Photovoltaic System Overcurrent Protection
Introduction
Solar Photovoltaic (PV) systems have, over the last fifty years, evolved into a mature, sustainable and adaptive technology.This technology is improving as solar cells increa in efficiency and modules attain better aesthetic appearance.
As a result, solar power is gaining more acceptance and is becoming an
increasingly cost-effective and clean
alternative to conventional energy sources.
As the installations and demand for PV systems increas so does the need for effective electrical protection.
PV systems, as with all electrical power systems, must have appropriate
overcurrent protection for equipment and conductors.
purposCooper Bussmann (the world leader in overcurrent protection products) has
developed a revolutionary new fu link for protecting photovoltaic systems.
加油英文This development was implemented
through coordinated rearch and testing with leading Solar Panel/Solar System manufacturers.
Photovoltaic Protection System from Cooper Bussmann
Photovoltaic System Overcurrent Protection
A number of PV panels in ries is termed a string A number of strings in parallel is termed an array
Solar Power generation systems are made of Photovoltaic cells and Power inverters. The
photovoltaic cells utili the power of sunlight to converters photons to clean DC (Direct Current) electricity.
The Electricity generated by the Solar Cells is then fed into a Power Inverter (PV inverter) that converts and regulates the DC source into usable AC power.The AC power can then be ud locally for specific remote equipment, residential homes or fed directly back into the power grid and ud as environmentally clean energy.
Energy content of sunlight: sunlight has an energy content of 1kW (1000 watts) per square meter.The typical Solar Panel achieves between 10% and 15% efficiency conversion.
How Solar Power Systems work
The voltage output of a Solar Panel/Array is defined by the number of individual cells in ries. An individual panel (e Fig. 1) is made up of a ries string of photovoltaic cells.
专四考试时间Globally there is a push for utilizing higher voltages (trending to 1000Vdc and above).
A number of PV panels in ries is termed a string
A number of strings in parallel is called an array
The vast majority of large Solar Farms in North America are 600Vdc, but following the lead from
Europe to increa voltages up to 1000Vdc to achieve more efficiency.
Solar Power Protection System from Cooper Bussmann
V+
Figure 1
Overcurrent Protection of PV Systems
The National Electrical Code ®defines the maximum circuit current as 125% of the short-circuit current of the PV module (I sc ). The conductors and the
overcurrent protective device are then sized at 125% of the maximum circuit current or 1.56 x I sc .Additionally, International standards such as BS EN7671Sec 712 for Solar Photovoltaic (PV) Power Supply systems specify that conductors current carrying ability must be equal to or greater than 1.25 x I sc STC* at any location. The I sc is published by the PV module manufacturers on datasheets. The I sc is typically only 110-115% of the maximum power
current (I pm )of the PV module.
This means that unlike typical grid connected AC systems, the available short circuit current is limited and the overcurrent protective devices will need to operate effectively on low levels of fault current. For this reason Cooper Bussmann has conducted extensive rearch and development of fus that are specifically designed and tested to safely protect PV systems with high DC voltages and low fault currents.
DCM - 600Vdc
PV - 1000Vdc
*I sc STC: The Electrical data applies under Standard Test Conditions (STC): Radiation 1000 W/m 2with a spectrum of AM 1.5 and at cell temperature of 25o C.
PV Fu - 1000Vdc
DCM - 600Vdc
Photovoltaic System Overcurrent Protection
Depending on the desired capacity of the PV system, there may be veral PV strings connected in parallel to achieve higher currents and subquently more power.
PV systems that have three or more strings connected in parallel need to have each string protected (systems that have less than three strings will not generate enough fault current to damage the conductors/equipment and therefore do not prent a safety hazard as long as the conductor was sized properly bad on local code requirements).
Where three or more strings are connected in parallel a fu on each string will protect the conductors from damage and help minimi any safety hazards. It will also isolate the faulted string so that the rest of the PV system can continue to generate electricity.grade
Protection of Conductors
Isolate damaged PV modules
仁爱版英语
Selecting Fu Links for PV String Protection
pm
current at maximum power
I
sc
:short-circuit current
Apply PV fu
to + and - Strings
No PV String
Fusing required PV Fu Selection Flow-Chart
Fu Rating for PV Applications Once it has been determined that maximum short-circuit current
([N-1]*I
sc
)exceeds continuous current rating of conductor, follow the recommendations of lecting the proper PV string fu.
Example 1: Solar Panel String Fusing文献翻译
I
sc
=5.37A
I
pm
=4.83A
Max System Voltage = 1000Vdc (max value of ries panels)
Conductor Size Formula = 1.56 * I
sc
=1.56 * 5.37 = 8.38A
Conduct Size = 14AWG or 2.5mm2=10.25A @ 80o C
N=4(4parallel Solar Panel Strings)
Array Max I
sc =(N-1) * I
sc
=(4-1) * 5.37 = 16.11A
Array Max I
光棍节由来sc
lookoveris greater than conductor withstand, therefore string fus are required
I n =1.56 x I
sc
(individual panel only) = 8.37A min fu rating
Select next higher std rating of 10A: PV-10A10F Fu lected will protect lected conductorusually怎么读
Min wire size: 14AWG or 2.5mm2=10.25A @ 80o C Module Description
Cell Type Polycrystalline Silicon
ability的形容词
Cell Size125mm2(5")
No of Cells and Connection72 in Series
Maximum System Voltage1,000Vdc
Electrical Data
Maximum Power Voltage (Vpm)34.6V
Open Circuit Voltage (Voc)43.1V
Maximum Power Current (Ipm) 4.83A
Short Circuit Current (Isc) 5.37A
Typical Solar Panel Specification Photovoltaic System Overcurrent Protection
