Section 21 Time Inverse Characteristics - ABB Relion Technical Manual

1MRK 502 048-UUS 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.
IPickup
ANSI05000129 V1 EN
Figure 315: Three overcurrent protections connected in series
Time
Stage 1
IEC05000130 V1 EN
Figure 316: Definite time overcurrent characteristics
Time inverse characteristics
IPickup
Stage 2
Stage 1
Section 21
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Stage 2
Stage 1
Fault point
position
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