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. A big difference between conventional electromechanical and static relays is how the relays are wired. A transistor amplifier . 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. Modern numerical relays will have comprehensive self monitoring to alert the user to any problems. 20% off code for Pro Plan: EEP2020. setting can be manually changed. It helps you. This is often done using a Discrete Fourier Transform (DFT) and the result is magnitude and phase information for the selected quantity. Working Principle of Over Current Relay. To use these features, the appropriate data must be entered into the relay’s memory and it is good practice to keep a backup copy. He has more than 13 years experience in transmission & distribution-energy theft detection and maintenance electrical projects. 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. Numerical Relay . 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. A solid state relay is composed of both static and electromechanical units in which the response is accomplished by the static units. The typical architecture of a numerical relay is shown in Figure 6. Numerical relays are the product of the advances in technology from digital relays. Electromechanical and static relays have fixed wiring and the setting is manual. As part of the process, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. Electromechanical Relays The above diagram shows the schematic of an electromechanical relay. This relay has to be installed straight only and away from magnetic field. Static relays possess the advantages of having. 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. The optimum altitude is investigated for both static and mobile UAVs. Similarly, the amount of data that must be recorded is much larger, requiring larger storage. A 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. It incorporates the latest developments in semiconductor technology and its applications to power system protection. The continuing reduction in the cost and size of microprocessors, memory and I/O circuitry leads to a single item of hardware for a range of functions. Functions: 1 relay can perform various functions. 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. The book is a thoroughly revised and updated second edition of a successful text. These can then be printed or uploaded to the user’s database facilities. 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. D. A differentiating circuit [info]It then has the capability to act as a disturbance recorder for the circuit being monitored, so that by freezing the memory at the instant of fault detection or trip, a record of the disturbance is available for later download and analysis. ii) Write the purpose of Start of Conversion (S/C) and End of Conversion (E/C) signals in the Numerical Relay? this portal is very helpful to all the electrical engineering student as well as professor and technical engineer.It’s very nice and helpful for all in electrical engineering to get practical knowledge & idea very easily. low burden on the CT and VT, fast operation, absence of mechanical inertia and; contact trouble, long life and; less maintenance. 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 term ‘static’ implies that the relay has no … In a static over current relay, inverse time characteristics are obtained by . The content is copyrighted to EEP and may not be reproduced on other websites. It is now possible to implement a substation automation scheme using numerical relays as the main hardware provided at bay level. 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. 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. Generally, there are several different types of numerical protection relays. In industrial and small distribution networks, this may be all that is required. of starts/reaccelerations, total running time, The different software versions in existence x the differences between each version. 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. Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. Software problems are minimized by rigorous use of software design techniques and the ability to download updated software. If only one or two phases are lost, the VT failure algorithm can be accomplished. Typical functions that may be found in a numerical relay other than protection functions are described in this section. El. Study specialized technical articles and papers. In static relays, the measurement is performed by electronic/magnetic/optical or other components without mechanical motion. 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. If maintenance is not carried out within a predefined time or number of trips after maintenance is required, the CB can be arranged to trip and lockout or inhibit certain functions such as auto-reclose. Historically, electromechanical and static relays have been provided with fixed plug settings applied to the relay. The continuing reduction in the cost and size of microprocessors, memory and I/O circuitry leads to a si… Based on Logic These classifications are made on the basis of logical operation of the relay 1. Some of the new issues that must be addressed are as follows: Numerical relays perform their functions in software. Such relays are also termed as microprocessor type protective relays. A. The task of entering the data correctly into a numerical relay becomes a much more complex task than previously, which adds to the possibility of a mistake being made. Analogue signals are converted to digital form using an A/D converter. ), Consistency of operation times – reduced grading margin, Sequence quantities (positive, negative, zero), Max. More than 7 decades ago, ALIND pioneered the manufacture of Aluminium conductors in India. Scope i) Describe the operation of time-dependent static over current relay with a neat diagram. Static relays are used for the protection of important lines, power stations and sub-stations. 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 process used for software generation is no different in principle to that for any other device using real-time software, and includes the difficulties of developing code that is error-free. An essential component is the Real Time Operating System (RTOS) which ensures that the other tasks are executed when required, in the correct priority. Operating Principle: They use principle of electromagnetic principle. 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 content is copyrighted to EEP and may not be reproduced on other websites. Powerful six-phase relay testing and more. It is also easier to customize a relay for a specific application, and eliminate other devices that would otherwise be required. They use one or more digital signal processors (DSP) optimised for real time signal processing, running the mathematical algorithms for the protection functions. 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. Function parameters are usually displayed on the front panel of the relay and through an external communications port. The standard normally used is an IRIG-B or IEEE 1588 signal, which may be derived from several sources including a GPS satellite receiver. Present generation relays. However, if the DSP is overloaded it cannot complete the protection algorithm calculations in the required time and the protection function is slowed. 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 ”. 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