Function Block; Functionality; Operation Principle - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.2.5.2
4.2.5.3
4.2.5.4
620 series ANSI
Technical Manual

Function block

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Figure 132: Function block

Functionality

The positive-sequence undervoltage protection 27PS is used to detect positive-sequence
undervoltage conditions. 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. 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 the positive-sequence undervoltage protection can be described using a
module diagram. All the modules in the diagram are explained in the next sections.
GUID-F1E58B1E-03CB-4A3C-BD1B-F809420397ED V1 EN
Figure 133: Functional module diagram. V
sequence voltage.
Protection functions
is used for representing positive phase
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