Abstract:
The present invention relates to a pole transformer load monitoring system using a wireless Internet network. The load monitoring system is capable of measuring, in real time, a variety of load parameters (phase voltages, phase currents and temperatures) of a pole transformer placed on a distribution line. The results of the measurements are transferred to an operator in a branch operating station over the wireless Internet network so as to prevent losses resulting from overloaded and unbalanced states, thereby enhancing the quality of power supply and efficiently managing a distribution load.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pole transformer load monitoring system using a wireless Internet network, and more particularly to a pole transformer load monitoring system using a wireless Internet network, which is capable of measuring a variety of loads (phase voltages, phase currents and temperatures) of a pole transformer placed on a distribution line in real time and transferring the results of the measurements to an operator in a branch operating station over the wireless Internet network so as to prevent losses resulting from overloaded and unbalanced states, thereby enhancing the quality of power supply and efficiently managing a distribution load. 
     2. Description of the Related Art 
     An example of conventional pole transformer load monitoring systems is shown in Korean Utility Model Publication No. 20-0174398 (published on Dec. 28, 1999). 
     FIG. 1 is a block diagram showing the construction of a pole transformer load monitoring system disclosed in the &#39;398 publication. As shown in this drawing, the pole transformer load monitoring system comprises an effective value converter  110  for converting current detected by a current transformer CT into an effective voltage, a battery  120  for charging and discharging itself with the current detected by the current transformer CT, a calculator  130  for amplifying the effective voltage from the effective value converter  110  and adjusting the gain of the amplified voltage, an analog/digital (A/D) converter  140  for converting an analog voltage from the calculator  130  into a BCD-coded digital signal, a data setting unit  150  for presetting a threshold value of overload current of a pole transformer, and a central processing unit (CPU)  160  operated according to a given program. In a normal state, the CPU  160  BCD-codes a peak load current value and continuously displays the coded value on a peak load current value display unit  170 . The CPU  160  also continuously monitors whether a currently measured peak load current value of the pole transformer exceeds the overload current threshold value preset by the data setting unit  150 . At the time that the currently measured peak load current value exceeds the preset overload current threshold value, the CPU  160  outputs an alarm control signal to an alarm unit  180  and an alarm transmission control signal to an alarm transmitter  190 , respectively. The peak load current value display unit  170  acts to display the peak load current value coded by the CPU  160  on a liquid crystal display (LCD). When the currently measured peak load current value of the pole transformer exceeds the preset overload current threshold value, the alarm unit  180  flickers or lights up an alarm indication lamp and rings a buzzer, in response to the alarm control signal from the CPU  160 . At this time, the alarm transmitter  190  transmits an overload alarm signal to a ground portable receiver in response to the alarm transmission control signal from the CPU  160 . 
     However, the above-mentioned conventional pole transformer load monitoring system has a disadvantage in that it cannot monitor hystereses of loads, such as phase voltages and phase currents, in real time because it uses no wireless Internet network. This makes it impossible to efficiently manage the demand for electricity as well as to practically provide upgraded and advanced versions of electrical products. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of monitoring phase voltages, phase currents, an internal temperature of a system body and an external temperature of a pole transformer in real time. 
     It is another object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of providing current and voltage load factors by time zones. 
     It is a further object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of outputting an alarm to a personal computer (PC) of a manager and a central control station at the time that a pole transformer is overloaded. 
     It is a further object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of providing an indication of only an overloaded pole transformer. 
     It is another object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of, when a pole transformer is overloaded, readily providing transformer information (light-loaded transformer information, overloaded transformer information, daily information, monthly information, quarterly information and yearly information). 
     It is yet another object of the present invention to provide a pole transformer load monitoring system using a wireless Internet network, which is capable of tracking an accurate fault point on a distribution line to shorten a recovery time. 
     In accordance with the present invention, the above and other objects can be accomplished by the provision of a pole transformer load monitoring system using a wireless Internet network, comprising phase current detection means for detecting current of each phase flowing through a secondary coil of a pole transformer; phase voltage detection means for detecting a voltage of each phase induced in the secondary coil of the pole transformer; internal temperature detection means for detecting an internal temperature of a system body; external temperature detection means for detecting an external temperature of the pole transformer; an analog/digital converter for converting the phase current detected by the phase current detection means, the phase voltage detected by the phase voltage detection means, the internal temperature detected by the internal temperature detection means and the external temperature detected by the external temperature detection means into digital signals; a microprocessor for performing an arithmetic operation for digital phase current, phase voltage, internal temperature and external temperature data from the analog/digital converter and controlling the entire operation of the system; a flash read only memory for sequentially storing phase current, phase voltage, internal temperature and external temperature values measured as a result of the arithmetic operation of the microprocessor; a watchdog for monitoring from periodic output signals from the microprocessor whether the microprocessor operates normally and outputting a reset signal to the microprocessor and flash read only memory upon determining that the microprocessor does not operate normally; a buffer for buffering an address signal from the microprocessor; a random access memory for storing output data from the microprocessor in its location corresponding to the address signal buffered by the buffer; a modem for receiving an output signal from the microprocessor, transmitting the received signal to a central control station via a base station and Internet network, receiving a control signal transmitted from the central control station and transferring the received control signal to the microprocessor; indication means for providing a visual indication of the transmission of the output signal from the microprocessor via the modem and a visual indication of the reception of the control signal from the central control station by the microprocessor; and an alternating current (AC)/direct current (DC) converter for converting an AC voltage applied between any one of three phases of the pole transformer and a neutral line into a DC voltage of a certain level and outputting the converted DC voltage as an operating voltage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a block diagram schematically showing the construction of a conventional pole transformer load monitoring system; 
     FIG. 2 is a block diagram schematically showing the construction of a pole transformer load monitoring system using a wireless Internet network in accordance with a preferred embodiment of the present invention; 
     FIG. 3 is a detailed circuit diagram of a phase current detection unit in FIG. 2; 
     FIG. 4 is a detailed circuit diagram of a phase voltage detection unit in FIG. 2; and 
     FIG. 5 is a schematic view of an exemplary example to which the present invention is applied. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 is a block diagram schematically showing the construction of a pole transformer load monitoring system using a wireless Internet network in accordance with a preferred embodiment of the present invention, FIG. 3 is a detailed circuit diagram of a phase current detection unit in FIG. 2, FIG. 4 is a detailed circuit diagram of a phase voltage detection unit in FIG. 2, and FIG. 5 is a schematic view of an exemplary example to which the present invention is applied. 
     As shown in FIGS. 2 to  5 , the present pole transformer load monitoring system comprises a phase current detection unit  300  for detecting current of each phase flowing through a secondary coil of a pole transformer  1900  installed in a pole  2050 , a phase voltage detection unit  400  for detecting a voltage of each phase induced in the secondary coil of the pole transformer  1900 , an internal temperature detection unit  500  for detecting an internal temperature of a system body S, an external temperature detection unit  600  for detecting an external temperature of the pole transformer  1900 , and an A/D converter  700  for converting the phase current detected by the phase current detection unit  300 , the phase voltage detected by the phase voltage detection unit  400 , the internal temperature detected by the internal temperature detection unit  500  and the external temperature detected by the external temperature detection unit  600  into digital signals. The pole transformer load monitoring system further comprises a microprocessor  800  for performing an arithmetic operation for digital phase current, phase voltage, internal temperature and external temperature data from the A/D converter  700  and controlling the entire operation of the system, a flash read only memory (ROM)  900  for sequentially storing phase current, phase voltage, internal temperature and external temperature values measured as a result of the arithmetic operation of the microprocessor  800 , and a watchdog  1000  for monitoring from periodic output signals from the microprocessor  800  whether the microprocessor  800  operates normally and outputting a reset signal to the microprocessor  800  and flash ROM  900  upon determining that the microprocessor  800  does not operate normally. The pole transformer load monitoring system further comprises a buffer  1100  for buffering an address signal from the microprocessor  800 , a random access memory (RAM)  1200  for storing output data from the microprocessor  800  in its location corresponding to the address signal buffered by the buffer  1100 , a modem  1300  for receiving an output signal from the microprocessor  800 , transmitting the received signal to a central control station  2200  via a base station  2000  and Internet network  2100 , receiving a control signal transmitted from the central control station  2200  and transferring the received control signal to the microprocessor  800 , an indication unit  1400  for providing a visual indication of the transmission of the output signal from the microprocessor  800  via the modem  1300  and a visual indication of the reception of the control signal from the central control station  2200  by the microprocessor  800 , and an alternating current (AC)/direct current (DC) converter  1500  for converting an AC voltage applied between any one of three phases of the pole transformer  1900  and a neutral line into a DC voltage of a certain level and outputting the converted DC voltage as an operating voltage. 
     As employed herein “AΦ” should be construed as the designation for a first phase of a three phase electrical power transmission/distribution line, “BΦ” should be construed as the designation for the second phase and “CΦ” should be construed as the designation for the third phase. 
     The phase current detection unit  300  includes, as shown in FIG. 3, an AΦ current detector  310  for detecting AΦ current, a BΦ current detector  320  for detecting BΦ current, and a CΦ current detector  330  for detecting CΦ current. 
     The AΦ current detector  310  includes a first current transformer CT 1  for detecting the AΦ current, a first bridge rectification circuit  312  for rectifying the AΦ current detected by the first current transformer CT 1  by full wave to reduce an associated input width of the A/D converter  700  so as to provide a precise measurement of the detected AΦ current, an output resistor R 310  connected to the output of the first bridge rectification circuit  312  for outputting AΦ DC current full wave-rectified by the first bridge rectification circuit  312 , a Zener diode ZD 2  for bypassing abnormal overcurrent to ground when it flows through the output of the first bridge rectification circuit  312 , and a capacitor C 3  connected in parallel to the Zener diode ZD 2  for filtering a noise component (high frequency component) contained in the AΦ DC current full wave-rectified by the first bridge rectification circuit  312  and outputting the resulting AΦ DC current to the A/D converter  700 . The BΦ current detector  320  includes a second current transformer CT 2  for detecting the BΦ current, a second bridge rectification circuit  322  for rectifying the BΦ current detected by the second current transformer CT 2  by full wave to reduce an associated input width of the A/D converter  700  so as to provide a precise measurement of the detected BΦ current, an output resistor R 320  connected to the output of the second bridge rectification circuit  322  for outputting BΦ DC current full wave-rectified by the second bridge rectification circuit  322 , a Zener diode ZD 3  for bypassing abnormal overcurrent to ground when it flows through the output of the second bridge rectification circuit  322 , and a capacitor C 4  connected in parallel to the Zener diode ZD 3  for filtering a noise component (high frequency component) contained in the BΦ DC current full wave-rectified by the second bridge rectification circuit  322  and outputting the resulting BΦ DC current to the A/D converter  700 . The CΦ current detector  330  includes a third current transformer CT 3  for detecting the CΦ current, a third bridge rectification circuit  332  for rectifying the CΦ current detected by the third current transformer CT 3  by full wave to reduce an associated input width of the A/D converter  700  so as to provide a precise measurement of the detected CΦ current, an output resistor R 330  connected to the output of the third bridge rectification circuit  332  for outputting CΦ DC current full wave-rectified by the third bridge rectification circuit  332 , a Zener diode ZD 4  for bypassing abnormal overcurrent to ground when it flows through the output of the third bridge rectification circuit  332 , and a capacitor C 5  connected in parallel to the Zener diode ZD 4  for filtering a noise component (high frequency component) contained in the CΦ DC current full wave-rectified by the third bridge rectification circuit  332  and outputting the resulting CΦ DC current to the A/D converter  700 . 
     The phase voltage detection unit  400  includes, as shown in FIG. 4, an AΦ voltage detector  410  for detecting an AΦ voltage, a BΦ voltage detector  420  for detecting a BΦ voltage, and a CΦ voltage detector  430  for detecting a CΦ voltage. 
     The AΦ voltage detector  410  includes a first potential transformer PT 1  for detecting the AΦ D voltage, a fourth bridge rectification circuit  412  for rectifying the AΦ voltage detected by the first potential transformer PT 1  by full wave, an output resistor R 410  connected to the output of the fourth bridge rectification circuit  412 , and a filter  414  for filtering a high frequency component contained in an output AΦ DC voltage from the output resistor R 410  and outputting the resulting AΦ DC voltage to the A/D converter  700 . The filter  414  is provided with a resistor R 414  and capacitor C 414 . The BΦ voltage detector  420  includes a second potential transformer PT 2  for detecting the BΦ voltage, a fifth bridge rectification circuit  422  for rectifying the BΦ voltage detected by the second potential transformer PT 2  by full wave, an output resistor R 420  connected to the output of the fifth bridge rectification circuit  422 , and a filter  424  for filtering a high frequency component contained in an output BΦ DC voltage from the output resistor R 420  and outputting the resulting BΦ DC voltage to the A/D converter  700 . The filter  424  is provided with a resistor R 424  and capacitor C 424 . The CΦ voltage detector  430  includes a third potential transformer PT 3  for detecting the CΦ voltage, a sixth bridge rectification circuit  432  for rectifying the CΦ voltage detected by the third potential transformer PT 3  by full wave, an output resistor R 430  connected to the output of the sixth bridge rectification circuit  432 , and a filter  434  for filtering a high frequency component contained in an output CΦ DC voltage from the output resistor R 430  and outputting the resulting CΦ DC voltage to the A/D converter  700 . The filter  434  is provided with a resistor R 434  and capacitor C 434 . 
     In accordance with the teaching of the present invention, sophisticated phase current detectors and phase voltage detectors (FIG.  3  and FIG. 4) may be used in conjunction with a single phase or multiphase AC power distribution. The detector outputs appear on lines  310 A,  320 B,  330 C,  410 A,  420 B and  430 C, respectively and are input to the A/D converter  700 . 
     The internal temperature detection unit  500  includes a pull-up resistor R 1  for inputting a power supply voltage Vcc, a temperature sensor  500   a  for sensing the internal temperature of the system body S, and a capacitor Cl for filtering a noise component contained in an output signal from the temperature sensor  500   a.    
     The external temperature detection unit  600  includes a temperature sensor  600   a  mounted on the outer surface of the pole transformer  1900  for sensing the external temperature of the transformer  1900 , a Zener diode ZD 1  for bypassing an abnormal overload voltage contained in an output signal from the temperature sensor  600   a  to ground, and a bypass capacitor C 2  for filtering a noise component contained in the output signal from the temperature sensor  600   a.    
     The indication unit  1400  includes a first light emitting diode LED 1  for indicating the transmission of the output signal from the microprocessor  800  to the central control station  2200  via a resistor R 5 , the modem  1300  and the Internet network  2100 , a voltage limiting resistor R 2  for limiting a voltage to the first light emitting diode LED 1 , a second light emitting diode LED 2  for indicating the reception of the control signal from the central control station  2200  by the microprocessor  800  via the Internet network  2100  and modem  1300 , and a voltage limiting resistor R 3  for limiting a voltage to the second light emitting diode LED 2 . 
     In FIG. 2, the reference numeral  1600 , not described, denotes a reference voltage generator that generates a reference voltage in response to the power supply voltage Vcc and applies the generated reference voltage to the A/D converter  700 , LED 3  denotes a light emitting diode that indicates the output of the DC voltage from the AC/DC converter  1500 , and R 4  denotes a voltage limiting resistor that limits a voltage to the light emitting diode LED 3 . 
     A description will hereinafter be given of the operation of the pole transformer load monitoring system with the above-stated construction in accordance with the preferred embodiment of the present invention. 
     First, in the phase current detection unit  300 , the AΦ current detector  310 , BΦ current detector  320  and CΦ current detector  330  detect AΦ current, BΦ current and CΦ current and output the detection results to the A/D converter  700 , respectively. 
     In detail, in the AΦ current detector  310 , the first current transformer CT 1  detects the AΦ current, which is then full wave-rectified by the first bridge rectification circuit  312  and applied to the output resistor R 310 . The capacitor C 3  filters a noise component (high frequency component) contained in output AΦ DC current from the output resistor R 310  and outputs the resulting AΦ DC current to the A/D converter  700 . At this time, if abnormal overcurrent flows through the output of the first bridge rectification circuit  312 , then it is bypassed to ground by the Zener diode ZD 2 . 
     In the BΦ current detector  320 , the BΦ current is detected by the second current transformer CT 2 , full wave-rectified by the second bridge rectification circuit  322  and then applied to the output resistor R 320 . The capacitor C 4  filters a noise component (high frequency component) contained in output BΦ DC current from the output resistor R 320  and outputs the resulting BΦ DC current to the A/D converter  700 . At this time, provided that abnormal overcurrent flows through the output of the second bridge rectification circuit  322 , it will be bypassed to ground by the Zener diode ZD 3 . In the CΦ current detector  330 , the CΦ current is detected by the third current transformer CT 3 , full wave-rectified by the third bridge rectification circuit  332  and then applied to the output resistor R 330 . The capacitor C 5  filters a noise component (high frequency component) contained in output CΦ DC current from the output resistor R 330  and outputs the resulting CΦ DC current to the A/D converter  700 . At this time, provided that abnormal overcurrent flows through the output of the third bridge rectification circuit  332 , it will be bypassed to ground by the Zener diode ZD 4 . 
     In the phase voltage detection unit  400 , the AΦ voltage detector  410 , BΦ voltage detector  420  and CΦ voltage detector  430  detect an AΦ voltage, BΦ voltage and CΦ voltage and output the detection results to the A/D converter  700 , respectively. 
     In other words, in the AΦ voltage detector  410 , the first potential transformer PT 1  detects the AΦ voltage, which is then full wave-rectified by the fourth bridge rectification circuit  412  and applied to the output resistor R 410 . The filter  414 , which includes the resistor R 414  and capacitor C 414 , filters a high frequency component contained in an output AΦ DC voltage from the output resistor R 410  and outputs the resulting AΦ DC voltage to the A/D converter  700 . In the BΦ voltage detector  420 , the BΦ voltage is detected by the second potential transformer PT 2 , full wave-rectified by the fifth bridge rectification circuit  422  and then applied to the output resistor R 420 . The filter  424 , which is composed of the resistor R 424  and capacitor C 424 , filters a high frequency component contained in an output BΦ DC voltage from the output resistor R 420  and outputs the resulting BΦ DC voltage to the A/D converter  700 . In the CΦ voltage detector  430 , the CΦ voltage is detected by the third potential transformer PT 3 , full wave-rectified by the sixth bridge rectification circuit  432  and then applied to the output resistor R 430 . The filter  434 , which is provided with the resistor R 434  and capacitor C 434 , filters a high frequency component contained in an output CΦ DC voltage from the output resistor R 430  and outputs the resulting CΦ DC voltage to the A/D converter  700 . 
     In the internal temperature detection unit  500 , the temperature sensor  500   a  senses the internal temperature of the system body S, and the capacitor C 1  filters a noise component contained in an output signal from the temperature sensor  500   a  and outputs the resulting signal to the A/D converter  700 . In the external temperature detection unit  600 , the temperature sensor  600   a  senses the external temperature of the pole transformer  1900 , and the Zener diode ZD 1  bypasses an, abnormal overload voltage contained in an output signal from the temperature sensor  600   a  to ground. The bypass capacitor C 2  filters a noise component contained in the output signal from the temperature sensor  600   a  and outputs the resulting signal to the A/D converter  700 . 
     The A/D converter  700  converts the AΦ current, BΦ current and CΦ current detected respectively by the AΦ current detector  310 , BΦ current detector  320  and CΦ current detector  330  in the phase current detection unit  300 , the AΦ voltage, BΦ voltage and CΦ voltage detected respectively by the AΦ voltage detector  410 , BΦ voltage detector  420  and CΦ voltage detector  430  in the phase voltage detection unit  400 , the internal temperature of the system body S detected by the internal temperature detection unit  500  and the external temperature of the pole transformer  1900  detected by the external temperature detection unit  600  into digital signals and then outputs the converted digital signals to the microprocessor  800 . 
     The microprocessor  800  performs an arithmetic operation for digital phase current, phase voltage, internal temperature and external temperature data from the A/D converter  700  and controls the entire operation of the system. 
     In other words, the flash ROM  900  sequentially stores phase current, phase voltage, internal temperature and external temperature values measured as a result of the arithmetic operation of the microprocessor  800 , in the order of their measurements (detections). 
     The watchdog  1000  receives output signals from the microprocessor  800  at intervals of a predetermined time and monitors from the received signals whether the microprocessor  800  operates normally. Upon determining that the microprocessor  800  does not operate normally, the watchdog  1000  outputs a reset signal to the microprocessor  800  and flash ROM  900  such that the microprocessor  800  is initialized to perform the normal operation. 
     The buffer  1100  buffers an address signal from the microprocessor  800  and outputs the buffered address signal to the RAM  1200 . The RAM  1200  stores output data from the microprocessor  800 , i.e., digital phase current, phase voltage, internal temperature and external temperature data in its location corresponding to the address signal buffered by the buffer  1100 . The microprocessor  800  also outputs the digital phase current, phase voltage, internal temperature and external temperature data to the modem  1300  via the resistor R 5 . If the modem  1300  receives the output data from the microprocessor  800 , then it transmits the received data to the central control station  2200  via the base station  2000  and Internet network  2100 . As a result, the central control station  2200  can monitor hystereses of loads, such as phase voltages and phase currents, on the basis of the transmitted data. The central control station  2200  can also graph load trend by time zones and print out a daily report, monthly report, quarterly report and yearly report about light-load information and overload information. The station  2200  can further generate an alarm and determine whether a pole transformer on any pole  2050  is overloaded. 
     Therefore, the central control station  2200  can output a control signal to an overloaded or faulty pole transformer  1900  to rapidly cope with the overloaded or faulty state, or give an alarm to a personal computer of a manager to cope with the overloaded or faulty state at once, thereby stably supplying power to consumers, estimating overload to avoid transformer explosion and sudden interruption of power supply, and tracking an accurate fault point on a distribution line to shorten a recovery time. 
     At this time, in the indication unit  1400 , the first light emitting diode LED 1  acts to indicate the transmission of the output data from the microprocessor  800  to the central control station  2200  via the resistor R 5 , the modem  1300  and the Internet network  2100 , and the second light emitting diode LED 2  acts to indicate the reception of the control signal from the central control station  2200  by the microprocessor  800  via the Internet network  2100  and modem  1300 . 
     As apparent from the above description, the present invention provides a pole transformer load monitoring system using a wireless Internet network, which comprises a phase current detection unit for detecting current of each phase flowing through a secondary coil of a pole transformer, a phase voltage detection unit for detecting a voltage of each phase induced in the secondary coil of the pole transformer, an internal temperature detection unit for detecting an internal temperature of a system body, an external temperature detection unit for detecting an external temperature of the pole transformer, and an A/D converter for converting the detected phase current, phase voltage, internal temperature and external temperature into digital signals and outputting the converted digital signals to a microprocessor. The microprocessor performs an arithmetic operation for digital phase current, phase voltage, internal temperature and external temperature data from the A/D converter and sequentially stores the resulting measurements in a flash ROM. A watchdog is provided to monitor from periodic output signals from the microprocessor whether the microprocessor operates normally and output a reset signal to the microprocessor and flash ROM upon determining that the microprocessor does not operate normally. A buffer is provided to buffer an address signal from the microprocessor, and a RAM is provided to store output data from the microprocessor in its location corresponding to the address signal buffered by the buffer. A modem is adapted to receive an output signal from the microprocessor, transmit the received signal to a central control station via an Internet network, receive a control signal transmitted from the central control station and transfer the received control signal to the microprocessor. The indication unit functions to provide a visual indication of the transmission of the output signal from the microprocessor via the modem and a visual indication of the reception of the control signal from the central control station by the microprocessor. Therefore, the pole transformer load monitoring system according to the present invention is capable of monitoring phase voltages, phase currents, an internal temperature of a system body and an external temperature of a pole transformer in real time and providing current and voltage load factors by time zones. The present system is further capable of, when a pole transformer is overloaded, outputting an alarm to a PC of a manager and a central control station and displaying an associated image on the screen. Moreover, the present system can provide an indication of only an overloaded pole transformer. Furthermore, the present system is capable of, when a pole transformer is overloaded, readily providing transformer information (for example, light-loaded transformer information, overloaded transformer information, daily information, monthly information, quarterly information and yearly information), and tracking an accurate fault point on a distribution line to shorten a recovery time. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.