A pulsed power drilling system and method for breaking a mineral substrate

Abstract

The technology disclosed relates to a pulsed power drilling system 100 for breaking a mineral substrate 400 and to a method for breaking a mineral substrate 400 by passing a pulsed electrical current through the mineral substrate 400. The disclosed pulsed power drilling system 100 and method 500 using microwave radiation for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate 400 to create localized ionizations inside the mineral substrate 400. The disclosed pulsed power drilling system 100 and method 500 may for example be applied in rock drilling, concrete processing, mineral processing, and continuous mining. The present disclosure further relates to a drill rig 600 comprising a pulsed power drilling system 100, a computer program product comprising instructions, and the use of a pulsed power drilling system 100.

Description

[0001] TITLE

[0002] A pulsed power drilling system and method for breaking a mineral substrate

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a pulsed power drilling system for breaking a mineral substrate and to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate. The disclosed pulsed power drilling system and method use microwave radiation for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations inside the mineral substrate. The disclosed pulsed power drilling system and method may for example be applied in rock drilling, concrete processing, mineral processing, and continuous mining. The present disclosure further relates to a drill rig comprising a pulsed power drilling system, a computer program product comprising instructions, and the use of a pulsed power drilling system.

[0005] BACKGROUND

[0006] In the field of rock drilling, a new technology has emerged during recent years, referred to as pulsed power drilling. The technology relies on the application of high voltage electric pulses between electrodes of a drill head to allow for a high voltage current pulse to pass between the electrodes via a rock. The discharge occurring, if successful, penetrates the rock material and breaks loose small pieces of rock.

[0007] The success probability of formation of high-pressure discharge channel inside the rock is today mainly dependent on a non-uniform distribution of the high-intensity electric field created by the high voltage pulse inside the rock. Since alternative routes for the discharge could be more favorable, pulsed power drilling systems typically require short rise times. The inherent breakdown strength of the rock material requires the use of high voltages.

[0008] Moreover, some of the discharges are today likely to occur directly between the electrodes of the drill head, for example via ionizable water present between the electrodes above the rock surface, not penetrating the rock material. When the discharge does not penetrate the rock material, a loss of efficiency occurs. Ultimately, such a failed rock penetration will result in that no rock destruction is achieved.

[0009] There are today typically also relatively high requirements on the positioning accuracy of the drill head in that the electrodes of the drill head must be positioned in close proximity to the rock surface to allow for a high voltage current pulse generated by the pulsed power generator to pass between two electrodes of the drill head via the rock to be drilled.

[0010] For pulsed power drilling systems, there exist a need in the drilling industry to reduce the required pulse voltage, lowering the rise time requirements, increasing the electrode distance and / or lowering the positioning accuracy of the drill head and to achieve a higher probability of rock penetration for each pulse or a combination thereof.

[0011] SUMMARY

[0012] In light of the foregoing discussion, the technology disclosed is aimed to overcome the aforementioned drawbacks associated with current pulsed power drilling tools, such as the requirements for high voltages, the risk of non-penetrating discharge resulting in lower speed of drilling or material fragmentation and the relatively high requirements on the positioning of the electrodes close to each other and in close proximity to the rock surface.

[0013] The technology disclosed is proposing the emission of microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate, or rock, for the purpose of creating localized ionizations present inside the mineral substrate prior to and during the generation of a high voltage electric pulse. Such localized ionization will simplify the main failure of the rock by reducing the dielectric strength of the rock material. The lower dielectric strength may be exploited as either reducing the required pulse voltage, increasing the electrode distance, and / or for achieving a higher probability of rock penetration for each pulse or a combination thereof.

[0014] A primary object of the present disclosure is therefore to achieve an in at least some aspects improved pulsed power drilling system and method for pulsed power drilling. In particular, it is an object to achieve such a pulsed power drilling system and method which alleviate at least some of the drawbacks associated with prior art pulsed power drilling tools, such as the requirements for high voltages, the risk of non-penetrating discharge resulting in lower speed of drilling or material fragmentation, and the high requirements on the positioning of the electrodes relatively close to each other and in close proximity to the surface of the mineral substrate to be drilled.

[0015] Other objects of the present disclosure include the use of an improved pulsed power drilling system according to any of the embodiments disclosed and achieving an in at least some aspects improved drill rig comprising the improved pulsed power drilling system according to any of the embodiments disclosed.

[0016] The technology disclosed relates to a pulsed power drilling system and method for breaking a mineral substrate by concurrently, or substantially concurrently, emitting microwave radiation and applying a high voltage electric pulse to an anode and / or a cathode of the pulsed power drilling system, so as to as to allow a high voltage current pulse to pass between the anode and the cathode via inclusions in the mineral substrate that are already and still ionized by the microwave radiation.

[0017] According to aspects of the disclosure, at least the primary object may be achieved by a pulsed power drilling system according to claim 1 , hereinafter also referred to as a drilling system. The pulsed power drilling system is configured for passing a pulsed electrical current through a mineral substrate to break a mineral substrate and is comprising a pulsed power generator for generating high voltage electric pulses and a drill head comprising a plurality of electrodes electrically connectable to the pulsed power generator. According to the technology disclosed, the pulsed power drilling system further comprises an arrangement for generating and emitting microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting the microwave radiation and the pulsed power generator is configured to generate a high voltage electric pulse after the generation of at least a portion of the microwave radiation generated by the device for generating microwave radiation.

[0018] In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated within a time period, e.g. a pre-determined time period, that is less than 10 milliseconds from the generation of at least a portion of the micro wave radiation. In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated after and during the generation of at least a portion of the micro wave radiation.

[0019] In embodiments, the device for generating microwave radiation is configured to generate microwave radiation having an average power that is within the range 50 W to 250 W.

[0020] In embodiments, the pulsed power drilling system is further comprising a control system and at least one switching arrangement. The control system may then be configured to control the at least one switching arrangement to control the generation of the high voltage electric pulse by pulsed power generator so that the high voltage electric pulse is generated after generating of at least a portion of the micro wave radiation.

[0021] In certain embodiments, the control system may be configured to control at least one switching arrangement to control the generation of the high voltage electric pulse by pulsed power generator so that the high voltage electric pulse is generated within a time period, e.g. a pre-determined time period, that is less than 10 milliseconds from generating of at least a portion of the microwave radiation.

[0022] In certain embodiments, the control system may then be configured to control the at least one switching arrangement to control at least one of timing of the generation of the high voltage electric pulse by pulsed power generator and timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within a time period, e.g. a pre-determined time period, that is less than 10 milliseconds from generating at least a portion of the microwave radiation.

[0023] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width that is less than 5 milliseconds.

[0024] In embodiments, at least portions of the free end of the antenna structure for emitting microwave radiation is positioned at a distance to portions of the free end of each of the electrodes of the drill head that is substantially equal to or less than the mutual distance between the closest portions of the free ends of each pair of electrodes of the drill head. In embodiments, at least a portion of the antenna structure for emitting microwave radiation is at least partly made of an electrically non-conductive dielectric material.

[0025] In embodiments, the free end of the antenna structure for emitting microwave radiation is at least one of a solid electrode portion of one of the electrodes functioning as a microwave antenna, an end portion of a structure for focusing microwave radiation generated by the device for generating microwave radiation and an end portion of a waveguide for carrying microwave radiation generated by the device for generating micro wave radiation.

[0026] In embodiments, the free end of the antenna structure for emitting microwave radiation is a solid electrode portion of one of the electrodes functioning as a microwave antenna, where the solid electrode portion is electrically connectable to the device for generating micro wave radiation.

[0027] In embodiments, the free end of the antenna structure for emitting microwave radiation is a coaxial cable functioning as an electrode that is electrically connectable to both the device for generating high voltage electric pulses, or pulsed power generator, and an antenna structure that is electrically connectable to the device for generating microwave radiation. The coaxial cable may then be configured for carrying both the microwave radiation generated by the device for generating microwave radiation and the high voltage electric pulse generated by the device for generating high voltage electric pulses. For example, the pulsed power drilling system may comprise at least one coaxial cable and at least one of the at least one coaxial cable functioning as both an electrode and a microwave antenna may then first carry a microwave pulse for creating localized ionizations in the mineral substrate and then carry a high voltage electric pulse applied to the portion of the coaxial cable functioning as an electrode, so as to allow a high voltage current pulse to pass between the two coaxial cables via already and still localized ionizations in the mineral substrate.

[0028] In embodiments, the arrangement for generating and emitting microwave radiation comprises at least one microwave-transmissive device configured for positioning the focus point of the microwave radiation generated by the device for generating microwave radiation and emitted by the antenna structure for emitting microwave radiation so that the focus point of the microwave radiation is in front of the drill head at a distance relative each of the electrodes of the drill head that is within the range 1 to 50 cm. The microwave-transmissive device for positioning the focus point of the microwave radiation may then typically comprise at least one lens.

[0029] In certain embodiments, the pulsed power drilling system comprises a control system and at least one switching arrangement where the control system is further comprising a control circuitry for controlling the at least one switching arrangement. The control circuitry of the control system may then be configured to control the at least one switching arrangement to control at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within less than 10 milliseconds from at least a portion of the time interval of the pulse width of the micro wave pulse.

[0030] In embodiments, the technology disclosed relates to a pulsed power drilling system comprises a device for generating a microwave pulse and a control system comprising at least one control circuitry and at least one switching arrangement, where at least one of the at least one control circuitry of the control system is configured to control, by controlling at least one of the at least one switching arrangement, the timing of the generation of a high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated by the device for generating high voltage electric pulse after and during the generating of the micro wave radiation.

[0031] In embodiments, the technology disclosed relates to a pulsed power drilling system comprising a control system comprising at least one control circuitry and at least one switching arrangement, where at least one of the at least one control circuitry of the control system is configured to control, by controlling at least one of the at least one switching arrangement, the timing of the generation of both a high voltage electric pulse generated by the pulsed power generator and the device for generating microwave radiation so that the high voltage electric pulse is generated by the device for generating high voltage electric pulse after and during the generating of the micro wave radiation by the device for generating micro wave radiation.

[0032] In aspects, the technology disclosed relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, where the pulsed power drilling system is further comprising an arrangement for generating microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting micro wave radiation, the method comprising:

[0033] - generating, by the device for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate;

[0034] - passing the generated microwave radiation to the antenna structure for emitting micro wave radiation;

[0035] - emitting, from the antenna structure for emitting microwave radiation, the generated microwave radiation in the direction of the mineral substrate; and

[0036] - generating, by the pulsed power generator, a high voltage electric pulse so that the high voltage electric pulse is generated after generation, by the device for generating microwave radiation, of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate; and

[0037] - passing the generated high voltage electric pulse to two of the electrodes of the drill head, so as to allow passing of a high voltage current pulse between the two electrodes via already and still localized ionizations present in the mineral substrate.

[0038] In embodiments, the method is comprising generating the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 10 milliseconds from the generating of at least a portion of the generated microwave radiation affecting the electric field and electric charge distribution inside the ionizable inclusions in the mineral substrate.

[0039] In embodiments, the method is comprising generating the high voltage electric pulse so that the high voltage electric pulse is generated by the device for generating high voltage electric pulses after and during the generating of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside the ionizable inclusions in the mineral substrate. In embodiments, the step of generating microwave radiation is comprising generating microwave radiation having an average power within the range 50 W to 250 W.

[0040] In aspects, the technology disclosed relates to a computer program product comprising instructions, which when executed by a processor, causes the processor to perform any of the above-mentioned method steps.

[0041] The present disclosure also relates to use of a pulsed power drilling system for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

[0042] Advantages of the improved pulsed power drilling system comprising an arrangement for generating and emitting microwave radiation adapted for affecting the electric field and electric charge distribution inside the mineral substrate to create localized ionizations inside the mineral substrate include reducing the required pulse voltage, increasing the electrode distance and to achieve a higher probability of rock penetration for each pulse or a combination thereof. These advantages also apply to a drill rig comprising the improved pulsed power drilling system, the use of the improved pulsed power drilling system and the method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of the improved pulsed power drilling system comprising the arrangement for generating and emitting microwave radiation adapted for affecting the electric field and electric charge distribution inside the mineral substrate.

[0043] The pulsed power drilling system of the present disclosure comprising an arrangement for generating and emitting microwave radiation for affecting the electric field and electric charge distribution inside ionizable inclusion, e.g. inside void and microcracks comprising fluids and gas, in the mineral substrate to create localized ionizations inside the mineral substrate may also enable that a good electrical contact may be achieved also with uneven substrate surfaces and / or when the solid electrode portions of the drill head are positioned a longer distance from the substrate surface than for current pulsed power drilling tools, while the efficiency of the drilling process may be maintained or improved. Thus, the pulsed power drilling system of the present disclosure may thus enable that the drill head with its solid electrode portions may be positioned a longer distance from the mineral substrate to be drilled than possible with other known drilling systems. Electrode wear as well as the risk for non-penetrating discharge between the electrodes can thereby be reduced, while the efficiency of the drilling process may be maintained or improved.

[0044] Other advantages of the pulsed power drilling system according to the various embodiments of the pulsed power drilling system disclosed include that the degree of localized ionizations inside the mineral substrate may easily be adapted to the overall dielectric properties of the mineral substrate by, for example, adjusting the power of the generated microwave radiation to thereby adjust the degree of localized ionization inside the mineral substrate, or rock.

[0045] Further advantages and advantageous features of the disclosure are disclosed in the following description and in the dependent claims.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In the following, the technology disclosed will be described in detail, with reference to exemplifying embodiments and to the enclosed drawings.

[0048] In the drawings:

[0049] Fig. 1 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0050] Fig. 2 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0051] Fig. 3 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0052] Fig. 4 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0053] Fig. 5 is a flow-chart illustrating steps of a method according to an embodiment of the disclosure, and Fig. 6 is a rock drilling machine, or drill rig, configured for comprising any of the pulsed power drilling system shown in Figs. 1, 2, 3 and 4.

[0054] The drawings show diagrammatic, exemplifying embodiments of the present disclosure and are thus not necessarily drawn to scale. It shall be understood that the embodiments shown and described are exemplifying and that the disclosure is not limited to these embodiments. It shall also be noted that some details in the drawings may be exaggerated in order to better describe and illustrate the disclosure. Like reference characters refer to like elements throughout the description, unless expressed otherwise.

[0055] DETAILED DESCRIPTION

[0056] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.

[0057] In the field of rock drilling, a new technology has emerged during the recent years, referred to as electro pulse boring (EPB), plasma channel drilling, pulsed plasma drilling, etc. The technology relies on the use of a pulsed power generator comprising a drill head with electrodes, and the application of a high voltage between two electrodes of the drill head. The discharge occurring, if successful, penetrates the rock material and breaks loose small pieces of the rock.

[0058] The technology disclosed is aimed at increasing the probability of dielectric breakthrough in a mineral substrate, or rock, by temporarily lowering the dielectric breakdown strength of the mineral substrate to thereby provide for easier and faster electrical breakdown of the mineral substrate in drilling or material fragmentation using generation of a high voltage electric pulse for breaking the mineral substrate.

[0059] The inventors propose the use of microwave radiation that is adapted for ionizing inclusions in a mineral substrate so that at least a portion of the inclusions in the mineral substrate is already and still ionized when generating a high voltage electric pulse for breaking the mineral substrate. The microwave radiation generated in accordance with the technology disclosed is typically not adapted for providing a substantial temperature rise in a mineral substrate and is typically not adapted for creating permanent damage to a mineral substrate for the purpose of simplifying mechanical excavation. The microwave radiation used is instead adapted for creating temporary and localized ionizations in inclusions present in the mineral substrate, which would be pointless for combination with mechanical excavation. The disclosed pulsed power drilling system and method may for example be applied in rock drilling, concrete processing, mineral processing, and continuous mining.

[0060] The probability of successful formation of a high-pressure discharge channel inside the rock is today mainly dependent on a non-uniform distribution of high intensity electric fields created by the high voltage pulse inside the rock. Since alternative routes for the discharge could be more favorable, the currently used pulsed power drilling systems typically require relatively high voltages, short rise times and / or that the electrodes of the drill head are positioned relatively close to each other and in direct contact with, or at a relatively close distance to, the rock surface.

[0061] Even when high voltages and short rise times are used for these pulsed power drilling systems and the electrodes of the drill head are positioned close to each other and at a close distance to the rock surface, the risk of non-penetrating discharge resulting in lower speed of drilling or material fragmentation may still not be negligible, for example when the rock surface to be drilled is particularly uneven and for certain applications in harsh environments. A non-negligible risk of nonpenetrating discharge resulting in slightly lower speed of drilling or material fragmentation may lead to a lower speed of drilling or material fragmentation, i.e. a relatively low efficiency use of these pulsed power drilling systems for certain applications and in certain environments.

[0062] The drawbacks of currently used pulsed power drilling systems thus include the high voltage requirements for these drilling systems and the non-negligible risk of non-penetrating discharge. There is also an overall need in the drilling industry to achieve higher energy efficiency for these pulsed power drilling systems.

[0063] The technology disclosed is therefore aimed at lowering voltage requirements for pulsed power drilling systems and / or improving the success probability of a high voltage pulses generated by a pulsed power drilling system is creating electrical breakdown inside the rock. Further objectives of the technology disclosed include achieving higher energy efficiency for pulsed power drilling systems, enabling for increasing the distance between the electrodes of the drill head to potentially also increase the area and / or volume of fragmentation damage caused by each generated high voltage electric pulse, i.e. improving the efficiency of the pulsed power drilling systems, and alleviating the requirements on positioning of the electrodes relatively close to each other and in close proximity to the surface of the mineral substrate to be drilled, or a combination thereof.

[0064] The technology disclosed relates to a pulsed power drilling system and method for breaking a mineral substrate by generating and emitting microwave radiation and applying a high voltage electric pulse, so as to as to allow a high voltage current pulse to pass between an anode and a cathode of the pulsed power drilling system via inclusions in the mineral substrate that are already and still ionized by the micro wave radiation.

[0065] The anode and / or the cathode may then be an electrode of a drill head of the pulsed power drilling system and a device for generating microwave radiation, typically a microwave generator, generates the high voltage electric pulse after at least a portion of the microwave radiation has been emitted in the mineral substrate for the purpose of creating localized ionizations in inclusions present in the mineral substrate. The high voltage electric pulse is generated and applied after at least a portion of the microwave radiation has been emitted in the mineral substrate.

[0066] Typically, the high voltage pulse is applied to two electrodes of the drill head, so as to as to allow a high voltage current pulse to pass between a first and a second electrode of the drill head via inclusions in the mineral substrate that are already and still ionized by the microwave radiation. However, in certain embodiments of a pulsed power drilling system according to example embodiments of the technology disclosed, the high voltage electric pulse may be applied to an electrode of the drill head and either the anode or the cathode may then be a casing of the pulsed power drilling system that is made of an electrically conductive material and that is adapted for carrying the high voltage current pulse.

[0067] The present disclosure addresses at least some of the above-mentioned drawbacks associated with current pulsed power drilling tools by proposing a pulsed power drilling system comprising an arrangement for generating and emitting microwave radiation for affecting the electric field and electric charge distribution inside the mineral substrate to temporarily create localized ionizations in the mineral substrate prior to generating a high voltage electric pulse by a pulsed power generator, so as to allow passing of a high voltage current pulse between an anode and a cathode, for example two electrodes of a drill head of the pulsed power drilling system, via already and still localized ionizations present in the mineral substrate. These ionizable inclusions may then include fluid inclusions and / or gas inclusions, such as inclusions filled with water and / or air.

[0068] The technology disclosed further relates to a method for breaking a mineral substrate by passing a high voltage current pulse for breaking the mineral substrate via inclusions present in the mineral substrate that are already and temporarily ionized by use of the microwave radiation in that at least a portion of the microwave radiation is generated and emitted by an arrangement for generating and emitting microwave radiation of the pulsed power drilling system prior to generating and emitting the high voltage electric pulse by the pulsed power generator, thereby allowing for the passing of a high voltage current pulse between an anode and a cathode, for example two electrodes of the drill head, of the pulsed power drilling system via a portion of the already and still ionized inclusions present in the mineral substrate.

[0069] In aspects, the pulsed power drilling system according to the technology disclosed comprises a drill head with at least one electrode, but typically a plurality of electrodes, and is configured for passing a pulsed electrical current through a mineral substrate to break a mineral substrate. The pulsed power drilling system may then typically comprise a pulsed power generator for generating high voltage electric pulses, a drill head comprising at least one electrode functioning either as an anode or as a cathode and that is electrically connectable to a pulsed power generator, and an arrangement for generating and emitting microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting the microwave radiation. The pulsed power generator is then configured to generate a high voltage electric pulse that is applied to an anode and / or a cathode, including at least one of the electrodes of the drill head, after the generation of at least a portion of the microwave radiation generated by the device for generating microwave radiation.

[0070] In aspects, the pulsed power drilling system according to the technology disclosed is configured for passing a pulsed electrical current through a mineral substrate to break a mineral substrate. The pulsed power drilling system comprises a pulsed power generator for generating high voltage electric pulses, a drill head comprising a plurality of electrodes electrically connectable to a pulsed power generator, and an arrangement for generating and emitting microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting the micro wave radiation, where the pulsed power generator is configured to generate a high voltage electric pulse after the generation of at least a portion of the microwave radiation emitted for affecting the electric field and electric charge distribution inside the mineral substrate and generated by the device for generating microwave radiation.

[0071] In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated within less than 10 milliseconds from the generation of at least a portion of the microwave radiation.

[0072] In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated within less than 1 millisecond from the generation of at least a portion of the micro wave radiation.

[0073] In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated within less than 50 nanoseconds from the generation of at least a portion of the microwave radiation. In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated after and during the generation of at least a portion of the microwave radiation.

[0074] In embodiments, the pulsed power generator is configured so that the high voltage electric pulse is generated within less than 10 milliseconds from the generation of at least a portion of the microwave radiation and during the generation of at least another portion of the microwave radiation.

[0075] In embodiments, the device for generating microwave radiation is configured to generate microwave radiation having an average power within the range 50 W to 250 W.

[0076] In embodiments, the device for generating microwave radiation is a continuous microwave radiation source configured to continuously generate microwave radiation having a power that is within the range 50 W to 500 W. In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source configured to generate a microwave pulse having an average power over the pulse width that is within the range 50 W to 250 W.

[0077] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source configured to generate a microwave pulse having an average power over the pulse width that is within the range 200 W to 400 W.

[0078] In embodiments, the pulsed power drilling system comprises a control system including at least one control circuitry and configured to control at least one switching arrangement for controlling generation of a high voltage electric pulse by the pulsed power generator so that a high voltage electric pulse is generated after the generating and emitting of at least a portion of the microwave radiation generated by a device for generating microwave radiation of the pulsed power drilling system for the purpose of affecting the electric field and electric charge distribution inside a mineral substrate to create localized ionizations in inclusions present in the mineral substrate prior to generating the high voltage electric pulse.

[0079] In certain embodiments, the pulsed power drilling system comprises a control system including control circuitry and configured to control at least one switching arrangement to control the timing of the generation of the high voltage electric pulse by pulsed power generator so that the high voltage electric pulse is generated after at least a portion of the microwave radiation is generated.

[0080] In certain embodiments, the pulsed power drilling system comprises a control system including control circuitry and configured to control at least one switching arrangement to control the mutual timing of the generation of the high voltage electric pulse and the generation of the microwave radiation by controlling at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the microwave radiation is generated prior to and during the generation of the high voltage electric pulse.

[0081] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source and the pulsed power drilling system comprises a control system configured to control at least one switching arrangement to control the mutual timing of the generation of the high voltage electric pulse and the generation of the microwave pulse by controlling at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave pulse by the pulsed microwave radiation source so that at least a portion of the microwave pulse is generated prior to the generation of the high voltage electric pulse. In certain embodiments, the control system is configured to control the mutual timing so that the high voltage electric pulse is generated by pulsed power generator after and during at least a portion of the time interval of the pulse width of the microwave pulse.

[0082] In certain embodiments, the device for generating microwave radiation is a pulsed microwave radiation source and the pulsed power drilling system comprises a control system configured to control at least one switching arrangement to control the mutual timing of the generation of the high voltage electric pulse and the generation of the microwave pulse by controlling both the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave pulse by the pulsed microwave radiation source so that at least a portion of the microwave pulse is generated prior to the generation of the high voltage electric pulse. In certain embodiments, the control system is configured to control the timing of both the generating of the high voltage electric pulse and the generating of the microwave pulse so that the high voltage electric pulse is generated by pulsed power generator after and during at least a portion of the time interval of the pulse width of the micro wave pulse.

[0083] In certain embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 5 milliseconds. The pulsed microwave radiation source may then be configured to generate a microwave pulse with a pulse width less than 5 milliseconds and having an average power over the pulse width within the range 50 W to 250 W.

[0084] In certain example embodiments, the pulsed power drilling system comprises a pulsed microwave radiation source for providing a microwave pulse with a pulse width less than 100 nanoseconds, a control system and at least one switching arrangement. The control system may then be configured to control the at least one switching arrangement to control at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within less than 1 millisecond from at least a portion of the time interval of generating the microwave with a pulse width less than 100 nanoseconds. The pulsed microwave radiation source may then be configured to generate a microwave pulse having an average power over the pulse width within the range 50 W to 250 W.

[0085] In certain embodiments, the pulsed power drilling system comprises a pulsed microwave radiation source for providing a microwave pulse with a pulse width less than 30 nanoseconds, a control system and at least one switching arrangement. The control system may then be configured to control the at least one switching arrangement to control at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within less than 100 nanoseconds from at least a portion of the time interval of generating the microwave pulse with a pulse width less than 30 nanoseconds. The pulsed microwave radiation source may then be configured to generate a microwave pulse having an average power over the pulse width within the range 50 W to 250 W.

[0086] The arrangement for generating and emitting microwave radiation according to technology disclosed is configured to generate and emit microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate, thereby locally ionizing at least a portion of the inclusions inside the mineral substrate. At least a portion of the microwave radiation is emitted in the direction of the mineral substrate prior to generating the high voltage electric pulse by the pulsed power generator, so as to allow passing of a high voltage current pulse between two of the electrodes of the drill head via already and still ionized portions of the ionizable inclusions present in the mineral substrate.

[0087] The microwave radiation generated and emitted by the arrangement for generating and emitting microwave radiation according to the technology disclosed will typically not cause any substantial temperature increases inside the mineral substrate, e.g. cooking of the rock, and is typically not adapted for creating cracks and permanent damage to the mineral substrate. The microwave radiation is instead adapted for temporarily and locally increasing the electric field strength inside ionizable inclusions in the mineral substrate to thereby create localized ionizations inside these ionizable inclusions that are temporarily lowering the dielectric breakdown strength of the mineral substrate prior to and during generation of the high voltage electric pulse.

[0088] At least portions of the free end of the antenna structure for emitting microwave radiation may be positioned at a distance to portions of the free end of each of the electrodes of the drill head where the distance is substantially equal to or less than the mutual distance between the closest portions of the free ends of each pair of electrodes of the drill head.

[0089] The free end of the antenna structure for emitting microwave radiation may be one of a solid electrode portion of one of the electrodes functioning as a microwave antenna, an end portion of a structure for focusing microwave radiation generated by the device for generating microwave radiation and an end portion of a waveguide for carrying microwave radiation generated by the device for generating microwave radiation. In example embodiments where the free end of the antenna structure for emitting microwave radiation is a solid electrode portion of one of the electrodes functioning as a microwave antenna, the solid electrode portion is electrically connectable to the device for generating micro wave radiation.

[0090] In example embodiments, the free end of the antenna structure for emitting microwave radiation may be a coaxial cable functioning as an electrode. The coaxial cable may then be electrically connectable to both the device for generating microwave radiation and the device for generating high voltage electric pulses and configured both for carrying the microwave radiation generated by the device for generating microwave radiation and for carrying the high voltage electric pulse generated by the device for generating high voltage electric pulses. In certain embodiments, both the first and second electrode is a coaxial cable electrically connectable to both the device for generating microwave radiation and the device for generating high voltage electric pulses and configured both for carrying the microwave radiation generated by the device for generating microwave radiation and the high voltage electric pulse generated by the device for generating high voltage electric pulses. Typically, and in embodiments, at least a portion of the antenna structure for emitting microwave radiation may at least partly be made of an electrically non- conductive dielectric material. The technical effects of providing so that at least a portion of the antenna structure for emitting microwave radiation is made of an electrically non-conductive dielectric material include that alternative routes for the discharge than via the mineral substrate are even less favorable. In other words, in embodiments where the antenna structure is at least partly mad of an electrically non-conductive dielectric material, it is less likely that a non-penetrating high voltage current pulse is passing directly between one of the conductive electrodes to which a high voltage electric pulse is applied and the antenna structure for emitting microwave radiation and more likely that a high voltage electric pulse is passing between one of the electrically conductive electrodes of the drill head to which a high voltage electric pulse is applied via the mineral substrate, i.e. via a portion of the temporarily localized ionizations in the mineral substrate, to another one of the electrically conductive electrodes of the drill head.

[0091] In other embodiments, the arrangement for generating and emitting microwave radiation may comprise at least one microwave-transmissive device configured for positioning the focus point of the microwave radiation generated by the device for generating microwave radiation and emitted by the antenna structure for emitting microwave radiation so that the focus point of the microwave radiation is in front of the drill head at a distance relative each of the electrodes of the drill head that is within the range 1 to 50 cm. The microwave-transmissive device for positioning the focus point of the microwave radiation may then typically comprise at least one lens.

[0092] The technology disclosed further relates to a drill rig comprising a pulsed power drilling system according to any of the above-mentioned embodiments where the pulsed power drilling system is comprising an arrangement for generating and emitting microwave radiation configured to generate and emit microwave radiation for at least partly ionizing at least a portion of the inclusions in the mineral substrate to create localized ionizations, where the device for generating high voltage electric pulses is configured to generate a high voltage electric pulse for breaking the mineral substrate after generating at least a portion of the microwave radiation and the use of such a pulsed power drilling system for breaking a mineral substrate. In aspects, the technology disclosed relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, where the pulsed power drilling system is further comprising an arrangement for generating microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting micro wave radiation, the method comprising:

[0093] - generating, by the device for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate;

[0094] - passing the generated microwave radiation to the antenna structure for emitting micro wave radiation;

[0095] - emitting, from the antenna structure for emitting microwave radiation, the generated microwave radiation in the direction of the mineral substrate; and

[0096] - generating, by the pulsed power generator, a high voltage electric pulse so that the high voltage electric pulse is generated after generation, by the device for generating microwave radiation, of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate; and

[0097] - passing the generated high voltage electric pulse to two of the electrodes of the drill head, so as to allow passing of a high voltage current pulse between the two electrodes via already and still localized ionizations present in the mineral substrate.

[0098] In aspects and embodiments, the technology disclosed relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, where the pulsed power drilling system is further comprising an arrangement for generating microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting microwave radiation, the method is comprising: - generating, by the device for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate;

[0099] - passing the generated microwave radiation to the antenna structure for emitting micro wave radiation;

[0100] - emitting, from the antenna structure for emitting microwave radiation, the generated microwave radiation in the direction of the mineral substrate; and

[0101] - generating, by the pulsed power generator, a high voltage electric pulse so that at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate is generated by the arrangement for generating and emitting microwave radiation prior to generating the high voltage electric pulse; and

[0102] - passing the generated high voltage electric pulse to two of the electrodes of the drill head, so as to allow passing of a high voltage current pulse between the two electrodes via already and still localized ionizations present in the mineral substrate.

[0103] In aspects and embodiments, the technology disclose relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, and an arrangement for generating microwave radiation comprising a device for generating microwave radiation and an antenna structure for emitting microwave radiation, the method comprising:

[0104] - generating, by the device for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate;

[0105] - passing the generated microwave radiation to the antenna structure for emitting micro wave radiation;

[0106] - emitting, from the antenna structure for emitting microwave radiation, the generated microwave radiation in the direction of the mineral substrate; and - generating, by the pulsed power generator, a high voltage electric pulse so that at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate is generated by the arrangement for generating and emitting microwave radiation prior to generating the high voltage electric pulse; and

[0107] - passing the generated high voltage electric pulse to two of the electrodes of the drill head, so as to allow passing of a high voltage current pulse between the two electrodes via already and still localized ionizations present in the mineral substrate.

[0108] The method according to any of the above embodiments may further comprise generating the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 10 milliseconds from the generating of at least a portion of the generated microwave radiation affecting the electric field and electric charge distribution inside the ionizable inclusions in the mineral substrate.

[0109] The method according to any of the above embodiments may further comprise generating the high voltage electric pulse by the pulsed power generator so that the microwave radiation is generated by the device for generating microwave radiation prior to and during the generating of the high voltage electric pulse.

[0110] In embodiments, the technology disclosed relates to a pulsed power drilling system comprising a control system and at least one switching arrangement, where the control system is configured to control, by controlling the at least one switching arrangement, the timing of the generation of the high voltage electric pulse by the pulsed power generator so that the microwave radiation is generated by the device for generating microwave radiation prior to and during the generating of the high voltage electric pulse.

[0111] The technology disclosed also relates to a computer program product comprising instructions, which when executed by a processor, causes the processor to control at least one control circuitry so that a high voltage electric pulse is generated after at least a portion of the microwave radiation used for ionizing at least a portion of the inclusions in the mineral substrate is generated and emitted by the arrangement of generating and emitting microwave radiation. The technology disclosed may further relate to a pulsed power drillings system including a control system comprising a control unit and at least one circuitry where the control unit via the control circuitry is configured to control the timing of the generating of a high voltage electric pulse for breaking a mineral substrate so that at least a portion of microwave radiation adapted to be used for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to locally ionize at least a portion of the ionizable inclusions, e.g. fluid and / or gas inclusions, in the mineral substrate is emitted in the direction of the mineral substrate prior to generating the high voltage electric pulse.

[0112] The technology disclosed also relates to a computer program product comprising instructions, which when executed by a processor, causes the processor to control the timing of the generating of a high voltage electric pulse so that at least a portion of the microwave radiation used for ionizing at least a portion of the inclusions in the mineral substrate is emitted in the mineral substrate prior to generating the high voltage electric pulse for breaking the mineral substrate.

[0113] The technology disclosed is aimed at increasing the probability of dielectric breakthrough in the rock for easier and faster electrical breakdown of the rock in drilling or material fragmentation. To increase the probability of dielectric breakthrough, the inventors propose to prepare the rock for electrical discharge or intrinsic breakdown before, typically within the longevity of the ions, the application of a high voltage electric pulse. This is achieved by letting microwave radiation, e.g. a pulsed microwave beam, excite the voids and microcracks inside the rock right before, but optionally also during, the generation of the high voltage electric pulse so that at least portions of these voids and microcracks is already and still ionized when the high voltage electric pulse is generated, thereby allowing for passing of a high voltage current pulse between two electrodes of the drill head of the pulsed power drilling system via already and still ionized portions of the inclusions present in the mineral substrate.

[0114] The microwave radiation will affect the electric field and electric charge distribution inside ionizable inclusions such as pores and microcracks in the mineral substrate, or rock, to create localized ionizations inside these pores and microcracks. Such localized ionization will simplify the main failure of the rock by reducing the dielectric strength of the rock material. The lower dielectric strength can be exploited as either reducing the required pulse voltage, increasing the electrode distance, and / or for achieving a higher probability of rock penetration for each pulse or a combination thereof.

[0115] To increase the probability of dielectric breakthrough, it is crucial for the technology disclosed that the arrangement for generating and emitting microwave radiation is generating at least some of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions to create localized ionizations inside the mineral substrate is generated at least some time before the high voltage electric pulse is applied. In embodiments, the microwave radiation is a pulsed microwave beam, since the localized ionizations are only required just before the high voltage pulse is applied and the localized ionizations inside the pores and microcracks are only temporarily present for the purpose of temporarily lowering the dielectric breakdown strength of the mineral substrate prior to and during generation of a high voltage electric pulse.

[0116] The power level of the microwave radiation is typically not the most crucial component for the success of the process of achieving localized ionizations inside the mineral substrate. More importantly is that the local electric field strength, at least at some points within the rock material, is high enough to create localized ionizations. For air inclusions in the rock, this would correspond to roughly 3kV / mm. For other ionizable inclusions, e.g. water, various gases, trapped charged particles, the local electric field strength needed to create the localized ionizations inside the mineral substrate could be both lower and higher.

[0117] According to the technology disclosed, the fluid and gas inclusions in a mineral substrate are at least partly locally ionized by means of the microwave radiation generated and emitted by the arrangement for generating and emitting microwave radiation. High voltage current pulses generated by the pulsed power generator typically pass between a solid electrode portion of a first electrode and a solid electrode portion of a second electrode of the drill head via the at least partly ionized fluid and gas inclusions. The pulsed power drilling system may then generate high voltage current pulses that are allowed to pass from the solid electrode portion of the first electrode to the solid electrode portion of the second electrode, or vice versa, via the localized ionizations.

[0118] The pulsed power drilling system may in various embodiment according to the technology disclosed comprise a drill head with three or more electrodes each comprising a solid electrode portion and the system may then be configured to selectively allow for that high voltage current pulses may pass from a first solid electrode portion of any of the three or more electrodes to a second solid electrode portion of any of the other electrodes of the drill head via the fluid and / or gas inclusions that are ionized by use of microwave radiation.

[0119] In embodiments, the technology disclosed relates to a pulsed power drilling system configured for passing a pulsed electrical current through a mineral substrate to break a mineral substrate, where the pulsed power drilling system comprises a control system including a control unit and at least one control circuitry. The control unit may then be configured to control, via at least one of the at least one control circuitry of the control system, the timing of the generation of a high voltage electric pulse by the pulsed power generator so that at least a portion of the microwave radiation is generated by the arrangement for generating and emitting micro wave radiation prior to generating the high voltage electric pulse.

[0120] As an example, the control system may be configured to control the timing of the generation of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 10 milliseconds from the generation of at least a portion of the microwave radiation. The control unit of the control system may then be configured to control the timing of the generation of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated during at least a portion of a time interval for generating at least a portion of the micro wave radiation. The device for generating microwave radiation may then be configured to generate microwave radiation having an average power within the range 50 W to 250 W.

[0121] In an example embodiment, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 5 milliseconds and the control system may be configured to control both the timing of the generation of the high voltage electric pulse by pulsed power generator and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within a time period, for example a predetermined time period, that is less than 10 milliseconds from at least a portion of the time interval of the pulse width of the micro wave pulse. At least portions of the free end of the antenna structure for emitting microwave radiation may be positioned at a distance to portions of the free end of each of the electrodes of the drill head that is substantially equal to or less than the mutual distance between the closest portions of the free ends of each pair of electrodes of the drill head.

[0122] In various embodiments, the free end of the antenna structure for emitting microwave radiation may be one of a solid electrode portion of one of the electrodes functioning as a microwave antenna, the end portion of a structure for focusing microwave radiation generated by the device for generating microwave radiation and the end portion of a waveguide for carrying microwave radiation generated by the device for generating micro wave radiation. As an example, the free end of the structure for emitting microwave radiation is a solid electrode portion of one of the electrodes functioning as a microwave antenna and that is electrically connectable to the device for generating microwave radiation.

[0123] The control system may be configured to control, via the at least one control circuitry, the timing of the generation of the high voltage electric pulse by the pulsed power generator so that the microwave radiation is generated by the device for generating microwave radiation prior to and during the generating of the high voltage electric pulse.

[0124] The device for generating microwave radiation may comprise a circuit for generating microwave radiation and the arrangement for generating and emitting microwave radiation may comprise a waveguide for carrying microwave radiation. The waveguide for carrying microwave radiation may be electrically connectable to the circuit for generating microwave radiation and configured to transport microwave radiation generated by the circuit to the antenna structure for emitting microwave radiation.

[0125] The arrangement for generating and emitting microwave radiation may comprise at least one microwave-transmissive device configured for positioning the focus point of the microwave radiation generated by the device for generating microwave radiation so that the focus point of the microwave radiation is in front of the drill head at a distance relative each of the electrodes of the drill head that is within the range 1 to 50 cm. The at least one microwave-transmissive device for positioning the focus point of the microwave radiation may then typically comprise at least one lens. In embodiments, the technology disclosed relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, and a control system comprising a control unit and at least one control circuitry. The control unit may be configured for controlling the timing of the generation of a high voltage electric pulse by the pulsed power generator via the at least one control circuitry, so that at least a portion of the microwave radiation is generated by the arrangement for generating and emitting micro wave radiation prior to generating the high voltage electric pulse. The generation of the high voltage electric pulse then allows for the passing of a high voltage current pulse between two electrodes of the drill head via already and still ionized portions of the ionizable inclusions present in the mineral substrate.

[0126] The method may further comprise controlling, by the control system controlling at least one control circuitry, the timing of the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 10 milliseconds from the generating of at least a portion of the generated microwave radiation affecting the electric field and electric charge distribution inside the mineral substrate, for example a predetermined time period that is less than 10 milliseconds.

[0127] In embodiments, the method is further comprising controlling, by a control unit of the control system controlling at least one control circuitry, the timing of the generating of the high voltage electric pulse by the pulsed power generator so that the microwave radiation is generated by the device for generating microwave radiation prior to and during the generating of the high voltage electric pulse.

[0128] In embodiments, the pulsed power drilling system comprises at least three electrodes and is configured to allow for that high voltage current pulses may pass from a solid electrode portion of at least any of three of the at least three to any of the other at least two other electrodes via already and still ionizable inclusions in the mineral substrate.

[0129] The generated microwave radiation according to the technology disclosed is emitted for affecting the electric field and electric charge distribution inside ionizable inclusions, e.g. voids and microcracks comprising fluid and / or gas such as air, present in the mineral substrate for the purpose of temporarily and locally increasing the electric field strength inside these ionizable inclusions to thereby create temporary and localized ionizations inside these ionizable inclusions that are temporarily lowering the dielectric breakdown strength of the mineral substrate prior to and during generation of the high voltage electric pulse.

[0130] For example, the pulsed power drilling system may comprise one or a plurality of microwave generators and one or a plurality of antenna structures each configured to emit microwave radiation for affecting the electric field and electric charge distribution inside ionizable inclusions, e.g. voids and microcracks comprising fluid and / or gas such as air, present in the mineral substrate for the purpose of temporarily and locally increasing the electric field strength inside these ionizable inclusions to thereby create temporary and localized ionizations inside these ionizable inclusions that are temporarily lowering the dielectric breakdown strength of the mineral substrate prior to and during generation of the high voltage electric pulse.

[0131] The technology disclosed proposes a pulsed power drilling system that is configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate. The pulsed power drilling system comprises a pulsed power generator for generating high voltage current pulses, a drill head comprising a plurality of electrodes that each typically comprises a solid electrode portion configured to be connected to the pulsed power generator, and an arrangement for generating and emitting microwave radiation used for at least partly and temporarily ionizing inclusions present in the mineral substrate, or rock, prior to and during generation of at least one high voltage electric pulse. The pulsed power drilling system thereby allows for at least one high voltage current pulse generated by the pulsed power generator to pass between the solid electrode portion of a first of the plurality of electrodes and a solid electrode portion of a second electrode of the drill head via the already and still ionized inclusions present in the mineral substrate prior to and during the generation of the at least one high voltage current pulse. In embodiments, at least one of the solid electrode portions may then be electrically connectable to the device for generating microwave radiation and be configured to function as a microwave antenna for emitting the microwave radiation generated by the device for generating microwave radiation.

[0132] The device for generating microwave radiation typically comprise a circuit for generating microwave radiation and the arrangement for generating and emitting microwave radiation may comprise a waveguide for carrying microwave radiation. The circuit may then be connected to the waveguide for carrying microwave radiation and the waveguide for carrying microwave radiation may then be configured to transport microwave radiation generated by the circuit to the antenna structure for emitting micro wave radiation.

[0133] The arrangement for generating and emitting microwave radiation may then comprise at least one microwave generator each including a circuit for generating microwave radiation. In certain embodiments, the at least one circuit may be configured to be electrically connectable to at least one of the electrodes of the drill head or the at least one circuit is configured to be connected to at least one of the electrodes of the drill head via a waveguide configured to transport the microwave radiation generated by the circuit so as to allow the generated microwave radiation to be emitted in the mineral substrate to affect the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate prior to and during the generation of the high voltage electric pulse.

[0134] The arrangement for generating and emitting microwave radiation may then comprise at least one device for generating micro wave radiation, or micro wave generator, in the form of at least one of a magnetron, a solid-state generator, a maser, travelling wave tubes and frequency multipliers. The at least one microwave generator may then be arranged and configured to generate microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate for temporarily creating ionizable inclusions present in the mineral substrate prior to and during generation of a high voltage electric pulse where the high voltage electric pulse is generated for breaking the mineral substrate in that a high voltage current pulse is allowed to pass between two of the electrodes of the drill head via the already ionized inclusions present in the mineral substrate, so as to allow a high voltage current pulse to pass between the solid electrode portion of a first electrode and a second electrode of the drill head via the already ionizable inclusions present in the mineral substrate.

[0135] The microwave radiation generated by the at least one arrangement for generating microwave radiation is adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate so regions of higher conductivity is achieved in portions of the mineral substrate. The temporarily ionized inclusions in the mineral substrate will have a substantially lower dielectric breakdown strength in comparison with, for example, non-ionized material surrounding the ionized inclusions, which means that the high voltage current pulse is more inclined to pass through the already and still ionized inclusions in the mineral substrate.

[0136] A pulsed power drill system that comprises an arrangement configured for generating and emitting microwave radiation in the mineral substrate to ionize the ionizable inclusions in the mineral substrate enable that the drill head with its electrodes may be positioned a longer distance from the mineral substrate to be drilled. Electrode wear as well as the risk for non-penetrating discharge between the electrodes can thereby be reduced, while the efficiency of the drilling process may be improved.

[0137] In embodiments, the solid electrode portion of at least one of the electrodes among the plurality of electrodes of the drill head is configured to be electrically connected to a microwave generator of the arrangement for generating and emitting microwave radiation. In embodiments, the solid electrode portion of the at least one electrode of the drill head may be configured to also function as a microwave antenna for emitting the microwave radiation generated by the microwave generator.

[0138] In embodiments, the solid electrode portion of at least a plurality of the electrodes of the drill head is configured to be electrically connected to their respective microwave generator of the arrangement for generating microwave radiation. Thus, , a first and a second electrode of the drill head may be associated with their own microwave generator for generating microwave radiation used for at least partly and temporarily ionizing the ionizable inclusions present in the mineral substrate.

[0139] In embodiments, a first and a second electrode of a drill head comprising at least two electrodes is connected to their respective microwave generator, for example their respective solid-state microwave generator, and is each configured to function as a microwave antenna used for transmitting microwave radiation generated by their respective microwave generator in the direction of the surface of the mineral substrate to be drilled. Both the first and the second electrode are then configured to be electrically connected to the pulsed power generator and to carry a discharge of a high voltage current pulse generated by the pulsed power generator. In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source and the control system is configured to control the pulsed power generator so that the high voltage electric pulse is generated within less than 10 milliseconds from at least a portion of the time interval of the pulse width of the microwave pulse generated by the device for generating microwave radiation, for example a predetermined time period that is less than 10 milliseconds.

[0140] In embodiments, the control system is configured to control the pulsed power generator and the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within less than 1 millisecond from at least a portion of the time interval of the pulse width of a microwave pulse generated by the device for generating microwave radiation, for example a predetermined time period that is less than 1 millisecond, where the microwave pulse is used for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations inside the mineral substrate.

[0141] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 50 nanoseconds and the control system is configured to control the pulsed power generator and the arrangement for generating and emitting microwave radiation so that the high voltage electric pulse is generated within less than 20 nanoseconds from at least a portion of the time interval of the pulse width of the microwave pulse, for example a predetermined time period that is less than 20 nanoseconds.

[0142] In embodiments, the pulsed power system comprises a waveguide configured for transporting, or carrying, the microwave radiation generated by the device for generating microwave radiation through the waveguide to the structure for emitting microwave radiation. In certain embodiments, the waveguide may be the same conductor as the conductor used for carrying the high voltage pulse.

[0143] In embodiments, at least portions of the free end of the structure for emitting microwave radiation is positioned at a distance to portions of the free end of each of the electrodes of the drill head that is substantially equal to or less than the mutual distance between the closest portions of the free ends of each pair of electrodes of the drill head. In embodiments, the device for generating microwave radiation comprises a circuit for generating microwave radiation and the arrangement for generating and emitting microwave radiation comprises a waveguide for carrying microwave radiation. In certain embodiments, the circuit for generating microwave radiation is connected to the waveguide for carrying microwave radiation and the waveguide for carrying microwave radiation is configured to carry or transport microwave radiation generated by the circuit to the structure for emitting microwave radiation.

[0144] In embodiments, the arrangement for generating and emitting microwave radiation comprises at least one microwave-transmissive device configured for positioning the focus point of the microwave radiation generated by the device for generating microwave radiation so that the focus point of the microwave radiation is in front of the drill head at a distance relative each of the electrodes of the drill head that is within the range 1 to 50 cm. The at least one microwave-transmissive device is then typically configured for positioning the focus point of the microwave radiation focus point inside the mineral substrate for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations inside the mineral substrate. In certain embodiments, the at least one microwave-transmissive device for positioning the focus point of the microwave radiation comprises at least one lens.

[0145] In aspects, the technology disclosed relates to a drill rig comprising a pulsed power drilling system according to any of the above-mentioned embodiments for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

[0146] In aspects, the technology disclosed relates to a method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by use of a pulsed power drilling system comprising a pulsed power generator and a drill head comprising a plurality of electrodes configured to be connected to the pulsed power generator, a control system comprising at least one control circuitry and configured for controlling the generation of a high voltage electric pulse by the pulsed power generator and an arrangement for generating and emitting microwave radiation comprising a device for generating microwave radiation and a structure for emitting microwave radiation, the method comprising: - generating, by means of the device for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside the mineral substrate to locally ionize at least a portion of the ionizable inclusions present in the mineral substrate;

[0147] - passing the generated microwave radiation to the structure for emitting microwave radiation;

[0148] - emitting, from the structure for emitting microwave radiation, the generated microwave radiation in the direction of the mineral substrate;

[0149] - generating, by use of the pulsed power generator and under the control of the control system, a high voltage electric pulse so that at least a portion of the microwave radiation is generated by the arrangement for generating and emitting microwave radiation prior to generating the high voltage electric pulse; and

[0150] - passing the generated high voltage electric pulse to two of the electrodes of the drill head, so as to allow passing of a high voltage current pulse between the two electrodes via already and still locally ionized portions of the ionizable inclusions present in the mineral substrate.

[0151] In embodiments, the method further comprising controlling, by the control system, the timing of the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within a time interval that is within less than 10 milliseconds from the generating of at least a portion of the generated microwave radiation, for example a predetermined time period that is less than 10 milliseconds.

[0152] In embodiments, the method further comprising controlling, by the control system, the timing of the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 1 milliseconds from the generating of at least a portion of the generated microwave radiation, for example a predetermined time period that is less than 1 millisecond.

[0153] In embodiments, the method further comprising controlling, by the control system, the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 20 nanoseconds from the generating of at least a portion of the generated microwave radiation, for example a predetermined time period that is less than 20 nanoseconds. In embodiments, the method further comprising controlling, by the control system, the generating of the high voltage electric pulse by the pulsed power generator so that the microwave radiation is generated by the device for generating microwave radiation prior to and during the generating of the high voltage electric pulse.

[0154] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 5 milliseconds and the method further comprising controlling, by the control system, the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated within less than 20 nanoseconds from the generating of at least a portion of the generated microwave radiation, for example a predetermined time period that is less than 20 nanoseconds.

[0155] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 5 milliseconds and the method further comprising controlling, by the control system, the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated during a portion of the time interval of the microwave pulse.

[0156] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 1 milliseconds and the method further comprising controlling, by the control system, the generating of the high voltage electric pulse by the pulsed power generator so that the high voltage electric pulse is generated during a portion of the time interval of the microwave pulse.

[0157] In embodiments, the step of generating microwave radiation may comprise generating microwave radiation having an average power within the range 50 W to 250 W.

[0158] In certain embodiments, the device for generating microwave radiation may be a continuous microwave radiation source that is constantly, or during a certain time period lasting at least a couple of seconds, turned on and that is configured to continuously generate microwave radiation having a constant or variable output power within the range 50 W to 500 W. In embodiments, the device for generating microwave radiation is a continuous microwave radiation source and the step of generating microwave radiation may comprise generating microwave radiation having an average power that is within the range 50 W to 500 W. In certain embodiments, the continuous microwave radiation source is then constantly, or during a certain time period lasting at least a couple of seconds, turned on and may then be configured to continuously generate microwave radiation having a constant or variable output power within the range 50 W to 500 W.

[0159] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source and the step of generating microwave radiation is comprising generating a microwave pulse having an average power over the pulse width that is within the range 50 W to 250 W.

[0160] In embodiments, the device for generating microwave radiation is a pulsed microwave radiation source configured to generate a microwave pulse having an average power over the pulse width that is within the range 200 W to 400 W. The step of generating microwave radiation may then comprise generating a microwave pulse having an average power over the pulse width that is within the range 50 W to 400 W

[0161] The pulsed power drilling system may further comprise a control system and a switching arrangement including at least one switch and the respective solid electrode portion of a plurality of electrodes of the drill head are arranged and configured to be electrically connected to a pulsed power generator of the pulsed power drilling system. The control system may then be configured to control the at least one switch to temporarily connect the solid electrode portion of the respective of two of the electrodes of the drill head to the pulsed generator to thereby allow for at least one high voltage current pulse to pass between the solid portions of the two electrodes. The control system may then be configured to control the at least one switch to temporarily connect the solid electrode portion of two of the electrodes of the drill head to the pulsed power generator.

[0162] In embodiments, the pulsed power drilling system may, in addition to a control system, further comprise a switching arrangement including at least one switch and the solid electrode portion of at least one of the plurality of electrodes of the drill head is arranged and configured to be functioning as a microwave antenna by being electrically connectable to a microwave generator of the arrangement for generating microwave radiation. The control system may then be configured to control the at least one switch to temporarily connect the solid electrode portion of one or two of the electrodes of the drill head to a microwave generator, e.g. their respective microwave generator, to thereby allow for emission of the microwave radiation in the mineral substrate. In example embodiments, at least one of the two electrodes, or solid electrode portions, is a coaxial cable configured to carry both microwave radiation and a high voltage electric pulse generated by the pulsed power generator. The free end of the coaxial cable may then be configured to function as a microwave antenna for emitting the generated micro wave radiation.

[0163] In certain embodiments, the pulsed power system comprises a pluralify of microwave generators and both the solid electrode portion of the first electrode and the solid electrode portion of the second electrode are configured to be connectable to their respective microwave generator. The control system of the pulsed power system may then be configured to control a switching arrangement and the opening and closing of at least one switch to control whether microwave radiation from the respective microwave generator is emitted in the mineral substrate.

[0164] In certain embodiments, both the solid electrode portion of the first electrode and the solid electrode portion of the second electrode are configured to be connectable to a common microwave generator. The control system of the pulsed power system may then be configured to control a switching arrangement to thereby control which of the solid electrode portions is currently transmitting the microwave radiation generated by the common microwave generator.

[0165] In embodiments, the pulsed power drilling system further comprises a control system and a switching arrangement including at least one switch and the solid electrode portion of at least one of the electrodes of the drill head is arranged and configured to be electrically connected to the circuit of the microwave generator. The method may then comprise the steps of:

[0166] - switching, under the control of the control system, at least one switch of the switching arrangement so that the solid electrode portion of at least one of a first and a second electrode of the drill head is electrically connected to a micro wave generator of the pulsed power drilling system;

[0167] - generating, by use of an arrangement for generating microwave radiation, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate to create localized ionizations in the mineral substrate;

[0168] - emitting the generated micro wave radiation in the mineral substrate;

[0169] - generating, by use of a pulsed power generator, a high voltage current pulse; and

[0170] - passing the high voltage current pulse between the solid electrode portion of the first electrode and a solid electrode portion of the second electrode of the drill head via the localized ionizations in the mineral substrate, wherein at least a portion of the generated microwave radiation is emitted in the mineral substrate prior to passing the high voltage current pulse between the solid electrode portion of the first electrode and a solid electrode portion of the second electrode via the already and temporarily localized ionizations in the mineral substrate.

[0171] The generation of the high voltage current pulse will create an at least partly ionized channel in the mineral substrate, via which channel the current pulse passes to the other electrode. In order for the current to pass between the electrodes, there has to be a difference in electric potential between the electrodes. In embodiments, the at least one pair of a first electrode and a second electrode may for this purpose comprise a positive electrode and a negative electrode, but it is also possible to, e.g., provide one positive or negative electrode and one electrode at zero potential. In embodiments, a plurality of the electrodes of the drill head are configured to have both a positive potential and a negative potential.

[0172] The arrangement for generating microwave radiation may each comprise a microwave generator including a circuit for generating microwave radiation. The circuit may then be connected to a waveguide configured to transport the microwave radiation generated by the circuit in the direction of the mineral substrate that is present in front of the solid electrode portion of the respective electrode, so as to allow the generated microwave radiation to be emitted in the mineral substrate.

[0173] The respective at least one arrangement for generating microwave radiation of a pulsed power drilling system comprising at least two electrodes may further comprise at least one microwave-transmissive device and / or aperture configured for positioning the focus point of the microwave radiation so that the focus point of the microwave radiation is in the fluid volume extending between the solid electrode portion of the respective at least one electrode and the surface of the mineral substrate. Thus, the at least one arrangement for generating and emitting microwave radiation may then comprise focusing means for positioning the focus point of the emitted microwave radiation. The focusing means may comprise at least one of an aperture and a microwave-transmissive device including at least one lens, typically a dielectric lens.

[0174] The respective of the at least one arrangement for generating and emitting microwave radiation may then comprise at least one microwave generator in the form of at least one of a magnetron, a solid-state microwave generator, a maser, travelling wave tubes and frequency multipliers.

[0175] The solid electrode portion of the respective at least one electrode among the plurality of electrodes of the drill head may then be further configured to also function as a waveguide for leading / transporting the microwave radiation generated by the respective at least one microwave generator to the fluid volume extending from the solid electrode portion of the respective at least one electrode to a surface of the mineral substrate. The at least one microwave generator may then be at least one of a magnetron, a solid-state microwave generator, a maser, travelling wave tubes and frequency multipliers.

[0176] In embodiments, the at least one arrangement for generating microwave radiation may include a circuit for generating microwave radiation, and, optionally, a waveguide configured to transport the microwave radiation generated by the circuit in the direction of the mineral substrate and at least one microwave-transmissive device or aperture configured for positioning the focus point of the microwave radiation. The circuit may then be arranged at a first end of a waveguide and a solid electrode portion of a first electrode is arranged at a second end of the waveguide so that the solid electrode portion is thereby arranged and configured to lead the microwave radiation to at least one microwave-transmissive device or aperture configured to position the focus point of the microwave radiation transported through the waveguide and then lead via the solid electrode portion so that the focus point of the microwave radiation is inside the mineral substrate.

[0177] Fig. 1 schematically illustrates an example embodiment of a pulsed power drilling system 100 configured for passing a pulsed electrical current through a mineral substrate 400 to break it. The pulsed power drilling system 100 in the embodiment shown in Fig. 1 comprises a pulsed power generator 110 schematically represented by a pulse transformer 112 in the form of a bank of capacitors and two electrodes 200, 200’, and an arrangement for generating and emitting microwave radiation 180.

[0178] The arrangement for generating and emitting micro wave radiation 180 illustrated in Fig. 1 comprises a microwave generator 181 including a circuit for generating microwave radiation 182. The circuit for generating microwave radiation 182 is connected to a waveguide 183 configured to transport the microwave radiation generated by the circuit 182 in the direction of the mineral substrate 400. The example embodiment of an arrangement for generating and emitting microwave radiation 180 shown in Fig. 1 further comprises an antenna structure for emitting microwave radiation 184 in the form of a microwave-transmissive device configured for positioning the focus point of the microwave radiation so that the focus point of the micro wave radiation is in the mineral substrate 400. The microwave radiation generated by the circuit for generating micro wave radiation 182 of the micro wave generator 181 is thereby emitted in the mineral substrate for the purpose of creating localized ionizations in the mineral substrate 400. As mentioned above, the microwave-transmissive device 184 in Fig. 1 is configured to function as an antenna structure for emitting microwave radiation 184 and comprises a lens 185 configured for positioning the focus point of the microwave radiation generated by the micro wave generator 181 in the mineral substrate 400.

[0179] Fig. 2 illustrates an example embodiment of a pulsed power drilling system 100 configured for passing a pulsed electrical current through a mineral substrate 400 to break it. The drilling tool 100 has a pulsed power generator 110 for generating high voltage current pulses, and a drill head 120 extending in an axial direction of the drilling tool 100 between a front end 121, configured to be positioned near or at a surface of the mineral substrate 400, and a rear end 122.

[0180] The pulsed power drilling system 100 in Fig. 2 comprises an arrangement for generating and emitting microwave radiation 180. The arrangement for generating and emitting micro wave radiation 180 includes a micro wave generator 181 comprising a circuit for generating microwave radiation 182. The circuit for generating microwave radiation 182 is connected to a waveguide 183 configured to transport the microwave radiation generated by the circuit 182 in the direction of an antenna structure for emitting microwave radiation 184. The microwave radiation generated by the circuit for generating micro wave radiation 182 is emitted in the mineral substrate 400 by the antenna structure for emitting microwave radiation 184. In this example embodiment, the antenna structure for emitting microwave radiation is a microwave-transmissive device 184 that is also configured for positioning the focus point of the microwave radiation generated by the microwave generator 180 in the mineral substrate 400.

[0181] The pulsed power generator 110 illustrated in Fig. 2 comprises a pulse transformer 112 in the form of a bank of capacitors, connected to an alternating current (AC) power supply 113 via a transformer and rectifier 111. Electrodes 200 and 200’ are selected and connected using switches 114 and 114’. By closing switches 114 and 114’, a short high voltage electric pulse that is generated by the pulsed power generator 110 is transferred to the electrodes 200 and 200’. The pulsed power generator is configured for generating pulses used for breaking the mineral substrate 400, such as nanosecond (ns) pulses to the electrodes 200 and 200’.

[0182] In Fig. 2, a pair of electrodes including a first electrode 200 and a second electrode 200’ are arranged at the front end 121 of the drill head 120, protruding slightly therefrom. The first and second electrodes 200, 200’ are electrically connectable to the pulsed power generator 110 by means of switches 114, 114’. This electrical connection to the pulsed power generator 110 is achieved by closing the respective switch 114, 114’. As the switches 114, 114’ are closed, a high voltage current pulse 150 passes between the first electrode 200 and the second electrode 200’ via the mineral substrate 400. As a result, a channel is formed in the mineral substrate 400 and the mineral substrate 400 is broken. Thus, as the switches 114, 114’ are closed, a high voltage current pulse 150 is allowed to pass between the electrodes 200, 200’ via already ionized inclusions present in the mineral substrate 400, where the inclusions are ionized by microwave radiation generated and emitted by the arrangement for generating and emitting microwave radiation 180.

[0183] The example embodiment of a pulsed power drilling system 100 illustrated in Fig. 2 further comprise a control unit 160 for controlling operation of the pulsed power drilling system 100 in response to signals received from an external control unit 170, such as a control unit of a machine, e.g. drill rig, in which the pulsed power drilling system is provided. The control unit 160 may include a microprocessor, a microcontroller, a programmable digital signal processor or another programmable device. Thus, control unit 160 comprises electronic circuits and connections (not shown) as well as processing circuitry (not shown) for communicating with different parts of the drilling tool 100 as well as with the external control unit 170. For example, the control unit 160 may be configured for communicating with various sensors, devices, systems and control units of the drilling tool 100. In the shown embodiment, the control unit 160 controls the transformer 111 as well as the switches 114, 114’. The example embodiment of a pulsed power drilling system 100 illustrated in Fig. 2 further comprises a fluid supply system 140 for supplying a shielding fluid, such as a flushing fluid, e.g., water, to a region between the drill head 120 and the mineral substrate 400 via a fluid conduit 141 having an outlet 142 located between the first and the second electrodes 200, 200’.

[0184] Fig. 3 illustrates an example embodiment of a pulsed power drilling system 100 configured for passing a pulsed electrical current through a mineral substrate 400 to break it. The pulsed power drilling system illustrated in Fig. 3 corresponds to the pulsed power drilling system illustrated in Fig. 3 with the difference that the solid electrode portions of the respective of the two electrodes 200, 200’ in Fig. 2 are replaced by the casings 186, 186’ of the antenna structure for emitting microwave radiation of the respective arrangement for generating and emitting microwave radiation 180, 180’. The respective arrangement for generating and emitting microwave radiation 180, 180’ in Fig. 3 each comprises a microwave generator 181, 181’ and is configured to emit micro wave radiation adapted for creating localized ionizations in the mineral substrate 400.

[0185] The casing 186, 186’ of the respective arrangement for generating microwave radiation 180, 180’ is configured to function as the solid electrode portion of the respective of the two electrodes 200, 200’ in that each of the casings 186, 186’ in Fig. 3 is electrically connectable to the pulsed power generator 110 by closing the respective switch 114, 114’. As the switches 114, 114’ are closed, a high voltage current pulse 150 is allowed to pass between the casings 186, 186’ of the respective arrangement for generating and emitting microwave radiation 180, 180’, functioning as a solid electrode portion of an electrode, via already localized ionizations in the mineral substrate 400. Hence, the casings 186, 186’ in Fig. 3 are configured to be connected to the pulsed power generator 110 to carry a discharge generated by the pulsed power generator 110 and, in addition, configured to be connected to their respective microwave generator 181 to function as an antenna for emitting the microwave radiation generated by the microwave generator 181 for creating localized ionizations in the mineral substrate prior to generating a high voltage electric pulse that allows for a high voltage current pulse to pass between the two casing via the already localized ionizations in the mineral substrate 400.

[0186] The example embodiment of a pulsed power drilling system 100 illustrated in Fig. 3 further comprise a control unit 160 for controlling operation of the pulsed power drilling system 100 in response to signals received from an external control unit 170, such as a control unit of a machine, e.g. drill rig, in which the pulsed power drilling system is provided. The control unit 160 may include a microprocessor, a microcontroller, a programmable digital signal processor or another programmable device. Thus, control unit 160 comprises electronic circuits and connections (not shown) as well as processing circuitry (not shown) for communicating with different parts of the drilling tool 100 as well as with the external control unit 170. For example, the control unit 160 may be configured for communicating with various sensors, devices, systems and control units of the drilling tool 100. In the shown embodiment, the control unit 160 controls the transformer 111 as well as the switches 114, 114’. The example embodiment of a pulsed power drilling system 100 illustrated in Fig. 3 further comprises a fluid supply system 140 for supplying a shielding fluid, such as a flushing fluid, e.g., water, to a region between the drill head 120 and the mineral substrate 400 via a fluid conduit 141 having an outlet 142 located between the first and the second electrodes 200, 200’.

[0187] Fig. 4 schematically illustrates an embodiment of a pulsed power drilling system 100 comprising two electrodes 200, 200’ and configured for passing a pulsed electrical current through a mineral substrate 400 to break it. The pulsed power drilling system in the embodiment shown in Fig. 4 comprises a pulsed power generator 110, which is schematically represented in Fig. 4 by a pulse transformer 112 in the form of a bank of capacitors and two electrodes 200, 200’, and two arrangements for generating and emitting microwave radiation 180, 180’, each comprising a microwave generator 181, 181’ each including a circuit for generating microwave radiation 182, 182’ that is connected to their respective microwave waveguide 183, 183’ which, in turn, is connected to their respective coaxial cable 187, 187’.

[0188] In the example embodiment illustrated in Fig. 4, each of the two electrodes 200, 200’ is a coaxial cable 187, 187’, or is part of their respective coaxial cable 187, 187’ that is functioning both as an antenna structure for emitting microwave radiation 184, 184’ in that each of the two electrodes 200, 200’ is electrically connectable to their respective device for generating microwave radiation 181, 181’ and to the pulsed power generator 110 for generating high voltage electric pulses. Each of the two coaxial cables 187, 187’ is then configured for carrying both a high voltage electric pulse generated by the device for generating high voltage electric pulses 110, or pulsed power generator 110, and micro wave radiation generated by their respective device for generating micro wave radiation 181, 181’. For example, each of the two coaxial cables 187, 187’ in Fig. 4 comprises an inner sub-structure functioning as an electrode 200, 200’ and an antenna structure for emitting microwave radiation 184, 184’ and is configured to carry microwave radiation adapted for creating localized ionizations in the mineral substrate and to carry a high voltage electric pulse applied to the electrodes 200, 200’, so as to as to allow a high voltage current pulse to pass between the two electrodes 200, 200’ via, by the microwave radiation generated by the two devices for generating microwave radiation 181, 181’, already and still localized ionizations in the mineral substrate 400.

[0189] The technology disclosed further relates to the use of a pulsed power drilling system according to any of the embodiments of a pulsed power drilling system shown in Figs. 1 to 4 for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

[0190] A method 500 for breaking a mineral substrate 400 by passing a pulsed electrical current through the mineral substrate 400 by means of any of embodiments of a pulsed power drilling system 100 described above in relation to Figs. 1 to 4 is illustrated in Fig. 5. The method 500 comprises the following actions:

[0191] 510: Generating, by a device for generating microwave radiation 181, microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate 400 to create localized ionizations in the mineral substrate 400;

[0192] 520: Passing the generated microwave radiation to an antenna structure for emitting microwave radiation 184;

[0193] 530: Emitting, from the antenna structure for emitting microwave radiation 184, the generated microwave radiation in the direction of the mineral substrate 400; 540: Generating, by a pulsed power generator 110, a high voltage electric pulse so that the high voltage electric pulse is generated after generation, by the device for generating micro wave radiation 181, of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate 400; and

[0194] 550: Passing the generated high voltage electric pulse to electrodes 200, 200’ of a drill head 120, so as to allow passing of a high voltage current pulse 150 between two electrodes 200, 200’ via already and still localized ionizations present in the mineral substrate 400.

[0195] Fig. 6 illustrates schematically a drill rig 600, or rock drilling machine 600, comprising a drilling system 100 as shown in any of Figs. 1 to 4, drilling a hole 401 in a mineral substrate 400 in the form of a rock. In Fig. 6, two electrodes 200, 200’ and the structure for emitting microwave radiation 184 is shown. The rock drilling machine 600 comprises the alternating current (AC) power supply 113 for powering the pulsed power generator 110. A hydraulic, pneumatic, or electrically actuated arm 610 for at least vertical positioning of the drilling tool 100 is provided, such as in response to signals from one or more position sensors (not shown) or similar sensing the distance between the electrodes and the mineral substrate surface. The rock drilling machine 600 further comprises ground engaging members 620 for moving the rock drilling machine 600 in a direction parallel with the rock 400.

[0196] It is to be understood that the present disclosure is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

CLAIMS1. A pulsed power drilling system ( 100) configured for passing a pulsed electrical current through a mineral substrate (400) to break the mineral substrate (400), the pulsed power drilling system (100) comprising:- a pulsed power generator (110) for generating high voltage electric pulses,- a drill head (120) comprising a plurality of electrodes (200, 200’) electrically connectable to the pulsed power generator (110), the pulsed power drilling system (100) is further comprising:- an arrangement for generating and emitting microwave radiation (180) comprising a device for generating micro wave radiation (181) and an antenna structure for emitting the microwave radiation ( 184) , wherein the pulsed power generator (110) is configured to generate a high voltage electric pulse after the generation of at least a portion of the microwave radiation generated by the device for generating micro wave radiation (181).

2. The pulsed power drilling system (100) according to claim 1, wherein the pulsed power generator ( 1 10) is configured so that the high voltage electric pulse is generated within less than 10 milliseconds from the generation of at least a portion of the micro wave radiation.

3. The pulsed power drilling system (100) according to any of claims 1 and 2, wherein the pulsed power generator ( 1 10) is configured so that the high voltage electric pulse is generated after and during the generation of at least a portion of the microwave radiation.

4. The pulsed power drilling system (100) according to any of the preceding claims, wherein the device for generating microwave radiation ( 181) is configured to generate microwave radiation having an average power within the range 50 W to 250 W.

5. The pulsed power drilling system (100) according to any of the preceding claims, wherein the device for generating microwave radiation ( 181) is a pulsed microwave radiation source providing a microwave pulse with a pulse width less than 5 milliseconds.

6. The pulsed power drilling system (100) according to claim 5, wherein the pulsed power drilling system (100) is further comprising a control system ( 160) and at least one switching arrangement ( 1 14, 1 14’), and wherein the control system ( 160) is configured to control the at least one switching arrangement ( 1 14, 1 14’) to thereby control at least one of the timing of the generation of the high voltage electric pulse by pulsed power generator ( 1 10) and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation ( 180) so that the high voltage electric pulse is generated within less than 10 milliseconds from at least a portion of the time interval of the pulse width of the micro wave pulse.

7. The pulsed power drilling system (100) according to claim 5, wherein the pulsed power drilling system (100) is further comprising a control system ( 160) and at least one switching arrangement ( 1 14, 1 14’), and wherein the control system ( 160) is configured to control the at least one switching arrangement ( 1 14, 1 14’) to control at least one of the timing of the generation of the high voltage electric pulse by the pulsed power generator ( 1 10) and the timing of the generation of the microwave radiation by the arrangement for generating and emitting microwave radiation ( 180) so that the microwave radiation is generated prior to and during the generation of the high voltage electric pulse.

8. The pulsed power drilling system (100) according to any of the preceding claims, wherein at least portions of the free end of the antenna structure for emitting microwave radiation ( 184) is positioned at a distance to portions of the free end of each of the electrodes (200, 200’) of the drill head (120) that is substantially equal to or less than the mutual distance between the closest portions of the free ends of each pair of electrodes (200, 200’) of the drill head (120).

9. The pulsed power drilling system (100) according to any of the preceding claims, wherein a free end of the antenna structure for emitting microwave radiation ( 184) is one of a solid electrode portion of one of the electrodes (200, 200’) functioning as a microwave antenna, an end portion of astructure for focusing microwave radiation generated by the device for generating microwave radiation (181) and an end portion of a waveguide (183) for carrying microwave radiation generated by the device for generating micro wave radiation (181).

10. The pulsed power drilling system (100) according to claim 9, wherein the free end of the structure for emitting microwave radiation (184) is a solid electrode portion of one of the electrodes (200, 200’) functioning as a microwave antenna, and wherein said solid electrode portion is electrically connectable to the device for generating microwave radiation ( 181).

11. The pulsed power drilling system (100) according to claim 9, wherein the free end of the structure for emitting microwave radiation ( 184) is a coaxial cable functioning as an electrode (200, 200’) and that is electrically connectable to both the device for generating microwave radiation ( 181) and the pulsed power generator (110), and wherein the coaxial cable is configured for carrying both the microwave radiation generated by the device for generating microwave radiation (181) and the high voltage electric pulse generated by the pulsed power generator ( 1 10).

12. The pulsed power drilling system (100) according to any of the preceding claims, wherein at least portions of the structure for emitting microwave radiation is at least partly made of an electrically non-conductive dielectric material.

13. The pulsed power drilling system (100) according to claim 9, wherein the arrangement for generating and emitting microwave radiation comprises at least one microwave-transmissive device configured for positioning the focus point of the microwave radiation generated by the device for generating microwave radiation (181) and emitted by the antenna structure for emitting microwave radiation (184) so that the focus point of the microwave radiation is in front of the drill head (120) at a distance relative each of the electrodes (200, 200’) of the drill head (120) that is within the range 1 to 50 cm.

14. The pulsed power drilling system (100) according to claim 13, wherein the at least one microwave-transmissive device for positioning the focus point of the microwave radiation comprises at least one lens (185).

15. A method (500) for breaking a mineral substrate (400) by passing a pulsed electrical current through the mineral substrate (400) by use of a pulsed power drilling system (100) comprising a pulsed power generator ( 1 10) and a drill head (120) comprising a plurality of electrodes (200, 200’) configured to be connected to the pulsed power generator ( 1 10), wherein the pulsed power drilling system (100) is further comprising an arrangement for generating microwave radiation (180) comprising a device for generating microwave radiation (181) and an antenna structure for emitting micro wave radiation ( 184), the method comprising:- generating (510), by the device for generating microwave radiation ( 181), microwave radiation adapted for affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate (400) to create localized ionizations in the mineral substrate (400);- passing (520) the generated microwave radiation to the antenna structure for emitting micro wave radiation (184);- emitting (530), from the antenna structure for emitting microwave radiation ( 184), the generated microwave radiation in the direction of the mineral substrate (400); and- generating (540), by the pulsed power generator ( 1 10), a high voltage electric pulse so that the high voltage electric pulse is generated after generation, by the device for generating micro wave radiation (181), of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside ionizable inclusions in the mineral substrate (400); and- passing (550) the generated high voltage electric pulse to two of the electrodes (200, 200’) of the drill head (120), so as to allow passing of a high voltage current pulse (150) between the two electrodes (200, 200’) via already and still localized ionizations present in the mineral substrate (400).

16. The method (500) according to claim 15, further comprising generating (540) the high voltage electric pulse by the pulsed power generator ( 1 10) so that the high voltage electric pulse is generated within less than 10 milliseconds from the generating of at least a portion of the generated microwave radiation affecting the electric field and electric charge distribution inside the ionizable inclusions in the mineral substrate (400).

17. The method (500) according to any of claims 15 and 16, further comprising generating (540) the high voltage electric pulse so that the high voltage electric pulse is generated by the pulsed power generator (110) after and during the generating of at least a portion of the microwave radiation affecting the electric field and electric charge distribution inside the ionizable inclusions in the mineral substrate (400).

18. The method according to any of claims 15 to 17, wherein the step of generating (510) microwave radiation is comprising generating microwave radiation having an average power within the range 50 W to 250 W.

19. A drill rig (600) comprising a pulsed power drilling system (100) according to any one of claims 1- 14 for breaking of a mineral substrate (400), such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

20. A computer program product comprising instructions, which when executed by a processor, causes the processor to perform the actions according to any one of claims 15 to 18.

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