Distance Protection - ABB RELION 650 Series Applications Manual

Section 21
Requirements
where:
I
kmax
I
tmax
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
through fault current may pass two main CTs for the line differential protection without
passing the protected line. In such cases and if both main CTs have equal ratios and
magnetization characteristics the CTs must satisfy equation
³
E E
al
EQUATION1411 V2 EN-US
where:
I
tfdb
If a power transformer is included in the protected zone of the line differential protection the
CTs must also fulfill equation 165.
³
E E
al
EQUATION1412 V2 EN-US
where:
I
rt
21.1.6.2

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:
358
Maximum primary fundamental frequency fault current for internal close-in
faults (A)
Maximum primary fundamental frequency fault current for through fault
current for external faults (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
ç
alreq tfdb ct
I
è
pr
Maximum primary fundamental frequency through fault current that passes two main CTs (one-and-
a-half or double-breaker) without passing the protected line (A)
æ
I
= × × ×
sr
30 I R
ç
alreq rt ct
I
è
pr
The rated primary current of the power transformer (A)
=5 A
r
ö
S
+
R
R
÷
L
2
I
ø
r
ö
S
+ +
R
R
÷
L
2
I
ø
r
1MRK 505 363-UEN A
=0.020 VA/channel for
R
162 and equation 164.
(Equation 164)
(Equation 165)
that is
al
Application manual
M11619-3 v5
alreq