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Choose the Right Type of Solar Cable

May 14, 2020

solar cable

These solutions cover a full range of cable interconnections between solar panel and other components of photovoltaic systems.

In response to the growing need for energy and thanks to state subsidies, the renewable energy industry in general, and the solar energy industry in particular, have seen the development of new technologies capable of receiving energy from of the environment in order to be “naturally” redistributed to the local and national network.The solar cables are present on some of the largest solar power plants in world, including the 46 mW installation of Landmead by Belectric, the largest floating solar installation in Forrester and four SunEdison solar power plants with a total output of 60 mW . The complete solar cable solutions have also helped to bring to life the largest solar power plants in the entire world.

 

FULL PORTFOLIO OF SOLAR CABLES

Our solar cables are manufactured in accordance with British and international standards. These include TUV certified solar cables, covering a range of applications typical of photovoltaic rooftop installations and solar power plants, as well as providing interconnections between photovoltaic power generation systems, including solar panels. This range of rugged outdoor cables has been designed to withstand demanding environmental conditions as well as the degradation caused by exposure to ultraviolet light. We also supply a wide range of bare copper cables, low and medium voltage to connect the solar installation to substations and the electrical network.

 

EN 50618 SOLAR CABLES

ZW photovoltaic cables are in accordance with EN 50618. This standard replaces the approvals of PV1-F solar cables from the TÜV Rheinland group. Like TÜV certified cables, EN 50618 solar cables have been subject to a rigorous manufacturing and testing program to guarantee quality cables with an expected life of around 25 years. . We apply the same quality standards to all of our products.

 

SPECIALIZED TECHNICAL SUPPORT IN SOLAR CABLES

ZW Cables’ complete solar cable solutions cover a wide spectrum of projects ranging from the choice or design of the cable to its same day delivery or its production in very short time, logistics and testing activities, conducted on and off site. Our internal test laboratory specializing in cables, certified in accordance with ISO 17025 by UKAS, offers a whole range of technical expertise including personalized cable development as well as tests and checks in the event of failure. suspected.

 

SOLAR CABLE ACCESSORIES WITH TOOLS

To ensure optimal performance of your solar systems, consult us for our solar wire accessories, including connectors and specialized crimping tools for quick and faultless installation.

DC cables connect the modules together to create a string. (PV chain: the circuit in which PV Cables connect in series to create the specified output voltage. Source: IEC60634-7-712. Standard and connect multiple wires In parallel Can use a cable called “Solar” only (double insulation, UV and ozone protection, etc.) can be used in more detail. Solar cables used outside on the roof must be resistant to UV rays and protect against the action of ozone. They must be certified to work at temperatures from -20 ° C to 80 ° C. Temperature requirements must apply to all equipment used for installation.

The main DC power cable must be sized and connected according to the necessary criteria for safety and energy efficiency reasons:

1. Withstand 1.15 x open circuit voltage (insulation)

2. Adjust the cable capacity to suit DC and AC current (cable section) and ohmic loss due to voltage drop.

3. Use suitable connectors

 

Safety against incidents, incidents or short events

When multiple wires are connected in parallel, it is necessary to protect the conductor from overcurrent by using a fuse on the + and – terminals as described in IEC 60364-7-712.

These protective fuses are optional if the conductor has the size that can withstand the highest possible overcurrent. (Short circuit current) and if there are no more than four wires connected in parallel In this case, check that the module can withstand this current in the opposite direction. (The electricity that is forced through the module) without causing permanent damage.

The maximum current that is possible through a string conductor is determined by:

          Imax, string = 1.25 (n-1) Isc, STC

Where n is the number of strings in parallel and Isc, STC is the short-circuit current through the string, the STC standard test conditions for abbreviations in English. (Standard test conditions: 1,000 W / m², AM1.5, 25 ° C).

Therefore, the main DC current conductor must be sized for the maximum possible current provided by many strings together with PV modules (such as all the strings laid in parallel). The maximum current possible is given by:

Imax, array = 1.25 n Isc, STC

The cable section will be the standard maximum, close to the calculated value.

 

Cable section and OHMIC loss in DC parts:

Cross-sectional picture of the conductor of each string and the main conductor (After parallel recovery) must be so that the current flows through them at the highest energy points (In English, Maximum Power Point or MPP) doesn’t cause anything else to happen. The voltage drop is 2% of the normal voltage at the ends of these conductors.

Cable section (S) can be calculated from the following formula:

S = (ρxLxI) / (εxVA)

Or :

ρ is the resistivity of the cable in Ω.m. This depends on the material. It is 1.7 × 10-8 Ω.m for a copper cable.

L is the cable length in m

I is the current that the cable crosses at A

ε is the voltage drop in V

VA is the voltage from the cable in V

When a new photovoltaic installation is planned on an existing building or to be built, a stress analysis must be carried out.

                             

Example:

The 250 W PRO L3 monocrystalline modules have a nominal current of 8.37 A (MPP) and a nominal voltage of 29.88 V (UMPP). The open circuit voltage (U OC) is 37.82 V and the short circuit current (I SC) is 8.68 A.

If we make a string of 20 modules in series, the total nominal voltage is 597.6 V (20 x 29.88V) and that of the open circuit is 756.4 V (20 x 37.82 V)

So the DC conductors must have a minimum DC insulation of 1.15 x 756.4 = 869.86V

The section of the main DC conductor (in this case, string conductor) will therefore be calculated as follows:

1.25 x 8.68 A = 10.85 A, this is the maximum current of the array.

The total power supported by the cable will be:

8.37 A x 597.6 V = 5002 W

For this example, we will consider a maximum distance of 120 m to the inverter, so to limit losses to less than 2%, say 1%:

The voltage drop in the cable is 1% x 597.6 V = 6 V

Thus, the section of the cable should be, for a tinned copper conductor:

S = (1.7 × 10 (E-8) Ω.mx 120 mx 10.85 A) / (1% x 597.6 V) = 2.21 x 10 (E-5) / 6 = 3.68 x 10 (E-6) m²

So, you have to choose 4mm² of cable section.

 

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