impedance grounded system, the voltage drop is big and the setting can typically be set to
70% of base voltage (VBase)
PU27PP: The setting of the phase-to-phase voltage level (line voltage) which is used by
the evaluation logic to verify that a fault exists in two or more phases. The voltage must
be set to avoid that a partly healthy phase-to-phase voltage, for example, B-C for a A-B
fault, picks-up and gives an incorrect release of all loops. The setting can typically be 40
to 50% of rated voltage (VBase) divided by √3, that is 40%.
3V0PU: The setting of the residual voltage level (neutral voltage) which is used by the
evaluation logic to verify that an ground-fault exists. The setting can typically be 20% of
base voltage (VBase).
Pickup_N: The setting of the residual current level (neutral current) which is used by the
evaluation logic to verify that a cross-country fault exists. The setting can typically be
20% of base current (IBase) but the setting shall be above the maximum current generated
by the system grounding. Note that the systems are high impedance grounded which
means that the ground-fault currents at ground-faults are limited and the occurring IN
above this level shows that there exists a two-phase fault on this line and a parallel line
where the IN is the fault current level in the faulty phase. A high sensitivity need not to be
achieved as the two-phase fault level normally is well above base current.
tIN: The time delay for detecting that the fault is cross-country. Normal time setting is 0.1
- 0.15 s.
tVN: The time delay for a secure VN detecting that the fault is an ground-fault or double
ground-fault with residual voltage. Normal time setting is 0.1 - 0.15 s.
tOffVN: The VN voltage has a reset drop-off to ensure correct function without timing
problems. Normal time setting is 0.1 s
8.20 Phase preference logic PPL2PHIZ
8.20.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Phase preference logic PPL2PHIZ - -
8.20.2 Application
The Phase preference logic function PPL2PHIZ provides a supplementary phase selection
to the High speed distance protection ZMFPDIS (21). The application is for resonance
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 481
Application manual
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