Instantaneous Phase Overcurrent Protection Phpioc (50) - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
Section 9
9.1
9.1.1
9.1.2
Line distance protection REL670 2.2 ANSI
Application manual
Current protection
Instantaneous phase overcurrent protection PHPIOC
(50)
Identification
Function description
Instantaneous phase overcurrent
protection
Application
Long transmission lines often transfer great quantities of electric power from generation
to consumption areas. The unbalance of the produced and consumed electric power at
each end of the transmission line is very large. This means that a fault on the line can easily
endanger the stability of a complete system.
The transient stability of a power system depends mostly on three parameters (at constant
amount of transmitted electric power):
• The type of the fault. Three-phase faults are the most dangerous, because no power
can be transmitted through the fault point during fault conditions.
• The magnitude of the fault current. A high fault current indicates that the decrease of
transmitted power is high.
• The total fault clearing time. The phase angles between the EMFs of the generators
on both sides of the transmission line increase over the permitted stability limits if the
total fault clearing time, which consists of the protection operating time and the
breaker opening time, is too long.
The fault current on long transmission lines depends mostly on the fault position and
decreases with the distance from the generation point. For this reason the protection must
IEC 61850 IEC 60617
identification identification
PHPIOC
3I>>
SYMBOL-Z V1 EN
Section 9
Current protection
ANSI/IEEE C37.2
device number
50
487