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5.13. Power supply
The SIA-B relay is designed to be self-powered using the cell current. Besides, depending on model
it is possible to select apart from self-powered an auxiliary supply (24-230 Vdc/Vac +10%/-20%
(Dual)).
It can also be supplied from a USB cable which goes directly to the PC. The USB is plugged into
the front communications port. Using USB cable for power supply does not inhibit the USB
communications port, as it can be used simultaneously.
5.13.1.
Self-Powered relay with standard current transformers
The SIA-B powers itself from the operating current through standard current transformers that are
connected to the line. Self-powering is achieved with very low levels of current: a minimum of 75 mA
three phase current or 160 mA one phase.
The relay is maintenance free when this type of power supply is used, as it does not require auxiliary
power components (batteries). As a result, it is especially useful in any centers where auxiliary power
is not available or cannot be guaranteed, and the facilities require protection with low levels of
current.
There is a self-power transformer per each phase (3 self-power transformers), separating current
circuits completely.
5.13.2.
24-230 Vac, 50/60 Hz auxiliary power
The 24-230 Vac (+10%/-20%) auxiliary powers are taken from the transformation center secondary
voltage. If this option is required, this needs to be selected in the list of models.
It is normal for transformation substations to have auxiliary voltage. This voltage is not guaranteed
because a short-circuit may cause this auxiliary voltage loss. However, the complete auxiliary
voltage loss is produced in primary faults between phases, which are very unlikely and generate a
lot of current. In other words, for faults with low contribution of current, AC auxiliary voltage keeps
its level and supplies the relay and for faults with auxiliary voltage sag and high contribution of
current, the self-powering characteristic keeps the relay operative. The continuous operation of SIA-
B is guaranteed with the levels of self-powering (75 mA three phase current or 160 mA one phase)
and the auxiliary power supply 24-230Vac.
5.13.3.
24-230 Vdc auxiliary power supply
The 24-220 Vdc (+10%/-20%) auxiliary power is taken from the transformation center RTU power
supply. SIA-B consumes a maximum of 0.5 W in normal operation. The consumption is so reduced
that it practically does not affect the transformation substation battery of 24Vdc, being able to supply
from it, with a total guarantee and without being a loss of functionality with communications relay
because it will extract 20 mA/hour. Therefore, the relay can be powered all the time, allowing it to
be continually monitored (status, measurements of transformation center
current, events…). The
relay is totally operational at this power and if a fault occurs, the trip time matches the time setting.
In a situation where the center is deenergized, if this is energized and a fault induced with the
instantaneous function set at 20 ms, the trip time will be 20 ms.
Summary of Contents for SIA-B Series
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Page 10: ...www fanox com Rev 07 10 138 2 4 Connection diagram NOTE STRIKER 6 24 Vdc 0 135 W s...
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