FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to online remote monitoring system and more particularly, pertains to devices for online remote monitoring of a grounding system.

BACKGROUND OF INVENTION
[002] The process of transferring immediate discharge of electrical energy directly to the earth by utilizing a low resistance wire is known as the electrical grounding. Normally the passive parts of the electrical equipment, which an operator may come in contact with, are grounded by connecting the said parts of the equipment or neutral of supply system to the ground or earth pit.

[003] Mostly, galvanized iron is used for the grounding of equipment by almost all organizations. This grounding provides a low resistance path to the leakage current. The short circuit current of the equipment passes to the earth which has zero potential (in case of line to earth fault). Thus, equipment grounding protects the system and equipment from damage. In particular, grounding of equipment is essential because of the following reasons:

a) It protects the operating personnel from electrical shock as the passive parts of the equipment are kept at earth potential by means of the earth connection;
b) Grounding provides the easiest path to the flow of short circuit current even after the failure of the insulation;
c) Grounding protects the apparatus and people from the high voltage surges and lightning discharge as the huge current caused by a lightning goes directly to earth; and
d) Equipment failures may also be avoided with proper grounding. For a switchboard, where potential transformers are connected, the primary neutral of them are earthed through the system grounding. Failure of this grounding will induce unbalanced overvoltage across them, henceforth will result in insulation failure of them. Also the core of the transformer is earthed at one single point through the grounding of the body of the transformer. Failure of this grounding will result in overheating of the core, thereby resulting in failure of the transformer.

[004] Conventionally, the grounding of all of the equipment of a power station were monitored by measuring the earth resistance offline, every two years. If the earth resistance was found to be within the prescribed limit (<= 0.5 ohm for a new station and <=1.0 ohm for an old station) then the equipment earth was considered healthy. And if the measured value exceeded the prescribed value, then maintenance of the earth pit is carried out stringently. The drawbacks associated with this conventional solution is that in case the health of the grounding of any equipment of a power stations suddenly deteriorates, the same will only be detected by the maintenance team during the next inspection tenure or during failure of an expensive or critical equipment over at that power station.

[005] To overcome the said drawbacks associated with the conventional solution, another existing solution involves the applicant Earthing the body of any equipment at two points for redundancy through copper or GI flats. However, the drawbacks associated with this other existing solution are as follows:
a) Complete discontinuity of the grounding system due to theft of copper / GI flats; and
b) High resistance for the earth due to rusting or deposition of copper sulphate or oxides in the joints in the path to the earth pit.

[006] Accordingly, there is a need to overcome the drawbacks associated with the conventional mechanisms for detecting the health of the grounding equipment. In particular, to there is a need for remotely monitoring the continuity of the grounding at all power stations, all captive installations and areas having HV/EHV/UHV installations.

[007] The above-described need for devices for online remote monitoring of a grounding system of a power station is merely intended to provide an overview of some of the shortcomings of conventional systems / mechanism / techniques, and are not intended to be exhaustive. Other problems/ shortcomings with conventional systems/ mechanism /techniques and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.

SUMMARY OF THE INVENTION
[008] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[009] An object of the present invention is to alleviate the drawbacks associated with conventional mechanisms for grounding equipment at a power station.

[0010] Another object of the present invention is to remotely monitor the grounding of all of the equipment of a power station.

[0011] Yet another object of the present invention is to provide devices for online remote monitoring of the grounding of a power station.

[0012] According to a first aspect of the present invention, there is provided a device to remotely monitor disconnection of a grounding system of a power station. The device comprising: a first contactor coil, a second contactor coil, a first indication lamp to indicate normal operation of the grounding system, and an audio-visual alarm to indicate disconnection of the grounding system, wherein one end of said first contactor coil is electrically connected to Earth of an AC supply, and the other end of said first contactor is electrically connected to Neutral of said AC supply; and wherein one end of said second contactor coil is electrically connected in series to NC contact of said first contactor coil, and the other end of said second contactor coil is electrically connected to the Neutral of said AC supply.

[0013] According to a second aspect of the present invention, there is provided a device to remotely monitor high resistance at a grounding system of a power station, said device comprises: a first interconnecting transformer, a second interconnecting transformer, a current transformer, an undercurrent sensor relay, and an audio-visual alarm to indicate high resistance at the grounding system, wherein one end of said current transformer is electrically connected to said first interconnecting transformer, and the other end of said current transformer is electrically connected to said second interconnecting transformer; and wherein said current transformer is operatively coupled to the relay.

[0014] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0015] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0016] Figure 1 illustrates the basic connection diagram of a device for remote monitoring during complete discontinuity of grounding system in the event of theft of copper and GI flats, in accordance with an embodiment of the present invention.

[0017] Figure 2 illustrates the basic connection diagram of a device for remote monitoring during high resistance for the grounding system in the event of rusting or deposition of sulphate at the joints in the connection to the earth pit, in accordance with another embodiment of the present invention.

[0018] It is to be understood that the attached drawings are for the purpose of illustrating the concepts of the invention and may not be to scale.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0019] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0020] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0021] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0022] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0023] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0024] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0025] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0026] The present invention lies in providing devices for online remote monitoring of a grounding system of a power station.

[0027] The conventional technique of monitoring the grounding of all of the equipment of a power station was by measuring the earth resistance offline, every two years. If the earth resistance was found to be within the prescribed limit (<= 0.5 ohm for a new station and <=1.0 ohm for an old station) then the equipment earth was considered healthy. And if the measured value exceeded the prescribed value, then maintenance of the earth pit is carried out stringently. However, the drawbacks associated with the conventional offline solution was that, in case the health of the grounding of any equipment of the power stations suddenly deteriorates, the same will not be detected immediately and accordingly, suitable measures cannot be taken promptly since the deterioration will only be detected by the maintenance team during the next inspection which would most likely result in failure of an expensive or critical equipment over at the power station.

[0028] To overcome said drawbacks, another existing solution involves the applicant Earthing the body of any equipment at two points for redundancy through copper or GI flats. However, the drawbacks associated with said alternative existing solution are as follows:
a) Complete discontinuity of the grounding system due to theft of copper / GI flats; and
b) High resistance for the earth due to rusting or deposition of copper sulphate or oxides in the joints in the path to the earth pit.

[0029] To overcome said drawbacks of conventional systems, the exemplary embodiments of present invention disclose devices for online remote monitoring of a grounding system of a power station. The system of the present invention may be readily available and very cheap, thereby making the same to be very economical. Further, there exists no remote monitoring system to monitor the equipment and system Earthing at a power station. It reduces the maintenance strategy for measurement and maintenance of earth resistance for the equipment in a power station since the operator is aware of the condition of system and equipment Earthing at any time without taking shutdown of the plant and executing electrical test for the equipment.

[0030] For the first abnormal situation i.e., complete discontinuity of grounding system due to theft of copper and GI flats, two 230 V AC contactor coils are installed with an auxiliary supply of one fed through earth and neutral of AC supply and the other being fed through the phase of AC supply in series with NC contact of the previous contactor and neutral of AC supply. During normal condition, an indication lamp, showing healthy system will be glowing at the local relay panel and during missing of the copper and GI flats, the indication lamp, showing unhealthy system will be glowing at the local relay panel. The two indication lamps having two different colours, such as but not limited to, red colour lamp to indicate theft and green colour lamp to indicate normal operation. Further, an alarm will also be rung at the control centre via a very high frequency (VHF) alarm. After getting the alarm, suitable actions need to be taken by the maintenance team for rectifying the problem. Moreover, additional precautions need to be taken regarding the safety aspects, since if the grounding system becomes discontinuous then the externally applied auxiliary voltage across the grounding system needs to be cut off so as to avoid electrifying the body of the equipment which may in turn electrocute the operator when touched.

[0031] Figure 1 illustrates the basic connection diagram of a device for remote monitoring during complete discontinuity of grounding system in the event of theft of copper and GI flats, in accordance with an embodiment of the present invention. The device comprising: a first contactor coil, a second contactor coil, a first indication lamp to indicate normal operation of the grounding system, and an audio-visual alarm to indicate disconnection of the grounding system. Where one end of said first contactor coil is electrically connected to Earth of an AC supply, and the other end of said first contactor is electrically connected to Neutral of said AC supply; and where one end of said second contactor coil is electrically connected in series to NC contact of said first contactor coil, and the other end of said second contactor coil is electrically connected to the Neutral of said AC supply. Each of the first and second contactor coils are 230V AC contactor coils, and each of said first indication lamp and said audio-visual alarm are operatively coupled to the other end of said second contactor coil; and wherein said audio-visual alarm comprises of a second indication lamp operatively coupled to an audio alarm device. The audio alarm device is a very high frequency (VHF) alarm device.

[0032] For the second abnormal situation i.e., high resistance for the grounding system due to rusting or deposition of sulphate at the joints in the connection to the earth pit, two Isolating Current Transformers (ICTs) of the ratio 1:100 are connected at the two earth pits. The output of the two ICTs are passed through a Summation Current Transformer (CT), whose output is fed to a relay as input. Using the under current sensor function for the relay and applying proper setting to the relay, an alarm will be sent to the remote centre via VHF alarm when the measured under current falls below 50% of the actual average leakage current at the earth pits, measured experimentally before. After sounding the alarm subsequent rectification job needs to be carried out over there. The schematic diagram for this arrangement has been provided later.

[0033] Figure 2 illustrates the basic connection diagram of a device for remote monitoring during high resistance for the grounding system in the event of rusting or deposition of sulphate at the joints in the connection to the earth pit, in accordance with another embodiment of the present invention. The device comprising: a first interconnecting transformer, a second interconnecting transformer, a current transformer, an undercurrent sensor relay, and an audio-visual alarm to indicate high resistance at the grounding system. Where one end of said current transformer is electrically connected to said first interconnecting transformer, and the other end of said current transformer is electrically connected to said second interconnecting transformer; and where said current transformer is operatively coupled to the relay. The ratio between the first and second interconnecting transformers is 1:100. The audio-visual alarm is operatively coupled to the relay; and wherein said audio-visual alarm comprises of a second indication lamp operatively coupled to an audio alarm device. The audio alarm device is a very high frequency (VHF) alarm device. The current transformer is a summation current transformer. The audio-visual alarm is activated, when the under current detected at the relay is below 50% of actual average leakage current at the earth pits of the grounding system.

[0034] The present invention finds its application in unmanned distribution stations of the applicant. The technical effect offered by the present invention is that an economical solution to one of the most important but neglected issues associated with any power system i.e. system and equipment Earthing. The approximate cost for monitoring the system for a single equipment would be INR. 5000/- while the total cost incurred approximately for monitoring the health of grounding system for all the equipment in a power station would be about INR. 12000/-.

[0035] Some of the non-limiting advantages of the present invention are mentioned herein below:
a) Health of the most critical but neglected parameter of power system is continuously monitored;
b) By monitoring and taking care of the health of grounding system, equipment life is considerably enhanced;
c) Operator safety is guaranteed while operating the equipment;
d) The system is quite simple and maintenance free thereby avoiding additional costs associated with maintenance.

[0036] Although devices for online remote monitoring of a grounding system of a power station has been described in language specific to structural features and/or methods as indicated, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or components or devices or methods described therein. Rather, the specific features are disclosed as examples of implementations for detection of abnormal situations i.e., complete discontinuity of grounding system due to theft of copper and GI flats or high resistance for the grounding system due to rusting or deposition of sulphate at the joints in the connection to the earth pit.

Claims:
1. A device to remotely monitor disconnection of a grounding system, said device comprising:
a first contactor coil,
a second contactor coil,
a first indication lamp to indicate normal operation of the grounding system, and
an audio-visual alarm to indicate disconnection of the grounding system,
wherein one end of said first contactor coil is electrically connected to Earth of an AC supply, and the other end of said first contactor is electrically connected to Neutral of said AC supply; and
wherein one end of said second contactor coil is electrically connected in series to NC contact of said first contactor coil, and the other end of said second contactor coil is electrically connected to the Neutral of said AC supply.

2. The device as claimed in claim 1, wherein each of the first and second contactor coils are 230V AC contactor coils.

3. The device as claimed in claim 1, wherein each of said first indication lamp and said audio-visual alarm are operatively coupled to the other end of said second contactor coil; and wherein said audio-visual alarm comprises of a second indication lamp operatively coupled to an audio alarm device.

4. The device as claimed in claim 3, wherein the audio alarm device is a very high frequency (VHF) alarm device.

5. A device to remotely monitor high resistance at a grounding system, said device comprising:
a first interconnecting transformer,
a second interconnecting transformer,
a current transformer,
an undercurrent sensor relay, and
an audio-visual alarm to indicate high resistance at the grounding system,
wherein one end of said current transformer is electrically connected to said first interconnecting transformer, and the other end of said current transformer is electrically connected to said second interconnecting transformer; and
wherein said current transformer is operatively coupled to the relay.

6. The device as claimed in claim 5, wherein ratio between the first and second interconnecting transformers is 1:100.

7. The device as claimed in claim 5, wherein said audio-visual alarm is operatively coupled to the relay; and wherein said audio-visual alarm comprises of a second indication lamp operatively coupled to an audio alarm device.

8. The device as claimed in claim 7, wherein said audio alarm device is a very high frequency (VHF) alarm device.

9. The device as claimed in claim 5, wherein said current transformer is a summation current transformer.

10. The device as claimed in claim 5, wherein the audio-visual alarm is activated, when the under current detected at the relay is below 50% of actual average leakage current at the earth pits of the grounding system.