Abstract:
A phasing and indicator arrangement is provided for switchgear or the like that responds to electrical sources and provides voltage indicator functions, phasing determinations, and self-test features. Phasing provisions are responsive to two or more voltage sensors proximate respective electrical sources to provide an output that represents the phase difference, i.e. time relationship, between the electrical sources as an alternating-current voltage measurable by a voltmeter. The output is relatively independent of the voltage of the electrical sources. The indicator arrangement is operable in a test mode to test the integrity of one or more voltage indicators while clearly identifying that the indicator arrangement is in a test mode. In a preferred arrangement, the indicator arrangement in the self-test mode is powered by a photocell. Further, in the self-test mode, the indicator arrangement generates signals through each voltage sensor and over the complete voltage sensing path, the generated signals being substantially similar to the signals generated by each voltage sensor during normal operation in response to an alternating-current source. In the self-test mode, the phasing arrangement is also tested.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional of application Ser. No. 08/788,158 filed on Jan. 24, 1997, now U.S. Pat. No. 5,910,775, which is a continuation-in-part application of application Ser. No. 08/705,460, filed on Aug. 29, 1996, now U.S. Pat. No. 5,864,107. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to phasing and indicator arrangements for switchgear and the like in the field of electrical power distribution, and more particularly to an arrangement that facilitates phasing measurements with the use of conventional voltmeters and an indicating arrangement with desirable test features. 
     2. Description of the Related Art 
     In the field of electrical power distribution, it is a common practice to perform phasing measurements between various power cables to determine the phase difference between and the correct connection of the power cables throughout the system. Various prior art arrangements include indicator lights that respond to sensed voltage signals to indicate whether two signals are in phase or out of phase. For example, device types HOMPK and HO-PV are available from ELSIC, Trompeterallee, Germany. Further, page 14 of Merlin Gerin Publication AC0063/3E illustrates voltage indicator lamps and a phase concordance unit designated MX 403. 
     Additionally, various devices are known that respond to voltage sensors and that function as voltage indicators. An arrangement for testing the integrity of the voltage sensing system is shown in U.S. Pat. No. 5,521,567. 
     While these prior art arrangements may be useful to provide various indicator and phasing arrangements, the prior phasing arrangements are rather awkward to operate, require manipulation and interconnection of various components, require relatively expensive sensing devices, require the use of specialized meters or devices, and/or require external power supplies. Further, the prior indicator arrangements require separate power supplies for testing and do not provide simplified unambiguous self-testing functions. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a principal object of the present invention to provide an arrangement that is responsive to a voltage sensor and determines phase information that is measurable with a voltmeter. 
     It is another object of the present invention to provide a method to verify phasing between different electrical sources with the use of a voltmeter and such that the phasing determination is independent of the source voltage. 
     It is a further object of the present invention to provide a phasing arrangement that is responsive to two or more alternating current sources and that provides phasing information as the AC voltage between outputs representing each of the two of the alternating-current sources. 
     It is yet another object of the present invention to provide a voltage indicator arrangement for an electrical source that includes a sensorially perceptible voltage indicator and a sensorially perceptible test indicator that clearly establishes a test mode of the voltage indicator arrangement. 
     It is an additional object of the present invention to provide a voltage indicator arrangement that is self-powered in a test mode by a photocell. 
     It is a still further object of the present invention to provide a voltage indicator arrangement that includes a test mode that tests the integrity of a voltage indicator utilizing substantially the same signal that is provided during normal operation. 
     These and other objects of the present invention are efficiently achieved by the provision of a phasing and indicator arrangement that responds to electrical sources and provides voltage indicator functions, phasing determinations, and self-test features. 
     Phasing provisions are responsive to two or more voltage sensors proximate respective electrical sources to provide an output that represents the phase difference, i.e. time relationship, between the electrical sources as an alternating-current voltage measurable by a voltmeter. The output is relatively independent of the voltage of the electrical sources. 
     The indicator arrangement is operable in a test mode to test the integrity of one or more voltage indicators while clearly identifying that the indicator arrangement is in a test mode. In a preferred arrangement, the indicator arrangement in the self-test mode is powered by a photocell. Further, in the self-test mode, the indicator arrangement generates signals through each voltage sensor and over the complete voltage sensing path, the generated signals being substantially similar to the signals generated by each voltage sensor during normal operation in response to an alternating-current source. In the self-test mode, the phasing arrangement is also tested. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the specification taken in conjunction with the accompanying drawing in which: 
     FIG. 1 is a block diagram representation of a phasing arrangement of the present invention; 
     FIG. 2 is a diagrammatic representation of various signals in the phasing arrangement of FIG. 1; 
     FIG. 3 is a diagrammatic representation of an indicator or display arrangement which utilizes the phasing arrangement of FIG. 1; and 
     FIG. 4 is a block diagram electrical schematic diagram of portions of the indicator or display arrangement of FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, the phasing arrangement  10  of the present invention provides phasing outputs at  12 ,  14 , and  16 , e.g. corresponding to a three-phase alternating-current electrical system. The outputs  12 ,  14  and  16  provide phase information that corresponds to each of the respective phases or electrical sources  31 ,  33  or  35  of the electrical system while being relatively independent of the voltage on each phase. An alternating-current voltmeter  20  with leads  22 ,  24  placed across two of the phasing outputs measures the phase difference, i.e. time relationship, e.g. as a voltage generally proportional to the phase difference. 
     The phasing arrangement  10  includes sensors  30 ,  32  and  34  that provide respective outputs  36 ,  38  and  40  which are proportional to the associated respective electrical source or phase line  31 ,  33  or  35  of the electrical system. Each of the outputs  36 ,  38  and  40  is connected to the input of a respective power conditioning stage  42 ,  44  and  46 . In a specific embodiment, the outputs  36 ,  38  and  40  are high-impedance outputs such that the power conditioning stages  42 ,  44  and  46  isolate the high impedance outputs  36 ,  38 , and  40  of the sensors  30 ,  32  and  34  and provide the phasing outputs  12 ,  14  and  16 . In a specific embodiment, the outputs  36 ,  38  and  40  are sinusoidal waveforms representative of the electrical sources. The power conditioning stages  42 ,  44  and  46  convert each of the sinusoidal waveform outputs at  36 ,  38  and  40 , via clamping action or the like, to waveforms at the phasing outputs  12 ,  14  and  16  that are substantially square waves. 
     With additional reference now to FIG. 2, the waveforms  70 ,  72  and  74  represent the signals at the respective phasing outputs  12 ,  14  and  16 , the waveforms  70 ,  72  and  74  containing the phase information of the respective electrical sources or phase lines  31 ,  33  and  35  sensed by the respective sensors  30 ,  32  and  34 . 
     The waveform  76  in FIG. 2 corresponds to a fourth phasing output  15  in FIG. 1 of another electrical source  37  sensed by a sensor  29  having an output  39  connected to a power conditioning stage  41 , the power conditioning stage  41  providing the phasing output  15 . For example, in a specific illustration, the electrical source  37  represents “phase one” of a “second way” or 3-pole circuit path of the electrical system while the electrical source  31  represents “phase one” of a “first way” or 3-pole circuit path. 
     Before connecting the electrical sources  31  and  37  together via a switch or the like, the phase relationship between the two sources  31  and  37  is determined or verified via measuring the voltage between the respective phasing outputs  12  and  15  which are represented by the respective waveforms  70  and  76 . If the voltage difference measured on the AC voltmeter  20  is below a predetermined level, the electrical sources  31  and  37  of the two ways are suitable for connecting to the same bus. However, if the voltage difference is above a predetermined level establishing that a significant phase difference exists between the two sources, the two electrical sources should not be interconnected. Accordingly, in accordance with important aspects of the present invention, the phase difference between various electrical sources can be measured via the voltage between the corresponding phasing outputs. 
     As illustrated in FIG. 2, the two waveforms  70  and  76  (corresponding to electrical sources  31  and  37 ) are of relatively the same phase or time relationship and are thus suitable for interconnection. For example, if the two electrical sources  31  and  37  are exactly in phase, i.e. 0 degrees phase difference, then the voltage measured between the phasing outputs  12  and  15  would be essentially zero volts. On the other hand, the phase difference between the two electrical sources  31  and  33  is significant (as illustrated in FIG. 2 by waveforms  70  and  72 ). Thus these two electrical sources  31  and  33  are not suitable for interconnection, which can be ascertained via the measurement of the voltage differential between the corresponding phasing outputs  12  and  14 . Specifically, as shown in FIG. 2, the two electrical sources  31  and  33  are approximately 120 degrees out of phase with respect to each other and in the example correspond to two different phases of the first way of the electrical system. 
     For illustrative purposes not to be interpreted in any limiting sense, it has been found that the phasing outputs operate in a desirable fashion for a voltage range of approximately 15-38 kv (phase-to-phase) AC and such that no calibration or adjustment is required to measure the phase differential using the phasing outputs, the magnitude of the waveforms in FIG. 2 being approximately 15 volts peak-to-peak. In a particular example, if the phasing output  12  to ground measures V 1  to ground, the voltage from output  12  to output  14  is approximately V 1  times the square root of 3. Further, the voltage differential between phasing outputs  12 ,  15  is less than (V 1 )/3 for the illustration where the waveforms  70 ,  76  are less than 10 degrees out of phase with respect to each other. As stated in other terms, the phasing arrangement  10  of the present invention establishes a voltage between the phasing outputs that characterizes or establishes a relationship between the measured AC voltage and the phase difference (time relationship) between the sensed electrical lines, i.e. a predetermined function between phase difference and voltage. As noted, it should also be understood that the phasing outputs  12 ,  14 ,  16  and  15  can also be utilized to verify the presence of voltage of the electrical sources, i.e. via the voltage measured phase to ground. It should also be understood that in specific embodiments of the present invention where additional accuracy of the phase differential measurement is desired, the power conditioning stages  41 ,  42 ,  44  and  46  include additional wave shaping circuitry to provide waveforms that are more accurately measured by AC voltmeters and the like. 
     Referring now additionally to FIGS. 3 and 4, in a specific embodiment, the phasing arrangement  10  is provided as an integral part of an indicator or display arrangement as represented by  50  in FIG.  3 . In an illustrative embodiment, not to be interpreted in any limiting sense, the indicator arrangement  50  is utilized as the display panel referred to as item 40 in the aforementioned copending application Ser. No. 08/705,460, now U.S. Pat. No. 5,864,107 to provide information about the status of the circuit and components of the switchgear  20  shown in that application such as the energized/deenergized status of each pole of the overlied load interrupter switch or fault interrupter. 
     For example, as shown in FIG. 3, the indicator arrangement  50  includes, for each pole, a voltage indicator  52  and a line diagram  54  representing the electrical circuit and the load interrupter switch or fault interrupter (a load interrupter switch being illustrated in FIG.  3 ). A test indicator  60  and the voltage indicator  52  provide information on the operable status of the indicator arrangement  50  and the integrity of the voltage sensing system for each pole. Reference may be made to U. S. Pat. No. 5,521,567 for a further discussion of the testing of the integrity of the voltage sensing system. The phasing outputs  12 ,  14  and  16  are provided for each respective phase of the circuit illustrated at pins or posts  112 ,  114 , and  116 . 
     In the illustrative example of the indicator arrangement  50 , the test indicator  60  displays a predetermined test symbol, e.g. a solid circle, when the indicator arrangement  50  is appropriately sequenced for testing. In the specific illustration, for testing purposes, a solar panel (i.e. photocell)  64  is provided to power the indicator arrangement  50 . Additionally a test actuator  66  is provided that includes a transparent window over an optical switch at  92 . The test sequence is actuated in response to the blocking of light to the optical switch at  92  while the solar panel  64  is illuminated sufficiently to provide power to actuate the indicator arrangement  50  and test circuit. Thus, after the user covers the test actuator  66 , the display of the test symbol in the test indicator  60  provides assurance that the indicator arrangement  50  is appropriately powered up and fully functioning. With the test indicator displayed at  60 , the user may then ascertain the operability of each voltage indicator  52  and the integrity of the voltage sensing circuit for that corresponding pole. Thus, the presence of the test symbol at  60  and the three voltage indicators at  52  assure that the overall voltage sensing system is functioning appropriately. 
     In a specific embodiment, the voltage indicator  52  flashes the energized symbol, e.g. lightning bolt or the like, in the test mode to verify that the voltage indicator  52  is functional and the voltage sensing circuit is fully functional and reliable. Following this test function, i.e. after the operator unblocks the transparent window over the optical switch at  66 , the energized/deenergized status of each pole may then be ascertained via the status of the voltage indicator  52  provided for each respective pole, for example  52   b  and  52   c  for the respective second and third poles of the indicator arrangement  50 . In a specific embodiment, while the voltage indicators  52  are arranged for normal functioning, the operator before relying on the absence of an energized symbol at the voltage indicator  52 , activates the testing mode of the indicator arrangement via the feature at  66  and observes the test symbol at  60  and checks for the presence of the energized symbols at  52   a,    52   b  and  52   c  to determine proper operation. Without such appropriate testing, the voltage indicators  52  in themselves would function only as ordinary indicators as found in the prior art. 
     Referring now additionally to FIG. 4, the testing circuit  90  of the indicator arrangement  50  is powered by the solar panel  64  and actuated by the test actuator feature at  66 . When the optical switch  92  is turned off by the blocking of light at  66 , the optical switch  92  via path  94  activates a power regulator stage  96 . The power regulator stage  96  supplies power to the power converter and signal generator stages referred to at  98  which actuate the test indicator  60  with a suitable alternating wave signal at  100 . The alternating wave signal at  100  via a surge protection stage  102  provides signals for each phase at  104  which are connected to the sensors  30 ,  32  and  34 . This signal path tests the integrity of the overall sensing circuit. If the sensing path is fully functioning, the signal will be returned at  106  on the lines from the bushing sensors  30 ,  32  and  34 . The signal at  106  is then processed by a power condition and logic stage  108  which provides protection and the desired indicator waveform at  110  to drive the voltage indicator  52 , e.g. a flashing signal. 
     Accordingly, the testing circuit  90  of the indicator arrangement  50  when actuated by the test actuator feature at  66  checks the integrity of the signal paths from the sensor and activates the voltage indicators at  52  to also test the integrity of the voltage indicators  52 . As discussed hereinbefore, if any of the voltage indicators  52  are not actuated during the testing mode with the testing indicator  60  actuated, the operator is alerted that the voltage indicators  52  are not working and not to be relied upon. 
     The power condition and logic stage  108  also is arranged to provide appropriate phasing signals at the phasing outputs  12 ,  14  and  16  as explained hereinbefore, such that the phasing outputs provide phasing information that is independent of the sensed voltage levels and such that an alternating-current voltmeter may be utilized to measure the phase difference between the phases or electrical sources  31 ,  33  or  35  of the electrical system. It should also be noted that the phasing outputs  12 ,  14  and  16  are also tested in the test mode of the indicator arrangement  50 , i.e. in the test mode, each of the phasing outputs  12 ,  14  and  16  develop a voltage to ground that can be measured using the AC voltmeter  20 . 
     For illustrative purposes not to be interpreted in any limiting sense, it has been found that the indicator arrangement  50  along with the phasing outputs operates in a desirable fashion for a voltage range of approximately 4-38 kv (phase-to-phase) AC and such that no calibration or adjustment is required to provide the indicator functions and testing and also to measure the phasing outputs. 
     While there have been illustrated and described various embodiments of the present invention, it will be apparent that various changes and modifications will occur to those skilled in the art. Accordingly, it is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present invention.