Bentek Solar reports it has developed and introduced the ‘PV 101 MDSS’ as a cost-effective Multiple Disconnect Safety System (MDSS), which is designed to provide safety and code compliance for PV installations in the US under National Electrical Code (NEC) 2011 rules.
Multiple sources of power are much less common in AC applications. As a result, PV installations contain hazards that many electricians and maintenance personnel are not accustomed to. Contact with a live fuse that has 600 or 1000V of electricity present may result in death. To help prevent this, National Electrical Code (NEC) 2011 690.16 states that, “an external disconnect must be installed within the line of sight of the inverter fuses or at a distance not greater than 50 feet from the inverter fuses.” However, not all states follow this NEC rule. This should be of great concern not only for the installers but also for the operations and maintenance (O&M) organization that will need to maintain the PV system for years to come.
The MDSS contains a bank of load-break disconnects in a compact, free-standing cabinet. Typically, the MDSS is installed next to the inverter and provides the safety and arc flash reduction that is needed in all photovoltaic (PV) systems, solving a critical safety issue that is commonly overlooked. The MDSS provides code-compliant fuse isolation that inverters do not. This allows fuses in the inverter to be removed safely.
Commercial and utility-scale PV power plants.
Bentek Solar’s MDSS with optional zone current monitoring is optimized to work with most inverters at both 600 and 1000VDC. The number of inputs and ampacity of the load-break disconnects in the MDSS are matched to the number and ampacity of the internal inverter fuses. This ensures that when the MDSS arrives at the project site, it is simple to install by eliminating extra racking, conduit and expensive labor that is required with traditional individual knife blade disconnects, saving up to 30 percent in total cost. The installer typically runs the cables up through the bottom of the MDSS and connects one cable to each input and one cable to each output. Each output cable then runs to an inverter fuse. For example, if the inverter has eight internal fuses that are 400A each, the MDSS would contain eight 400A load-break disconnects, with each disconnect connecting to an inverter fuse
October 2012 onwards for the US market.