Table 315: VRPVOC (51V) Non group settings (basic)
Name Values (Range) Unit Step Default Description
GlobalBaseSel 1 - 12 - 1 1 Selection of one of the Global Base Value
groups
8.16.6 Monitored data
PID-3858-MONITOREDDATA v5
Table 316: VRPVOC (51V) Monitored data
Name Type Values (Range) Unit Description
IMAX REAL - A Maximum phase current magnitude
VUMIN REAL - kV Minimum ph-to-ph voltage magnitude
8.16.7 Operation principle
8.16.7.1 Measured quantities
GUID-0D511C03-3750-4F61-9555-69DAD96CDC21 v5
The voltage-restrained time overcurrent protection VRPVOC (51V) function is always connected to
three-phase current and three-phase voltage input in the configuration tool (ACT), but it will
always measure the maximum of the three-phase currents and the minimum of the three phase-
to-phase voltages. If frequency tracking mode for preprocessing blocks is used, then the function
operates properly in wide frequency range (e.g. 10-90 Hz).
8.16.7.2 Base quantities
GUID-08944177-73CF-4FB4-818E-3B7AC4F625EE v4
GlobalBaseSel
defines the particular Global Base Values Group where the base quantities of the
function are set. In that Global Base Values Group:
IBase
shall be entered as rated phase current of the protected object in primary amperes.
VBase
shall be entered as rated phase-to-phase voltage of the protected object in primary kV.
8.16.7.3 Overcurrent protection
GUID-7BB29872-EBC1-4628-AFB5-7A15E2EC41A8 v2
The overcurrent step simply compares the magnitude of the measured current quantity with the
set pickup level. The overcurrent step picks up if the magnitude of the measured current quantity
is higher than the set level.
Voltage restraint/control feature
GUID-E7C59BAD-47A1-46C2-8929-7E589548045C v3
The overcurrent protection operation is made dependent of a measured voltage quantity. This
means that the pickup level of the overcurrent step is not constant but decreases with the
decrease in magnitude of the measured voltage quantity. This feature affects the pickup current
value of both definite time and inverse time IDMT overcurrent protection; in particular the
overcurrent with IDMT curve operates faster during low voltage conditions. Two different types of
dependencies are available:
• Voltage restrained overcurrent (when setting parameter
VDepMode
=
Slope
); the pickup level
of the overcurrent stage changes according to the Figure 305. The voltage restrained
characteristic is defined by the two points: (0.25*
VBase
;
VDepFact
*
Pickup_Curr
/100*
IBase
)
Section 8 1MRK 502 066-UUS B
Current protection
574
Technical manual
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