Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62C—FIRE-FIGHTING
  • A62C3/00—Fire prevention, containment or extinguishing specially adapted for particular objects or places
  • A62C3/16—Fire prevention, containment or extinguishing specially adapted for particular objects or places in electrical installations, e.g. cableways
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62C—FIRE-FIGHTING
  • A62C99/00—Subject matter not provided for in other groups of this subclass
  • A62C99/009—Methods or equipment not provided for in groups A62C99/0009 - A62C99/0081
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/02016—Circuit arrangements of general character for the devices
  • H01L31/02019—Circuit arrangements of general character for the devices for devices characterised by at least one potential jump barrier or surface barrier
  • H01L31/02021—Circuit arrangements of general character for the devices for devices characterised by at least one potential jump barrier or surface barrier for solar cells
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
  • A62B17/00—Protective clothing affording protection against heat or harmful chemical agents or for use at high altitudes
  • A62B17/003—Fire-resistant or fire-fighters' clothes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy

Definitions

• the present invention belongs to the field of processes for fire extinguishing of photovoltaic power plants, specifically belonging to the field of electronic devices for minimizing dangerous voltage contact between the fire extinguishing system and the photovoltaic power plant on fire.
• the technical problem is creation of such a process for a systematic reduction and control of dangerous voltage contact, which would enable a reduction of the dangerous voltage contact for a fireman through a water jet at extinguishing photovoltaic power plants or photovoltaic panels.
• the problem solved by the present invention is also creating an electronic device for the reduction and control of the dangerous voltage contact on the basis of limited current of panels by levelling the potential of the entire fire extinguishing system of Fig.1 , which comprises fire-fighting devices, tools, motor pumps 6a, machines, ladders, fire - fighting water cannons fire-extinguishers, fire tank trucks 6, fire hydrants 9, as well as the firemen involved in fire-fighting.
• the aim of the invention as set is also a solution for solving grounding of the entire fire-fighting system, including the fireman, to achieve reliable levelling of potential of a fireman or a group of firemen.
• the problem of extinguishing fires at photovoltaic power plants lies in that there can arise a dangerous voltage contact or electric shock for the fireman.
• the Fire Fighting Association regulation states that the resistance of the water jet - the extinguishing media - must be sufficiently high and that the voltage-drop between the photovoltaic PV module and the fire-fighting nozzle is such that the dangerous voltage contact between the fire-fighting nozzle and the ground is lower than 120 V DC.
• DC voltage of 120V is considered harmless and is allowed according to the regulations in force, whereby it is assumed that water used for fire extinguishing shows a conductivity lower than 2500 pScm-1 and that the extinguishing of fire ensues with one nozzle of prescribed type with prescribed water pressure.
• the distance should be greater or firemen must abandon fire extinguishing as the conditions are unpredictable.
• the total panel voltage can reach several thousand volts up to a breakdown voltage of the module to ground- housing, which at some manufacturers amounts to about 8000V. Because fire- trucks present a capacity in relation to the ground and despite the low electric current on the cistern, the electric charge can still build up, which can then during extinguishing the fire instantly emanate through the contact of a fireman or a bystander. Also lower voltages can cause an exaggerated reaction of an individual, which can present a life hazard both indirectly or even directly.
• the standard fireman's equipment does not usually offer satisfactory protection of a fireman in the case of electric breakdown, which implies that we must prevent electric breakdown or current penetrating the protective clothing.
• the thickness of the non-conducting clothing is in proportion with the voltage, which can amount up to 8000V.
• This type of equipment is too expensive and too rigid to wear.
• Photovoltaic modules of PV 16 emit a direct current of constant value which depends on the lighting. These are the so-called current generators producing a constant current unlike voltage generators emitting a constant voltage regardless of the load. Existing modules emit a current of I app. 8-9 A at full sunlight.
• the modules are connected to a series of so-called PV panels. The panels can have from 800V to 1000V of exit voltage.
• the characteristics of the U-l diagram show that an individual module has at least 5 ⁇ of inner electric resistance RM or more.
• the internal resistance of panels RP is the total sum of all internal resistances of RM modules. As shown in Fig. 2, the current can flow from one electric pole of the current generator through the resistance of the modules RM, through electric resistance of the jet RC at one or several nozzles, water cannons or another fire extinguishing device through extinguishing media to the grounding devices through ground resistance, conductive resistance of the Rss contact to the other pole. Dangerous voltage contact can occur from 0 - 800V at the nozzle, cannon or fire extinguisher. It is essential that the panels produce a current of limited power, which cannot be switched off, but can be drawn off without significant problems, because it is not too great.
• the dangerous voltage contact reduces.
• the current can be stopped by interrupting the water jet of the fire extinguishing medium.
• the system according to the invention allows direct contact with the panel, which also enables extinguishing with chemical foam as chemical foam is conductive and fire extinguishing with foam has significant advantages. Until now, extinguishing with foam has not been allowed in such cases because firemen have not been sufficiently protected.
• the essential feature of the process and device for safe fire extinguishing of photovoltaic power plants according to the invention lies in a systematic reduction of the dangerous voltage contact by levelling out the potential of the entire fire extinguishing system, which includes fire extinguishing devices, tools, motor pumps, ladders, water cannons, fire extinguishers, tank trucks, hydrants and firemen involved in fire extinguishing.
• the entire fire-fighting system including firemen wearing a single layer or a multiple-layer Faraday cage, which can be occupied by a single or several firemen, there can also be achieved stable levelling out of the potential on a fireman or a group of firemen.
• FIG. 1 Block diagram of the grounding of the fire extinguishing system according to the invention
• Fig. 1 a Block diagram of the pipe and automatic stop valve
• Fig. 3 Diagram of the electronic circuit for the termination of the dangerous voltage contact
• FIG. 4 Diagram of the operation of the levelling system of the fireman's potential Fig. 4a Detail A - A
• all points of the fire extinguishing system including fire extinguishing devices, tools, motor pumps, machines, ladders, water cannons, tank trucks 6, hydrants 9 and firemen, are connected to grounding points 2, 3, 4, 5, 8 and point PE10 of the measuring signalling device 10 according to the invention, which includes an antenna to transmit signals, light signalization, sound signalization, the control signal of Fig. 1 for propulsion 7a of valve 7 to turn off water supply or extinguishing media to the nozzles 1 , 1a, 1 b.
• the system enables reduction of the dangerous voltage contact when extinguishing fires at photovoltaic power plants 16 and control of the dangerous voltage contact on the basis of limited panel current.
• the substitute electric diagram of Fig. 2 displays the electric parameters of the system, which include the photovoltaic power plant or panels, parameters of the fire extinguishing equipment and material, the measuring signalling device 10 and signalling elements for notifications.
• the substitute diagram of the solar panel is composed of a series of resistances RM, which represent the internal resistance of the module and of the current generator, which conveys current IM app. the size of 8A. In series with the current generator l M , there is the resistance of contact Rss of the panel with the conductive housing of the grounding structure.
• the difference between the protection system applied in electrical engineering at low-voltage installations and the proposed invention lies in that in electrical engineering it is possible to automatically turn off the dangerous circuit, whereas with solar panels this is not possible.
• the voltage generators can produce such currents that can easily destroy the fuses and thereby turn off the dangerous currents and contact voltage.
• the current cannot destroy a fuse, because in the case of a short circuit, the current does not increase. Therefore, the principle of protection applied in electrical engineering is not applicable in this case.
• Present invention is based on the fact that the circuit of photovoltaic panels is relatively small and stable. In the case of a fire, the current enters the ground through grounding or, in other words, the voltage contact is reduced to permitted values.
• the time span of the water supply to turn off is defined in the measuring signalling device 10 depending on voltage, however, the combined time for the operation of the automatic break mode of the system and fire extinguishing media should be less than 0.4 s, which corresponds even to voltage up to 240 V.
• the measuring signalling device 10 through a microprocessor, which measures the voltage contact, controls the two electronic switches so as to stimulate virtual zero.
• the electronic switches are through diodes connected in parallel charged to the positive or negative poles of the solar panels.
• the electronic switches release current Ik of the opposite polarity, but of the same amplitude as loz to the joint grounding point PE10; that is current, which flows on the panels, when spurting water on the panel.
• Fig.3 clearly shows that the panels are connected with grounding in the middle.
• the second contact is created by the water jet, which through grounding resistance Ro and resistances Rci , Rc2 and Rc3 of the jets completes the circuit for the current loz-
• the microprocessor ⁇ measures the voltage between points PE10 and NE10 and in accordance with this voltage turns on the electronic switch and allows the current Ik to flow.
• the current Ik is of the same amplitude as l 0 z > but of opposite polarity. This makes the total combined voltage at the common grounding point 0V. Essentially, it releases a current of appropriate amplitude, which causes a drop of the voltage of opposite polarity on the grounding resistance Ro. In this manner, the drop of voltage at Ro equals zero, because the sum of all currents equals zero.
• Many direct contacts, short circuits will automatically annul through the grounding, and have no dangerous voltage contact as a result.
• the diodes prevent the contact of PV panels among themselves.
• Fig. 1 schematically shows the grounding of a fire extinguishing system and attachment to point PE10 on the signalling measuring device 10.
• Point NE 10 is connected to the grounding probes 11 , which are nailed to the ground outside the grounding systems connected to point ⁇
• Point NEKJ is attached to the neutral grounding outside the potential grounding area of the burning building.
• grounding equipment prescribed in electrical engineering of metal wires, braids, bands, pipes, is used.
• Two or more connective wires are applied, which are attached to various grounding systems in the direct vicinity of the burning building or at least each to its own lightning conductor to the ground in order to ensure that there occurs no accidental breakdown of grounding.
• Each connective wire should have its own path.
• the more connective wires used and attached to various grounding systems the lower the combined grounding resistance Ro. This reduces the dangerous voltage contact on the nozzle, the fire extinguishing systems, and on the fireman to the allowed voltage, which is less than 120V.
• FIG. 4 Levelling out of the potential of the fireman either in full with the use of partial or complete Faraday cage, grounded or ungrounded, is shown in Fig. 4.
• An additional levelling out of potential of parts of personal equipment and fireman's clothing is performed by placing the same in a partially or completely closed off Faraday cage 17a.
• Faraday cage 17a There can be several cages, also one within the other. They come in different sizes, from sizes that fit several firemen in the cage 17 to the individual size.
• Also on a fireman Faraday cages can be mounted over the clothing, in the clothing or under the same.
• the outer Faraday cage f1 is the toughest to sustain current, which can appear.
• Faraday cages are additionally strengthened on the limbs, head - helmet, because of the expectancy of stronger currents at these locations.
• Faraday cages f2, f3, f4... are made of increasingly thinner electrically conductive materials to foils or fine wires.
• Fig. 4a describes a detail of the composition of a Faraday cage, which is made so that between cages f1 and f2 there is insulation i1 , between cages f2 and f3 there is insulation i2 and between cages f3 and f4 there is installed insulation i3.
• the Faraday cages are connected at one point as shown in Fig. 4.
• the layers can be insulated against heat and electricity. Possible electric charge moves from the inside out because of electricity laws, and in this manner electric shock is prevented, because there are no potential differences or differences in voltage on a fireman.
• Additional levelling out of the potential of firemen or the equipment is realized in the joint point, where all layers are connected and grounded through point PE of the OMNS device 15, connected to point PE 1C ) of the device 10.
• Higher safety is achieved by grounding as the dangerous voltage is drawn off continuously to the ground. This is significantly important for inner fire incursion or working directly on the panels on the roof.
• the entire equipment used by firemen has to be attached to the joint electric point of a fireman of additional levelling out of potential.
• Firemen can use a personal signalling device OMSN 15, which signals dangerous voltage contact and also receives the signal to turn off fire extinguishing media and grounding wire attached to a drum 15a. The wire is attached between the fireman, the device and point PE-
• OMSN 15 has the following functions: it warns firemen of the dangerous voltage contact and through reception enables shutting down of fire extinguishing media on a nozzle, if the same has a built-in automatic valve system.
• OMNS 10 has an additional wire or several wires available with a crocodile for quick setup and connection to the local grounding system to release the currents through a Faraday cage.
• Fig. 1 Measuring dangerous voltage contact can be performed with several known methods applied in electrical engineering.
• Fig. 1 used two auxiliary probes 1 1 connected to point NE10 at device 10.
• the auxiliary probes 1 1 are nailed to the ground and connected to grounding 40 - 50m away from the burning building or their grounding systems.
• the two probes have the potential of 0V and enable measurement of grounding resistance and voltage.
• the measuring methods are known, and there are many instruments and devices at disposal.
• a single or several auxiliary probes 11 have to be nailed to the ground in the opposite direction from the fire and outside of the potential area of the main grounding systems.
• the measuring of voltage between the auxiliary probe 11 and the main grounding system is performed by the measuring signalling device 10 in accordance with known measuring methods.
• device 10 triggers a signal - a warning signal to the firemen of a dangerous voltage contact - and sets off the order to turn off water or fire extinguishing media supply. Turning off the water supply is carried out with the signal from device 10, which triggers the propulsion 7a of valve 7, as shown in Fig. 1a.
• the valve is mounted on the supply pipe for water or fire extinguishing media.
• the amplitude of voltage contact which may be self-indicated with the appropriate indicator or measured by a voltmeter between the auxiliary probe attached to point NE10 or the common point PE10 of the device 10 and the fire extinguishing system.
• the grounding resistance increases due to a number of factors, such as a drop of groundwater, drying of the earth, the electrolysis phenomenon or as the current becomes stronger due to more sunlight on the panels, etc., even though this increase is slow.
• the measuring and malfunction signal warns of the dangerous voltage contact in time.
• Constant measuring and monitoring of continuous connection between the fire extinguishing system and the grounding system prevents unpleasant surprises, such as the rise of voltage contact over permitted values. Measuring only the common grounding resistance gives us the information whether resistance is constant or whether it varies considerably from its initial value, which can increase due to electrochemical processes on the grounding system, a drop of groundwater, heating of the earth or other causes.
• the measuring signalling device 10 measures interruptions and the values of the common grounding resistance according to known methods. In the case of interrupted connection between the fire extinguishing system and the grounding system or a substantial increase of the grounding resistance, device 10 signals a warning to the firemen that the grounding is cut off , closing the water supply.
• the measuring signalling device 10 measures the current between the entire fire extinguishing system and the common grounding system.
• the value of current loz is calculated indirectly from the Ro grounding resistance and voltage contact.
• the value loz helps the fire chief at deciding upon the use or perhaps preparation of new grounding material, such as nailing in grounding points, throwing grounding panels 8 into creeks, wells, lakes, or searching for more distant grounding systems.
• measuring signalling devices 10 can be attached to one grounding point or several points. For the operation of two or more devices 10, points ⁇ and points NEio have to be connected. These connections save time when another fire extinguishing unit joins the task and the entire fire extinguishing system has to be connected and grounded. In this manner a number of devices 10 can be connected, they forming a type of grid or circle on any topology. Regardless of the distribution and number of devices 10, the voltage contact remains and is at all times the main parameter of danger and the basis for turning off the fire extinguishing media. After turning off all fire extinguishing media at a site of a fire, setting on is automatic, but with a time delay, which occurs when contact voltage levels are under 120V.
• the sequence of activations can also have priorities, such as cooling the fire extinguishing shields near the fire, extinguishing inner fire incursion, etc.
• Some fire extinguishing media, which are critical or life-saving need not be disconnected, however, firemen have to be protected from voltage contact in a different way.
• Several devices 10 can be interconnected pneumatically, hydraulically, mechanically, acoustically, by light, through wire or wireless communication, optical communication for the transfer of signals and parameter values, such as current, contact voltage, grounding resistance, disconnection, and other.
• the most important data is the contact voltage and the signal to disconnect the fire extinguishing media via an automatic valve system consisting of propulsion 7a and valve 7 according to Fig. 1a.
• the purpose of network connections is to transfer the signal to alert the firemen of danger and to disconnect the fire extinguishing media, because this is a kind of switch that breaks contact with the dangerous voltage contact.
• Devices 10 can be mounted to fire trucks or can be portable with their own charging system.
• the measuring signalling device 0 measures the continuous connection between the grounding system and the fire extinguishing system, it measures the values of the total grounding resistance, calculates the amplitude of the grounding current and measures or indicates voltage contact.
• device 10 When a signal warns of disruption or of a phenomenon of dangerous contact voltage, device 10 sets off a command to turn off the water or other fire extinguishing media supply, which takes place automatically.
• the signal for interruption is transferred acoustically, by light, wire or wireless communications system between the trucks or fire extinguishing systems. All devices 10 are connected by one or several wires to the common grounding point PE-io and neutral point NE 0 , and as such function autonomously.
• the signal to turn off water or fire extinguishing media is mandatory for everybody at the fire site and is accompanied by audio and light warning signals.
• the device 10 In cases of weak grounding, i.e. too large grounding resistance, the device 10 has a built-in electronic circuit, which is charged from all panels through diodes on the positive pole and through diodes on the negative pole, and which releases voltage of opposite polarity to the common grounding point of the same amplitude with the aid of electronic switches as shown in Fig. 3. This enables a total voltage at the common grounding point of 0V. Essentially, a current of adequate amplitude Ik is released, which at Ro (grounding resistance) causes a drop of voltage of the opposite polarity. Therefore, the drop of voltage at Ro is also zero because of the sum of all currents, which equal zero.
• the diodes prevent electric contact of PV panels also during operation. During regular operation of the solar power plant, the diodes may be switched off through the installation switches or fuses and can be turned on only during a fire. The device works so that it measures the voltage contact between the grounding point PE 10 and the neutral point NEi 0 . On the basis of this information, the ⁇ microprocessor releases (with the aid of electronic switches) contact voltage of the opposite polarity to the grounding point, or opens the switches to the same pole, which artificially lowers voltage contact. Device 10 achieves voltage from diodes on the positive pole of the panels or negative pole of the panels.
• Present invention comprises measures and devices for preventing voltage contact, and enables safe fire extinguishing of photovoltaic power plants.
• the system of electric conditions is constantly under control with the aid of passive protective measures, such as the levelling out of potential and grounding of the fire extinguishing system and active protective measures, such as annulling dangerous contact voltage by electric circuit and instant breakdown or turning off of the fire extinguishing media supply with the aid of an automatic valve system.
• the entire system is connected or attached to a measuring signalling device 10, which, i.a., measures the contact voltage, triggers the warning signals, controls the active electronic circuit for the annulment of voltage contact and/or turns off the fire extinguishing media supply.
• Several devices 10 can be interconnected to a unified system for safe fire extinguishing of photovoltaic power plants.

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• Engineering & Computer Science (AREA)
• Public Health (AREA)
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• Health & Medical Sciences (AREA)
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• Sustainable Development (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Fire-Extinguishing By Fire Departments, And Fire-Extinguishing Equipment And Control Thereof (AREA)
• Hybrid Cells (AREA)
• Photovoltaic Devices (AREA)

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• 2012
  • 2012-06-27 SI SI201200219A patent/SI24126A/sl not_active IP Right Cessation
• 2013
  • 2013-06-24 EP EP13762913.5A patent/EP2866904A2/de not_active Withdrawn
  • 2013-06-24 WO PCT/SI2013/000041 patent/WO2014003691A2/en active Application Filing

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