ABB HiPerGuard MV UPS User Manual page 22

22 H I P E R G U A R D M V U P S U S E R M A N U A L
3.2.2 Independent mode
If the utility power is no longer available or in a prolonged sag event, the HiPerGuard MV UPS opens its input
breaker and transfers the load to the energy storage, operating now in Independent mode. The energy storage al-
lows ride-through time for either the utility power to be restored or for the time necessary for an alternative en-
ergy source to be activated, such as a generator for example.
3.2.3 Transition from Power Conditioning to Independent mode
The HiPerGuard MV UPS Main Controller (MC) manages the input circuit breaker, based on the input voltage and
current measurements shown in Figure 3.04.
• If the voltage at the input side is between 110 and 90% of the nominal value, it is conditioned to 1 p.u.
at the load side (Power Conditioning Mode).
• If the voltage is between 90 and 85% of the nominal value, the HiPerGuard MV UPS will monitor and will
be ready to transition to the Independent mode. The expected threshold for the transfer depends on
the sag depth and remaining voltage.
• If the voltage is between 85% and 50%, the MV UPS will open the input circuit breaker. The time to open
will be between approximately 1 and 10 seconds, depending on the input voltage level.
• If the voltage is below 50%, the MV UPS will command the input circuit breaker to open in milliseconds.
• In case of an outage or prolonged sag event, the MV UPS opens the input circuit breaker and goes into
the Independent mode.
The input breaker management graph is split into two regions. The first part, a slow filter curve down to 50% in-
put voltage, is designed for thermal management of the MV UPS and protection coordination. It allows the MV
UPS to keep the input circuit breaker closed for typically 1 second at 50%.
The second part, a fast filter for input values below 50% and down towards 0% remaining voltage, responds
quickly so as to prevent unnecessary tripping due to sub-cyclic events and transients.
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Figure 3.03: HiP-
erGuard MV UPS
Independent mode