Section 25 Inverse Time Characteristics - ABB REG670 Technical Manual

1MRK502052-UEN B
Section 25
25.1
Technical manual
Inverse time characteristics
Application
In order to assure time selectivity between different overcurrent protections at
different points in the network different time delays for the different protections are
normally used. The simplest way to do this is to use definite time-lag. In more
sophisticated applications current dependent time characteristics are used. Both
alternatives are shown in a simple application with three overcurrent protections
operating in series.
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IEC05000129 V1 EN
Figure 574: Three overcurrent protections operating in series
Time
Stage 1
IEC05000130 V1 EN
Figure 575: Definite time overcurrent characteristics
Inverse time characteristics
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Stage 2
Stage 1
Section 25
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Stage 3
Stage 2
Stage 1
Fault point
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