# US 2014/0191589 A1 · Safety device for a photovoltaic system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191589 A1 - Document ID: US20140191589A1 - Status: Published application - Kind: A1 - Application number: 14/205,606 - Filed: 2014-03-12 - Published: 2014-07-10 - Earliest claimed: 2011-09-12 - Assignees: SMA Solar Technology AG - Applicants: SMA Solar Technology AG - Inventors: Jens Friebe; Sebastian Bieniek - Web page: https://patentgrep.com/patent/US20140191589A1 ## CPC - H01H 9/54: Circuit arrangements not adapted to a particular application of the switching device and for which no provision exists elsewhere - H02H 3/08: responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) - H02H 3/20: responsive to excess voltage - H10F 77/955: {for photovoltaic devices} - Y02E 10/50: Photovoltaic [PV] energy - H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00) - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract The disclosure relates to a safety device for a photovoltaic system for feeding into a power supply system, that includes at least one input for connection to a PV generator, at least one output for connection to an inverter, and a switching element for de-energizing the at least one output. The safety device includes an evaluating unit configured to switch the switching element based on a low-frequency signal at the at least one output. The disclosure also relates to a method for operating such a safety device. ## Claims ### Claim 1 A safety device for a photovoltaic system for feeding into a power supply system, the safety device comprising: at least one input for connection to a PV generator; at least one output for connection to an inverter; a switching element for de-energizing the at least one output; and an evaluating unit configured to switch the switching element based on a low-frequency signal present at the at least one output. ### Claim 2 (depends on 1) The safety device as claimed in claim 1, wherein the evaluating unit is configured to measure the low-frequency signal as a voltage signal. ### Claim 3 (depends on 2) The safety device as claimed in claim 2, further comprising a terminal for connection to an earth potential, wherein the evaluating unit is configured to determine the voltage signal between the at least one output and the earth potential. ### Claim 4 (depends on 1) The safety device as claimed in claim 1, wherein the evaluating unit is configured to measure the low-frequency signal as a current signal. ### Claim 5 (depends on 4) The safety device as claimed in claim 4, further comprising a current measuring device connected to the evaluating unit, wherein the evaluating is configured to determine a current flowing via the at least one output as current signal. ### Claim 6 (depends on 1) The safety device as claimed in claim 1, wherein the low-frequency signal comprises a frequency which corresponds to an integral multiple of the system frequency in the power supply system. ### Claim 7 (depends on 6) The safety device as claimed in claim 6, wherein the low-frequency signal comprises a frequency which corresponds at least to one and at most to 10-times the system frequency in the power supply system. ### Claim 8 (depends on 1) The safety device as claimed in claim 1, comprising a a band-pass filter coupled between the evaluating unit and an output of the at least one output. ### Claim 9 (depends on 1) The safety device as claimed in claim 1, further comprising an amplifier configured to amplify the low-frequency signal. ### Claim 10 (depends on 1) The safety device as claimed in claim 1, wherein the safety device is configured to connect the at least one input to the at least one output at a signal level above a first threshold value. ### Claim 11 (depends on 1) The safety device as claimed in claim 1, wherein the safety device de-energize the at least one output at a signal level below a second threshold value. ### Claim 12 (depends on 10) The safety device as claimed in claim 10, wherein the second threshold value is less than the first threshold value. ### Claim 13 (depends on 1) The safety device as claimed in claim 1, wherein a de-energizing of the at least one output takes place via a short circuit of the inputs of the safety device. ### Claim 14 (depends on 1) The safety device as claimed in claim 1, wherein a de-energizing of the at least one output takes place via a separating of the connection of the at least one input and the at least one output. ### Claim 15 (depends on 1) The safety device as claimed in claim 1, wherein the switching element comprises means for extinguishing an arc. ### Claim 16 (depends on 1) The safety device as claimed in claim 1, further comprising a central detection unit with the evaluating unit and at least one switching unit with the switching element, wherein the central detection unit and the at least one switching unit reside in separate housings. ### Claim 17 A method for operating a safety device for a photovoltaic system for feeding into a power supply system, the safety device comprising at least one input for connection to a PV generator and at least one output for connection to an inverter, and comprising a switching element for de-energizing the at least one output, comprising: determining a level of a low-frequency signal at the at least one output; connecting the at least one output to the at least one input, if the level of the low-frequency signal is above a first threshold value; and de-energizing the at least one output if the level of the low-frequency signal is below a second threshold value. ### Claim 18 (depends on 17) The method as claimed in claim 17, wherein the level of the low-frequency signal is determined at a frequency which corresponds to an integral multiple of the system frequency in the power supply system. ### Claim 19 (depends on 18) The method as claimed in claim 18, wherein the low-frequency signal has a frequency which corresponds at least to one and at most to 10-times the system frequency in the power supply system.