ABB REL650 series, Applications Manual, Page: 175 / 516

Section 7 Current protection
7.1 Instantaneous phase overcurrent protection 3-phase
output PHPIOC (50)
7.1.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Instantaneous phase overcurrent
protection 3-phase output
PHPIOC
3I>>
SYMBOL-Z V1 EN
50
7.1.2 Application
Long transmission lines often transfer great quantities of electric power from production
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
1MRK 506 334-UUS A
Section 7
Current protection
169
Application manual