An essential component is the Real Time Operating System (RTOS) which ensures that the other tasks are executed when required, in the correct priority. Therefore, the time of operation of relay would vary as V/I i.e. It helps you. 2) Definite Time Overcurrent Relay- This type of relay operates when two conditions are met i. e. input current exceeding the relay setting value and the desired time delay is reached. The numerical value of the ratio of V to I is shown as the length of the radius vector, such as Z, and the phase angle θ between V and I determines the position of vector, as shown. A numerical relay usually provides many more features than a relay using static or electromechanical technology. Logic functions are well suited to implementation using microprocessors. For faster real time processing and more detailed analysis of waveforms, several DSPs can be run in parallel. 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. A thermal overload relay works in the principle of electro-thermal properties in a bimetallic strip. the number of bits in A/D converter. 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. For example, one may use 16 bit A/D converter in place of 12 bit A/D converter. The problems have been addressed with software to automate the preparation and download of relay setting data from a laptop PC connected to a communications port of the relay. This is often done using a Discrete Fourier Transform (DFT) and the result is magnitude and phase information for the selected quantity. The protection relay no longer performs a basic protection function but is an integral and major part of a substation automation scheme. INTRODUCTION Inrush or overexcitation conditions of a power transformer produce false differential currents that could cause differential relay misoperation. Minimum voltage setting prevents mal-operation of the relay when fuse failure/MCB tripped conditions. The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. A numerical relay can record all of these parameters and hence be configured to send an alarm when maintenance is due. Incorrect results are then obtained. Analogue signals are converted to digital form using an A/D converter. Hence, it is clear that the speed of operation of an electrical relay depends upon the level of fault current. Electromechanical and static relays have fixed wiring and the setting is manual. – Construction and Working Principle, Binary Coded Decimal or BCD Number Explained, What is UPS? 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 suitable VTs are used, supervision of the VT/CT supplies can be made available. 2000 A. Many numerical relays have the facility for time synchronisation from an external clock. 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. In other words, the time of operation of the relay depends upon plug setting multiplier. It may be inconvenient to download the record immediately, so facilities may be provided to capture and store a number of disturbances. Now if IDIFF> 0.15A relay operation results. Abstract— In this paper a prototype algorithm for Numerical Distance relay is developed in order to prevent mal-operation of relays when Current Transformer (CT) saturation occurs. Numerical relays are based on the use of microprocessors. The present protection technique used is unable to ensure selectivity and speedily operation for the faults appearing on the entire protected line. It consists of a flexible moving mechanical part which can be controlled electronically through an electromagnet, basically, a relay is just like a mechanical switch but you can control it with an electronic signal instead of manually turning it on or off. The time delay is also known as operation time is computed from the protection algorithm embedded in the processor. Digital Input / Communication Module: Numerical Relays are provided with serial and parallel ports for the interconnection with control and communication system of the substation. TMS320F28335 is a floating point Digital Signal Controller (DSC). Modern numerical relay protection scheme offers multi-function and multiple characteristics, and other several advantages. 5. A Relay is an electromechanical device that can be used to make or break an electrical connection. The argument against putting many features into one piece of hardware centres on the issues of reliability and availability. Nice Article.Relays are used to provide time delay functions. This action causes the output contacts to touch, closing the load circuit. 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. Electric FA Site.” The protection relay supports USB Type B connection. The alternative is to provide each input with a dedicated A/D converter and logic to ensure that all converters perform the measurement simultaneously. A Digital Relay comprises both Hardware and Software. The main operation of a relay comes in places where only a low-power signal can be used to 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. ROM is also needed for storing Event and Disturbance data. 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. 3. 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. As the relay current does not increase further, there would not be any further reduction in time of operation in the relay. Many functions previously implemented in separate items of hardware can then be included in a single item. Each type, however, shares a similar architecture, thus enabling designers to build an entire system solution that is based on a relatively small number of flexible components. Commentdocument.getElementById("comment").setAttribute( "id", "ad2c8b195f7d42869ab347867cb2cf1e" );document.getElementById("j15d56cccb").setAttribute( "id", "comment" ); Subscribe to our mailing list and get interesting stuff and updates to your email inbox. 2000 A. This implies that resolution of A/D converter is 2000/(212-1)=0.488 A. This implies that resolution of A/D converter is 2000/(2, What is IGBT? Although there is an internal clock, this is of limited accuracy and use of this clock to provide time information may cause problems if the disturbance record has to be correlated with similar records from other sources to obtain a complete picture of an event. Single function devices. Similarly, the amount of data that must be recorded is much larger, requiring larger storage. Numerical relays are natural developments of digital relays due to advances in technology. 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. The small power relay has only one contacts, and the high power relay has two contacts for opening the switch. The typical architecture of a numerical relay is shown in Figure 6. Electromagnetic Relay Definition: Electromagnetic relays are those relay which operates on the principle of electromagnetic attraction. A MATLAB model of a frequency relay was detailed before . 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. However, if the DSP is overloaded it cannot complete the protection algorithm calculations in the required time and the protection function is slowed. A typical Numerical Relay can store as much as 520 Events and 50 Disturbances. 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. The content is copyrighted to EEP and may not be reproduced on other websites. Introduction and Architecture of Numerical Relay. 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. 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. In industrial and small distribution networks, this may be all that is required. Figure 1, Figure 2 and Figure 3 show typical numerical relays, while Figure 4 and Figure 5 show typical numerical relay boards. In this paper, TMS320F28335 based Implementation of Numerical Relay is discussed. i) Describe the operation of time-dependent static over current relay with a neat diagram. Bottom: The same relay photographed from the front.Suppose you want to build an electronically operated coolingsystem that switches a fan on or off as your room temperaturechanges. 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. In principle, the hardware setup discussed above can be used for both measurement and protection function. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. Now a day for - In case more than one analog quantity is to be converted into digital form, Multiplexer is used for selecting any analog input at a time to convert into digital form. The operation of these relays are independent of the fault current level rather the time delay provided to it to work. of Int. However I am going to define a Numerical 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. To know the basic construction and internal parts of a relay, the following fig clearly shows an inside view of a relay.Lets discuss all of them one by one. Therefore and A/D converter is used to convert the analog signal to digital signal. The internal communications bus links the hardware and therefore is a critical component in the design. By using DSP as the relay’s processor, the relay is capable of meeting the fundamental A very high voltage develops across the relay circuit and the CT’s which can damage the insulation of CT’s, secondary wiring and relay. Operation of Electromagnetic -attraction Relay:Figure shows a typical electro mechanical relay. DSP based Numerical Relay discussed in this paper can discriminate better between above conditions Based on Logic These classifications are made on the basis of logical operation of the relay 1. Saturation of CT causes errors in reproduction of the current fundamental harmonic. Numerical relays These relays are controlled by a smart controlling unit that continually monitors the grid parameters (such as voltages, currents, temperature, etc) and switches the appropriate relays in case fault conditions occur. CPU: CPU stand for Central Processing Unit which is responsible for the processing of protection algorithms and digital filtering. Actually, a relay is nothing but a combination of one or more open or closed contacts. General: The ADR241A is member of Ashida Numerical Relay family (Aditya Series) design to meet demand of low and medium switchgear control. A single Numerical relay can monitor multiple parameters like current, voltage, Frequency, onset time, offset time, etc. It detects the intolerable or undesirable condition with an assigned area and gives the commands to the circuit breaker to disconnect the affected area. They are functional replacements for electro-mechanical protective relays and may include many protection functions in one unit, as well as providing metering, communication, and self-test functions. The general principle is the calculation of a level of negative sequence current that is inconsistent with the calculated value of negative sequence voltage. 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. Photo: Another look at relays. Arithmetic do not cause operation of numerical relay loss of accuracy an electrical relay depends the..., while Figure 4 and Figure 5 show typical numerical relays are developments... Temporary magnetic field then uses for opening the switch protection functionality separate for! 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