APPLICATION
Inverters
An inverter is a device that converts DC power
from the battery bank to AC power for various
loads. In smaller PV systems, it may be possible to
eliminate this component altogether. In larger
systems incorporating components that demand
AC power, an inverter must be utilized. Also, if the
instrument site is located some distance from the
power production site, an inverter allows for an
efficient means of getting electricity to the point of
use. Alternating current is easier to transport over
long distances and has become the conventional
modern electrical standard.
There are two fundamental categories of inverters:
synchronous and static or stand-alone.
Synchronous inverters are capable of being tied
into the electrical grid, or utility power. Except in
the largest of infrastructure-based systems, this on all PV systems regardless of operating voltage, Graph shows as
type of inverter finds little application in the field of obtaining a true earth ground in polar temperature
polar research. Static inverters are designed for environments can often be difficult or impossible to decreases, charging
independent, utility-free power systems and are the obtain. In areas of permafrost, rocky soil, or voltages must increase
type most often used for remote PV applications. muskeg, grounding plates or grounding rings
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made of bare copper will typically provide a
Balance-of-System Components – satisfactory earth ground. This earth ground must
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Conductors be bonded to every metal electrical box or
.solar
PV systems always incorporate DC circuits and component enclosure, receptacle, and bare metal
often utilize an inverter for AC circuitry as well. AC frame. The PV panels should be interconnected at
-pv-management.com
and DC wiring systems have distinct requirements the point specified on the frame and referenced
and should never be mixed in conduit, raceways, back to the earth ground. The grounding wire is
or junction boxes. DC systems are typically low never fused or switched, and the entire system
voltage (< 48 VDC) and thus require much larger must be grounded at only one point.
wire sizes than AC systems. Indeed, the wire size
required to avoid unacceptable voltage drops In an ice cap environment, achieving an earth
across any distance or in high-current applications ground is typically not possible. As such,
Issue I 2010
is often surprisingly large. Many systems have grounding is dealt with in the same way as within
experienced poor performance due to the automotive industry. In this method, the frame
inadequately sized conductors.
The polar environment introduces additional
challenges in system wiring. Larger cables used
for battery connections become incredibly stiff and
difficult to work with due to the insulated
sheathing. Coarse-stranded wire intended for
residential AC-type use exacerbates the difficulty.
Pre-assembling as much of the system as possible
will reduce field installation woes. However,
installing battery cables and runs from the PV array
are often difficult to avoid. Remember that if wires
are to be left exposed to the environment, they
must be rated for exposure including UV radiation.
If it does not say “UV rated,” it probably is not.
Grounding
Grounding is a deceptively complicated issue.
Although the NEC requires equipment grounding
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