ABB rec670 Applications Manual

24.1.6.1 Breaker failure protection
M11621-3 v5
The CTs must have a rated equivalent limiting secondary e.m.f. E
al
that is lar
ger than
or equal to the required rated equivalent limiting secondary e.m.f. E
alreq
below:
sn
R
al alreq CT L
2
pn n
op
I
S
E E 5 I R R
I I
³ = × × + +
æ ö
×
ç ÷
è ø
EQUATION1677 V1 EN-US (Equation 128)
where:
I
op
The primary operate value (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
n
The nominal current of the protection IED (A)
R
ct
The secondary resistance of the CT (W)
R
L
The resistance of the secondary cable and additional load (W). The loop resistance containing the
phase and neutral wires, must be used for faults in solidly
grounded
systems. The resistance of a
single secondary wire should be used for faults in high impedance grounded systems.
S
R
The burden of an IED current input channel (VA). S
R
=0.020
VA/channel for I
r
=1 A and S
R
=0.150
VA/channel for I
r
=5 A
24.1.6.2 Non-directional instantaneous and definitive time, phase and residual
overcurrent protection
M11622-3 v5
The CTs must have a rated equivalent limiting secondary e.m.f. E
al
that is lar
ger than
or equal to the required rated equivalent limiting secondary e.m.f. E
alreq
below:
Section 24 1MRK 511 401-UUS A
Requirements
632 Bay control REC670 2.2 ANSI
Application manual

ABB rec670 Specifications

General

Brand	ABB
Model	rec670
Category	Control Unit
Language	English