Chapter 1) 7SR242 Duobias Description Of Operation
©2015 Siemens Protection Devices Limited
Chapter 1 Page 23 of 60
Section 3: Protection Functions
3.1 Current Protection: Differential Protection
Comprises both biased differential and high-set differential elements.
The fundamental frequency current is measured with the line CT inputs. These line currents are both multiplied
and vector corrected before being applied to the current differential elements.
3.1.1 ICT
The
Wn ICT Multiplier
setting is applied to the line currents – the CT secondary currents. The multiplier is used
to correct any CT ratio mismatch so that ideally nominal current (ICT
OUT
= 1A) is applied to the biased differential
algorithm.
The
Wn ICT Connection
setting applies the correct vector compensation to the current applied to the differential
algorithm.
The nominal current ratio of the virtual interposing CT is 1:1. Note that where Yd settings are applied some
current distributions will result in a 3 multiplying factor being applied. See ‘Applications Guide’.
Summary of Contents for 7SR242 Duobias
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