Section 21
Time inverse characteristics
21.1
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.
xx05000129.vsd
I>
I>
I>
IEC05000129 V1 EN
Figure 267:
Three overcurrent protections connected in series
en05000130.vsd
Time
Fault point
position
Stage 1
Stage 2
Stage 3
Stage 1
Stage 2
Stage 1
IEC05000130 V1 EN
Figure 268:
Definite time overcurrent characteristics
1MRK 504 135-UEN A
Section 21
Time inverse characteristics
625
Technical manual
Summary of Contents for ret650
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