I
sr
The rated secondary CT current (A)
I
r
The rated current of the protection IED (A)
R
ct
The secondary resistance of the CT (Ω)
R
L
The resistance of the secondary wire and additional load (Ω). The loop resistance
containing the phase and neutral wires shall be used.
S
R
The burden of a REx670 current input channel (VA). S
R
=0.020 VA / channel for IR =
1 A and S
R
= 0.150 VA / channel for IR = 5 A
In substations with breaker-and-a-half or double-busbar double-breaker
arrangement, the fault current may pass two main phase CTs for the restricted earth
fault protection without passing the power transformer. In such cases and if both
main CTs have equal ratios and magnetization characteristics the CTs must satisfy
Requirement
and the Requirement
:
2
sr
R
al
alreq
ef
ct
L
pr
r
I
S
E
E
I
R
R
I
I
æ
ö
³
=
×
×
+
+
ç
÷
è
ø
EQUATION2239 V2 EN-US
(Equation 88)
Where:
I
ef
Maximum primary fundamental frequency phase-to-earth fault current that passes two
main CTs without passing the power transformer neutral (A)
Neutral CTs and phase CTs for impedance earthed transformers
GUID-FA79C943-A19B-47E2-BFC5-C9D01347302A v3
The neutral CT and phase CTs must have a rated equivalent limiting secondary
e.m.f. E
al
that is larger than or equal to the required rated equivalent limiting
secondary e.m.f. E
alreq
below:
2
3
sr
R
al
alreq
etf
ct
L
pr
r
I
S
E
E
I
R
R
I
I
æ
ö
³
= ×
×
×
+
+
ç
÷
è
ø
EQUATION2240 V2 EN-US
(Equation 89)
Where:
I
etf
Maximum primary fundamental frequency phase-to-earth fault current that
passes the CTs and the power transformer neutral (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
r
The rated current of the protection IED (A)
R
ct
The secondary resistance of the CT (Ω)
R
L
The resistance of the secondary wire and additional load (Ω). The loop
resistance containing the phase and neutral wires shall be used.
S
R
The burden of a REx670 current input channel (VA). S
R
= 0.020 VA / channel for
I
r
= 1 A and S
R
= 0.150 VA / channel for I
r
= 5 A
1MRK 506 375-UEN A
Section 22
Requirements
Railway application RER670 2.2 IEC
481
Application manual
Содержание RELION RER670
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