Section 21 Time Inverse Characteristics; Application - ABB RET650 Technical Manual

1MRK 504 135-UEN A
Section 21
21.1
Technical manual
Time inverse characteristics

Application

In order to assure time selectivity between different overcurrent protections in
different points in the network different time delays for the different relays are
normally used. The simplest way to do this is to use definite time delay. In more
sophisticated applications current dependent time characteristics are used. Both
alternatives are shown in a simple application with three overcurrent protections
connected in series.
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Figure 267: Three overcurrent protections connected in series
Time
Stage 1
IEC05000130 V1 EN
Figure 268: Definite time overcurrent characteristics
Time inverse characteristics
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Section 21
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Stage 2
Stage 1
Fault point
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