Portable diagnostic apparatus for testing circuit breakers

A portable diagnostic apparatus for performing diagnostic testing on a circuit breaker includes a number of sensor devices structured to generate a number of sensed parameter signals relating to operation of the circuit breaker during an operational sequence, a number of auxiliary input connectors structured to receive a number of auxiliary data signals from the circuit breaker, the number of auxiliary data signals relating to and being generated in response to the operation of the circuit breaker during the operational sequence, and control and diagnostic circuitry. The control and diagnostic circuitry is structured to control operation of the portable diagnostic apparatus, receive the number of sensed parameter signals and the number of auxiliary data signals, and generate a time signature based on the number of sensed parameter signals and the number of auxiliary data signals.

BACKGROUND

Field

The disclosed concept pertains generally to circuit breakers used in power transmission and distribution systems, and, more particularly, to a portable diagnostic apparatus including an onboard diagnostic feature for performing diagnostic testing on circuit breakers, such as, without limitation, low or high voltage power circuit breakers.

Background Information

Electrical power transmission and distribution systems typically utilize a plurality of power circuit breakers which include one or more sets of separable contacts for protecting circuits against overcurrent conditions. In the field, a number of such circuit breakers are generally mounted and housed within a non-conductive housing or enclosure, often referred to as a switchgear enclosure. Power connections for the circuit breakers are generally terminated in the rear of the enclosure, and instrumentation and control terminal blocks for the circuit breakers may either be mounted in the rear or the front of the enclosure. In many cases, switchgear equipment as just described is provided in a drawout configuration wherein the circuit breakers may be completely removed from the front of the switchgear enclosure for repair, testing or maintenance. On other cases, the circuit breakers are mounted on customized framework, generally called a fixed breaker, and may not be able to racked out of the framework.

The electrical power transmission and distribution industry has a huge installed-base of power circuit breakers. Many of the circuit breakers have been in the field for a long time and are still completely operational. These older circuit breakers, unlike many more modern circuit breakers, do not have any built-in diagnostic sensors for monitoring the operation thereof. If such a circuit breaker fails, the customer typically immediately replaces the failed circuit breaker with a spare circuit breaker available on site, and transfers the failed circuit breaker to a remote maintenance site for diagnostic testing and repair.

Many of the circuit breakers in the electrical power and distribution industry are what are known as drawout circuit breakers. Drawout circuit breakers often include a mechanism for moving the breaker in and connecting the breaker to corresponding electrical contacts, a location known as the “racked-in” position. When in the racked-in position, the circuit breaker is coupled to the main electrical circuit and provides the interruption functionality for which it is intended. If the drawout mechanism is activated to the “racked-out” position, the circuit breaker is disconnected from the electrical contacts and the main electrical circuit. The circuit breaker may be moved to the racked-out position, for example, when maintenance is performed on the main electrical circuit. Typical racking mechanisms often include a third or “test” position in between the “racked in” or “Connected” position and “Racked out” or “Disconnected” position. In the test position the circuit breaker can be closed, opened or tripped in order to check the functionality of the circuit breaker by evaluating proper operation of the internal and external accessories such as auxiliary switches, shunt trip and under voltage and secondary circuits.

Diagnostic testing and repair at such a remote maintenance site often makes the diagnosis of the real problem more difficult, since the circuit breaker will often have to be tested without electrical control power due to the unavailability of a proper fixture such as switchgear enclosure, testing cabinet, etc. In addition, on-call service Engineers or maintenance staff at the customer's site may face problems understanding the breaker mechanism and may not be able to repair the issue due to lack of knowledge and/or sensor diagnostic data. Thus, there is a need for a diagnostic device that can easily and readily interact with the circuit breaker, under drawout or fixed configurations, as discussed above, and provide onboard diagnostic information. In the case of a drawout breaker, it is also often necessary to analyze the breaker functioning under switchgear control signals, giving rise to at least three modes of diagnostic protocol, including, but not limited to, ONLINE mode, Semi-Online mode and Offline mode.

Further, the time constrains at maintenance shops due to the cost associated with the downtime or maintenance itself are critical. This creates a need for quick guidance as to the appropriate and accurate repair instructions further to the on board diagnostic indications. This is needed to further improve the service efficiency for the breaker failure event. This requires an automated diagnostic and repair methodology to be implemented in the new portable device that can be used at the customer's site.

SUMMARY

In one embodiment, a portable diagnostic apparatus is provided for performing diagnostic testing on a circuit breaker. The portable diagnostic apparatus includes a number of sensor devices structured to generate a number of sensed parameter signals relating to operation of the circuit breaker during an operational sequence, a number of auxiliary input connectors structured to receive a number of auxiliary data signals from the circuit breaker, the number of auxiliary data signals relating to and being generated in response to the operation of the circuit breaker during the operational sequence, and control and diagnostic circuitry. The control and diagnostic circuitry is structured to control operation of the portable diagnostic apparatus, receive the number of sensed parameter signals and the number of auxiliary data signals, and generate a time signature based on the number of sensed parameter signals and the number of auxiliary data signals.

In another embodiment, a method of performing diagnostic testing on a circuit breaker is provided. The method includes causing the circuit breaker to perform an operational sequence, employing a portable diagnostic apparatus coupled to the circuit breaker to generate a number of sensed parameter signals relating to operation of the circuit breaker during the operational sequence, receiving in the portable diagnostic apparatus a number of auxiliary data signals from the circuit breaker, the number of auxiliary data signals relating to and being generated in response to the operation of the circuit breaker during the operational sequence, and generating in the portable diagnostic apparatus a time signature based on the number of sensed parameter signals and the number of auxiliary data signals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “number” shall mean one or an integer greater than one.

As employed herein, the term “time signature” shall mean a visual representation of a number of waveforms each indicating a time sensitive parameter relating to the operation of a circuit breaker or switchgear/cell and/or the data that may be used to represent, render or otherwise generate such a visual representation.

A circuit breaker has its own working logic, which is implemented electro-mechanically using an interlock mechanism, separable contacts and actuators such as a motor, close-open coils, etc. These components have very specific time-dependent relations with respect to each other. This working logic can be obtained and represented as a time signature for the circuit breaker. Whether operated mechanically or electrically, proper operation of a circuit breaker will result in a “normal” time signature having a certain, predetermined format. Time signatures that deviate from this “normal” format can be indicative of certain issues with the operation of the circuit breaker that may have caused or will eventually cause certain failure mode(s). Thus, a properly acquired time signature for a circuit breaker may be used to provide diagnostic input to a service engineer to assist with the diagnostic process.

As described in greater detail herein, the disclosed concept provides a portable diagnostic apparatus that may be used to perform diagnostic testing on a circuit breaker by acquiring/generating a time signature for the circuit breaker. As also described in greater detail herein, the portable diagnostic apparatus may be used: “on-site” at the site wherein the circuit breaker is normally installed, e.g., in a switchgear enclosure, in an online or automatic mode of operation wherein the circuit breaker is electrically operated via locally generated or remotely generated switchgear control signals, or “off-site” at, for example, a remote maintenance site, in modes wherein the circuit breaker may be electrically operated in a manner that simulates switchgear control or manually operated.

FIG. 1is a schematic diagram of a portable diagnostic apparatus2according to an exemplary embodiment of the disclosed concept. In one particular, non-limiting exemplary embodiment, diagnostic apparatus2is provided in the form of a portable diagnostic box as shown inFIG. 2that, to facilitate traveling, is the size of an acceptable airline carry-on baggage with a strong, rigid and bounce resistant cover4. InFIG. 1, the dotted line shows the boundary where all of the wired connections to diagnostic apparatus2will be made as described herein.

As seen inFIG. 1, diagnostic apparatus2includes main control and diagnostic circuitry6. In one aspect, main control and diagnostic circuitry6includes a processor apparatus/module that includes a processor and a memory. The processor may be, for example and without limitation, a microprocessor, a microcontroller, or some other suitable processing device or circuitry, that interfaces with the memory. The memory can be any of one or more of a variety of types of internal and/or external storage media such as, without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the like that provide a storage register, i.e., a machine readable medium, for data storage such as in the fashion of an internal storage area of a computer, and can be volatile memory or nonvolatile memory. The memory forming part of main control and diagnostic circuitry6has stored therein a number of routines that are executable by the processor. One or more of the routines implement a system for controlling the operation of diagnostic apparatus2as described herein. In another aspect, main control and diagnostic circuitry6includes diagnostic circuitry that is structured and configured to receive a number of inputs relating to the operation of a circuit breaker from the outside enclosure such as switchgear or cell and to generate a time signature based on the received input information. As described herein, that time signature may then be used to diagnose issues relating to the operation of the circuit breaker.

Diagnostic apparatus2further includes an input terminal block8and an output terminal block10. Input terminal block8is structured to enable a number of input connections to be made to diagnostic apparatus2. Output terminal block10is structured to enable a number of output connections to be made to diagnostic apparatus2so that output signals can be provided from diagnostic apparatus2to another device. Input terminal block8and output terminal block10are electrically connected to main control and diagnostic circuitry8such that certain input signals can be routed from input terminal block8to main control and diagnostic circuitry6and certain output signals can be routed from main control and diagnostic circuitry6to output terminal block10as needed. In addition, a number of electrical connections12are provided between input terminal block8and output terminal block10so that certain signals can be passed from input terminal block8to output terminal block10directly as needed.

Diagnostic apparatus2also includes a number of sensor devices14. Each sensor device14is structured to measure a parameter, such as a current and/or a voltage, that is present on one of the electrical connections12. For example, and without limitation, a sensor device14may be a Rogowski coil or a Hall effect sensor for measuring current or a voltage measuring apparatus. Each sensor device14is also operatively coupled to main control and diagnostic circuitry6such that the output of the sensor device14can be provided to main control and diagnostic circuitry6.

Diagnostic apparatus2includes power electronics module16structured to provide various types of power functionality for diagnostic apparatus2. Power electronics module16may contain, for example and without limitation, step up/down transformers, signal conditioning circuitry, rectifying circuitry, a pulsating power generator, and frequency modulation circuitry. The power functionality provided by power electronics module16may include providing DC or AC power for powering the various electronic components of diagnostic apparatus2. The power functionality provided by power electronics module16may also include generating power and control signals that simulate the power and control signals of a switchgear that, in certain embodiments described herein, are provided to a circuit breaker to electrically control and operate the circuit breaker, including any number of circuit breaker accessory devices such as, without limitation, a spring charging motor, a spring release device, a shunt trip device, and/or an undervoltage release device. The significance of this functionality is described in detail elsewhere herein. A power connector22is also provided as part of diagnostic apparatus2and is coupled to power electronics module16. Power connector22is provided to enable power electronics module16to receive AC power from a local source, such as, for example and without limitation, a wall outlet.

Diagnostic apparatus2further includes a number of auxiliary data connectors18that are operatively coupled to main control and diagnostic circuitry6. The auxiliary data connectors18are structured to enable one or more input electrical signals to be provided to main control and diagnostic circuitry6from another device. Such data inputs are useful for measuring the performance of the circuit breaker elements, such as those that are not directly or indirectly connected to switchgear or an external control cell. Such elements are used only internally to the circuit breaker, for example, but not limited to, a motor cutoff switch, various internal limit switches, etc. In addition, a data connector20, which may enable wired and/or wireless connections, such as, but not limited to, a standard USB connector, Ethernet, CAN BUS, DIN, RJ45, or blue tooth, WiFi, NFS etc, is provided in order to enable main control and diagnostic circuitry6to output data, such as a time signature, to a device such as, without limitation, a laptop computer, a tablet computer, or a smartphone.

Finally, diagnostic apparatus2includes I/O apparatus23which may include various types of devices for inputting information into diagnostic apparatus2and/or outputting information from diagnostic apparatus2. Such devices may include various switches and buttons to control various aspects of diagnostic apparatus2and/or various visual display devices, such as LEDs or LCD displays, for enabling diagnostic apparatus2to output certain information as described herein to a user.

As noted elsewhere herein, diagnostic apparatus2may be operated in either an on-site, online or automatic mode of operation at the site wherein the circuit breaker being tested is normally installed with the circuit breaker being operated via switchgear control, or in a number of off-site modes wherein the circuit breaker being tested being operated such that it is controlled electrically via signals that simulate switchgear control or manually. Particular non-limiting, exemplary implementations of these modes of operation will now be described.

FIG. 3is a schematic diagram illustrating operation of diagnostic apparatus2in the on-site mode for performing diagnostic testing on a drawout switchgear assembly24including a switchgear enclosure26which houses a circuit breaker28in a manner wherein the circuit breaker28may be selectively drawn out of switchgear enclosure26. As is known in the art, drawout switchgear assembly24includes a mechanism for selectively moving the circuit breaker28among racked-in, racked-out and test positions, as described elsewhere herein. It will be understood, however, that description herein including drawout switchgear assembly24is exemplary only, and that the disclosed concept may be employed with other types of circuit breaker implementations such as, without limitation, a fixed type circuit breaker.

As seen inFIG. 3, switchgear enclosure26includes a switchgear secondary disconnect30which is coupled to instrumentation and control terminal blocks32. Switchgear enclosure26also includes electrical contacts34structured to enable electrical connections to be made to an AC power source and a load. As will be appreciated, in drawout switchgear assembly24, circuit breaker28is structured and configured to provide circuit protection functionality to the attached load. As also seen inFIG. 3, circuit breaker28includes circuit breaker secondary disconnect36which is structured to be in electrical connection with switchgear secondary disconnect30when switchgear assembly24is in the racked-in position. Circuit breaker28also includes various trip components, control circuitry and accessories, indicated at reference numeral38, which may include the mechanism for automatically tripping circuit breaker28, a number of circuit breaker accessories, such as, without limitation, a spring charging motor, a spring release device, a shunt trip device, and/or an undervoltage release device, and associated control electronics, such as an electronic trip unit. Switchgear secondary disconnect30is operatively coupled to a control center which, during normal operation of switchgear assembly24, generates power and control signals for operating switchgear assembly26. Thus, when switchgear secondary disconnect30and circuit breaker secondary disconnect36are coupled to one another in the racked-in condition, signals generated by the control center may be provided to trip components, control circuitry and accessories38through switchgear secondary disconnect30and circuit breaker secondary disconnect36. Such signals may include, for example and without limitation, signals for controlling a spring charging motor, a spring release device, a number of shunt trip devices, or an overvoltage release device, and/or signals for controlling the opening and closing of the separable contacts of circuit breaker28by any other suitable means.

As noted elsewhere herein, main control and diagnostic circuitry6of diagnostic apparatus2is structured and configured to receive a number of inputs relating to the operation of a circuit breaker, such as a circuit breaker28, and to generate a time signature based on the received input information. In particular, according to an aspect of the disclosed concept and in accordance with the exemplary embodiment shown inFIGS. 1-3, the time signature related inputs may be provided to main control and diagnostic circuitry6from a number of the sensor devices14and/or from circuit breaker28through auxiliary data connectors18in response to circuit breaker28being subjected to a particular operational sequence.FIG. 4is a schematic representation of an exemplary time signature60that may be generated by main control and diagnostic circuitry6in response to a particular operational sequence of circuit breaker28.

As seen inFIG. 4, time signature60includes a number of time dependent waveforms62a-62heach indicating a time sensitive parameter relating to the operation of circuit breaker28during the operational sequence. In the non-limiting, illustrated exemplary embodiment, waveforms62aand62bare based on the output of two sensor devices14and waveforms62c-62hare based on data received through auxiliary data connectors18from circuit breaker28. It will be appreciated, however, that this is meant to be exemplary only, and that the waveforms62comprising time signature60may differ. For example, waveforms62a-62dmay be based on the output of sensor devices14with the remaining waveforms,62e-62h, being based on data received through auxiliary data connectors18, and so on. In one particular, non-limiting exemplary embodiment, waveform62ais based on and represents the current of a spring charging motor provided as part of circuit breaker28as measured by one of the sensor devices14in the form of a current sensor, waveform62bis based on and represents the current of a solenoid coil provided as part of circuit breaker28as measured by another one of the sensor devices14also in the form of a current sensor, and waveforms62c-62hare based on and represent the following digital data received through auxiliary data connectors18from circuit breaker28, respectively: contact-LC, contact-PS2, contact travel, contact LS1, auxiliary contact, and contact LS2. In addition, the operational sequence used to generate the time signature60may be any of a number of operational sequences, such as, without limitation, a CHARGE-CLOSE-CHARGE-OPEN-CLOSE-OPEN sequence, wherein CHARGE indicates the charging or compression of the closing springs of circuit breaker28, CLOSE indicates the closing of the separable contacts of circuit breaker28, and OPEN indicates the opening of the separable contacts of circuit breaker28. Other operational sequence may include, without limitation, CHARGE-OPEN-CLOSE and CHARGE-CLOSE-CHARGE-OPEN.

In operation, when it is desired to perform on-site diagnostic testing of circuit breaker28, a service engineer will travel to the site with diagnostic apparatus2. Once at the site, circuit breaker28is moved to the racked-out position. In this racked out position, switchgear secondary disconnect30will be disconnected from circuit breaker secondary disconnect36. Diagnostic apparatus2is then operatively coupled in series between switchgear enclosure26and circuit breaker28by connecting switchgear secondary disconnect30to input terminal block8using cable assembly40, connecting circuit breaker secondary disconnect36to output terminal block10using cable assembly42, and connecting the trip components, control circuitry and accessories38to auxiliary data connectors18using cable assembly44. In addition, a local AC source46, such as a wall outlet, is connected to power connector22using cable assembly48. Finally, a computing device50, such as, without limitation, a laptop computer, a tablet computer, or a smart phone, is connected to data connector20using cabling52.

Next, to perform the diagnostic testing, the service engineer will control operation of circuit breaker28using locally or remotely generated switchgear control signals as described elsewhere herein and cause circuit breaker28to be subjected to a particular operational sequence, such as, without limitation, the CHARGE-CLOSE-CHARGE-OPEN-CLOSE-OPEN sequence described above. During this operational sequence, main control and diagnostic circuitry6will collect the data that is used to generate the time signature as described above via one or more of the sensor devices14and via inputs provided through auxiliary data connectors18. The time signature, once generated by main control and diagnostic circuitry6, may then be output to computing device50through data connector20and cabling52. Once received by computing device50, the time signature may be displayed so that it can be viewed by the service engineer. In addition, computing device50may be provided with software which compares the received time signature to a stored, predetermined “normal” time signature for circuit breaker28in order to identify particular issues and/or failure modes. Furthermore, according to a particular embodiment, main control and diagnostic circuitry6may also be provided with software which is able to examine the generated time signature and identify particular failure modes therefrom. Once particular failure modes are identified, they may be displayed via I/O apparatus23provided as part of diagnostic apparatus2, for example in the form of a failure code. The service engineer may then use the indicated failure code to consult an operational manual for circuit breaker28to determine the particular problem that corresponds to the indicated failure code.

Another advantage of the on-site, online mode just described is that a service engineer can also gauge the signal coming from the switchgear secondary disconnect30. For example, if a breaker is designed to handle 125 VDC control voltage for the opening coil, but switchgear enclosure26and switchgear secondary disconnect30are providing 200 VDC via failed switchgear components, this would be a problem that a service engineer would be interested in and would need to address first, as this situation would change the opening time of the breaker.

FIG. 5is a schematic diagram illustrating operation of diagnostic apparatus2in the off-site mode for performing diagnostic testing on circuit breaker28wherein circuit breaker28has been removed from switchgear enclosure26and taken to a remote site for the diagnostic testing according to one particular exemplary embodiment. It will be understood that the illustration of circuit breaker28inFIG. 5is meant to be exemplary only, and that other types of circuit breakers may also be tested in this manner according to an aspect of the disclosed concept.

In operation, when it is desired to perform off-site diagnostic testing of circuit breaker28, a service engineer will remove the circuit breaker28from switchgear enclosure26and take it to the remote site. At the remote site, diagnostic apparatus2is operatively coupled to circuit breaker28by connecting circuit breaker secondary disconnect36to output terminal block10using cable assembly42, and connecting the trip components, control circuitry and accessories38to auxiliary data connectors18using cable assembly44. In addition, a local AC source64, such as a wall outlet, is connected to power connector22using cable assembly48. Finally, a computing device50, such as, without limitation, a laptop computer, a tablet computer, or a smart phone, is connected to data connector20using cabling52.

Next, to perform the diagnostic testing, the service engineer will control operation of circuit breaker28by causing control and diagnostic circuitry6, in conjunction with power electronics16, to generate power and control signals which simulate switchgear control signals. As will be appreciated, the service engineer may cause such signals to be generated using I/O apparatus23as described herein. The generated power and control signals are output to circuit breaker secondary disconnect36through output terminal block16and cause circuit breaker28to be subjected to a particular operational sequence, such as, without limitation, the CHARGE-CLOSE-CHARGE-OPEN-CLOSE-OPEN sequence described above. As described elsewhere herein, during this operational sequence, main control and diagnostic circuitry6will collect the data that is used to generate the time signature as described above via one or more of the sensor devices14and via inputs provided through auxiliary data connectors18. The time signature, once generated by main control and diagnostic circuitry6, may then be used as described in detail elsewhere herein to assist with the diagnostic testing of circuit breaker28. The time signature in this mode of operation may look similar to time signature60shown inFIG. 4. Thus, operation of diagnostic apparatus2as just described represents the off-site mode with electrical control of circuit breaker28.

According to an alternative embodiment, the configuration shown inFIG. 5may be used to test a circuit breaker, such a circuit breaker28, in an off-site mode wherein, rather than employing electrical control of circuit breaker28, manual control of circuit breaker28is employed. In particular, in this embodiment, once diagnostic apparatus2is connected as shown inFIG. 5, the user can manually cause the circuit breaker to be subjected to a particular operational sequence, such as, without limitation, the CHARGE-CLOSE-CHARGE-OPEN-CLOSE-OPEN sequence described above, with the resulting time signature being generated as described herein. The time signature in this mode of operation may look similar to time signature60shown inFIG. 4, except that, since the circuit breaker28was manually controlled, the waveforms62aand62bthat represent electrical breaker control signals will be absent.

FIG. 6is a schematic diagram illustrating operation of diagnostic apparatus2in the off-site mode for performing diagnostic testing on circuit breaker28wherein circuit breaker28has been removed from switchgear enclosure26and taken to a remote site for the diagnostic testing according to an alternative particular exemplary embodiment. The embodiment shown inFIG. 6is similar to the embodiment shown inFIG. 5, except that in diagnostic apparatus2, certain of the power electronics functionality provided in power electronics module16has been removed therefrom and instead provided in a separate power supply apparatus66. As seen inFIG. 6, power supply apparatus66is coupled to local AC source64for receiving AC power therefrom. In addition, power supply apparatus66is coupled to input terminal block8via cable assembly68so that power supply apparatus66can provide certain signals to diagnostic apparatus2. In one embodiment, power supply apparatus66is provided with a strong, rigid and bounce resistant cover similar to cover4. Power supply apparatus66, in the exemplary embodiment, includes a processor apparatus and an I/O apparatus for controlling operation of power supply apparatus66and enabling user input into power supply apparatus66. For example, the included I/O apparatus may include CLOSE, OPEN buttons on the front panel to perform a CHARGE-CLOSE-CHARGE-OPEN-CLOSE-OPEN sequence as described herein, or any other desired sequence. A power supply apparatus66may also contain, for example and without limitation, step up/down transformers, signal conditioning circuitry, rectifying circuitry, a pulsating power generator, and frequency modulation circuitry such that the power functionality provided by power supply apparatus66may also include generating power and control signals that simulate the power and control signals of a switchgear to control and operate circuit breaker28, including any number of circuit breaker accessory devices such as, without limitation, a spring charging motor, a spring release device, a shunt trip device, and/or an undervoltage release device. Those signals, when generated and output by power supply apparatus66and provided to diagnostic apparatus2are then provided to circuit breaker28through circuit breaker secondary disconnect36as described herein. Thus, this embodiment, wherein power supply apparatus66provides power supply and certain operation logic and diagnostic apparatus2provides sensing and diagnostic functionality, provides an alternative configuration wherein circuit breaker28may be electrically controlled in order to obtain a time signature for diagnostic purposes as described herein.