Detection Of A Fault During A Power Swing; Power Swing Blocking Configuration - GE MiCOM P40 Technical Manual

Chapter 10 - Power Swing Functions
The PSB timer setting defines the minimum time that the impedance trajectory must take to cross through zone 8
into zone 7 (Dt) before a power swing is deemed to have taken place. A power swing is indicated if Dt > PSB Timer.
3.2

DETECTION OF A FAULT DURING A POWER SWING

Faults are characterised by step changes in superimposed current (ΔI) rather than more gradual transitions
symptomatic of a power swing.
When a power swing is in progress, the threshold for the phase selector is increased to a value twice that of the
maximum prevailing superimposed current caused by the swing. A fault will cause a ΔI greater than this raised
threshold, so the fault will be detected by the phase selector. Operation of the phase selector in this condition
unblocks the PSB function, to allow tripping of Distance elements.
To provide stability for external faults, the blocking signal is only removed from zones that start within two cycles
of the phase detector recognising the fault:
Any Distance element measuring an impedance inside its characteristic before the phase selector detects the fault
remains blocked. This prevents tripping for a swing impedance that may be coincidentally passing through a fast-
acting zone, and which could cause spurious tripping if all elements were unblocked without qualification.
Any Distance element that measures an impedance inside its characteristic after the two cycle ΔI window of the
phase selector has expired, remains blocked. This prevents tripping for a continued swing that may pass through a
fast acting zone which could cause spurious tripping if the element was allowed to unblock by an unqualified
phase selector reset.
3.3

POWER SWING BLOCKING CONFIGURATION

To use the Power Swing function, you must ensure that the PowerSwing Block setting in the CONFIGURATION
column is set to Enabled. You can set Power Swing Blocking to Indication (where alarms are raised but no
blocking is imposed), or to Blocking (where blocking actions are imposed).
To define what the action the PSB function should take, you need to set the distance zones. The available distance
zones are:
Zone 1 Ph. PSB: Zone 1 phase
Zone 2 Ph. PSB: Zone 2 phase
Zone 3 Ph. PSB: Zone 3 phase
Zone 4 Ph. PSB: Zone 4 phase
Zone P Ph. PSB: Zone P phase
Zone 1 Gnd. PSB: Zone 1 ground
Zone 2 Gnd. PSB: Zone 2 ground
Zone 3 Gnd. PSB: Zone 3 ground
Zone 4 Gnd. PSB: Zone 4 ground
Zone P Gnd. PSB: Zone P ground
The following options are available for each of the above zones:
Allow Trip: If a power swing locus stays in the Distance characteristic for a duration equal to the element time
delay, the trip is allowed.
Blocking: Prevents tripping for that element, even if a power swing locus enters the element's characteristic.
Delayed Unblock: This maintains the block for a set duration after a power swing has been detected. To use it,
you must set PSB Unblocking to Enabled, and then set the desired PSB Unblock dly time for removing the block.
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P446SV
P446SV-TM-EN-1