8.6
Loss of voltage check LOVPTUV (27)
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Loss of voltage check
LOVPTUV
-
27
8.6.1
Introduction
Loss of voltage check (LOVPTUV, 27) is suitable for use in networks with an
automatic system restoration function. LOVPTUV (27) issues a three-pole trip
command to the circuit breaker, if all three phase voltages fall below the set value for a
time longer than the set time and the circuit breaker remains closed.
8.6.2
Principle of operation
The operation of Loss of voltage check LOVPTUV (27) is based on line voltage
measurement. LOVPTUV (27) is provided with a logic, which automatically
recognizes if the line was restored for at least
tRestore
before starting the
tTrip
timer.
All three phases are required to be low before the output TRIP is activated. The
PICKUP output signal indicates pickup.
Additionally, LOVPTUV (27) is automatically blocked if only one or two phase
voltages have been detected low for more than
tBlock
.
LOVPTUV (27) operates again only if the line has been restored to full voltage for at
least
tRestore
. Operation of the function is also inhibited by fuse failure and open
circuit breaker information signals, by their connection to dedicated inputs of the
function block.
Due to undervoltage conditions being continuous the trip pulse is limited to a length set
by setting
tPulse
.
The operation of LOVPTUV (27) is supervised by the fuse-failure function (BLKV
input) and the information about the open position (CBOPEN) of the associated circuit
breaker.
The BLOCK input can be connected to a binary input of the IED in order to receive a
block command from external devices or can be software connected to other internal
functions of the IED itself in order to receive a block command from internal
functions. LOVPTUV (27) is also blocked when the IED is in TEST status and the
function has been blocked from the HMI test menu. (
Blocked
=
Yes
).
Section 8
1MRK505222-UUS C
Voltage protection
546
Technical reference manual
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