ABB Relion REC670, Applications Manual

Page: 178 / 658

V pol = 3V
0
or V
2
RCA
Operation
IDirPU
en 05000135-4- ansi.vsd
ANSI05000135 V3 EN-US
Figure 67: Relay characteristic angle given in degree
In a normal transmission network a normal value of RCA is about 65°. The setting
range is -180° to +180°.
polMethod : Defines if the directional polarization is from
• Voltage (3V
0
or V
2
)
• Current (3I
0
· ZNpol or 3I
2
·ZNpol where ZNpol is RNpol + jXNpol), or
• both currents and voltage, Dual (dual polarizing, (3V
0
+ 3I
0
· ZNpol) or (V
2
+ I
2
·
ZNpol)).
Normally voltage polarizing from the internally calculated residual sum or an external
open delta is used.
Current polarizing is useful when the local source is strong and a high sensitivity is
required. In such cases the polarizing voltage (3V
0
) can be below 1% and it is then
necessary to use current polarizing or dual polarizing. Multiply the required set current
(primary) with the minimum impedance (ZNpol) and check that the percentage of the
phase-to-ground voltage is definitely higher than 1% (minimum 3V
0
> VPolMin setting)
as a verification.
RNPol, XNPol : The zero-sequence source is set in primary ohms as base for the current
polarizing. The polarizing voltage is then achieved as 3I
0
· ZNpol. The ZNpol can be
defined as (ZS
1
-ZS
0
)/3, that is the ground return impedance of the source behind the
protection. The maximum ground-fault current at the local source can be used to
Section 8
1MRK 511 401-UUS A
Current protection
172 Bay control REC670 2.2 ANSI
Application manual