Instantaneous Phase Overcurrent Protection Phpioc (50) - ABB REC670 Applications Manual

1MRK 511 401-UUS A
Section 8
8.1
8.1.1
8.1.2
Bay control REC670 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
IEC 61850 IEC 60617
identification identification
PHPIOC
3I>>
SYMBOL-Z V1 EN-US
Section 8
Current protection
IP14506-1 v6
M14880-1 v5
ANSI/IEEE C37.2
device number
50
M12911-3 v6
147