A pulsed power drilling system and method for controlling activation of electrodes of a drill head

Abstract

The technology disclosed relates to a pulsed power drilling system, a drill rig comprising the pulsed power drilling system and methods for activating electrodes of a drill head of a pulsed power drilling system. In particular, the drill head comprises at least three electrodes and a control system of the pulsed power drilling system is configured to control a switching arrangement so that a pair of electrodes among the at least three electrodes are simultaneously connected to a pulsed power generator of the pulsed power drilling system. The disclosed pulsed power drilling system and methods 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 and the use of a pulsed power drilling system.

Description

[0001] TITLE

[0002] A pulsed power drilling system and method for controlling activation of electrodes of a drill head

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a pulsed power drilling system, a drill rig comprising the pulsed power drilling system and methods for activating electrodes of a drill head of a pulsed power drilling system. In particular, the drill head comprises at least three electrodes and a control system of the pulsed power drilling system is configured to control a switching arrangement so that a pair of electrodes among the at least three electrodes are simultaneously connected to a pulsed power generator of the pulsed power drilling system. The disclosed pulsed power drilling system and methods 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 and the use of a pulsed power drilling system.

[0005] BACKGROUND

[0006] 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 mechanical electrodes creating contact with a rock material, and the application of a high voltage between the electrodes.

[0007] Current rock drilling solutions typically use a passive array of electrodes, where the discharge will occur along the path of least resistance between the anode electrode and the cathode electrode. This random path is not necessarily the best path when it comes to rock destruction. For these solutions, it is not possible to control where the spark actually occurs. Moreover, it is also not possible to determine and / or control where the spark will occur, and maybe more importantly, it is not possible to determine and / or control where the spark should occur.

[0008] The current drilling process is typically “blind” and is not optimized for high- resolution drilling. Best case, some of the conventional pulsed power drilling tools may use rotating switches to provide more unform drilling over the rock surface and a broad overview of the rock mass may be obtained from previous long-distance investigations such as core drilling, but these conventional pulsed power drilling tools are typically not suitable for high resolution drilling or for more advanced methods for controlling the drilling process.

[0009] SUMMARY

[0010] In light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with conventional pulsed power drilling tools.

[0011] A primary object of the present disclosure is to achieve an in at least some aspects improved pulsed power drilling system adapted for better optimized drilling and high resolution drilling, including the possibility to discharge in patterns, and methods for achieving better optimized drilling and high resolution drilling, for example by making it possible to discharge where the most damage to the rock is done without causing any significant harm to the equipment.

[0012] The primary object is at least partly achieved by introducing a pulsed power drilling system that is adapted for better optimized drilling and high resolution drilling in that the pulsed power drilling system is configured to simultaneously activate a pair of electrodes among the at least three electrodes of the drill head during generation of a high voltage current pulse, for example with the purpose to discharge in patterns and / or to discharge where most damage to the rock is done. The pulsed power drilling system of the technology disclosed is thereby better adapted than conventional pulsed power drilling tools for more optimized drilling and / or high- resolution drilling by enabling better control of the drilling process, for example by controlling the activation of electrodes so that a discharge is carried between a pair of electrodes of the drill head where the most damage to the rock is done.

[0013] The activation, for example selective activation, of electrodes so that only pair of electrodes of the drill head, e.g., two of the electrodes of the drill head, are simultaneously connected to the pulsed power generator and that the other electrodes of the drill head are not connected to the pulsed power generator, also enables the possibility to discharge in pre-determined patterns, for example to create curving holes or particular hole shapes.

[0014] Other benefits include the prevention of usage of already damaged electrodes and the possibility to continue critical drilling with at least one of the electrodes being damaged, i.e., enabling so called “limp-mode”. In embodiments, the primary object is at least partly achieved by introducing a pulsed power drilling system that is adapted for more optimized drilling and high resolution drilling in that a control system of the pulsed power drilling system may be configured to obtain input data for determining which pair of electrodes among at least three electrodes of the drill head to be connected to the pulsed power generator during the generation of at least one high-voltage current pulse and then control a switching arrangement so that only the electrodes of the determined at least one pair of electrodes are connected to the pulsed power generator during the generation of the at least one high-voltage current pulse.

[0015] In certain embodiments, the primary object is at least partly achieved by introducing a pulsed power drilling system that is adapted for more optimized drilling an high resolution drilling in that the pulsed power drilling system may also be configured to obtain measurement data indicating properties of the mineral substrate to be drilled, for example by measuring the complex impedance between individual pair(s) of electrodes of the drill head, and then determine pair of electrodes to be selected for carrying a subsequent discharge at least partly based on the measurements. Thus, in embodiments of the technology disclosed, the primary object is at least partly achieved by configuring the pulsed power drilling system so that properties of the mineral substrate are measured by the pulsed power drilling system prior to the system generating a high voltage current pulse that is allowed to pass between two electrodes of the drill head via the mineral substrate to break the mineral substrate.

[0016] Yet another object of the present disclosure is 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.

[0017] In aspects, the technology disclosed relates to a pulsed power drilling system configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate, the drilling system comprising:

[0018] - a pulsed power generator for generating high voltage current pulses,

[0019] - a drill head comprising at least three electrodes each comprising a solid electrode portion and configured to be connected to the pulsed power generator,

[0020] - a switching arrangement comprising at least one switching circuit, and - a control system configured to control at least one switching circuit of the switching arrangement so that a pair of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator to thereby allow for a high voltage current pulse generated by the pulsed power generator to pass between the respective solid electrode portions of the two electrodes via the mineral substrate.

[0021] In embodiments, the control system is configured to control the switching arrangement so that a pair of electrodes are simultaneously connected to the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse and so that at least one of the other electrodes of the drill head is disconnected from the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse.

[0022] In aspects, the technology disclosed relates to a pulsed power drilling system configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate, the drilling system comprising:

[0023] - a pulsed power generator for generating high voltage current pulses,

[0024] - a drill head comprising at least three electrodes each comprising a solid electrode portion and configured to be connected to the pulsed power generator,

[0025] - a switching arrangement comprising at least one switching circuit, and

[0026] - a control system configured to control at least one switching circuit of the switching arrangement so that two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of at least one high voltage current pulse generated by the pulsed power generator whereas at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator during the generation of the at least one high voltage current pulse to thereby allow for the at least one high voltage current pulse to pass between the respective solid electrode portions of the two electrodes via the mineral substrate but not via the at least one other electrode of the drill head that is disconnected from the pulsed power generator. In embodiments, the control system is configured to control the at least one switching circuit of the switching arrangement so that only pairs of electrodes of the drill head, e.g., two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse.

[0027] In embodiments, the control system is configured to obtain input data and then control the at least one switching circuit at least partly based on the obtained input data.

[0028] In embodiments, the control system is configured to control activation of at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head.

[0029] In embodiments, the control system is further configured to selectively activate at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head by controlling the connection and disconnection of the at least three electrodes to and from the pulsed power generator via the at least one switching circuit of the switching arrangement.

[0030] In embodiments, the control system may be configured to obtain input data determining a pair of electrodes for carrying a discharge for at least one subsequent high-voltage pulse generated by the pulsed power generator and the control the switching arrangement so that only the determined at least one pair of electrodes for the respective at least one subsequent high-voltage pulse is connected to the pulsed power generator during the generating of the respective at least one subsequent high-voltage pulse. The input data may then determine the at least one pair of electrodes for each of a plurality of subsequent high-voltage pulses and the plurality of pairs of electrodes may together include at least three electrodes among the at least three electrodes of the drill head.

[0031] In embodiments, the control system may be configured to obtain measurement data indicating properties of the mineral substrate from a measurement system and determine or select a pair of electrodes for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data indicating properties of the mineral substrate.

[0032] In certain embodiments, the control system may be configured to obtain measurement data indicating properties of the mineral substrate, select a pair of electrodes among the at least three electrodes of the drill head for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data, and then control the at least one switching circuit of the switching arrangement so that the selected pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective at least one high voltage current pulse.

[0033] In aspects and embodiments, the technology disclosed relates to a method for breaking a mineral substrate where only a pair of electrodes among at least three electrodes of the drill head are connected to a pulsed power generator of the of the pulsed power drilling system during the generating of a high-voltage current pulse.

[0034] In embodiments, the drill head comprises at least three electrodes and the primary object is at least partly achieved by introducing a pulsed power drilling system that comprises a control system configured to control a switching arrangement so that two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of at least one high voltage current pulse generated by the pulsed power generator whereas at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator during the generation of the at least one high voltage current pulse to thereby allow for the at least one high voltage current pulse to pass between the respective solid electrode portions of the two electrodes via the mineral substrate but not via the at least one other electrode of the drill head that is disconnected from the pulsed power generator.

[0035] In embodiments, the drill head comprises at least five electrodes and the primary object is at least partly achieved by introducing a pulsed power drilling system that is adapted for more optimized drilling and high resolution drilling in that a control system of the pulsed power drilling system is configured to obtain input data for determining which at least one pair of electrodes among at least three electrodes of the drill head to be connected to the pulsed power generator during the generation of at least one high-voltage current pulse, and then control a switching arrangement so that the electrodes of the determined at least one pair of electrodes are connected to the pulsed power generator during the generation of the at least one high-voltage current pulse. In embodiments, the drill head comprises at least five electrodes and the primary object is at least partly achieved by introducing a pulsed power drilling system that is adapted for more optimized drilling and high resolution drilling in that a control system of the pulsed power drilling system may be configured to obtain input data for determining which at least one pair of electrodes among at least three electrodes of the drill head to be connected to the pulsed power generator during the generation of at least one high-voltage current pulse and which at least one of the electrode is disconnected from the to the pulsed power generator during the generation of at least one high-voltage current pulse, and then control a switching arrangement so that the electrodes of the determined at least one pair of electrodes are connected to the pulsed power generator during the generation of the at least one high-voltage current pulse and further so that the at least one of the electrode is disconnected from the to the pulsed power generator during the generation of at least one high-voltage current pulse.

[0036] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least three electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0037] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0038] - activating, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes so that the electrodes of the pair among the at least three electrodes are available for carrying a discharge generated by the pulsed power generator, and

[0039] - passing at least one high voltage current pulse between the solid electrode portions of the activated pair of electrodes via the mineral substrate.

[0040] The above step of activating may then comprise at least one of closing and opening, by the control system, at least one switch so that only the two electrodes of the activated pair of electrodes are available for carrying a discharge during the generation of the at least one high voltage current pulse whereas the remaining at least one electrode of the drill head is not available for carrying a discharge during the generation of the at least one high voltage current pulse.

[0041] In embodiments, the step of activating is comprising at least one of closing and opening, by the control system, at least one switching circuit so that two electrodes of the pair are available for carrying a discharge generated by the pulsed power generator whereas the remaining at least one electrode of the drill head is / are not available for carrying a discharge generated by the pulsed power generator.

[0042] In embodiments, the control system of the pulsed power drilling system is configured to obtain input data and the step of activating is comprising activating, for example selectively activating, the pair of electrodes based on input data obtained by the control system. The method may then comprise determining, by the control system, which pair of electrodes among at least three electrodes of a drill head to be activated based on input data obtained by the control system.

[0043] In embodiments, the method is further comprising: determining, by the control system, which pair of electrodes among the at least three electrodes to be activated and connected to the pulsed power generator at least partly based on the input data obtained by the control system.

[0044] In embodiments, the method is further comprising: obtaining, by the control system, input data prior to said step of activating the pair of electrodes, and the step of activating is comprising selectively activating, by the control system, the pair of electrodes at least partly based on the input data obtained by the control system.

[0045] In embodiments, the control system may then be configured to selectively activate at least two different pairs of electrodes including at least three electrodes of the drill head.

[0046] In embodiments, the control system is configured to obtain measurement data indicating properties of the mineral substrate and the step of activating is preceded by the step of: - determining, by the control system, which pair of electrodes to be activated and be connected to the pulsed power generator at least partly at least partly based on measurement data indicating properties of the mineral substrate.

[0047] In embodiments, the pulsed power drilling system comprises an arrangement for measuring properties of the mineral substrate, and the step of activating is preceded by the steps of: measuring, by the arrangement for measuring properties of the mineral substrate, properties of the mineral substrate, and determining, by the control system, which pair of electrodes among the at least three electrodes of the drill head to be activated and connected to the pulsed power generator during the generation of the at least one high voltage current pulse at least partly based on the measured properties of the mineral substrate.

[0048] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least three electrodes comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0049] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0050] - connecting, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes to the pulsed power generator,

[0051] - generating, by use of the pulse power generator, a high voltage current pulse, and

[0052] - passing the high voltage current pulse between the solid electrode portions of the activated pair of electrodes via the 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least three electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0053] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0054] - activating, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes so that the two electrodes of the pair are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator,

[0055] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein the at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and

[0056] - passing the at least one high voltage current pulse between the solid electrode portions of the pair of electrodes via the mineral substrate.

[0057] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least five electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0058] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate, - activating, by the control system controlling at least one switching circuit of the switching arrangement, at least one pair of electrodes among the at least three electrodes so that the two electrodes of the respective at least one pair of electrodes are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator,

[0059] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein the at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and

[0060] - passing at least one high voltage current pulse between the solid electrode portions of the at least one pair of electrodes via the mineral substrate.

[0061] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least five electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0062] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0063] - activating, by the control system controlling at least one switching circuit of the switching arrangement, one or two pairs of electrodes among the at least three electrodes so that the electrodes of the one or more pairs of electrodes are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one other electrode of the drill head is disconnected from the pulsed power generator,

[0064] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein the at least one other electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and - passing at least one high voltage current pulse among the at least one generated high voltage current pulse between the solid electrode portions of the one or more pairs of electrodes via the mineral substrate.

[0065] In aspects, the present disclosure relates to a drill rig comprising a pulsed power drilling system according to any of the embodiments mentioned above. The drill rig may then be configured for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

[0066] Advantages of the pulsed power drilling system and methods according to the technology disclosed include the provision of accurate and repetitious adjustments, right before drilling, so that proactive adjustments of the system including optimized and / or intelligent activation of pair of electrodes for carrying a subsequent discharge may be performed prior to generating a high voltage current pulse, thereby achieving more optimized drilling and / or high-resolution drilling.

[0067] As mentioned above, the benefits of the technology disclosed include the possibility to perform optimized and / or intelligent activation, for example selection, of pair of electrodes for carrying a subsequent discharge and to prevent parasitic discharge during charging of the high voltage circuit.

[0068] Further advantages and advantageous features of the disclosure are disclosed in the following description and in the dependent claims.

[0069] BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In the following, the technology disclosed will be described in detail, with reference to exemplifying embodiments and to the enclosed drawings.

[0071] In the drawings:

[0072] Fig. 1 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0073] Fig. 2 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure, Fig. 3 schematically illustrates a pulsed power drilling system according to an embodiment of the disclosure,

[0074] Fig. 4 is a flow-chart illustrating steps of a method according to an embodiment of the disclosure, and

[0075] Fig. 5 is a rock drilling machine, or drill rig, configured for comprising any of the pulsed power drilling system shown in Figs. 1, 2 and 3.

[0076] 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.

[0077] DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE DISCLOSURE

[0078] 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.

[0079] The present disclosure addresses at least some of the above-mentioned drawbacks associated with prior art pulsed power drilling tools by proposing a pulsed power drilling system comprising a drill head with at least three electrodes, a pulsed power generator, a control system and a switching arrangement, where the pulsed power drilling system is configured so that a pair of electrodes of the drill head are allowed to carry a discharge during the generation of a high-voltage pulse so as to allow the passing of the high-voltage current pulse between the pair of electrodes via a mineral substrate.

[0080] The basic concept of the invention is to provide a pulsed power drilling system with a drill head comprising at least three electrodes, and that is configured to control which pair of electrodes among the at least three electrodes that will carry a discharge, for example by use of a high voltage switching arrangement under the control of a control system.

[0081] According to the technology disclosed, one or more pairs of the at least three electrodes of the drill head are allowed to be simultaneously connected to the pulsed power generator while the other at least one electrode of the drill head is / are not connected to the pulsed power generator during the generation of a high voltage current pulse. A control system of the pulsed power drilling system may then be configured to control a switching arrangement so that different pairs of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of different high voltage pulses by the pulsed power generator so as to allow the passing of the respective high- voltage current pulse between the respective different pairs of electrodes via a mineral substrate.

[0082] Because only a pair of electrodes among at least three electrodes of the drill head are allowed to carry a discharge and at least one of the electrodes of the drill head is typically disconnected from the pulsed power generator during the generation of a high-voltage current pulse, the discharge will not always occur along the path of least resistance between the anode electrode and the cathode electrode. Since the path of least resistance is not necessarily the optimized best path, the pulsed power drilling system and methods for controlling the activation of electrodes according to the technology disclosed provide some advantages over conventional pulsed power drilling tools and previously used solutions when it comes to optimized rock destruction and high-resolution drilling.

[0083] In aspects, the technology disclosed relates to a pulsed power drilling system comprising a drill head with at least three electrodes and that is configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate, the drilling system comprising:

[0084] - a pulsed power generator for generating high voltage current pulses,

[0085] - a drill head comprising at least three electrodes each comprising a solid electrode portion and configured to be connected to the pulsed power generator,

[0086] - a switching arrangement comprising at least one switching circuit, and

[0087] - a control system configured to control at least one switching circuit of the switching arrangement so that pair of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator to thereby allow for a high voltage current pulse generated by the pulsed power generator to pass between the respective solid electrode portions of the two electrodes via the mineral substrate.

[0088] The advantages of the pulsed power drilling system and method according to technology disclosed include that the control system is configured to actively control which pair of electrodes among the at least three electrodes of a drill head that are allowed to be passing a high-voltage current pulse between them via a mineral substrate by controlling the switching arrangement so that one or more pairs of the electrodes of the drill head are simultaneously connected to the pulsed power generator and allowed to carry a discharge. The switching arrangement may then be configured for applying at least one of a positive and a negative potential to one or more of the electrodes of the drill head so that at least two electrodes among the at least three electrodes of the drill head may function both as an anode electrode and as a cathode electrode for the passing of a high voltage current pulse between a pair of electrodes via a mineral substrate, for example via at least one fluid volume and a mineral substrate.

[0089] In embodiments, the control system is configured to control a switching arrangement so that at least one pair of electrodes are simultaneously connected to the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse and so that at least one of the other electrodes of the drill head is disconnected from the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse.

[0090] In aspects, the technology disclosed relates to a pulsed power drilling system configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate, the drilling system comprising:

[0091] - a pulsed power generator for generating high voltage current pulses,

[0092] - a drill head comprising at least three electrodes each comprising a solid electrode portion and configured to be connected to the pulsed power generator,

[0093] - a switching arrangement, and - a control system configured to control the switching arrangement so that two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of at least one high voltage current pulse generated by the pulsed power generator whereas at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator during the generation of the at least one high voltage current pulse to thereby allow for the at least one high voltage current pulse to pass between the respective solid electrode portions of the two electrodes via the mineral substrate but not via the at least one other electrode of the drill head that is disconnected from the pulsed power generator.

[0094] In embodiments, the switching arrangement may then comprise at least one trigger logic device configured for applying a high voltage pulse to the pair of electrodes of the drill head determined to be connected to the pulsed power generator and carry a discharge during the generation of a high voltage current pulse. The control system of the pulsed power drilling system may then be configured to control the at least one trigger logic device of the switching arrangement so that only two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator to thereby allow for a high voltage current pulse generated by the pulsed power generator to pass between the two electrodes via at least the mineral substrate, for example via at least one fluid volume and a mineral substrate.

[0095] The at least one trigger logic may then apply a high voltage pulse to at least one of the electrodes. This causes a spark gap between a pair of the electrodes among the at least three electrodes of the drill head to conduct, creating a discharge between two electrodes. Once the spark is over, the spark gap stops conducting and the switching arrangement is ready for a new cycle. The new cycle that may then involve a different pair of electrodes of the drill head. The control system of the pulsed power drilling system may then be configured to control the at least one trigger logic device of the switching arrangement so that a different pair of electrodes among the at least three electrodes of the drill head may be simultaneously connected to the pulsed power generator during the new cycle.

[0096] In embodiments, the drill head comprises at least three electrodes and the control system and the switching arrangement may be configured to determine one or more pairs of electrodes to be activated for at least one high voltage current pulse to be generated so that the at least one high voltage current pulse may pass from any of at least three of the electrodes of the drill head determined by the control system to be the anode electrode for the at least one high voltage current pulse to any of the other electrodes among the at least three electrodes of the drill head determined by the control system to be the cathode electrode for the at least one high voltage current pulse via the mineral substrate, for example via at least one fluid volume and the mineral substrate.

[0097] In embodiments, the switching arrangement comprising at least one trigger logic may be configured to apply a high voltage pulse to at least a pair of the electrodes among the at least three electrodes of the drill head so that at the least two of the electrodes are configured to both function as an anode electrode and as a cathode electrode in a pair of electrodes for carrying a discharge and passing a high-voltage current pulse between them. In certain embodiments, the switching arrangement may then be configured to apply at least one of a positive potential and a negative potential to at least two of the at least three electrodes of the drill head to thereby allow for a high voltage current pulse to pass in both directions between each pair of electrodes including at least three different pairs of electrodes involving at least three electrodes among the at least three electrodes of the drill head, i.e. each electrode of the at least three different pairs of electrodes may then be arranged and configured to both function as a anode electrode and as a cathode electrode.

[0098] In embodiments, the control system may be configured to obtain input data used by the control system for determining a pair of electrodes for carrying a discharge for at least one high voltage current pulse to be generated. For example, the control system may be configured to determine which pair of electrodes among the at least three electrodes of the drill head for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained input data, and then control the switching arrangement so that the determined pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective high voltage current pulse.

[0099] In embodiments, the control system may be configured to obtain measurement data indicating properties of the mineral substrate where the measurement data is used for determining the pair of electrodes for carrying a discharge for at least one subsequent high voltage current pulse. For example, the control system may be configured to select a pair of electrodes among the at least three electrodes of the drill head for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data, and then control the at least one switching circuit of the switching arrangement so that the selected pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective high voltage current pulse.

[0100] In embodiments, the pulsed power drilling system comprises a measurement system. The control system may then be configured to obtain measurement data indicating properties of the mineral substrate from the measurement system and determine, for example select, a pair of electrodes for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data indicating properties of the mineral substrate.

[0101] In embodiments, the pulsed power drilling system comprises a pulsed power generator and a high-voltage supply to a switching arrangement which is controlled by a control system of the pulsed power drilling system. The switching arrangement may then be configured for applying a high voltage current pulse between a pair of electrodes among the at least three electrodes of the drill head in that only the pair of electrodes are simultaneously connected to the pulsed power generator during the generation and passing of a high voltage current pulse. The switching arrangement may then be configured so that at least one of a positive potential and a negative potential may be applied to at least one of a first electrode and a second electrode of the at least three electrodes of the drill head to thereby allow for a high voltage current pulse to pass both from the first electrode to the second electrode via the mineral substrate. The control system may then be configured to control the switching arrangement for connecting a pair of electrodes of the drill head to the pulsed power generator by first determining which of the electrodes in the pair is going to be the anode electrode and which of the electrodes in the pair is going to be the cathode electrode in the passing of a high voltage current pulse generated by the pulsed power generator. Hence, the control system and the switching arrangement are configured so that a high voltage current pulse may pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate and the control system is configured to determine which electrode is going to be the anode electrode and which electrode is going to be the cathode electrode. In embodiments, the pulsed power drilling system comprises a pulsed power generator and a high-voltage supply to a switching arrangement and is configured to apply a high voltage current pulse between two electrodes among the at least three electrodes of the drill head that are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse. The switching arrangement and the high-voltage supply are configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode, a second electrode and a third electrode of the at least three electrodes of the drill head so to allow for a high voltage current pulse to pass in any of two directions via the mineral substrate for at least two separate pairs of electrodes where the at least two separate pairs includes at least three of the electrodes among the at least three electrodes of the drill head. The control system may then be further configured to selectively control the switching arrangement for connecting a pair of electrodes of the drill head so that a high voltage current pulse generated by the pulsed power generator may pass in any of two directions via the mineral substrate for at least two separate pairs of electrodes where the at least two separate pairs include at least three of the electrodes among the at least three electrodes of the drill head.

[0102] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least three electrodes comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0103] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0104] - connecting, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes to the pulsed power generator,

[0105] - generating, by use of the pulse power generator, a high voltage current pulse, and

[0106] - passing the generated high voltage current pulse between the solid electrode portions of the pair of electrodes via the mineral substrate. In certain 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one trigger logic device, a pulsed power generator comprising a high-voltage supply to the switching arrangement and a drill head comprising at least three electrodes comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0107] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0108] - determining, by the control system, a pair of electrodes among the at least three electrodes to be simultaneously connected to the pulsed power generator during the generation and passing of at least one high voltage current pulse in that the other at least one electrode of the drill head is / are not allowed to be connected to the pulsed power generator during the generation and passing of the at least one high voltage current pulse,

[0109] - applying, under the control of the control system controlling the at least one trigger logic device of the switching arrangement and by use of the high- voltage supply, at least one high-voltage pulse to at least one of the electrodes of the pair of electrodes to thereby cause a spark gap to conduct and create a discharge between the solid electrode portions of the pair of electrodes so as to allow at least one high voltage current pulse to be passing between the pair of electrodes, and

[0110] - passing the at least one high voltage current pulse between the solid electrode portions of the pair of electrodes via the mineral substrate.

[0111] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement, a pulsed power generator and a drill head comprising at least three electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising: - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0112] - activating, by the control system controlling the switching arrangement, at least one pair of electrodes among the at least three electrodes so that the two electrodes of the at least one pair of electrodes are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one of the other at least one electrode of the drill head is disconnected from the pulsed power generator,

[0113] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein at least one other electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and

[0114] - passing the at least one high voltage current pulse between the solid electrode portions of the pair of electrodes via the mineral substrate.

[0115] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least five electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0116] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0117] - activating, by the control system controlling at least one switching circuit of the switching arrangement, one or two pairs of electrodes among the at least three electrodes so that the electrodes of the one or more pairs of electrodes are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one other electrode of the drill head is disconnected from the pulsed power generator,

[0118] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein the at least one other electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and

[0119] - passing at least one high voltage current pulse among the at least one generated high voltage current pulse between the solid electrode portions of the one or more pairs of electrodes via the mineral substrate.

[0120] 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 means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least five electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:

[0121] - positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,

[0122] - activating, by the control system controlling at least one switching circuit of the switching arrangement, at least two pairs of electrodes among the at least three electrodes so that the electrodes of the at least two pairs of electrodes are simultaneously connected to the pulsed power generator and available for carrying a discharge, wherein at least one other electrode of the drill head is disconnected from the pulsed power generator,

[0123] - generating, by the pulsed power generator, at least one high voltage current pulse, wherein the at least one other electrode of the drill head is disconnected from the pulsed power generator during the step of generating the at least one high voltage current pulse, and

[0124] - passing at least one high voltage current pulse between the solid electrode portions of the at least two pairs of electrodes via the mineral substrate.

[0125] The control system may be configured to obtain input data and then control the switching arrangement at least partly based on the obtained input data. The control system may then be configured to control the activation of at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head. In embodiments, the control system may be configured to selectively activate at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head by controlling the connection and disconnection of the at least three electrodes to and from the pulsed power generator via at least one switching circuit of the switching arrangement.

[0126] In embodiments, the pulsed power drilling system comprises a pulsed power generator with a high-voltage supply to a switching arrangement and is configured so that only two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse. The switching arrangement and the high-voltage supply may then be configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode and to a second electrode of the at least three electrodes of the drill head to thereby allow for a high voltage current pulse to pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate.

[0127] In embodiments, the control system may be further configured to selectively control the switching arrangement for connecting a pair of electrodes of the drill head so that a high voltage current pulse generated by the pulsed power generator may pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate.

[0128] In embodiments, the pulsed power drilling system comprises a pulsed power generator and a high-voltage supply to a switching arrangement and is configured so that only two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse. The switching arrangement and the high-voltage supply may then be configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode, a second electrode and a third electrode of the at least three electrodes of the drill head so to allow for a high voltage current pulse to pass in any of two directions via the mineral substrate for at least two separate pairs of electrodes where the at least two separate pairs include at least three of the electrodes among the at least three electrodes of the drill head. In embodiments, the control system is further configured to selectively control the switching arrangement for connecting a pair of electrodes of the drill head so that a high voltage current pulse generated by the pulsed power generator may pass in any of two directions via the mineral substrate for at least two separate pairs of electrodes where the at least two separate pairs include at least three of the electrodes among the at least three electrodes of the drill head.

[0129] In embodiments, the control system may be configured to obtain measurement data indicating properties of the mineral substrate, select a pair of electrodes among the at least three electrodes of the drill head for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data, and then control the switching arrangement so that the selected pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective high voltage current pulse.

[0130] In embodiments, the control system is configured to obtain measurement data indicating properties of the mineral substrate from the measurement system and select a pair of electrodes for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data indicating properties of the mineral substrate. The measurement data may then be obtained from an arrangement for measuring properties of a mineral substrate configured to perform at least one of complex impedance measurements between a pair of electrodes among the at least three electrodes and ground-penetrating measurements from receiving reflected waves of radar signals transmitted into the mineral substrate by the arrangement.

[0131] In an example embodiment, the arrangement for measuring properties of the mineral substrate may be configured to measure the complex impedance between at least two different pairs of electrodes of the drill head portions via the mineral substrate by temporarily applying a frequency-swept alternating voltage signal between the two electrodes of each of the two different pairs of electrodes and measuring the resulting current from applying the frequency-swept voltage signal. The control system may then be configured to control at least one switch of the switching arrangement to thereby control the activation of the electrodes so that only two of the electrodes among the at least three electrodes determined from the obtained measurement data to be activated are activated for a subsequent high voltage current pulse. In certain embodiments, the switching arrangement is a multi-pole switch and the control system is configured to control the activation of the pair of electrodes by controlling the multi-pole switch. In these embodiments using a multi-pole switch, the technology disclosed may be implemented in a setup that contains a series spark gap. This spark gap may be the same spark gap as needed in a multi-pole high voltage switch. In certain embodiments, also a grounding electrode can be used and switched under the control of the control system. In embodiments, initially neither of the spark gaps in the switch are conducting. During this time, complex impedance measurements may be conducted between any combinations of electrodes in contact with the rock, aiding the choice of best pair of electrodes. Once a suitable electrode pair is chosen, a trigger logic device may be used for applying a high voltage pulse to a chosen trigger electrode. This causes the spark gap between a high-voltage supply and the electrode to conduct, creating a powerful discharge between the rock in contact with the rock and ground. Once the spark is over, the spark gap stops conducting, and the multi-pole switch is ready for a new cycle.

[0132] However, a number of different embodiments of a switching arrangement may be used in connection with the technology disclosed, for example a switching arrangement that comprises a common ground electrode, or a switching arrangement configured for only switching the high voltage side between different electrodes. The switching arrangement may also be configured for alternating a ground electrode. Two separate high voltage switches are then typically required. One for high-voltage-to-electrode, and one for electrode-to-ground. This might require the ground electrode to be replaced by an opposite high-voltage potential.

[0133] The triggering of spark gaps may also be done in different ways. Pretty much any technology for ionizing the gap may be used, such as laser triggering, optical triggering and mentioned high-voltage triggering. Also, other types of switches could be considered, such as solid-state switches.

[0134] In example embodiments, the switching arrangement of the pulsed power drilling system may comprise a single-pole switch for each electrode of at least three electrodes of the drill head and the control system is configured to control the activation of the pair of electrodes by controlling each of the at least three singlepole switches. The switching arrangement may then be configured have a separate high voltage switch for each of at least three electrodes of the at least three electrodes of the drill head. This could either be realized with many single-pole switches, or by using a multipole high voltage switch similar to the distributor on a traditional gas engine. Such a device could either be mechanical or built up from controlled spark gaps.

[0135] 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 comprises a pulsed power generator 110 for generating high voltage current pulses, and a drill head

[0136] 120 extending in an axial direction of the pulsed power drilling system 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. In the example embodiment shown in Fig. 1, the drill head 120 comprises three electrodes 200, 200’, 200” arranged at the front end

[0137] 121 of the drill head 120, protruding slightly therefrom.

[0138] The pulsed power generator 110 illustrated in Fig. 1 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 111. The pulsed power generator 110 comprises a circuit (not shown) for generating high voltage current pulses 150 and each of the three electrodes 200, 200’, 200” of the drill head 120 may be connected to the pulsed power generator 110 by closing their respective switches 114, 114’, 114”. The three electrodes in the example embodiment of a pulsed power drilling system 100 shown in Fig. 1 are in direct contact with the mineral substrate, or rock mass. Fig. 1 shows the temporary closing of two of the three switches 114, 114’, 114” under the control of a control system 160, so as to allow a short high voltage pulse 150 generated by the pulsed power generator 110 to only be transferred to two of the electrodes 200, 200’. The pulsed power generator 110 shown in Fig. 1 is configured for generating pulses 150 used for breaking the mineral substrate 400, such as nanosecond (ns) pulses to two of the three electrodes 200, 200’, 200” of the dill head 120.

[0139] Hence, only two of the three electrodes 200, 200’, 200” may be simultaneously connected to the pulsed power generator 110 by means of their respective switches 114, 114’, 114”. In Fig. 1, two of the switches 114, 114” are temporarily closed under the control of the control system 160, thereby temporarily connecting two of the electrodes 200, 200” to the pulsed power generator 110 so as to allow a high- voltage current pulse 150 generated by the pulsed power generator 110 to pass between the two electrodes 200, 200”. This is achieved by connecting the first electrode 200, temporarily functioning as an anode electrode for a high-voltage current pulse, to the pulsed power generator 110 by closing the switch 114, so that a high voltage current pulse 150 generated by the circuit of the pulsed power generator 110 may pass to the first electrode 200, where a discharge is formed between the first electrode 200 and the mineral substrate 400. As two of the switches 114, 114” are temporarily closed in Fig. 1, the high voltage current pulse passes between the electrode to the left in Fig. 1 200 and the electrode to the right 200”, functioning as a cathode electrode for the pulse 150, via the mineral substrate 400. As a result, a channel is formed in the mineral substrate 400 and the mineral substrate 400 is broken. The third switch 114’ in Fig. 1 is temporarily open so the electrode in the middle 200’ in Fig. 1 is temporarily disconnected from the pulsed power generator 110. The electrode in the middle 200’ is thereby not allowed to carry a discharge and no high-voltage current pulse 150 generated by the pulsed power generator 110 is allowed to pass between the electrode in the middle 200’ and any of the other two electrodes 200, 200” via the mineral substrate 400.

[0140] The control system 160 in Fig. 1 is configured to control 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 system 160 may include a microprocessor, a microcontroller, a programmable digital signal processor or another programmable device. Thus, the control system 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 system 160 may be configured for communicating with various sensors, devices, systems and control units of the pulsed power drilling system 100. In the embodiment shown in Fig. 1, the control system 160 controls the opening and closing of the switches 114, 114’, 114” to thereby connect and disconnect different pairs of the three electrodes 200, 200’, 200” to the pulsed power generator 110 so that the different pairs of electrodes can carry a discharge and pass a high-voltage current pulse between them via the mineral substrate 400.

[0141] The control system 160 may comprise modules in either hardware or software, or partially in hardware or software, and communicate using known transmission buses such a CAN-bus and / or wireless communication capabilities. The processing circuitry may be a general-purpose processor or a specific processor. The control system 160 may comprise a non-transitory memory for storing computer program code and data. Thus, the skilled person realizes that the electronic control system 160 may be embodied by many different constructions.

[0142] The electrodes 200, 200’, 200” each typically comprises a solid electrode portion (not shown) arranged at a front end of the electrode 200. The solid electrode portion may be made at least partially of electrically conductive material and may be either metallic or ceramic.

[0143] The example embodiment of a pulsed power drilling system 100 illustrated in Fig. 1 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 middle electrode 200’ and the electrode to the right 200”. The flushing fluid is used for isolating any possible first fluid volume extending from the solid electrode portion of the middle electrode 200’ to the mineral substrate 400 from any possible second fluid volume extending from the solid electrode portion of the electrode to the right 200” to the mineral substrate 400. The same type of pulsed power drilling system 100 according to other embodiments of the technology disclosed may be configured to use a combination of electrodes arranged around a perimeter of the drill head 120 and the outlet 142 of the shielding fluid conduit 141 may then by way of example be positioned at a center of the drill head 120, but a variety of different configurations are possible.

[0144] Fig. 2 schematically illustrates an embodiment of a pulsed power drilling system 100 configured for passing a pulsed electrical current 150 through a mineral substrate 400 to break it. The pulsed power drilling system in the embodiment shown in Fig. 2 comprises a pulsed power generator 110, which is schematically represented in Fig. 2 by a pulse transformer 112 in the form of a bank of capacitors, and three electrodes 200, 200’, 200”.

[0145] The pulsed power drilling system 100 schematically illustrated in Fig. 2 is configured so that two of the electrodes among the three electrodes 200, 200’, 200” may be simultaneously connected to the pulsed power generator 110 via their respective switches 114, 114’, 114”. Each of the three electrodes 200, 200’, 200” of the drill head 120 may be connected to the pulsed power generator 110 by closing their respective switches 114, 114’, 114” under the control of a control system 160. Fig. 2 illustrates the temporary closing of two of the three switches 114, 114’, 114” under the control of the control system 160, so as to allow a short high voltage pulse 150 generated by the pulsed power generator 110 to only be transferred to two of the electrodes among the three electrodes 200, 200’, 200” determined to carry a discharge. The opening and closing of each of the three switches 114, 114’, 114” in Fig. 2 is thus controlled by the control system 160, thereby determining whether the respective electrode 200, 200’, 200” is connected to or disconnected from the pulsed power generator 110.

[0146] The three electrodes 200, 200’, 200” in the example embodiment of a pulsed power drilling system 100 shown in Fig. 2 are all in direct contact with the mineral substrate 400, or rock mass. However, in other usage of the pulsed power drilling system shown in Fig. 2, a fluid volume may be present between at least one of the two the electrodes 200, 200’, 200” and the mineral substrate 400 during the generation and passing of a high-voltage current pulse 150 between two electrodes via the mineral substrate 400. The generated high-voltage current pulse 150 for breaking the mineral substrate may then be passing between two of the three electrodes 200, 200’, 200” via both the mineral substrate and the at least one fluid volume.

[0147] Fig. 3 schematically illustrates an 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 in the embodiment shown in Fig. 3 comprises a pulsed power generator 110, which is schematically represented in Fig. 3 by a pulse transformer 112 in the form of a bank of capacitors, three electrodes 200, 200’, 200” and a measurement system 190.

[0148] The pulsed power drilling system 100 in Fig. 3 further comprises a measurement system 190. In measurement mode, the measurement system 190 is temporarily connected simultaneously to two of the three electrodes 200’, 200”, 200”, in that the two electrodes are temporarily functioning as measurement electrodes. Thus, each of three electrodes 200, 200’, 200” in Fig. 3 may temporarily be connected to a second circuit (not shown) of the measurement system 190.

[0149] The pulsed power drilling system 100 shown in Fig. 3 is configured so that two of the electrodes among the three electrodes 200, 200’, 200” may be simultaneously connected to a first circuit (not shown) of the pulsed power generator 110 via their respective switches 114, 114’, 114”. The opening and closing of each of the three switches 114, 114’, 114” in Fig. 3 is controlled by the control system 160, thereby determining whether the respective electrode 200, 200’, 200” is connected to or disconnected from the pulsed power generator 110.

[0150] The pulsed power drilling system 100 shown in Fig. 3 is configured so that two of the electrodes among the three electrodes 200, 200’, 200” may be simultaneously connected to a second circuit (not shown) of the measurement system 190 via their respective switches 115, 115’, 115”. The opening and closing of each of the three switches 115, 115’, 115” in Fig. 3 is controlled by the control system 160.

[0151] In the embodiments shown in Fig. 3, the electrodes 200, 200’, 200” are configured to be connected to a first circuit (not shown) of the pulsed power generator 110 via their respective switches 114 114’, 114” (the switches 114, 114’ and 114” in Fig. 3 are temporarily open so none of the electrodes 200, 200’, 200” illustrated in Fig. 3 are currently connected to the pulsed power generator 110. The three electrodes 200, 200’, 200” shown in Fig. 3 are further configured to each be connected to the measurement system 190 via their respective switches 115, 115’ and 115”. The measurement system 190 comprises a second circuit (not shown) configured to supply a frequency-swept voltage signal that is applied between two of the electrodes 200, 200’, 200” that are simultaneously and temporarily connected to the measurement system 190 for measuring the complex impedance between two of the three electrodes 200, 200’, 200”. The resulting current from the applied frequency-swept voltage signal is measured / obtained by the measurement system 190. The measurement system 190 is configured to determine the complex impedance from the current resulting from the applied frequency-swept voltage signal to thereby, in turn, determine properties of the mineral substrate 400 to be drilled.

[0152] In measurement mode, the three electrodes 200, 200’, 200” in the example embodiment of a pulsed power drilling system 100 shown in Fig. 3 may typically all be in direct contact with the mineral substrate 400, or rock mass, and are thereby each positioned to function as a measurement electrode used for measurement purpose by closing their respective switch 115, 115’, 115” to be connected to the measurement system 190. In the example embodiment of a pulsed power drilling system 100 illustrated in Fig. 3, two of the three electrodes (the electrode in the middle 200’ and the electrode to the right 200”) of the drill head 120 are temporarily connected to the measurement system 190 (but not to the pulsed power generator 110 since pulsed power drilling system is in measurement mode) via the closing of their respective switches 115’, 115”, whereas the third electrode to the left 200 is neither connected to the pulsed power generator 110 nor to the measurement system 190 (both the switch 114 and the switch 115 are temporarily open in Fig. 3). Since the switches 115’ and 115” are temporarily closed in Fig. 3, a frequency- swept voltage signal generated by the second circuit of the measurement system 190 is allowed to be applied between the two electrodes 200’, 200” via the mineral substrate 400.

[0153] The control system 160 in Fig. 3 is further configured to also control the opening and closing of switches 115, 115’, 115” to thereby control which pair of electrodes 200, 200’, 200” are simultaneously connected to the measurement system 190 so that the frequency-swept voltage signal may be temporarily applied between two of the electrodes 200, 200’, 200”. Each of the two electrodes 200, 200’, 200” may not be simultaneously connected to both the first circuit of the pulsed power generator 110 and the second circuit of the measurement system 190. The resulting current from the applied frequency- swept voltage signal is used by the measurement system 190 to determine the complex impedance from the current resulting from the applied frequency-swept voltage signal to thereby, in turn, determine properties of the mineral substrate 400 to be drilled.

[0154] In Fig. 3, the pulsed power drilling system 100 is currently in measurement mode and both the middle electrode 200’ and the electrode to the right 200” are currently connected to the measurement system 190 via the closing of their respective switches 115’, 115” so as to allow them to temporarily function as measurement electrodes. The middle electrode 200’ and the electrode to the right 200” are not currently connected to the pulsed power generator 110. The electrode to the left 200 is neither connected to the pulsed power generator 110 nor to the measurement system 190.

[0155] 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 3 for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining. An example method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by means of any of embodiments of a pulsed power drilling system is illustrated in Fig. 4. The method comprises the following actions / steps:

[0156] 410: Position drill head, i.e., positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate;

[0157] 420: Activate pair of electrodes, i.e., activating, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes so that only the two electrodes of the pair among the at least three electrodes are available for carrying a discharge;

[0158] 430: Generate high voltage (HV) current pulse, i.e., generating, by the pulsed power generator, at least one high voltage current pulse; and

[0159] 440: Pass pulse between electrodes, i.e., passing the at least one high voltage current pulse between the solid electrode portions of the activated pair of electrodes via the mineral substrate.

[0160] Fig. 5 illustrates schematically a drill rig 500, or rock drilling machine, comprising a pulsed power drilling system 100 as shown in any of Figs. 1 to 3, drilling a hole 401 in a mineral substrate 400 in the form of a rock. The drill rig 500 comprises the alternating current (AC) power supply 113 for powering the pulsed power generator 110. It further comprises the compressed gas supply system 130 and the fluid supply system 140. A hydraulic, pneumatic, or electrically actuated arm 510 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 drill rig 500 further comprises ground engaging members 520 for moving the drill rig 500 in a direction parallel with the rock 400.

[0161] 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 configured for passing a pulsed electrical current through a mineral substrate to break the mineral substrate, the drilling system comprising:- a pulsed power generator for generating high voltage current pulses,- a drill head comprising at least three electrodes each comprising a solid electrode portion and configured to be connected to the pulsed power generator,- a switching arrangement comprising at least one switching circuit, and- a control system configured to control at least one switching circuit of the switching arrangement so that a pair of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator to thereby allow for a high voltage current pulse generated by the pulsed power generator to pass between the respective solid electrode portions of the two electrodes via the mineral substrate.

2. The pulsed power drilling system according to claim 1, wherein the control system is further configured to control the at least one switching circuit of the switching arrangement so that the pair of electrodes are simultaneously connected to the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse and so that at least one of the other electrodes of the drill head is disconnected from the pulsed power generator during the generation of the respective at least one subsequent high voltage current pulse.

3. The pulsed power drilling system according to any of claims 1 and 2, wherein the control system is further configured to obtain input data and then control the at least one switching circuit at least partly based on the obtained input data.

4. The pulsed power drilling system according to any of claims 1 to 3, wherein the control system is further configured to control activation of at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head.

5. The pulsed power drilling system according to any of claims 1 to 4, wherein the control system is further configured to selectively activate at least two different pairs of electrodes including at least three electrodes among the at least three electrodes of the drill head by controlling the connection and disconnection of the at least three electrodes to and from the pulsed power generator via the at least one switching circuit of the switching arrangement.

6. The pulsed power drilling system according to any of claims 1 to 5, wherein the pulsed power drilling system comprises a pulsed power generator providing a high-voltage supply to the switching arrangement and where the switching arrangement is configured so that only two electrodes among said pair of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse, and wherein the switching arrangement is further configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode and to a second electrode of the at least three electrodes of the drill head to thereby allow for a high voltage current pulse to pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate.

7. The pulsed power drilling system according to claim 6, wherein the control system is further configured to selectively control the switching arrangement for connecting a pair of electrodes of the drill head so that a high voltage current pulse generated by the pulsed power generator may pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate.

8. The pulsed power drilling system according to any of claims 1 to 5, wherein the switching arrangement is configured so that only two electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse, and wherein the switching arrangement is further configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode, a second electrode and a third electrode of the at least three electrodes of the drill head so to allow for a high voltage current pulse to pass in any of two directions via the mineral substrate for atleast two separate pairs of electrodes where the at least two separate pairs includes at least three of the electrodes among the at least three electrodes of the drill head.

9. The pulsed power drilling system according to claim 8, wherein the control system is further configured to selectively control the switching arrangement for connecting a pair of electrodes of the drill head so that a high voltage current pulse generated by the pulsed power generator may pass in any of two directions via the mineral substrate for at least two separate pairs of electrodes where the at least two separate pairs includes at least three of the electrodes among the at least three electrodes of the drill head.

10. The pulsed power drilling system according to any of claims 1 to 9, wherein the control system is further configured to obtain measurement data indicating properties of the mineral substrate, select a pair of electrodes among the at least three electrodes of the drill head for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data, and then control the at least one switching circuit of the switching arrangement so that the selected pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective at least one subsequent high voltage current pulse.

11. The pulsed power drilling system according to any of claims 1 to 10, wherein the pulsed power drilling system comprises a measurement system, and wherein the control system is configured to obtain measurement data indicating properties of the mineral substrate from the measurement system, select a pair of electrodes for carrying a discharge for at least one subsequent high voltage current pulse at least partly based on the obtained measurement data indicating properties of the mineral substrate, and then control the at least one switching circuit of the switching arrangement so that the selected pair of electrodes for the respective at least one subsequent high voltage current pulse is connected to the pulsed power generator during generation of the respective at least one subsequent high voltage current pulse.

12. A method for breaking a mineral substrate by passing a pulsed electrical current through the mineral substrate by means of a pulsed power drilling system comprising a control system, a switching arrangement including at least one switching circuit, a pulsed power generator and a drill head comprising at least three electrodes each comprising a solid electrode portion configured to be connected to the pulsed power generator and to carry a discharge generated by the pulsed power generator, the method comprising:- positioning the drill head so that the solid electrode portions of the at least three electrodes are at least in proximity of a surface of the mineral substrate,- activating, by the control system controlling at least one switching circuit of the switching arrangement, a pair of electrodes among the at least three electrodes so that electrodes of the activated pair among the at least three electrodes are available for carrying a discharge,- generating, by the pulsed power generator, at least one high voltage current pulse, and- passing the at least one high voltage current pulse between the solid electrode portions of the activated pair of electrodes via the mineral substrate.

13. The method according to claim 12, wherein said step of activating is comprising at least one of closing and opening, by the control system, at least one switch so that electrodes of the activated pair of electrodes are available for carrying a discharge during the generation of the at least one high voltage current pulse, whereas the remaining at least one electrode of the drill head is not available for carrying a discharge during the generation of the at least one high voltage current pulse.

14. The method according to any of claims 12 and 13, said method further comprising:- obtaining, by the control system, input data prior to said step of activating the pair of electrodes, and wherein said step of activating is comprising selectively activating, by the control system, the pair of electrodes at least partly based on the input data obtained by the control system.

15. The method according to claim 14, wherein said method is further comprising determining, by the control system, which pair of electrodes among the at least three electrodes to be activated and connected to the pulsed power generator at least partly based on the input data obtained by the control system.

16. The method according to any of claims 12 to 15, wherein the switching arrangement is configured so that only pairs of electrodes among the at least three electrodes of the drill head are simultaneously connected to the pulsed power generator during the generation of a high voltage current pulse, and wherein the switching arrangement is further configured so that at least two of a positive potential, a negative potential and ground may be applied to at least a first electrode and to a second electrode of the at least three electrodes of the drill head to thereby allow for a high voltage current pulse to pass both from the first electrode to the second electrode via the mineral substrate and from the second electrode to the first electrode via the mineral substrate, said method further comprising: applying, under the control of the control system controlling the switching arrangement and by use of a high-voltage supply from the pulsed power generator, two different potentials to the two electrodes of the pair of electrodes including at least two of a positive potential, a negative potential and ground to thereby selectively controlling, by the control system, that a high voltage current pulse is passing from the first electrode to the second electrode of the pair of electrodes via the mineral substrate and not from the second electrode to the first electrode via the mineral substrate, or vice versa.

17. The method according to any of claims 12 to 16, said control system is configured to obtain measurement data indicating properties of the mineral substrate and said step of activating is preceded by the step of: determining, by the control system, which pair of electrodes to be activated and be connected to the pulsed power generator at least partly at least partly based on measurement data indicating properties of the mineral substrate.

18. The method according to claim any of claims 12 to 17, wherein the pulsed power drilling system comprises an arrangement for measuring properties of the mineral substrate, and said method is further comprising: measuring, by the arrangement for measuring properties of the mineral substrate, properties of the mineral substrate, wherein said step of activating is preceded by the step of: determining, by the control system, which pair of electrodes among the at least three electrodes of the drill head to be activated and connected to the pulsed power generator during the generation of the at least one high voltage current pulse at least partly based on the measured properties of the mineral substrate.

19. Use of a pulsed power drilling system according to any one of claims 1-11 for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

20. A drill rig comprising a pulsed power drilling system according to any one of claims 1- 11 for breaking of a mineral substrate, such as in any one of rock drilling, concrete processing, mineral processing, and continuous mining.

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