Underpower Logic; Application Notes; Low Forward Power Considerations; Low Forward Power Setting Guidelines - GE MiCOM P40 Agile Technical Manual

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Chapter 12 - Power Protection Functions
3.2

UNDERPOWER LOGIC

A Phase Watts
A Phase VA
Power<1 1 Ph Watt
Power<1 1 Ph VAR
Power<1 Mode
Active
-1
Reactive
3 Phase Watts
3 Phase VA
Power<1 3 Ph Watt
Power<1 3 Ph VAR
Power<1 Mode
Active
-1
Reactive
Power<1Direction
Forward
Reverse
Power<1 Status
Enabled
All Poles Dead
V<1 Poledead Inh
Enabled
VTS Slow Block

Figure 138: Underpower logic

3.3

APPLICATION NOTES

3.3.1

LOW FORWARD POWER CONSIDERATIONS

The Low Forward Power protection can be arranged to interlock 'non-urgent' protection tripping using the
programmable scheme logic. It can also be arranged to provide a contact for external interlocking of manual
tripping. To prevent unwanted alarms and flags, a Low Forward Power protection element can be disabled when
the circuit breaker is opened via Pole Dead logic.
The Low Forward Power protection can also be used to provide loss of load protection when a machine is
motoring. It can be used for example to protect a machine which is pumping from becoming unprimed, or to stop
a motor in the event of a failure in the mechanical transmission.
A typical application would be for pump storage generators operating in the motoring mode, where there is a need
to prevent the machine becoming unprimed which can cause blade and runner damage. During motoring
conditions, it is typical for the protection to switch to another setting group with the low forward power enabled
and correctly set and the protection operating mode set to Reverse.
A low forward power element may also be used to detect a loss of mains or loss of grid condition for applications
where the distributed generator is not allowed to export power to the system.
3.3.2

LOW FORWARD POWER SETTING GUIDELINES

Each stage of power protection can be selected to operate as a forward power stage by selecting the Power<(n)
Direction cell to Forward.
264
&
&
X
X
&
1
1
&
Power>1TimeDelay
&
1
&
Power>1TimeDelay
&
Note: This diagram does not show all stages . Other stages follow similar principles.
DT
DT
P14xEd1-TM-EN-1
P14x
Power<1 A Start
Power<1 A Trip
Power<1 3 PhStart
Power<1 3Ph Trip
V00901

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