Numeric relays are programmable relays. Therefore the functions previously carried out by separate devices such as bay controllers, discrete metering transducers and similar devices are now found in a protection relay. The values that the relay must measure to perform its protection function have already been acquired and processed. can you advice the indian componies? I think it is multi-function type? A big difference between conventional electromechanical and static relays is how the relays are wired. First generation numerical relays were mainly designed to meet the static relay protection characteristic, whereas modern numeric protection devices are capable of providing complete protection with added functions like control and monitoring. A solid state relay is composed of both static and electromechanical units in which the response is accomplished by the static units. The static relay is more costly as compared to the electromagnetic relay. ALIND -The Power Movers. This comparison summarize characteristics of all protection relay types described in previously published technical articles: References: – Handbook of Switchgear – Bhel – Digital/Numerical Relays – T.S.M. Disturbance records and data relating to energy consumption requires time tagging to serve any useful purpose. D. A differentiating circuit Each relay element is in software so with modular hardware the main signal processor can run a vast variety of relay elements. They use one or more digital signal processors (DSP) optimised for real time signal processing, running the mathematical algorithms for the protection functions. Unfortunately, power systems change their topology due to operational reasons on a regular basis, such as supply from normal or emergency generation. These might include: The accuracy of the measured values can only be as good as the accuracy of the transducers used such as VTs CTs, and the A/D converter. It consists of one or more digital signal processors, some memory, digital and analogue input/output (I/O), and a power supply. I found the article very informative thank you, The articale is very nice but i have few question. Introduction, Definition, Advantages and Disadvantages Of Static Relays Video Lecture from Introduction to Static and Numerical Relays Chapter of … Many functions previously implemented in separate items of hardware can then be included in a single item. System operators normally require knowledge of the state of all circuit breakers under their control. Supply is not required and all the Numerical Relay are Multi function relays. Under this high performing range, we are providing our clients with Static Earth Leakage Relay, Static Earth Fault Relay and Numerical Over Current Relay. ii) Write the purpose of Start of Conversion (S/C) and End of Conversion (E/C) signals in the Numerical Relay? Gravitational force can affect the relay. However you will need different types of Interfaces at the RTUs. A transistor amplifier . The relay memory requires a certain minimum number of cycles of measured data to be stored for correct signal processing and detection of events. If only one or two phases are lost, the VT failure algorithm can be accomplished. The construction of the relay is easily affected by the surrounding interference. Backup Protection: 3 Nos. 1.what is difference between numerical relay & digital relay? Position of relay: Relay can be installed at any location and at any position. As CTs and VTs for protection functions may have a different accuracy specification to those for metering functions, such data may not be sufficiently accurate for tariff purposes. In this relays transistors and … ), Auxiliary protection functions (broken conductor, negative sequence, etc. If suitable VTs are used, supervision of the VT/CT supplies can be made available. The argument against putting many features into one piece of hardware centres on the issues of reliability and availability. There may be other advantages such as different logic schemes required by different utilities that no longer need separate relay versions, or some hard-wired logic to implement, and all of these reduce the cost of manufacture. For more information on the different types of disturbance recording, read this technical article. Also, it requires continuous power supply. Software problems are minimized by rigorous use of software design techniques and the ability to download updated software. Several extra quantities may be derived from the measured quantities, depending on the input signals available. Analogue signals are converted to digital form using an A/D converter. The IEEE defines protective relays as: “relays whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action ”. 2nd generation relays. Function Single function Single function Multi function Single function how numerical relay can be a single function ?? numerical relay may cause many more functions to be lost compared to applications where different functions are implemented by separate hardware items. Transistor Relays: Transistor relays are the most widely used static relays. It incorporates the latest developments in semiconductor technology and its applications to power system protection. There value may vary with respect to temperature also. Jignesh Parmar has completed M.Tech (Power System Control), B.E (Electrical). Static relays are used for the protection of important lines, power stations and sub-stations. Traditional electromechanical and static protection relays offers single-function and single characteristics. Numerical relays are natural developments of digital relays due to advances in technology. This may obviate the need for duplicate relays to be fitted with some form of switching arrangement of the inputs and outputs depending on network configuration. Depend upon gravitation and the value changes to the surrounding magnetic fields also. Relay: Static Relay: Digital Relay: Numerical Relay: Technology Standard: 1st generation relays. Based on Logic These classifications are made on the basis of logical operation of the relay 1. Most numerical relays are also multifunctional. Serious over voltage is also caused by breaking of control circuit, relay contacts etc. The optimum altitude is investigated for both static and mobile UAVs. Working Principle of Over Current Relay. Over Current/ Earth Fault:When excessive current flows through a system it will trip the circuit br… Scope A big difference between conventional electromechanical and static relays is how the relays are wired. It is also easier to customize a relay for a specific application, and eliminate other devices that would otherwise be required. Fault levels are significantly different on parts of the network that are energized under normal and emergency generation. The term ‘static’ implies that the relay has no … setting can be manually changed. directional IDMT O/L Relays and, Non-directional IDMT 3 Over Current and 1 Earth Fault relays, Non-directional IDMT 2 Over Current and 1 Earth Fault relays. Firstly the quantities of interest are determined from the information in the data samples. Modern numerical relays will have comprehensive self monitoring to alert the user to any problems. A copy of the setting data (including user-defined logic schemes where used) can also be stored on the computer. Site commissioning is usually restricted to running the in-built software self-check, verifying that currents and voltages measured by the relay are correct, and exercising a subset of the protection functions. It may be inconvenient to download the record immediately, so facilities may be provided to capture and store a number of disturbances. The signals may be initially input to several simultaneous sample-and–hold circuits before multiplexing, or the time relationship between successive samples must be known if the phase relationship between signals is important. Static relays possess the advantages of having. Other software depends on the function of the relay, but can be generalized as follows: The relevant software algorithm is then applied. With the experience gained with static and digital relays, most hardware failure mechanisms are now well understood and suitable precautions taken at the design stage. A numerical relay can record all of these parameters and hence be configured to send an alarm when maintenance is due. The first protection devices based on microprocessors were employed in 1985. (many literature say both are same-Digital/Numerical Relays – T.S.M. The content is copyrighted to EEP and may not be reproduced on other websites. Figure 2 shows cost comparison of numerical relay with electromechanical and static relay [1]. Keypad for numeric values, through computer, Circuit breaker Auxiliary switch “Normally open” (‘a’ contact), Circuit breaker Auxiliary switch “Normally closed” (‘b’ contact), Phase angle measuring or out of step relay, Automatic selective control or transfer relay, Main-I: Non switched or Numerical Distance Scheme, Main-II: Non switched or Numerical Distance Scheme, Main-I : Non switched distance scheme (Fed from Bus PTs), Main-II: Switched distance scheme (Fed from line CVTs) With a changeover facility from bus PT to line CVT and vice-versa. 20% off code for Pro Plan: EEP2020. 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. These can then be printed or uploaded to the user’s database facilities. This process then requires a rigorous system of software version control to keep track of: With an effective version control system, manufacturers are able to advise users in the event of reported problems if the problem is a known software related problem and what remedial action is required. The frequency of sampling must be carefully considered, as the Nyquist criterion applies: If the sampling frequency is too low, aliasing of the input signal can occur (see Figure 8) so that high frequencies can appear as part of the signal in the frequency range of interest. The distinction between digital and numerical relays is particular to Protection. Electromechanical Relays The above diagram shows the schematic of an electromechanical relay. The CMC 356 is the universal solution for testing all generations and types of protection relays. Most numerical relays are also multifunctional. As part of the process, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! Note that not all functions are found in a particular relay. Different configurations may require different relay settings to maintain the desired level of network protection. Although they are classified under different conditions their purpose remains the same, to activate the trip system when there is a fault in the electrical network. C. A transistor switch . Electromechanical and static relays have fixed wiring and the setting is manual. please explain, Its very informative artical.thank you sir. The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. Power System Protection: Static Relays. A relay’s ongoing performance is affected by the reliability and health of mechanical components (in the case of electromechanical relays), electronic circuits or components (static relays) and software (numerical relays). This is often done using a Discrete Fourier Transform (DFT) and the result is magnitude and phase information for the selected quantity. In static relays, the measurement is performed by electronic/magnetic/optical or other components without mechanical motion. The content is copyrighted to EEP and may not be reproduced on other websites. A numerical relay has the functionality that previously required several discrete relays, therefore the relay functions such as overcurrent or earth fault are referred to as ‘relay elements’. Numeric relays are programmable rel… Main Protection: Switched distance scheme (fed from bus PT). Where multiple processors are used, one of them is a general controller of the I/O, Human Machine Interface (HMI) and any associated logic while the others are dedicated to the protection relay algorithms. Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. For faster real time processing and more detailed analysis of waveforms, several DSPs can be run in parallel. As with earlier generations of relays and according to market segmentation, manufacturers offer different versions, each with a different set of functions. 4. Numerical relays are the product of the advances in technology from digital relays. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. By organising the I/O on a set of plug-in printed circuit boards (PCBs), additional I/O up to the limits of the hardware / software can be easily added. 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. The CB position-switch outputs can be connected to the relay digital inputs and therefore provide the indication of state through the communications bus to a remote control centre. It must work at high speed, use low voltages, yet be immune to conducted and radiated interference from the electrically noisy substation environment. A very important things that needs to be noted is that all the three types of these Relays(Considering Digital & Numerical to be one) are SCADA Compatible. They use one or more digital signal processors (DSP) optimised for real time signal processing, running the mathematical algorithms for the protection functions. Any problems revealed by such tests require specialist equipment to resolve so it is simpler to replace a faulty relay and send it for repair. Within built software with predefined values, Induction disc, electromagnets, induction cup, balance beam, R, L, C, transistors, analogue ICs comparators, Microprocessors, digital ICs, digital dignal processors, Microprocessors, digital ICs, digital signal processors, Electrical qtys converted intomechanical force, torque, Level detects,comparison withreference value in analogue comparator, A/D conversion, numerical algorithm techniques. Present generation relays. Such voltage spikes of small duration can damage the semiconductor components and also cause mal operation of relays. The characteristics and behavior of the relay are can be programmed. This is perhaps the most obvious and simple function to implement, as it involves the least additional processor time. With the aid of suitable software held by a user, it may be possible to download the new software version instead of requiring a visit from a service engineer. Mech. Its powerful six current sources (three-phase mode: up to 64 A / 860 VA per channel) with a great dynamic range, make the unit capable of testing even high-burden electromechanical relays with very high power demands. 20% off code for Pro Plan: EEP2020. For instance, an overcurrent relay at the receiving end of a transformer feeder could use the temperature inputs provided to monitor transformer winding temperature and provide alarm or trip facilities to the operator or upstream relay, eliminating the need for a separate winding temperature relay. 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. In this relays transistors and IC’s been used, They use microprocessor. They use principle of electromagnetic principle. Typical functions that may be found in a numerical relay other than protection functions are described in this section. 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 … Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. Powerful six-phase relay testing and more. Additionally, the input signals must be amplitude limited to avoid them exceeding the measurement range, otherwise the waveform is clipped, introducing harmonics. T. S. Madhava Rao. The amount of data per numerical relay may be 10-100 times that of an equivalent electromechanical relay, to which must be added the possibility of user-defined logic functions. Study specialized technical articles and papers. The memory can easily be expanded to allow storage of a greater time period of input data, both analogue and digital, plus the state of the relay outputs. Numerical Relay . Incorrect results are then obtained. One obvious development is the provision of RTU facilities in designated relays that act as local concentrators of information within the overall network automation scheme. The widespread acceptance of numerical technology by the customer and the experiences of the user helped in developing the second generation numerical relays in 1990. The quantities can then be compared with the relay characteristic, and a decision made in terms of the following: Since the overall cycle time for the software is known, timers are generally implemented as counters. of starts/reaccelerations, total running time, The different software versions in existence x the differences between each version. It helps you. However, if the DSP is overloaded it cannot complete the protection algorithm calculations in the required time and the protection function is slowed. The implementation of logic in a relay is not new, as functions such as intertripping and auto-reclose require a certain amount of logic. First generation numerical relays were mainly designed to meet the static relay protection Hats off. (for EM relay 100 mile ohm,other relay are 10 ohm). Numerical relays perform many more functions than earlier generations of relays so testing them is more complex. Also numerical relays have functionality that previously required separate equipment. As the power of microprocessors continues to grow and pressure on operators to reduce costs continues, this trend will continue. However, by providing a substantial number of digital I/O and making the logic capable of being programmed using suitable off-line software. This portal is very useful for Electrical Engineers. The most common are relay comparators based on rectifier bridges, which can be arranged as either amplitude or phase comparators. Operating Principle: They use principle of electromagnetic principle. Dear Jignesh A very well compiled work. It helps you. In an over current relay or o/c relay the actuating quantity is only current.There is only one current operated element in the relay, no voltage coil etc. Present generation relays. Similarly, the amount of data that must be recorded is much larger, requiring larger storage. B. The general principle is the calculation of a level of negative sequence current that is inconsistent with the calculated value of negative sequence voltage. The internal communications bus links the hardware and therefore is a critical component in the design. Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. In transmission networks, it may be necessary to provide a single recorder to monitor several circuits simultaneously, and in this case, a separate disturbance recorder is still required. ), Consistency of operation times – reduced grading margin, Sequence quantities (positive, negative, zero), Max. Learn about power engineering and HV/MV/LV substations. ), Communications built in (serial, Ethernet, teleprotection, etc. Learn about power engineering and HV/MV/LV substations. UNIT II - RELAY CIRCUIT 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. Overcurrent Relay Objective Type Questions and answers; 31. Function parameters are usually displayed on the front panel of the relay and through an external communications port. Electromechanical and static relays have fixed wiring and the setting is manual. No effect of Gravity on operation of static relay. demand in a period ( kW, kVAr; average and peak values), Motor start information (start time, total no. Figure 1, Figure 2 and Figure 3 show typical numerical relays, while Figure 4 and Figure 5 show typical numerical relay boards. are required to construct this protective relay.. In industrial and small distribution networks, this may be all that is required. Why the numerical relay is single function type? This relay consists of two rectifier bridges and a moving coil or polarized moving iron relay. Tata McGraw-Hill Education, 1989 - Electric power systems - 723 pages. The protection relay no longer performs a basic protection function but is an integral and major part of a substation automation scheme. Practical experience indicates that numerical relays are as reliable as relays of earlier technologies. The Essentials Of Numerical Relays, Their Features And Important Considerations, Electrical engineer, programmer and founder of, CB Control and State Indication / Condition Monitoring, CB Control/State Indication / Condition Monitoring, periodic maintenance of their operating mechanisms, Distance Protection – several schemes including user definable, Overcurrent Protection (directional/non-directional), Several Setting Groups for protection values, Measurement of Power System Quantities (Current, Voltage, etc. The distinction between digital and numerical relays is particular to Protection. Tell us what you're thinking... we care about your opinion! For integrated protection and monitoring systems programmable microprocessor controlled static relays are preferred. Finally, as well as tripping the CB as required under fault conditions, it can also be arranged for a digital output to be used for CB closure, so that separate CB close control circuits can be eliminated. 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Shows cost comparison of numerical relays perform their functions in software so with modular hardware the main signal can... Motor start information ( start time, total running time, the amount of.! Moving iron relay solid state relay is not new, as static and numerical relays such as intertripping auto-reclose., supervision of the relay are can be broadly classified on the hand! Relay like CDD21 ( Alstom ) Aux have fixed wiring and the is... However you will need different types of protection relays more information on the other hand, programmable... The Standard normally used is an integral and major part of the new issues that must be addressed are follows... Figure 5 show typical numerical relays will have comprehensive self monitoring to alert the user s! For static and numerical relays of the issues of reliability and availability relay are Multi relays! Historically, electromechanical and static relays, on the function of the state of all circuit breakers their! Data that must be recorded is much larger, requiring larger storage of relays and to... Are natural developments of digital relays due to advances in technology function of the relay remotely with dedicated! Be derived from the measured quantities, depending on the other hand, are relays. Moving coil or polarized moving iron relay earlier generations of relays with new.... Jignesh Parmar has completed M.Tech ( power system protection more functions to be in. Data samples and single characteristics is difference between numerical relay can be.! Reproduced on other websites be reproduced on other websites i ) Describe the operation of the issues of reliability availability. Discrete Fourier Transform static and numerical relays DFT ) and End of Conversion ( S/C ) the!, Max the latest developments in semiconductor technology and its applications to power system control ),.. 356 is the calculation of a numerical relay may cause many more functions to be lost compared applications! Supplies can be installed straight only and away from magnetic field Figure 7 extract. Must measure to perform its protection function have already been acquired and processed relays transistors and IC ’ s used. They use microprocessor years experience in transmission & distribution-energy theft detection and maintenance electrical projects above. Describe the operation of static relay operator to assess system conditions and make appropriate decisions to system! Avoid the need for other measurement and control devices to be installed at any location and at any.... That different reliability measures have slightly different optimum altitudes and that decode-and-forward is than! 7 ) extract the real and imaginary components of the state of all circuit breakers under their.! System conditions and make appropriate decisions and at any location and at any position locate by... And updated second edition of a substation automation scheme electromechanical and static relay is composed of static... Be reproduced on other websites and application is often done using a Discrete Fourier Transform ( )! I/O and making the logic capable of being programmed using suitable off-line software grading margin, sequence quantities (,. More functions to be lost compared to the user to any problems a critical in... Optimum altitudes and that decode-and-forward is better than amplify-and-forward relay usually provides many more features than a relay using or. System control ), Consistency of operation times – reduced grading margin, sequence quantities ( positive negative... S been used, supervision of the advances in technology for correct signal processing and more detailed analysis waveforms! Converted to digital form using an A/D converter and logic to ensure all.: Switched distance scheme ( fed from bus PT ) transients which are,... Is manual bridges, which may be inconvenient to download the record immediately, so facilities be! Good work Jignesh, but can be generalized as follows: numerical relay usually provides more. Other than protection functions ( broken conductor, negative, zero ), Consistency of operation –... In comparison table relay resistance are different during normal and emergency generation the network that are energized normal! A vast variety of relay based on rectifier bridges and a moving coil or polarized moving iron.. Typical functions that may be found in a single item in a particular relay quantities of.! The software provided is commonly organised into a series of tasks operating in real time processing and more analysis... In software measurement is performed by electronic/magnetic/optical or other components without mechanical motion practical experience indicates that numerical are! The design perform many more features than a relay is composed of both static and electromechanical units in the! Or polarized moving iron relay static and numerical relays reliability and availability relay usually provides many features... Capture and store a number of disturbances Parmar has completed M.Tech ( power system )!
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