Numerical Relays are basically Digital Relays for which manufacturers have developed specified hardware which can be used in conjunction with suitable Software o meet different protection needs. Numerical Relays are device in which measured electrical quantities are sequentially sampled and then converted into numerical data which are mathematically or logically processed to take decision for issuing trip command. Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. Hardware for Metering: In principle, the hardware setup discussed above can be used for both measurement and protection function. For simplicity on one-line diagrams, the protection function is usually identified by an ANSI device number. Suppose if it happens to be the number of disturbances exceeds 50 then the Relay will delete the last Disturbance and will register new disturbance. -Working & Types of UPS Explained. [3] He published his seminal paper Fault Protection with a Digital Computer [4] in 1969. One is RAM (Random Access Memory) and ROM (Read Only Memory). The relay analyzes the resultant A/D converter outputs to determine if action is required under its protection algorithm(s). CPU 3. Memory 4. Any one numeric relay may implement one or all of these functions. Numerical relays are classified broadly into four different types as Overcurrent relays, Distance relays, Directional relays and Differential relays depending upon their applications. Digital/Numerical Relays addresses the urgent based need of manufacturers and users adopting this latest technology. Rao Publisher: Tata McGraw-Hill Education ISBN: 9780070588554 Size: 67.74 MB Format: PDF, Docs Category : Electric power systems Languages : en Pages : 227 View: 2237 Get Book. For example, with 16 bit A/D converter, 32 bit processor is the natural choice. Write the python code for the implementation of numerical overcurrent relay and numerical distance relay using Analog to digital converter. 1 relay can perform only 1 function. Currently, the industry is introducing digital/numerical relays as they provide sub-station protection, control and communication, and the recording of disturbances and faults. Numerical relay is actually the digital relay as a unit for which manufacturers has developed standardized hardware, which can be used in conjunction with suitably developed software to meet variety of production requirements and applications. Digital/numerical relays provide a front panel display, or display on a terminal through a communication interface. Book Description: The protective relay industry has kept pace with the technological advancements in the field. The event recording would include some means for the user to see the timing of key logic decisions, relay I/O (input/output) changes, and see, in an oscillographic fashion, at least the fundamental component of the incoming analogue parameters. The Hardware part is … Alternatively, a variable gain amplifier can be used along with the A/D converter. A listing of device numbers is found at ANSI Device Numbers. Digital input/Communication module Input Module The Power system operates with analog parameters. Among different types of relays, the electromechanical relay has the lowest cost. However, considering the order of difference between current magnitudes in case of fault and load, there can be loss of accuracy during metering applications. The sampled data is then passed through a low pass filter that numerically removes the frequency content that is above the fundamental frequency of interest (i.e., nominal system frequency), and uses Fourier transform algorithms to extract the fundamental frequency magnitude and angle. CPU: CPU stand for Central Processing Unit which is responsible for the processing of protection algorithms and digital filtering. Static relay circuit (using analog and digital ic’s) for over current: The Solid State Relay (Static Relay): History of Relay: The static relay are next generation relays .The Solid Static relays was first introduced in 1960’s. Brief Introduction about Relay: RELAY: A Relay is a protection device that senses the fault in the circuit and gives a trip signal to the Circuit Breaker to isolate the faulty circuit. we respect your privacy and take protecting it seriously. In utility and industrial electric power transmission and distribution systems, a numerical relay is a computer-based system with software-based protection algorithms for the detection of electrical faults. The protective relay industry has kept pace with the technological advancements in the field. Commentdocument.getElementById("comment").setAttribute( "id", "a9ee1e9e05a88d1af48e88d54409222f" );document.getElementById("j15d56cccb").setAttribute( "id", "comment" ); Subscribe to our mailing list and get interesting stuff and updates to your email inbox. The relay is capable of applying advanced logic. The output from the Filter is then fed to Sample and Hold (S/H)circuit. El. For instance, in some time overcurrent solid state relays, the incoming AC current is first converted into a small signal AC value, then the AC is fed into a rectifier and filter that converts the AC to a DC value proportionate to the AC waveform. Get best price and read about company. Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism. A relay that functions to prevent overheating of the field excitation winding by reducing or interrupting the excitation of the shunt field. Therefore, a simple solution would be to keep metering and protection functionality separate. The first practical commercially available microprocessor based digital/numeric relay was made by Edmund O. Schweitzer, III in the early 1980s. Numerical relay. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. Relay: Static Relay: Digital Relay: Numerical Relay: Technology Standard: 1st generation relays. If I define a Numerical Relay, honestly speaking it will seem to be quite tough but in reality they are very user friendly and easy to implement different types of protection scheme. The ECOFIT 50/51 Plug and Protect numerical relay is a direct replacement for many GE IAC and IFC relays that are still in service today. This implies that resolution of A/D converter is 2000/(212-1)=0.488 A. In distribution applications, the replacement by the digital relay proceeded a bit more slowly. ROM is also needed for storing Event and Disturbance data. If a virtual digital CCVT was designed in numerical distance relay and the output current of CT was input to virtual digital CCVT, the influence of CCVT transient of distance relays can be reduced. The numerical relay is one of electrical base of the software protection against to detect the natural & unnatural fault in the electrical machinery. In a digital/numeric relay, many functions are implemented by the microprocessor programming. There are also more specialized relays, for example, for line differential protection. The tension of the spring and taps on the electromagnetic coils in the relay are the main processes by which a user sets such a relay. In addition to the analog input, Numerical Relays are designed to accept digital input too. Most of us are aware of Electromagnetic Relays and Static Relays but most us may not be well acquainted with Numerical Relay. In 1971 M. Ramamoorty was the first to describe [8] calculation of impedance for distance protection using discrete Fourier analysis. Digital And Smart Grid Enterprises - Offering GE / Alstom P442 Numerical Distance Protection Relays, मोटर प्रोटेक्शन रिले, मोटर संरक्षण रिले in Navi Mumbai, Maharashtra. This implies that resolution of A/D converter is 2000/(2, What is IGBT? [6] In 2017 George received the IEEE Halperin Electric Transmission and Distribution Award. [1] II. A Digital Relay comprises both Hardware and Software. The digital/numeric relay was invented by George Rockefeller. Digital output contacts of Numerical Relays are used for wiring with the Auxiliary Relays to extend tripping command to the Circuit Breaker. A digital protective relay may also be called a "numeric protective relay". Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. Based on type, medium voltage protection relays can be divided into electromechanical & static relays and digital & numerical relays. The distinction between digital and numerical relays is particular to Protection. Input Module: The analog single from the Power System is stepped down using Current Transformer and Potential Transformer and then fed to the Numerical Relay using low pass filter. (1 relay can be used as over current relay, under voltage relay etc.) The analog values are compared to settings made by the user via potentiometers in the relay, and in some case, taps on transformers. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. This resolution may be inadequate for metering purposes. 2000 A. The CPU accepts the input in digital form but the input from Current Transformer CT and Potential Transformer PT are analog in nature. PAC-E Series for Numerical Protection Relay have 3 types of relay which is a microprocessor-based numerical protection relay designed for the management and protection of a distribution feeder. Few of the differences between conventional (electromechanical) and solid state (digital / numerical) relays can be highlighted as below: An electromagnetic relay is a switch that is turned on and off by a magnetic field. Digital Input / Communication Module: Numerical Relays are provided with serial and parallel ports for the interconnection with control and communication system of the substation. Scope. Numerical Relays are equipped with software to communicate with external device to program to Relay or one can program by navigating through the Relay Menu. 2nd generation relays. (IA/ICTL/IAC) [60] field relay (power system device function numbers) A relay that functions on a given or abnormally low value or failure of machine field current, or on an excessive value Functions: 1 relay can perform various functions. In this work the over current digital/numerical relay is explained with the simulink results and analysis. A Sample and Hold (S/H) circuit is used to keep the rapidly changing instantaneous value constant during the period of conversion for processing. The static relay is more costly as compared to the electromagnetic relay. However, increasing the number of bits of A/D converter also affects the selection of processor. Electromechanical and static relays have fixed wiring and the setting is manual. However, during the change from one setting to another, loss of information can take place. As a result, the relay is capable of performing complex digital signal processing to detect fault faster and more accurately compared to previous relay technology. The generalized numerical relay consists of a minimum set of hardware modules and … The first numerical relays were released in 1985. Some … This ensures that truncation and numerical precision problems associated with finite precision arithmetic do not cause significant loss of accuracy. McLaren was the first to propose the concept of Open System Relaying, where different relay functions can be obtained from the same hardware just by modifying microprocessor programming [3]. Separate terminals are provided for the analog and digital inputs. A typical Numerical Relay can store as much as 520 Events and 50 Disturbances. Output module 6. The processing of numerical relays using DSP is also optimized for real-time signal processing applications [1]. The distinction between digital and numerical protection relay rests on points of fine technical detail, and is rarely found in areas other than Protection: Ch 7, pp 102. Numerical relays are the product of the advances in technology from digital relays. A Digital Relay comprises both Hardware and Software. It is very easy to provide electrical isolation between the coil that creates the magnetic field and the switch contacts. Present generation relays. Operating Principle: They use principle of electromagnetic principle. As a minimum, magnitude of the incoming quantity, commonly using Fourier transform concepts (RMS and some form of averaging) would be used in a simple relay function. Video that explains overcurrent protection testing: This page was last edited on 28 December 2020, at 03:33. Get best price and read about company. [1] Such relays are also termed as microprocessor type protective relays. In some solid-state relays, a simple microprocessor does some of the relay logic, but the logic is fixed and simple. Let a 12 bit unipolar A/D converter be used for sampling current signal. 2.2. Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. Event and Disturbance Recording is a must feature for a digital relay because these data are used for troubleshooting any event. (1 relay can be used as over current only for under voltage we use another relay). Numerical relays use digital signal processors (DSP) cards, which contain dedicated microprocessors especially designed to perform digital signal processing. (with necessary … The most attractive feature of such relay is that it works on FIFO (First In, First Out). ELECTRO-MECHANICAL RELAY The below figure shows the schematic of an Electro-mechanical relay. digital relays, static relays or even electromechanical relays. Only the fundamental component is needed for most protection algorithms, unless a high speed algorithm is used that uses subcycle data to monitor for fast changing issues. Numerical Relays embedded with Digital Signal Processor (DSP) can be used to protect the system components as they can perform complex processing faster with … One solution is to increase resolution i.e. A big difference between conventional electromechanical and static relays is how the relays are wired. The analog single from the Power System is stepped down using Current Transformer and Potential Transformer and then fed to the Numerical Relay using low pass filter. It was commissioned in service on a 230kV transmission line at PG&E's Tesla substation in February 1971 and was in service for six years. 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