WO2015184491A1 - Voltage detector - Google Patents

Abstract

A voltage detector comprising positive and negative probes as input; a self-test input; a self-test output; a voltage level output; a transformer connected, in use, to a power source, where the transformer generates a known transformer voltage from the power source; and electronic circuitry. The electronic circuitry is arranged to, when the self-test input is not actuated to receive a signal indicative of a voltage difference between the positive and negative probe inputs, and control the voltage level output to indicate the voltage difference between the positive and negative probe inputs. The electronic circuitry is arranged to, when the self-test input is actuated and the positive probe input and the negative probe input are connected in a short circuit, determine the actual transformer voltage, and if the actual transformer voltage is within a threshold of the known transformer voltage, actuate the self- test output to indicate a successful self-test procedure.

Description

VOLTAGE DETECTOR

Related Application

This application is based on and claims the benefit of the filing and priority dates of Australian patent application no. 2014902124 filed 3 June 2014, the content of which as filed is incorporated herein by reference in its entirety.

Field of the Invention

The present invention is generally related to a voltage detector and particularly, although not exclusively, related to a voltage detector for measuring voltage levels in power systems.

Background to the Invention

Power systems, such as substations or those associated with the rail industry (including overhead lines), can experience downtime, during which maintenance or expansion work can take place. It is important to ensure that there is no residual electricity in such a power system when such work is undertaken because this can lead workers receiving electric shocks. Before any work is performed, technicians can perform measurements using instruments to confirm that the area is safe to work on.

Summary of the Invention

In a first broad aspect the invention provides a voltage detector comprising:

a positive probe input;

a negative probe input;

a self-test input;

a self-test output;

a voltage level output;

a transformer connected, in use, to a power source, where the transformer is arranged to generate a known (that is, predetermined or preconfigured) transformer voltage from the power source;

electronic circuitry;

wherein the electronic circuitry is arranged to, when the self-test input is not actuated:

receive a signal indicative of a voltage difference between the positive probe input and the negative probe input, and control the voltage level output to indicate the voltage difference between the positive probe input and the negative probe input; and

wherein the electronic circuitry is arranged to, when the self-test input is actuated and the positive probe input and the negative probe input are connected in a short circuit, determine the actual transformer voltage, and upon the actual transformer voltage being within a threshold of the known transformer voltage:

actuate the self-test output to indicate a successful self-test procedure.

In an embodiment, the voltage detector comprises a voltage-detection output, wherein the electronic circuitry is configured to actuate the voltage-detection output upon detecting a voltage difference between the positive probe input and the negative probe input.

In an embodiment, the electronic circuitry is configured to actuate the voltage-detection output upon detecting a transformer voltage.

In an embodiment, the voltage detector comprises a buzzer, wherein the electronic circuitry is configured to control the buzzer to sound upon determining that the actual transformer voltage is with a threshold of the known transformer voltage.

In an embodiment, the self-test input is a button or switch.

In an embodiment, the voltage detector comprises a housing that contains the electronic circuitry, wherein the self-test input, the self-test output and the voltage level output are mounted on the housing.

In an embodiment, the voltage level output is a display.

In an embodiment, wherein the self-test output is a light.

In an embodiment, the power source is an internal battery.

In a second broad aspect the invention provides a kit of parts comprising:

the voltage detector of the first broad aspect;

a positive probe comprising a test contact arranged to electrically connect with the positive probe input; and a negative probe comprising a test contact arranged to electrically connect with the negative probe input.

In a third broad aspect the invention provides a voltage detection and self-test method comprising:

connecting a transformer to a power source;

generating a transformer voltage;

actuating a self-test input;

connecting a positive probe input to a negative probe input in a short circuit; determining whether the transformer voltage is within a threshold of a known transformer voltage;

actuating a self-test output to indicate a successful self-test procedure.

In an embodiment, the method comprises actuating a voltage-detection output upon detecting a voltage difference between the positive probe input and the negative probe input.

In an embodiment, the method comprises actuating the voltage-detection output upon detecting the transformer voltage.

In an embodiment, the method comprises controlling a buzzer to sound upon determining that the actual transformer voltage is within a threshold of the known transformer voltage. In an embodiment, the self-test input is a button or switch.

In an embodiment, the voltage level output is a display.

In an embodiment, the self-test output is a light.

In an embodiment, the power source is an internal battery. Brief Description of the Drawings

In order that the invention may be more clearly ascertained, embodiments will now be described, by way of example, with reference to the accompanying drawing, in which:

Figure 1 is a perspective view of a voltage detector of the invention; Figure 2 is a close-up perspective view of a test contact of the voltage detector of figure 1 ;

Figure 3 is a close-up schematic view of a housing and display of the voltage detector of figure 1 ;

Figure 4 is a circuit diagram of the circuitry of the voltage detector of figure 1 ; and

Figure 5 is a flow diagram for safely using the voltage detector of figure 1 .

Detailed Description of Embodiments of the Invention

The invention is generally related to a voltage detector comprising a self-testing circuit. The self-testing circuit is generally enables a user to confirm that the voltage detector is functional or working correctly before using the voltage detector to test voltage in a power system. The voltage detector may also be used to measure the voltage across suitable points of a power system. The voltage detector may be used with any suitable power system and may detect DC or AC voltage of any suitable level, such as up to 3000 V.

Referring to figure 1 , a voltage detector 2 may be used to detect a potential difference or voltage in a power system, such as a substation or overhead lines within a rail system. Typically, a voltage is detected over a point-of-interest in the power system and ground or earth, though voltage may be detected over any suitable location. The voltage detector 2 comprises a positive probe input 4 and a negative probe input 6. The positive probe input 4 is arranged to receive and electrically connect with a positive probe 8, and the negative probe input 6 is arranged to receive and electrically connect with a negative probe 10. The voltage detector 2 typically comprises a housing 12 that houses or contains electronic circuitry and that provides for the reception and connection of the positive 8 and negative 10 probes.

The positive 8 and negative 10 probes typically each comprise an elongated, insulated portion 14a, 14b with a respective electrically conducting test contact 16a, 16b provided at the distal end. An electrical conductor (not shown) is typically provided in each probe 8,10 and electrically connects to the test contact 16a, 16b, runs lengthwise through the insulated portion 14a, 14b, and electrically connects to the electrical circuitry at the proximal end, thereby electrically connecting each test contact 16a, 16b to the electrical circuitry. The insulated portion14a, 14b may protect a user from an electric shock when the voltage detector 2 is in use. In an embodiment, the positive probe 8 is rigidly connected to the housing 12. For example, a socket provided on the housing may receive and hold or secure the proximal end of the positive probe 8. The socket may provide a thread that complements a thread found on the proximal end of the positive probe 8, thereby facilitating a mechanical connection between the housing 12 and the positive probe 8. The housing may comprise a handle 18 that enables a user to move the positive probe 8 in order to bring the positive test contact 16a into contact with a suitable part of a power system for voltage detection. However, the positive probe 8 may be connected to the housing 12 in any suitable rigid or non-rigid manner.

In an embodiment, the negative probe 10 is flexibly connected to the housing 12. For example, a plug on the housing may receive a first end of an electrical lead 20, and a plug on the negative prove 10 may receive a second end of the lead 20. The second end of the electrical lead 20 is typically received at or near the proximal end of the negative probe 10. The negative probe 10 may also comprise a handle 21 that enables a user to move the negative probe 10 in order to bring the negative test contact 16b into contact with a suitable part of a power system for voltage detection. The flexible connection of the negative probe 10 to the housing 12 may facilitate movement of the negative probe 10 relative to the positive probe 8 so that a user can reach between two suitable points in the power system for voltage detection. For example, the user may first place the negative test contact 16b on a suitable negative or earth point and then place the positive test contact 16a on an overhead line in order to measure the overhead line voltage. As another example, the user may place the test contacts 16 together in order to execute the self-testing function of the voltage detector. The negative probe 10 may be connected to the housing 12 in any suitable flexible or non-flexible manner.

In an embodiment, the positive probe 8 is extendable. The positive probe 8 may comprise a telescoping portion 22 at its distal end. A user may extend the distance between the positive test contact 16a and the housing 12 by, for example, opening a locking tab 24, extending the telescoping portion 22 to the desired length, and closing the locking tab 24 again. The positive probe 8 may comprise a spring (not shown) that facilitates automatic retraction of the telescoping portion 22 upon opening the locking tag 24. However, the positive probe 8 may be extendable through any other suitable mechanism. In an embodiment, the negative probe 10 is alternatively or additionally similarly extendable. The probes 8,10 may be extendable by any suitable length, such as from 760 mm to 1360 mm. Figure 2 is a enlarged perspective view of positive probe 8 of voltage detector 2 (though equally illustrates the corresponding features of negative test contact 10). Referring to figure 2, in an embodiment, test contact 16a may be removable. The test contact 16a may comprise an external (or male) threaded portion 26 that is received by a corresponding internal (or female) threaded portion 28 provided on the distal end of the positive probe 8 or negative probe (not shown in figure 2). The threaded portions 26, 28 are typically composed of an electrically conducting material in order to facilitate electrical connection between the test contact 16a and the probe (and ultimately with the electrical circuitry). This connection may be enhanced by the presence of corresponding pads 30 provided on the test contact 16a and distal end of the probe 8. In an embodiment, the test contact 16a comprises a knurled pattern 32 on is surface, which may assist with the test contact 16a in gripping the contact point of the power system. However, the test contact 16a may be provided with any suitable pattern such as serrations, grooves or barbs. The test contact 16a may be any suitable length such as 60 mm. The test contact 16a may be arranged to receive and electrically connect with an adapter or connector suitable for connection to specific power systems (such as those found in the railway industry). Figure 3 is a schematic view of housing 12 and the voltage level output (in the form of display 34) of voltage detector 2. Referring to figure 3, the voltage detector 2 comprises a voltage level output arranged to indicate to the user a voltage level. The voltage detector 2 also comprises a self-test output arranged to indicate a successful self-test function result to the user. The voltage level output is typically in the form of a display 34, and the self-test output is typically in the form of a light, but any suitable output devices may be used. The voltage detector may comprise additional outputs such as a voltage-detection output, which may be a light or any other suitable output device. Each output may be any suitable type of output such as: i) visual output (such as numbers, letters or symbols displayed on a display 34; lights such as LEDs), ii) audible output (such as a sound made by a speaker or a buzzer), iii) tactile output (such as vibrating caused by a motor connected to an eccentric weight), or iv) output detectable by some other sensor (such as an infrared emission). For example, a detected voltage level may be indicated to the user via display 34, and the successful self-test function result may be indicated to the user via a self-test light 36.

In an embodiment, the voltage detector comprises three outputs: i) a display 34, ii) a self-test light 36, and iii) a voltage-detection light 38. In particular, the voltage detector 2 comprises a display 34 arranged to indicate to a user a voltage level. The display is typically arranged to indicate a detected voltage level or value to the user when the voltage detector 2 is in use. The display 34 may be a backlit or non-backlit. The display may be a liquid-crystal display (LCD) or any other suitable display. The display may be capable of displaying four digits as well as symbols, such as a low-battery symbol. Alternatively, for example, the display may comprise a series of LEDs that light up in a known sequence to indicate a voltage level to the user. In this

embodiment, the voltage detector 2 comprises a self-test light 36 arranged to indicate to a user that the voltage detector 2 is in working order and is safe to use, for example, by confirming continuity of the voltage detector 2 circuitry. The self-test light 36 may be a LED or any other suitable light. In this embodiment, the voltage detector 2 comprises a voltage detection light 38 that is arranged to indicate to a user that any voltage level is detected. The voltage-detection light 38 may be an LED or any other suitable light. The voltage-detection light 38 may be controlled to flash upon determining that a voltage is being detected.

In this embodiment, the voltage detector comprises two inputs: i) a self-test input, such as a self-test button 40, and ii) an on/off switch 42. The self-test input is typically a button or switch that is arranged to connect or switch in a test circuit in order to perform a self-test function on the voltage detector. The self-test input may be a switch or a push button, such as a normally open or push-to-make switch, or any other suitable button. The self-test input typically requires pressing and holding by a user in order to perform a self-test procedure of the voltage detector. The on/off switch 42 is typically arranged to switch the voltage detector 2 on and off, and may be a rocker, a toggle switch, or any other suitable type of switch.

The various inputs and outputs may be mounted in the housing 12 or provided in any other suitable manner, such as remotely through a wired or wireless connection. As referred to above, the voltage detector 2 has two main modes of operation: i) a self- test mode, and ii) a voltage-detection mode. A user may wish to test that the voltage detector 2 is safe to use (i.e. by performing a self-test function) before using it to measure a (potentially high) voltage in a power system. The self-test function may indicate whether or not there is continuity in the voltage detector 2 circuitry or whether or not all of the componentry is operational. In performing a self-test function, a user may perform the following steps: i) ensure that the voltage detector 2 is switched off (i.e. using the on/off switch 42), ii) connect the positive probe input to the negative probe input, for example, by touching the positive test contact to the negative test contact, iii) switching the voltage detector 2 on (i.e. using the on/off switch 42), iv) pressing the self-test button. This may result in the indication of one of a successful or failed self-test procedure to the user.

At least, the self-test output may indicate to the user that the test was successful, which may mean that there is continuity in the circuitry and that the circuitry is operational. For example, the self-test light 36 will illuminate while the user is pressing the self-test button and successful self-test function conditions are present. In some embodiments, additional outputs are required to indicate to the user that the self-test procedure was successful, and this may be represented by any suitable combination of any suitable outputs. For example, in addition to the self-test light illuminating, the voltage-detection light 38 may illuminate, a buzzer may sound, and a particular number or symbol may be displayed on the display 34, where the combination of these four outputs indicates to the user that the self-test was successful. A failed self-test may be indicated if any required output is not actuated. The user may avoid using the voltage detector for voltage detection in such cases.

Referring to figure 4, the housing of the voltage detector comprises electronic circuitry 44 that allows for the operation of the voltage detector and, in particular, allows for the execution of the two modes of operation discussed above. The electronic circuitry 44 comprises a power circuit 45 comprising a power source input arranged to receive a power source 46. In an embodiment, the power source 46 is an internal DC power source and may be a battery (such as a 9 V battery) or any other suitable internal power source. (The housing may provide a removable portion to access and replace the power source 46.) In other embodiments, the power source 46 may be external. For example, an external battery pack or mains power may be connected to the power source input to provide power to the circuitry. The power source input may be electrically connected to a voltage regulator 48 and a timing circuit 50 (to ensure constant, regulated power is provided to the circuitry 44) via on/off switch 42. The power circuit 45 may provide a backlight power source and a low-battery signal to the display 34.

The electronic circuitry 44 comprises a positive probe input 4 and a negative probe input 6 arranged to electrically connect to the positive test contact and negative test contact, respectively. The probe inputs 4,6 are electrically connected to an input circuit 52, and may have associated current limiting resistors 54. The input circuit 52 may comprise analogue-to-digital converters and associated logic so that the input circuit 52 receives analogue signals from the probe inputs 4,6 and outputs digital signals.

The input circuit 52 may be electrically connected to a metering circuit 56 and an alarm circuit 58. The metering circuit 56 may comprise logic that converts the received input circuit 52 signal into a control signal indicative of the potential difference or voltage level between the probe inputs 4,6, and outputs the control signal to the display 34 so that the display 34 is controlled to indicate to the user that voltage level.

The alarm circuit 58 may comprise logic that converts the received input circuit signal 52 into a control signal indicative of the detected voltage level between the probe inputs 4,6 and outputs the control signal to the voltage-detection light 38 and a buzzer 60. The voltage-detection light 38 may be controlled to illuminate upon the detection of any (i.e. non-zero) voltage difference between the probe inputs 4,6 in both the voltage detection mode and the self-test mode. (The voltage-detection light 38 generally indicates to the user that a voltage difference is detected.) In an embodiment, the buzzer may be used only to indicate to the user a successful result during a self-test procedure. Thus, the buzzer may be controlled to sound upon the detection of a voltage difference between a lower and upper threshold in the self-test mode, as is discussed below.

The electronic circuitry comprises self-test circuitry 62 arranged to allow the user to perform a self-test procedure. The self-test circuitry is electrically connected to: i) the self-test input, such as the self-test button 40, ii) the input circuit 52, and iii) the self-test output, such as the self-test light 36. The self-test circuitry 62 generally comprises a transformer, such as a step-up transformer, though any suitable transformer may be used. The transformer typically receives power from the power circuit 45 and outputs a predetermined, preconfigured or known voltage, such as 50 V or 200 V. For example, the transformer may convert or step up the power signal to a voltage that replicates a voltage detection scenario. For example, the transformer may receive a 9 V power supply and step it up to 50 V or 200 V (or any other suitable voltage level) for delivery to the input circuit 52. (It should be recalled that the probe inputs 4,6 are shorted during a self-test procedure, and so the self-test circuit 62 output signal takes the place of the probe input 4,6 signals.) Upon receiving the self-test circuit 62 signal, the input circuit 52 (as described above) may check that a known or expected voltage (such as 50 V or 200 V ± some threshold) has been received, and then sends signals to the metering circuit 56 and alarm circuit 58 for actuation of the display 34, voltage-detection light 38 and buzzer 60. During self-test mode, the user may expect to see an indication of a voltage level on the display 34 that corresponds to the output of the self-test circuit or the transformer, such as 50 V or 200 V (i.e. the known voltage) ± some threshold. This may (in concert with any other required outputs) indicate to the user that the voltage detector is in working order.

Concurrently, the self-test circuit 62 actuates the self-test output if a suitable transformer-output voltage (such as 50 V or 200 V ± some threshold) is achieved. For example, the self-test circuit 62 may control the self-test light 36 to illuminate if the transformer generates an output voltage between 45 V and 55 V (i.e. 50 V ± 5 V) when it is expected to generate 50 V. This may (in concert with any other required outputs) indicate to the user that the voltage detector is in working order.

Figure 5 is a flow diagram 63 of a method of use for safely using voltage detector 2. Referring to figure 5, a user may be required to follow a safety procedure in order to safely use the voltage detector to detect voltages at a power system. According to this procedure, at step 64 a calibration label (for example, found on housing 12) is checked to ensure that the current date is not past the required calibration and testing date. Upon such a determination of currency, at step 66 a self-test procedure as described above is performed. That is, for example, positive test contact 16a and negative test contact 16b are brought into contact; on/off switch 42 is switched to its "ON" position; self-test button 40 is held depressed; if, while depressing self-test button 40, speaker or buzzer 60 sounds, voltage-detection light 38 flashes, self-test light 36 illuminates with a steady glow and display 34 shows a voltage reading of between 45 V and 55 V (when expected to read 50 V), voltage detector 2 is deemed to PASS— and otherwise FAIL.

If the self-test 66 fails, use of the voltage detector is aborted 68. If the self-test 66 passes, the method of use continues at step 70, where the user operates voltage detector to measure the voltage between two desired points of a power system by, typically, securely connecting the negative test contact 16b to a suitable ground or earth point and only then connecting the positive test contact 16a. At step 72, the user can then read the potential difference or voltage level from the voltage level output (such as display 34). When doing so, if the detected voltage is below the nominal voltage (e.g. 50 V), voltage-detection light 38 will not illuminate, speaker or buzzer 60 will remain silent, and the detected voltage will be displayed on display 34; if the detected voltage is the nominal voltage of greater, voltage-detection light 38 will flash, speaker or buzzer 60 will sound, and the detected voltage will be displayed on display 34.

At step 74, another self-test is performed in the same manner as described above. If the self-test fails, the reading 72 should be discarded and further use of the voltage detector aborted 68. If the self-test at step 74 passes, the user can determine at step 76 whether it is safe to proceed with work (in the light of the reading), such as power system maintenance, in line with local or federal guidelines. If so, the user proceeds with the intended work at step 38 but, if not, the user would typically report the unacceptable voltage to the ESO (or equivalent) and seek the ESO's advice on how to proceed.

The voltage detector may be provided with a suitable carry case, such as an aluminium protective carry case. The voltage detector may also be provided with one or more silicon-impregnated cloths for coating the test contacts with silicon during wet-weather conditions, which can help prevent the formation of a continuous film of water thereon.

It will be understood to persons skilled in the art of the invention that many

modifications may be made without departing from the spirit and scope of the invention.

In the claims that follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that such prior art forms a part of the common general knowledge in the art, in any country.

Claims

Claims

1. A voltage detector comprising:

a positive probe input;

a negative probe input;

a self-test input;

a self-test output;

a voltage level output;

a transformer connected, in use, to a power source, where the transformer is arranged to generate a known transformer voltage from the power source;

electronic circuitry;

wherein the electronic circuitry is arranged to, when the self-test input is not actuated:

receive a signal indicative of a voltage difference between the positive probe input and the negative probe input, and

control the voltage level output to indicate the voltage difference between the positive probe input and the negative probe input; and

wherein the electronic circuitry is arranged to, when the self-test input is actuated and the positive probe input and the negative probe input are connected in a short circuit, determine the actual transformer voltage, and upon the actual transformer voltage being within a threshold of the known transformer voltage:

actuate the self-test output to indicate a successful self-test procedure.

2. A voltage detector as claimed in claim 1 comprising a voltage-detection output, wherein the electronic circuitry is configured to actuate the voltage-detection output upon detecting a voltage difference between the positive probe input and the negative probe input.

3. A voltage detector as claimed in claim 2, wherein the electronic circuitry is configured to actuate the voltage-detection output upon detecting a transformer voltage.

4. A voltage detector as claimed in any one of claims 1 to 3 comprising a buzzer, wherein the electronic circuitry is configured to control the buzzer to sound upon determining that the actual transformer voltage is with a threshold of the known transformer voltage.

5. A voltage detector as claimed in any one of claims 1 to 4, wherein the self-test input is a button or switch.

6. A voltage detector as claimed in any one of claims 1 to 5 comprising a housing that contains the electronic circuitry, wherein the self-test input, the self-test output and the voltage level output are mounted on the housing.

7. A voltage detector as claimed in any one of claims 1 to 6, wherein the voltage level output is a display.

8. A voltage detector as claimed in any one of claims 1 to 7, wherein the self-test output is a light.

9. A voltage detector as claimed in any one of claims 1 to 8, wherein the power source is an internal battery.

10. A kit of parts comprising:

the voltage detector as claimed in any one of claims 1 to 8;

a positive probe comprising a test contact arranged to electrically connect with the positive probe input; and

a negative probe comprising a test contact arranged to electrically connect with the negative probe input.

1 1 . A voltage detection and self-test method comprising:

connecting a transformer to a power source;

generating a transformer voltage;

actuating a self-test input;

connecting a positive probe input to a negative probe input in a short circuit; determining whether the transformer voltage is within a threshold of a known transformer voltage;

actuating a self-test output to indicate a successful self-test procedure.

12. A voltage detection and self-test method as claimed in claim 1 1 comprising actuating a voltage-detection output upon detecting a voltage difference between the positive probe input and the negative probe input.

13. A voltage detection and self-test method as claimed in claim 12 comprising actuating the voltage-detection output upon detecting the transformer voltage.

14. A voltage detection and self-test method as claimed in any one of claims 1 1 to 13 comprising controlling a buzzer to sound upon determining that the actual transformer voltage is within a threshold of the known transformer voltage.

15. A voltage detection and self-test method as claimed in any one of claims 1 1 to

14, wherein the self-test input is a button or switch.

16. A voltage detection and self-test method as claimed in any one of claims 1 1 to

15, wherein the voltage level output is a display.

17. A voltage detection and self-test method as claimed in any one of claims 1 1 to 16, wherein the self-test output is a light.

18. A voltage detection and self-test method as claimed in any one of claims 1 1 to 17, wherein the power source is an internal battery.