ZIV 7IRD-A, Инструкция по эксплуатации

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Chapter 6. Description of Operation of Protection Subsystem
6-11
M7IRDA2003I
7IRD-A/J/M: Distribution Protection & Control Terminal
© ZIV APLICACIONES Y TECNOLOGÍA, S.L.U. 2020
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With Minimum Load in the Line Setting
Some models have a special setting for Minimum Load in the Line, which is the level of direct
sequence current needed for enabling unit operation. The logic of this unit is shown on the
following figure.
Figure 6.8 Open Phase Element Block Diagram (with Minimum Load in the Line Setting).
6.4 Residual Current Element
The Residual Ground Overcurrent element is designed to detect situations of sustained residual
or unbalance currents by the existence of zero sequence currents which are below expected
ground fault values.
Figure 6.9 Residual Current Unit Detection Block Diagram.
The current measured by the Residual Current Unit Detection uses the same Current Analog
Input as the Ground Overcurrent elements. Once this element has picked up, output
A_RESIDUAL is activated. If the A_RESIDUAL signal is present for a period of time equal to or
greater than the Time Delay setting, a Trip Output occurs ( S_RESIDUAL ). The Residual
Current Unit Detection can be disabled with the element Enable setting but is automatically
disabled when the Ground Time Overcurrent element picks up.