Solar Cable and Wiring Standards in India: DC, AC and BIS Compliance

With the growth of the solar industry, it is becoming necessary to have a functioning electrical infrastructure which has photovoltaic panels and products like wires and equipment for electricity distribution. While everyone is paying attention to solar panels, the choice of cables is important in order to ensure electrical safety and efficient operation of the facility.

For solar companies, EPC contractors, electrical engineers, and purchasing departments, choosing the right cable involves more than matching the voltage levels and measuring the size of a conductor. Cables should be suitable for application, resistant to external influences, and comply with Indian standards.

IS 17293:2020 is the principal standard connected with photovoltaic DC cables of not exceeding 1,500 DC volts of direct current. Another significant document is the Solar DC Cable and Fire Survival Cable (Quality Control) Order of 2023 that requires a Bureau of Indian Standards certification for every product mentioned therein.

Thus, understanding the specifications of current DC and AC standards as well as the requirements for certification will help prevent any problems associated with the procurement process for everybody involved in solar power projects.

1. Why Solar Cable Selection Matters

Solar cables are used for applications where it is important for cables to function in strenuous conditions, especially outdoor locations. The cables that link the solar panels together are subject to different factors such as the effects of UV rays, hot weather, humidity, and rainfall, in addition to some mechanical challenges. If the insulation or sheath materials are not well suited for the application, issues may arise in the future because degraded insulation can cause problems with electrical conduction.

It is crucial to choose the cables properly since the energy efficiency of energy transmission will be low if the current intensity and other characteristics are not sufficient, which will lead to voltage drop and energy loss. Not only will improper connections or connectors create issues with overheating, but they can also cause damage to the equipment.

When large installations of solar panels are being set up, the cable quotation should take into account voltage, power, material type, insulation technology, installation method and the environment.

2. Solar DC Cable Standard in India: IS 17293:2020

IS 17293:2020 applies to electric cables that have a rated voltage of about 1,500 volts DC, thereby providing the essential requirements for the cables used in the DC side of the photovoltaic system. This type of cable is used to transfer electrical energy from solar panels to inverters through proper DC connections, as opposed to standard electric cables, which are used in many indoor applications. Photovoltaic cables must be able to withstand the conditions of long-term outdoor exposure as well as the operational conditions of photovoltaic devices. The standard outlines the construction and dimensions of the cable, electrical characteristics, and tests needed for insulation or sheath.

The important factors that should be taken into account are as follows:

•      Voltage Rating: The cable must have the right voltage level for the PV system.

•      Material of Conductor: The material which is used for making the conductor will also affect its electrical properties.

•      Insulation and Sheath: Insulation and sheath are supposed to protect the cable from electrical and environmental hazards.

•      Temperature Efficiency: The cable is supposed to operate within the limits of temperature.

•      UV-Exposure and Weather Resistance: This is especially important for cables which are permanently exposed to sunlight or used outdoors.

•      Mechanical Properties: The cable is supposed to have enough durability so that it can withstand exploitation, routing, and installation.

•      Identification and Traceability: The process of identification is important to make sure that the product is consistent with its procurement.

According to BIS documentation, a temperature of 90 deg C is said to be the normal temperature for cables as per IS 17293, depending on certain conditions under which the particular cable can operate at much higher temperatures. All those who want to buy cable should always refer to the concerned standard and relevant certified documents to know the limits.

In the case of engineering contractors, having just the phrase 1.5 kV solar cable is not sufficient. The specification should include the standards and specifications of the cable along with the environmental parameters.

3. BIS Certification for Solar Cables

The Solar DC Cable and Fire Survival Cable (Quality Control) order of 2023 stipulates the conformity criteria for the products mentioned in the order.

For solar DC cables, the specified standard is IS 17293:2020. The concerned products need to be compliant with the corresponding Indian Standard and must bear the BIS Standard Mark through the necessary BIS license in compliance with the order.

Thus, certification is an important criterion in supplier selection.

A test report and a BIS license serve different functions. A test report describes the results of the prescribed tests carried on a sample. A BIS license permits the manufacturer to use the Standard Mark for the product as per the conditions of the license.

Thus, applying the test report solely instead of the BIS license is not correct in situations where compulsory certification is due.

Before placing the order, the procurement staff should check whether the license of the manufacturer is valid and whether the specific type of the cable is covered by the license.

It is especially relevant with respect to cases when there is a need to buy the products from the distributors or different manufacturers, thus creating an opportunity for changes in product documentation.

4. Solar AC Cable Standards: What Buyers Need to Know

AC cables transfer electric power from the inverter to the load, with their specifications depending on voltage level, conductor design, insulating material, and conditions of installation.

Apart from that, these cables are not subject to a common standard for solar technologies like photovoltaic (PV) direct current (DC) cables.

Specifically, IS 7098 (Part 1) applies to cross-linked poly-ethylene (XLPE) insulated, PVC sheathed conductors for voltage not exceeding 1,100 V.

IS 7098 (Part 2) specifies the use of cables whose working voltages range between 3,3 kV and 33 kV.

The respective standards will apply depending on what part of solar treatment system they are part of.

In a utility-scale project, low-voltage inverter output cables and medium-voltage collection or evacuation cables may require different specifications.

A cable suitable for an AC circuit should not automatically be substituted for a photovoltaic DC cable simply because its voltage rating appears adequate.

5. Solar Cable Sizing and Electrical Losses

Cable sizing is an important part of solar system design. The conductor must safely carry the expected current while keeping voltage drop and electrical losses within the project's design limits.

For a simple DC circuit, voltage drop can be calculated using:

For a simple DC circuit, voltage drop can be calculated using:

Here, I represents the current and R represents the total resistance of the outgoing and return conductors.

Voltage drop as a percentage of system voltage is:

However, final cable sizing requires more than this calculation. Engineers must consider conductor resistance at operating temperature, current-carrying capacity, cable grouping, ambient temperature, installation method, and short-circuit withstand.

For AC circuits, power factor and cable reactance may also need to be considered.

An undersized cable can increase losses and operating temperatures. Conversely, excessive conductor sizing raises material and installation costs. The engineering objective is to identify the cable size that meets electrical, safety, and regulatory requirements without unnecessary expenditure.

6. Solar Cable Procurement: A Checklist for EPCs

Cable compliance should always be methodically ensured before shipment to installation locations. Adopting a stringent procurement procedure is one way to eradicate specification mismatches and eliminate issues relating to certifications.

Prior to pursuing a purchase order, purchasers must validate applicable Indian Standards, voltage rating, size of the conductor, type of material, type of insulation, type of sheath, as well as operational conditions. In the case of regulated products, it is recommended that the procurement specification is augmented with pertinent requirements related to the BIS certification.

When qualifying a supplier, the license of the manufacturer and the certified product scope should be verified. Data sheets and details of tests must be compared against the demands of the particular project.

When goods are delivered, the check-point teams must confirm that the cables comply with the standards and regulations regarding markings, drum stickers, dimensions, identification of the batch, etc. Resolving discrepancies between a certified product and the supplied unit must take place even before installation work starts.

The quality of the installation is equally important. Proper routing, minimum bending radius , mechanical protection, termination practices, and compatibility of connectors of cables are responsible for the correct functioning of compliant cables.

7. Common Cable Procurement Mistakes

In the procurement process, many mistakes are made, exposing solar projects to unnecessary risks.

When only focusing on the prices of cables, one might fail to notice the differences in cable construction, material quality and certification.

There is a danger in equating voltage rating with certification compliance because one can end up buying a cable that is unsuitable for photovoltaic DC use.

By accepting the test report without checking the BIS license, one can face serious compliance problems if it is an area where it is mandatory to obtain certification.

The current capacity of a cable, as well as its lifespan, can be affected by not taking installation conditions into account.

The same specifications used to make all connections do not recognize the differences between the various types of DC strings, low voltage AC connections, and MV evacuation systems.

These mistakes can be avoided by using accurate technical specifications, confirming the quality of the supplier, and using the right inspection throughout the procurement process.

Conclusion

It is important to understand the technical specifications, standards, and certification requirements when selecting cables for solar use in India. In this regard, IS 17293:2020 serves as the Indian Standard for photovoltaic DC cables meant for use in voltages up to 1,500V DC, whereas the specifications for the AC cable will depend on factors such as voltage, construction and place of installation of the cable. Cables which are covered under the Solar DC Cable and Fire Survival Cable (Quality Control) Order, 2023 will require the procurement of cables to be BIS certified.

For the solar developers, taking steps to determine requirements of cables earlier in the design phase and validating suppliers before placement of order will matter most. The development of cables is suggested to be regarded as engineered components instead of commoditized goods in order to improve the reliability of the power plant and manage costs more effectively.

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