Abstract:
A controller for a voltage regulator has an input keypad for designating selected operating parameters of the voltage regulator. The keypad is formed with a dedicated function portion and a menu navigation portion, and the parameters are divided into first and second categories. The controller has a display for displaying the parameters, and a computer is connected to the input and to the display for controlling the display in response to activation of the keypad. Any parameter in the first category can be displayed on the display by activation of the dedicated function portion of the keypad. Any parameter in the second category can be displayed by activation of the menu navigation portion. The menu navigation portion can optionally also be used to control display of parameters in the first category.

Description:
This is a continuation of application Ser. No. 07/950,402, filed Sep. 23, 1992. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to apparatus for controlling a voltage regulator and more particularly to a novel and highly effective “man-machine interface” that enables a user of the apparatus easily and efficiently to display and control selected parameters of the voltage regulator. 
     2. Description of the Prior Art 
     In conventional practice, the parameters of a voltage regulator are accessed by means of physical switch settings, both for viewing and for configuration. Some control systems employ numerical identification codes entered by a keypad for the purpose of viewing and modifying system parameters. These conventional mechanisms are limited in the number of physical parameters available for access because of physical space restrictions and often require a chart or index list that must be consulted by an operator in order to access the parameters. 
     Operation of a keyboard or other interfacing device for data input should be efficient, easy, and even to a degree intuitive. Though often criticized as less than perfect, the QWERTY layout of a conventional typewriter keyboard, for example, is preferred by most users to an alphabetical layout (ABC . . .) in part because the former places the “E” key and other relatively frequently used keys in positions that are more accessible than, for example, that of the “Q” key and other relatively infrequently used keys. 
     It has been found that interfaces developed heretofore for permitting access to various parameters of voltage regulators are very awkward to use. 
     Representative prior art relating to menus, user interfaces, and keypads is found in U.S. Pat. Nos. 361,730, 4,503,291, 4,628,158, 4,645,874 and 5,077,582. The apparatus and techniques disclosed in these patents are representative of the current state of the art in this field; they do not enable an operator of a voltage regulator control to gain access to system parameters for viewing and modification with great ease and efficiency. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the invention is to remedy the deficiencies of the prior art noted above and in particular to provide apparatus for controlling a voltage regulator that improves the ease and efficiency with which an operator of a voltage regulator can gain access to voltage regulator parameters for viewing and modification. 
     Another object of the invention is to provide apparatus for controlling a voltage regulator that enables an operator in effect to “scan” and, if necessary, adjust the operating parameters of a voltage regulator in rapid succession. 
     Another object of the invention is to provide apparatus for controlling a voltage regulator the operation of which requires no special training. 
     Another object of the invention is to provide apparatus for controlling a voltage regulator that enables a more rapid response to an alert condition or another condition requiring attention. 
     The foregoing and other objects are attained in accordance with the invention by the provision of apparatus for controlling a voltage regulator, the apparatus comprising: input means for designating selected operating parameters of a voltage regulator, the input means being formed with a dedicated function portion and a menu navigation portion and the parameters being divided into first and second categories; display means for displaying the parameters; and computer -means connected to the input means and the display means for controlling the display means in response to activation of the input means; the apparatus being constructed so that any parameter in the first category can be displayed on the display means by activation of the dedicated function portion and any parameter in the second category can be displayed on the display means by activation of the menu navigation portion. 
     Preferably, any parameter in the first category can also be displayed on the display means by activation of the menu navigation portion. 
     In the best mode for practicing the invention known to the inventors, the input means comprises a keypad, the dedicated function portion comprises a plurality of keys physically grouped together in a first area of the keypad, and the menu navigation portion comprises a plurality of keys physically grouped together in a second area of the keypad. 
     In accordance with an independent aspect of the invention, there is provided a method for controlling a voltage regulator, the method comprising the steps of: providing input means for designating selected operating parameters of a voltage regulator, the input means being formed with a dedicated function portion and a menu navigation portion and the parameters being divided into first and second categories; providing display means for displaying the parameters; activating the dedicated function portion to display parameters in the first category; and activating the menu navigation portion to display parameters in the first or second category. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the objects, features and advantages of the invention can be gained from a consideration of the following detailed description of the preferred embodiment thereof, in conjunction with the appended figures of the drawing, wherein a given reference character always refers to the same element or part, and wherein: 
     FIG. 1 is a view of a keypad and display interface and can be thought of as a plan view (if the keypad and display are oriented in a horizontal plane) or as an elevational view (if, as will be the usual case, they are mounted on a panel in a vertical plane), the keypad being a part of input means for designating selected operating parameters of a voltage regulator and the display being a part of means for displaying the parameters; 
     FIG. 2 is a schematic diagram showing the connection of the interface of FIG. 1 to a microcomputer; and 
     FIGS. 3A,  3 B,  3 C and  3 D constitute a flowchart helpful in understanding the operation of apparatus constructed in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Operational parameters, setpoints and special functions including metering parameters and local operator interfacing are accessed in accordance with the invention via any suitable switching device such as membrane contact switches. The layout of the membrane keypad can be varied but has characteristics illustrated in FIG.  1 . 
     The keypad is designed to provide direct (i.e., single keystroke) access to regularly used functions, plus quick access (via a menu arrangement) to all of the remaining functions. 
     The buttons towards the bottom of the keypad (including Regulation Setting RS, Line Drop Compensation LDC, Power Flow Setting Mode PFS, Voltage Reduction Control VRC, Voltage Limit Control VLC, and Operation Counter OC) are dedicated function keys. They permit single-key access to the most commonly used functions. The buttons at the top of the display (including Cancel CNC, Save SV, Change CNG, Max/Min MX/MN, Menu M, and the Scroll or arrow keys SU, SD, SL, SR surrounding the Menu key) are configuration/select or menu navigation keys. They permit access (through menu screens) to all of the control features, including those that can be accessed by a single keystroke of one of the dedicated function keys. 
     Configuration/Select Keys 
     The configuration/select or menu navigation keys include the scroll keys (arrows), Menu, Cancel, Save, Change, and Max/Min. These keys are physically grouped together, for example in an upper part of the keypad. 
     The ↑ (scroll up or SU) and ↓ (scroll down or SD) arrow keys respectively above and below the Menu key permit the user to move upward and downward, respectively, through the menu headings. The → (scroll right) and ← (scroll left) arrow keys respectively to the right and left of the Menu key permit the user to move forward and backward, respectively, through the items under the menu headings. The Menu key allows the user to quickly return to the menu heading level. Pressing Menu twice turns the user to the top of the menu headings list. 
     By means of this interface, an operator can view and/or change the unit&#39;s configuration. When a window with a configuration parameter is displayed, a cursor appears at the parameter. To change the parameter value, the user presses the Change key. 
     For numeric parameters, a cursor appears at the least significant digit or, in the preferred embodiment of the invention, the least significant digit flashes. The → and ← keys are used to position the cursor on the digit to be changed. The ↑ and ↓ keys are used to change the numeric value. Once the desired value is displayed, the user presses the Save key to save the revised value. 
     For alphabetic parameters, pressing the ↑ and ↓ keys show the different choices for that parameter. Once the desired value is displayed, the user presses the save key to save the revised value. 
     To get out of the “Change” Mode without saving, the user presses the Cancel key. 
     If either Save or Cancel is pressed to exit the “Change” Mode, the display continues to show the screen that was previously being edited. 
     To view the minimum and maximum stored values for a meter parameter, the user first displays the instantaneous value for the meter parameter. Pressing Max/Min once shows the maximum value for the parameter. Pressing Max/Min again shows the minimum value for that parameter. (The Max/Min key press activates a temporary display of the maximum or minimum value. If the Max/Min key is pressed once, the controller returns to displaying the instantaneous value after about 5 seconds. If the Max/Min key is pressed twice, the minimum value is displayed. If no more keys are pressed, the display reverts (after about 5 seconds) to the instantaneous meter value. If the Max/Min key is pressed while the minimum value is displayed, the maximum value is displayed again.) 
     If Cancel is pressed while the minimum or maximum value of a meter parameter is displayed, it causes these values to change to the value shown for the instantaneous meter parameter. 
     If either the → or ← the key is pressed while a minimum or maximum value is being displayed, the next or previous item screen will be displayed, respectively. 
     The operating rules for the configuration/select keys are summarized in Table 1 below: “Rules for Configuration/Select Keys”. In the table, “Menu Level” refers to the heading level, e.g., Configure, Regulator, Meter, FW Demand, etc. . . . “Item” refers to any screen below the menu level; e.g., [Type: straight], [Syst: Wye], etc.} 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 RULES FOR CONFIGURATION/SELECT KEYS 
               
             
          
           
               
                 Key 
                 Menu Level 
                 Display: Normal 
                 Display: “Change” 
               
               
                   
               
               
                 Cancel 
                 Displays Help message. 
                 When “min” (or “max”) value is 
                 Returns to value 
               
               
                   
                   
                 being displayed, resets “min” (or 
                 shown before 
               
               
                   
                   
                 “max”) to present value. When 
                 Change Mode was 
               
               
                   
                   
                 viewing KQHR, KWHR, and 
                 entered. Exits 
               
               
                   
                   
                 Elapsed Ops screens, clears value 
                 Change Mode. 
               
               
                   
                   
                 to zero. 
               
               
                 Save 
                 No effect 
                 No effect 
                 Stores the new 
               
               
                   
                   
                   
                 value(s). Exits 
               
               
                   
                   
                   
                 Change Mode. 
               
               
                 Change 
                 Displays Help message. 
                 Enters “Change Mode”, indicated 
                 No effect. 
               
               
                   
                   
                 by a change in the cursor type. 
               
               
                 Max/Min 
                 No effect 
                 If a meter value is being displayed, 
                 No effect. 
               
               
                   
                   
                 shows maximum reading for that 
               
               
                   
                   
                 parameter. If maximum reading 
               
               
                   
                   
                 being displayed, shows minimum 
               
               
                   
                   
                 value for the paramter. Times 
               
               
                   
                   
                 out after 5 seconds, display 
               
               
                   
                   
                 reverts to the instantaneous meter 
               
               
                   
                   
                 screen. 
               
               
                 Menu 
                 Shows message: “Start of 
                 Returns window to “Menu” level. 
                 No effect. 
               
               
                   
                 Menus” for ˜2 seconds, 
                 Displays menu screen for the item 
               
               
                   
                 then shows 1st menu 
                 that was active. 
               
               
                   
                 screen. 
               
               
                 ↑ 
                 Shows previous menu. At 
                 No effect. 
                 Changes value of 
               
               
                   
                 1st menu, shows “Menus 
                   
                 parameter/digit 
               
               
                   
                 Start/End” for ˜2 seconds 
                   
                 downward 
               
               
                   
                 seconds then shows last 
               
               
                   
                 menu screen. 
               
               
                 ↓ 
                 Shows next menu. At last 
                 No effect. 
                 Changes value of 
               
               
                   
                 menu, shows “Menus 
                   
                 parameter/digit 
               
               
                   
                 Start/End” for ˜2 seconds 
                   
                 downward 
               
               
                   
                 then shows 1st menu 
               
               
                   
                 screen. 
               
               
                 ← 
                 Displays last item screen 
                 Shows previous item screen. If 
                 Moves “Change 
               
               
                   
                 for that menu. 
                 present screen is 1st item screen, 
                 cursor” from right 
               
               
                   
                   
                 shows the menu screen for that 
                 to left. 
               
               
                   
                   
                 item. 
               
               
                 → 
                 Displays 1st item screen 
                 Shows next item screen. If 
                 Moves “Change 
               
               
                   
                 for that menu. 
                 present screen is last item screen, 
                 cursor” from left to 
               
               
                   
                   
                 shows the menu screen for that 
                 right. 
               
               
                   
                   
                 item. 
               
               
                   
               
             
          
         
       
     
     Setpoint keys 
     The Setpoint Keys or designated function keys permit single key access to several of the display screens. Each of these screens can be viewed with a single keystroke, but they require the “Change Mode” (i.e., an Edit Mode) to be enabled before the contents can be changed. 
     Pressing any of the Setpoint Keys has no effect if the display is currently in the Change Mode. 
     The operating rules for the Setpoint keys are listed in Table 2 below: “Rules for Setpoint Keys”. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 RULES FOR SETPOINT KEYS 
               
             
          
           
               
                 BUTTON 
                 DESCRIPTION 
               
               
                   
               
               
                 Regulation 
                   
               
               
                 Setting: 
               
               
                 Bandwidth 
                 Directly accesses (forward) Bandwidth setting screen for regulator 
               
               
                   
                 control. Pressing while FW screen is displayed causes RV screen to be 
               
               
                   
                 shown and vice-versa. 
               
               
                 Voltage Level 
                 Directly accesses (forward) Voltage Level setting screen for regulator 
               
               
                   
                 control. Pressing while FW screen is displayed causes RV screen to be 
               
               
                   
                 shown and vice-versa. 
               
               
                 Time Delay 
                 Directly accesses (forward) Time Delay setting screen for regulator 
               
               
                   
                 control Pressing while FW screen is displayed causes RV screen to be 
               
               
                   
                 shown and vice-versa. 
               
               
                 Line Drop 
               
               
                 Compensation: 
               
               
                 Resistance 
                 Directly accesses (forward) Line Drop Compensation Resistance setting 
               
               
                   
                 screen for regulator control. Pressing while FW screen is displayed 
               
               
                   
                 causes RV screen to be shown and vice-versa. 
               
               
                 +/− 
                 If Line Drop Compensation 
               
               
                   
                 Resistance or Reactance screen is presently being displayed and the 
               
               
                   
                 “Change mode” is enabled, this button toggles between positive and 
               
               
                   
                 negative compensation. Otherwise, it has no effect. 
               
               
                 Reactance 
                 Directly access (froward) Line Drop Compensation Reactance setting 
               
               
                   
                 screen for regulator control. Pressing while FW screen is displayed 
               
               
                   
                 causes RV screen to be shown and vice-versa. 
               
               
                   
               
             
          
         
       
     
     Special Function Keys 
     The Special Function keys permit single key access to several of the display screens. Each of these screens can be viewed with a single keystroke, but they require the “Change Mode” to be enabled before the contents can be changed. 
     Pressing any of the Special Function keys has no effect if the display is currently in the Change Mode. 
     The operating rules for the Special Function keys are listed in Table 3 below: “Rules for Special Function Keys”. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 RULES For SPECIAL KEYS 
               
             
          
           
               
                 BUTTON 
                 DESCRIPTION 
               
               
                   
               
               
                 Power Flow Setting 
                 Directly access Power Flow Setting screen for regulator control. 
               
               
                 Mode: Select 
               
               
                 Voltage Reduction 
                 Directly accesses Voltage Reduction Control “mode select” screen. If 
               
               
                 Control: Select 
                 pressed while VRC setting screen is active, will toggle to next VRC setting 
               
               
                   
                 screen, eventually wrapping around to the “VRC mode select” screen. 
               
               
                 Voltage Limit Control: 
                 Directly accesses Voltage Limit Control-Upper Voltage setting screen. If 
               
               
                 Select 
                 pressed while upper voltage setting screen is displayed, will toggle to lower 
               
               
                   
                 voltage setting screen. If pressed while lower voltage setting screen is 
               
               
                   
                 displayed, will toggle to VLC State screen. If pressed while VLC State 
               
               
                   
                 screen is displayed, will toggle to VLC upper voltage setting screen. 
               
               
                 Operation Counter: 
                 Directly accesses &lt;MENU:COUNTER&gt;[Total Ops = NN..N] display screen. 
               
               
                 Select 
                 If pressed while any &lt;MENU:COUNTER&gt; display screen is shown, will 
               
               
                   
                 toggle to next &lt;MENU:COUNTER&gt; display screen. If this key is pressed 
               
               
                   
                 while Automatic/Manual toggle switch is in Manual position, the 
               
               
                   
                 [Tap:NN..N] screen is displayed. Subsequent presses will toggle through 
               
               
                   
                 the &lt;MENU:COUNTER&gt; display screens in the order indicated in Table 3, 
               
               
                   
                 eventually wrapping to the 1st counter screen. 
               
               
                   
               
             
          
         
       
     
     Indicators 
     The user interface supports two methods of displaying status information—via an alphanumeric display module  19 , and via individual status indicators. The individual status indicators provide a direct means of assessing the regulator operating conditions. 
     A lamp  21  is illuminated to show that the tap changer is in the neutral position. 
     High, Low, and In-Band indicators  22 ,  23 ,  24  respectively show the status of the instantaneous sensed voltage relative to the voltage level and bandwidth setpoints. The “sensed voltage” includes the effect of line drop compensation, if active. 
     An ALERT indicator  25  is turned on in response to an active ALERT status. The ALERT indicator  25  remains on as long as any ALERT conditions remain in effect. 
     A communication indicator  26  activates whenever data transfer is in process across one or more of the controller&#39;s communications ports. Optionally, the communications indicator can be activated and left on if any configuration is performed remotely. 
     An RPF indicator  27  activates when the reverse current magnitude exceeds a predetermined threshold. 
     A Voltage Reduction Control (VRC) indicator  28  activates whenever the controller activates Voltage Reduction. A unique and distinct pattern of flashing can optionally be generated for each level of voltage reduction. 
     Voltage Limit Control (VLC) indicators activate when the regulator controller activates VLC. With the lower limit activated, the VIC Lower Indicator  29  is active. With the upper limit activated, the VLC Upper Indicator  30  is active. 
     Switches 
     A momentary switch  21  and several toggle switches  31 ,  32 ,  33  are provided for direct manual control. The momentary switch  21   a  when pushed down tests the lamp  21 . When pushed up, it resets the drag hands maximum and minimum tap position indicators on the electromechanical tap position indicator. The toggle switch  33  is a power switch and has a Normal position and an External Source position. The switch  32  has a Manual position enabling manual control and an Auto position enabling automatic control of tap changer position. The switch  31  is effective only when the switch  32  is in the Manual position and in the case can be used to raise or lower the tap changer. All three switches  31 - 33  (and, of course, the momentary switch  21   a ) have Off positions. 
     Local Configuration Communication Port 
     Any suitable local port  20  such as an RS232-compatible port is preferably provided for serial communication with other apparatus, for example a palmtop or other computer. The physical interface can be a 9-pin D-type connector whose pin-out meets any suitable industry standard, for example, matching the PC-AT RS232 port connector. The supported signals should ideally meet the electrical requirements of the most recent RS232 specifications, and the System port ideally supports data transmission and reception at standard data rates (from 300 to 19.2 kbaud, inclusive). 
     The system protocol can be an adaption of an existing standard communications protocol. The SEAbus protocol is one possible standard that may be adapted to implement the system port protocol. 
     The system is provided to support connection to a hand held communications device. The port supports transfer of data in both directions—allowing the controller to be configured via the serial link, and also providing meter and status information to a connected device. 
     In addition to supporting the configuration and data retrieval functions required for remote access, the system port should support uploading and/or downloading the program code for the main processor. 
     FIG. 2 is a block diagram of interface circuits used in accordance with the invention. Corresponding to the nineteen keys shown in FIG. 1, there are nineteen switches arranged in a 4×5 switching matrix  30 . The nine discrete light emitting diodes of FIG. 1 are shown collectively at  32  in FIG.  2 . 
     Each of the switches  30  is normally open and is closed when an operator or user of the apparatus presses it. 
     A computer  34 , which may be a Motorola MC68HC16Z1, writes the columns of the matrix through a column latch/driver and while each column is active polls the rows through a row buffer  38 . The column latch/driver can comprise for example a Motorola 74HC374 latch and an open drain 74HC05; the row buffer can comprise a schmitt trigger and output inverter, for example, Motorola 74HC14 and 74HC244. These are conventional components conventionally arranged and enable the microcomputer  34  to determine when any of the keys  30  is pressed. 
     The computer controls an LED latch/driver which can be formed of a Motorola 74HC374 and ULW2003A high current driver. The light emitting diodes  32  are turned on in accordance with instructions from the microcomputer  34 . 
     A first LED character display  42  for characters  1 - 8  is provided together with a second LED character display  44  for characters  9 - 16 . A data bus connects the microcomputer  34  to the column latch/driver  36  the row buffer  38 , the LED latch/driver  40 , the character display and the character displays  42  and  44 ; an address bus connects the microcomputer  34  to the character displays  42  and  44  for controlling the addresses of the displayed characters. 
     The structure of FIG. 2 is one example of components that can be employed in implementing apparatus in accordance with the invention for controlling a voltage regulator. 
     FIGS. 3A,  3 B,  3 C and  3 D form a flowchart helpful in understanding the operation of apparatus constructed in accordance with the invention. FIG. 3A discloses the menu mode, FIGS. 3B and 3C the normal mode, and FIG. 3D the change mode. 
     In response to a reset, the program at step  101  displays &lt;MENU: METER&gt; and waits for a key press at step  102 . When at step  102  a key press is detected as described above in connection with FIG. 2, the program investigates at step  103  whether a Config/Select key has been pressed. If so, a determination is made at step  104  whether a cancel or change key has been pressed. If so, since there is nothing to be canceled or changed, the program advances to step  108 , where a help message is displayed, and then the menu screen is displayed and the program recycles to step  102  to wait for another key press. 
     If at step  104  it is determined that a cancel or change key has not been pressed, then at step  105  a determination is made whether a save or max/min key has been pressed. If so, since there is nothing to be saved and the max/min key is also inoperative under this condition, the program loops back to step  102  to wait for another key press. 
     If at step  105  it is determined that neither a save nor a max/min key has been pressed, a determination is made at step  106  whether the ↑ or ↓ key has been pressed. If so, then at step  109 , in response to pressing the ↑ key, the previous menu is displayed; and, in response to pressing the ↓ key, the next menu is displayed. After performing the operation at step  109 , the program loops back to step  102  to wait for another key press. 
     If at step  106  it is determined that neither the ↑ key nor the ↓ key is pressed, a determination is made at step  107  whether the → key or the ← key has been pressed. If so, then at step  110  the next item screen is displayed in response to pressing the → key or the previous item screen in displayed in response to pressing the ← key. 
     If at step  103  it is determined that a config/select key has not been pressed, then at step  111  it is determined whether the +/− key has been pressed. If so, since this key is inoperative under such a condition, the program loops back to step  102  to wait for another key press. If at step  111  it is determined that the +/− key has not been pressed, then at step  112  the selected step setpoint or special function screen is displayed. 
     Following the display effected at step  110  or  112  or following a determination at step  107  that neither the → key nor the ← key has been pressed, the program advances to step  201  (FIG.  3 B), where it waits for another key press. When a key press is detected, the program advances to step  203 , where a determination is made whether the cancel/reset key has been pressed. If so, at step  204  the program determines whether a max or min screen is displayed. 
     If so, at step  205  the stored maximum or minimum value is reset to the present value, and the program loops back to step  201 . 
     If at step  204  it is determined that a max or min screen is not displayed, then at step  206  it is determined whether KQHR, KWHR, or elapsed Ops (see glossary below) is displayed. If so, then at step  207  the value is cleared, and the program loops back to step  201 . If at step  206  it is determined that none of the investigated parameters is displayed, the program loops back to step  201  without clearing any value. 
     If at step  203  it is determined that the cancel/reset button has not been pressed, then at step  208  it is determined whether the → key or the ← key has been pressed. If so, since this key is inactive at this point, the program loops back to step  201  to wait for another key press. 
     If at step  208  it is determined that neither the → key nor the ← key has been pressed, then at step  209  the program determines whether the save key has been pressed. If so, since there is nothing to be saved, the program loops back to step  201  and waits for another key press. 
     If at step  209  it is determined that the save key has not been pressed, then at step  210  it is determined whether the max/min key has been pressed. If so, then at step  211  it is determined whether a meter or max screen is displayed. If so, then at step  212 , the max screen is displayed if meter has been displayed, or the min screen is displayed if the max screen has been displayed, a timer is started, and the program loops back to stop  201 . (When the program returns to step  201  from step  212 , where the timer is set, the program looks both for the next key press and for a timer timeout. If a key press does not occur within a prescribed time, the timer times out, and the program advances to step  202  so that the meter value screen is displayed. The program then cycles back to step  201  to wait for the next key press. 
     If at step  211  it is determined that neither meter nor max screen is displayed, then at step  213  it is determined whether min screen is displayed. If so, then at step  214  the meter screen is displayed, the timer is cleared, and the program loops back to step  201 . 
     If at step  213  it is determined that the min screen is not displayed, the program loops back to step  201  without taking any further action. 
     If at step  210  it is determined that the max/min button has not been pushed, then at step  215  it is determined whether the → key or the ← key has been pressed. If so, then at step  216 , the previous screen is displayed if the ← key has been pressed or the next screen is displayed if the → key has been pressed. 
     If at step  215  it is determined that neither the ← key or the → key has been pressed, then the program advances to step  301  shown in FIG.  3 C. At step  301 , it is determined whether a change key has been pressed. If so, then at step  302  it is determined whether the change key is valid for the active screen. If not, the program loops back to step  201  in FIG.  3 B and waits for another key press. 
     If at step  301  it is determined that the change key has not been pressed, then at step  303  it is determined whether the +/− key has been pressed. If so, then at step  304  it is determined whether the resistance or reactance screen is displayed. If so, then at step  305  the polarity is toggled: that is, a + is changed to a − and a − to a +, and the program then loops back to step  201  in FIG.  3 B. 
     If at step  304  it is determined that neither the resistance nor reactance screen is displayed, the program loops back to step  201  without taking any further action. 
     If at step  303  it is determined that the +/− key has not been pressed, then at step  306  it is determined whether the power flow setting mode key has been pressed. If so, the power flow setting mode is displayed, and the program loops back to step  201  in FIG.  3 B. 
     If at step  306  it is determined that the power flow setting mode key has not been pressed, at step  308  it is determined whether the set point VRC, VLC or Ops counter key (see glossary below) has been pressed. If so, it is determined at step  309  whether the screen relating to the pressed key is currently active. If so, an alternate or next screen is displayed at step  310 , and the program loops back to step  201  in FIG.  2 B. 
     If at step  309  it is determined that the screen is not currently active, then at step  311  the selected screen is displayed, and the program loops back to step  201  in FIG.  3 B. 
     If at step  308  it is determined that neither a set point, VRC, VLC nor Ops counter key has been pressed, then an invalid key or error routine is performed at step  312 , and the program loops back to step  201  to wait for the next key press. 
     If at step  302  the change key investigated is determined to be valid for the activated screen, then the program advances to step  401  in FIG. 3C, where parameter/digit blinking is enabled. At step  402 , the program waits for the next key press. Upon the occurrence of the next key press, a determination is made at step  403  whether the cancel key has been pressed. If so, the program loops back to step  201  in FIG.  3 B and waits for the next key press. If a determination is made at step  403  that the cancel key has not been pressed, then at step  404  a determination is made whether the save key has been pressed. If so, then at step  405  the new values are stored, and the program loops back to step  201  of FIG. 3B to wait for the next key press. 
     If at step  404  it is determined that the save key has not been pressed, then at step  406  it is determined whether max/min, change or menu has been pressed. If so, the program loops back to step  402  to wait for the next key press. 
     If at step  406  it is determined that none of max/min, change and menu has been pressed, then at step  407  a determination is made whether the ↑ key or the ↓ key has been pressed. If so, then at step  408  the value of the parameter or digit is moved upward in response to pressing the ↑ key or downward in response to pressing the ↓ key. 
     If at step  407  it is determined that neither the ↑ key nor the ↓ key has been pressed, then at step  409  it is determined whether the ← key or the → key has been pressed. If so, then at step  410  the cursor is moved left or right, left in the case of the ← key being pressed, and right in the case of the → key being pressed, and the program loops back to step  402  to wait for the next key press. 
     If at step  409  it is determined that neither the ← key nor the → key has been pressed, then at step  411  it is determined whether the +/− has been pressed. If so, then at step  412  it is determined whether a resistance or a reactance screen is active. If so, then at step  413  the displayed polarity is reversed. 
     If at step  412  it is determined that a resistance or a reactance screen is not active, the program loops back to step  402  to await the next key press. 
     If at step  411  it is determined that the +/− key has not been pressed, then at step  414  it is determined whether the power flow setting mode key has been pressed. If so, then at step  415  the power flow setting mode screen is displayed and the program loops back to step  402  to wait for the next key press. 
     If at step  414  it is determined that the power flow setting mode key has not been pressed, then at step  416  it is determined whether the set point, VRC, VLC or Ops counter key has been pressed. If so, then at step  417  it is determined whether the screen is currently active. If so, the alternate or next screen is displayed at step  418  and the program loops back to step  402  to wait for the next key press. 
     If at step  417  it is determined that the screen is not currently active, then at step  419 , the selected screen is shown, and the program loops back to step  402  to wait for the next key press. 
     If at step  416  it is determined that none of the setpoint, VRC, VLC and Ops counter keys has been pressed, then, in view of the string of negative previous determinations at steps  403 ,  404 ,  406 ,  407 ,  409 ,  411  and  414 , an invalid key error routine is processed at step  420 , and the program then loops back to step  402  to wait for the next key press. 
     The following glossary of symbols is particularly helpful in interpreting Table 4 which follows the glossary. Table 4, including its continuation, has eight menu headings of display screens: namely, &lt;MENU:CONFIGURE&gt;, &lt;MENU:REGULATOR&gt;, &lt;MENU: METER&gt;, &lt;MENU:FW DEMAND&gt;, &lt;MENU:RV DEMAND&gt;, &lt;MENU:LOG SETUP&gt;, &lt;MENU:LOG/ALERT&gt;, &lt;MENU:COUNTER&gt;. Under these headings, various screens that can be displayed by the alphanumeric LED display  19  are shown. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 GLOSSARY OF SYMBOLS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 A 
                 Amps (if associated with Ild screen). 
               
               
                   
                 BW 
                 Bandwidth. 
               
               
                   
                 Comp 
                 (Line Drop) Compensation. 
               
               
                   
                 CT ratio 
                 Current Transformer ratio. 
               
               
                   
                 DA 
                 Day. 
               
               
                   
                 Dmd Subperiods 
                 Demand (Interval) Sub-periods. 
               
               
                   
                 Dmd Time 
                 Demand (Interval) Time. 
               
               
                   
                 F, FW or Fwd 
                 Forward. 
               
               
                   
                 Freq 
                 Frequency. 
               
               
                   
                 Hz 
                 Hertz (measure of frequency). 
               
               
                   
                 I 
                 I is a standard representation for 
               
               
                   
                   
                 electrical current, measured in Amperes. 
               
               
                   
                 Ild 
                 Load Current. 
               
               
                   
                 KQ 
                 Kilo-Vars (Vars = Volt-amp reactive). 
               
               
                   
                 KQHR 
                 Kilo var hours. 
               
               
                   
                 KVA 
                 Kilovoltamps measured at load. 
               
               
                   
                 KVARld 
                 Kilovars measured at load. 
               
               
                   
                 KW 
                 Kilo-Watts. 
               
               
                   
                 KWHR 
                 Kilowatt hours. 
               
               
                   
                 KWld 
                 Kilowatts measured at load. 
               
               
                   
                 Ld Pt 
                 Load Potential Transformer (ratio) 
               
               
                   
                 M 
                 Power Flow Direction; can be either “F” for 
               
               
                   
                   
                 forward, or “R” for reverse. 
               
               
                   
                 max 
                 Maximum. 
               
               
                   
                 min 
                 Minimum. 
               
               
                   
                 Mins 
                 Minutes. 
               
               
                   
                 MO 
                 Month. 
               
               
                   
                 NN . . . N 
                 Numerical value that the regulator 
               
               
                   
                   
                 controller displays; it cannot be changed 
               
               
                   
                   
                 (or entered) by the user. The number of N&#39;s 
               
               
                   
                   
                 indicates the number of digits used to 
               
               
                   
                   
                 display the parameter. 
               
               
                   
                 Ops 
                 operations. 
               
               
                   
                 PF 
                 Power Factor. 
               
               
                   
                 PFKVA min 
                 Power Factor at minimum KVA. 
               
               
                   
                 PFKVA max 
                 Power Factor at maximum KVA. 
               
               
                   
                 Pol 
                 Polarity 
               
               
                   
                 Pri 
                 Primary (of Regulator&#39;s Step down 
               
               
                   
                   
                 transformer). 
               
               
                   
                 Pt Threshold 
                 Potential Transformer Threshold. 
               
               
                   
                 Pwr Flow 
                 Power Flow (mode). 
               
               
                   
                 (R) 
                 Resistance (Line Drop Compensation). 
               
               
                   
                 R 
                 Reverse. 
               
               
                   
                 Rev 
                 Reverse 
               
               
                   
                 RV 
                 Reverse. 
               
               
                   
                 Sec 
                 Secondary (of Regulator&#39;s Step down 
               
               
                   
                   
                 transformer). 
               
               
                   
                 Src Pt 
                 Source Potential Transformer (ratio) 
               
               
                   
                 Vcomp 
                 Compensated Voltage. 
               
               
                   
                 VLC 
                 Voltage Limit Control. 
               
               
                   
                 Vld 
                 Load Voltage. 
               
               
                   
                 VRC 
                 Voltage Reduction Control. 
               
               
                   
                 VS 
                 Source Voltage. 
               
               
                   
                 (X) 
                 Reactance (Line Drop Compensation). 
               
               
                   
                 Xtrigger 
                 External Trigger. 
               
               
                   
                 XX . . . X 
                 Numeric value that can be user programmed. 
               
               
                   
                   
                 The number of X&#39;s indicates the number of 
               
               
                   
                   
                 digits used for this parameter. 
               
               
                   
                 YR 
                 Year. 
               
               
                   
                 YYYY . . . Y 
                 Numeric value that can be user programmed. 
               
               
                   
                   
                 The number of Y&#39;s indicates the number of 
               
               
                   
                   
                 digits used for this parameter. 
               
               
                   
                 ZZ . . . Z 
                 Alphabetic field that cannot be changed (or 
               
               
                   
                   
                 entered) by the user. 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 DISPLAY SCREENS 
               
             
          
           
               
                 1234567890123456 
                 1234567890123456 
                 1234567890123456 
                 1234567890123456 
               
               
                   
               
               
                 &lt;MENU:CONFIGURE&gt; 
                 &lt;MENU:REGULATOR&gt; 
                 &lt;MENU:METER&gt; 
                 &lt;MENU:FW DEMAND&gt; 
               
             
          
           
               
                 Type: 
                 STRAIGHT 
                 Fwd Volts: YYY.Y 
                 VId = NNNNN M 
                 F Dmd VId = NNNNN 
               
               
                   
                 INVERTED 
                 (YYY.Y = 106,134) 
                 VId = NNNNN M max 
                  max VId = NNNNN 
               
               
                   
                   
                   
                 VId = NNNNN M min 
                  min VId = NNNNN 
               
               
                 Syst: 
                 WYE 
                 Fwd BW: Y.Y V 
               
               
                   
                 DELTA LAG 
                 (YY.Y = 0.5,6.0,0.5) 
                 Vs = NNNNN M 
                 F Dmd IId = NNNNN 
               
               
                   
                 DELTA LEAD 
                   
                 Vs = NNNNN M max 
                  max IId = NNNNN 
               
               
                   
                   
                 Fwd Delay: YYYS 
                 Vs = NNNNN M min 
                  min IId = NNNNN 
               
             
          
           
               
                 Utility Pol: 
                 NORM 
                 (YYY = 0,180) 
                   
                   
               
               
                   
                 REV 
                   
                 Vcomp = NNNNN M 
                 PFKVAmax = NNNZZZZ 
               
             
          
           
               
                   
                 Fwd Comp(R): +/−YYV 
                 Vcomp = NNNNN M 
                 (ZZZZ = Lag, Lead) 
               
               
                 Ld PT YYYYY:XXX 
                 (YY = −24,24) 
                 Vcomp = NNNNN Mmin 
               
               
                  (YYYYY = 1500,15000) 
                   
                   
                 PFKVAmin = NNNZZZZ 
               
               
                  (XXX = 100,150) 
                 Fwd Comp(X): +/−YYV 
                 IId = NNNN A M 
                 (ZZZZ = Lag, Lead) 
               
               
                   
                 (YY = −24, 24) 
                 IId = NNNN A Mmax 
               
               
                 Src PT YYYYY:XXX 
                   
                 IId = NNNNN A Mmin 
                 F Dmd KW = NNNNN 
               
               
                 (YYYYY = 1500,15000) 
                 Rev Volts: YYY.Y 
                   
                  max KW = NNNNN 
               
               
                 (XXX = 100,150) 
                 (YYY.Y = 106,134) 
                 PF Lead = NNN 
                  min KW = NNNNN 
               
               
                   
                   
                 PF Lead = NNN max 
               
               
                 CTratio YYYY:X.X 
                 Rev BW: YY.Y V 
                 PF Lead = NNN min 
                 F Dmd KQ = NNNNN 
               
               
                  (YYYY = 120,7200) 
                 (YY.Y=0.5,6.0,0.5) 
                   
                  max KQ = NNNNN 
               
               
                 (X.X=0.1,9.5) 
                   
                 PF Lag = NNN 
                  min KQ = NNNNN 
               
               
                   
                 Rev Delay; YYYS 
                 PF Lag = NNN max 
               
             
          
           
               
                 Meter Volts: 
                 PRI 
                 (YYY =0,180) 
                 PF Lag = NNN min 
                 F Dmd KVA = NNNNN 
               
               
                   
                 SEC 
                   
                   
                  max KVA = NNNNN 
               
             
          
           
               
                   
                 Rev Comp (R): +/−YYV 
                 KVA = NNNNN M 
                  min KVA = NNNNN 
               
               
                 I Inhibit: YY% 
                 (YY =24,24) 
                 KVA = NNNNN Mmax 
               
               
                  (YY = 1,10) 
                   
                 KVA = NNNNN Mmin 
               
               
                   
                 Rev Comp (X): +/−YYV 
               
               
                 I Shift: YYY 
                 (YY =−24,24) 
                 KW = NNNNN M 
               
               
                  (YYYY = 000,359) 
                   
                 KW = NNNNN Mmax 
               
             
          
           
               
                   
                   
                 VCR Mode: 
                 OFF 
                 KW = NNNN Mmin 
               
               
                 Pwr Flow: 
                 F LOCK 
                   
                 LOCAL 
               
               
                   
                 R LOCK 
                   
                 REMOTE 
                 KQ = NNNNN M 
               
               
                   
                 IDLE R 
                   
                   
                 KQ = NNNNN Mmax 
               
             
          
           
               
                   
                 BI-DIR 
                 Local VRC%: YY.Y 
                 KQ = NNNNN Mmin 
               
               
                   
                 NEUT R 
                  (YY.Y=0,10) 
               
               
                   
                 CO-GEN 
                   
                 Freq = NN.NHz 
               
               
                   
                   
                 VRC Stage1: YY.Y 
                 Freq = NN.NHz max 
               
             
          
           
               
                 PT Threshold: YYY 
                 VRC Stage2: YY.Y 
                 Freq = NN.NHz min 
               
               
                  (YYY = 000,134) 
                 VRC Stage3: YY.Y 
               
               
                   
                  (YY.Y=0,10) 
                 KWHR F = NNNNNNNNN 
               
               
                 TIME: YY:YY 2 
                   
                 KQHR F = NNNNNNNNN 
               
             
          
           
               
                  (YY:YY = 1:00, 12:59) 
                 VRC Remote: 
                 MJ-X 
                 KWHR F = NNNNNNNNN 
               
               
                  (Z = A|P) 
                   
                 MJ3A 
                 KQHR F = NNNNNNNNN 
               
             
          
           
               
                 Date: YY/YY/YY 
                 MJ-3A VRC%: YY.Y 
                 KWHR R = NNNNNNNNN 
               
               
                  (YY/YY/YY = 
                 (YY.Y = 0,10) 
               
               
                  01/01/00, 12/31/99) 
               
             
          
           
               
                 DATE: 
                 MO/DA/YR 
                 VLC Enable: 
                 ON 
               
               
                   
                 DA/MO/YR 
                   
                 OFF 
               
             
          
           
               
                 DmdTime: YYYMins 
                 VLC upper: YYY.Y 
                   
                   
               
               
                  (YYY = 1,999) 
                  (YYY.Y = 120, 134) 
               
               
                 DmdSubperiods: YY 
                 VLC Lower: YYY.Y 
               
               
                  (YY = 1,99) 
                  (YYY.Y = 106,120) 
               
               
                 &lt;MENU:RV DEMAND&gt; 
                 &lt;MENU:LOG SETUP&gt; 
                 &lt;MENU:LOG/ALERT&gt; 
                 &lt;MENU:COUNTERS&gt; 
               
             
          
           
               
                 R Dmd VId = NNNNN 
                 Log Event: 
                 ON 
                 Alert: ZZZZZZZZZZ 
                 Total Ops = NNNNN 
               
               
                  max VId = NNNNN 
                   
                 OFF 
               
               
                  min VId = NNNNN 
                   
                   
                 “EventNN Values” 
                 Elapsed Ops = NNNN 
               
               
                   
                 Event = Tap: 
                 ON 
                 Event: NNNNNNN 
               
               
                 R Dmd IId = NNNNN 
                   
                 OFF 
                 Date: NN/NN/NN 
                 Reset NN/NN/NN 
               
               
                  max IId = NNNNN 
                   
                   
                 Teime: NN:NN:NN Z 
               
               
                  min IId = NNNNN 
                 Event = VLC: 
                 ON 
                 Cause: ZZZZZZZZZZ 
                 Reset NN:NN Z 
               
               
                   
                   
                 OFF 
                 VId = NNNN.N 
               
               
                 PFKVAmax = NNNZZZZ 
                   
                   
                 IId = NNNN.N 
                 Day Ops = NNNNN 
               
               
                  (ZZZZ = Lag, Lead) 
                 Event = VRC: 
                 ON 
                 PF = N.NN ZZZZ 
               
               
                   
                   
                 OFF 
                 KWId = NNNNN 
                 Month Ops = NNNNN 
               
               
                 PFKVAmin = NNNZZZZ 
                   
                   
                 KVARId = +/−NNNNN 
               
               
                  (ZZZZ = Lag, Lead) 
                 Log Interval: 
                 ON 
                 KVAId = NNNNN 
                 Years Ops = NNNNN 
               
               
                   
                   
                 OFF 
                 Event: NNNNNNN 
               
               
                 R Dmd KW = NNNNN 
                   
                   
                 Date: NN/NN/NN 
                 Tap = NNNNNNNN 
               
             
          
           
               
                  max KW = NNNNN 
                 Interval: YYHRYYM 
                 Time: NN:NN:NN Z 
                 (where NW...= 
               
               
                  min KW = NNNNN 
                   
                 Cause: ZZZZZZZZZZ 
                   “Neutral” 
               
             
          
           
               
                   
                 Log Xtrigger: 
                 ON 
                 VId = NNNN.N 
                   “NN Raise”, 
               
               
                 R Dmd KQ = NNNNN 
                   
                 OFF 
                 IId = NNNN.N 
                   “NN Lower” 
               
               
                  Max KQ = NNNNN 
                   
                   
                 PF = N.NN 
                 or “????????”) 
               
               
                  min KQ = NNNNN 
                   
                   
                 KWId = NNNNN 
               
               
                   
                   
                   
                 KVARId = NNNNN 
               
               
                 R Dmd KVA = NNNNN 
                   
                   
                 KVAId = NNNNN 
               
               
                  max KVA = NNNNN 
               
               
                  min KVA = NNNNN 
                   
                   
                 “IntervalNN Val” 
               
             
          
           
               
                   
                 Date: NN/NN/NN 
               
               
                   
                 Time: NN:NN:NN Z 
               
               
                   
                 VId = NNNN.N 
               
               
                   
                 Vld = NNNN.N max 
               
               
                   
                 VId = NNNN.N min 
               
               
                   
                 VId = NNNN.N dmd 
               
               
                   
                 IId = NNNN.N 
               
               
                   
                 IId = NNNN.N max 
               
               
                   
                 IId = NNNN.N min 
               
               
                   
                 IId = NNNN.N dmd 
               
               
                   
                 PF = N.NN 
               
               
                   
                 PF(KVAmax) = N.NN 
               
               
                   
                 PF(KVAmin) = N.NN 
               
               
                   
                 KWId = NNNNNN 
               
               
                   
                 KWId = NNNNN max 
               
               
                   
                 KWId = NNNNN min 
               
               
                   
                 KWId = NNNNN dmd 
               
               
                   
                 KVARId = NNNNN 
               
               
                   
                 KVARId = NNNNN max 
               
               
                   
                 KVARId = NNNNN min 
               
               
                   
                 KVARId = NNNNN dmd 
               
               
                   
                 KVAId = NNNNN 
               
               
                   
                 KVAId = NNNNN max 
               
               
                   
                 KVAId = NNNNN min 
               
               
                   
                 KVAId = NNNNN dmd 
               
               
                   
                   
               
             
          
         
       
     
     Thus there is provided in accordance with the invention a novel and highly effective man-machine interface for a voltage regulator that enables a user of the apparatus easily and efficiently to display and control selected parameters of the voltage regulator. The invention accomplishes all of the objects set out above. Many modifications of the preferred embodiment of the invention disclosed herein will readily occur to those skilled in the art. For example, the type of computer and other hardware employed can easily be changed, and the specific functions performed by the discrete signal lamps can be modified in the discretion of manufacturers or users of the apparatus. Accordingly, the invention extends to all subject matter that falls within the scope of the appended claims.