A SYSTEM AND METHOD FOR DETECTING FAULTS IN CABLES AND ELECTRICAL JOINTS BY MEASURING IMPEDANCE
Field of the Invention
[001] The present invention relates to a system and a method for detecting faults in cable and electrical joints, more particularly the system and method uses an impedance detector for detecting faults by measuring impedance in cable and electrical joints in an electrical network.
Background of the Invention
[002] Electrical faults are physical events that show the occurrence by themselves occasionally and in unpredictable ways within electrical networks or systems. A major contributor to electrically caused fires is loose connections or deteriorated electrical contacts caused due to long run in the network. These loose contacts in turn increase the resistance of the joint and causes heat build-up on the connection. Cable loops with higher impedance can result high power losses. Early detection of these loose contacts is very essential to avoid occurrence of electrical faults.
[003] Existing technologies use radar methods to locate faults. The first method uses a transient waveform generated by the fault breakdown. In this case, the fault transient reflects back and forth between the fault and the end of the cable where the measurement is made. The round trip time delay is measured and interpreted as a distance to the fault. In the second case, a pulse signal is transmitted along the cable and is reflected from the fault. In this case, the pulse must be transmitted along the cable while the arc at the fault is ignited. The pulse is reflected from the arc and the round trip is interpreted as a distance to the fault.
[004] US6798211 discloses a power line fault detector and analyzer for locating faults in a power line by modeling pulses of reflected travelling wave signals which are generated from electrical arcs that occur as a result of the fault. The detector monitors the circuit using an antenna which receives radio-frequency signals emitted by line faults and records the signatures of these faults. A model of the fault signature is calculated using the recorded signature and the initial conditions of the cable system prior to the fault. The result is an approximate response characteristic of the faulted power line with arcs generated in the fault condition being modeled as an impulse. Parameters derived from this response characteristic direct to the precise fault location. However, this detector is imprecise and does not provide accurate results for detecting faults.
[005] US9215045 discloses detecting and locating of intermittent faults in electrical systems. Signals are transmitted from a transmitter that is positioned in an electrical network. The signals that have been transmitted are received by a single receiver positioned within the electrical network. At the single receiver, the received signals are analyzed with the transmitted signals and

a determination is made as to whether a fault has occurred in the electrical network and the approximate location of the fault. However, this system also provides approximate location for detecting faults.
[006] Therefore, there exists a need for an invention to overcome the drawbacks described herein such that invention should be capable of detecting faults in live cables and electrical joints. There also exists a need to provide an invention such that the system capable of measuring impedance in cable and electrical joints in an electrical network by using an impedance detector.
Objects of the Invention
[007] It is a primary object of the present invention to detect faults in cables and electrical joints in an electrical network.
[008] It is another object of the present invention to measure impedance in cables and electrical joints to detect faults.
[009] It is another object of the present invention to detect faults such as loose contacts, deteriorated contacts, rusted contacts after long run, open circuit, short circuit, power loss detection in an electrical network.
[010] It is another object of the present invention to reduce maintenance and effectively manage cables and electrical joints in an electrical network.
Summary of the Invention
[011] According to an aspect of the present invention, a system for detecting faults in cables and electrical joints of an electrical network by measuring impedance of cables and electrical joints, said system comprising of an impedance detector assisting in minimizing power loss in cable path and electrical joints. The impedance detector further comprising of a microcontroller for injecting a high frequency pulse sweep in a cable loop with a set frequency & amplitude at set injection point; a band pass filter for attenuating noise and signal outside the pass band; at least two relays for selecting the cable loop; plurality of capacitors C1, C2 and C3 for coupling high frequency voltage pulse on P, N and E lines and attenuates low frequency high line voltage from entering the impedance detector; plurality of schottky diodes for providing low impedance path for high frequency and drops low frequency leakage current; and Phase (P), Neutral (N) and Earth (E) cables of an electrical network connected between a distribution transformer and the impedance detector; wherein the system; measures and records base impedance characteristics of the cables and electrical joints during installation by means of the impedance detector, wherein the impedance detector measures the voltage drop across a known resistor R2 to calculate the cable loop impedance, and wherein the impedance detector compares the base impedance characteristics with the calculated cable loop impedance to detect open circuit, short circuit,

contact deterioration, rusting, mechanical wear and tear, cable cuts or other faults at pre-determined time intervals.
[012] It is another aspect of the present invention, wherein a first analog to digital convertor of the impedance detector converts voltage drop across the known resistor R2 to a digital value for analyzing.
[013] It is another aspect of the present invention, wherein the microcontroller comprising of an FFT window for detecting the amplitude of the measured signal; a high frequency programmable pulse generator to generate the pulse sweep at pre-determined time intervals; a transistor based amplifier for amplifying the generated pulse sweep; and a second analog to digital convertor to convert voltage drop across resistor R2 to a digital value for analyzing, wherein the microcontroller regularly injects the pulse sweep at pre-determined time intervals at the set injection point.
[014] It is another aspect of the present invention, wherein the set injection point is at a resistor R1.
[015] It is another aspect of the present invention, wherein the pulse generator generates the pulse sweep at a pre-determined step time with an increment of each step by a pre-determined frequency, where each step for generating the pulse sweep is provided with a set delay period.
[016] It is another aspect of the present invention, wherein the FFT window measures the voltage drop across the known resistor R2 at each pulse sweep to calculate the cable loop impedance till resonant frequency is attained.
[017] It is another aspect of the present invention, wherein the pulse sweep is injected between Phase Neutral (P to N), Earth Phase (E to P) and Earth Neutral (E to N) cable loops for fault detection in cables and electrical joints.
[018] It is another aspect of the present invention, wherein the system remotely customizes the pre-determined time intervals, pre-determined step time, set frequency, set delay period and controls the injection of high frequency pulse sweep.
[019] It is another aspect of the present invention, wherein the distribution transformer shorts the Neutral (N) and Earth (E) cables.
[020] It is another aspect of the present invention, wherein a high frequency current injection transformer is mounted on Phase (P) and Neutral (N) cables to calculate the secondary side loop impedance by measuring the primary side current of the coil.

[021] It is another aspect of the present invention, wherein the system also detects short circuits on the disconnected power lines by injecting high frequency pulse sweep and measure voltage drop across the known resistor R2 to calculate the cable loop impedance.
[022] It is another aspect of the present invention, wherein a power supply is provided for supplying power to the impedance detector and its components.
[023] According to a further aspect of the present invention, a method for calculating the cable
loop impedance by means of an impedance detector of an electrical network, comprising steps of
selecting a cable loop by arranging positions of at least two relays; injecting high frequency
pulse sweep on the cable loop with a set frequency and amplitude at a set injection point using a pulse generator; measuring and converting the voltage drop across a known resistor R2 to a digital value using a first analog to digital convertor; calculating cable loop impedance from the voltage drop of the measured signal at the set frequency using an FFT window; if the measured amplitude is equal to the applied amplitude, an open circuit notification is sent to user; if the measured amplitude is not greater than the threshold value and not less than the applied amplitude, an open circuit notification is sent to user; if the measured amplitude is greater than a threshold value and less than the applied amplitude, updating the measured amplitude and frequency table along with the calculated cable loop impedance at set frequency; finding the maximum amplitude and the corresponding frequency at this maximum amplitude which is resonant frequency; and calculating capacitive reactance at this resonant frequency, wherein the capacitive reactance is equal to inductive reactance at the resonant frequency and hence the cable loop impedance at this resonant frequency is equal to pure resistance.
[024] It is another aspect of the present invention, wherein the resistance is recorded as base impedance characteristic value for the selected cable loop set during the starting of the installation using the impedance detector.
[025] According yet another aspect of the present invention, a method for detecting faults in
cables and electrical joints of an electrical network by measuring impedance of cables and
electrical joints, said method comprising steps of calculating the cable loop impedance for a
selected cable loop of an electrical network.
[026] It is another aspect of the present invention, wherein comparing the calculated cable loop impedance with the recorded base impedance characteristic value; and informing the user for necessary corrective actions according to the increase of the calculated cable loop impedance value from the base impedance characteristic value.

[027] It is another aspect of the present invention, wherein the pulse sweep is generated at a pre-determined step time with an increment of each step by a pre-determined frequency, where each step for generating the pulse sweep is provided with a set delay period.
[028] It is another aspect of the present invention, wherein at each increment of the pre-determined frequency, the measured amplitude is recorded till the said pre-determined frequency reaches resonant frequency.
[029] It is another aspect of the present invention, wherein the cable loops include Phase Neutral (P to N), Earth Phase (E to P) and Earth Neutral (E to N) cable loops for fault detection in cables and electrical joints.
[030] According to a further aspect of the present invention, a method for calculating the primary current of a high frequency current injection transformer by means of an impedance detector of an electrical network, comprising steps of: selecting a cable loop by arranging positions of at least two relays; injecting high frequency pulse sweep on the cable loop with a set frequency and amplitude at a set injection point using a pulse generator; measuring and converting the voltage drop across a known resistor R2 to a digital value using a first analog to digital convertor; calculating cable loop impedance from the voltage drop of the measured signal at the set frequency using an FFT window; and calculating the primary current and load impedance using the calculated primary current and primary voltage.
[031] It is another aspect of the present invention, wherein the method records the initial setup impedance and current value using the impedance detector.
[032] According to yet further aspect of the present invention, a method for detecting faults in cables and electrical joints of an electrical network by measuring impedance of cables and electrical joints, said method comprising steps of: calculating the primary current of a high frequency current injection transformer.
[033] It is another aspect of the present invention, wherein if the calculated current value is same as the recorded initial current value, next measurement is triggered; and if the calculated current value is not same as recorded current value, inform the new impedance reading to the user.
Brief description of Drawings
[034] Referring now to the drawings wherein the illustrations are for the purpose of depicting a possible embodiment of the invention only, and not for the purpose of limiting the same.

[035] FIG. 1 illustrates a block diagram of the system employing an impedance detector for Earth (E), Phase (P) and Neutral (N) according to an embodiment of the present invention.
[036] FIG. 2 illustrates a block diagram of the system employing an approximate short circuit distance indicator according to an embodiment of the present invention.
[037] FIG. 3 illustrates a block diagram for determining base impedance characteristic of Earth (E) and Neutral (N) cable loop according to an embodiment of the present invention.
[038] FIG. 4 illustrates a block diagram for determining base impedance characteristic of Earth (E) and Phase (P) cable loop according to an embodiment of the present invention.
[039] FIG. 5 illustrates a block diagram for determining base impedance characteristic of Neutral (N) and Phase (P) cable loop according to an embodiment of the present invention.
[040] FIG. 6 illustrates a flow process for determining base impedance characteristic of Earth (E) and Neutral (N) cable loop according to an embodiment of the present invention.
[041] FIG. 7 illustrates a flow process for determining base impedance characteristic of Earth (E) and Phase (P) cable loop according to an embodiment of the present invention.
[042] FIG.8 illustrates a flow process for determining base impedance characteristic of Phase (P) and Neutral (N) cable loop according to an embodiment of the present invention.
[043] FIG. 9 illustrates a flow process for measuring impedance of Earth (E) and Neutral (N) live cable loop according to an embodiment of the present invention.
[044] FIG. 10 illustrates a flow process for measuring impedance of Earth (E) and Phase (P) live cable loop according to an embodiment of the present invention.
[045] FIG. 11 illustrates a flow process for measuring impedance Phase (P) and Neutral (N) live cable loop according to an embodiment of the present invention.
[046] FIG. 12 illustrates a block diagram of impedance detector for Phase (P) and Neutral (N) cable loop according to another embodiment of the present invention.
[047] FIG. 13 illustrates a flow process for determining base impedance characteristic and measuring impedance of Phase (P) and Neutral (N) cable loop according to another embodiment of the present invention.

Detailed description of the Invention
[048] Referring to FIG. 1, illustrates a block diagram of the system employing an impedance detector according to an embodiment of the present invention. The system is used for detecting faults in cables and electrical joints in an electrical network by measuring impedance of a selected cable loop by means of the impedance detector (20) as shown in FIG. 3. The system comprises of Phase (P), Neutral (N) and Earth (E) (13) cables of an electrical network connected between a distribution transformer (15) and the impedance detector (20). The impedance detector assisting in minimizing power loss in cable path and electrical joints comprising of a microcontroller (1), a band pass filter (8), at least two relays (11a, 11b), plurality of capacitors C1(9), C2(14), C3(12), plurality of schottky diodes (10, 16, 17) and a first analog to digital convertor (2). The microcontroller further comprises of an FFT window (4), a high frequency programmable pulse generator (5), a transistor based amplifier (6) and a second analog to digital convertor (7).
[049] The microcontroller (1) injects a high frequency pulse sweep in a cable loop with a set frequency and amplitude at set injection point. The high frequency programmable pulse generator (5) generates the pulse sweep at pre-determined time intervals. The transistor based amplifier (6) amplifies the generated pulse sweep. The microcontroller (1) regularly injects the pulse sweep at pre-determined time intervals at the set injection point.
[050] The pulse generator (5) generates the pulse sweep at a pre-determined step time with an increment of each step by a pre-determined frequency, where each step for generating the pulse sweep is provided with a set delay period. The impedance detector (20) by means of the FFT window (4) measures the voltage drop across a known resistor R2 at each pulse sweep to calculate the cable loop impedance till resonant frequency is attained. The cable loops include Phase Neutral (P to N), Earth Phase (E to P) and Earth Neutral (E to N) for fault detection in cables and electrical joints.
[051] The band pass filter (8) attenuates noise and signals outside the pass band. The relays (11a, 11b) are used for selecting the cable loop. The capacitors C1, C2, C3 couples high frequency voltage pulse on P, N and E lines and attenuates low frequency high line voltage from entering the impedance detector (20). The schottky diodes (10, 16, 17) provides low impedance path for high frequency and drops low frequency leakage current. The injection point of pulse sweep is at resistor R1 as shown in FIG. 1. The distribution transformer (15) shorts the Neutral (N) and Earth (E) cables.
[052] The system measures and records base impedance characteristics of the cables and electrical joints during installation by means of the impedance detector (20). Further, the impedance detector (20) compares the base impedance characteristics with the calculated cable loop impedance to detect open circuit or short circuit or contact deterioration or rusting or

mechanical wear and tear or cable cuts at pre-determined time intervals. The system remotely customizes the pre-determined time intervals, pre-determined step time, set frequency, set delay period and controls the injection of high frequency pulse sweep.
[053] The system also detects short circuits on the disconnected power lines by injecting high frequency pulse sweep and measure voltage drop across the known resistor R2 to calculate the cable loop impedance. Further, a high frequency current injection transformer is mounted on Phase (P) and Neutral (N) cables to calculate the secondary side loop impedance by measuring the primary side current of the coil as shown in FIG. 12. A power supply (3) is connected to the impedance detector for supplying power to it and its components.
[054] Referring to FIG. 2, illustrates the system employing an approximate short circuit distance indicator along with an MCB according an embodiment of the present invention. The MCB is provided with impedance detector (20) as an auxiliary for tripping in abnormal impedance measurement conditions. The MCB and impedance detector (20) are connected between the distribution transformer (15) and load. As shown in Figures, the power distribution system is single phase having the cable lines Phase (P), Neutral (N) and Earth (E). This system and the impedance detector (20) are applicable for three phase AC or DC power distribution system.
[055] The impedance detector (20) also measures the contact quality and informs the user for corrective measures to provide safety to the electrical equipment. The short locator will display the short distance in meters from the MCB/MCCB/ACB, which can be built as an auxiliary device for MCB. Based on the short circuit loop impedance the system will indicate approximate short circuit distance from the MCB.
[056] Referring to FIG. 3, illustrates a block diagram for impedance measurement between Earth (E) and Neutral (N) according to an embodiment of the present invention. To select the Earth (E) and Neutral (N) cable loop both the relays (11a) and (11b) are connected in ‘normally closed’ condition. The high frequency pulse sweep is injected at resistor R1 and voltage drop across R2 is measured using the FFT window (4) of the microcontroller (1). From this measured voltage value impedance of the loop is calculated to detect the faults such as open circuit, short circuit, contact deterioration, rusting, mechanical wear and tear, cable cuts or other faults.
[057] Referring to FIG. 4, illustrates a block diagram for impedance measurement between Earth (E) and Phase (P) according to an embodiment of the present invention. To select the Earth (E) and Phase (P) cable loop the relay 1 (11a) is connected in ‘normally open’ condition and relay 2 (11b) is connected in ‘normally closed’ condition. The high frequency pulse sweep is injected at resistor R1 and voltage drop across R2 is measured using the FFT window (4) of the microcontroller (1). From this measured voltage value impedance of the loop is calculated to

detect the faults such as open circuit, short circuit, contact deterioration, rusting, mechanical wear and tear, cable cuts or other faults.
[058] Referring to FIG. 5, illustrates a block diagram for impedance measurement between Neutral (N) and Phase (P) according to an embodiment of the present invention. To select the Neutral (N) and Phase (P) cable loop both the relays (11a) and (11b) are connected in ‘normally open’ condition. The high frequency pulse sweep is injected at resistor R1 and voltage drop across R2 is measured using the FFT window (4) of the microcontroller (1). From this measured voltage value impedance of the loop is calculated to detect the faults such as open circuit, short circuit, contact deterioration, rusting, mechanical wear and tear, cable cuts or other faults.
[059] Referring to FIG. 6, illustrates a flow process for determining base impedance characteristic of Earth (E) and Neutral (N) cable loop at the installation of the system. At start of the process (S601), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S602) is selected. Arrange relay 1 (11a) and relay 2 (11b) in ‘normally closed’ condition (S603) and inject the high frequency pulse sweep at injection point at resistor R1 (S604). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S605). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S606). Save the measured amplitude as ZEN (S607).
[060] If ZEN is equal to the applied amplitude ‘Y’ (S608), then a notification of ‘open circuit’ condition is sent to user (S609). If ZEN is not equal to the applied amplitude ‘Y’ (S608), then check if ZEN is greater than a threshold value (0.2) and ZEN is less than the applied amplitude ‘Y (S610). If Yes, the amplitude and frequency table is updated with this measured value (S611). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S612). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance. This resistance value is recorded as base impedance characteristic value for the Earth (E) and Neutral (N) cable loop (S613). If No, an ‘open circuit’ notification is sent to user (S614).
[061] Referring to FIG. 7, illustrates a flow process for determining base impedance characteristic of Earth (E) and Phase (P) cable loop at the installation of the system. At start of the process (S701), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S702) is selected. Arrange relay 1 (11a) in ‘normally open’ condition and relay 2 (11b) in ‘normally closed’ condition (S603) and inject the high frequency pulse sweep is injected at injection point at resistor R1 (S704). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S705). The FFT window (4) of the

microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S706). Save the measured amplitude as ZEP (S707).
[062] If ZEP is equal to the applied amplitude ‘Y’ (S708), then a notification of ‘open circuit’ condition is sent to user (S709). If ZEP is not equal to the applied amplitude ‘Y’ (S708), then check if ZEP is greater than a threshold value (0.2) and ZEP is less than the applied amplitude ‘Y (S710). If Yes, the amplitude and frequency table is updated with this measured value (S711). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S712). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance. This resistance value is recorded as base impedance characteristic value for the Earth (E) and Phase (P) cable loop (S713). If No, an ‘open circuit’ notification is sent to user (S714).
[063] Referring to FIG. 8, illustrates a flow process for determining base impedance characteristic of Phase (P) and Neutral (N) cable at the installation of the system. At start of the process (S801), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S802) is selected. Arrange relay 1 (11a) and relay 2 (11b) in ‘normally open’ condition (S603) and inject the high frequency pulse sweep is injected at injection point at resistor R1 (S804). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S805). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S806). Save the measured amplitude as ZPN (S807).
[064] If ZPN is equal to the applied amplitude ‘Y’ (S808), then a notification of ‘open circuit’ condition is sent to user (S809). If ZPN is not equal to the applied amplitude ‘Y’ (S808), then check if ZPN is greater than a threshold value (0.2) and ZPN is less than the applied amplitude ‘Y (S810). If Yes, the amplitude and frequency table is updated with this measured value (S811). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S812). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance. This resistance value is recorded as base impedance characteristic value for the Phase (P) and Neutral (N) cable loop (S813). If No, an ‘open circuit’ notification is sent to user (S814).
[065] Referring to FIG. 9, illustrates a flow process for measuring impedance of Earth (E) and Neutral (N) live cable loop according to an embodiment of the present invention. At start of the process (S901), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S902) is injected at injection point at resistor R1 (S903 & S904). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S905). The

FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S906). Save the measured amplitude as ZEN (S907).
[066] If ZEN is equal to the applied amplitude ‘Y’ (S908), then a notification of ‘open circuit’ condition is sent to user (S909). If ZEN is not equal to the applied amplitude ‘Y’ (S908), then check if ZEN is greater than a threshold value (0.2) and ZEN is less than the applied amplitude ‘Y (S910). If Yes, the amplitude and frequency table is updated with this measured value (S911). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S912). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance (S913).
[067] The system compares the measured impedance value with the recorded base impedance characteristic value set during the installation of the system of this electrical network (S914). Informing the end user for taking corrective actions if the measured value is increased from base value (S915). The system maintains the user set delay between the measurements and reset the measurement (S916). If No, an ‘open circuit’ notification is sent to user (S917).
[068] Referring to FIG. 10, illustrates a flow process for measuring impedance of Earth (E) and Phase (P) live cable loop according to an embodiment of the present invention. At start of the process (S1001), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S1002) is injected at injection point at resistor R1 (S1003 & S1004). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S1005). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S1006). Save the measured amplitude as ZEP (S1007).
[069] If ZEP is equal to the applied amplitude ‘Y’ (S1008), then a notification of ‘open circuit’ condition is sent to user (S1009). If ZEP is not equal to the applied amplitude ‘Y’ (S1008), then check if ZEP is greater than a threshold value (0.2) and ZEP is less than the applied amplitude ‘Y (S1010). If Yes, the amplitude and frequency table is updated with this measured value (S1011). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S1012). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance (S1013).
[070] The system compares the measured impedance value with the recorded base impedance characteristic value set during the installation of the system of this electrical network (S1014). Informing the end user for taking corrective actions if the measured value is increased from base

value (S1015). The system maintains the user set delay between the measurements and reset the measurement (S1016). If No, an ‘open circuit’ notification is sent to user (S1017).
[071] Referring to FIG. 11, illustrates a flow process for measuring impedance of Phase (P) and Neutral (N) live cable loop according to an embodiment of the present invention. At start of the process (S1101), a pulse sweep having a frequency ‘X’ of 5 kHz with an amplitude ‘Y’ of 5v (S1102) is injected at injection point at resistor R1 (S1103 & S1104). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S1105). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S1106). Save the measured amplitude as ZPN (S1107).
[072] If ZPN is equal to the applied amplitude ‘Y’ (S1108), then a notification of ‘open circuit’ condition is sent to user (S1109). If ZPN is not equal to the applied amplitude ‘Y’ (S1108), then check if ZPN is greater than a threshold value (0.2) and ZPN is less than the applied amplitude ‘Y (S1110). If Yes, the amplitude and frequency table is updated with this measured value (S1111). Further, the maximum amplitude is determined along with frequency at this maximum amplitude (S1112). Further, the capacitive reactance is calculated at this maximum frequency which is resonant frequency, where capacitive reactance is equal to inductive reactance and the impedance is pure resistance (S1113).
[073] The system compares the measured impedance value with the recorded base impedance characteristic value set during the installation of the system of this electrical network (S1114). Informing the end user for taking corrective actions if the measured value is increased from base value (S1115). The system maintains the user set delay between the measurements and reset the measurement (S1116). If No, an ‘open circuit’ notification is sent to user (S1117).
[074] Referring to FIG. 12, illustrates a block diagram of impedance detector for Phase (P) and Neutral (N) cable loop according to another embodiment of the present invention. A high frequency current injection transformer (18) is mounted on Phase (P) and Neutral (N) cable loop with the impedance detector (20) to measure the cable loop impedance. The current on the primary side of the transformer is measured to calculate the secondary loop impedance. The primary current will change based on the secondary loop impedance. The manner of injecting the high frequency pulse sweep is same as shown in FIG. 1.
[075] Referring to FIG. 13, illustrate a flow process for determining base impedance characteristic and measuring impedance of Phase (P) and Neutral (N) cable loop according to another embodiment of the present invention. At start of the process (S1301), a pulse sweep having a frequency ‘X’ of 5 kHz with amplitude ‘Y’ of 5v (S1302) is injected at injection point at resistor R1 (S1303). Amplitude and frequency across the known resistor R2 is measured using

a first analog to digital convertor (2) (S1304). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S1305). Save the measured amplitude as ZPN (S1306).
[076] Further, calculate the primary current (S1307) and load impedance from primary current and primary voltage (S1308) by compensating losses. Record the initial setup impedance and current values (S1309). Check if time for measurement is triggered (S1310). If Yes (S1311), set a pulse sweep having a frequency ‘X’ of 5 kHz with amplitude ‘Y’ of 5v (S1312) is injected at injection point at resistor R1 (S1313). Amplitude and frequency across the known resistor R2 is measured using a first analog to digital convertor (2) (S1314). The FFT window (4) of the microcontroller (1) is used to measure the cable loop impedance using the calculated voltage drop/ amplitude across the resistor R2 (S1315). Measure the primary current (S1316).
[077] If the measured current is same as the recorded initial setup current value (S1317), then wait for the timer to trigger next measurement (S1318). If the measured current is not same as the recorded initial setup current value (S1317), then a notification is provided to user regarding the change in the new impedance (S1319) and wait for the timer to trigger next measurement (S1318). Further, if time for measurement is not triggered (S1310), then wait for the timer to trigger next measurement (S1318).
[078] The pulse sweep is generated at a pre-determined step time with an increment of each step by a pre-determined frequency, where each step for generating the pulse sweep is provided with a set delay period. At each increment of the pre-determined frequency, the measured amplitude is recorded till the said pre-determined frequency reaches resonant frequency.
[079] For illustration, the pulse sweep is generated at a frequency of 10Khz and till 100 KHz with a step time of 5 milli sec along with an increment of each step by a frequency of 10KHz till the FFT window (4) output detects resonant frequency of the electrical network. Each step will have a delay of 10 minutes. The same test will be repeated between Phase (P) Neutral (N), Phase (P) Earth (E) and Neutral (N) Earth (E) cable loops. This measurment intervals can be set based on the user preference, programmable measurment schedule function has been provided in the impedance detector (20).
[080] It is to be understood that the invention described in the above paragraphs relates to specific embodiments and the present invention is not limited to the preferred embodiments shown. It is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

WE CLAIM:
1. A system for detecting faults in cables and electrical joints of an electrical network by
measuring impedance of cables and electrical joints, said system comprising of:
an impedance detector (20) assisting in minimizing power loss in cable path and electrical joints, further comprising of:
a microcontroller (1) for injecting a high frequency pulse sweep in a cable loop with a set frequency & amplitude at set injection point;
a band pass filter (8) for attenuating noise and signals outside the pass band; at least two relays (11a, 11b) for selecting the cable loop;
plurality of capacitors C1 (9), C2 (14) and C3 (12) for coupling high frequency voltage pulse on P, N and E lines and attenuates low frequency high line voltage from entering the impedance detector (20);
plurality of schottky diodes (10, 16, 17) for providing low impedance path for high frequency and drops low frequency leakage current; and
Phase (P), Neutral (N) and Earth (E) cables of an electrical network connected between a distribution transformer (15) and the impedance detector (20),
wherein the system; measures and records base impedance characteristics of the cables and electrical joints during installation by means of the impedance detector (20),
wherein the impedance detector (20) measures the voltage drop across a known resistor R2 to calculate the cable loop impedance, and
wherein the impedance detector (20) compares the base impedance characteristics with the calculated cable loop impedance to detect open circuit, short circuit, contact deterioration, rusting, mechanical wear and tear, cable cuts or other faults at pre-determined time intervals.
2. The system as claimed in claim 1, wherein a first analog to digital convertor (2) of the
impedance detector (20) converts voltage drop across the known resistor R2 to a digital value for
analyzing.
3. The system as claimed in claim 1, wherein the microcontroller (1) comprising of:
an FFT window (4) for detecting the amplitude of the measured signal;
a high frequency programmable pulse generator (5) to generate the pulse sweep at pre-determined time intervals;
a transistor based amplifier (6) for amplifying the generated pulse sweep; and
a second analog to digital convertor (7) to convert voltage drop across resistor R2 to a digital value for analyzing,
wherein the microcontroller (1) regularly injects the pulse sweep at pre-determined time intervals at the set injection point.
4. The system as claimed in claim 1 or 5, wherein the set injection point is at a resistor R1.

5. The system as claimed in claim 1 or 3, wherein the pulse generator (5) generates the pulse sweep at a pre-determined step time with an increment of each step by a pre-determined frequency, where each step for generating the pulse sweep is provided with a set delay period.
6. The system as claimed in claim 5, wherein the FFT window (4) measures the voltage drop across the known resistor R2 at each pulse sweep to calculate the cable loop impedance till resonant frequency is attained.
7. The system as claimed in claim 1, wherein the pulse sweep is injected between Phase Neutral (P to N), Earth Phase (E to P) and Earth Neutral (E to N) cable loops for fault detection in cables and electrical joints.
8. The system as claimed in claim 1 or 5, wherein the system remotely customizes the pre¬
determined time intervals, pre-determined step time, set frequency, set delay period and controls
the injection of high frequency pulse sweep.
9. The system as claimed in claim 1, wherein the distribution transformer (15) shorts the Neutral
(N) and Earth (E) cables.
10. The system as claimed in claim 1, wherein a high frequency current injection transformer (18) is mounted on Phase (P) and Neutral (N) cables to calculate the secondary side loop impedance by measuring the primary side current of the coil.
11. The system as claimed in claim 1, wherein the system also detects short circuits on the disconnected power lines by injecting high frequency pulse sweep and measure voltage drop across the known resistor R2 to calculate the cable loop impedance.
12. The system as claimed in claim 1, wherein a power supply (3) is provided for supplying power to the impedance detector (20) and its components.
13. A method for calculating the cable loop impedance by means of an impedance detector (20) of an electrical network, comprising steps of:
selecting a cable loop by arranging positions of at least two relays (11a, 11b);
injecting high frequency pulse sweep on the cable loop with a set frequency and amplitude at a set injection point using a pulse generator (5);
measuring and converting the voltage drop across a known resistor R2 to a digital value using a first analog to digital convertor (2);
calculating cable loop impedance from the voltage drop of the measured signal at the set frequency using an FFT window (4);

if the measured amplitude is equal to the applied amplitude, an open circuit notification is sent to user;
if the measured amplitude is not greater than the threshold value and not less than the applied amplitude, an open circuit notification is sent to user;
if the measured amplitude is greater than a threshold value and less than the applied amplitude, updating the measured amplitude and frequency table along with the calculated cable loop impedance at set frequency;
finding the maximum amplitude and the corresponding frequency at this maximum amplitude which is resonant frequency; and
calculating capacitive reactance at this resonant frequency,
wherein the capacitive reactance is equal to inductive reactance at the resonant frequency and hence the cable loop impedance at this resonant frequency is equal to pure resistance.
14. The method as claimed in claim 13, wherein the resistance is recorded as base impedance characteristic value for the selected cable loop set during the starting of the installation using the impedance detector (20).
15. A method for detecting faults in cables and electrical joints of an electrical network by measuring impedance of cables and electrical joints, said method comprising steps of:
calculating the cable loop impedance for a selected cable loop of an electrical network as claimed in claim 13.
16. The method as claimed in claim 15, wherein
comparing the calculated cable loop impedance with the recorded base impedance characteristic value as claimed in claim 14; and
informing the user for necessary corrective actions according to the increase of the calculated cable loop impedance value from the base impedance characteristic value.
17. The method as claimed in claim 13, wherein the pulse sweep is generated at a pre-determined
step time with an increment of each step by a pre-determined frequency, where each step for
generating the pulse sweep is provided with a set delay period.
18. The method as claimed in claim 17, wherein at each increment of the pre-determined
frequency, the measured amplitude is recorded till the said pre-determined frequency reaches
resonant frequency.
19. The method as claimed in claim 13, wherein the cable loops include Phase Neutral (P to N),
Earth Phase (E to P) and Earth Neutral (E to N) cable loops for fault detection in cables and
electrical joints.

20. A method for calculating the primary current of a high frequency current injection
transformer (18) by means of an impedance detector (20) of an electrical network, comprising
steps of:
selecting a cable loop by arranging positions of at least two relays (11a, 11b);
injecting high frequency pulse sweep on the cable loop with a set frequency and amplitude at a set injection point using a pulse generator (5);
measuring and converting the voltage drop across a known resistor R2 to a digital value using a first analog to digital convertor (2);
calculating cable loop impedance from the voltage drop of the measured signal at the set frequency using an FFT window (4); and
calculating the primary current and load impedance using the calculated primary current and primary voltage.
21. The method as claimed in claim 20, wherein the method records the initial setup impedance
and current value using the impedance detector (20).
22. A method for detecting faults in cables and electrical joints of an electrical network by
measuring impedance of cables and electrical joints, said method comprising steps of:
calculating the primary current of a high frequency current injection transformer (18) as claimed in claim 20.
23. The method as claimed in claim 22, wherein
if the calculated current value is same as the recorded initial current value as claimed in claim 21, next measurement is triggered; and
if the calculated current value is not same as recorded current value, inform the new impedance reading to the user.