Chapter 11 — Electrical Integration

download report

Transcript Chapter 11 — Electrical Integration

PowerPoint® Presentation
Photovoltaic Systems
Solar Electrical Integration
National Electrical Code • Voltage and Current
Requirements • Conductors and Wiring Methods •
Overcurrent Protection • Disconnects • Grounding
• Battery Systems
Arizona Solar Power Society
www.meetup.com/arizona-solar-power-society/
Chapter 11 — Electrical Integration
Many articles in the
NEC® are applicable to
the electrical integration
of a PV system,
particularly Article 690.
Chapter 11 — Electrical Integration
The NEC® defines the
various circuits and
components in PV
systems and specifies
their requirements.
Chapter 11 — Electrical Integration
Array open-circuit voltage
is corrected for low
temperatures to yield the
maximum possible PV
circuit voltage.
Chapter 11 — Electrical Integration
Conductor sizes typically
used in PV systems
range from 18 AWG to
4/0 AWG. Conductors
may be solid or stranded.
Larger conductors have
lower resistance for a
given length.
Chapter 11 — Electrical Integration
Ampacity is the currentcarrying capacity of a
conductor, which
depends on the
conductor’s type, size,
and application.
Chapter 11 — Electrical Integration
Conductor ampacity
must be derated for high
temperatures.
Chapter 11 — Electrical Integration
For conduits installed on rooftops, an extra temperature
adder is needed to account for the extreme ambient
temperatures of the environment. The adjusted ambient
temperature is then used to determine the temperaturebased ampacity correction factor.
Chapter 11 — Electrical Integration
Conductor ampacity must be derated for more than
three current-carrying conductors together in a
conduit or cable.
Chapter 11 — Electrical Integration
Size, insulation type,
resistances, and other
information are printed
on the outer jacket of
conductors.
Chapter 11 — Electrical Integration
Conductors in different parts of a PV system have
different application requirements.
Chapter 11 — Electrical Integration
Source-circuit conductors
are permitted to be
exposed if the conductor
insulation has the
required environmental
resistances.
Chapter 11 — Electrical Integration
Modules are typically
connected together in PV
source circuits with
external, exposed
connectors.
Chapter 11 — Electrical Integration
When tightened properly,
screw terminals produce
secure and lowresistance connections.
Chapter 11 — Electrical Integration
Lugs are crimped conductor terminations in ring, fork,
spade, or pin shapes.
Chapter 11 — Electrical Integration
Splicing devices, such as
screw terminal blocks,
are used in PV systems
to connect or extend
conductors, parallel array
source circuits, or tap
service-entrance
conductors for supplyside interconnections.
Chapter 11 — Electrical Integration
Several NEMA plug-andreceptacle configurations
are acceptable for use
with DC branch circuits.
Chapter 11 — Electrical Integration
Module junction boxes
contain and protect the
module terminal
connections and diodes
in the source circuit.
Some are fieldaccessible.
Chapter 11 — Electrical Integration
Multiple PV source
circuits are combined into
the PV output circuit
within the combiner box.
Chapter 11 — Electrical Integration
Blocking diodes are
installed in the source
circuit and bypass diodes
are installed within a
module or its junction
box. These diodes
prevent power loss due
to reverse current or
high-resistance
conditions.
Chapter 11 — Electrical Integration
Bypass diodes may be
field-installed in the
module junction box.
Chapter 11 — Electrical Integration
A number of different
types of conduit may be
used in PV systems if
they have the necessary
resistances, such as
moisture and high
temperature resistance
for source circuits.
Chapter 11 — Electrical Integration
Current-limiting
overcurrent protection
devices open a short
circuit before current
reaches its highest value.
Chapter 11 — Electrical Integration
Overcurrent protection
devices include fuses
and circuit breakers of
various types and
ratings.
Chapter 11 — Electrical Integration
Array source circuits are
fused individually within
the source-circuit
combiner box.
Chapter 11 — Electrical Integration
Overcurrent protection
for the inverter output
circuit depends on the
system or utility
interconnection type.
Overcurrent protection
and disconnecting means
for this circuit may also
be combined by using
circuit breakers or fused
disconnects.
Chapter 11 — Electrical Integration
Connecting a 120 V
inverter to a 120/240 V
system with multiwire
branch circuits causes
dangerous overloading in
the grounded (neutral)
conductor and must be
avoided.
Chapter 11 — Electrical Integration
The array disconnect
opens all current-carrying
conductors in the PV
output circuit.
Chapter 11 — Electrical Integration
The AC disconnect of an
interactive PV system
may be located close to
the main utility service
disconnect, which can
satisfy utility
requirements for an
external, visible-break,
and lockable PV system
disconnect.
Chapter 11 — Electrical Integration
Switches or circuit
breakers are required to
isolate and disconnect all
major components in a
PV system from all
ungrounded conductors
of all power sources.
Chapter 11 — Electrical Integration
The DC grounding
system and the AC
grounding system must
be connected together
with a bonding
conductor. The array
may also require a
separate grounding
electrode system.
Chapter 11 — Electrical Integration
Some inverters include fuses as array ground-fault
protection in their DC input circuits.
Chapter 11 — Electrical Integration
Circuit breakers can be
used for array groundfault protection when the
inverter does not already
provide this protection.
Chapter 11 — Electrical Integration
A ground-fault circuit
interrupter (GFCI) senses
differences between the
current in the grounded
and ungrounded
conductors, indicating a
ground fault, and opens
the circuit in response.
Chapter 11 — Electrical Integration
Modules should be
connected to each other
and the mounting
structure with grounding
conductors to ensure a
continuous grounding
connection.
Chapter 11 — Electrical Integration
Equipment grounding
conductors are sized
based on the rating of the
overcurrent protection
device in the circuit.
Chapter 11 — Electrical Integration
Lightning protection is
especially important in
the southeastern states,
which have the highest
lightning-strike density in
the United States.
Chapter 11 — Electrical Integration
A lightning protection
system includes a
network of air terminals,
a grounding electrode
(down) conductor, and a
set of grounding
electrodes.
Chapter 11 — Electrical Integration
Surge arrestors may be
incorporated into
equipment or can be
installed on circuits as
separate devices.
Chapter 11 — Electrical Integration
Connectors may be used
for disconnecting highvoltage battery banks for
servicing.