Hitachi Relion 670 Series Applications Manual page 149

1MRK506375-UEN Rev. N
Section 8
8.1 Instantaneous phase overcurrent protection 2-phase
output PHPIOC
8.1.1 Identification
Function description
Instantaneous phase overcurrent
protection 2-phase output
8.1.2 Application
The transient stability of a power system depends mostly on three parameters (at constant amount of
transmitted electric power):
• The type of the fault. Two-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 railway lines depends mostly on the fault position and decreases with the
distance from the infeed point. For this reason the protection must operate very quickly for faults very
close to the relay point, for which very high fault currents are characteristic.
The instantaneous phase overcurrent protection PHPIOC can operate in one-half of the fundamental
power system cycle 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 during two-phase
fault conditions. But also examine single-phase-to-earth condition.
Also study transients that could cause a high increase of the line current for short times. A typical
example is a line with a power transformer at the remote end, which can cause high inrush current
when connected to the network and can thus also cause the operation of the built-in, instantaneous,
overcurrent protection.
Common base IED values for primary current (IBase), primary voltage (UBase) and primary power
(SBase) are set in the global base values for settings function GBASVAL.
Railway application RER670
Application manual
Current protection
IEC 61850
identification
PHPIOC
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GUID-16B23942-56A3-42E4-BC34-91FF2D3A8648 v1
IEC 60617 ANSI/IEEE C37.2
identification device number
50
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IEC15000110 V1 EN-US
Section 8
Current protection
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