Unfortunately, power systems change their topology due to operational reasons on a regular basis, such as supply from normal or emergency generation. The choice of a protection relay rather than some other device is logical as the protection relay is probably the only device that is virtually mandatory on circuits of any significant rating. The first numerical relays were released in 1985. Top: Looking straight down, you can see the spring contacts on the left, the switch mechanism in the middle, and the electromagnet coil on the right. t. reactor protection and con trol, an exam ple of poss ible . This paper presents a study of the impacts of the Flexible AC 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. April 28, 2018 at 3:28 pm . However, it is sufficiently accurate for an operator to assess system conditions and make appropriate decisions. Introduction and Architecture of Numerical Relay. Configured by selection and manual settings. The main operation of a relay comes in places where only a low-power signal can be used to These output digital contacts are a pulse which is generated as a response signal. These can then be printed or uploaded to the user’s database facilities. Then auxiliary CT output is given to rectifier. An essential component is the Real Time Operating System (RTOS) which ensures that the other tasks are executed when required, in the correct priority. 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 noted that that the transients occures in the system due to X?R ratio of the system and henec the transients vary based on the X/R ratio . For example, with 16 bit A/D converter, 32 bit processor is the natural choice. Minimum voltage setting prevents mal-operation of the relay when fuse failure/MCB tripped conditions. Digital output contacts of Numerical Relays are used for wiring with the Auxiliary Relays to extend tripping command to the Circuit Breaker. 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. A Sample and Hold (S/H) circuit is used to keep the rapidly changing instantaneous value constant during the period of conversion for processing. Therefore, a simple solution would be to keep metering and protection functionality separate. A typical Numerical Relay can store as much as 520 Events and 50 Disturbances. However, increasing the number of bits of A/D converter also affects the selection of processor. i) Describe the operation of time-dependent static over current relay with a neat diagram. A big difference between conventional electromechanical and static relays is how the relays are wired. At low currents, high gain setting is used and at high currents low gain setting is preferred. The protection relay no longer performs a basic protection function but is an integral and major part of a substation automation scheme. Now a day for - Hence, it is clear that the speed of operation of an electrical relay depends upon the level of fault current. The first protection devices based on microprocessors were employed in 1985. 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. Each relay element is in software so with modular hardware the main signal processor can run a vast variety of relay elements. Now if IDIFF> 0.15A relay operation results. However, considering the order of difference between current magnitudes in case of fault and load, there can be loss of accuracy during metering applications. This implies that resolution of A/D converter is 2000/(2, What is IGBT? For faster real time processing and more detailed analysis of waveforms, several DSPs can be run in parallel. JNC 154 is a numerical local breaker backup relay. It is a type of a magnetic switch which uses the magnet for creating a magnetic field. Principle of operation. protective relays encounter several problems as revealed in [2]. In this paper, TMS320F28335 based Implementation of Numerical Relay is discussed. Multiplexer and Analog to Digital Converter: Numerical Relays are provided with serial and parallel ports for the interconnection with control and communication system of the substation. However, this technique fails when closing onto a dead but healthy line, so a level detector is also required to distinguish between current inrush due to line charging and that due to a fault. Software problems are minimized by rigorous use of software design techniques and the ability to download updated software. A numerical relay usually provides many more features than a relay using static or electromechanical technology. Related Post: Solid State Relay (SSR) – Types of SSR Relays – Construction & Operation Construction of a Relay. Over Current/ Earth Fault:When excessive current flows through a system it will trip the circuit br… The ADR241A continuously monitors all phases and earth current, ROM is also needed for storing Event and Disturbance data. Numeric relays are programmable rel… Many numerical relays have the facility for time synchronisation from an external clock. CT supervision is carried out more easily. Principle of operation. Generally, there are several different types of numerical protection relays. This calculation is repeated for all of the quantities of interest. Separate terminals are provided for the analog and digital inputs. Actually, a relay is nothing but a combination of one or more open or closed contacts. The standard normally used is an IRIG-B or IEEE 1588 signal, which may be derived from several sources including a GPS satellite receiver. -Working & Types of UPS Explained. This action causes the output contacts to touch, closing the load circuit. Practical experience indicates that numerical relays are as reliable as relays of earlier technologies. Saturation of CT causes errors in reproduction of the current fundamental harmonic. It may be inconvenient to download the record immediately, so facilities may be provided to capture and store a number of disturbances. Nice Article.Relays are used to provide time delay functions. Output module provided in Numerical Relay is digital contacts which are actuated when a trip decision is taken by the CPU. Typical functions that may be found in a numerical relay other than protection functions are described in this section. Dictionary says that relay means the act of passing something from one thing to another, the same meaning can be applied to this device because the signal received from one side of the device controls the switching operation on the other side. 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. In addition to the analog input, Numerical Relays are designed to accept digital input too. ), Consistency of operation times – reduced grading margin, Sequence quantities (positive, negative, zero), Max. Numerical relays are able to improve the performance of the protection operation considerably. 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. Therefore, the time of operation of relay would vary as V/I i.e. numerical relay is made of digital signal processor (DSP), whereas a microprocessor was used in digital relay [8]. Some of the new issues that must be addressed are as follows: Numerical relays perform their functions in software. The magnetic field then uses for opening and closing the switch and for performing the mechanical operation. In addition to the relay comprehensive self monitoring to alert the user ’ s database facilities with a group settings... 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