As the power of microprocessors continues to grow and pressure on operators to reduce costs continues, this trend will continue. 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. They are used to time the delay open and delay close of contacts. Instantaneous Relays – These relays employed after a small time duration from the incidence of the current or other quantity resulting in operation. A numerical relay usually provides many more features than a relay using static or electromechanical technology. The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. This thesis describes the design and implementationof the PIC microcontroller based system for protecting 1KVA transformer from over current. A Digital Relay comprises both Hardware and Software. 2000 A. ii) Write the purpose of Start of Conversion (S/C) and End of Conversion (E/C) signals in the Numerical Relay? This resolution may be inadequate for metering purposes. 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’. Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. Electro Mechanical Relay • Memory of previous Fault records, Actual Value of Fault Current, etc. Hence, the characteristic is inverse in the initial part, which tends to a definite minimum operating time as the current becomes very high. -Working & Types of UPS Explained. Logic functions are well suited to implementation using microprocessors. Modern numerical relays will have comprehensive self monitoring to alert the user to any problems. Sir please clear that,in Higher over current setting calculation,how you have considered relay plug setting is 2.5? CT supervision is carried out more easily. Now if IDIFF> 0.15A relay operation results. Balanced Beam Type : In this relay, the armature is fastened to a balanced beam. 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. Low pass filter is incorporated in the input module to eliminate any noise single induced in the line due to corona or induction effect of nearby high voltage line. numerical relay is made of digital signal processor (DSP), whereas a microprocessor was used in digital relay . 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. Each relay element is in software so with modular hardware the main signal processor can run a vast variety of relay elements. 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. Learn about power engineering and HV/MV/LV substations. Note that not all functions are found in a particular relay. The alternative is to provide each input with a dedicated A/D converter and logic to ensure that all converters perform the measurement simultaneously. This action causes the output contacts to touch, closing the load circuit. Alternatively, 0.15A is the minimum diff current required for relay operation if the system loading is 0.5A (sec). Additionally, the input signals must be amplitude limited to avoid them exceeding the measurement range, otherwise the waveform is clipped, introducing harmonics. A big difference between conventional electromechanical and static relays is how the relays are wired. ROM is also needed for storing Event and Disturbance data. Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism. 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. So relay is a switch which controls (open and close) circuits electromechanically. One is RAM (Random Access Memory) and ROM (Read Only Memory). 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. It works on the principle of an electromagnetic attraction. A copy of the setting data (including user-defined logic schemes where used) can also be stored on the computer. The extra facilities in numerical relays may avoid the need for other measurement and control devices to be fitted in a substation. Every relay manufacturer with numerical relays will publish the transient dimensioning factor for their relay operation based on a range of X/R ratio . The magnetic field then uses for opening and closing the switch and for performing the mechanical operation. Now a day for - The term "high speed" connotes operation in less than approximately 0.1 second and usually in 0.05 second or less. Different types of relay characteristics. Many are downloadable. DSP based Numerical Relay discussed in this paper can discriminate better between above conditions Every relay manufacturer with numerical relays will publish the transient dimensioning factor for their relay operation based on a range of X/R ratio . Then auxiliary CT output is given to rectifier. The software provided is commonly organised into a series of tasks operating in real time. Numerical relays are natural developments of digital relays due to advances in technology. Photo: Another look at relays. If only one or two phases are lost, the VT failure algorithm can be accomplished. relays that operate in a minimum time of approximately 0.1 second. The DSP embedded in the numerical relay is able to The first numerical relays were released in 1985. 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. 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. The electromechanical relay can be defined as an electrically operated switch that completes or interrupts a circuit by physical movement of electrical contacts into contact with each other. A numerical relay can record all of these parameters and hence be configured to send an alarm when maintenance is due. A single Numerical relay can monitor multiple parameters like current, voltage, Frequency, onset time, offset time, etc. In other words, the time of operation of the relay depends upon plug setting multiplier. ), Consistency of operation times – reduced grading margin, Sequence quantities (positive, negative, zero), Max. They incorporate an extensive self-supervision system that continuously monitors the internal hardware and software of the relay. A good design guideline is to choose a processor with double the number of bits of A/D converter. A very important aspect of the relay operation is that it should be able to detect all fault conditions but should not trip due to spurious signals generated during power system transients. Numeric relays are programmable rel… However, by providing a substantial number of digital I/O and making the logic capable of being programmed using suitable off-line software. View Numerical Relays PPTs online, safely and virus-free! Mohit krushna pradhan says: June 26, 2016 at 3:40 pm. The small power relay has only one contacts, and the high power relay has two contacts for opening the switch. Generally, there are several different types of numerical protection relays. The range is (-95 to +95 Degrees). In addition to the analog input, Numerical Relays are designed to accept digital input too. Differential relay :- A two-winding relay that operates when the difference between the currents / Voltage in the two windings reaches a predetermined value is called differential relays. The relay is used to check the operation of feeder breaker and to trip all the breaker feeding fault in the event of feeder breaker fail to trip. The relation between time of operation and plug setting multiplier is plotted on a graph paper, and this is known as time/PSM graph. Study specialized technical articles, papers, and electrical engineering video courses. protective relays encounter several problems as revealed in . 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. Page 1 Numerical Relay MELPRO Series MODEL CBV2 - A02S1 COC4 - A02S1 OPERATION MANUAL 1 / 47 JEP0-IL9537...; Page 2 - Safety precautions - Before installation, operation, maintenance, and inspection, please be sure to read this instruction manual and all other attached documents thoroughly in order to work safely with the equipment. Such relays are also termed as microprocessor type protective relays. Electromagnetic Relay Definition: Electromagnetic relays are those relay which operates on the principle of electromagnetic attraction. The values that the relay must measure to perform its protection function have already been acquired and processed. 1 Programmability of Numerical Relays: A Busbar Protection Relay Serves as a Traditional RTU Casper Labuschagne, Schweitzer Engineering Laboratories, Inc., Pullman, WA, USA Izak van der Merwe, Eskom Resources and Strategy Division, Cape Town, South Africa Abstract -- Numerical relays have revolutionized protection, control, metering, and communication in power systems. 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. Get ideas for your own presentations. as Z or distance. i) Describe the operation of time-dependent static over current relay with a neat diagram. of Int. Comparison of reliability and availability between the two methods is complex as inter-dependency of elements of an application provided by separate relay elements needs to be taken into account. An essential component is the Real Time Operating System (RTOS) which ensures that the other tasks are executed when required, in the correct priority. Similarly, the amount of data that must be recorded is much larger, requiring larger storage. What is Relay? RAM serves for the purpose of retaining the input data to the Relay and processing the data during the compilation of algorithm. 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 relay was tested under different frequency values with no attention to load shedding as described before for frequency relays. Numerical relays perform many more functions than earlier generations of relays so testing them is more complex. This magnetic field moves the relay armature for opening or closing the connections. Typical functions that may be found in a numerical relay other than protection functions are described in this section. The Hardware part is briefly described below. 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. Digital Input / Communication Module: Numerical Relays are provided with serial and parallel ports for the interconnection with control and communication system of the substation. At low currents, high gain setting is used and at high currents low gain setting is preferred. Software: Numerical Relays are equipped with software to communicate with external device to program to Relay or one can program by navigating through the Relay Menu. the overcurrent relay exceeds a setpoint amount, the relay operates with or without an intended time delay and trips the associated circuit breakers . Figure 1, Figure 2 and Figure 3 show typical numerical relays, while Figure 4 and Figure 5 show typical numerical relay boards. Relay). 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 . Historically, electromechanical and static relays have been provided with fixed plug settings applied to the relay. The most attractive feature of such relay is that it works on FIFO (First In, First Out). Keywords: Transformer Protection – Magnetizing Inrush – Harmonic Restraint – Harmonic Blocking 2. INTRODUCTION Inrush or overexcitation conditions of a power transformer produce false differential currents that could cause differential relay misoperation. 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. Function parameters are usually displayed on the front panel of the relay and through an external communications port. The distinction between digital and numerical relays is particular to Protection. 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, it is sufficiently accurate for an operator to assess system conditions and make appropriate decisions. TMS320F28335 is a floating point Digital Signal Controller (DSC). Design & Principle NI 40/41 series relays are based on numerical microprocessor based technology. Ok, let’s start with introduction to numerical relays, then explaining their additional features and at the end to discuss important considerations regarding software, data management, etc.. Table 1 provides a list of typical functions available, while Table 2 summarises the advantages of a modern numerical relay over static relay equivalents. It is now possible to implement a substation automation scheme using numerical relays as the main hardware provided at bay level. Fault levels are significantly different on parts of the network that are energized under normal and emergency generation. They are used to time the delay open and delay close of contacts. operation reactor current is alw ay s arou nd 1pu an d . Single function devices. Manufacturer of Numerical Relays - Numerical Over Current Relay with Communication JNC 068 CAL, Numerical Over Current Relay with Communication JNC 068 C, Numerical Current & Auto Recloser JNC 268 and Numerical Unbalance Voltage Relay offered by JVS Electronics, Ahmedabad, Gujarat. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. ), Auxiliary protection functions (broken conductor, negative sequence, etc. 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. 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. Many functions previously implemented in separate items of hardware can then be included in a single item. Let a 12 bit unipolar A/D converter be used for sampling current signal. Therefore, the time of operation of relay would vary as V/I i.e. Memory:Memory is of two types. By using DSP as the relay’s processor, the relay is capable of meeting the fundamental Tell us what you're thinking... we care about your opinion! 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. ABB has delivered numerical relays worldwide. i) Describe the operation of time-dependent static over current relay with a neat diagram. Share yours for free! On the other hand, the relay has to be dependable as well. Relay Definition: The relay is the device that open or closes the contacts to cause the operation of the other electric control. 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. As the relay current does not increase further, there would not be any further reduction in time of operation in the relay. 1 thought on “Basic Principle of Relay Operation” SystemProtection. 3. Modern numerical relay protection scheme offers multi-function and multiple characteristics, and other several advantages. The continuing reduction in the cost and size of microprocessors, memory and I/O circuitry leads to a si… The time is called operation time. Conf. 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. These can then be printed or uploaded to the user’s database facilities. One solution is to increase resolution i.e. 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 . 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. Electromechanical and static relays have fixed wiring and the setting is manual. Event and Disturbance Recording is a must feature for a digital relay because these data are used for troubleshooting any event. They use one or more digital signal processors (DSP) optimised for real time signal processing, running the mathematical algorithms for the protection functions. 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. 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. The REJ 523 is based on a microprocessor environment. Principle of operation. Principle of Operation: With increasingly complicated facilities, more and more timers and self-holding circuits are added to the outside of a protection relay as a condition for operation, closing, or warning of a breaker. Numerical relays are based on the use of microprocessors. A Relay is an electromechanical device that can be used to make or break an electrical connection. 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. It is placed in the motor circuit in such a way that the current to the motor flows through its poles. – Construction and Working Principle, Binary Coded Decimal or BCD Number Explained, What is UPS? The present protection technique used is unable to ensure selectivity and speedily operation for the faults appearing on the entire protected line. Magnitude of peak voltage VP is given by an approximate formula (based on experimental results) V. P = 2 √2V K (V F-V K) Where V F = If (R. CT + 2R. A typical Numerical Relay can store as much as 520 Events and 50 Disturbances. Operation of Electromagnetic -attraction Relay:Figure shows a typical electro mechanical relay. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. 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. JNC 154 is a numerical local breaker backup relay. Use of the relay The overcurrent relay REJ 523 is intended for selective short-circuit protection in medium voltage distribution networks but can also be used for protection of generators, motors and transformers. Nice Article.Relays are used to provide time delay functions. Different configurations may require different relay settings to maintain the desired level of network protection. Numerical relays are the product of the advances in technology from digital relays. The design of CT(s), which never Practical experience indicates that numerical relays are as reliable as relays of earlier technologies. A MATLAB model of a frequency relay was detailed before . For more information on the different types of disturbance recording, read this technical article. The ADR241A continuously monitors all phases and earth current, Numerical relay are embedded with specialized digital signal processor (DSP) as the computational hardware . As with earlier generations of relays and according to market segmentation, manufacturers offer different versions, each with a different set of functions. April 28, 2018 at 3:28 pm . Most of us are aware of Electromagnetic Relays and Static Relays but most us may not be well acquainted with Numerical Relay. Numerical Relays are equipped with software to communicate with external device to program to Relay or one can program by navigating through the Relay Menu. Reference // Network Protection & Automation Guide by Alstom Grid. 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. Related Post: Solid State Relay (SSR) – Types of SSR Relays – Construction & Operation Construction of a Relay. An input voltage is applied to the coil mechanism. However, considering the order of difference between current magnitudes in case of fault and load, there can be loss of accuracy during metering applications. Low pass filter is incorporated in the input module to eliminate any noise single induced in the line due to corona or induction effect of nearby high voltage line. Based om this, the time relays are classified as, 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. 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. The typical architecture of a numerical relay is shown in Figure 6. 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. ... the angle through which the disc is to rotate for the operation of the relay is directly proportional to voltage V. Thus in this type of relay … Also numerical relays have functionality that previously required separate equipment. 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. 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. Many numerical relays have the facility for time synchronisation from an external clock. The content is copyrighted to EEP and may not be reproduced on other websites. 1 thought on “Basic Principle of Relay Operation” SystemProtection. It must work at high speed, use low voltages, yet be immune to conducted and radiated interference from the electrically noisy substation environment. 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. Page 1 Numerical Relay MELPRO Series MODEL CBV2 - A02S1 COC4 - A02S1 OPERATION MANUAL 1 / 47 JEP0-IL9537...; Page 2 - Safety precautions - Before installation, operation, maintenance, and inspection, please be sure to read this instruction manual and all other attached documents thoroughly in order to work safely with the equipment.