ABB RELION 650 SERIES, Applications Manual

Page: 249 / 262

16.1.6.3 Non-directional instantaneous and definitive time, phase and residual
overcurrent protection
M11622-3 v4
The CTs must have a rated equivalent secondary e.m.f. E
al
that is larger than or equal to the
required secondary e.m.f. E
alreq
below:
s n
R
a l a lre q CT L
2
pn n
op
I S
E E 1.5 I R R
I I
³ = × × + +
æ ö
×
ç ÷
è ø
EQUATION1678 V1 EN-US
(Equation 33)
where:
I
op
The primary operate value (A)
I
pn
The rated primary CT current (A)
I
sn
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
=0.010 VA/channel for I
r
=1 A and S
R
=0.250 VA/channel
for I
r
=5 A
16.1.6.4 Non-directional inverse time delayed phase and residual overcurrent
protection
M11339-3 v4
The requirement according to Equation 34 and Equation 35 does not need to be fulfilled if the high
set instantaneous or definitive time stage is used. In this case Equation is the only necessary
requirement.
If the inverse time delayed function is the only used overcurrent protection function the CTs must
have a rated equivalent secondary e.m.f. E
al
that is larger than or equal to the required secondary
e.m.f. E
alreq
below:
s n R
a l a lre q CT L
2
pn n
op
I S
E E 20 I R R
I I
³ = × × + +
æ ö
×
ç ÷
è ø
EQUATION1679 V1 EN-US
(Equation 34)
where
I
op
The primary current set value of the inverse time function (A)
I
pn
The rated primary CT current (A)
I
sn
The rated secondary CT current (A)
I
n
The nominal current of the protection IED (A)
Table continues on next page
1MRK 505 287-UUS B Section 16
Requirements
Busbar protection REB650 243
Application manual
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