REALTED APPLICATION

Benefit is claimed to India Provisional Application No. ^CHE/2010, titled "SYSTEM AND METHOD FOR SENSING THE PRESENCE OF ELECTRICAL GROUND CONNECTION AND MEASURING THE GROUND RESISTANCE" by Murugesan, Shanmugasundaram, filed on 23rd December 2010, which is herein incorporated in its entirety by reference for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to the field of electrical systems, and more particularly relates to a system and method of measuring ground resistance.

BACKGROUND OF THE INVENTION

Earth grounding is used to provide a connection from electrical/electronics system and power to earth. Earth grounding provides protection for faults, lighting strikes, RFI, EMI, and other interference. Proper grounding is required by many industries and grounding recommendations and practices that exist from many organizations such as National Electric Code (NEC) and many others. Poor grounding can result in injury or death to people, animals and plants. It can also result in damage, poor operation, or the failure of equipment and electronics to operate.

One way to ensure proper grounding is through monitoring the ground resistance. For this purpose, ground testers are used to measure resistance of the earth to a buried ground electrode. The grounding connection is considered as faulty if a ground tester records more than 20% increase in the standard ground resistance. In such case, the source of the problem associated with the grounding is identified and corrected so that the grounding resistance is brought to normal.

Current ground testers measure ground resistance by applying voltage across a ground electrode associated with a electrical/electronic device and buried in the earth for grounding purpose, and a separate conductor placed in the earth. The separate conductor is buried in the earth at a pre-determined distance from the ground electrode so that a return path for ground current is formed between the ground electrode and the separate conductor. Due to resistance of the ground and the applied voltage certain amount of current flows in the return path. The ground testers measure the current flowing through the ground in the return path and computes ground resistance by applying the Ohm's law. Therefore, every time ground resistance is to be measured, one or more separate conductors have to be placed in the earth. The use of separate conductors may add up to the cost of measuring the ground resistance and also may not be feasible in real time measurement of ground resistance.

SUMMARY OF THE INVENTION

The present invention provides a system and method for measuring ground resistance. In one aspect, a system includes a load having a first ground electrode, an energy supply unit connected to the load through a positive line and a neutral line, for supplying power. The system further includes a ground resistance measurement unit which includes a power control unit having a first terminal connected to the first ground electrode and a second terminal connected to the neutral line of the energy supply unit, where the neutral line is connected to a second ground electrode at the energy supply unit. The ground resistance measurement unit further includes a map of calibrated resistance values and at least one current sensor disposed in the ground and connected to the processor unit. The power control unit applies a pre-determined voltage to the first ground electrode and the neutral line. The current sensor senses the ground current in a return path between the first ground electrode and the second ground electrode. Accordingly, the processor unit computes a ground resistance associated with the first ground electrode based on the predetermined voltage, the ground current and the calibrated resistance values in the map.

In another aspect, an apparatus includes a processor unit coupled to a power control unit, a current sensor which is disposed in the ground and connected to the processor unit, and a memory unit coupled to the processor unit, where the memory includes the map of calibrated resistance values. The power control unit applies a pre-determined voltage to a first ground electrode associated with the load via a first terminal and a neutral line of the energy supply unit via a second terminal, where the neutral line is connected to a second ground electrode associated with the energy supply unit. The current sensor senses the ground current in the return path between the first ground electrode and the second ground electrode. Accordingly, the processor unit computes a ground resistance associated with the first ground electrode based on the pre-determined voltage, the ground current and the calibrated resistance values in the map.

In yet another aspect, a method of measuring ground resistance includes applying a pre-determined voltage to a first ground electrode of a load and a neutral line of an energy supply unit supplying power to the load, where the neutral line is connected to a second ground electrode associated with the energy supply unit. The method also includes sensing current flowing through the ground in a return path between the first ground electrode and the second ground electrode, and computing the ground resistance associated with the first ground electrode in real time using the calibrated resistance values in the map based on the sensed ground current.

Other features of the embodiments will be apparent from the accompanying drawings and from the detailed description that follows.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1 is a system diagram illustrating a system for measuring ground resistance associated with a load in real time, according to one embodiment.

Figure 2 is a block diagram illustrating various components of a ground resistance measurement unit such as those shown in Figure 1, according to one embodiment.

Figure 3 is a process flowchart illustrating an exemplary method of measuring ground resistance associated with a first ground electrode at a load site, according to one embodiment.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system and method of measuring ground resistance. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

In the document, the terms "neutral line" and "negative line" are interchangeably used throughout the document.

Figure 1 is a system diagram illustrating a system 100 for measuring ground resistance associated with a load in real time, according to one embodiment. In particular, the system 100 includes a load 102, an energy supply unit 104, a ground resistance measurement unit 106, and a backend server 126.

The load 102 may be electrical/electronic equipment which operates based on power supplied by the energy supply unit 104 located to a energy supply unit or transformer location. The energy supply unit 104 supplies the power to the load through a positive line 122 and a negative line 124. The load 102 is grounded via a first ground electrode 116 to provide protection for faults, lighting strikes, RFI, EMI and other interference. Similarly, the energy supply unit is also grounded via a second ground electrode 118. The negative line 124 is connected to the ground electrode 124 to provide protection from faults. Therefore, the negative line 123 is referred to as a neutral line.

The ground resistance measurement unit 106 is a device which is deployed at the load site to detect a faulty ground connection and to ensure that the ground resistance associated with the load 102 is always normal. As shown in Figure 1, the ground resistance measurement unit 106 includes a first terminal 112 connected to the first ground electrode 116, a second terminal 114 connected to the second ground electrode 114, a map of calibrated resistance values 110, and a current sensor 108 (e.g., Hall Effect sensor) buried in the ground 120.

In an exemplary operation, the ground resistance measurement unit 106 applies a predetermined voltage to the first ground electrode 116 and the negative line 118 via the first terminal 112 and the second terminal 114 respectively. Since the negative line 124 is connected the second ground electrode 118, a return path is formed between the first ground electrode 116 and the second ground electrode 118. The application of the voltage to the first ground electrode 114 and the negative line 116 causes potential difference between the first ground electrode 114 and the second ground electrode 116 which results in current to flow through the ground 120 in the return path. The current sensor 108 senses the ground current in the return path and provides the signal indicative of amount of current flowing through the ground 120 to the ground resistance measurement unit 106.

Accordingly, the ground resistance measurement unit 106 computes a ground resistance associated with the first ground electrode 116 based on the voltage applied to the first ground electrode 116 and the negative line 124 and the current flowing through the ground 120. The ground resistance measurement unit 106 determines an actual ground resistance corresponding to the computed ground resistance based on the calibrated resistance values in the map 110. In one embodiment, different voltages are applied to the first ground electrode 116 and a separate ground conductor (not shown) buried in the ground at the load site. The current values are measured corresponding to each of the voltages applied. Accordingly, ground resistance is computed for each voltage value and corresponding current value measured in the return path. In this manner, a map 110 containing actual resistance values for specific voltage and current is constructed and loaded in the ground resistance measurement unit 106 so that the ground resistance measurement unit 106 can compute an actual resistance value associated with the first ground electrode 116 in real time using the calibrated resistance values in the map 110. It can be noted that, the map 110 can be specific to the geographic location associated with the load 102.

Additionally, the ground resistance measurement unit 106 compares the actual ground resistance with a pre-determined threshold ground resistance and determines whether the actual ground resistance is greater than the predetermined threshold ground resistance. If the actual ground resistance is greater than the pre-determined ground resistance, the ground resistance measurement unit 106 generates an alarm condition indicative of a fault ground connection associated with the load 102. The alarm condition may be audio alarm or a visual notification on a display (e.g., blinking of an indicator light). Additionally, the ground resistance measurement unit 106 communicates the alarm condition indicative of the faulty ground connection associated with the load 102 to the backend server 126 (e.g., of a service provider company, and/or maintenance company) via any wireless communication channel so that appropriate action can be taken to correct the faulty ground connection at the load 102. In this manner, the ground resistance is measured in real time. In one exemplary implementation, the ground resistance measurement unit 106 can be employed at a cellular site to measure ground resistance associated with a base station in real time by applying voltage to a ground electrode of the base station and a neutral connection associated with a power supply line, and measuring current flowing in a return path.

Figure 2 is a block diagram illustrating various components of the ground resistance measurement unit 106 such as those shown in Figure 1, according to one embodiment. The ground resistance measurement unit 106 includes the current sensor 108, a processor unit 202, a power control unit 204, an analog to digital converter (ADC) 206, memory 208, a display 210, an alarm 212, and a transceiver 214. The memory 208 contains the map 110 and one or more machine-readable instructions 216 for measuring the ground resistance. The power control unit 204, the ADC 206, the memory 208, the display 210, the alarm 212, and the transceiver 214 are connected to the processor unit 202.
In an exemplary operation, the processor unit 202 determines a value of voltage to be applied to the first ground electrode 116 and the second ground electrode 118 and provides a signal indicating the value of voltage to the power control unit 204. In one exemplary implementation, the processor unit 202 determines the value of voltage using the map 110. As described above, the map 110 contains different voltage values and corresponding current and resistance values computed at the load site prior to installing the ground resistance measurement unit 106. Based on these values, the processor unit 202 selects a voltage value to be applied by the power control unit 204 for measuring ground resistance at the load site.

Accordingly, the power control unit 204 applies the pre-determined voltage to the first ground electrode 116 and the negative line 124 of the energy supply unit 104, resulting in a flow of current through the ground 120 in return path. The current sensor 108 buried in the ground 120 senses the amount of the current flowing through the ground 120 and provides an analog signal indicative of the amount of ground current to the ADC 206. The ADC converts the analog signal into digital signal and provides the digital signal indicating the ground current value to the processor unit 202.

The processor unit 202 computes the ground resistance associated with the first ground electrode 116 based on the current value and the pre-determined voltage. Further, the processor unit 202 determines actual ground resistance value from the map 110 using the computed ground resistance, the predetermined voltage and the measure ground current in real time. The processor unit 202 thus compares the actual ground resistance value with a predetermined threshold ground resistance (e.g., a standard ground resistance) and determines whether the actual ground resistance is greater than the predetermined threshold ground resistance. If the actual ground resistance is greater, then the processor 202 generates an alarm condition indicative of a faulty ground connection at the load site and notifies authority via the alarm 212 and/or the display 210. Also, the processor unit 202 communicates the alarm condition indicative of the faulty ground connection at the load site to the backend server 126 via the transceiver 214. In this manner, the ground resistance measurement unit 106 enables to detect a faulty ground connection at the load 102 by measuring ground resistance in real time using the map 110 preloaded in the memory 208.

Figure 3 is a process flowchart 300 illustrating an exemplary method of measuring ground resistance associated with the first ground electrode 116 at a load site, according to one embodiment. At step 302, a pre-determined voltage is applied to the first ground electrode 116 of the load 102 and the neutral line 124 of the energy supply unit 104 by the power control unit 204. At step 304, current flowing through the ground 120 in a return path is sensed by the current sensor 108. At step 306, ground resistance associated with the first ground electrode 116 is computed based on the pre-determined voltage value and the ground current value.

At step 308, actual ground resistance corresponding to the computed ground resistance from the map containing calibrated resistance values 110. At step 310, the actual ground resistance is compared with a pre-determined threshold ground resistance. At step 312, it is determined whether the computed ground resistance is greater than the pre-determined threshold ground resistance. At step 314, an alarm condition indicative of a faulty ground connection at the load 102 is generated. The alarm condition may be an audio alarm or visual indicator indicating that the ground connection is faulty. At step 316, the alarm condition indicative of the faulty ground connection is communicated to the backend server 126.

It can be noted that, one or more of the steps 302-316 are performed by the processor unit 202 upon execution of the machine-readable instructions 218 stored in the memory 208. Moreover, in one embodiment, a computer-readable storage medium having instructions stored therein, that when executed by the processor unit 202, cause the processor unit to perform one or more steps described in Figure 3.

The present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, selectors, estimators, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.

We claim:

1. A system comprising:
a load comprising a first ground electrode;
a energy supply unit connected to the load through a positive line and a neutral line for supplying power; and a ground resistance measurement unit comprising:
a power control unit having a first terminal connected to the first ground electrode and a second terminal connected to the neutral line of the energy supply unit, wherein the neutral line is connected to a second ground electrode at the energy supply unit;
a processor unit coupled to the power control unit;
a memory unit coupled to the processor unit, wherein the memory comprises a map including calibrated resistance values; and
at least one current sensor disposed in the ground and connected to the processor unit, wherein the power control unit is configured for applying a predetermined voltage to the first ground electrode via the first terminal and the neutral line via the second terminal, and wherein the current sensor is configured for sensing the ground current in a return path between the first ground electrode and the second ground electrode, and wherein the processor unit is configured for computing a ground resistance associated with the first ground electrode in real time using the pre-determined voltage, the sensed ground current, and the calibrated resistance values in the map.

2. The system of claim 1, wherein the processor unit is further configured for:
comparing the computed ground resistance with a predetermined threshold
ground resistance;
determining whether the computed ground resistance is greater than the predetermined threshold; and
generating an alarm condition indicative of a faulty ground connection at the load if the computed ground resistance is greater than the predetermined threshold ground resistance.

3. The system of claim 2, further comprising a backend server wirelessly coupled to the ground resistance measurement unit for receiving the alarm condition indicative of faulty ground connection from the ground resistance measurement unit.

4. The system of claim 1, wherein the processor unit is configured for providing the value of pre-determined voltage to be applied to the first ground electrode and the neutral line to the power control unit based on the calibrated resistance values stored in the map.

5. The system of claim 1, wherein in computing the ground resistance associated with the first ground electrode using the current sensed by the current sensor and the calibrated resistance values in the map, the processor unit is configured for
computing a ground resistance associated with the first ground electrode based on the predetermined voltage applied across the first ground electrode and the neutral line and the value of current sensed by the current sensor; and
determining an actual ground resistance corresponding to the computed ground resistance from the map.

6. The system of claim 1, further comprising:
an analog to digital converter configured for converting an analog value of current sensed by the current sensor to a digital value and providing the digital value of the sensed current to the processor unit.

7. An apparatus comprising:
a power control unit having a first terminal connected to a first ground electrode associated with a load and a second terminal connected to a neutral line of an energy supply unit, wherein the neutral line is connected to a second ground electrode associated with the energy supply unit;
a processor unit coupled to the power control unit;
a memory unit coupled to the processor unit, wherein the memory comprises a map including calibrated resistance values;
at least one current sensor disposed in the ground and connected to the processor unit, wherein the power control unit is configured for applying a predetermined voltage to the first ground electrode via the first terminal and the neutral line via the second terminal, and wherein the current sensor is configured for sensing the ground current in a return path between the first ground electrode and the second ground electrode, and wherein the processor unit is configured for computing a ground resistance associated with the first ground electrode in real time using the current sensed by the current sensor and the calibrated resistance values in the map.

8. The apparatus of claim 7, wherein the processor unit is further configured for:
comparing the computed ground resistance with a predetermined threshold
ground resistance;
determining whether the computed ground resistance is greater than the predetermined threshold; and
generating an alarm condition indicative of a faulty ground connection at the load if the computed ground resistance is greater than the predetermined threshold ground resistance.

9. The apparatus of claim 8, further comprising a transceiver wirelessly coupled
to a backend server for communicating the alarm condition indicative of faulty
ground connection to the backend server.

10. The apparatus of claim 7, wherein the processor unit is configured for providing the value of pre-determined voltage to be applied to the first ground electrode and the neutral line to the power control unit based on the calibrated resistance values stored in the map.

11. The apparatus of claim 7, wherein in computing the ground resistance associated with the first ground electrode using the current sensed by the current sensor and the calibrated resistance values in the map, the processor unit is configured for:

computing a ground resistance associated with the first ground electrode based on the predetermined voltage applied across the first ground electrode and the neutral line and the value of current sensed by the current sensor; and
determining an actual ground resistance corresponding to the computed ground resistance from the map.

12. The apparatus of claim 7, further comprising:
an analog to digital converter configured for converting an analog value of current sensed by the current sensor to a digital value and providing the digital value of the sensed current to the processor unit.

13. A method of measuring resistance associated with the ground, comprising:
applying a pre-determined voltage to a first ground electrode of a load and a
neutral line of an energy supply unit supplying power to the load, wherein the neutral line is connected to a second ground electrode associated with the energy supply unit;
sensing current flowing through the ground in a return path between the first ground electrode and the second ground electrode; and
computing a ground resistance associated with the first ground electrode in real time using calibrated resistance values in a map based on the sensed ground current.

14. The method of claim 13, further comprising:
comparing the computed ground resistance with a predetermined threshold ground resistance;
determining whether the computed ground resistance is greater than the predetermined threshold; and
generating an alarm condition indicative of a faulty ground connection at the load if the computed ground resistance is greater than the predetermined threshold ground resistance.

15. The method of claim 14, further comprising communicating the alarm
condition indicative of faulty ground connection to a backend server.

16. The method of claim 13, wherein in applying the pre-determined voltage to the first ground electrode and the neutral line, the amount of pre-determined voltage to be applied to the first ground electrode and the neutral line is determined based on the calibrated resistance values in the map.

17. The method of claim 13, wherein computing the ground resistance associated with the first ground electrode using the calibrated resistance values in the map comprises:
computing a ground resistance associated with the first ground electrode based on the predetermined voltage applied across the first ground electrode and the neutral line and the value of current sensed by the current sensor; and
determining an actual ground resistance corresponding to the computed ground resistance from the map.

18. The method of claim 13, further comprising:
converting an analog value of current sensed by the current sensor to a digital value; and
providing the digital value of the sensed current for computing to ground resistance.