Safety Risks and Solutions in PV Systems for Firefighters

White Paper Safety Risks and Solutions in PV Systems for Europe and APAC The purpose of this paper is to discuss the safety issues of PV systems for firefighters and outline how the SolarEdge system can mitigate these safety issues Shutdown functions in traditional inverters merely interrupt current flow and voltages remain dangerously high Automatic DC breakers located on the inverter in the cabinet cannot disconnect the voltage on the modules adding cost without decreasing the risk Rooftop array disconnect switches only terminate the flow of current from the roof to the inverter The modules on the roof their cabling and the cabling all the way to the inverter remain energized and dangerous while there is daylight PV module covering Spraying foam this approach has proven to be ineffective because the foam evaporates or slides off the modules before extinguishing the fire Covering the module with an opaque material this approach is not practical to implement and even dangerous as it requires the firefighters to climb onto the burning roof carrying heavy covering material and risking electrocution Firefighting Risk Electrocution Firefighters and other first responders called to a blaze commonly cut off power to the burning building as a safety precaution If the building has a PV installation however the PV modules continue to generate DC voltage even if the system is not actually connected to the AC grid In electrical systems extralow voltage SELV indicates a safe voltage below 120V Under these conditions there is a low risk of electrocution PV modules typically have an output voltage of 3060V and threefour connected modules are enough to generate more than 150V When connected in a string voltage in residential and commercial installations can reach 6001500V which can be dangerous to installers during system installation maintenance personnel during OM and first responders during an emergency Effective solution modulelevel shutdown SolarEdge offers a PV power harvesting system that consists of power optimizers connected to each module a PV inverter and modulelevel monitoring Additionally SolarEdge systems have a builtin SafeDC safety feature that minimizes safety risks When power optimizers are connected modules continue to operate only as long as a signal from the inverter is constantly renewed If there is no signal from the inverter or if the inverter is not operating SolarEdges SafeDC feature is designed to automatically shut down the DC current as well as voltage in module and string wires In safety mode the output voltage of each module equals 1V For example if firefighters disconnect a PV system from the Ineffective solutions electrical grid during daylight and the PV system consists of 10 modules per string the string voltage will decrease to 10VDC Since the maximum string length in a SolarEdge system is 50 the string voltage is limited to 50VDC safely below the risk level Even under single faults the solution has been certified to have SELV 120V voltages Modulelevel shutdown occurs automatically in any of these cases A building is disconnected from the electrical grid The inverter is turned off Power optimizer thermal sensors for each module detect the rising temperature threshold 85C Global Trends Increasing numbers of fire authorities insurance companies and electrical authorities are introducing new standards and regulations aimed at increasing PV safety and protecting personnel and property NEC 2014 2017 In the United States for example the National Electric Code NEC 2014 and the more recent NEC 2017 requires rapid shutdown of PV systems on buildings As part of this requirement DC voltage in circuits running more than a certain distance from the array to the inverter 10 feet for NEC 2014 one foot for NEC 2017 has to be lower than 30VDC within 30 seconds of rapid shutdown initiation NEC 2017 or 10 seconds NEC 2014 The SolarEdge solution complies with this requirement Published by the NFPA National Fire Protection Association the NEC code is voted on and approved by firefighters and code officials SolarEdge has also received a NRTL listing to UL 1741 CRD for PVRSS Photovoltaic Rapid Shutdown System This is now required for NEC 2017 compliance An additional example is the German application guide VDEARE 2100712 VDE compliance The German application guide VDEARE 2100712 requires among other things that after switching off the AC power supply first responders will not expose themselves to the risk of direct contact with DC cables which still carry a voltage greater than 120 volts DC SolarEdge P series power optimizers meet this requirement by the patented SafeDC function 1V safety voltage SolarEdge power optimizers allow automatic and failsafe reduction of DCvoltage to a safe voltage below 120VDC within the required time This function is integral to the system and therefore does not require any additional hardware or fire proof constructional measures leading to a reduction of installation costs SolarEdges conformity to the technical requirements in sections 71 and 74 of the application rule were confirmed by Primara see last page Conclusion The SolarEdge system with the integral SafeDC feature ensures complete safety for firefighters working with PV modules and eliminates the risk of electrocution The SolarEdge SafeDC feature is certified in Europe as a DC disconnect according to IECEN 609471 and 3 and to the safety standards VDE AR 2100712 and OEVE R111 SafeDCTM Voltage shutdown at the module level Power Optimizer Inverter Monitoring Platform Applicant SolarEdge Technologies 1 HaMada Street Herzliya 4673335 Israel Product type Disconnect device for PV generators Model Safe DC disconnect mechanism Rating Disconnection between a PV inverter and a PV generator Applied rules and standards In dependence on IEC 6094731999 Corr1999 A12001 Corr12001 A22005 in conjuction with IEC 6094712004 4th edition Lowvoltage switchgear and controlgear Part 3 Switches disconnectors switchdisconnectors and fusecombination units The safety concept of an aforementioned representative product corresponds at the time of this certificate to the valid safety specifications for the specified use Report no 13KFS10901 Certificate no 1616700 Date of issue 20161109 Andreas Aufmuth solaredgecom infosolaredgecom 052020V01ENG ROW