Undervoltage Protection Logic; Figure 95: Undervoltage - Single And Three Phase Tripping Mode (Single Stage) - GE MiCOM P40 Agile Technical Manual

P14D
Outputs are available for single or three-phase conditions via the V< Operate Mode cell for each stage.
2.2

UNDERVOLTAGE PROTECTION LOGIC

V< Measur't Mode
VA
VAB
V<1 Voltage Set
V<1 Time Delay
V< Measur't Mode
VB
VBC
V<1 Voltage Set
V<1 Time Delay
V< Measur't Mode
VC
VCA
V<1 Voltage Set
V<1 Time Delay
All Poles Dead
V<1 Poledead Inh
Enabled
VTS Fast Block
V<1 Timer Block
V< Operate Mode
Any Phase
Three Phase
V00803

Figure 95: Undervoltage - single and three phase tripping mode (single stage)

The Undervoltage protection function detects when the voltage magnitude for a certain stage falls short of a set
threshold. If this happens a Start signal, signifying the "Start of protection", is produced. This Start signal can be
blocked by the VTS Fast Block signal and an All Poles Dead signal. This Start signal is applied to the timer module
to produce the Trip signal, which can be blocked by the undervoltage timer block signal (V<(n) Timer Block). For
each stage, there are three Phase undervoltage detection modules, one for each phase. The three Start signals
from each of these phases are OR'd together to create a 3-phase Start signal (V<(n) Start), which can be be
activated when any of the three phases start (Any Phase), or when all three phases start (Three Phase), depending
on the chosen V< Operate Mode setting.
The outputs of the timer modules are the trip signals which are used to drive the tripping output relay. These
tripping signals are also OR'd together to create a 3-phase Trip signal, which are also controlled by the V< Operate
Mode setting.
If any one of the above signals is low, or goes low before the timer has counted out, the timer module is inhibited
(effectively reset) until the blocking signal goes high.
In some cases, we do not want the undervoltage element to trip; for example, when the protected feeder is de-
energised, or the circuit breaker is opened, an undervoltage condition would obviously be detected, but we would
not want to start protection. To cater for this, an All Poles Dead signal blocks the Start signal for each phase. This
is controlled by the V<Poledead Inh cell, which is included for each of the stages. If the cell is enabled, the relevant
stage will be blocked by the integrated pole dead logic. This logic produces an output when it detects either an
open circuit breaker via auxiliary contacts feeding the opto-inputs or it detects a combination of both
undercurrent and undervoltage on any one phase.
P14D-TM-EN-8
&
&
&
&
&
&
890
&
832
414
Note: This diagram does not show all stages . Other stages follow similar principles.
VTS Fast Block only applies for directional models .
Chapter 10 - Voltage Protection Functions
789
V<1 Start A/AB
684
V <1 Trip A/AB
790
V<1 Start B/BC
685
V<1 Trip B/BC
791
V<1 Start C/CA
686
V<1 Trip C/CA
1
&
1 788
V<1 Start
&
&
1
&
683
1 V<1 Trip
&
&
189