ANSI06000127_2_en.vsd
IED
with 1A
CT inputs
IB2
IX2
IA2
A B C N
IA1
IB1
IX1
LA
LB
LX
A-bus
Summation CTs
Main CTs
CT1
CT2 . . . CT24
A B C N
A B C N
52
52
52
ANSI06000127 V2 EN-US
Figure 83:
Principle CT connections for the complete station
This summation type bus differential protection still has the same main CT
requirements as outlined in section
"Rated equivalent secondary e.m.f. requirements"
Some of these are:
•
main CT ratio differences can be tolerated up to 10:1 (for example, 3000/5A CT
can be balanced against CT"s as low as 300/5)
•
different main CT ratios are compensated numerically by a parameter setting
•
main CT shall not saturate quicker than 2 ms ( refer to section
secondary e.m.f. requirements"
for detailed CT requirements regarding main CT
knee-point voltage)
However, due to the summation principle this type of busbar protection scheme has the
following limitations:
1MRK 505 370-UUS A
Section 6
Differential protection
Busbar protection REB670 2.2 ANSI
165
Application manual
Summary of Contents for RELION REB670
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