Title of Invention

A METHOD FOR REALIZATION OF MULTIFUNCTION NUMERICAL LINE PROTECTION RELAY ADOPTING A REAL-TIME OPERATING SYSTEM AND A SINGLE PROCESSOR

Abstract

The method comprising segregating the various tasks into multiple threads for real time and non real time functions and prioritizing the various threads. Then to continuously perform the data acquisition and fault detection task scheduling is done using a unique method of switching between the various tasks depending on the criticality of the function, and issue a trip command to the field breaker at the earliest in order to isolate the fault section. After that communication is made with other devices for measured and processed data, event, fault and disturbance records and relay switch settings, wherein the protection features being Phase to ground fault, Phase to phase fault, Directional / Non-directional three phase over-current and earth-fault, negative sequence over-current, over/under voltage, circuit breaker failure protection, broken conductor detection, switch onto fault, trip on reclose, voltage and current transformer supervision, and wherein the non- protection features being autorecloser with check synchronism for phase, frequency and voltage, event / fault / disturbance records, distance to fault locator, circuit breaker condition monitoring and the data is shared for communication with other serial devices.

Full Text

FIELD OF INVENTION The invention relates to a method for realization of multifunction numerical line protection relay adopting a real-time operating system and a single processor. BACKGROUND OF THE INVENTION Transmission system is undergoing radical changes due to the introduction of numerical relays, SCADA and advance communication systems as a part of the substation automation. Numerical relays play an important role in the protection, control and monitoring of the transmission lines. Protective relaying is a vital part of any power system - quite unnecessary during normal operation, but very important during faults and abnormal disturbances. Properly applied protective relaying initiates the isolation of the faulty section, while operation and service in the rest of the system continue. Present power system is a complex network comprising of various power plants interconnected through transmission lines in a grid meeting the growing needs of industries. Conventionally, transmission lines are protected by electromechanical and electronic relaying systems which monitor the analog voltages and currents through various lines, via isolation transformers, for the purpose of detecting out-of-tolerance operating conditions. Such systems, receive and process the field data and achieve system reliability by having at least one independent protective relay dedicated to the protection of a single transmission line. This one-to-one correspondence between the protection hardware and the protectable equipment, when considering the many transmission lines of a large system to be protected, although ensures high reliability, but leads to a high cost protection system. The growing complexity of network in the transmission lines, lead to complicated phenomena of system faults. Thus, it is essential to achieve an optimization of various protection functions including a highly graded protective performance along with high speed and greater accuracy in order to isolate the faulty section from the rest.Such a requirement entails high-speed processing of large amount of data by adopting several algorithms . Large amount of data also needs to be shared on the network. In order to achieve a superior protective performance, higher speed and greater accuracy, the processing functions need to be graded and prioritized suitably. In general, numerical line protection relays are well known. In recent years, a digital relay has been developed as a protective relay for a power system to process voltage and current signal data, sampled at regular time intervals to detect a system fault and thus to protect the system. A few related examples can be found in the earlier patents mentioned below: 1) US PATENT NO.5428553 Dt. June 27,1995 Title : DIGITAL CONTROL AND PROTECTION EQUIPMENT FOR POWER SYSTEM In accordance with this invention, a power signal processing system and a related system is based on a multiprocessor system, with processing means optimally distributed into a plurality of units according to respective processing functions. A power signal processing system and method for protection of a power system has a signal input unit for receiving a signal representing a condition of a power system; a plurality of processing units cooperating to apply to the received signal a predetermined process including a series of predetermined different computations thereby producing a control signal for controlling operation of the power signal processing system. The respective processing units operate to perform the predetermined different computations, respectively. A control unit is provided for controlling transfer of data among the processing units so that the different computations are applied, successively, to the received signal thereby producing the control signal which is used to cause, for example, the issue of a cut-off command to a circuit breaker. The drawback of this invention is that several digital signal processing units are required, thereby making the system costly as well as robust. 2. KOREAN PATENT NO. KR20020031066 Dt. April 26,2002 TITLE : SEPARATION OF PROTECTION AND AUTOMATION FUNCTIONS IN PROTECTIVE RELAY FOR POWER SYSTEMS This invention relates generally to protection and automation control functions for power systems, and more particularly concerns a system for providing separation between the protection and automation functions in a single apparatus. Separation of protection and automation functions in a protective relay for power systems is provided to achieve a single system for both protection and automation control, while maintaining the autonomy and separation between the specific control portions of the protection and automation functions. This invention discusses about having a single system for both protection and automation control, while maintaining the autonomy and separation between the specific control portions (logic equations) of the protection and automation functions, as well as separate output contact control in some cases. While the protection logic equations can be modified by a user having first password, the automation logic equations can be modified by another user having access to the second password. Here, the disadvantage is that the user is allowed to tamper with protection logic equations along with the automation logic equations. In the case of protection relays with high complexity of protection logic built into it for failsafe operation, it is not advisable to let user change the protection logic. 3. US PATENT NO. US6789001Dt. Sep 7,2004 TITLE : DIGITAL MULTIFUNCTION RELAY This invention relates to a digital multifunction relay having a digital signal processor in conjunction with a microcontroller for controlling one or more protection devices of a power distribution network from fault events. The foreground activity of the digital signal processor is to convert the analog signals into sampled values and processing said sampled values to obtain predefined calculated values suitable for controlling said protection devices; and generating control signals which regulate an operating state of said protection devices. The foreground and background activity is controlled by the microcontroller. 4. US PATENT NO.5,224,011 Dt. Jun.29, 1993 TITLE : MULTIFUNCTION PROTECTIVE RELAY SYSTEM This invention is about the relay system which includes a dual processing architecture wherein a digital signal processor executes all the signal- processing algorithms, and a separate microprocessor is used for input/output data processing. A dual-ported RAM is used to effect a fast communication link between the digital signal processor and the microprocessor to accomplish high-speed protective relaying functions to selectively trip and close a circuit breaker at a generator or cogenerator site, or that which connects it to an electric utility system. The limitation of the methodology discussed in 1,2,3,4 is that all of them are based on more than one processor, either a DSP with a microcontroller / microprocessor or with several DSPs together. 5. US PATENT NO.4,636,909 Dt. Janl3, 1987 TITLE : DIGITAL IMPEDANCE RELAY This invention relates to a device for digitally detecting an impedance below a set value. The incoming voltage and current signals are converted in a A/D converter, filtered and rectified to deliver an output signal via summators when the measured impedance is lower than the set impedance value. The method discussed here is about a single parameter - distance measurement as a basis for identification of fault, which is a limitation in the present scenario of complex networks. 6. US PATENT NO. 4,689,709 Dt. Aug 25, 1987 TITLE: DIGITAL DISTANCE RELAY The invention relates to a digital distance relay which requires only 2N (N: number of phases on duty) per sampling of distance measuring operations. Here, the distance measuring operation is performed only regarding the phase on duty in third step, if there is no fault, and it is performed regarding either the third and first steps or the third and second steps, if a fault is detected within third step. Thereby the processing time for the distance measuring operation is reduced to two steps per sampling. The method discussed here is about a single parameter - distance measurement as a basis for identification of fault, which is a limitation in the present scenario of complex networks. 7. US PATENT NO. 4,344,143 Dt. Aug 10,1982 TITLE: DIGITAL TYPE DISTANCE RELAY SYSTEM This invention relates to a digital distance relay system, which can reliably determine whether or not to protect the power transmission system at the time of occurrence of a fault in the power system. It caters to a single protection function of line protection. The limitation of the methodologies discussed in 5,6,7 is that it is difficult to meet the present day demands on a multifunction line protection relay to not only detect a fault based on impedance parameter alone, but also perform several other protection functions before deciding on the operation of the breaker. 8. JP PATENT NO. 1077415 Dt. March 23, 1989 TITLE: DIGITAL PROTECTING RELAY This invention relates a method to obtain multifunction protective relay unlimited by the scale of a function, by increasing the number of CPU units according to the scale of the function. Here too, the methodology is to increase the number of CPU units as the complexity rises, which would ultimately increase the size of the unit. Thus, a conventional digital relay consists of a Central Processing Unit (CPU) and the associated digital circuitry, where one or several functions are performed in time division multiplexing mode. In this type of relay, the limitation is in the processing ability of the processing section which may not be able to meet the enormous data processing requirements. In order to circumvent the above mentioned problem, several relays are being proposed with two or more processors, thereby segregating the processing load and attempt to meet the high speed performance. In some cases, while the data acquisition is managed by a Digital Signal Processor (DSP), the rest of the protection and control functions are being managed by a microcontroller or a microprocessor or a DSP. The limitation of this method is that the main processor is made to handle both the protection and control functions, and also slow processes such as serial communication over RS232 and MODBUS communications over RS485, thereby loading the processor. Increasing demands upon protection relays for higher level services like high speed and accurate protection along with networking, user interfaces and file system management, are driving growth in fully-featured configuration. A critical issue is efficient integration of custom hardware and software resources, where efficiency must be considered in terms of both design time and run time. The prior art available does not answer this issue. OBJECTS OF THE INVENTION It is therefore, an object of the invention to provide a single processor architecture with a real-time operating system that is designed for scheduling the multiple tasks in order to protect the transmission line by means of a multifunction numerical line protection relay, so as to achieve a significant increase in the processing capability. Another object of the invention is to provide a method for line fault detection by adopting a numerical line protection relay which provides task scheduling and prioritizing the tasks for the protection and control. A further object of the invention is to provide a method for transmission line fault detection by adopting a multifunction numerical line protection relay based on determination of current and voltage parameters in a single central processing unit (CPU) in combination with a real time operating system, thereby eliminating the need of using dual processor with / without Digital Signal Processor (DSP). Still another object of the invention is to provide a method for line fault detection by adopting a multifunction numerical line protection relay which is cost-effective and functionally reliable. SUMMARY OF THE INVENTION The invention proposes a unique method to schedule several tasks to achieve optimum usage of processor resources with memory management for data sharing. More particularly, the invention relates to a method for transmission line protection by means of a multifunction numerical line protection relay. The present invention relates to a method used in multifunction numerical line protection relays, based on a single processor system with the processing load optimally distributed into several threads and tasks and prioritizing the various functions to accommodate protection and control functions of the relay. The protection features are Phase to ground fault, Phase to phase fault, Directional / Non-directional three phase over-current and earth-fault, negative sequence over-current, over/under voltage, circuit breaker failure protection, broken conductor detection, switch onto fault, trip on reclose, voltage and current transformer supervision. The non-protection features are autorecloser with check synchronism for phase, frequency and voltage, event / fault / disturbance records, distance to fault locator, circuit breaker condition monitoring etc. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.1 shows a Multifunction Numerical Line Protection Relay connected in a protective arrangement with an electrical system; Fig. 2 depicts the block diagram of the relay hardware; Fig. 3 illustrates the overall design of the relay software; Fig. 4 illustrates the Data Flow Diagram of the relay (real time) software; Fig. 5 illustrates the Data Flow Diagram of the relay (non-real time) software; Fig. 6 shows the oscilloscope record of the RTThreadl swtiching time; Fig. 7 shows the oscilloscope record of the RTThread2 switching time; Fig. 8 shows the timing and synchronization between the three RTThreads; Fig. 9 Waking up of RTThread2 by the signal from RTThreadl; Fig. 10 The procedural design of the RT module with the three real time threads; Fig. 11 Procedural flowcharts of RTThreadl, RTThread2 and RTThread3; DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION Referring now to Fig.l, the multifunction numerical line protection relay incorporating the present invention, is a powerful and compact multifunction numerical relay, configured for the protection of transmission lines. The relay is capable of handling the protection requirements of the transmission lines, and works based on the three phase currents and voltages. The entire application software is divided into real and non-real time tasks wherein the real time tasks are repeated exactly with the same cyclicity as has been originally defined by the application. The non-real tasks on the other hand, are not time critical and run in the background. The real time tasks are handled by the RT module while the non-real time tasks are handled by NRT module. The relay software is designed and implemented such that it supports many features. It uses RT FIFOs (real time first in first out) as Inter Process Communication (IPC) mechanism for communication between RT module and NRT module and it lies in kernel memory space. They act as pipes between the RT and NRT tasks. As relay software needs to keep on sampling voltages and currents periodically, using a real time operating system is very advantageous. It provides system calls to schedule the execution of our code to a precision of few tenths of micro seconds. And the RT programs are inserted into the kernel, like other kernel modules, while they are executed, so even direct access to hardware is also possible. This will increase the performance of the software. Another advantage is that the programs can be multithreaded so that the protection functions are executed periodically without interruption even while communicating with external interfaces, eg. changing the setting through serial link which is usually slow. It is not possible without the multithreading feature. Also operating system uses dual kernel technology making it possible to execute both real time programs and non-real time programs on the same microprocessor. It also provides good Inter Process Communication (IPC) mechanisms between real time programs and non- real time programs. The multifunction line protection relay of the invention is configured to perform the following protection and non protection functions : PROTECTION FEATURES 1. Phase and earthfault distance protection: Each with five independent zones of protection, four in the forward and one in the reverse direction. This is based on impedance measurement, which is high during the normal operation, and, during fault condition, the impedance becomes less, and when it is below the set value, trip command to the breaker is issued to isolate the faulty time. 2. Overcurrent protection: Two elements with direction control, with first element as either Inverse Definite Minimum Time (IDMT) or Definite Time (DT) and the second element as Hiset instantaneous. This is provided to limit damage from phase faults. 3. Earthfault protection: Two elements with directional control, with first element as either Inverse Definite Minimum Time (IDMT) or Definite Time (DT) and the second element as Hiset instantaneous. This is a protection scheme with the zero sequence component of the three phase currents. 4. Overvoltage protection: One element with selectable characteristics as either Inverse Definite Minimum Time (IDMT) or definite time (DT) for each of the three phase voltages. 5. Undervoltage protection: One element with selectable characteristics as either Inverse Definite Minimum Time (IDMT) or definite time (DT) for each of three phase voltages. 6. Negative sequence overcurrent protection. This element can provide backup protection for many unbalanced fault conditions. 7. Switch on to fault (SOTF) protection: This is provided for high speed clearance of any detected fault immediately after a manual circuit breaker closure. 8. Trip on reclose protection (TOR): This is provided for high speed clearance of any detected fault immediately following autoreclose of the circuit breaker. 9. Power swing blocking: Selective blocking of distance protection zones ensures stability during power swings experienced on transmission systems. 10. Voltage transformer supervision: This is to prevent wrong operation of voltage dependent protection on AC voltage input. It mainly detects voltage transformer fuse failures. 11. Current transformer supervision: If one or any of the current transformers were to become open circuited, this protection raises an alarm. 12. Broken conductor: This is to detect network faults such as open circuits, where a conductor may be disconnected and not in contact with another conductor or the earth. 13. Circuit breaker failure protection: Whenever the circuit breaker at protected terminal fails to trip, this protection would then send a command to upstream circuit breaker to backtrip. NON-PROTECTION FEATURES 1. Autorecloser with checksynchronism: This provides upto 4 reclose shots, with checksynchronism for voltage, frequency and phase, and can be set for any combination of line and bus conditions. 2. Distance to fault locator. 3. Measurements of field data and computation of derived parameters are available for display at the relay as well as accessed from the serial communication facility. 4. Event / Fault / Disturbance Records. The program continuously monitors to determine the status of the associated transmission line, in real time. This provides information related to the line conditions and whether any alarms or trips are issued by the relay. Fig. 1 shows the relay connected to the transmission line for monitoring the current and voltages in real-time. The field inputs viz. three phase currents, the three phase voltages and the busbar voltage are connected to the relay terminal blocks. The relay contacts operate the circuit breaker (52), which is connected to the relay terminal blocks. Fig.2 shows a block diagram of the hardware of the system. The relay hardware comprises of seven modules. The auxiliary D.C. voltage given to the relay is first stepped down to 24Vdc in module no. 1. This voltage energizes module no. 2, module no. 5 and module no. 7. The +15Vdc and -15Vdc is used to energize module no. 3 and module no. 4. The field inputs viz. three phase currents and the three phase voltages (described in Fig.l ), connected to the relay terminal blocks, are first processed by module no. 3. The stepped down signals are then filtered by module no. 4 for any high frequency disturbances and anti-aliasing errors. These signals are then sent to section B of module no. 2. The module no. 2 has the relay algorithm residing in section C. When the module is powered ON, the program control after necessary hardware and software memory initializations, first digitizes the analog data in section B, and processes the data checking for any fault. When a fault occurs, the relay senses it and issues a command in the form an annunciation or a trip, depending upon the severity of the fault. The final relay outputs are sent through section D to the module no. 5. This module with its sixteen numbers of contacts has a higher driving capability and these potential free contacts are brought out to relay terminal blocks (described in Fig. 1). Relay status is indicated by means of lamps provided on the front side of the panel. In addition, alarms and trip contacts are brought out in the form of potential-free contacts, which can, in turn, be used for either operating the circuit breaker or to drive audio / visual alarm. The contacts and lamps are of self resetting type. The module no.2 also has two serial ports RS232- section F, through which the metered data is communicated to the operator interface on the front of the relay (module 7) and also to the PC-based HMI (Human machine interface) program (module 6). It can also read the set parameters from the operator interface. The section G comprises of two RS485 ports which facilitates the multi drop communication features of the relay when using MODBUS protocol. The section E is the 100 Mbps Ethernet port that is available on the relay for communication over Ethernet. FUNCTION OF THE RT AND NRT MODULES AND THEIR INTECONNECTIVITY The present invention incorporates the concept of multithreading used in the relay and is described in Fig.3, Fig.4 and Fig.5. Both the real time tasks as well as the non-real time tasks are handled by the relay software and the communication between them is through RT FIFOs. Description of Fig. 3: This figure describes the overall design of the relay software by means of a Data Flow Diagram. The RT module handles real time operations regarding data acquisition through A/D interrupts for analog signals, and also the digital signals, processes them and handles control of the circuit breaker and other digital controls. The data that needs to be shared with the NRT module is placed in the memory (RT FIFOs) that can be accessed by the NRT module. The NRT module handles the serial communications with the environment, stores the data made available by the RT module in data files. It handles the metering data, event, fault, disturbance, oscillography data and the relay switch settings data. Description of Fig. 4: This figure illustrates the various real time threads by means of the data flow diagram. There are three threads, viz. RTthreadl, RTthread2, RTthread3. RTthreadl has the highest priority and is programmed to wake up every 277 microseconds. On waking up, this thread completes the tasks and goes to sleep. RTthread2 which has the next lower priority level, is programmed to wake up every 833 microseconds (three times that of RTthreadl). RTthread3 has the least priority and scheduled to be executed every 1 second. This thread gets to be active only when the other tasks in the higher two threads are completed, and the processor is idle. The load in each of the thread is distributed in such a way that all the tasks are executed in a easy manner without any loss of data. The rate of sampling as done by the RTthreadl is 3600 samples per second. This is very much essential for accurate fault identification, location, proper regeneration of the waveform when oscillography / disturbance recording is considered and for the computation of the derived parameters. But for performing the protection functions, this high rate of periodicity is not necessary. If even the protection is done at this high rate the burden on the processor will increase unnecessarily. So it is better to run the protection functions at a slower rate i.e. in the second thread. The RT thread2 runs periodically 1200 times a second, and calls the protection functions with the same rate. This is exactly l/3rd of the rate of sampling done at the RT thread 1. The RT thread 1 is the highest priority thread. And this thread runs periodically once in every 277 microseconds. The tasks in this thread which sample all the seven input signals ie. three voltages, three currents and the busbar voltage from the field. The second thread, RTthread2, calls all the functions needed for the protection and other algorithms. Other derived parameters viz. the frequency of the signal, impedances of each phase, active power and reactive power, phase angles between the currents and voltages etc. are also calculated here and used in the algorithms. The third thread, RT thread 3, is used for properly communicating with the NRT module through FIFOs. It sends the metering data to the NRT module once in every 1 second. Reading from and writing to the RT-FIFOs is completely taken care of, by this thread. As explained before, the relay settings are also brought to RT module form the NRT module via an RT FIFO dedicated for this purpose. The records of data for the events, faults and disturbances are also updated in the respective RT FIFOs. The scheduling time and synchronization of the three threads is shown in the Fig. 8. Description of Fig. 5: This diagram depicts the data flow in the NRT software. The data accessed from the shared memory i.e. through RTFIFOs is managed by the NRT module. The front-panel display and keypad functions are handled through the serial port. These functions include - the data to be displayed (viz. metering, event, fault, disturbance records) and the data to be read and updated during the modification of the relay switch settings. Similarly, the PC based GUI software can be accessed over another serial port. Other devices and relays can also be connected to the RS485 ports for multidrop communication. All these tasks are slow and are handled by the NRT thread which is not time critical and gets executed during the idle time of the processor. Fig. 6 and 7 show the recording of the RTThreadl, RTThread2 switching time. The logic 'high' of each of waveform depicts the thread busy time. Fig. 8 shows the timing and synchronization between the three threads. Fig. 9 is the record showing the waking up of RTThread2 by the signal from RTThreadl. DESCRIPTION OF THE FLOWCHARTS Fig. 10 shows the procedural design of the RT module with the three real time threads. Step 1: When powered ON, the program first initializes the operating system. Step 2: Next is the initialization of all the memory variables of section C in Fig.2, and the A/D - section B of Fig.2. Step 3: Creation of the real time threads takes place here. Step 4: This is an event loop handler that allows the program to suspend until it receives an exit signal from the user or system. Step 5: Here, the cancellation and joining of threads take place. Step 6: Before the application is terminated, all the initialized memory and RTFIFOs are released. Step 7: Termination of the application program. Step 8: Waking up of RTThreadl for the execution of the tasks. Upon completion, it goes to sleep. Step 9: When RTthreadl goes to sleep and the timer for this thread gets activated, RTThread2 wakes up to execute the tasks assigned. Upon completion, it goes to sleep. Step 10: RTThread3 wakes up every 1 second to perform the tasks assigned to this thread. If any of the higher priority tasks viz. RTThreadl or the RTThread2 wakes up, it will preempt the task, switch to the higher priority thread, finish the tasks and resume from where it left. Upon finishing the tasks, this thread would go to sleep. Fig. 11 shows the procedural flowcharts of RTThreadl, RTThread2 and RTThread3 Step 1 shows the waking up and beginning of RTThreadl. Step 2 shows the functions performed by RTThreadl. The data acquisition, digital filtering routine, computation of metered and derived parameters and storing of data for records is done here. Step 3 is the termination and going to sleep of RTThreadl. Step 4 shows the waking up and beginning of RTThread2. Step 5 shows the functions performed by RTThread2. The protection algorithms for the various functions are processed here. The circuit breaker control is also performed here. Step 6 shows the non-protection algorithms being processed by RThread2. Step 7 is the termination and going to sleep of RTThread2. Step 8 shows the waking up and beginning of RTThreacB. Step 9 shows the functions performed by RTThread3. The writing of the RTFIFOs with measurement values, event, fault and disturbance records, and reading of the RTFIFO for the updated switch settings and relay parameters is executed here. Step 10 is the termination and going to sleep of RTThread3. WE CLAIM 1. A method for realization of multifunction numerical line protection relay adopting a real-time operating system and a single processor, the said multifunction numerical line protection relay comprising; - a power supply module [1] providing overload, short circuit and input reversal protections; a microprocessor [A] based module [2] having in-built digital input, analog input, digital output [D], analog output, a static memory [C] and flash memory, two serial RS232 ports [F], 2 serial RS485 ports [G] for multidrop communications, one Ethernet port [E]; a relay algorithm incorporated in the microprocessor based module; a powerful real time and compact operating system; characterized in that the method of fault detection by the relay comprising steps of; i) segregating the various tasks into multiple threads for real time and non real time and non real time functions; ii) prioritizing the various threads; iii) task scheduling to continuously perform the data acquisition and fault detection; iv) communication facility with other devices for - measured and processed data, event , fault and disturbance records and relay switch settings. v) The protection features are Phase to ground fault, Phase to phase fault, Directional / Non-directional Three phase over-current and earth-fault, negative sequence over-current, over/under voltage, circuit breaker failure protection, broken conductor detection, switch onto fault, trip on reclose, voltage and current transformer supervision. vi) The non-protection features are autorecloser with check synchronism for phase, frequency and voltage, event / fault / disturbance records, distance to fault locator, circuit breaker condition monitoring etc. - sharing of data for communication with other serial devices [6] and [7]; - a voltage and current transducer module [3] having four voltage transformers, three current transducer module [3] having four voltage transformers, three current transformer for stepping down field voltages and currents respectively; - a seven channel, second order filters [4] for correction of amplitude and phase of the analog signals, and a relay module [5] comprising of plurality of relays, to open or close the breaker upon fault detection or reclose condition. A method to provide a multifunction numerical line protection relay for transmission line fault detection, using a single microprocessor and a real time operating system, as substantially herein described and illustrated with reference to the accompanying drawings. ABSTRACT A METHOD FOR REALIZATION OF MULTIFUNCTION NUMERICAL LINE PROTECTION RELAY ADOPTING A REAL-TIME OPERATING SYSTEM AND A SINGLE PROCESSOR The method comprising segregating the various tasks into multiple threads for real time and non real time functions and prioritizing the various threads. Then to continuously perform the data acquisition and fault detection task scheduling is done using a unique method of switching between the various tasks depending on the criticality of the function, and issue a trip command to the field breaker at the earliest in order to isolate the fault section. After that communication is made with other devices for measured and processed data, event, fault and disturbance records and relay switch settings, wherein the protection features being Phase to ground fault, Phase to phase fault, Directional / Non-directional three phase over-current and earth-fault, negative sequence over-current, over/under voltage, circuit breaker failure protection, broken conductor detection, switch onto fault, trip on reclose, voltage and current transformer supervision, and wherein the non- protection features being autorecloser with check synchronism for phase, frequency and voltage, event / fault / disturbance records, distance to fault locator, circuit breaker condition monitoring and the data is shared for communication with other serial devices.

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00575-kol-2007-claims.pdf

00575-kol-2007-correspondence others 1.1.pdf

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00575-kol-2007-description complete.pdf

00575-kol-2007-drawings.pdf

00575-kol-2007-form 1.pdf

00575-kol-2007-form 18.pdf

00575-kol-2007-form 2.pdf

00575-kol-2007-form 3.pdf

00575-kol-2007-gpa.pdf

575 KOL 2007 Final Search Report.pdf

575-KOL-2007-(03-01-2012)-ABSTRACT.pdf

575-KOL-2007-(03-01-2012)-AMANDED CLAIMS.pdf

575-KOL-2007-(03-01-2012)-DESCRIPTION (COMPLETE).pdf

575-KOL-2007-(03-01-2012)-DRAWINGS.pdf

575-KOL-2007-(03-01-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

575-KOL-2007-(03-01-2012)-FORM-1.pdf

575-KOL-2007-(03-01-2012)-FORM-2.pdf

575-KOL-2007-(03-01-2012)-OTHERS.pdf

575-kol-2007-CANCELLED PAGES.pdf

575-KOL-2007-CORRESPONDENCE 1.1.pdf

575-kol-2007-CORRESPONDENCE 1.2.pdf

575-kol-2007-EXAMINATION REPORT.pdf

575-kol-2007-FORM 18.pdf

575-kol-2007-GPA.pdf

575-kol-2007-GRANTED-ABSTRACT.pdf

575-kol-2007-GRANTED-CLAIMS.pdf

575-kol-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

575-kol-2007-GRANTED-DRAWINGS.pdf

575-kol-2007-GRANTED-FORM 1.pdf

575-kol-2007-GRANTED-FORM 2.pdf

575-kol-2007-GRANTED-FORM 3.pdf

575-kol-2007-GRANTED-SPECIFICATION-COMPLETE.pdf

575-kol-2007-OTHERS.pdf

575-kol-2007-REPLY TO EXAMINATION REPORT.pdf