WO2025227128A1

WO2025227128A1 - Insulation resistance tester with integrated fault pre-location

Info

Publication number: WO2025227128A1
Application number: PCT/US2025/026530
Authority: WO
Inventors: Brian D. PAINTING; Matthew A. CASTLE; Han B. Tran; Allison R. WYATT; Travis Tom; Harsha MUNIKOTI; Jay DE JAEN
Original assignee: Fluke Corp
Current assignee: Fluke Corp
Priority date: 2024-04-26
Filing date: 2025-04-25
Publication date: 2025-10-30
Anticipated expiration: 2026-10-26
Also published as: WO2025227128A9

Abstract

An insulation resistance tester includes test cables structured to be coupled to insulation and to a conductor of the DUT, a port coupled to the set of testing cables, a resistance measurement unit coupled to the port and structured to determine an insulation resistance of the DUT, a fault detector coupled to the port and structured to generate a fault-detecting signal to be applied to the DUT to provoke a response, a fault pre-locater structured to receive a return signal from the DUT after being provoked by the fault-detecting signal, and structured to determine a potential location of a fault in the DUT based at least in part on the return signal, and a display structured to show an indication of a location of the fault in the DUT in relation to a location of the insulation resistance tester. Methods are also described.

Description

INSULATION RESISTANCE TESTER WITH INTEGRATED FAULT PRE-LOCATION

FIELD OF THE INVENTION

[0001] This disclosure relates to test and measurement devices, and, more particularly, to a test and measurement device that determines the approximate location of a detected fault and informs a user of the location.

BACKGROUND

[0002] Technicians use Insulation Resistance Testing (IRT) devices to measure insulation resistance of various devices, such as electrical wires, cables, and transformers, for example. The resistance measurement indicates the state of the insulation in the device. Insulation that is failing may be detected as a fault. In operation, IRTs apply either an AC or DC voltage to an insulative material of a cable under test and measure current flow back through an electrical conductor in the cable. The IRT determines resistance values of the insulation, in Ohms, based on the applied voltage and the measured current, and presents the information to the user.

[0003] When the IRT determines that a fault is present, a fault detector device is brought in to help determine the approximate location of the fault. Some fault detectors, called "Thumpers", use a high-voltage capacitive discharge system to help locate the fault. Other types of fault detectors may use technologies such as Time-Domain Reflectometry (TDR), Acoustical and Electro-Magnetics, or a High Potential tester that is associated with a visual inspection. All of these fault detectors have drawbacks. For example, while insulation testing may be performed with little training, fault detectors are generally operated by specialty technicians using a separate tool, only after a fault has been identified. Since the fault detecting devices are specialty devices that are generally scheduled to arrive at the testing site after a fault has been detected, they are not typically available by the operator of the IRT but rather must be specifically scheduled to the site. And, when they are on site, the Thumpertype fault detectors are large, heavy, and require two people to move to most testing locations. Oftentimes, for simplicity, companies use third parties to perform and operate the fault detectors, which adds to the delay and expense of determining the location of an insulation fault detected by an IRT.

[0004] Simply combining a fault detector with an insulation resistance tester has proven difficult due to the different technologies involved with each device. And merely combining the devices does not address the additional training necessary to operate a fault detector compared to the lower skill level of operating an insulation detector.

[0005] Embodiments of the disclosure address this and other shortcomings in modern IRT devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. 1 is a block diagram of an example insulation resistance tester including fault pre-location according to embodiments of the disclosure.

[0007] Fig. 2 is a block diagram of an insulation resistance testing system including the insulation resistance tester of Fig. 1 coupled to a mobile device according to embodiments of the disclosure.

[0008] Fig. 3 is a block diagram illustrating an example spark gap control system for delivering a high voltage used in fault detecting and location in the insulation resistance tester of Fig. 1, according to embodiments.

[0009] Fig. 4 is a block diagram illustrating an example linear actuator control system for delivering a high voltage used in fault detecting and location in the insulation resistance tester of Fig. 1, according to embodiments.

[0010] Fig. 5 is an example display screen that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments.

[0011] Fig. 6 is another example display screen that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments.

[0012] Fig. 7 is yet another example display screen that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments.

[0013] Fig. 8 is an example display screen graph showing location test data that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments.

[0014] Fig. 9 is another example display screen graph showing location test data that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments.

[0015] Fig. 10 is yet another example display screen graph showing location test data that may be shown on either or both devices of the insulation resistance testing system of Fig. 2, according to embodiments. DETAILED DESCRIPTION

[0016] Embodiments of the disclosure include an insulation resistance tester (IRT) having fault pre-location capabilities. The disclosed IRT is handheld, lightweight, easily portable, and smaller than the existing solutions. In addition, the IRT according to embodiments of the disclosure presents a simplified interface that allows technicians to operate it despite not having the specific training necessary to operate a stand-alone fault detector.

[0017] Fig. 1 is a block diagram of an insulation resistance tester 100 including fault prelocation according to some embodiments of the disclosure. The insulation resistance tester 100 includes one or more ports 102, which may be any electrical signaling medium. Ports 102 may include receivers, transmitters, and/or transceivers. The insulation resistance tester 100 may couple to a Cable Under Test (CUT) 130 through the one or more ports 102. In the example of Fig. 1, a pair of electrical test cables 132 connects the CUT 130 to the ports 102. In the illustrated example, the CUT 130 is an electrical cable having a single conductor surrounded by an insulating material. Other types of devices that may be tested with the insulation resistance tester 100 include cables having one or more conductors surrounded by various combinations of insulators or insulation material. Some cables, such as coaxial cables, may include shielding as well. In this description, although the device being tested by the insulation resistance tester 100 is referred to as a CUT, which is for convenience, it is understood that the described insulation tester 100 could be used on any device where an insulation resistance measurement would be useful, and is not limited to only testing cables. Such devices could include transformers, motors, and switchgears, among others, for example.

[0018] The insulation resistance tester 100 includes one or more measurement units 140, which perform the main functions of measuring parameters and other qualities of signals from the CUT 130 being measured by the insulation resistance tester 100. Typical measurements include resistance, voltage, current, and/or power of input signals, as well as insulation-specific tests such as polarization index and dielectric absorption ratio. Some tests may be performed over time, using stepped voltages. The measurement units 140 represent any measurements that are typically performed on insulation resistance testers. One specific type of measurement unit illustrated in the insulation resistance tester 100 is a resistance measurement unit 142, which measures resistance of the CUT 130. In operation, the resistance measurement generates and applies a known voltage to the CUT 130. Then the resistance measurement unit 142 measures the current caused by the applied voltage and determines the resistance of the system using Ohms law.

[0019] Embodiments according to the disclosure also include a fault detector 144 as well as a fault pre-locater 148. The fault detector 144 may operate independently or in conjunction with the above-described resistance measurement unit 142 to determine if the measured resistance is below a predetermined resistance threshold, such as 1 MOhm, or any level of resistance specified by a manufacturer, a particular standard, or a user's specifications. If the measured resistance is below the predetermined resistance threshold, this indicates that there may be a fault in the insulation of the CUT 130.

[0020] If the fault detector 144 determines a fault in the CUT 130 is possible, or probable, the fault detector can prompt the user to initiate a fault pre-locater 148 to determine an approximate location of the probable fault. In other embodiments the fault detector 144 may automatically invoke the fault pre-locater 148 when the fault detector determines a fault is probable in the CUT 130, based on the results of the resistance measurement unit 142. When initiated, the fault pre-locater 148 sends fault detection signals to the CUT 130. Then, also as described below in more detail, the fault pre-locater 148 receives a return signal from the CUT 130 in response to the sent fault detection signals. The fault pre-locater 148 analyzes the return signals to determine whether the CUT contains a fault, and, if so, an approximate location of the fault. Faults may include degradation or failures of the insulation that diminish the insulative effect between two conductors or between a conductor and a ground reference. The functions and details of both the fault detector 144 and fault pre-locater 148 are described in more detail below.

[0021] The insulation resistance tester 100 further includes one or more main processors 110 configured to execute instructions stored in a main memory 111 and may perform any methods and/or associated steps indicated by such instructions. For instance, the processor executes these software instructions and other procedures to operate a menu on a display 122 of the insulation resistance tester 100. A user of the insulation resistance tester 100 uses the menu to control the operation of the resistance tester, such as by setting parameters, running tests, and directing how the results are to be used. The one or more main processors 110 operate most or all functions of the insulation resistance tester 100.

[0022] User inputs 120 are coupled to and act as input for the one or more processors

110, and may include buttons, a keyboard, touchscreen, and/or any other controls employable by a user to interact with the insulation resistance tester 100. The display 122 may be a monochrome or digital screen such as an LCD, LED, OLED, or any other monitor to display output of the insulation resistance tester 100. In some embodiments, data or images from the display 122 of the resistance tester 100 may be made available to other devices through an information cloud 124 or other type of communication network.

[0023] While the components and functions of the insulation resistance tester 100 are depicted and described above, it will be appreciated by a person of ordinary skill in the art that any of these components can be combined or integrated into fewer component parts, or different functions may be split into components in addition to the functional blocks illustrated in Fig. 1. In particular, the fault detector 144 and fault pre-locater 148 may be disposed in a single device, processor, or module.

[0024] Fig. 2 illustrates an insulation resistance measurement system 200 including the insulation resistance tester 100 coupled through the testing cables 132 to the CUT 130. Additionally, the insulation resistance measurement system 200 includes a mobile device 240 that is in communication with the insulation resistance tester 100. The mobile device 240 may be a mobile phone, tablet computer, laptop computer, or other computing device structured to interact with the insulation resistance tester 100. In some embodiments the mobile device 240 is coupled to the insulation resistance tester 100 through communication wires (not illustrated), while in other embodiments the mobile device is wirelessly coupled to the insulation resistance tester, such as through a WiFi, Bluetooth™, or other wireless data protocol.

[0025] In operation, the mobile device 240 and insulation resistance tester 100 cooperate to perform tests and measurements on the CUT 130, including fault pre-location described with reference to Fig. 1. The user of the measurement system 200 may control the system by interacting with either the mobile device 240 or the insulation resistance tester 100 or both the mobile device and the insulation resistance tester. A touch screen 244 on the mobile device 240 may be controlled by one or more processors 250 running programs stored on affiliated memory 251 to present an interactive user interface to the user. Then, by interacting with the touch screen 244, the user can control which tests and which test parameters will be used by the insulation resistance tester 100 to generate tests and make measurements of the CUT 230. Or, in other embodiments, the user inputs to the insulation resistance tester 100 may be controlled by the user to initiate and perform various tests on the CUT 130 and the results of the tests may be shown on display screens located on either or both the insulation resistance tester 100 and the mobile device 240. In some embodiments the mobile device 240 may be used to remotely start and/or stop tests being performed on the insulation resistance tester 100. The details of menus, displays, etc. of the measurement system 200 are largely implementation specific. But, in general, a user may interact with either the mobile device 240 or the insulation resistance tester 100 of the measurement system 200 to perform measurements and tests of the CUT 130 and the results of such measurements and/or tests may be displayed on either device. And, although the measurement system 200 of Fig. 2 includes a mobile device 240 to provide a user of the system with additional controls, inputs, and outputs, it is not strictly necessary that that mobile device 240 be present to operate the insulation resistor tester 100, and instead the insulation resistor tester may be operated solely on its own to test the CUT 130.

[0026] With reference back to Fig. 1, a user may invoke operation of the fault pre-locater 148 of the insulation resistance tester 100 at any time. In other embodiments the fault detector 144 within the insulation resistance tester 100 may automatically invoke the fault pre-locater 148 based on measurement results made by the resistance measurement unit 142. For example, when the insulation resistance tester 100 determines that resistance value measured by the resistance measurement unit 142 is below a testing threshold value, the one or more processors 110 may direct that the fault detector 144 or fault pre-locater 148 automatically perform a fault detection operation without further user input. Or the insulation resistance tester 100 may generate a query to the user and show it on the display 122 (Fig. 1) or on the mobile device 240 (Fig. 2), such as "Measurement Indicates Possible Fault - Proceed to Fault Testing?" Then, depending on the response from the user, the one or more processors 110 cause the insulation resistance tester 100 to perform the fault detection process on the CUT 130 by causing the fault detector 144 or fault pre-locater 148 to generate their signals to detect the potential fault as described above.

[0027] The fault detector 144 may take different forms, depending on embodiments of the insulation resistance tester 100. For example, the fault detector 144 may use time-domain reflectometry (TDR), which involves generating and sending an energy pulse through the port 102 and the test cables 132 to the CUT 130. The pulse may have a voltage of between 10 Volts - 300 Volts, for example. In one embodiment the voltage of the pulse is approximately 50 Volts. Then, the fault detector 144 and/or the fault pre-locater 148 measures a reflection of the pulse as it returns from the CUT 130. Comparing qualities of the return pulse, such as amplitude, to the known outgoing pulses generated by the fault detector 144 allows the insulation resistance tester 100 to determine and measure qualities of any discontinuities in the CUT 130. Also, the time elapsed between sending the pulse and receiving the reflections may be used by the fault pre-locater 148 to calculate an approximate distance to the fault in the CUT 130.

[0028] In some embodiments the insulation resistance tester 100 may perform an automatic pre-location test that repeatedly applies increasing voltages to the CUT 130 being tested until an insulation breakdown occurs in the cable, which may indicate a location of a weak point in the insulation of the CUT. A breakdown may be indicated when the resistance of the CUT 130 undergoing testing has a non-linear change in resistance. Such a breakdown is also referred to as an arc condition, since an electrical arc passes from the insulation to the conductor in the CUT 130 based on the high voltage stimulus pulse. The pre-locater 148 may start the pre-location test by, for example, applying a 1000 Volt stimulus to the cable. Then, if no breakdown occurs, as determined by the cable resistance remaining in an approximate linear band, the voltage is increased to a higher voltage, such as 2000 Volts and again the CUT 130 is checked for insulation breakdown. This test may be repeated until breakdown occurs. This automatic test avoids applying higher voltages than necessary to cause a breakdown in the CUT 130. In other words, using the series of increasing voltages described above allows the user to determine the breakdown voltage of the CUT 130 at the lowest possible voltage, which prevents applying higher than necessary voltages to the cable.

[0029] In other embodiments the fault detector 144 may include or operate in conjunction with an external surge wave generator, also referred to in the industry as a thumper, to generate a series of high-voltage signals that are propagated to the CUT 130 as described above. The high-voltage signals in a thumper-type fault detector 144 may exceed 15,000 Volts. The high voltage signals are selected to be high enough to cause the CUT 130 to produce an electrical arc in one or more areas where the insulation between conductors is compromised. In such an embodiment, the fault pre-locater 148 may include an acoustic device configured to generate an output based on monitored acoustic signals from the arcs caused by the fault detector 144. Then, the fault pre-locater 148 may generate pre-location information about the fault, such as an approximate distance and direction between the insulation resistance tester 100 and the fault itself based on the acoustic signals. Output of such information may be displayed to the user in a number of ways, as described in detail below.

[0030] To safely and accurately deliver the high-voltage signals that cause the electrical arcs described above, certain embodiments may use a pressurized, controllable spark gap actuator to deliver the arc-inducing voltage to the cable being tested. Fig. 3 illustrates an example arc-inducing voltage delivery system 300 that may be a component of the fault pre- locater 148 of Fig. 1. This arc-inducing voltage delivery system 300 may be used in some embodiments to provide the arc triggering voltage in the fault pre-locater 148. In general, the arc-inducing voltage delivery system 300 allows the operator to deliver a particular high voltage with precision. In Fig. 3, a high voltage charging circuit 310 is used to charge a capacitor 320 to a desired arc-inducing voltage for testing. As mentioned above, the testing voltage may be between 3000v - 15,000v in some embodiments. Also, in some embodiments various voltages are applied to the CUT 130 at increasing voltages. In other words, a first voltage is applied and the response of the CUT 130 is measured and interpreted. If it is determined that an additional test is needed, then the voltage is increased and the voltage applied again. This cycle continues until the arc is successfully generated and provides the desired effect on the CUT 130 so that the properties of the cable can be measured and the defect detected, as described above.

[0031] Although the charging circuit 310 and capacitor 320 are illustrated in Fig. 3, there are other methods of generating large voltages, which may be used in embodiments. Also, only one electrode 321 of the capacitor 320 is illustrated in Fig. 3, although it is understood that a second electrode (not illustrated) may also coupled to the CUT 130 so that the high voltage delivered by the capacitor has a return path. In yet other embodiments the return path may be a ground path.

[0032] A spark gap pressure chamber 340 is a sealed system with an operating pressure controlled by a pressure controller 350. The pressure controller 350 may raise or lower a pressure of a gas that fills the pressure chamber 340. The gas may be a noble gas such as argon, helium or neon. Or the gas within the spark gap pressure chamber 340 may be a mixture of other gasses including nitrogen. In some embodiments the gas is air, which is a mixture of mostly nitrogen mixed with oxygen and small amounts of other gasses. In operation, controlling the pressure of the gas in the spark gap pressure chamber 340 causes an electric spark to form at a gap between two electrodes, 344 and 346, within the spark gap pressure chamber 340. In this way, the operator can precisely control either the voltage applied through the gap or the time the voltage is applied through the gap or both the time and voltage at which the arc-inducing voltage is applied to the cable undergoing testing.

[0033] In more detail, the spark gap pressure chamber 340 is a sealed system that includes the first electrode 344 connected to the high voltage source. In this example the source of the high voltage is the capacitor 320. The second electrode 346 of the spark gap pressure chamber 340 is coupled to a test cable 323, which is further coupled to the cable undergoing the test, such as the CUT 130.

[0034] As the high voltage charging circuit 310 is charging the capacitor 320 to the arc- inducing voltage desired to be used for testing, or once the capacitor 320 has achieved the voltage set by the high voltage charging circuit 310, the pressure controller 350 may be operated to induce a particular, pre-determined, pressure within the spark gap pressure chamber 340. Then, when the electrode 344 is at the desired voltage and the pressure within the spark gap pressure chamber 340 is at the specified pressure, a spark 348 jumps across a gap between the electrodes 344 and 346 to cause the high voltage from the capacitor 320 to be passed to the electrode 346, where is further passes through the test cable 323 and is applied to the CUT 130. Thus, by controlling the voltage of the capacitor 320 and the pressure within the spark gap pressure chamber 340, the arc-inducing voltage may be applied to the CUT 130 with precision. Using a higher pressure within the spark gap pressure chamber 340 causes the spark 348 to be generated at higher voltages for the same-sized sparkgap between the electrodes 344, 346, thus allowing the arc-inducing voltage to be applied at a specific, desired, voltage. A feedback loop may be employed to cause the arc-inducing voltage to be applied at increasing levels to the cable undergoing testing, as described above.

[0035] Although reference is made above to the pressurized spark gap pressure chamber 340, in some embodiments the pressure chamber may actually be open to atmospheric pressure, i.e., non-pressurized. In yet other embodiments the spark gap pressure chamber 340 may instead be a vacuum chamber, i.e., a chamber having less than atmospheric pressure, in which case the pressure controller 350 generates a vacuum. In short, the spark gap pressure chamber 340 may operate at any pressure, and does not necessarily need to be pressurized above atmospheric pressure.

[0036] Other delivery control mechanisms may also be used instead of a spark gap to control application of the arc-inducing voltage to the CUT 130. Fig. 4 illustrates an example arc-inducing voltage delivery system 400 that may be used to apply an arc-inducing voltage to a cable undergoing test. The arc-inducing voltage delivery system 400 has similar components to the arc-inducing voltage delivery system 300 described above with reference to Fig. 3, and like components will not be described again for brevity.

[0037] Different than the arc-inducing voltage delivery system 300, the arc-inducing voltage delivery system 400 includes a linear actuator 360 coupled to an electrode 368 within a high-voltage switch 342. The high voltage switch 342 has the same function as the spark gap pressure chamber 340 described above, which is to deliver the arc-inducing voltage to the CUT 130 at the proper time. In embodiments, the electrode 368 may include tips formed of tungsten or other material that couple to each of the electrodes 344, 346 to turn on the high voltage switch 342 and apply the voltage from the capacitor 320 to the test cable 323 to be further applied to the CUT 130. In practice, the linear actuator 360 controls the movement of a mechanic coupler 362 that is attached to the electrode 368. When the linear actuator moves mechanic coupler 362, the electrode 368 makes or breaks contact between the electrodes 344, 346, thus turning on or off the high voltage switch 342.

[0038] Returning back to the systems described in Figs. 1 and 2, the insulation resistance tester 100 may use different forms of fault detection in the fault detector 144 and fault pre- locater 148 depending on specific types of faults. For example, the TDR-type fault detector generally provides better test results for completely open circuits or fully shorted circuits in the CUT 130, while the surge generator-type fault detector generally provides better results for partially compromised insulators in the CUT. So, some embodiments of the insulation resistance tester 100 may include either the TDR type fault detector 144 or the surge wave generator type of fault detector 144, depending on which fault may be expected in a certain CUT.

[0039] Yet other embodiments of the fault detector 144 may leverage both technologies described above and be embodied by an arc reflector device. An arc reflector device combines both a TDR generator and a surge generator method in a combined device. In practice, an arc reflector embodiment of the fault detector 144 generates the high voltage signals like the surge wave generator described above, and, in addition, generates TDR signals to be sent to the CUT 130. Both sets of signals are sent through the port 102 and test cables 132 to the CUT 130. In practice, the TDR signals are reflected back from the arc caused by the surge wave generator, which eliminates the need for an acoustic listening device as described above. In operation, qualities of the reflected TDR signals may be used to determine information about the fault by analyzing properties of the TDR signals, such as amplitude, and by comparing the shape of reflected signals to the shape of signals originally sent by the TDR to the CUT 130. Also, the timing of the return of the TDR signals compared to their origination times is used by the fault pre-locater 148 to determine an approximate location of the fault.

[0040] After the insulation resistance tester 100 determines that there may be a fault present in the CUT 130, and after the fault detector 144 and fault pre-locater 148 determine an approximate distance to the fault, using any of the technologies described above, the insulation resistance tester, according to embodiments, may generate a report of the measurements and findings to the user. One common way to report the measurements is by simply displaying them on either the display 122 of the insulation resistance tester 100 (Fig. 1) or on the touch screen 244 (Fig. 2) of the mobile device 240. Outputs of the measurements may include, for example, a numerical or text-based display of the measurements, a graphical display of the measurements, or a combination of text and graphics. In some embodiments the graphical display of the measurements may be in the form of a meter, a graphic approximation of a meter, or a display of actual graphed data on an output waveform graph having a time axis, such as that approximating an oscilloscope display. Yet other outputs may include a data file that includes measurement data in row and column form.

[0041] Some insulation measurements made in the insulation resistance tester 100 may include several measurements taken at various locations on or within the CUT 130. For example, if the CUT 130 is an insulated transmission cable, the user may take measurements at two ends of the cable. If the insulation resistance tester 100 determines a fault may be present, and invokes the fault-detection processing described above, the multiple measurements may be combined to form a single measurement, such as by averaging the results of the multiple tests. In other embodiments, if fault pre-location is performed, the insulation resistance tester 100 may use a second or subsequent test in another location on the same CUT 130 to verify or refine the location output of the test. By integrating fault prelocation capabilities into the insulation resistance tester 100, the user can more easily generate "as-found" and "as-left" test reports, including the presence of a fault (with distance) or lack of a fault, with all of the data integrated from a single testing instrument.

[0042] As described above, data recorded during measurements when operating the insulation resistance tester 100 is assembled for reporting to the user. If no faults are detected, orthe measurements indicate that no fault is likely, then the report may be a simple report of the resistance value or values of the CUT 130 such as in text or graph form. If, however, a fault is likely to be present in the cable undergoing testing, then the insulation resistance tester 100 may proceed to the fault detection and pre-location as described above. In some embodiments, the insulation resistance tester 100 assembles the fault pre-location data and integrates it into the report, so that there is a record of the test as well as the potential location of the fault. In other embodiments, when the insulation resistance tester 100 finds the location of a fault, a text and/or graphic display, such as those illustrated in Figs. 4-10 may be presented on either the insulation resistance tester 100 orthe mobile device 240 to help direct the user to the location of the fault.

[0043] Fig. 5 illustrates an example display screen 500 having a very simple display 510 that shows the user the estimated distance to the fault through a text-based message. This estimated distance in the message 510 is determined by the insulation resistance tester 100 using the techniques described above, such asTDR. As described above, the message 510 may be shown on the insulation resistance tester 100, the mobile device 240 (Fig. 2), or on both the insulation resistance tester and the mobile device.

[0044] Fig. 6 illustrates an example display screen 600 that may be presented to the user on either or both of the insulation resistance tester 100 and the mobile device 240. In other embodiments, the display screen 600 showing location data may be shown on the mobile device 240, while measurement results are displayed on the insulation resistance tester 100. With reference to Fig. 6, the display screen 600 includes an indication 602 of the location of the insulation resistance tester 100 itself, or the mobile device 240, as well as an indication of a possible distance perimeter 604 of the location of the detected fault. The display screen 600 may be updated in real-time as the user walks toward or away from the detected fault. GPS features on the mobile device 240 may be used by an application running on the mobile device to help determine the location of the user. Fig. 7 illustrates an alternative example display screen 700 that may be presented to the user on the mobile device 240 (Fig. 2). The mobile display screen 700 is map-based, which may leverage a map application that operates on the mobile device 240. An indication 702 of the location of the insulation resistance tester 100, orthe mobile device 240 is displayed on the map as well as an indication 704 of a location of the fault, as determined by the insulation resistance tester 100. [0045] Figs. 8, 9, and 10 illustrate example screens 800, 900, 1000, shown on either the insulation resistance tester 100 or the mobile device 240. The example screens 800, 900, 1000 show data generated by the insulation resistance tester 100 in graphical form, showing the user actual data determined by the insulation resistance tester 100. For example, the example screen 800 of Fig. 8 informs the user that a fault was determined using an arc reflection method described above. And the main graph shows an elevated voltage at approximately 140 meters from the location of the user, which informs the user the approximate distance to the fault in the tested cable.

[0046] The example screen 900 of Fig. 9 illustrates that the user may control a position of cursors, such as cursor 1 and cursor 2 to precisely identify locations of the faults as determined by the insulation resistance tester 100. In this example, cursor 1 indicates an arc reflection occurred at approximately 72 meters from the user, while the cursor 2 indicates that the cable length is approximately 140 meters. In this embodiment, cursors 1 and 2 may be controlled by the user to determine distances between any two points of interest on the display, such as arcs or any impedance disturbances due to splices, transformers, etc.

[0047] The example screen 1000 of Fig. 10 shows a zoomed-in version of the acquired data on a main screen 1002. In particular, the acquired data is shown in a data bar 1010 near the top of the main screen 1002. The acquired data exceeds the amount of data that can be clearly displayed at one time on the main screen 1002. Instead, only a portion 1016 of the acquired data is actually displayed on the main screen 1002. The user controls which portions of the acquired data from the data bar 1010 are on shown on the main screen 1002 by operating a set of scroll buttons 1020, 1022 to move right or left within the set of acquired data. Furthermore, the user can operate a zoom function 1030 to control how much of the acquired data is shown on the main screen 1002 at any single time. For example, zooming to 6x will make the data appear larger within the main window 1002, but will decrease the total amount of data that is able to be shown on the main window at one time.

[0048] As described above, the insulation resistance tester according to embodiments of the disclosure includes multiple advantages over the state of the art. In addition to making resistance measurements, the disclosed insulation resistance tester may include fault prelocation, which has only been available before in some type of fault-detection device. The disclosed insulation resistance tester may be lighter than previous fault-detection devices and is easier for a single operator to use. Integrating a fault-detection function in an insulation resistance tester removes the necessity of a user carrying and operating two different tools. Not only does the disclosed insulation resistance tester simplify tracking the distance to the fault through its integrated location display, but the insulation resistance tester also unifies measurement data as well as fault location data onto a single test report, in addition to other advantages.

[0049] The previously described versions of the disclosed subject matter have many advantages that were either described or would be apparent to a person of ordinary skill. Even so, these advantages or features are not required in all versions of the disclosed apparatus, systems, or methods.

[0050] Additionally, this written description makes reference to particular features. It is to be understood that the disclosure in this specification includes all possible combinations of those particular features. Where a particular feature is disclosed in the context of a particular aspect or example, that feature can also be used, to the extent possible, in the context of other aspects and examples.

[0051] Also, when reference is made in this application to a method having two or more defined steps or operations, the defined steps or operations can be carried out in any order or simultaneously, unless the context excludes those possibilities.

[0052] Although specific examples of the invention have been illustrated and described for purposes of illustration, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims.

Claims

CLAIMS:

1. An insulation resistance tester, comprising: a first test cable structured to be coupled to insulation of a device under test (DUT); a second test cable structured to be coupled to a conductor of the DUT; a port coupled to the set of testing cables; a resistance measurement unit coupled to the port and structured to determine an insulation resistance of the DUT; a fault detector coupled to the port and structured to generate a fault-detecting signal to be applied to the DUT to provoke a response; a fault pre-locater structured to receive a return signal from the DUT in response to the fault-detecting signal, and structured to determine a potential location of a fault in the DUT based at least in part on the return signal; and a display structured to show an indication of a location of the fault in the DUT in relation to a location of the insulation resistance tester.

2. The insulation resistance tester according to claim 1, in which the fault detector is structured to generate the fault-detecting signal based on the resistance determined by the resistance measurement unit.

3. The insulation resistance tester according to claims 1 or 2, in which the fault detector is structured to generate the fault-detecting signal when the resistance determined by the resistance measurement unit is below a pre-determined threshold.

4. The insulation resistance tester according to any of the preceding claims in which the fault-detecting signal is a time-domain reflectometry signal.

5. The insulation resistance tester according to claim 4, in which the time-domain reflectometry signal is a pulsed voltage.

6. The insulation resistance tester according to claim 5, in which the pulsed voltage has an amplitude between approximately 10 Volts and 300 Volts.

7. The insulation resistance tester according to any of claims 1-3, in which the faultdetecting signal is structured to cause an arc fault in the DUT.

8. The insulation resistance tester according to claim 7, in which the fault-detecting signal has an amplitude between approximately 500 Volts and 15,000 Volts.

9. The insulation resistance tester according to claims 7 or 8, in which the fault detecting signal comprises a time-domain reflectometry signal and a signal structured to cause an arc fault in the DUT.

10. The insulation resistance tester according to claims 7 or 8, in which insulation tester further comprises an acoustic device configured to measure a sound caused by the electrical arc fault in the DUT.

11. The insulation resistance tester according to claim 10, in which the fault pre-locater is structured to determine an approximate distance between the electrical arc fault and the insulation resistance tester based on the measured sound.

12. The insulation resistance tester according to any of claims 1-4, or 7-11, in which the fault-detecting signal is initiated with a spark gap pressure controller.

13. The insulation resistance tester according to any of claims 1-4, or 7-11, in which the fault-detecting signal is initiated with an actuator-controlled switch.

14. The insulation resistance tester according to claim 13, in which the actuator- controlled switch includes a movable electrode structured to close an electrical circuit including one or more static electrodes.

15. The insulation resistance tester according to claim 14, in which the movable electrode includes tungsten tips.

16. The insulation resistance tester according to any of the preceding claims, further comprising a mobile computing device in communication with the insultation resistance tester.

17. The insulation resistance tester according to claim 16, in which the mobile computing device comprises a display screen.

18. The insulation resistance tester according to claim 18, in which the indication of the location of the fault is further generated on the display screen of the mobile computing device.

19. The insulation resistance tester according to any of the preceding claims, in which the fault detector is also structured to receive the return signal.

20. The insulation resistance tester according to any of the preceding claims, in which the fault pre-locater is further structured to generate a signal to be applied to the DUT.

21. A method performed by an insulation resistance tester coupled to a device under test, the method comprising: performing a resistance test on the device under test; comparing results of the resistance test to a fault threshold to generate a comparison outcome; and performing a fault location test on the device under test by the insulation resistance tester.

22. The method according to claim 21, in which the fault location test is automatically performed based on the comparison outcome.

23. The method according to claim 21, further comprising generating a prompt to a user of the insulation resistance tester based on the comparison outcome.

24. The method according to claim 23, in which generating a prompt comprises presenting a message on a display of the insulation resistance tester.

25. The method according to claims 23 or 24, in which generating a prompt comprises presenting a message on a display of a separate computing device coupled to the insulation resistance tester.

26. The method according to any of the preceding claims 21-25, in which performing a fault location test comprises: generating an electrical pulse having a first voltage amplitude; delivering the electrical pulse having the first voltage amplitude to the device under test; determining if the device under test incurred an arc event; if no arc event occurred in the device under test based on the first electrical pulse, repeatedly generating and delivering electrical pulses having increased voltage amplitudes until the arc event occurs in the device under test.

27. The method according to any of the preceding claims 21-26, in which performing a fault location test comprises: generating a fault detecting signal; applying the fault detecting signal to the device under test; receiving a reflected signal back from the device under test; and analyzing the reflected signal.

28. The method according to claim 27, in which generating the fault detecting signal comprises generating a time-domain reflectometry signal.

29. The method according to claim 28, in which generating the time-domain reflectometry signal comprises generating a pulsed voltage.

30. The method according to any of claims 27-29, in which generating the pulsed volage comprises generating an amplitude between approximately 10 Volts and 300 Volts.

31. The method according to claim 30, in which generating the fault-detecting signal comprises generating an arc inducing signal.

32. The method according to claim 31, in which generating an arc inducing signal comprises generating a signal having an amplitude of between approximately 500 Volts and 15,000 Volts.

33. The method according to claims 31 or 32, further comprising detecting a sound caused when the arc inducing signal causes an arc.

34. The method according to claim 33, further comprising measuring a distance to the arc based on the sound.

35. The method according to any of claims 31-34, in which generating the fault-detecting signal comprises generating the fault-detecting signal with a spark gap pressure controller.

36. The method according to any of claims 31-34, in which generating the fault-detecting signal comprises generating the fault-detecting signal with an actuator-controlled switch.

37. The method according to claim 36, in which the actuator-controlled switch comprises an electrode having tungsten tips.

38. The method according to any of the preceding claims 19-37, further comprising establishing a communication channel between the insulation resistance tester and a portable computing device.

39. The method according to claim 38, further comprising presenting a measurement of the device under test on a display of the portable computing device.

40. The method according to claim 38 or 39, further comprising presenting a measurement of the device under test on a display of the portable computing device and on a display of the insulation resistance tester.