Function Block - ABB 615 series Technical Manual

1MAC059074-MB A
4.5.5.2
4.5.5.3
4.5.5.4
615 series ANSI
Technical Manual

Function block

47U,27PS
V TRIP
1
BLOCK PICKUP
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Figure 317: Function block
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.
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
Level
Detector
Blocking
BLOCK
logic
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Figure 318: Functional module diagram. V
sequence voltage.
Timer
TRIP
t
PICKUP
is used for representing positive phase
1
Section 4
Protection functions
637