D-700 MK3 User Manual Firmware V-16.8
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The D-700 includes a comprehensive set of protection functions to detect quickly a mains failure during
parallel with mains operation.
The protections are enabled after the timeout defined by the parameter Parallel Check Delay in order not
to detect a mains failure during transients caused by the closing of the contactors.
If any of the protection functions detects a mains failure during parallel with mains:
-the mains contactor is immediately de-energized,
-a Parallel Mains Fail warning is generated,
-a specific warning to the related protection function is generated.
The ROCOF measures the frequency of the mains for each period. If the frequency change exceeds the
predefined limit for 4 successive periods, then the ROCOF function detects a mains failure. Thus the
response time of the ROCOF is approximately 4 cycles.
However the ROCOF will not detect relatively slow changes in mains frequency.
Related parameter: ROCOF df/dt
If the parameter is set to zero, then the protection function will be disabled.
The Vector Shift measures and stores the period of last 5 cycles. At the end of each cycle it compares the
average period of last 2 cycles with the average period of 4
th
and 5
th
cycles. If the difference exceeds the
predefined limit, then the vector shift detects a mains failure. Thus the response time of the vector shift is
5 cycles.
However the vector shift will not detect relatively slow changes in mains frequency.
Related parameter: Vector Shift Limit
If the parameter is set to zero, then the protection function will be disabled.
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