Non-Directional Inverse Time Delayed Phase And Residual Overcurrent Protection - ABB REC670 Applications Manual

1MRK 511 401-UEN A
24.1.6.3
Bay control REC670 2.2 IEC
Application manual
Non-directional inverse time delayed phase and residual overcurrent
protection
The requirement according to Equation
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 limiting secondary e.m.f. E
than or equal to the required rated equivalent limiting secondary e.m.f. E
below:
³ = × ×
E E 20 I
al alreq op
EQUATION1076 V2 EN-US
where
I The primary current set value of the inverse time function (A)
op
I The rated primary CT current (A)
pr
I The rated secondary CT current (A)
sr
I The rated current of the protection IED (A)
r
R The secondary resistance of the CT (W)
ct
R
The resistance of the secondary cable and additional load (W). The loop
L
resistance containing the phase and neutral wires, must be used for faults in
solidly earthed systems. The resistance of a single secondary wire should be
used for faults in high impedance earthed systems.
S The burden of an IED current input channel (VA). S
R
A and S
Independent of the value of I
the following:
³ =
E E I
al alreq max k max
EQUATION1077 V2 EN-US
where
I Maximum primary fundamental frequency current for close-in faults (A)
kmax
130 and Equation
æ ö
I S
× + +
sr R
R R
ç ÷
ct L
2
I
I
è ø
pr r
=0.150 VA/channel for I =5 A
R r
the maximum required E
op
æ
I S
× × + +
sr R
R R
ç
ct L
2
I
I
è
pr r
Section 24
Requirements
131 does not need to be
that is larger
al
=0.020 VA/channel for I
R
is specified according to
al
ö
÷
ø
M11339-3 v5
alreq
(Equation 130)
=1
r
(Equation 131)
603