Abstract:
Methods, systems, and devices for controlling a serial arc fault in an electrical circuit are disclosed. In some embodiments, the methods include the following: a. measuring a current in the circuit; b. determining whether the current is below a predetermined value; c. if the current is below ten percent of the predetermined value, determining whether a countdown timer value indicated by a cell pointer value is equal to zero; d. if the countdown timer value is equal to zero, starting a countdown timer, advancing the cell pointer value by one, and restarting the method at step a.; e. if the countdown timer value is not equal to zero, determining whether the interruptions in the current are periodic; f. if the interruptions in the current are not periodic, checking whether an arc event countdown timer is running; and g. if the arc event countdown timer is running, tripping a circuit breaker.

Description:
BACKGROUND 
     Serial arc faults are typically created by the connecting or disconnecting of circuit connectors under load, a wire being broken or cut while under load, or a loose connection. As a result, an arc can be drawn between both ends impacted portion of the circuit. Serial arc faults act in series to a load and thus reduce current flowing through a circuit due to the additional resistance. Serial arc faults typically do not draw enough amperes to trip a circuit breaker. As a result, significant damage can occur if the arc is sustained for a period of time. Known technology for controlling serial arc faults fails to effectively address the issues presented by serial arc faults. 
     SUMMARY 
     Generally, the disclosed subject matter relates to systems, methods, and devices for controlling a serial arc fault in an electrical circuit. The current flowing through the electrical circuit is measured in real-time and further analyzed to identify the occurrence of a serial arc fault in the circuit. Upon identification, a circuit breaker is tripped to terminate the flow of current through the circuit and thus terminate the serial arc fault. 
     As defined herein, a serial arc fault is defined by the occurrence of two arc events in a two second timeframe. An arc event is defined herein by the occurrence of ten interruptions of the current that last 200 μs in 100 ms. As defined herein, an interruption is a point where the current drops below ten percent of the average current of the circuit. In addition, to meet the definition of an arc event, the interruptions can not be periodic. Generally, periodic interruptions are those that happen or recur at regular intervals. As defined herein, the interruptions are considered periodic if they all last longer than twenty-five percent of the time between interruptions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings show embodiments of the disclosed subject matter for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
         FIG. 1  is a diagram of a system and method according to some embodiments of the disclosed subject matter; 
         FIG. 2  is a chart of a method according to some embodiments of the disclosed subject matter; 
         FIG. 3  is a chart including an example of current flowing with a periodic wave form; 
         FIG. 4  is a chart including an example of current flowing with a non-periodic wave form; and 
         FIG. 5  is a diagram of a device according to some embodiments of the disclosed subject matter. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1-3 , some embodiments include systems, methods, and devices for controlling a serial arc fault in an electrical circuit. Some embodiments include a system  100  having a measurement module  102 , a control module  104 , and a circuit breaker module  106 , all of which are interconnected. 
     Measurement module  102  is in electrical communication with an electrical circuit  108 . In some embodiments, measurement module  102  is integrated in electrical circuit  108  and in some embodiments the measurement module is joined with the electrical circuit via a lead  110 . Measurement module  102  can be configured to both sense and measure current running through electrical circuit  108 . 
     Control module  104  includes a processor and computer readable medium (not shown), which can be included in a computing device  112 . The processor is configured to execute instructions contained on the computer readable medium. Generally, the instructions include continually measuring the current running through electrical circuit  108  and determining whether a serial arc fault has occurred. 
     Circuit breaker module  106  is joined with a circuit breaker  114  and is configured to adjustably control the flow of current through and a supply  116  of voltage across electrical circuit  108 . In some embodiments, circuit breaker module  106  is integrated in electrical circuit  108  and in some embodiments the circuit breaker module is joined with the electrical circuit via a lead  118 . When an occurrence of a serial arc fault in electrical circuit  108  is noted by control module  104 , circuit breaker module  106  trips circuit breaker  114  to terminate the flow of current through and voltage from supply  116  across electrical circuit  108 . 
     Referring now to  FIG. 2 , some embodiments of the disclosed subject matter include a method  200  of controlling a serial arc fault in an electrical circuit. At  202 , the electrical circuit is measured to determine if any current is running through the circuit or a sensor detects a current running through the circuit. At  204 , if no current is sensed, the method restarts at  202 . If current is sensed, i.e., the current is greater than zero, then at  206 , a warm-up countdown timer is started, and at  208 , when the warm-up countdown timer is started, a cool down countdown timer is reset. The warm-up and cool down countdown timers are included to prevent nuisance tripping of the circuit breaker during times, which can occur at the start and end of periodic loads where the period expands or contracts quickly, thereby falsely presenting characteristics of non-periodic interruptions. The circuit breaker cannot be tripped while either the warm-up or cool down countdown timers are running. 
     After the warm-up countdown timer reaches zero, at  210 , the current running through the electrical circuit is measured (“Xmeas”). At  212 , it is determined whether Xmeas is below a predetermined amount of a predetermined average current (“Xavg”) for the electrical circuit. In some embodiments, the predetermined amount is about ten percent. If Xmeas is not below Xavg by a predetermined amount, e.g., Xmeas is greater than ten percent of Xavg, method  200  restarts at  210  and the current running through the electrical circuit is re-measured. If Xmeas is below ten percent of Xavg for the electrical circuit, an interruption in the current noted and at  214  a countdown timer value in a data cell indicated by a cell pointer is reviewed. At  216 , it is determined whether the countdown timer value is equal to zero. If the countdown timer value is equal to zero, at  218 , a countdown timer is started in the data cell, the cell pointer value is advanced by one, and method  200  is restarted at  210  where the current running through the electrical circuit is re-measured. Typically, each countdown timer has a beginning value of 1000 units and each of the units is equal to 100 μs. 
     If at any time during method  200 , the countdown timer value in a first data cell, i.e., the first countdown timer started, reaches zero before a predetermined number of data cells are populated with countdown value timers, at  220 , all the countdown timer values in all the data cells are reset to zero, the cell pointer value is reset to a first position at the first data cell, and the method is restarted at  210 . In some embodiments, the predetermined number of data cells is about ten. 
     At  222 , if the countdown timer value is not equal to zero, it is determined whether the interruptions in the current are periodic. As discussed above and shown in  FIGS. 3 and 4 , a non-periodic wave form is one where all of the interruptions are do not last longer than twenty-five percent of the time between the interruptions and vice-versa for periodic wave forms. As explained further below, determining whether interruptions in the current are periodic includes first determining a difference between the countdown timer values of the last two of the predetermined number of data cells started. Then a threshold value is calculated by multiplying the difference by a predetermined value, e.g., twenty-five percent in some embodiments. Then the differences between adjacent ones of the countdown timer values of the remaining of the predetermined number of data cells started are calculated. The interruptions are not periodic if the differences are greater than the threshold value. 
     If the interruptions are periodic, at  224 , all countdown timer values are reset to zero, the cell pointer value is reset to a first position at the first cell, and method  200  is restarted at  210 . If the interruptions in the current are not periodic, at  226 , the occurrence of an arc event in the electrical circuit is noted and it is determined whether an arc event countdown timer is running. Generally, an arc event is defined as the occurrence of ten ( 10 ) interruptions of current that last 200 μs in 100 ms. If the arc event countdown timer is not running, at  228 , the arc event countdown timer having a predetermined beginning value is started and then method  200  is restarted at  210 . In some embodiments, the predetermined beginning value is two seconds. At  230 , if the arc event countdown timer is running, the occurrence of a serial arc fault in the electrical circuit is noted and a circuit breaker of the electrical circuit is tripped. Upon tripping the circuit breaker, at  232 , the cool down countdown timer is started and at  234 , the warm-up timer is reset. 
     Example 
     The following is an example of how one embodiment of method  200  is used to detect and control the occurrence of arc events and serial arc faults in an electrical circuit. 
     As discussed above and further illustrated in Tables 1-4 below, upon noting the occurrence of a first interruption in current, the value of countdown TIMER 1, which is positioned at a first data cell indicated by a cell pointer value V (in column 0), is set to 1000 units and pointer V is advanced to column 1. As mentioned above, each of the 1000 units is typically equal to 100 μs. 
     
       
         
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 Pointer 
                 V → 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Column 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                 Data Cell 
                 TIMER 1 
               
               
                 Timer 
                 1000   
               
               
                 Value 
               
               
                 Delta 
               
               
                   
               
             
          
         
       
     
     As shown in Table 2, on the next sensed interruption, for example, after 800 μs has elapsed, pointer V is at column one (1), the interruption is sensed, and the value of TIMER 2, which is positioned in a second data cell, is set to 1000 and pointer V is advanced to column 2. 
     
       
         
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
             
             
               
                 Pointer 
                   
                 V → 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Column 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                 Data Cell 
                 TIMER 1 
                 TIMER 2 
               
               
                 Timer 
                 992  
                 1000   
               
               
                 Value 
               
               
                 Delta 
                 8 
               
               
                   
               
             
          
         
       
     
     As shown in Table 3, on next sensed interruption, for example, after an additional 200 μs has elapsed, pointer V is at column two (2), the interruption is sensed, and the value of TIMER 3, which is positioned into a third data cell, is set to 1000 and pointer V is advanced to column 3. 
     
       
         
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
             
             
               
                 Pointer 
                   
                   
                 V → 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Column 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                 Data 
                 TIMER 
                 TIMER 
                 TIMER 3 
               
               
                 Cell 
                 1 
                 2 
               
               
                 Timer 
                 990  
                 998  
                 1000   
               
               
                 Value 
               
               
                 Delta 
                 8 
                 2 
               
               
                   
               
             
          
         
       
     
     Method  200  continues until 7 more interruptions are sensed or countdown TIMER 1 runs out, which would indicate that 100 ms has elapsed without detecting an arc event. If TIMER 1 runs to zero before ten interruptions are sensed, all of the TIMERS are cleared and method  200  restarts by measuring the current in the electrical circuit. 
     As shown in Table 4, in the case where ten interruptions are sensed within 100 ms, the TIMER values in all ten data cells are checked to determine whether the interruptions are periodic. The time between interruptions or the delta is calculated. If each is greater than twenty-five (25) percent of the last delta, e.g., 12 in the Table 4 example, it is not periodic and an arc event has occurred. As mentioned above, when an arc event is noted, the arc event countdown timer is checked. If the arc event countdown timer is running, that means that a second arc event has occurred within 2 seconds thereby indicating a serial arc fault. At that time, the circuit breaker is tripped. If the arc event countdown timer is not running, it is started and the current is measure per method  200 . If a second table filled and not periodic within before the arc event countdown timer runs to zero, it is an indication of a second arc event and thus a serial arc fault. 
     
       
         
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
             
             
               
                 Pointer 
                 V 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Column 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
               
               
                 Data Cell 
                 TIMER 1 
                 TIMER 2 
                 TIMER 3 
                 TIMER 4 
                 TIMER 5 
                 TIMER 6 
                 TIMER 7 
                 TIMER 8 
                 TIMER 
                 TIMER 
               
               
                 Timer Value 
                 540 
                 548 
                 550 
                 600 
                 800 
                 810 
                 820 
                 900 
                 9 
                 10 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                   
                 950 
                 990 
               
               
                 Delta (time 
                 8 
                 2 
                 50 
                 200 
                 10 
                 10 
                 80 
                 50 
                 50 
               
               
                 between 
               
               
                 interruptions) 
               
               
                 Delta deltas 
                 50 − 8 = 
                 50 − 2 = 48 
                 50 − 50 = 0 
                 50 − 200 = 150 
                 50 − 10 = 40 
                 50 − 10 = 40 
                 50 − 80 = 30 
                 50 − 50 = 0 
                 25% 
               
               
                 (is it &gt;25% 
                 42 
                 48 
                 0 
                 150 
                 40 
                 40 
                 30 
                 0 
                 of last 
               
               
                 of last delta, 
                 42 
                 &gt;12 
                 &lt;12 
                 &gt;12 
                 &gt;12 
                 &gt;12 
                 &gt;12 
                 &lt;12 
                 delta 
               
               
                 if yes, arc 
                 &gt;12 
                   
                   
                   
                   
                   
                   
                   
                 is 12 
               
               
                 event is non- 
               
               
                 periodic) 
               
               
                   
               
             
          
         
       
     
     Referring now to  FIG. 5 , some embodiments of the disclosed subject matter include a device  300  for controlling a serial arc fault in an electrical circuit  302 . Device  300  generally includes a housing  304 , which at least partially contains a measurement/sensor lead  306 , a processor and computer readable medium  308 , and a circuit breaker activator  310 . 
     Measurement/sensor lead  306  extends from an end  312  of housing  304 . Measurement/sensor lead is used for sensing and measuring a current running through electrical circuit  302 . Measurement/sensor lead  306  is typically adapted to be removably in electrical communication with electrical circuit  302 . 
     Processor and computer readable medium  308  is positioned within housing  304  and is communication with measurement/sensor lead  306 . The processor is generally configured to execute instructions contained on the computer readable medium. Generally, the instructions include continually measuring the current running through electrical circuit  302  and determining whether a serial arc fault has occurred. 
     Circuit breaker activator  310  is in communication with processor and computer readable medium  308  and a circuit breaker  314  for electrical circuit  302 . Upon occurrence of a serial arc fault in electrical circuit  302  as indicated by processor and computer readable medium  308 , circuit breaker activator  310  causes circuit breaker  314  of the electrical circuit to trip thereby discontinuing the flow of a current through and voltage from a power supply  316  across the electrical circuit. 
     Methods, systems, and devices according to the disclosed subject matter offer benefits and advantages over known technology. Using technology including the disclosed subject matter, serial arc faults are identified and terminated more rapidly, thus reducing the amount of damage caused by the faults. 
     Although the disclosed subject matter has been described and illustrated with respect to embodiments thereof, it should be understood by those skilled in the art that features of the disclosed embodiments can be combined, rearranged, etc., to produce additional embodiments within the scope of the invention, and that various other changes, omissions, and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.