Distance Protection - ABB RELION 670 Series Applications Manual

Section 23
Requirements
where:
I
rt
I
tf
I
pr
I
sr
I
r
R
ct
R
L
S
R
In substations with breaker-and-a-half or double-busbar double-breaker arrangement, the
fault current may pass two main CTs for the transformer differential protection without
passing the power transformer. In such cases and if both main CTs have equal ratios and
magnetization characteristics the CTs must satisfy equation
³
E E
al
EQUATION1414 V2 EN-US
where:
I
f
23.1.6.2

Distance protection

The current transformers must have a rated equivalent limiting secondary e.m.f. E
larger than the maximum of the required rated equivalent limiting secondary e.m.f. E
below:
³
E E
al
EQUATION1080 V2 EN-US
³
E E
al
EQUATION1081 V2 EN-US
720
The rated primary current of the power transformer (A)
Maximum primary fundamental frequency current that passes two main
CTs and the power transformer (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 wire 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
æ
I
= × × +
sr
I R R
ç
alreq f ct
I
è
pr
Maximum primary fundamental frequency current that passes two main CTs without passing the
power transformer (A)
æ
I I
= × × ×
k max sr
a R
ç
alreq
I
è
pr
æ
I I
= × × ×
kzone1 sr
k R
ç
alreq
I
è
pr
=5 A
r
ö
S
+
R
÷
L
2
I
ø
r
ö
S
+ +
R
R
÷
ct L
2
I
ø
r
ö
S
+ +
R
R
÷
ct L
2
I
ø
r
1MRK 504 152-UEN B
=0.020 VA/channel for
R
529 and equation 531.
(Equation 531)
that is
al
(Equation 532)
(Equation 533)
Application manual
M11619-3 v5
alreq