ABB Relion 670 Series Applications Manual page 133

1MRK 511 401-UEN Rev. K
Section 8
8.1 Instantaneous phase overcurrent protection PHPIOC
8.1.1 Identification
Function description
Instantaneous phase overcurrent
protection
8.1.2 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
operate very quickly for faults very close to the generation (and relay) point, for which very
high fault currents are characteristic.
The instantaneous phase overcurrent protection PHPIOC can operate in 10 ms for faults
characterized by very high currents.
8.1.3 Setting guidelines
The parameters for instantaneous phase overcurrent protection PHPIOC are set via the local
HMI or PCM600.
This protection function must operate only in a selective way. So check all system and
transient conditions that could cause its unwanted operation.
Only detailed network studies can determine the operating conditions under which the
highest possible fault current is expected on the line. In most cases, this current appears
Bay control REC670
Application manual
Current protection
IEC 61850
identification
PHPIOC
© Copyright 2017 Hitachi Power Grids. All rights reserved
IEC 60617 ANSI/IEEE C37.2
identification device number
50
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SYMBOL-Z V1 EN-US
Section 8
Current protection
IP14506-1 v6
M14880-1 v5
M12911-3 v6
IP14979-1 v1
M12915-4 v9
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