The past, present and future of photovoltaic connectors

As the lifeline of the system, photovoltaic connectors run throughout the project and are an important carrier to ensure the stable transmission of power generated from the components to the inverter and user end. According to different application scenarios, the DC side can be mainly divided into line-end connectors (such as components), branch connectors (engineering sites) and board-end connectors (such as inverters).

As a key component, connectors’ low contact resistance and long-term reliability can ensure efficient and safe operation of power stations. On the contrary, continuously rising contact resistance will greatly increase the safety risk of the project, and may even lead to serious fire accidents. From 2010 to 2017, 27% of the 58 photovoltaic fires in the UK were caused by connectors; from 1995 to 2012, 24% of the 180 photovoltaic fires in Germany were also attributed to connector failure*.

This article focuses on connector standard updates and product iterations, aiming to give the industry a more macro understanding of the history of connectors and look forward to future development trends.

Standard updates

Ulrika Frank, President of the International Organization for Standardization (ISO), said in her 2022 New Year's message, "Standards are obviously important tools for solving many problems. From governments to businesses to civil society, standards allow people around the world to speak a common language and become international benchmarks for quality, safety and, most importantly, trust."

The first connector standard in the photovoltaic industry was 2PfG 1161 launched by TÜV Rheinland in 2004. With the continuous innovation of connector products and the development of market demand, it has mainly gone through DIN V VDE V 0126-3 (2006), EN 50521 (2008) and EN 50521: 2008+A1 (2012), eventually forming IEC 62852 in 2014. Currently, the standard applicable to the industry is IEC 62852:2014+A1 (2020). International standards bring norms to the industry and ensure the safety and reliability of products in terminal applications.

In addition to international standards, various countries or regions also have locally recognized industry standards, such as UL 6703 in North America, Japan's JET, China's "GB/T 33765-2017 DC Connectors for Ground Photovoltaic Systems", etc.

Connector iteration

During the life cycle of the photovoltaic system (>25 years), the connector as an energy transmitter must have constant and low contact resistance to ensure low power loss, otherwise it will cause invisible loss of power generation. At the same time, connectors must also adapt to various harsh environments, such as wind and rain, scorching sun, salt spray and extreme temperature changes.

Before 1996, photovoltaic cables were commonly connected using screw terminals or splice connections, but this method could not meet environmental and market demands. In 1996, in response to the customized demands of end customers, Stäubli launched a new plug-in connector - the world's first photovoltaic connector MC3 - based on the core electrical connection technology MULTILAM. The main body of MC3 is made of TPE material (thermoplastic elastomer) and is physically connected through friction fit.

In 2002, Stäubli launched the MC4 connector, which truly achieved "plug and play". The insulation material used hard materials (PC/PA) and was designed to be easier to assemble and install on site. After MC4 was launched, it was quickly recognized by the market and gradually became an industry benchmark. In order to adapt to the increase in the voltage level of photovoltaic systems, MC4-Evo 2 has also emerged. The contact resistance is less than 0.2 milliohms and the maximum carrying current is 70A, which fully meets the needs of 1500V photovoltaic systems and large-size component markets.

At the same time, after passing the TÜV Rheinland test, the MC4 series connector is the first photovoltaic connector suitable for high temperature (IEC TS 63126:2020 level 2) and high altitude (MC4, 4000 meters; MC4-Evo 2, 5000 meters).

future trends

Whether now or in the future, fundamentally speaking, the development of photovoltaic connectors should be committed to improving product reliability and consistency and reducing energy loss, so as to contribute to the reduction of LCOE throughout the life cycle of photovoltaic power stations.

Shen Qianping, product and technical service manager of Stäubli (Hangzhou) Electrical Connector Division, believes that future photovoltaic connectors need to keep up with the technological development of photovoltaic modules (such as higher voltage and higher current), technological upgrades of photovoltaic systems (such as higher system voltage and non-photovoltaic cables), various special environmental scenario applications (such as sea floating power stations, agricultural and livestock power stations, desert power stations and BiPV) and intelligent operation and maintenance.