DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to a protection relay, and more particularly to an electronic circuit in the protection relay for detecting overvoltage faults and thereby protecting an electrical power system.

BACKGROUND

[002] Electrical power systems are used for transmission and distribution of power to electrical loads. In order to protect the major components of the electrical power system, protection relays are used which provides protection against overvoltage, overcurrent, overload, phase loss, temperature rise and other such detrimental effects which cause damage or failure of the electrical power system. For example, Motor protection relays (MPR) are used only for motor protection and to protect motor and increased of motor life. MPR provides all the protection related to motor. Same as motor, transformer protection relay which provide the transformer related protection, variable-frequency drive’s (VFD) are used for motion control and protection of motor, soft starter used for initial soft start of the motor, harmonic filter used for the harmonic reduction of power system.

[003] Currently, this protection is provided through software program. When CPU energizes and operates the program and then calculates the current and detects faults. Then it gives the faults of protections taking defined time by CPU programmer. In that particular time power source supply is reached at device or machine. It may decrease the life of the devices or machine. Sometimes, it may also create the severe damages to the devices or machines.

[004] In the power supply circuit, overvoltage fault occurs frequently. In the event of an overvoltage fault when the voltage exceeds the maximum withstand voltage, if timely protective measures are not taken some of the equipment may damage resulting in huge losses of the electrical power system. Overvoltage protection relay is used to reduce the losses caused in such events by promptly disconnecting the power supply circuit and thereby terminating further supply of power to electrical loads.

[005] Microprocessor based overvoltage relay and other equipment (like switch gear, relays VFD, MVD, soft starter, and harmonic filter, and the like) as mentioned above is well known in the art. The microprocessor uses a memory to store a preset value and time-current characteristics curves. Such microprocessor relay uses software programs or algorithms for detecting faults. The microprocessor converts the monitored voltage to a digital value and compares the digital value against a selected preset value. When the digital value exceeds the selected preset value, a connected circuit breaker or equipments are tripped. It gives a fault indication after taking definite time by the processor. However in that particular time, power source supply may reaches the device or machine, decreasing the life of device or machine and thereby causing severe damages.

[006] Some existing overvoltage protection circuits also include the use of metal oxide varistor (MOV), an electrical component for protecting a device against high voltage conditions. MOVs however degrade over time and sometimes fail by creating a partial or complete short circuit and causing damage to the circuit being protected. Another overvoltage protection device used is the thyristor surge protection device (TSPD) which is a solid-state electronic device typically used in crowbar protection circuits. Still another device used in protecting against overvoltage conditions is a silicon avalanche diode (SAD). SADs provide fairly fast limiting action of protection, but have very low energy absorbing capability, so are not useful in a lot of applications.

[007] The prior art document US 20120002332Al, wherein an overvoltage circuit is disclosed which includes a voltage reference having a voltage, a comparator, analog to digital convertor (ADC) and a switch as a part of a processor which protects a load connected in the circuit by cutting off a power supply when whenever the voltage of the power supply exceeds a threshold voltage.

[008] The prior art document US 20130250464 A, wherein a method and circuit for detecting and providing protection against an overvoltage condition is disclosed. The overvoltage detection circuit uses an opto-isolator component to generate an overvoltage condition signal to drive a protection relay in case of an overvoltage fault. However opto-isolators have limitations and cannot be used in all electrical systems. Also, high humidity may negatively affect opto-isolators as it causes electricity to arc and subsequently causing internal arc fault in the circuit.

[009] The existing hitherto techniques for detection of overvoltage faults in a device using software model are complex, much costlier, and require extra man power for their operation and maintenance.

[0010] Thus, in view of the above mentioned drawbacks, there exists a need for providing an overvoltage circuit that eliminates the requirements of software simulation to drive the operation of a protection relay and that is simple to construct, inexpensive, and thereby obtain more accurate results making the protection relay more robust.

SUMMARY OF THE INVENTION

[0011] 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.

[0012] An object of the present invention is to provide a simple and compact overvoltage detection circuit in protection relay devices in order to improve the design of the existing protection relay and thereby making devices more robust.

[0013] Another object of the present invention is to provide an alternative solution which is non-existent today to obviate the problems of the microprocessor based protection relays.

[0014] Yet another object of the present invention is to improve the design and make robust protection relays product, by providing the hardware protection and detection of the over voltage.

[0015] Accordingly, the present invention provides an overvoltage detection circuit in a protection relay for protecting an electrical power system. The overvoltage circuit essentially detects faults due to overvoltage in the electrical power system using simple electrical components and thereby eliminating the need of software models to drive the operation of protection relays.

[0016] In one implementation, voltage divider network divide the three phase voltage and given to the non-inverting amplifier to amplify the signal. Amplified signal is provided to summing amplifier to add the DC offset and generate the 0 to 3 voltage. This voltage is given to the ADC input for ADC Scan, and thereby it calculates the voltage based on the microprocessor program. At the same time amplified signal is given to the Full wave rectifier along with the amplifier to generate the full wave Rectifier signal. Now comparator circuitry compare the Rectifier signal along with user defined reference DC Voltage and give the High/Low output. In our case low output which is connected to the reset mechanism to trip the relays or other Equipment as mentioned above. This is for AC three phase.

[0017] In another implementation, the present invention is used for DC voltage measurement of equipment (especially VFD, MVD, Battery Charger, and the like). The voltage divider n/w is used to divide the l Voltage and given to the op amp to amplify the signal. The amplified signal is given to a comparator. The comparator circuitry then compares the amplified DC voltage signal with the user decided DC reference voltage to give the high/low signal as its output. If the voltage limit exceeds predefined range then it will give the low and according to the reset circuitry the device will be tripped.

[0018] In another implementation of the present invention, an overvoltage detection circuit comprises electrical components for detecting an analog input signal, amplification of the analog input signal, converting analog signal to digital signal and subsequently comparing a converted alternation current (AC) voltage signal to direct current (DC) voltage signal with preset reference value to determine a processed value.

[0019] In one implementation of the present invention the processed value from the overvoltage detection circuit is transmitted to a trip zone interrupt of a processor in a protection relay or equipment mentioned above to respond to a fault instantaneously and subsequently terminate the flow of a power supply.

[0020] In one implementation, the overvoltage circuit disclosed in the present invention provides protection against overvoltage faults in an electrical power system using internal simplified structures.

[0021] Conventionally, over voltage protection and detection are provided through software program in protection relays products. In addition to software program, we will add the hardware protection and detection of the over voltage. In current relays product, the voltage is measured through voltage divider network and gives it to the CPU. To give the measured voltage to ADC, the basic fundamental circuit of the operational amplifier to make 0 to 3V AC is used. ADC will sense the voltage and gives the count. Count will be used to get the actual voltage by deducting offset and adding gain in count. This actual voltage is used to detect the over voltage fault in software program means or any other detection means.

[0022] In addition to this, basic fundamental circuit will remain same the present invention adds a parallel circuit to provide the hardware protection of over voltage. To make the hardware protection, we have simulated the design for over voltage. Parallel circuit which full wave rectifier and Comparator circuitry. In case of AC voltage measurement, we use the Voltage divider N/W Circuit and divided voltage is given to the op amp. Op amp amplifies the voltage signal received and then gives it to the full wave rectifier to convert voltage signal into full wave rectified signal. Now comparator circuit compare the full wave rectified signal with user defined DC reference. If the Voltage limit for AC is exceeds the decide voltage trip limit it gives the high low signal. In our case it is low signal. According to the reset mechanism, unit will trip and also the comparator signal is given to the Trip zone of the Processor to trip the unit. In case of DC, the amplified signal is given to the Comparator circuit and comparator compares it with designer defined limit and gives the high/low output. In our case it is low and connected mechanism get tripped. Also it is given to the Trip zone of the processor to trip the unit instantaneously.

[0023] In one implementation, a system and method of an overvoltage detection (AC/DC) for any electrical/electronic and power electronics equipments like switch gear, relays VFD, MVD, soft starter, and harmonic filter, etc. are disclosed.

[0024] Accordingly, in one implementation, an overvoltage protection relay device to generate an over voltage fault is disclosed. The overvoltage protection relay device comprises at least one voltage divider network to measure a voltage passing through the overvoltage protection relay device; a processor configured to receive the voltage measured, amplify the voltage received, and transmit the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified and generate a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain. The overvoltage protection relay device achieves the technical advancement due to the presence of a detection circuit adapted to receive the voltage amplified and detect over voltage in the voltage amplified, wherein if the voltage amplified value is more than 2.85 V AC, a comparator circuit output generated is low and the detection circuit gives the over voltage fault.

[0025] In one implementation, a method for generating an over voltage fault, using an overvoltage protection relay device, is disclosed. The method comprises:
· measuring, by at least one voltage divider network, a voltage passing through the overvoltage protection relay device;
· receiving, by a processor, the voltage measured;
· amplifying, by the processor, the voltage received;
· transmitting, by the processor, the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified;
· generating, by the ADC, a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain;
· receiving, by a detection circuit, the voltage amplified;
· detecting, by the detection circuit, over voltage in the voltage amplified, wherein if the voltage amplified value is more than 2.85V AC, a comparator circuit output is low; and
· generating the over voltage fault.

[0026] 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

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:

[0027] Figure 1 illustrates a block diagram representation of an overvoltage detection circuit in a protection relay, in accordance with an embodiment of the present subject matter.

[0028] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0029] 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.

[0030] 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.

[0031] 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.

[0032] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0033] 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.

[0034] 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.

[0035] 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 components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0036] Figure 1 illustrates a block diagram of overvoltage detection circuit. A person skilled in the art will appreciate that for understanding purpose the present invention is explained with the help of protection relay however the disclosed method shall not be considered as the limiting factor for the scope of present invention.

[0037] Referring now to figure 1, in one implementation, the overvoltage detection circuit comprises a voltage divider network to measure an operating analog signal, a signal amplification circuit for amplifying the operating analog signal, an analog to digital (ADC) convertor for converting the operating signal amplified and an ADC scanner for detecting an event wherein the input voltage signal is beyond a threshold limit.

[0038] Referring now to figure 1, in one implementation, the ADC senses an input voltage and determines a count or digital voltage depending on a preset maximum and a minimum voltage and based on the count or digital voltage determined, the Processor determines an event if the input voltage exceeds the preset maximum voltage.

[0039] Referring now to figure 1, in one implementation, an event determined by an Processor, wherein the input voltage exceeds a preset maximum voltage, an additional circuit comprising full wave rectifier converts the amplified voltage to DC full wave rectified voltage and a comparator that compares the converted DC full wave rectified voltage signal with a preset DC reference voltage and thereby the comparator indicating overvoltage fault.

[0040] In one implementation, as shown in figure 1, the present invention starts from the block of Full wave rectifier and DC reference to comparator. Output of the comparator decides the over voltage. The software protection of the over voltage for both AC/DC voltage is provided. It senses the voltage and takes time to execute the software fault. In this particular time load or device connected to the protection device or other equipment as mentioned above may reduce life of equipment or create a severe damage. To overcome the limitation, hardware protection is given which immediately give the overvoltage fault by taking component internal time. However, this fast compare is performed with software fault. ADC scanning is well known in the art and most of the conventional products uses the same topology, however, giving the hardware protection through the same topology adding the hardware part is one of the essential aspect of the present invention.

[0041] Referring now to figure 1, in one implementation, a comparator indicates a high/low output to a trip zone interrupt of a processor to response to overvoltage faults and subsequently terminating the power supply.

[0042] In one implementation, the sensing voltage ranges from 0 to 3 AC. In one example, the minimum voltage is taken as 0 V and the maximum voltage is taken as 2.85 V AC. In one example, the ADC used is a 12 bit ADC that determines 4096 count in case of 2.85V AC and 0 count in case of 0V AC. In the event wherein a voltage increases beyond 2.85VAC (maximum voltage), the comparator output will go low and thereby giving an over voltage fault. The comparator high/low output is given to the Trip zone interrupt of a processor in a protection relay to immediately response of protection. The protection relays causes an electrical switching device to trip instantaneously.

[0043] In one implementation, in addition to the basic fundamental circuit the present invention enables to add the parallel circuit to provide the hardware protection of over voltage. In one example, to make the hardware protection, the design for over voltage is simulated.

[0044] In this simulation, the reference as before voltage sensing circuit means are taken into consideration as it should not be change in our new design. In new design, the present invention enables to take the sensing voltage 0 to 3 AC. With this sensing voltage, the present invention enables to make circuit which will detect over voltage of respective phase.

[0045] In parallel circuit, if 0V means minimum count and 2.85V AC means maximum count of ADC. Means suppose 12 bit ADC it takes 4096 count when 2.85V AC and 0 count when 0V AC. In one example, if the voltage increase 2.85 VAC then there is parallel circuit of hardware protection which will come in picture and comparator output will go low and gives the over voltage fault. The present invention may enable to trip the protection relays without waiting the software fault and protection.

[0046] In one implementation, the present invention provides the comparator that sends high/low output to the Trip zone interrupt of the processor to immediately response of protection and trip.

[0047] In one implementation, in the present invention provides the parallel circuit to all phase and take output of three comparator for single protection and trip the hardware as well as provide the hardware interrupt to the trip zone of the CPU.

[0048] Accordingly, in one implementation, an overvoltage protection relay device to generate an over voltage fault is disclosed. The overvoltage protection relay device comprises at least one voltage divider network to measure a voltage passing through the overvoltage protection relay device; a processor configured to receive the voltage measured, amplify the voltage received, and transmit the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified and generate a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain. The overvoltage protection relay device achieves the technical advancement due to the presence of a detection circuit adapted to receive the voltage amplified and detect over voltage in the voltage amplified, wherein if the voltage amplified value is more than 2.85 V AC, a comparator circuit output generated is low and the detection circuit gives the over voltage fault.

[0049] In one implementation, a method for generating an over voltage fault, using an overvoltage protection relay device, is disclosed. The method comprises:
· measuring, by at least one voltage divider network, a voltage passing through the overvoltage protection relay device;
· receiving, by a processor, the voltage measured;
· amplifying, by the processor, the voltage received;
· transmitting, by the processor, the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified;
· generating, by the ADC, a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain;
· receiving, by a detection circuit, the voltage amplified;
· detecting, by the detection circuit, over voltage in the voltage amplified, wherein if the voltage amplified value is more than 2.85V AC, a comparator circuit output is low; and
· generating the over voltage fault.

[0050] In one implementation, the detection circuit comprises at least on comparator circuit adapted to receive the voltage amplified and a pre-stored reference signal for comparison and thereby generate a output based on comparison, wherein if the output value of 2.85 V AC the detection circuit gives the over voltage fault.

[0051] In one implementation, the pre-stored reference signal is feed to the comparator circuit at the time of manufacturing and is re-configurable.

[0052] In one implementation, over voltage protection circuit is coupled to the comparator circuit, and is adapted to trip the overvoltage protection relay device if the voltage amplified value received from the comparator circuit is more than 2.85V AC.

[0053] In one implementation, the present invention discloses comprises a mechanism, preferably a software technique, configured to provide the over voltage fault based on the actual voltage of the count, and thereby tripping the overvoltage protection relay device.

[0054] In one implementation, the detection circuit is adapted to detect over voltage of respective phase.

[0055] In one implementation, the comparator circuit output i.e., high/low output to a trip unit interrupt of the processor for tripping.

[0056] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention provides a hardware overvoltage protection for protection relays as well other equipment as mentioned above.
2. The present invention provides an overvoltage detection circuit for switchgear devices which do not contain a processor, and thereby giving the hardware protection to such devices against faults due to overvoltage in an electrical power system.
3. The present invention provides a overvoltage circuit that provides protection to the components in a device against severe damage due to instantaneous cutting off power supply.
4. The present invention provides a protection relay that is more robust.
,CLAIMS:1. An overvoltage protection relay device to generate an over voltage fault, comprising:
at least one voltage divider network to measure a voltage passing through the overvoltage protection relay device;
a processor configured to receive the voltage measured, amplify the voltage received, and transmit the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified and generate a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain; wherein
the overvoltage protection relay device characterized in that comprises:
a detection circuit adapted to receive the voltage amplified and detect over voltage in the voltage amplified, wherein, a comparator circuit is adapted to compare the voltage amplified, specifically a voltage amplified value, with a fixed reference DC voltage, specifically a fixed reference DC voltage value, and thereby the detection circuit gives the over voltage fault based on the comparison.

2. The overvoltage protection relay device as claimed in claim 1, wherein, after comparing the voltage amplified with the fixed reference DC voltage, if the voltage amplified found more, the comparator circuit is adapted to generate a low signal.

3. The overvoltage protection relay device as claimed in claim 1, wherein the comparator circuit is adapted to receive the voltage amplified and the fixed reference dc voltage for comparison and thereby generate a output based on comparison, wherein if result of comparison is more than a threshold limit, preferably 2.85 V AC, the detection circuit gives the over voltage fault.

4. The overvoltage protection relay device as claimed in claim 3, wherein the fixed reference dc voltage (value) is feed to the comparator circuit at the time of manufacturing and is re-configurable.

5. The overvoltage protection relay device as claimed in claim 1, wherein over voltage protection circuit is coupled to the comparator circuit, and is adapted to trip the overvoltage protection relay device if the voltage amplified value received from the comparator circuit is more than 2.85V AC.

6. The overvoltage protection relay device as claimed in claim 1, comprises a mechanism, preferably a software technique, configured to provide the over voltage fault based on the actual voltage of the count, and thereby tripping the overvoltage protection relay device.

7. The overvoltage protection relay device as claimed in claim 1, wherein the detection circuit is adapted to detect over voltage of respective phase.

8. The overvoltage protection relay device as claimed in any of the preceding claims, wherein the comparator circuit output i.e., high/low output to a trip unit interrupt of the processor for tripping.

9. A method for generating an over voltage fault, using an overvoltage protection relay device, the method comprising:
measuring, by at least one voltage divider network, a voltage passing through the overvoltage protection relay device;
receiving, by a processor, the voltage measured;
amplifying, by the processor, the voltage received;
transmitting, by the processor, the voltage amplified to at least one analog to digital converter (ADC) to sense the voltage amplified;
generating, by the ADC, a count, the count provides an actual voltage by deducting offset from the voltage amplified and by adding gain;
receiving, by a detection circuit, the voltage amplified;
detecting, by the detection circuit, over voltage fault in the voltage amplified, by comparing the voltage amplified, specifically a voltage amplified value, with a fixed reference DC voltage, specifically a fixed reference DC voltage value; and
generating the over voltage fault, if the result of comparison is beyond a threshold limit.
10. The method as claimed in claim 8, comprises, tripping, overvoltage protection relay device, after the generating the over voltage fault.