operates after a predefined operate time and resets when the fault current
disappears. The IDMT mode provides current-dependent timer characteristics.
The function contains a blocking functionality. It is possible to block function
outputs, timers or the function itself, if desired.
4.4.1.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of the negative-sequence overcurrent protection can be described
using a module diagram. All the modules in the diagram are explained in the next
sections.
A070660 V1 EN
Figure 239: Functional module diagram. I
2
represents negative phase
sequence current.
Level detector
The measured negative-sequence current is compared to the set Start value. If the
measured value exceeds the set Start value, the level detector activates the timer
module. If the ENA_MULT input is active, the set Start value is multiplied by the
set Start value Mult.
The IED does not accept the Start value or Start value Mult setting
if the product of the settings exceeds the Start value setting range.
Timer
Once activated, the timer activates the START output. Depending on the value of
the Operating curve type setting, the time characteristics are according to DT or
IDMT. When the operation timer has reached the value of Operate delay time in
the DT mode or the maximum value defined by the inverse time curve, the
OPERATE output is activated.
When the user-programmable IDMT curve is selected, the operation time
characteristics are defined by the parameters Curve parameter A, Curve parameter
B, Curve parameter C, Curve parameter D and Curve parameter E.
1YHT530004D05 D Section 4
Protection functions
615 series 447
Technical Manual
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