Solar Connectors play a crucial role in photovoltaic systems and have the potential to cause PV panel burnout. Photovoltaic connectors are integral components used to establish connections between solar panels, batteries, and junction boxes, enabling the creation of solar panel arrays. These connectors serve as the uniform and compatible power interface, facilitating ease of installation, accommodating high current capacity, and exhibiting robustness in extreme environmental conditions. Given the common use of solar panels in challenging settings, all system components must withstand harsh environmental factors like solar radiation, humidity, and dusty surroundings. Solar cell connectors come equipped with built-in UV protection, adhere to stringent wire gauge specifications, and feature excellent sealing capabilities.

Slightly different sizes for different connectors

Slightly different sizes for different connectors

The initial connector standard introduced for the photovoltaic industry was 2PfG1161 by TÜV Rheinland in 2004, followed by IEC 62852 in 2014. The current industry standard is IEC 62852:2014+A1 (2020). These international standards bring consistency and ensure the safety and reliability of products in end-use applications. In addition to international standards, various countries and regions have their own locally recognized industry standards, such as UL 6703 in North America, JET in Japan, and China’s GB/T 33765-2017 DC Connectors for Ground Mounted Photovoltaic Systems. These standards specify requirements for insulation strength, electrical gap, IP protection level, and safety performance of PV connectors, but they may not cover aspects related to connector form, structure, and core size.

Within the entire photovoltaic system, the DC side voltage can reach levels as high as 600-1000V. When the connections of photovoltaic module connectors become loose or have poor contact, there is a high risk of DC arcing. DC arcing leads to a significant increase in the contact’s temperature, generating sustained arcs at temperatures ranging from 1000 to 3000°C. This can result in the carbonization of surrounding components, potentially causing fuse failures, cable damage, and even equipment fires. Various factors can contribute to photovoltaic connector failures, with connector quality being the most significant factor, followed by issues related to the interconnection of different connector brands and improper installation practices. Connector misconnections can trigger DC-side arcing, subsequently leading to fires. Problems stemming from connector-related issues include increased contact resistance, connector overheating, reduced connector lifespan, connector burnout, string disconnections, junction box failures, component leaks, and other issues that disrupt system functionality, ultimately affecting power generation efficiency.

Solar Connectors

1. Compatibility of Different Brands of Photovoltaic Connectors

Ideally, Solar connectors of the same brand and type should be used for interconnection. Each inverter typically comes with a specific number of PV connectors, and it’s essential to ensure the use of matching connectors during installation. While components typically have cables of a certain length, standard installations do not require additional PV connectors. However, due to the increased size of components in recent years, some manufacturers now offer horizontal and vertical row installations to reduce costs, leading to shorter cable lengths in vertical rows. If horizontal row designs are needed, additional PV connectors may be necessary. Given the variety of connector brands in the market and the lack of matching connectors provided by component manufacturers, the best practice is to purchase the same brand of connectors as the components or to cut out the end-of-string connector and replace it with a matching one.

If interconnection is unavoidable, one group can be cut, and Solar connectors specifically designed for interconnection can be used. It is essential to verify the smoothness of insertion and extraction and conduct an air leakage test on interconnection connectors. Any products that fail this test should not be used for interconnection. Furthermore, use a multimeter to check the circuit’s functionality after interconnection. Solar Connector mismatches, poor contact, or water leakage are common causes of fire accidents. It’s generally not recommended to use connectors from different brands with each other due to variations in positive and negative tolerances between manufacturers.

2. O-Ring Seals and T-Ring Waterproof Performance

While problems related to O-ring seals and T-ring waterproof performance may not become evident immediately, they can pose a risk during the rainy season, especially in rain-soaked environments. High-voltage direct current can create a circuit with the Earth, resulting in electrical leakage and electrocution. It is imperative to choose connectors with proper waterproofing capabilities (e.g., IP67) and ensure that the photovoltaic cable matches the connector size. For example, the popular Stäubli MC4 connector comes in various size models. Selecting the correct size for your cable is crucial to prevent potential leakage accidents.

3. Prolonged Exposure of Photovoltaic Connectors and Cables to Humid Environments
It is commonly assumed that the conductive parts of photovoltaic cables and connectors are insulated from the external environment. While photovoltaic connectors are designed with waterproofing capabilities (e.g., IP67), this does not mean they can withstand long-term immersion in water. The IP67 rating refers to pre-installed photovoltaic connectors with wires submerged in water at a specific distance from the water surface for 30 minutes without performance degradation.

Most PV cables on the market can tolerate short-term exposure to water, such as brief drenching. However, if water accumulates for extended periods, issues may arise. For instance, burying photovoltaic cables in swampy areas can lead to breakdown, arcing, and combustion due to long-term water infiltration. Notably, PV cables run through PVC pipes are particularly susceptible to fires caused by accumulated water within the pipes. When using PVC pipes for cable routing, it’s advisable to position the pipe mouth downward or to introduce drainage holes at the lowest point to prevent water accumulation.

4. Cable Damage or Excessive Bending During Installation

Damage to the cable’s insulation, resulting from cable skin scratches, can lead to significant reductions in cable insulation and weather resistance. Excessive bending of cables, a common occurrence during construction, can pose several risks. Standard guidelines dictate that the minimum bending diameter must be greater than four times the cable’s diameter. For instance, a 4 square photovoltaic cable with a 6mm diameter should have a bending arc diameter of at least 24mm. Grounding at any point in the PV string circuit or the formation of bridge pathways can be complex and may result from several factors, including long-term cable soaking, extended PV connector cables, cable surface damage during construction, rodent damage, and lightning strikes.

5. Non-standardized Crimping of Photovoltaic Connectors

Non-standardized crimping of PV connectors primarily arises due to variations in field tools and limited operational experience. Poor crimping quality is typically associated with the bending of cable copper wires and incomplete crimping of copper wires into the cable insulation.
During the crimping process, attention should also be given to the stripping process, which has strict regulations regarding the number of copper wires to be cut during stripping. Excessive cutting of copper wires can affect crimping quality and lead to higher temperature rises. Installers should aim to use professional tools and provide field installers with the necessary training while establishing a sampling mechanism for quality control.

Rapid Shutdown Device For Solar PV Array Level 6-10 Strings 600V-1500V
In Summary:
Photovoltaic connectors are critical components in photovoltaic systems and require careful consideration. During product selection and construction, it is essential to focus on the following points:
1. Prioritize well-known domestic and international brands with proven, reliable product quality. Pre-testing of components is crucial, and each batch of materials should undergo testing.
2. Avoid mixing products from different manufacturers. If mixing is necessary, conduct connector intermating tests, including checks for contact resistance (less than 0.3 milliohms), waterproofing, and tensile strength.
3. Use professional wire strippers and crimping tools to ensure high-quality crimping. Proper training and quality control mechanisms are essential to achieve standardized crimping.
In conclusion, photovoltaic connectors are a pivotal aspect of photovoltaic systems that deserve meticulous attention. Adherence to best practices and a focus on quality and safety can prevent potential issues and enhance the overall reliability and performance of a photovoltaic system.