7.4.6 Operation principle
SEMOD171765-4 v6
The operation of Loss of voltage check LOVPTUV is based on line voltage
measurement. LOVPTUV 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 START
output signal indicates start.
Additionally, LOVPTUV is automatically blocked if only one or two phase
voltages have been detected low for more than tBlock.
LOVPTUV 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 is supervised by the fuse-failure function (BLKU
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 is also blocked when the IED is in TEST status and
the function has been blocked from the HMI test menu. (Blocked=Yes).
Section 7 1MRK 505 384-UEN A
Voltage protection
200 Breaker protection REQ650 2.2 IEC
Technical manual
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