator
The relay has an integral fault locator that uses information from the current and voltage
inputs to provide a distance to fault location feature. The sampled data from the analog input
circuits is written to a cyclic buffer until a fault condition is detected. The data in the input
buffer is then held to allow the fault calculation to be made. When the fault calculation is
complete the fault location information is available in the relay fault record.
1.5.1 Basic theory for ground faults
A two-machine equivalent circuit of a faulted power system is shown in Figure 6.