Directional Phase And Residual Overcurrent Protection - ABB Relion REC670 Applications Manual

1MRK 511 358-UEN A
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
required rated equivalent limiting secondary e.m.f. E
³
E E
al
EQUATION1076 V2 EN-US
where
I
op
I
pr
I
sr
I
r
R
ct
R
L
S
R
Independent of the value of I
following:
³
E E
al
EQUATION1077 V2 EN-US
where
I
kmax
22.1.6.4

Directional phase and residual overcurrent protection

If the directional overcurrent function is used the CTs must have a rated equivalent limiting
secondary e.m.f. E
secondary e.m.f. E
Application manual
æ
I
= × × ×
sr
20 I R
ç
alreq op
I
è
pr
The primary current set value of the inverse time function (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The rated current of the protection IED (A)
The secondary resistance of the CT (W)
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 earthed systems. The resistance of a single secondary wire should
be used for faults in high impedance earthed systems.
The burden of an IED current input channel (VA). S
I =1 A and S =0.150 VA/channel for I
r R
the maximum required E
op
æ
I
= × ×
sr
I R
ç
alreq max k max
I
è
pr
Maximum primary fundamental frequency current for close-in faults (A)
that is larger than or equal to the required rated equivalent limiting
al
below:
alreq
alreq
ö
S
+ +
R
R
÷
ct L
2
I
ø
r
=5 A
r
ö
S
+ +
R
R
÷
ct L
2
I
ø
r
that is larger than or equal to the
al
below:
=0.020 VA/channel for
R
is specified according to the
al
Section 22
Requirements
(Equation 133)
(Equation 134)
M11624-3 v6
461