A method for testing an electrical circuit of a trolley-assist system for mining vehicles

Abstract

A trolley assist system for mining vehicles comprises at least one power distribution unit configured to receive electrical power from a source of electrical energy and provide electrical power to an

Description

Technical Field The present disclosure relates to a method for testing an electrical circuit of a trolley-assist system for mining vehicles. In particular, the present disclosure relates to a method whereby a testing protocol is initiated at a first test voltage and, during use, the electrical circuit is monitored at a second voltage; the second voltage is greater than the first voltage. The present disclosure also relates a test system for a trolley-assist system for mining vehicles. Background A trolley-assist system is a system in which mining vehicles or haul trucks, in open pit mines, are propelled, or assisted, by electrical power or energy along a mining vehicle haul road. This is known to be advantageous because the use of electrical power leads to high savings on fuel costs and reduced CO2 emissions in comparison to well-known systems that may use diesel fuel. It is known that electrical power is provided to trolley-assist systems using power distribution units, otherwise known as trolley substations. Trolley substations are prefabricated structures that house electrical equipment and control systems. Although these known trolley-assist systems are advantageous with regards to reducing diesel consumption, they do have associated safety risks. For example, high-voltage electrical equipment is housed within the trolley substation, therefore, if there is a fault in the electrical circuit this can lead to significant damage to the system or even to technicians working within the trolley substation or elsewhere on the trolley-assist system. Due to these safety and damage risks, it is known in the prior art that there is a need to test the trolley-assist system. In the prior art, the system is energised and may be monitored for a fault. A part of the system may be shut down once a fault has occurred. However, the present inventors have appreciated that energising the system and subsequently detecting faults can lead to damage to the system or even to a technician who has activated the system. Further, in the known prior art, even if the trolley substation is shut down in response to a voltage spike, for example, technicians are only aware of the trolley substation being shut down upon physical inspection of the system. This is an inefficient process, with regards to time and resources. Further, it presents a potential safety risk to the technician who has to inspect the system in person. The present inventors have appreciated that there is a need to improve the safety of technicians working on trolley substation for trolley-assist systems. Further still, in known prior art systems, a trolley-assist system which has an overhead power cable exceeding a certain length often comprises a plurality of independent trolley substations to power the overhead cable along the whole length. Each trolley substation is configured to provide electrical power for a portion of the system. Each trolley substation may be configured to provide electrical power to a specific section of the overhead power cable. Each trolley substation can provide power to a certain number of trucks at a time. Therefore, because the trolley substations are independent, the mining vehicles or trucks have to disconnect and the reconnect as they move from one portion or section of the overhead power cable powered by a first trolley substation to a different portion or section of the overhead power cable powered by a second trolley substation. The present inventors have appreciated that there is a need to provide a more efficient process. In summary, the present inventors have appreciated that it would be desirable to be able to provide a method for testing an electrical circuit of a trolley-assist system for mining vehicles with efficiency and safety improvements over the known prior art. Summary of the Disclosure Examples described herein provide a method for testing an electrical circuit of a trolley-assist system for mining vehicles and a test system for a trolley-assist system for mining vehicles as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the disclosure are set out in the dependent subclaims. According to a first aspect of the present disclosure, there is provided a method for testing an electrical circuit of a trolley-assist system for mining vehicles. The trolley assist system comprises at least one power distribution unit configured to receive electrical power from a source of electrical energy and provide electrical power to an overhead power cable. The method comprises initiating a testing protocol at a first test voltage. Where, upon determining that there is no fault in the electrical circuit, energising the or each at least one power distribution unit and monitoring the electrical circuit at a second voltage. The second voltage being greater than the first voltage. Upon detecting at least one fault, the method comprises de-energising the or each at least one power distribution unit. The method according to the first aspect advantageously provides a lower-voltage test circuit which can be used to determine the integrity and safety of the trolley-assist system before energising and / or re-energising the at least one power distribution unit. Therefore, advantageously, and unlike the prior art, the electrical circuit does not need to be energised prior to initiating the testing protocol and potentially detecting faults. Preventing energisation of the circuit until it has been determined that there is no fault advantageously prevents, or at least reduces the chances of damage to the trolley-assist system. Further, this also mitigates the risk of harming any technician operating within the at least one power distribution unit because faults will be detected prior to a technician energising the circuit. Energising the or each at least one power distribution unit may involve closing a medium voltage circuit breaker. Initiating a testing protocol at a first test voltage may involve initiating a testing protocol when a circuit breaker of the electrical circuit is open. For example, by providing a sub-circuit from another power supply configured to run a lower voltage through the electrical circuit. Alternatively, particular components on the electrical circuit may be individually tested using a first test voltage. The testing protocol is an electrical inspection of the electrical circuit. The testing protocol is carried out by applying the first test voltage to the circuit and / or a particular component and observing its voltage response. The testing protocol may comprise voltage detection, whereby the desired voltage value or range is pre-set for particular components. If the measured voltage is within the desired range the or each at least one power distribution unit is energised. If the measured voltage deviates from this value, the or each power distribution unit is prevented from being energised. The testing protocol may perform a continuity test to check for any breaks or interruptions in the circuit. The testing protocol may perform an earth fault test. Further, the method monitors the electrical circuit and will de-energise the or each at least one power distribution unit upon detecting a fault. This also advantageously prevents, or at least reduces, damage to trolley-assist system because the electrical circuit is automatically de-energised upon detecting a fault. The method advantageously does not require input or verification from a technician to de-energise the at least one power distribution unit. As a result, the method avoids any delay in de-energising the at least one power distribution unit. The method according to the first aspect advantageously initiates the testing protocol at a first voltage and once energised, monitors the electrical circuit at a second voltage. The second voltage being greater than the first voltage. Using a lower voltage to carry out an initial test of the circuit provides an energy efficient method for testing an electric circuit of a trolley-assist system. This is because lower voltage testing consumes less energy compared to higher voltage testing. Further, lower voltage testing reduces the risk of electrical shock or damage to electronic components. Optionally, upon detecting at least one fault in the electrical circuit, the method comprises outputting an alert. This advantageously provides an indication that at least one fault has been detected such that a technician can be made aware of said fault and as a result the necessary action can be taken. The alert may be output to a remote device. The remote device may be a tablet, laptop or a phone, such as a smartphone, for example. As used herein, the term “remote device” connotes a device that can be off-site with a technician. Advantageously, this means that technicians or users can be informed of faults in the electrical circuit without having to be present at the site. This may allow for efficient use of time, costs and resources. The alert may be output to a network of remote devices. When the method comprises outputting an alert, the alert may be at least one of a visual indicator and an audible indicator. For example, the remote device may output an alarm when it receives an input that at least one fault has been detected in the electrical circuit. Alternatively, or additionally, the remote device may output a message or notification that is displayed on the graphical user interface of the remote device. The alert may comprise technical details of the at least one fault. Technical details may include at least one of the location of the fault, the nature of the fault. For example, whether it is a ground fault, a earth fault or as a result of overheating. For example, the alert might be “DC Trip - Left Fan Cooling Failure”. The alert may comprise the occurrence time and the occurrence date. When the method comprises outputting an alert, a user may be able the access a log book for alerts. The alerts may be coloured coded, for example, a colour for past alerts which have been dealt with, a colour for pending alerts which are being dealt with, and a colour for new alerts. This may advantageously flag re-occurring faults. Optionally, the method comprises, upon detecting at least one fault, isolating one or more catenary systems from the at least one power distribution unit. The method may use at least one DC isolator to isolate one or more catenary systems. The isolator may be an automatic isolator. This is advantageous because it prevents damage to the catenary system upon a fault occurring, and / or increases safety. The catenary system is a system of overhead wires used to supply electricity to the mining vehicle. The catenary system may comprise a catenary wire, and an overhead power cable. The catenary wire supports the overhead power cable, otherwise known as a contact wire. The catenary system may also comprise a messenger wire for transmitting communications from one trolley substation to another. Optionally, the method further comprises receiving an input. The input indicating that the at least one fault has been resolved. ‘Resolved’ may mean that the a technician manually fixed a part of the electrical circuit. However, it may also mean that the technician reviewed the information provided and confirmed that it was a false alarm. The alert on the remote device may be cleared upon there being an input indicating that the at least one fault has been fixed. The alert may change colour in a long book upon there being an input indicating that the at least one fault has been fixed. Optionally, upon receiving the input, the method further comprises initiating the testing protocol at the first test voltage. Advantageously, this ensures that the testing protocol is not initiated, carried out or implemented until confirmation has been provided that the at least one fault has been fixed. This advantageously reduces the risk of damage to the system. This also advantageously reduces the risk of injury to a technician working on the system. Further, initiating the testing protocol at the first test voltage, upon receiving the input rather than energising the electrical circuit adds a further layer of safety. The testing protocol can verify that the at least one fault has been fixed, before energising the electrical circuit. This further advantageously reduces the risk of damage to the system. Optionally, the testing protocol is initiated remotely from the power distribution unit. The testing protocol may be initiated from the remote device. The testing protocol may be initiated from the remote device by a technician. For example, the technician may be able to send a command from the remote device to initiate the testing protocol. Advantageously, this prevents or reduces the need to have a technician on site to initiate testing and as such energisation of the at least one power distribution unit. Consequently, this mitigates the risk to a technician that may occur when initiating the testing protocol. Further, this advantageously saves costs and time / resources. Alternatively, the testing protocol may be initiated from the power distribution unit. The testing protocol may be initiated from the power distribution unit by a technician. Optionally, upon the testing protocol determining that there is no fault in the electrical circuit, the method comprises initialising the or each at least one power distribution unit in preparation for energisation. In other words, once the testing protocol has confirmed that there is no fault in the electrical circuit, the at least one power distribution unit is initialised such that it is ready to be energised. Optionally, upon initialisation, the method comprises outputting a notification to a user that there is no fault in the electrical circuit. Advantageously, this provides an extra layer of safety protection, in that the technician is kept within the chain of communication. Optionally, the notification is output to a remote device. This notification may be a message on a graphical user interface of the remote device. The notification may include technical information. For example, if a fault detected is that the temperature of a component in the at least one power distribution unit has exceeded a threshold, the notification may indicate both that the fault has been fixed and also the current temperature. This may advantageously allow for further verification by the technician. Optionally, the method further comprises receiving an input. The input being a command to energise the or each at least one initialised power distribution unit. The at least one initialised power distribution unit being energised upon receiving an input, provides an additional layer of security and safety, whereby the unit can only be energised with an active choice from a technician to do so. This may provide a safer method of testing the electrical circuit. Further, it prevents the power distribution unit from be unnecessarily energised, for example, when the site is not in use but an initial test has been carried out in preparation. Optionally, the input command is provided from a remote device. This may advantageously allow energisation of the at least one power distribution unit to occur remotely. As such, energisation can occur without the technician having to be on site or in particular, within the power distribution unit. This may provide significant safety advantages and benefits. As well as reducing costs, time and providing a more effective use of resources. Optionally, the testing protocol comprises testing at least one electrical component of the electrical circuit. The testing protocol may comprise testing at least one of: rectifier banks; circuit breakers; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable. The testing protocol may further comprise testing for a fault due to at least one of: inadvertent truck or mining vehicle behaviour; incoming voltage supply surges; cooling system failures; and lightning / static surges on the overhead power cable. Optionally, monitoring the electrical circuit at the second voltage comprises monitoring at least one of the following components of the electrical circuit: rectifier banks; circuit breakers; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable. Monitoring the electrical circuit at the second voltage may further comprise monitoring the temperature of components within the at least one power distribution unit and / or electrical circuit. Further, monitoring the electrical circuit at the second voltage may further comprise monitoring air conditioning units within the at least one power distribution unit. Monitoring the electrical circuit at the second voltage may further comprise monitoring the voltage and / or temperature of components of at least one power distribution unit and / or electrical circuit. Monitoring the temperature is advantageous because overheating of components can reduce the efficiency and lifespan of equipment. Optionally, upon energising the or each at least one power distribution unit, the method further comprises outputting status information of the trolley-assist system. Status information being information or data that has not triggered an alert, but that provides a useful real-time status / update of components of the trolley-assist system. The information may be modified based on specific requirements. The status information may be output to a remote device. This may advantageously allow the technician to remotely monitor the electrical circuit. This advantageously saves cost, time and resources that would be used if the technician had to manually assess the electrical circuit throughout the day. The remote device being a technicians tablet or phone, for example. The status information may be accessible from a plurality of remote devices. The status information may include at least one of: the state of the or each at least one distribution unit; power consumption of the trolley-assist system; and number of trolleys coupled to the overhead power cable. The user or technician may be able review the status information and then interrogate the at least one power distribution unit to assess a parameter indicated in the status information. Therefore, the status information may advantageously flag or bring to the attention of the technician conditions which are not faults but which may require some further investigation. This may advantageously prevent faults from occurring. Optionally, the first test voltage is between about 1350 VDC and about 2600 VDC. VDC being volts of direct current. Optionally, the second voltage is between about 1700VDC and about 2600 VDC. The second voltage is greater than the first test voltage. Optionally, the trolley-assist system comprises a plurality of power distribution units. In particular, there may be two, three, or more power distribution units on one trolley line. Advantageously, a trolley-assist system comprising a plurality of power distribution units per trolley line, may increase the number of trucks that can be powered at one time. Further, it may increase the distance over which the trucks can be powered. When the trolley-assist system comprises a plurality of power distribution units, the plurality of power distribution units are preferably communicatively linked. Advantageously, linking a plurality of power distribution units provides the required electricity to sufficiently power an increase number of mining vehicles per trolley line over a greater distance. Further, this advantageously reduces the need for the mining trucks to disconnect and re-connect every 750 m, for example, as required in known prior art systems. Further still, linking the plurality of power distribution units advantageously allows control of all the power distribution units at the same time. This reduces time spent, compared to known prior art where each power distribution unit has to be dealt with separately. An aerial fibre optic cable or radio frequency systems may be used to link respective communication systems of each power distribution unit. This may allow a controller to monitor the power distribution units and in the event of a failure or fault with one power distribution unit the system will automatically shut down the communicatively linked power distribution units. This advantageously isolates / de-energises the entire trolley-assist system, which improves the repair personnel safety. When the trolley-assist system comprises a plurality of power distribution units, upon at least one fault being detected in the electrical circuit, de-energising each of the plurality of power distribution units. This is advantageous because it ensures repair personnel safety, in comparison to the known prior art, where only one power distribution unit i.e., the one where the fault has occurred, is shut down. According to a second aspect of the present disclosure, there is provided a test system for a trolley-assist system for mining vehicles. The test system comprises a first fault detection module configured to conduct a testing protocol at a first test voltage. The test system further comprises a second fault detection module configured to monitor the electrical circuit at a second voltage. The second voltage is greater than the first voltage. The test system further comprises a controller comprising a processor and memory. The memory storing instructions which when carried out by the processor perform the method steps of the first aspect.Optionally, further comprising a communication module and a remote device, wherein the communication module is configured to output to and receive inputs from the remote device. The test system may be integrated into the power distribution unit control system. Alternatively, the test system may be a standalone system. It will be appreciated that features described in relation to one aspect of the present disclosure may also be applied equally to all of the other aspects of the present disclosure. Features described in relation to the first aspect of the present disclosure may be applied equally to the second aspect of the present disclosure and vice versa. For example, features of the method described in relation to the first aspect may be applied, mutatis mutandis, to the test system of the second aspect. It will further be appreciated that particular combinations of the various features described and defined in any aspects of the invention may be implemented and / or supplied and / or used independently. Description of Specific Examples of the Disclosure Specific examples of the disclosure will now be described with reference to the figures, in which: Figure 1 shows a schematic of a trolley-assist system for mining vehicles; Figure 2 shows a flow diagram of a method according to the present disclosure; Figure 3 shows a flow diagram of a further method according to the present disclosure; Figure 4 shows a flow diagram of a further method according to the present disclosure; Figure 5 shows a flow diagram of a further method according to the present disclosure; Figure 6 shows a flow diagram of a further method according to the present disclosure; and Figure 7 shows a schematic of a test system according to the present disclosure. Specific description Figure 1 illustrates a trolley-assist system 100 comprising a plurality of power distribution units 102a and 102b. Each power distribution unit 102a and 102b is configured to receive electrical power from a source of electrical energy, such as electrical grid, but may also comprise a generator. Each power distribution unit 102a and 102b is configured provide electrical power to an overhead power cable 104, otherwise known as a contact wire. The overhead power cable is supported by a plurality of support structures 106a, 106b, 106c, etc, arranged such that the overhead power cable 104 is above a roadway for use by mining trucks. In this way, the mining trucks can couple to the overhead power cable using a pantograph in order to use the electrical power to power one or more electrical motors to propel or assist the propulsion of the mining truck and harvesting of truck energies. The overhead power cable 104 is further supported by a catenary wire 108, otherwise known as a support cable. The plurality of power distribution units 102a and 102b of the example are communicatively linked to one another by communication systems, such as cables supported by the catenary wire 108. At least one of the power distribution units 102a and 102b comprises a test system. In this example, each power distribution unit comprises a test system 110a and 110b. Further, each power distribution unit comprises an externally mounted automatic stored energy isolator 112a and 112b respectively. The automatic stored energy isolators 112a and 112b are used to isolate the positive and negative catenary system from the power distribution cables. The catenary system comprising the catenary wire 108 and the overhead power cable 104. The test system, described in detail below, is configured to test the electrical circuits of the power distribution units 102, the overhead cables 104, and the catenary wire or cable 108, both before the power distribution 102 units are energised, and while they are energised. Figure 2 illustrates an example method 200 for testing an electrical circuit of the trolley-assist system 100, shown in Figure 1, for mining vehicles embodying the present disclosure. The method comprises the following steps. Step 202 comprises initiating a testing protocol at a first test voltage. The first test voltage being between about 1350 VDC and about 2600 VDC. The specific first test voltage range or value is dependent on the site. For example, dependent on the type of truck that will be used for that trolley-assist system. Step 202 provides a low voltage initial testing protocol, which ensures energisation of the or at least one of the power distribution unit does not occur until the system has been tested. The testing protocol includes determining whether there is a fault in the electrical circuit. The testing protocol includes testing at least one of: rectifier banks; circuit breaker; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable, for a fault. This is not an exhaustive list and additional components of the electrical circuit and / or the power distribution units may be tested for faults. The method further comprises step 204. Step 204 comprises, upon determining that there is no fault in the electrical circuit from the testing protocol of step 202, energising the or each at least one power distribution unit. Energising the or each at least one power distribution unit may involve closing one or more circuit breakers. This advantageously, reduces the chances of damage to the system. If a fault is detected during the testing protocol of step 202 the or each at least one power distribution unit will not be energised until it is determined, by the testing protocol during step 202, that there is no fault in the electrical circuit. This may require maintenance of the system, or secondary confirmation that the detected fault was a false positive result. Once the or each power distribution unit has been energised, the method further comprises step 206. Step 206 comprises monitoring the electrical circuit, now energised, at a second voltage. The second voltage is greater than the first test voltage of step 202. This allows a first testing at a lower voltage which improves safety, while reducing costs and the use of energy resources compared to method where a higher voltage is used continuously. Further, testing at the lower voltage initially also reducing the potential damage to parts of the electrical circuit. The second voltage is between about 1700VDC and about 2600 VDC. The specific second voltage range or value is dependent on the site. For example, dependent on the type of truck that will be used for that trolley-assist system. Monitoring 206 the electrical circuit at the second voltage comprises monitoring at least one of the following components of the electrical circuit: rectifier banks; circuit breakers; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable. This is not an exhaustive list and additional components of the electrical circuit and / or the power distribution units may be monitored for faults. Monitoring may include monitoring the temperature and / or the voltage. The method further comprises step 208. Step 208 comprises, upon detecting at least one fault when carrying out step 206, the method further comprises de-energising 208 the or each at least one power distribution unit. This means that the or at least one power distribution unit is effectively automatically shut down upon at least one fault being detected. This also reduces the likelihood of significant damage occurring to parts of the electrical circuit and as such increases the life-time of the system. Step 208 may further comprise isolating the catenary system from at least one power distribution unit. Figure 3 illustrates a further example method 300 for testing an electrical circuit of the trolleyassist system for mining vehicles embodying the present disclosure. Some of the steps of method 300 are identical to method 200, in particular, steps 202 to 208 which are identical to steps 302 to 308. The method 300 further comprises step 310. Step 310 comprises, upon detecting at least one fault during step 306, outputting an alert. The alert may be outputted simultaneously with the or each at least one power distribution unit being de-energised. The alert is outputted to a remote device. The remote device being a tablet, laptop or mobile device, such as a smartphone, of a technician. The remote device being a device which a technician can take off site. This reduces resources, time and costs with regards to the technicians because it is not necessary to always have the technicians on site to monitor the or each at least one power distribution unit. The technician with the remote device may therefore be ‘on call’. Step 310 may comprise outputting an alert to a network of remote devices. The alert of step 310 can be an audible alert, such as an alarm or ringtone. Alternatively, or additionally, the alert can be a visual alert. This visual alert may be, for example, a flashing screen, a notification, or a message. The notification or message alert the technician that a fault has occurred, but also may include technical information regarding the fault that has occurred. This technical information including the location of the fault and the nature of the fault. For example, if the fault is in the air conditioning unit, the alert may indicate the location e.g. left fan and then the nature of the fault e.g. that the maximum temperature threshold has been exceeded. Further examples of alert notifications include ‘Rectifier - Diode Monitoring Failure - [date] - [time of fault]’, ‘Battery Charger Failure - [date] - [time of fault]’, ‘DC Isolator not opening successfully in preset time’, ‘DC Trip - Left Fan Cooling Failure’ or ‘Rectifier Doors Open’. Figure 4 illustrates a further example method 400 for testing an electrical circuit of the trolleyassist system for mining vehicles embodying the present disclosure. Some of the steps of method 400 are identical to method 300, in particular, steps 302 to 310 which are identical to steps 402 to 410. The method 400 further comprises step 412. Step 412 comprises receiving an input. The input indicating that the at least one fault has been fixed. The fault being the at least one fault that caused the at least one power distribution unit to be de-energised. The input may be received from a technician inputting, on the remote device, for example, that the at least one fault has been fixed or resolved. Alternatively, there may be interfaces on site which a technician may use to indicate that the at least one fault has been fixed. As shown in Figure 4, upon receiving the input, the testing protocol at the first test voltage of step 402 is re-initiated. Therefore, once the technician has confirmed that the at least one fault has been fixed, the method comprises initiating 402 the testing protocol at the first test voltage again. Re-initiating the testing protocol at the first test voltage is effectively a confirmatory check to confirm that the at least one fault has been fixed, before energising the or each at least one power distribution unit. Figure 5 illustrates a further example method 500 for testing an electrical circuit of the trolleyassist system for mining vehicles embodying the present disclosure. Some of the steps of method 500 are identical to method 400, in particular, steps 402, 404, 406, 408, 410, 412 which are identical to steps 502, 512, 514, 516, 518, 520 respectively. The method further comprises step 504, wherein upon the testing protocol determining that there is no fault in the electrical circuit, initialising the or each at least one power distribution unit in preparation for energisation. This initialising prepares the at least one power distribution unit to be energised. In other words, it puts the at least one power distribution unit in a condition appropriate for energisation. The method further comprises step 506. Step 506 comprising upon the initialisation of step 504, outputting a notification to a user that there is no fault in the electrical circuit. This notification is output to a technicians or users remote device. This notification may be output to a network of remote devices. The method further comprises step 508. Step 508 comprising receiving an input to energise the or each at least one power distribution unit. The input is a command to energise or provide electrical power to the or each at least one power distribution unit. The at least one power distribution unit is then energised according to step 512, which is identical to step 504. The input command to energise the or each at least one power distribution unit is provided from a remote device. In other words, the technician or user is notified that no fault has been detected or determined from the testing protocol. The user can then decide, upon receipt of this information, to provide a instruction or command to energise the at least one power distribution unit. This adds a further layer of safety protection before energising the at least one power distribution unit. Further, this allows energisation to occur only when needed. Figure 6 illustrates a further example method 600 for testing an electrical circuit of the trolleyassist system for mining vehicles embodying the present disclosure. Some of the steps of method 600 are identical to method 500, in particular, steps 502 to 520 which are identical to steps 602 to 620. The method 600 further comprises step 622. Step 620 comprises outputting status information of the trolley-assist system. The status information is output to a remote device. The status information may be output to a network of remote devices. The status information includes at least one of: the state of the or each at least one distribution unit; power consumption of the trolley-assist system; and number of trolleys coupled to the overhead power cable. The state of the or each at least one distribution unit includes the state of the air conditioning unit(s), the state of the rectifier etc... The technician may be able to interrogate the system for further information, if required. The technician may be able to interrogate the system for further information if required via an internal VPN. The status information may be generated by a controller. The status information may include graphs which provide information regarding a change condition over time, for example. Further, where there is more than one power distribution unit, the plurality of power distribution units are communicatively linked to one another. As such, were at least one fault is detected during step 506, 306, 406, 512 and 612, the plurality of power distribution units are de-energised. Therefore, if a fault occurs in one power distribution unit the communicatively linked power distribution units are automatically de-energised as well. Figure 7 illustrates a test system 700 for the trolley-assist system for mining vehicles. The test system 700 comprises a first fault detection module 702. The first fault detection module 702 is configured to conduct a testing protocol at a first test voltage. The first fault detection module 702 is configured to determine whether there is a fault in the electric circuit. In particular, the first fault detection module 702 checks for faults in at least one of: rectifier banks; circuit breaker; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable, for a fault. This is not an exhaustive list and additional components of the electrical circuit and / or the power distribution units may be tested for faults. The first test voltage is between about 1350 VDC and about 2600 VDC. The test system 700 (110a, 110b shown in Figure 1) also comprises a second fault detection module 704. The second fault detection module 704 is configured to monitor the electrical circuit at a second voltage. The second voltage is greater than the first voltage. The second voltage is between about 1700 VDC and about 2600 VDC. The second fault detection module 704 monitors the electrical circuit and as such is able to determine if there is a fault in the electrical circuit. The second fault detection module 704 monitors at least one of the following components of the electrical circuit: rectifier banks; circuit breaker; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable. This is not an exhaustive list and additional components of the electrical circuit and / or the power distribution units may be monitored for faults. Monitoring may include monitoring the temperature and / or the voltage of said components. The test system also comprises a controller 706. The controller 706 comprises a processor 708 and memory 710. The controller 706 may be a programme logic controller. The memory 710 stores instructions which when carried out by the processor 708 perform the method steps as illustrated in Figures 1 to 6 discussed above. Upon a fault being detected, a circuit breaker 716, such as a vacuum circuit breaker (VCB), is initiated to de-couple the power distribution unit from the overhead power cable. A VCB is a type of circuit breaker that uses a vacuum as the interrupting medium to extinguish the electric arc when a fault occurs in the electric circuit. In addition, the power distribution unit, or units, are de-energised. The test system further comprises a communication module 712. The test system further comprises the remote device 714. The communication module 712 is configured to output to and receive inputs from the remote device 714. The communication module 712 is in communication with the controller 606 and outputs alerts and / or status information to the remote device 714. The communication module 712 may also output information to a device located at the site, for example, on the outside of the power distribution unit. The communication module 712 outputs commands received from the remote device 714 to the controller 706. For example, the input command to energise at least one power distribution unit. Although not shown, the mining vehicle may comprise an independent test system. The test system allowing each mining vehicle to monitor itself independently from the test system for the trolley-assist system to which is it attached. For example, if an over voltage occurred from utility, the mining vehicle would shut itself down. The mining vehicle may also monitor conditions with regards to what it is receiving. However, alternatively, the method and the test system described with regards to Figure 1 to 7 may be communicatively linked to the mining vehicle.

Claims

1. A method for testing an electrical circuit of a trolley-assist system for mining vehicles, wherein the trolley assist system comprises at least one power distribution unit configured to receive electrical power from a source of electrical energy and provide electrical power to an overhead power cable, the method comprising:initiating a testing protocol at a first test voltage;wherein, upon determining that there is no fault in the electrical circuit:energising the or each at least one power distribution unit; andmonitoring the electrical circuit at a second voltage, wherein the second voltage is greater than the first voltage, andwherein, upon detecting at least one fault, de-energising the or each at least one power distribution unit.

2. The method according to claim 1, wherein, upon detecting at least one fault in the electrical circuit, outputting an alert.

3. The method according to claim 2, wherein the alert is output to a remote device.

4. The method according to claims 2 or 3, wherein the alert is at least one of a visualindicator or an audible indicator.

5. The method according to any of claims 2 to 4, wherein the alert comprises technical details of the at least one fault.

6. The method according to any preceding claim, wherein, upon detecting at least one fault, isolating one or more catenary systems from the at least one power distribution unit.

7. The method according to any preceding claim, further comprising receiving an input, the input indicating that the at least one fault has been fixed.

8. The method according to claim 5, wherein upon receiving the input, initiating the testing protocol at the first test voltage.

9. The method according to any preceding claim, wherein the testing protocol is initiated remotely from the power distribution unit.

10. The method according to any preceding claim, wherein, upon the testing protocol determining that there is no fault in the electrical circuit, initialising the or each at least one power distribution unit in preparation for energisation.

11. The method according to claim 10, wherein, upon initialisation, outputting a notification to a user that there is no fault in the electrical circuit.

12. The method according to claim 11, wherein the notification is output to a remote device.

13. The method according to claim 11 or 12, further comprising receiving an input, the input being a command to energise the or each at least one initialised power distribution unit.

14. The method according to claim 13, wherein the input command is provided from a remote device.

15. The method according to any preceding claim, wherein the testing protocol comprises testing at least one of: rectifier banks; circuit breakers; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable.

16. The method according to any preceding claim, wherein monitoring the electrical circuit at the second voltage comprises monitoring at least one of the following componentsof the electrical circuit: rectifier banks; circuit breaker; direct current feeder cables; direct current isolator; catenary wire; and the overhead power cable.

17. The method according to any preceding claim, wherein, upon energising the or each at least one power distribution unit, the method further comprises outputting status information of the trolley-assist system.

18. The method according to claim 16, wherein the status information is output to a remote device.

19. The method according to claim 17 or 18, wherein the status information includes at least one of: the state of the or each at least one distribution unit; power consumption of the trolley-assist system; and number of trolleys coupled to the overhead power cable.

20. The method according to any preceding claim, wherein the first test voltage is between 1350 VDC and 2600 VDC.

21. The method according to any preceding claim, wherein the second voltage is between 1700 VDC and 2600 VDC.

22. The method according to any preceding claim, wherein the trolley-assist system comprises a plurality of power distribution units.

23. The method according to claim 22, wherein the plurality of power distribution units are communicatively linked.

24. The method according to claim 22 or 23, wherein upon at least one fault being detected in the electrical circuit, de-energising the plurality of power distribution units.

25. A test system for a trolley-assist system for mining vehicles comprising:a first fault detection module configured to conduct a testing protocol at a first test voltage;a second fault detection module configured to monitor the electrical circuit at a second voltage, wherein the second voltage is greater than the first voltage;5 anda controller comprising a processor and memory, the memory storing instructions which when carried out by the processor perform the method steps of any of claims 1 to 24.

26. The test system according to claim 25, further comprising a communication module10 and a remote device, wherein the communication module is configured to output to and receive inputs from the remote device.19

Images