Other software depends on the function of the relay, but can be generalized as follows: The relevant software algorithm is then applied. This is often done using a Discrete Fourier Transform (DFT) and the result is magnitude and phase information for the selected quantity. An essential component is the Real Time Operating System (RTOS) which ensures that the other tasks are executed when required, in the correct priority. 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. It is also easier to customize a relay for a specific application, and eliminate other devices that would otherwise be required. Position of relay: Relay can be installed at any location and at any position. He is member of Institution of Engineers (MIE), India. i) Describe the operation of time-dependent static over current relay with a neat diagram. The relay memory requires a certain minimum number of cycles of measured data to be stored for correct signal processing and detection of events. Scope 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. However, by providing a substantial number of digital I/O and making the logic capable of being programmed using suitable off-line software. It must work at high speed, use low voltages, yet be immune to conducted and radiated interference from the electrically noisy substation environment. 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. Such relays are also termed as microprocessor type protective relays. ii) Write the purpose of Start of Conversion (S/C) and End of Conversion (E/C) signals in the Numerical Relay? Jignesh Parmar has completed M.Tech (Power System Control), B.E (Electrical). demand in a period ( kW, kVAr; average and peak values), Motor start information (start time, total no. El. Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! 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. They use one or more digital signal processors (DSP) optimised for real time signal processing, running the mathematical algorithms for the protection functions. Good work Jignesh, But for El Mechanical Relay like CDD21 (Alstom) Aux. 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 … As the power of microprocessors continues to grow and pressure on operators to reduce costs continues, this trend will continue. 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. 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. This relay has to be installed straight only and away from magnetic field. Each relay element is in software so with modular hardware the main signal processor can run a vast variety of relay elements. Reference // Network Protection & Automation Guide by Alstom Grid. It may be inconvenient to download the record immediately, so facilities may be provided to capture and store a number of disturbances. 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. The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. [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. low burden on the CT and VT, fast operation, absence of mechanical inertia and; contact trouble, long life and; less maintenance. Dear Jignesh A very well compiled work. The general principle is the calculation of a level of negative sequence current that is inconsistent with the calculated value of negative sequence voltage. Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. VT supervision is made more complicated by the different conditions under which there may be no VT signal, some of which indicate VT failure and some occur because a power system fault has occurred. Present generation relays. Static relays are used for the protection of important lines, power stations and sub-stations. The numerical relays are used for various types of protection and they are classified on the basis of characteristics, Logic, Actuation parameter and application. The cheapest method is to use a single A/D converter, preceded by a multiplexer to connect each of the input signals in turn to the converter. Many functions previously implemented in separate items of hardware can then be included in a single item. Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. are required to construct this protective relay.. The protection relay no longer performs a basic protection function but is an integral and major part of a substation automation scheme. 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. 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