4.5.5.2
Function block
TRIP
PICKUP
V
1
47U,27PS
BLOCK
GUID-BA2E06D5-7FFA-4231-9BE4-C5E14C37E5C9 V1 EN
Figure 317:
Function block
4.5.5.3
Functionality
The positive-sequence undervoltage protection function 47U, 27PS is used to detect
positive-sequence undervoltage conditions. 47U, 27PS is used for the protection of small
power generation plants. The function helps in isolating an embedded plant from a fault
line when the fault current fed by the plant is too low to cause an overcurrent function to
pickup but high enough to maintain the arc. Fast isolation of all the fault current sources
is necessary for a successful autoreclosure from the network-end circuit breaker.
The function picks up when the positive-sequence voltage drops below the set limit. 47U,
27PS operates with the definite time (DT) characteristics.
The function contains a blocking functionality. It is possible to block function outputs, the
definite timer or the function itself, if desired.
4.5.5.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are “Enable” and “Disable”.
The operation of 47U, 27PS can be described using a module diagram. All the modules in
the diagram are explained in the next sections.
V
1
Blocking
logic
BLOCK
TRIP
PICKUP
t
Timer
Level
Detector
GUID-E7F19717-CF62-4A4D-9F86-1CB5D376A420 V1 EN
Figure 318:
Functional module diagram. V
1
is used for representing positive phase
sequence voltage.
1MAC059074-MB A
Section 4
Protection functions
615 series ANSI
637
Technical Manual
Summary of Contents for Relion 615 series
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