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Metering and Extended Protective Relaying
Y
lry
Voltage Unbalance
-
Voltage Unbalance
is
a
protective relay-
ing
function that protects
agarnst an
unbalance
in
the
linelo-
line
voltages.
Each
lineto-line voltage,
Vab,
Vbc and Vca,
is
compared to the arithmetic average of the three line{o-line
voltages,
V;K>K.
Tripping occurs
when any
line{o-line voltage
exceeds the programmed unbalance pickup for a period
of
time equal to
the
delay time setting. The
pickup
must remain
active
for
the entire delay time for
a
trip
to
occur,
lf
the
voltage
unbalance condition
subsides
in
less
time than
the
delay time,
the
pickup
will
go
inactive and the
voltage unbalance protec-
tive
relaying
function will be
reset, When
tripping occurs,
the
actual condition
that
caused
the
trip
is
recorded
in
the
trip unit's
nonvolatile
trip
log,
Programmable settings:
Trip:
Yes, No or Clr
Pickup:
5%
Io
50% in increments
of
I %
Delay: I
to
15
seconds
in increments
of
1
second
Average
line-to-line
voltage
is
defined as [Vab
+
Vbc +
Vca]
/3
=
VXX
Pickup
occurs
if
the absolute value
of
1
-
(Vab/V**)
or
(Vbc/
V**)
or
(Vca/VXX) X
100% is equal to or greater than
the
pickup
setting. Voltage unbalance
is
disabled for any
line
voltage
less
than
15%
of V SCALE.
Data
recorded
in
the event
log:
Pickup
Active:
Time
at
which pickup went active
and
Vab,
Vbc and
Vca
at pickup.
Pickup
Inactive:
Time at
which pickup went
inactive,
Under Voltage -
Under
Voltage
is a
protective
relaying
func-
tion
that protects against
a
line-to-line under voltage condition.
Tripping
occurs when any line-to-line voltage
drops
below the
programmed
under
voltage pickup
for a
period
of
time equal
to
the
delay time setting.
The
pickup
must remain active
for
the
entire delay time
for a trip to occur. lf the
under
voltage
condition
subsides
in less
time than the delay time, the
pickup
will go
inactive
and
the
under voltage protective
relaying
function wtll be reset.
When
tripping
occurs,
the
condition that
caused
the
trip
is
recorded
in
the
trip unit's nonvolatile
trip
log.
Programmable settings:
Trip:
Yes, No or Clr
Pickup:
60 to 660
volts
in increments
of
I
volt
Delay:
1
to
l5
seconds
in increments
of
.1
second
Pickup occurs
if
Vab,
Vbc
or
Vca
is
less than the
pickup setting.
Data
reco'oed
in
the
event
log:
Pickup
Active:
Time
at
which pickup went active
and
Vab,
Vbc and
Vca
at
pickup.
Pickup
lnactive:
Time at
which pickup went
inactive.
Over Voltage
- Over Voltage
is
a
protective
relaying function
that
protects against
a
line{o-line over voltage
condition.
Tripping occurs when any
line-to-line
voltage
exceeds
the
programmed
over
voltage pickup
for
a
period
of
time equal to
the
delay time setting. The
pickup
must remain active for the
entire delay
time for
a
trip
to
occur.
lf
the over
voltage
condiiion
subsides in
less
time than the delay time, the pickup will
go
inactive and
the over
voltage protective
relaying
function
will
be
reset. When
tripping occurs,
the
actual condition
that
caused
the
trip
is
recorded
in
the
trip unit's nonvolatile trip
log,
Programmable settrngs:
Trip:
Yes, No or Clr
Pickup:
60
to
660
volts
in increments
of
1
volt
Delay:
1
to
15
seconds
in increments
of
1
second
Pickup occurs
if
Vab, Vbc or Vca
is
greater than the pickup
setting.
Data
recorded
in
the event
log:
Pickup
Active:
Time at
which pickup
went
active
and
Vab,
Vbc and
Vca
at pickup.
Pickup
lnactive:
Time at
which pickup went
inactive.
Under Frequency
- Under Frequency
is
a
protective
relaying
function that protects against an
under
frequency
condition.
Tripping occurs
when
the
frequency
drops
below
the
pro-
grammed
under
frequency pickup
for
a period
of time equal
to the delay time setting. The pickup must
remain
active
for
the entire delay time for
a
trip to
occur,
lf
the under
frequency
condition subsides
in less time than
the
delay time,
the pick-
up will go
inactive
and the under frequency
protective
relaying
f
unction will
be reset. When
tripping
occurs,
the
actual
condition
that caused the
trip is
recorded in the
trip
unit's
nonvolatile
trip log.
Under
Frequency
is
disabled
if Va
is
less than
90V,
Programmabte
settin gs:
Trip:
Yes,
No
or Clr
Pickup:
45,0
to
7O.0
Nz in increments
ol
.1
l1z
Delay:
1
to
15
seconds
in increments
of
1
second
Pickup
occurs
if
the
frequency
is less
than the
pickup
setting.
Data
recorded
in
the
event
log:
Pickup
Active:
Time
at
which pickup went active
and
frequency at
pickup.
Pickup
Inactive:
Time at
which pickup went
inactive.
Over Frequency
-
Over Frequency is
a
protective
relaying
function
that
protects against
an
over frequency
condition.
Tripping occurs
when
the
f
requency exceeds
the
programmed
over
frequency pickup
for a
period
of time equal to the delay
time setting.
The
pickup
must
remain
active
for the
entire delay
timeforatriptooccur,
lf
theoverfrequencycondition subsides
in
less time
than the delay time, the
pickup
wiil go inactive and
the
over
frequency protective relaying function will be
reset.
When
tripping
occurs,
the
actual condition that caused
the
trip
is
recorded
in
the
trip
unit's
nonvolatile trip
log. Over
Frequency
is
disabled
if
Va is less than
90V.
Programmable settings:
Trip:
Yes, No or Clr
Pickup:
45,0 to 70 0
I'z
in increments
of
.1
l1z
Delay:
1
to
15
seconds
in increments
of
1
second
Pickup
occurs
if
the frequency
ls
greater
than
the
pickup
setting.
Data
recorded
in
the
event
log:
Pickup
Active:
Time
at
which pickup went active
and
frequency at
pickup.
Pickup
Inactive:
Time at
which pickup went
inactive.
rv
z.)

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