ABB Relion 670 Series Applications Manual page 246

Section 10
Unbalance protection
æ
3 C
=
ç
I
L1
è C
IECEQUATION19032 V1 EN-US
=
I I
p L 1
IECEQUATION19033 V1 EN-US
=
I I
p A
ANSIEQUATION19033 V1 EN-US
where a = 1 < 120°
æ
=
ç
V
ç
unit
è
IECEQUATION19034 V1 EN-US
=
I V
unit
IECEQUATION19035 V1 EN-US
% I
unit
IECEQUATION19036 V1 EN-US
Where,
V is the open-circuit voltage between N1 and N2
th
Z is the open-circuit impedance between N1 and N2
th
I is the unbalance current in Amperes
UNBL1
I is the phase L1 current in Amperes
L1A
I is the positive sequence component of phase L1A current in Ampere
P
V is the RMS value of phase L1 voltage in Volts
L1A
w is the radial frequency = 2 × π × f = 2 × π × 60
V is the RMS value of voltage across the faulty unit
unit
I is the RMS value of current flowing through the faulty unit
unit
%I is the percentage of current flowing through the faulty unit with respect to the rated
unit
current.
Based on the number of elements and units failure, the capacitance values of the faulty section
and neutral currents are shown in the following table:
240
´ ´ ö
C
+ ´ ´
L1l ÷
C V w
+ ´
L1
2 C ø
L1l
+ ´ + ´
2
I a I a
L 2 L 3
+ ´ + ´
2
I a I a
B C
ö
æ - ö
C C
- ´
÷
ç L1l ÷
1 V
÷
+ ´
L1
è ø
C 2 C ø
L1l
´ ´
w C
unit X
æ ö
I
= ´
ç unit ÷
100
è ø
I
unit Rated
© Copyright 2017 Hitachi Power Grids. All rights reserved
1MRK 511 401-UEN Rev. K
(Equation 114)
(Equation 115)
(Equation 115)
(Equation 116)
(Equation 117)
(Equation 118)
Bay control REC670
Application manual