of the generator’s current rating. This standard hinges upon
generator design and operation. “The output of the generator
must be protected from overloads. The circuit breakers, fuses,
or other acceptable overcurrent protective means should be
able to prevent overloading of the conductor.” [445.12(a)]
According to Article 445.18, generators require a disconnect
device unless they can be shut down easily and do not operate
in parallel with another voltage source.
Point-of-Utility Connections
Utility grid-tied PV systems are connected through the customer’s service
entrance section. This is known as the SES in almost every situation. Utility-
owned and developer-owned PV systems attach on dedicated PV service
entrances. These SESs are often set up for the project independent of any load
other than that of the grid. The NEC allows this. Article 230.82(6) gives the par-
ticular requirements needed for connections. Customer-owned PV systems
couple through a breaker. Those PV systems must always have an appropriate
means of disconnecting.
The place where the PV system connects to the utility service is called the
point-of-utility connection. Locate the point-of-utility connection at the main
distribution panel board. The easiest way to do this is typically to place the
inverter output breaker on the customer load side of the main breaker in the SES.
This will feed the house loads first with any excess being sent out to the grid. The
inverter output must have a circuit breaker or fuse in the distribution panel board.
The circuit breaker or fuse must be appropriately labeled. When connecting the
inverter to the circuit breaker, use appropriate techniques to secure the enclosure.
Make sure to follow NEC Article 705.12, which requires that
The enclosure be secured through a reserved circuit breaker or its own fuse
on the disconnecting means.
Overcurrent device amps providing power to the conductor be no greater
than the conductor’s amps.
Point-of-utility connection be on the line part of all the ground-fault
defensive mechanisms.
All mechanisms with overcurrent devices be marked to
warn about power supply.
Optional Standby System Panels
According to NEC Article 702.7, optional standby system
panel boards have to be labeled. They are labeled to warn
workers that an inverter supplies current into the panel board.
[690.10(c)]
NOTE
PV systems with backup generators use
a disconnect to separate the generator
from the rest of the PV system in the
case of repairs and maintenance.
NOTE
Typically, Article 690.10 is for
standalone PV systems, but it can be
applied to grid-tied PV systems with
backup batteries. The battery backup
system acts as a standalone PV system
in instances where the power is out.
CHAPTER 7 PV Technology—Cells, Panels, Arrays, Balance of System, and Inverters 171
Absorption stage
Ampacity
Bulk-charging phase
Bypass diode
Clipping
Equalization stage
Float charge
Ground-fault protection (GFP)
I-V curve
Low voltage disconnect (LVD)
Maximum power current (Imp)
Maximum Power Point (MPP)
Maximum power voltage (Vmp)
Open-circuit voltage (Voc)
Point-of-utility connection
Service entrance section or service entrance
switchboard (SES)
Shading analysis
Source circuits
Standard test conditions (STC)
Chapter 7 Summary
PV power system technology is very intricate. Each component must feed into the other to
properly create an efficient PV system. Details about PV cells, panels, and arrays bring insight
into how to lay out the PV system components. The collective of PV components, often
referred to as the balance of system, is discussed in this chapter. The BOS layout and equip-
ment function in harmony. This chapter culminates with reviewing the installation of various
PV components.
Key ConCeptS and termS
Chapter 7 aSSeSSment
PV Technology—Cells, Panels, Arrays, Balance of System, and
Inverters
1. Grounding conductors carry current.
A. True
B. False
2. Grounded conductors carry current.
A. True
B. False
3. Which NEC article deals with grounding codes?
A. NEC 2011, Article 110
B. NEC 2011, Article 250
C. NEC 2011, Article 300
D. NEC 2011, Article 400
4. The DC disconnect switch is installed before the:
A. AC main disconnect/isolator switch.
B. inverter.
172
ADVANCED PHOTOVOLTAIC INSTALLATIONS
C. grounding electrode conductor.
D. None of the above
5. If a 12V PV system and a 48V PV system operate at the same power level, the
wire resistance of the 48V system will be _______ as much compared with the
wire resistance of the 12V system.
A. 1/16th
B. 1/4th
C. 4 times
D. 16 times
6. NEC Article 445.13 states that the conductor size and its ampacity must be at
least _______ percent of the generator’s current rating.
A. 125
B. 115
C. 150
D. 225
7. Which NEC article discusses temperatures at which various wire sizes are
appropriate?
A. NEC Article 310.15(b)(16)
B. NEC Article 310.37
C. NEC Article 312.5
D. NEC Article 314.28
8. The charge controller battery temperature sensor should be connected to
which area of the battery?
A. Battery compartment sides
B. End of a battery row
C. On the bottom of a battery
D. Between two batteries
9. Connections made in series strings are to raise:
A. current.
B. voltage.
C. conduit runs.
D. All of the above
E. None of the above
10. Different battery cable lengths between batteries can cause:
A. extreme voltage drop.
B. imbalanced voltages and current for battery charging and discharging.
C. overheating.
D. currents that falter.
CHAPTER 7 PV Technology—Cells, Panels, Arrays, Balance of System, and Inverters 173
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