It is recognized that throughout the 25-year lifetime of a PV power plant, there is always a danger inherent in photovoltaics of injury from electrical shock, not just during construction, but during routine maintenance, inspection of a technical problem, or responding to a fire. PV modules produce DC voltage when exposed to light even when disconnected from the inverter. Touching the PV arrays or the DC cables will shock technicians or emergency responders. On October 25, 2010, NECA (Australia) reported that two apprentices received electrical shocks during installation of solar panels on domestic rooftops caused by accidentally touching a live DC cable. Similar accidents have been reported worldwide.
To reduce the likelihood of electric shock in jury to inspectors, maintenance personnel, or emergency responders, countries and standards groups are drafting new requirements and standards to protect people's safety.
VDE, the European Association for Electrical, Electronic & Information Technologies, has issued draft standard VDE-AR-E 2100 712 that requires additional measures and equipment to improve the safety of DC components in the PV system.
These new standards add to the minimum requirements that apply to the design and construction of PV power systems located inside or on the outside of buildings. Specifically, the new rules require such measures as affixing warning labels in dangerous areas and providing general information about the project, including layout information identifying the location of the DC cable and the configuration of the project in the building, in order to help technicians and emergency responders avoid dangerous areas.
The new standards also require the design to meet additional safety regulations. For example, a DC cable installed inside a building must meet certain fire resistance criteria, and the DC cable must be accessible only to personnel with special tools and backup assistance. DC cables installed outside the building must be located in such a way as to prevent exposure to dangerous voltage.
Most importantly, the new rules require adoption of new technical measures in the facilities and capabilities of PV systems. PV generators/modules must have shut-off, isolation, and short-circuit functions at the single module, module strings, or system level to protect the safety of technicians during inspection, maintenance, or emergency fire response.
The new standards encourage system developers, component suppliers, and module manufacturers to commit to upgrading their products and adding new functionality to meet requirements, which should lead to an important new trend in the industry.
ET Solar, the worlds leading provider of integrated photovoltaic solutions, and Convertergy, a leading global electronics product development company, have collaborated to develop a revolutionary new product called Smart Module that combines monitoring, shutdown, and short-circuit functions in a single module. Smart Module goes well beyond the new requirements for shutdown, isolation, and short-circuit functions by providing cost-effective monitoring capabilities that enable installation owners and technicians to make quick and accurate maintenance decisions. The 1st generation Smart Module replaces the conventional diode with an integrated intelligent chip and integrates these critical functions:
Firstly, Smart Module provides real-time monitoring of parameters such as temperature, real-time peak power, daily and total power output, current, etc., with data uploaded to a database for viewing on a dedicated website. With this data, owners can not only monitor current operation but also analyze the optimal maintenance cycle of the system in order to anticipate and avoid potential problems. The Web platform will encode each module and provide a user-friendly layout location diagram so that if a problem does occur, technicians can locate the faulty module quickly and accurately. Component topologies can be configured to display the true structure of the power plant. With the order of the modules on the display matching the actual location in the plant, personnel can easily obtain relevant data from the real-time operation monitoring platform. Based on the information in the display, the technician can quickly locate the module. In this case, field tests will reveal that the abnormal power output is due to a damaged diode in the module. In less than half an hour, maintenance personnel can replace the faulty module.
Secondly, Smart Module is capable of organizing a communications network. In the past, it has been necessary for a technician to manually build a telecom network, but with Smart Module, once panels are installed and active, junction boxes will automatically communicate with each other in an internal network using an international telecommunications protocol. Through the network, panel information will be collected quickly and reliably and uploaded to the cloud server via Wi-Fi or GSM.
The biggest innovation of Smart Module is its ability to satisfy the new rule requiring a shutdown/short-circuit function. The ET Solar Smart Module is able to do self-testing during its monitoring of daily system operation. If it detects a high operating temperature or a current exceeding the safety standard, Smart Module will shut down the module to protect the panel and the system. For example, a loose connection in the junction box can cause an electric arc with a surge in voltage which can damage the diode and cause high temperatures and perhaps a fire. If the situation is not discovered quickly and the generator immediately shut down, the entire system may be damaged and there is danger of a fire that could destroy the entire building. The ET Solar Smart Module will detect the arc in less than a millisecond, shut down the module immediately, report to the cloud server database, and display a warning on the Web platform. The panel will be placed on standby until a new instruction is received. In standby mode the affected module will be isolated and will not affect other modules, even those in the same string, until the situation is corrected. This is an innovation novel to Smart Module, designed to limit loss when a partial fault occurs.
Thus, Smart Module exceeds the new shutdown, isolation, and short-circuit requirements by providing critical monitoring and hazard-detection functions. From a technological perspective, Smart Module limits possible power loss due to a faulty component by shutting down the affected module. From the perspective of system owners and technicians, Smart Module provides an efficient and user-friendly means of rapidly detecting and limiting system problems, permitting a more ideal maintenance plan.
