Hitachi Relion 670 Series Applications Manual page 421

1MRK506375-UEN Rev. N
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
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
³
E E
al
EQUATION1077 V2 EN-US
where
I
kmax
22.1.6.6 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
below:
Railway application RER670
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
and S =0.150 VA/channel for I
R
the maximum required E
op
æ
I
= × ×
sr
I
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 secondary e.m.f. E
al
© 2017 - 2023 Hitachi Energy. All rights reserved
that is larger than or equal to the required rated
al
below:
alreq
ö
S
+ +
R
R
÷
ct L
2
I
ø
r
=5 A
r
is specified according to the following:
al
ö
S
+ +
R
R R
÷
ct L
2
I
ø
r
=0.020 VA/channel for I =1 A
R r
Section 22
Requirements
(Equation 82)
(Equation 83)
M11624-3 v6
alreq
415