Abstract:
The invention discloses a current direction detection module including a conversion unit, a bridge unit and an operation unit. The conversion unit has primary and secondary sides, wherein the secondary side has first and second ends. The bridge unit has first, second, third and fourth rectifying elements and first, second, third and fourth nodes. Each rectifying element has an anode and a cathode. The anode of the first rectifying element is coupled to the fourth rectifying element. The anode of the second rectifying element is coupled to the first rectifying element. The anode of the third rectifying element is coupled to the second rectifying element. The anode of the fourth rectifying element is coupled to the third rectifying element. The first and second nodes are coupled to the first and second ends. The operation unit amplifies two bridge voltages at the third and fourth nodes and outputs an operation voltage.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to a current direction detection module and, more particularly, to a current direction detection module that detects directions of faulty currents in an electric power system. 
         [0003]    2. Description of the Related Art 
         [0004]    Power distribution networks of an electric power system are widely arranged all over a country for industry development. The electric power systems should be maintained in an efficient way to provide better service quality during the operation thereof. Thus, when an abnormality occurs in the electric power system, it is required to quickly find out the location of the problem and the root cause thereof. In light of this, human labors are conventionally used to repair the electric power system. However, this may not be an efficient way anymore as the modern electric power systems are arranged on a very wide range. 
         [0005]    To solve the problem, many detection apparatuses have been developed to collect faulty information of an electric power system for centralized management. For instance, Taiwanese Publication Number 200837368 discloses a multi-ended fault location system, Taiwanese Publication Number 200933176 discloses a fault detection method of an electric power network and a system thereof, Taiwanese Patent Number 589651 discloses a protection relay, Taiwanese Patent Number 475991 discloses a fault point location system, Taiwanese Patent Number M379069 discloses a fault location device, and Taiwanese Patent Number M321170 discloses an automatic detection device for detecting faults of branched feed lines of a power distribution system. However, these conventional detection devices can only detect the occurrence of faulty currents in the electric power system rather than the directions of the faulty currents. As a result, the location of the problem can only be located by proceeding in a step-by-step manner starting from an area of the electric power system adjacent to the conventional detection devices. In a preferred case, if the directions of the faulty currents can be recognized, the problem will be quickly located. 
         [0006]    Furthermore, another conventional detection device detects directions of faulty currents via a directional over current relay. Specifically, the conventional detection device detects the directions of the faulty currents by acquiring voltage and current phase information via at least a potential transformer and at least a current transformer. However, the potential transformer cannot be used on a single transmission path and it is required to detect phase voltages thereof (L and N phases). In addition, the potential transformer should have its primary side connected to circuits of the electric power system. Thus, usage of the potential transformer makes it more difficult to detect the directions of the faulty currents. Moreover, the method requires higher costs because both the potential transformer and current transformer are used. 
         [0007]    Therefore, it is desired to improve the conventional detection devices. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore the primary objective of this invention to provide a current direction detection module without any potential transformer. 
         [0009]    The invention discloses a current direction detection module including a conversion unit, a bridge unit and an operation unit. The conversion unit has a primary side and a secondary side, wherein the secondary side has a first end and a second end. The bridge unit has a first rectifying element, a second rectifying element, a third rectifying element, a fourth rectifying element, a first node, a second node, a third node and a fourth node. Each of the first, second, third and fourth rectifying elements has an anode and a cathode. The anode of the first rectifying element is electrically coupled to the cathode of the fourth rectifying element to form the first node. The anode of the second rectifying element is electrically coupled to the cathode of the first rectifying element to form the third node. The anode of the third rectifying element is electrically coupled to the cathode of the second rectifying element to form the second node. The anode of the fourth rectifying element is electrically coupled to the cathode of the third rectifying element to form the fourth node. The first and second nodes are electrically coupled to the first and second ends of the conversion unit, respectively. The operation unit is electrically coupled to the third and fourth nodes of the bridge unit, amplifies two bridge voltages at the third and fourth nodes in a differential manner and outputs an operation voltage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0011]      FIG. 1  shows a normal operation diagram of an electric power system equipped with a current direction detection module of the invention. 
           [0012]      FIG. 2  shows an abnormal operation diagram of the electric power system equipped with the current direction detection module of the invention. 
           [0013]      FIG. 3  shows a circuit diagram of the current direction detection module according to a first embodiment of the invention. 
           [0014]      FIG. 4  shows a circuit diagram of the current direction detection module according to a second embodiment of the invention. 
           [0015]      FIG. 5  shows a circuit diagram of the current direction detection module according to a third embodiment of the invention. 
           [0016]      FIG. 6  shows a circuit diagram of the current direction detection module according to a fourth embodiment of the invention. 
           [0017]      FIGS. 7   a  and  7   b  show voltage signals converted from a current signal using a current clamp at a secondary side of a conversion unit in the fourth embodiment of the invention. 
           [0018]      FIGS. 8   a  to  8   f  show waveforms measured at various measurement ends of the current direction detection module when a to-be-detected current flows in a first direction. 
           [0019]      FIGS. 9   a  to  9   f  show waveforms measured at the various measurement ends of the current direction detection module when the to-be-detected current flows in a second direction opposite to the first direction. 
       
    
    
       [0020]    In the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the term “first”, “second”, “third”, “fourth”, “inner”, “outer” “top”, “bottom” and similar terms are used hereinafter, it should be understood that these terms refer only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring to  FIGS. 1 and 2 , an operation diagram of an electric power system using a current direction detection module of the invention is shown according to a preferred embodiment of the invention. In  FIG. 1 , an electrical substation, a power station, a client and one or more distributed power sources are interconnected together via a plurality of power lines PL. The power lines PL carry currents passing in a first direction D 1  and a second direction D 2  opposite to the first direction D 1 . The power lines PL are equipped with one or more inspection modules (namely, M 1 , M 2  and M 3 ) for detecting the current direction of the electric power system when the electric power system is broken. Here, the current of the electric power system to be detected when the electric power system is broken is defined as a faulty current, which is used hereinafter for the entire specification. When the electric power system operates normally, a normal current Ia outputted by the power station flows to the client via the power lines PL. The distributed power sources also send normal currents Ib and Ic to the client via the power lines PL. The inspection modules M 1  and M 2  detect the currents of the electric power system flowing in the first direction D 1 , whereas the inspection module M 3  detects the currents of the electric power system flowing in the second direction D 2 . 
         [0022]    As shown in  FIG. 2 , faulty currents are shown to occur in the electric power system. When the electric power system is broken (for example, one power line PL is short to ground), a faulty current Ia′ of the power station will be directed to the ground via a short circuit path S, and faulty currents Ib′ and Ic′ of the distributed power sources will also be directed to the ground via the short circuit path S. At this moment, the short circuit path S will have a short circuit current. Based on this, the inspection module M 1  can detect that the faulty current Ia′ flows in the first direction D 1 , and the inspection modules M 2  and M 3  can detect that the faulty currents Ib′ and Ic′ flow in the second direction D 2 . Therefore, based on the directions of the faulty currents detected by the inspection modules, the location of the short circuit can be determined. 
         [0023]    Referring to  FIG. 3 , a circuit diagram of a current direction detection module is disclosed according to a first embodiment of the invention. The current direction detection module includes a conversion unit  1 , a bridge unit  2  and an operation unit  3 . The conversion unit  1  is electrically connected to the bridge unit  2  which, in turn, is electrically connected to the operation unit  3 . The conversion unit  1  detects a to-be-detected current I 1  (not shown) and outputs a converted current I 2  (not shown). The bridge unit  2  receives the converted current I 2  and outputs two bridge voltages V 11  and V 12  (not shown). The operation unit  3  receives the bridge voltages V 11  and V 12  and outputs an operation voltage V 2 . Based on this, the directions of faulty currents of the electric power system can be detected. In this embodiment, the to-be-detected current I 1  is the current carried by the power lines PL. 
         [0024]    The conversion unit  1  may be implemented by a current transformer, or by a device that converts an input current into an output current by a conversion ratio. The range of the conversion ratio may be determined in a way that a maximal value of the output current of the device does not exceed a maximal rated current of the bridge unit  2 . Take the power distribution networks of the electric power system as an example: assuming that the standard value of a faulty current is 1000 A (Ampere) and the maximal rated current of the bridge unit  2  is 1 A, then a current transformer with a conversion ratio of 2000:1 can be used to obtain an output current of 0.5 A. The conversion unit  1  includes a primary side  11  and a secondary side  12 . The primary side  11  can receive the to-be-detected current I 1  via the power lines PL and output the converted current I 2  at the secondary side  12 . The secondary side  12  has a first end  121  and a second end  122 . Both the first end  121  and second end  122  are electrically connected to the bridge unit  2 . In the embodiment, the conversion unit  1  is a current transformer with a conversion ratio of 2000:1. Based on this, the current transformer  1  is in a tube-like form having a K-end opening  111  and an L-end opening  112  at the primary side  11  thereof. In addition, the current transformer  1  has a K contact and an L contact, with the K contact serving as the first end  121  and the L contact serving as the second end  122 . In the embodiment, when detecting the current direction of the power lines PL, the power lines PL must be extended through the primary side  11  of the current transformer  1 . Based on this, the direction of currents of the power lines PL flowing from the K-end opening  111  to the L-end opening  112  is defined as the first direction D 1 , whereas the direction of currents of the power lines PL flowing from the L-end opening  112  to the K-end opening  111  is defined as the second direction D 2 . 
         [0025]    The bridge unit  2  includes a first rectifying element  21 , a second rectifying element  22 , a third rectifying element  23 , a fourth rectifying element  24 , a first node  25 , a second node  26 , a third node  27  and a fourth node  28 . The first rectifying element  21 , second rectifying element  22 , third rectifying element  23  and fourth rectifying element  24  may be solid state diodes, vacuum tube diodes or the like for rectification purposes. Each of the first rectifying element  21 , second rectifying element  22 , third rectifying element  23  and fourth rectifying element  24  has a cathode and an anode. The anode of the first rectifying element  21  is electrically connected to the cathode of the fourth rectifying element  24  to form the first node  25 . The anode of the second rectifying element  22  is electrically connected to the cathode of the first rectifying element  21  to form the third node  27 . The anode of the third rectifying element  23  is electrically connected to the cathode of the second rectifying element  22  to form the second node  26 . The anode of the fourth rectifying element  24  is electrically connected to the cathode of the third rectifying element  23  to form the fourth node  28 . The first node  25  and second node  26  are respectively electrically connected to the first end  121  and second end  122  of the conversion unit  1  for receiving the conversed current I 2 . The first rectifying element  21  and second rectifying element  22  cut off the negative cycle of the converted current I 2 , whereas the third rectifying element  23  and fourth rectifying element  24  cut off the positive cycle of the converted current I 2 . The third node  27  and fourth node  28  are electrically connected to the operation unit  3  for respectively outputting the two bridge voltages V 11  and V 12  thereto. In this embodiment, the first rectifying element  21 , second rectifying element  22 , third rectifying element  23  and fourth rectifying element  24  are implemented as solid state diodes with a maximal rated current of 1 A. 
         [0026]    The operation unit  3  includes a first amplifying element  31 , a first resistor  32 , a second resistor  33 , a third resistor  34 , a fourth resistor  35 , a fifth resistor  36 , a first capacitor  37  and a fifth node  38 . The first amplifying element  31  is an operational amplifier and includes a first inverting input end  311 , a first non-inverting input end  312 , a first output end  313 , a first positive power supply end  314  and a first negative power supply end  315 . The first inverting input end  311  is electrically connected to the first resistor  32  and second resistor  33 . The first non-inverting input end  312  is electrically connected to the third resistor  34  and fourth resistor  35 . The first output end  313  is electrically connected to the second resistor  33  and the fifth resistor  36 . The first positive power supply end  314  is electrically connected to a positive power supply Vp, whereas the first negative power supply end  315  is connected to the ground. The first resistor  32  has one end electrically connected to the first inverting input end  311  of the first amplifying element  31  and the other end electrically connected to the third node  27  of the bridge unit  2  for receiving the bridge voltage V 11 . The second resistor  33  has two ends electrically connected to the first inverting input end  311  and the first output end  313 , respectively, allowing the first amplifying element  31  to form a negative feedback amplifying circuit. The third resistor  34  has one end electrically connected to the first non-inverting input end  312  of the first amplifying element  31  and the other end electrically connected to the fourth node  28  of the bridge unit  2  for receiving the bridge voltage V 12 . The fourth resistor  35  has two ends electrically connected to the first non-inverting input end  312  and the ground, respectively. The first resistor  32 , second resistor  33 , third resistor  34  and fourth resistor  35  determine the gain Av  1  of the first amplifying element  31 . The fifth resistor  36  has one end electrically connected to the first output end  313  and the other end electrically connected to the first capacitor  37 . The first capacitor  37  may be a polar or non-polar capacitor and includes a first end  371  and a second end  372 . The first end  371  of the first capacitor  37  is electrically connected to the fifth resistor  36  to form the fifth node  38 , whereas the second end  372  of the first capacitor  37  is connected to the ground. The first capacitor  37  and the fifth resistor  36  form a RC filtering circuit which filters high frequency noise of the first output end  313 . Based on this, the operation unit  3  amplifies the bridge voltages V 11  and V 12  in a differential manner and outputs the operation voltage V 2  at the fifth node  38  thereof. Meanwhile, in order to protect the current direction detection module from being damaged by the positive power supply Vp when the positive power supply Vp appears to be unstable, an additional capacitor may be connected between the first positive power supply end  314  and the ground to provide a bypass path. In this embodiment, the first amplifying element  31  is an operational amplifier having the gain Av 1  with a value of 300, the resistance of the first resistor  32  and the third resistor  34  is 1KΩ, the resistance of the second resistor  33  and the fourth resistor  35  is 300KΩ, the positive power supply Vp is 3.3V (Volt) and the first capacitor  37  is a polar capacitor with a capacitance of 10 μF (micro Farad), with the first end  371  being positive polarity and the second end  372  being negative polarity. 
         [0027]    The operation of the current direction detection module of the first embodiment is now elaborated in detail. Assume that the to-be-detected current I 1  flows in the first direction D 1 , and the conversion unit  1  receives the to-be-detected current I 1  at the primary side  11  and outputs the converted current I 2  at the secondary side  12 . In this case, the converted current I 2  is a sinusoidal signal with noise. Therefore, the first rectifying element  21  and the second rectifying element  22  will allow the positive cycle of the converted current I 2  to pass and cut off the negative cycle of the converted current I 2 . Thus, the third node  27  of the bridge unit  2  will have the bridge voltage V 11  without negative cycle, which is then delivered to the first inverting input end  311  of the first amplifying element  31  after being attenuated by the first resistor  32 . On the other hand, the third rectifying element  23  and the fourth rectifying element  24  will allow the negative cycle of the converted current I 2  to pass and cut off the positive cycle of the converted current I 2 . Thus, the fourth node  28  of the bridge unit  2  will have the bridge voltage V 12  without positive cycle, which is then delivered to the first non-inverting input end  312  of the first amplifying element  31  after being attenuated by the third resistor  34 . The first resistor  32  sends the signal at the first output end  313  of the first amplifying element  31  back to the first inverting input end  311  in a negative feedback manner. The first output end  313  has a low-level signal with noise, which is then filtered by the RC filtering circuit consisting of the fifth resistor  36  and first capacitor  37 . The voltage at the fifth node  38  is retrieved as the operation voltage V 2  which is in a low level. The related experimental data is shown in Table 1 below: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 The 
                 The 
                 The 
               
               
                   
                 Sequence 
                   
                 to-be-detected 
                 converted 
                 operation 
               
               
                   
                 number 
                   
                 current I1 
                 current I2 
                 voltage V2 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 84 
                 mV 
               
               
                   
                 2 
                 536 
                 A 
                 268 
                 mA 
                 68 
                 mV 
               
               
                   
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 125 
                 mV 
               
               
                   
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 216 
                 mV 
               
               
                   
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 481 
                 mV 
               
               
                   
                   
               
             
          
         
       
     
         [0028]    On the contrary, if the to-be-detected current I 1  flows in the second direction D 2 , the third node  27  of the bridge unit  2  will have the bridge voltage V 11  without positive cycle, as the first rectifying element  21  and the second rectifying element  22  allow the negative cycle of the converted current I 2  to pass and cut off the positive cycle of the converted current I 2 . The bridge voltage V 11  without positive cycle at the third node  27  of the bridge unit  2  will then be delivered to the first inverting input end  311  of the first amplifying element  31 . On the other hand, the fourth node  28  of the bridge unit  2  will have the bridge voltage V 12  without negative cycle, as the third rectifying element  23  and the fourth rectifying element  24  allow the positive cycle of the converted current I 2  to pass and cut off the negative cycle of the converted current I 2 . The bridge voltage V 12  without negative cycle at the fourth node  28  of the bridge unit  2  will then be delivered to the first non-inverting input end  312  of the first amplifying element  31 . The first output end  313  has a high-level signal with noise, which is then filtered by the RC filtering circuit constituted by the fifth resistor  36  and first capacitor  37 . The operation voltage V 2  is in a high level. The related experimental data is shown in Table 2 below: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 The 
                 The 
                 The 
               
               
                   
                 Sequence 
                   
                 to-be-detected 
                 converted 
                 operation 
               
               
                   
                 number 
                   
                 current I1 
                 current I2 
                 voltage V2 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 309 mV 
               
               
                   
                 2 
                 536 
                 A 
                 268 
                 mA 
                 435 mV 
               
               
                   
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 420 mV 
               
               
                   
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 586 mV 
               
               
                   
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 827 mV 
               
               
                   
                   
               
             
          
         
       
     
         [0029]    Based on this, by retrieving the operation voltage V 2  and setting a high-level threshold Vth and a low-level threshold Vt 1 , the operation voltage V 2  is set to high level when the operation voltage V 2  is higher than the high-level threshold Vth. As such, it may be determined that the to-be-detected current I 1  flows in the second direction D 2 . On the other hand, the operation voltage V 2  is set to low level when the operation voltage V 2  is lower than the low-level threshold Vt 1 . As such, the to-be-detected current I 1  may be determined to flow in the first direction D 1 . In addition, the operation voltage V 2  may be magnified to enlarge the difference between the low and high levels for reducing determination error rate and required numerical accuracy of the high-level threshold Vth and low-level threshold Vt 1 . 
         [0030]    Referring to  FIG. 4 , a circuit diagram of a current direction detection module is disclosed according to a second embodiment of the invention. In comparison with the first embodiment, the current direction detection module in this embodiment includes a magnifying unit  4  electrically connected to the operation unit  3 . The magnifying unit  4  magnifies the operation voltage V 2  and outputs a magnifying voltage V 3 . The magnifying unit  4  includes a second amplifying element  41 , a sixth resistor  42 , a seventh resistor  43 , a eighth resistor  44 , a ninth resistor  45 , a tenth resistor  46  and a sixth node  47 . The second amplifying element  41  includes a second inverting input end  411 , a second non-inverting input end  412 , a second output end  413 , a second positive power supply end  414  and a second negative power supply end  415 . The second inverting input end  411  is electrically connected to the eighth resistor  44  and the ninth resistor  45 . The second non-inverting input end  412  is electrically connected to the sixth resistor  42  and seventh resistor  43 . The second output end  413  is electrically connected to the eighth resistor  44  to form the sixth node  47 . The second positive power supply end  414  is electrically connected to the positive power supply Vp. The second negative power supply end  415  is connected to the ground. The sixth resistor  42  has one end electrically connected to the second non-inverting input end  412  of the second amplifying element  41  and the other end electrically connected to the fifth node  38  of the operation unit  3 . The seventh resistor  43  has one end electrically connected to the second non-inverting input end  412  of the second amplifying element  41  and the other end electrically connected to the ground. The eighth resistor  44  has one end electrically connected to the second inverting input end  411  and the other end electrically connected to the second output end  413 , so that the second amplifying element  41  is allowed to form an amplifying circuit. The ninth resistor  45  has one end electrically connected to the second inverting input end  411  and the other end electrically connected to the tenth resistor  46 . The sixth resistor  42 , seventh resistor  43 , eighth resistor  44  and ninth resistor  45  determine the gain Av 2  of the second amplifying element  41 . The tenth resistor  46  has a first reference end  461  and two ends. The first reference end  461  is electrically connected to the ninth resistor  45  for adjusting the input voltage at the second inverting input end  411 . The two ends of the tenth resistor  46  are electrically connected to the positive power supply Vp and the ground. Meanwhile, in order to prevent the current direction detection module from being damaged by the positive power supply Vp when the positive power supply Vp appears to be unstable, an additional capacitor may be connected between the second positive power supply end  414  and the ground to provide a bypass path. In addition, another capacitor may be connected between the first reference end  461  and the ground to provide another bypass path. In the embodiment, the second amplifying element  41  is an operational amplifier, the resistance of the sixth resistor  42  and the ninth resistor  45  is 1KΩ, the resistance of the seventh resistor  43  and the eighth resistor  44  is 8.2KΩ, the tenth resistor  46  is a variable resistor with a resistance of 5KΩ, and the second amplifying element  41  has a gain Av 2  with a value of 8.2. 
         [0031]    The operation of the current direction detection module of the second embodiment is now elaborated in detail. The various parameters mentioned above are designated with specific values for experiment (with the to-be-detected current I 1  assumed to flow in the first direction D 1 ), as shown below: the first positive power supply end  314  and the second positive power supply end  414  are electrically connected to the positive power supply Vp of 3.3V, the first negative power supply end  315  and second negative power supply end  415  are connected to the ground, the gain value Av 1  of the first amplifying element  31  is 300, the gain value Av 2  of the second amplifying element  41  is 8.2, and the first reference end  461  of the tenth resistor  46  outputs a first reference voltage Vref 1  which is set as 191 mV. Referring to  FIG. 4 , the operation voltage V 2  at the fifth node  38  is delivered to the magnifying unit  4 . Assuming that the voltage at the sixth node  47  is retrieved as the magnifying voltage V 3 , the magnifying voltage V 3  will have the following relation with the operation voltage V 2 , as indicated in formula (I) below: 
         [0000]        V 3=( V 2 −V ref1)* Av 2  (1)
 
         [0032]    In the embodiment, since the second positive power supply end  414  and the second negative power supply end  415  of the second amplifying element  41  are respectively electrically connected to the positive power supply Vp and the ground, the resulted value of the V 2  minus the Vref 1  will be negative. The negative resulted value will not be amplified at the sixth node  47  of the second amplifying element  41  (i.e. the magnifying voltage V 3  is almost 0V at the sixth node  47 ) since the second amplifying element  41  is not connected to any negative power supply. Therefore, based on the assumption that the operation voltage V 2  flows in the first direction D 1 , the operation voltage V 2  will be smaller than the first reference voltage Vref 1 . As such, the magnifying voltage V 3 , which is almost 0 V, will be closer to 0 V than the operation voltage V 2  is. The experimental data regarding the magnifying voltage V 3  and the operation voltage V 2  is shown in Table 3 below: 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 The 
                 The 
                 The 
                 The 
               
               
                 Sequence 
                 to-be-detected 
                 converted 
                 operation 
                 magnifying 
               
               
                 number 
                 current I1 
                 current I2 
                 voltage V2 
                 voltage V3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 84 
                 mV 
                 51 
                 mV 
               
               
                 2 
                 536 
                 A 
                 268 
                 mA 
                 68 
                 mV 
                 58 
                 mV 
               
               
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 125 
                 mV 
                 77 
                 mV 
               
               
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 216 
                 mV 
                 204 
                 mV 
               
               
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 481 
                 mV 
                 1.91 
                 V 
               
               
                   
               
             
          
         
       
     
         [0033]    On the contrary, if the to-be-detected current I 1  flows in the second direction D 2 , the voltage at the fifth node  38  is in high level. As a result, the magnifying voltage V 3  will be closer to the positive power supply Vp than the operation voltage V 2  is. The experimental data regarding the magnifying voltage V 3  and the operation voltage V 2  is shown in Table 4 below: 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                 The 
                 The 
                 The 
                 The 
               
               
                 Sequence 
                 to-be-detected 
                 converted 
                 operation 
                 magnifying 
               
               
                 number 
                 current I1 
                 current I2 
                 voltage V2 
                 voltage V3 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 309 mV 
                 850 
                 mV 
               
               
                 2 
                 536 
                 A 
                 268 
                 mA 
                 435 mV 
                 1.78 
                 V 
               
               
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 420 mV 
                 1.85 
                 V 
               
               
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 586 mV 
                 2.12 
                 V 
               
               
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 827 mV 
                 2.17 
                 V 
               
               
                   
               
             
          
         
       
     
         [0034]    Based on this, by retrieving the magnifying voltage V 3  and setting the high-level threshold Vth and low-level threshold Vt 1 , it can be determined that the magnifying voltage V 3  is in the high or low level. The magnifying voltage V 3  is set to high level when the magnifying voltage V 3  is higher than the high-level threshold Vth. At this point, the to-be-detected current I 1  may be determined to flow in the second direction D 2 . On the contrary, the magnifying voltage V 3  is set to low level when the magnifying voltage V 3  is lower than the low-level threshold Vt 1 . At this point, the to-be-detected current I 1  may be determined to flow in the first direction D 1 . Moreover, the magnifying voltage V 3  may be input to a waveform shaping circuit so that the high-level threshold Vth and low-level threshold Vt 1  of the magnifying voltage V 3  may be replaced by and fixed at another two DC voltage levels. In this manner, the output signal of the current direction detection module of the invention may be in the form of a logic signal reflecting the directions of faulty currents of the electric power system. 
         [0035]    Referring to  FIG. 5 , a circuit diagram of the current direction detection module is disclosed according to a third embodiment of the invention. In comparison with the second embodiment, the current direction detection module in this embodiment further includes a shaping unit  5  electrically connected to the magnifying unit  4  for shaping the magnifying voltage V 3  into a shaping voltage V 4 . The shaping voltage V 4  is a logic signal. In the embodiment, the shaping unit  5  is a Schmitt trigger, which includes a third amplifying element  51 , an eleventh resistor  52 , a twelfth resistor  53 , a thirteenth resistor  54  and a fourteenth resistor  55 . The third amplifying element  51  includes a third inverting input end  511 , a third non-inverting input end  512 , a third output end  513 , a third positive power supply end  514  and a third negative power supply end  515 . The third inverting input end  511  is electrically connected to the thirteenth resistor  54 . The third non-inverting input end  512  is electrically connected to the eleventh resistor  52  and twelfth resistor  53 . The third output end  513  is electrically connected to the twelfth resistor  53  and fourteenth resistor  55 . The third positive power supply end  514  is electrically connected to the positive power supply Vp and the third negative power supply end  515  is connected to the ground. The eleventh resistor  52  has one end electrically connected to the third non-inverting input end  512  and the other end electrically connected to the sixth node  47  of the magnifying unit  4 . The twelfth resistor  53  has one end electrically connected to the third non-inverting input end  512  and the other end electrically connected to the third output end  513 . The thirteenth resistor  54  has a second reference end  541  and two ends. The second reference end  541  is electrically connected to the third inverting input end  511 . The two ends of the thirteenth resistor  54  are electrically connected to the positive power supply Vp and the ground. The fourteenth resistor  55  has one end electrically connected to the positive power supply Vp and the other end electrically connected to the third output end  513 . Meanwhile, in order to prevent the current direction detection module from being damaged by the positive power supply Vp when the positive power supply Vp appears to be unstable, an additional capacitor may be connected between the third positive power supply end  514  and the ground to provide a bypass path. In addition, another capacitor may be connected between the second reference end  541  and the ground to provide another bypass path. In the embodiment, the third amplifying element  51  is an operational amplifier, the resistance of the eleventh resistor  52  is 75.2KΩ, the resistance of the twelfth resistor  53  is 825KΩ, the thirteenth resistor  54  is a variable resistor with a resistance of 5KΩ, and the resistance of the fourteenth resistor  55  is 1KΩ. 
         [0036]    The operation of the current direction detection module of the third embodiment is now elaborated in detail. Based on the parameters given in previous embodiments that the gain value Av 1  of the first amplifying element  31  is 300, the gain value Av 2  of the second amplifying element  41  is 8.2, the first reference voltage Vref 1  is 191 mV, and the shaping unit  5  is a Schmitt trigger, the shaping voltage V 4  at the third output end  513  will be in a high level of the logic signal when the magnifying voltage V 3  is higher than the high-level threshold Vth. On the contrary, the shaping voltage V 4  will be in a low level of the logic signal when the magnifying voltage V 3  is lower than the low-level threshold Vt 1 . Meanwhile, the second reference end  541  of the thirteenth resistor  54  outputs a second reference voltage Vref 2  to the third inverting input end  511  of the third amplifying element  51 . The second reference voltage Vref 2  can adjust the high-level threshold Vth. The shaping voltage V 4  turns into the high level from the low level of the logic signal when the magnifying voltage V 3  is higher than the high-level threshold Vth, whereas the shaping voltage V 4  turns into the low level from the high level of the logic signal when the magnifying voltage V 3  is lower than the low-level threshold Vt 1 . In the embodiment, the high-level threshold Vth is 0.8V, the low-level threshold Vt 1  is 0.45V, the high level of the logic signal is 3.3 V and the low level of the logic signal is 0.8 V. Experimental data regarding the to-be-detected current I 1  flowing in the first direction D 1  is shown in Table 5 below: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                   
                 The 
                 The 
                 The 
                 The 
                 The 
               
               
                 Se- 
                 to-be- 
                 converted 
                 operation 
                 magnifying 
                 shaping 
               
               
                 quence 
                 detected 
                 current 
                 volt- 
                 volt- 
                 volt- 
               
               
                 number 
                 current I1 
                 I2 
                 age V2 
                 age V3 
                 age V4 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 84 
                 mV 
                 51 
                 mV 
                 0.8 V 
               
               
                 2 
                 536 
                 A 
                 268 
                 mA 
                 68 
                 mV 
                 58 
                 mV 
                 0.8 V 
               
               
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 125 
                 mV 
                 77 
                 mV 
                 0.8 V 
               
               
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 216 
                 mV 
                 204 
                 mV 
                 0.8 V 
               
               
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 481 
                 mV 
                 1.91 
                 V 
                 3.3 V 
               
               
                   
               
             
          
         
       
     
         [0037]    In the Table 5 above, it can be known from the data  1  to  4  that the shaping voltage V 4  is always 0.8 V when the to-be-detected current I 1  flows in the first direction D 1 . Furthermore, from the data  5  in the Table 5 above, the shaping voltage V 4  is 3.3 V when the to-be-detected current I 1  is over the range that can be measured. To limit the to-be-detected current I 1  in a proper range, the first reference voltage Vref 1  must be adjusted. For example, the first reference voltage Vref 1  is set as 400 mV and the gain value Av 2  of the second amplifying element  41  is set as 40. In this case, the shaping voltage V 4  will become 0.8 V after adjustment. 
         [0038]    On the contrary, experimental data regarding the to-be-detected current I 1  flowing in the second direction D 2  is shown in Table 6 below: 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                   
                 The 
                   
                   
                   
                   
               
               
                   
                 to-be- 
                 The 
                 The 
                 The 
                 The 
               
               
                 Se- 
                 detected 
                 converted 
                 operation 
                 magnifying 
                 shaping 
               
               
                 quence 
                 current 
                 current 
                 volt- 
                 volt- 
                 volt- 
               
               
                 number 
                 I1 
                 I2 
                 age V2 
                 age V3 
                 age V4 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 169 
                 A 
                 84.5 
                 mA 
                 309 mV 
                 850 
                 mV 
                 3.3 V 
               
               
                 2 
                 536 
                 A 
                 268 
                 mA 
                 435 mV 
                 1.78 
                 V 
                 3.3 V 
               
               
                 3 
                 1068 
                 A 
                 534 
                 mA 
                 420 mV 
                 1.85 
                 V 
                 3.3 V 
               
               
                 4 
                 1184 
                 A 
                 592 
                 mA 
                 586 mV 
                 2.12 
                 V 
                 3.3 V 
               
               
                 5 
                 1800 
                 A 
                 900 
                 mA 
                 827 mV 
                 2.17 
                 V 
                 3.3 V 
               
               
                   
               
             
          
         
       
     
         [0039]    Furthermore, the circuit of the current direction detection module of the third embodiment may be simplified by increasing the capacity of the first capacitor  37  of the operation unit  3  and replacing the shaping unit  5  with a comparator circuit electrically connected to the magnifying unit  4 . 
         [0040]    Referring to  FIG. 6 , a circuit diagram of the current direction detection module is disclosed according to a fourth embodiment of the invention. In comparison with the third embodiment, the current direction detection module in the embodiment further replaces the shaping unit  5  with a comparing unit  6  and changes the capacity of the first capacitor  37  of the operation unit  3  into 100 μF, with the comparing unit  6  electrically connected to the magnifying unit  4 . Based on this, the comparing unit  6  receives the magnifying voltage V 3  and outputs a comparing voltage V 5 , which is a logic signal. The comparing unit  6  includes a fourth amplifying element  61  and a fifteenth resistor  62 . The fourth amplifying element  61  includes a fourth inverting input end  611 , a fourth non-inverting input end  612 , a fourth output end  613 , a fourth positive power supply end  614  and a fourth negative power supply end  615 . The fourth inverting input end  611  is electrically connected to the fifteenth resistor  62 . The fourth non-inverting input end  612  is electrically connected to the sixth node  47  of the magnifying unit  4 . The fourth positive power supply end  614  is electrically connected to the positive power supply Vp and the fourth negative power supply end  615  is connected to the ground. The fifteenth resistor  62  includes a third reference end  621  and two ends. The third reference end  621  is electrically connected to the fourth inverting input end  611 . The two ends of the fifteenth resistor  62  are electrically connected to the positive power supply Vp and the ground. Meanwhile, in order to prevent the current direction detection module from being damaged by the positive power supply Vp when the positive power supply Vp appears to be unstable, an additional capacitor may be connected between the fourth positive power supply end  614  and the ground to provide a bypass path. In addition, another capacitor may be connected between the third reference end  621  and the ground to provide another bypass path. In the embodiment, the fourth amplifying element  61  is an operational amplifier and the fifteenth resistor  62  is a variable resistor with a resistance of 5KΩ. 
         [0041]    The operation of the current direction detection module of the fourth embodiment is now elaborated in detail. Based on the given parameters that the gain value Av 1  of the first amplifying element  31  is 300, the gain value Av 2  of the second amplifying element  41  is 8.2, the first reference voltage Vref 1  is 0 mV and the second reference voltage Vref 2  is 48 mV, and assuming that the voltage at the fourth output end  613  is retrieved as the comparing voltage V 5 , experimental data regarding the to-be-detected current I 1  flowing in the first direction D 1  can be seen in Table 7 below: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                   
                 The 
                 The 
                 The 
                 The 
               
               
                 Sequence 
                 converted 
                 operation 
                 magnifying 
                 comparing 
               
               
                 number 
                 current I2 
                 voltage V2 
                 voltage V3 
                 voltage V5 
               
               
                   
               
             
             
               
                 1 
                  58 mA 
                 5.83 mV 
                 7.64 mV 
                 0.02 V 
               
               
                 2 
                 307 mA 
                 6.99 mV 
                 7.03 mV 
                 0.02 V 
               
               
                 3 
                 576 mA 
                  6.6 mV 
                 7.82 mV 
                 0.02 V 
               
               
                   
               
             
          
         
       
     
         [0042]    On the contrary, experimental data regarding the to-be-detected current I 1  flowing in the second direction D 2  is shown in Table 8 below: 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
               
                   
                 The 
                 The 
                 The 
                 The 
               
               
                 Sequence 
                 converted 
                 operation 
                 magnifying 
                 comparing 
               
               
                 number 
                 current I2 
                 voltage V2 
                 voltage V3 
                 voltage V5 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                  58 mA 
                 53.5 
                 mV 
                 399 mV 
                 2.13 V 
               
               
                 2 
                 307 mA 
                 50.9 
                 mV 
                 380 mV 
                 2.09 V 
               
               
                 3 
                 576 mA 
                 55 
                 mV 
                 363 mV 
                 2.15 V 
               
               
                   
               
             
          
         
       
     
         [0043]      FIG. 7   a  shows a voltage signal converted from a current signal using a current clamp at the secondary side  12  of the conversion unit  1  when the first end  121  and the second end  122  are electrically connected to each other but not connected to the bridge unit  2 .  FIG. 7   b  shows a voltage signal converted from the current signal using the current clamp at the secondary side  12  of the conversion unit  1  when the first end  121  and the second end  122  are electrically connected to the bridge unit  2 .  FIGS. 8   a  to  8   f  show waveforms measured at various measurement ends of the current direction detection module when the to-be-detected current I 1  flows in the first direction D 1 . Specifically,  FIG. 8   a  shows a voltage signal of the first inverting input end  311  of the first amplifying element  31 .  FIG. 8   b  shows a voltage signal of the first non-inverting input end  312  of the first amplifying element  31 .  FIG. 8   c  shows a voltage signal of the first output end  313  of the first amplifying element  31 , with noise included in the voltage signal.  FIG. 8   d  shows a voltage signal of the fifth node  38  of the operation unit  3  (namely, the operation voltage V 2 ), with the noise filtered off.  FIG. 8   e  shows a voltage signal of the sixth node  47  of the operation unit  3  (namely, the amplified signal of the voltage signal shown in  FIG. 8   d ).  FIG. 8   f  shows a voltage signal of the fourth output end  613  of the fourth amplifying element  61  (namely, a logic signal having a stable DC value converted from the magnifying voltage V 3 ). 
         [0044]      FIGS. 9   a  to  9   f  show waveforms measured at various measurement ends of the current direction detection module when the to-be-detected current I 1  flows in the second direction D 2 . Specifically,  FIG. 9   a  shows a voltage signal of the first inverting input end  311  of the first amplifying element  31 .  FIG. 9   b  shows a voltage signal of the first non-inverting input end  312  of the first amplifying element  31 .  FIG. 9   c  shows a voltage signal of the first output end  313  of the first amplifying element  31 .  FIG. 9   d  shows a voltage signal of the fifth node  38  of the operation unit  3  (namely, the operation voltage V 2 ).  FIG. 9   e  shows a voltage signal of the sixth node  47  of the operation unit  3  (namely, the magnifying voltage V 3 ).  FIG. 9   f  shows a voltage signal of the fourth output end  613  of the fourth amplifying element  61  (namely, the waveform of the comparing voltage V 5 ). 
         [0045]    The current direction detection module of the invention uses the conversion unit  1  to convert the to-be-detected current I 1  into the converted current I 2 , which is then converted into the operation voltage V 2  with different voltage levels by the bridge unit  2  and the operation unit  3 . Based on this, the direction of the to-be-detected current I 1  may be recognized by determining whether the operation voltage V 2  is smaller than the low-level threshold Vt 1  or higher than the high-level threshold Vth. Thus, when short circuit occurs in the electric power system, the current direction detection module of the invention may detect the directions of faulty currents caused by the short circuit in the electric power system, thereby quickly finding out the location of the short circuit by referring to the directions of the faulty currents. 
         [0046]    Furthermore, since it is only required to extend the power lines PL through the primary side  11  of the conversion unit  1  without having to use the potential transformer, the current direction detection module of the invention may achieve reduced costs and easy detection of directions of faulty currents in the electric power system. 
         [0047]    Although the invention has been described in detail with reference to its presently preferable embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.