ABB Relion 670 Series Applications Manual page 152

Section 8
Current protection
IEC05000135 V5 EN-US
Figure 68: 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 current and voltage,
Normally voltage polarizing from the internally calculated residual sum or an external open
delta is used.
Current polarization is useful when the local source is strong and a high sensitivity is required.
In such cases the polarizing voltage (3U
current polarization or dual polarization. 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
polarization. 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
146
RCA
IN>Dir
or U )
0 2
· ZNpol or 3I ·ZNpol where ZNpol is RNpol + jXNpol), or
0 2
Dual (dual polarizing, (3U
)/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.
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Upol = -3U
Operation
IEC05000135-5-en.vsdx
) can be below 1% and it is then necessary to use
0
UPolMin setting) as a verification.
>
0
. If so, there is a risk for incorrect operation for faults in the
0
1MRK 511 401-UEN Rev. K
or -3U
0 2
+ 3I · ZNpol) or (U + I
0 0 2
· ZNpol. The ZNpol can be defined as
0
INx> or the product
· ZNpol)).
2
IB .
Bay control REC670
Application manual