ABB REB670 Series Applications Manual page 167

1MRK 505 370-UEN D
IEC05000135 V5 EN-US
Figure 94: 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 (3U
•
Current (3I
•
• both currents and voltage,
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 (3U
polarizing or dual polarizing. Multiply the required set current (primary) with the minimum
impedance (ZNpol) and check that the percentage of the phase-to-earth voltage is definitely
higher than 1% (minimum 3U
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
(ZS -ZS
1
maximum earth-fault current at the local source can be used to calculate the value of ZN as
U/(√3 · 3I
primary ohms.
When the dual polarizing method is used, it is important that the setting
3I · ZNpol is not greater than 3U
0
reverse direction.
IPolMin : is the minimum earth-fault current accepted for directional evaluation. For smaller
currents than this value, the operation will be blocked. A typical setting is 5-10% of
UPolMin : Minimum polarization (reference) polarizing voltage for the directional function,
given in % of
Busbar protection REB670
Application manual
RCA
IN>Dir
or U )
0 2
· ZNpol or 3I ·ZNpol where ZNpol is RNpol + jXNpol), or
0 2
>
0
)/3, that is the earth return impedance of the source behind the protection. The
0
) Typically, the minimum ZNPol (3 · zero sequence source) is set. The setting is in
0
UBase /√3.
Upol = -3U
Operation
IEC05000135-5-en.vsdx
Dual (dual polarizing, (3U
) can be below 1% and it is then necessary to use current
0
UPolMin setting) as a verification.
. If so, there is a risk for incorrect operation for faults in the
0
or -3U
0 2
+ 3I · ZNpol) or (U + I
0 0 2
· ZNpol. The ZNpol can be defined as
0
INx> or the product
Section 7
Current protection
· ZNpol)).
2
IB .
161