Abstract
A device for minimizing the risk of fire in weed control applications, provides that arcs are detected by analyzing characteristic partial discharge or current and voltage values, which are prevented by round, channel-less geometries, the use of a depth electrode or the use of high ground contact pressures, which are extinguished by extinguishing mats or liquid spraying on the treated and/or surrounding surface before, during or after the high voltage treatment.
Claims
1. Method for minimizing the risk of fire when working with electrodes (2, 3) at the soil (96) with weeds (22), which is denominated substrate (96, 22), characterized in that partial corona or arcing discharge, or current or voltage values, are detected by a sensor system, which acts to minimize the risk of fire.
2. Method according to claim 1, characterized in that the sensor system acts by switching off the high voltage.
3. Method according to claim 2, characterized in that the sensor system acts by switching off the high voltage for a period of time between 0.1 and 100 milliseconds to de-ionize the air, therefore limiting the arc size and/or preventing it from forming.
4. Method according to any of the preceding claims, characterized in that the sensor system acts by changing the relative speed between electrodes and substrate or the electrode position to minimize arc size and reduce impedance.
5. Method according to any of the preceding claims, characterized in that a high-voltage-side current and/or voltage measurement is used to detect arcs.
6. Method according to any of the preceding claims, characterized in that a current and/or voltage measurement on the high voltage side is used to limit the current or voltage by briefly switching off at least parts of the high voltage device.
7. Method according to one of the preceding claims, characterized in that the high voltage is automatically switched off as soon as the relative speed between the high voltage electrode and the substrate exceeds or falls below a limit value.
8. Method in particular according to one of the preceding claims, characterized in that electrical field control electrodes are used.
9. Method according to one of the preceding claims, characterized in that a short circuit device is used.
10. Method in particular according to one of the preceding claims, characterized in that rounded electrode geometry surfaces directed towards the ground (23) or weeds are used.
11. Method in particular according to one of the preceding claims, characterized in that depth electrodes (250) arranged at least 0.5 m below the bottom surface (96) are used.
12. Method in particular according to one of the preceding claims, characterized in that with ground sliding electrodes (2, 3) at least a force of 1 N, in particular 15 N and at most 15000 N is exerted on the substrate (96, 22).
13. Method in particular according to one of the preceding claims, characterized in that a sectorized electrode arrangement is used.
14. Method in particular according to one of the preceding claims, characterized in that a liquid preferably water is sprayed onto the soil (96) or weeds (22) before, during or after the high-tension treatment to prevent a temperature increase causing a fire.
15. Method in particular according to one of the preceding claims, characterized in that mats are drawn behind the treated surface.
16. Method in particular according to one of the preceding claims, characterized in that the electrodes are short-circuited by means of a manually operated insulated rod, a high voltage switch, in order to avoid sparks and possible human accidents before and/or after the use of the equipment.
17. Device for minimizing the fire risk in weed control applications comprising electrodes (2, 3), characterized in that the electrodes (2, 3) are arranged in sectors in such a way that individual electrodes (2, 3) are not connected to each other in a low-ohmic manner.
18. Device according to claim 17, characterized in that one pole (plus or minus) is not sectorized, while the other pole is sectorized.
19. Device according to claim 18, characterized in that the non-sectorized pole is arranged as an electrode between the sectorized electrodes in the direction of travel and the sectorized electrodes are arranged alternately in front of and behind the non-sectorized electrode in the direction of travel.
20. Device, in particular according to one of the preceding claims, characterized in that field control electrodes are arranged on the electrodes which reduce the local electric field strength in order to inhibit the ionization process of the air.
21. Device according to claim 20, characterized in that the field control electrodes consist of conductive and/or flexible material.
22. Device in particular according to any of the preceding claims, characterized in that the electrodes have a base body with rounded edges around which an electrically conductive material is bent.
23. Device according to claim 22, characterized in that the base body is arranged elastically movable on a support.
24. Device according to claim 22 or 23, characterized in that the base body comprises an insulating material.
25. Use of a device according to any of the previous claims, characterized in that at least one electrode or parts of an electrode-rod are arranged under the surface of the earth.
Description
[0037] Several design examples are shown in a drawing and are described in more detail below.
It shows
[0038] FIG. 1 an arrangement of a modular high voltage source,
[0039] FIG. 2 an electrode without edges,
[0040] FIG. 3 a sample electrode,
[0041] FIG. 4 a deep soil layer electrode,
[0042] FIG. 5 an area with the highest electric field strength at the ends of the electrode plates for observing two different geometries of the electrode,
[0043] FIG. 6 a first electrode arrangement,
[0044] FIG. 7 another electrode arrangement,
[0045] FIG. 8 shows a nonlinear field control (top view left angular and rounded; bottom view right),
[0046] FIG. 9 a nonlinear field control when using split electrodes; with and without rounding,
[0047] FIG. 10 a use of several layers (e.g. three layers),
[0048] FIG. 11 a geometric field control; from left: electrode view from below, above, laterally straight, laterally bent,
[0049] FIG. 12 an electric field control for deep soil layer electrodes,
[0050] FIG. 13 an electric field control for cutting elements such as discs,
[0051] FIG. 14 a radar sensor positioning,
[0052] FIG. 15 an improvement in the coupling of the electrode to the plants through contact pressure,
[0053] FIG. 16 shows a high-voltage area at the rear of the vehicle with an extinguishing mat between the high-voltage area and the vehicle,
[0054] FIG. 17 a high-voltage area at the front of the vehicle with a fire extinguishing mat immediately behind the high-voltage area,
[0055] FIG. 18 a high voltage area at the front of the vehicle with a fire extinguishing mat behind the vehicle,
[0056] FIG. 19 a high-voltage area at the front of the vehicle and a fire extinguishing mat in front of and behind the vehicle, and
[0057] FIG. 20 a manually operated short circuit device.
[0058] FIG. 1 shows how in a modular design of the high voltage source 1 one pole is bridged to avoid series connection of voltage sources due to inhomogeneities of the substrate. In this case the voltage of several sources would add up and lead to unacceptably high voltages for the insulation. FIG. 1 shows the separation of electrodes 2, which can be designed as a positive pole, and an electrode 3, which is designed as a negative pole or bridged pole, for example. High voltage converter modules 4 are connected to electrodes 2 and 3. A central CPU 5 is connected to the high-voltage converter modules 4 via communication and control paths 6 and the high-voltage converter modules 4 are connected to the electrodes 2, 3 via high-voltage connections 7.
[0059] FIG. 2 shows a general electrode shape without edges as side view, front view and top view. For this purpose, sheets are formed and connected elliptically. The distances d1 to d11 are design parameters. Depending on the choice of parameters, different shapes can be achieved:
e.g. sphere with diameter x:
d1=d3=d5=d6=d7=d9=d10=d11=d4/2=x/2
d2=d8=0m
e.g. hemisphere with diameter x:
d1=d3=d5=d6=d7=d9=d10=d11=d4=x/2
d2=d8=0m
[0060] For enlargements, e.g. to increase the contact area or to determine the working width, d2 and d8 can be adjusted accordingly. All distances can be varied in the range>=0 m.
[0061] The mounting can be made of flexible material to achieve height adjustment by spring tension, especially in combination with electrical insulation.
[0062] The example electrode 10 shown in FIG. 3 has a curved shape with curved surfaces 11, which reduces the edges. The flexible material 12, which is preferably an insulating material, allows movement in a vertical direction, which compensates for unevenness of the substrate 13 and at the same time ensures constant contact pressure in a defined range. The electrode is attached to the flexible material, e.g. by means of screws 14, to which a cable 15 can also be attached. The electrode can be mounted to a frame part by means of a further fastening device 16. The electrode is preferably drop-shaped.
[0063] FIG. 4 shows the principle arrangement of a deep soil layer electrode 20. The current flow between electrodes 20 and 21, which is used e.g. for weed control, is adjusted. Layer 22 shows the vegetation with the plants and layer 23 shows the soil. The electrode 20 can be installed on the carrier vehicle as well as fixed to the ground or buried. When attached to the carrier vehicle, electrode 20 can have a high voltage insulation to the carrier vehicle.
[0064] A key factor for arcing is the potential difference between the high voltage electrodes 20 and 21 and the plants 22. To reduce the voltage of the electrodes, depth electrodes 20 can be used that are placed in the soil. In this way, the plant resistance and the resistance of the first soil layers 23 can be bypassed and thus the total resistance to be bridged is reduced. Lower soil layers 24 can also be contacted directly.
[0065] A current flow is set between the electrodes 20, 21. The deep electrode can be installed on the carrier vehicle as well as fixed stationary on or in the underground or buried.
[0066] When a frame (not shown) with electrodes 30, 31 is lowered to the working height as shown in FIG. 5, electrodes 30, 31 are in contact with substrate 32. Due to the applied voltage and the fact that the electrodes are sheet metal, high local electric field strengths are generated at sheet edges 33, 34, which can lead to arcing on low-conductive substrates. At the ends of the electrodes 30, 31 an increased arcing is to be expected. A rigid electrode, as shown in FIG. 5 on the left side, favors arcing, while an electrode that rests against the floor, as shown on the right side, reduces the risk of arcing. Flexible electrodes that bend against the ground during installation are therefore preferred.
[0067] FIG. 6 shows an electrode arrangement 40 where the positive electrodes 41, 42 are separated and alternately arranged in the possible direction of travel 43 in front of and behind the bridged negative electrode 44. Each positive electrode 41, 42 is connected to an individually controlled power source (not shown). The distance of the positive electrodes 42, 42 from each other provides a high degree of electrical independence and thus a more uniform treatment result.
[0068] In case of critical space requirements, as in the case of the electrode arrangement 50 shown in FIG. 7, the ageing of the electrodes 51, 52 relative to the negative electrode 54 in direction of travel 53 can be dispensed with.
[0069] FIG. 8 shows an example of a non-linear field control. For this purpose, a material is used which changes to a more conductive state at high electric field strengths. This allows the higher local field strengths to be suppressed and lowered. For this purpose, a suitable material 62, 63 is attached to the end of the electrodes 60 and 61, which extends outwards over the electrodes 60, 61 and thus extends the arrangement. The transition 64 of material 62 to electrode 60 is angular and the transition 65 of material 63 to electrode 61 is rounded. The materials are joined, for example, with rivets 66.
[0070] Accordingly, as shown in FIG. 9, a rounding 72, 73 can be used at the end of electrode 71 for split electrodes 70, 71 to reduce the number of edges of the arrangement. The field control element 74 to 77 is wider than the electrodes 70, 71 to homogenize possible lateral critical inhomogeneity's of the electric field.
[0071] At the end of electrodes 80, 81, several layers 82 to 84 of conductive material can be attached as shown in FIG. 10. With the help of these layers, the electrical potential can be successively reduced and thus lead to a homogenization of the electrical field strength. The nominal conductivity of the individual layers is gradually reduced (σ1>σ2>σ2>σ3). Non-linear material and a rounding at the end are particularly advantageous.
[0072] FIG. 11 shows how the electrode potential can be directed to the substrate by means of geometric field control. The geometrical shape stretches the potential and smoothes the electric field strength. A wedge-shaped conductive material 83, 84 is attached to the end of the electrodes 81 and 82. As a field control element, a further plate 85, 86 is attached to the wedge 83, 84, so that the distance to the substrate is continuously increasing. By using a curvature 87 (e.g. Rogowski profile) the electric field can be additionally homogenized.
[0073] An electric field control for deep soil layer electrodes 90, 91 is shown in FIG. 12 and FIG. 13 shows an electric field control for cutting elements 92 to 94, such as slices. In the direction of movement a rotating or, as a cutting edge, a non-rotating disc 97 made of metal can be pulled through the soil 96. This creates a field with high electric field strength in the rear area 98 and there is a risk of electric arcs.
[0074] FIG. 14 shows five possible positions of the sensors on a tractor 100 with a power generation unit 101 and an applicator 102. Three exemplary positions 103, 104, 105 detect a relative movement on the ground 106. Two further positions 107 and 108 detect a relative movement of the tires 109 and 110. This has the advantage that possible ground movements, e.g. grasses moving in the wind, have no influence on the correct condition evaluation.
[0075] FIG. 15 shows an electrode 111 and schematically the plant as a whole system, including the carrier vehicle, which are in relative motion to substrate 112. The sliding contact is generally high-impedance and can determine the power output and thus the biological performance depending on the substrate. A high-impedance contact resistance generates a voltage between electrode and plant 113 (or substrate), which is the decisive parameter for arcing. By reducing the contact resistance, the local soil potential is increased and the voltage 114, 115 between electrode and plant is reduced. By applying a defined contact pressure 116 of the electrode 111 on the substrate 113, the contact resistance can be reduced and both the biological effect and the overall safety with regard to arcing and fire hazard can be improved. The reason for this is an increased effective contact area.
[0076] The local critical field strength can be reduced by increasing the contact pressure and/or by targeted mechanical destruction of the plants in order to improve the coupling of the electrode to the plant, as shown in FIG. 15.
[0077] FIGS. 16 to 19 show different arrangements 120, 130, 140, 150 of the extinguishing mats in relation to the application area, the carrier vehicle and the direction of travel. The application area results in a trapezoidal danger area for fires (3).
[0078] The high-voltage area is shown in FIG. 16 as applicator area 121 at the rear of the vehicle 122. Behind it is an extinguishing mat 123 and a danger area 125 in the direction of travel 124. In FIG. 17, the high-voltage area is attached to the front of the vehicle 132 as applicator area 131, while an extinguishing mat 133 is located directly behind the high-voltage area 131 in the direction of travel 134. The danger area 135 is thus partly located under the vehicle 132.
[0079] FIG. 18 shows a high-voltage area as applicator area 141 at the front of vehicle 142 and an extinguishing mat 143 in the direction of travel 144 behind vehicle 142. The danger area 145 therefore extends under the entire arrangement. FIG. 19 shows a high-voltage area as applicator area 151 at the front of the vehicle 151 and one fire extinguishing mat 153 and 156 each in direction of travel 154 in front of and behind the vehicle 152. Here, too, the danger area 155 extends under the entire arrangement.
[0080] A version of a manually operated short circuit device 160 is shown in FIG. 20 and consists of two rods 161 and 162, which are made of electrically non-conductive material. These bars have two electrodes 163 and 164 at the ends and are connected by a cable 165. The ends of the rods 161 and 162 are designed as handles 166 and 167 and are limited by disks 168 and 169.
