ABB RELION REX640, Техническое руководство, Страница: 918 / 1960

function is blocked and the timers are reset. In the “Block OPERATE output” mode,
the function operates normally but the
OPERATE
output is not activated.
4.5.10.6 Application
Overvoltage in a network occurs either due to the transient surges on the network
or due to power frequency overvoltages. Surge arresters are used to protect
the network against the transient overvoltages; power frequency overvoltage
of magnitude greater than 15...20% of nominal voltage is normally handled by
traditional overvoltage protection. However, slow voltage variations are usually
quantified by calculating the RMS value of the voltage. To assess the RMS voltage,
measurements are taken over a relatively long period of time to avoid any
instantaneous effect caused by switching transients or faults.
It is important to monitor such slow voltage variation which can cause sub-optimal
operation of the equipment. EN 50160 quantifies slow voltage variation using 10
min mean RMS value. CEI EN 50160 standard indicates that the RMS value of the
voltage calculated over a period of 10 min should not exceed 110% of the nominal
voltage; if the voltage exceeds this level, the generator must be disconnected from
the network within 3 s. PHVPTOV provides overvoltage protection by calculating the
RMS value over a period of 10 min.
A sudden change in the magnitude of the supply voltage is not immediately
detected by the RMS calculation; hence this is mainly used as an indication of
voltage quality supplied by the utility.
4.5.10.7 Signals
PHVPTOV Input signals
Table 872: PHVPTOV Input signals
Name Type Default Description
U3P SIGNAL - Three-phase voltages
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
INITIALIZE BOOLEAN 0=False Initialize the volt-
age average measure-
ment
RESET BOOLEAN 0=False Reset the volt-
age average measure-
ment values
PHVPTOV Output signals
Table 873: PHVPTOV Output signals
Name Type Description
OPERATE BOOLEAN Operate
START BOOLEAN Start
Protection functions 1MRS759142 F
918 REX640
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