The unwanted operation of the bus differential relay will have the similar effect as simultaneous faults on all power system elements connected to the bus. ... ・16 kinds of operation time characteristics and wide setting range of time multiplier are available for overcurrent protection element. In other words, the time of operation of the relay depends upon plug setting multiplier. 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. The relay is an electromechanical switch used as a protecting device and also as a controlling device for various circuits, equipments, and electrical networks in a power system. Separate terminals are provided for the analog and digital inputs. Numerical relays are natural developments of digital relays due to advances in technology. The time is called operation time. 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. of starts/reaccelerations, total running time, The different software versions in existence x the differences between each version. Alternatively, a variable gain amplifier can be used along with the A/D converter. A self-s upervision system continuously monitors the operation of the relay. Every relay manufacturer with numerical relays will publish the transient dimensioning factor for their relay operation based on a range of X/R ratio . However, considering the order of difference between current magnitudes in case of fault and load, there can be loss of accuracy during metering applications. Figure 1, Figure 2 and Figure 3 show typical numerical relays, while Figure 4 and Figure 5 show typical numerical relay boards. The ADR241A is a 3 OC and 1 EF relay with Instantaneous high set and programmable output to simplify feeder protection wiring. One solution is to increase resolution i.e. 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. Numerical local breaker backup relay jnc 154. Based om this, the time relays are classified as, Different configurations may require different relay settings to maintain the desired level of network protection. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. Modern numerical relay protection scheme offers multi-function and multiple characteristics, and other several advantages[9]. 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. Sir please clear that,in Higher over current setting calculation,how you have considered relay plug setting is 2.5? 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. Consider a hypothetical case where in maximum load current is 100 A and maximum fault current is 20 times this load current i.e. If only one or two phases are lost, the VT failure algorithm can be accomplished. 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. The operation of the numerical relay depends upon the function of the (Peripheral Interface Controller) PIC microcontroller signal. Hence, the characteristic is inverse in the initial part, which tends to a definite minimum operating time as the current becomes very high. The magnetic field then uses for opening and closing the switch and for performing the mechanical operation. The emphasis is on electromagnetic force causing the mechanical operation of the relay. System operators normally require knowledge of the state of all circuit breakers under their control. It is now possible to implement a substation automation scheme using numerical relays as the main hardware provided at bay level. 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. Software problems are minimized by rigorous use of software design techniques and the ability to download updated software. 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. Numerical relay are 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. Hardware for Metering: In principle, the hardware setup discussed above can be used for both measurement and protection function. A thermal overload relay works in the principle of electro-thermal properties in a bimetallic strip. Many functions previously implemented in separate items of hardware can then be included in a single item. Principle of operation. CPU: CPU stand for Central Processing Unit which is responsible for the processing of protection algorithms and digital filtering. Fault levels are significantly different on parts of the network that are energized under normal and emergency generation. Therefore, a simple solution would be to keep metering and protection functionality separate. The timing of pulse can be changed by the user. The first protection devices based on microprocessors were employed in 1985. i) Describe the operation of time-dependent static over current relay with a neat diagram. Distance Relay – In this relay operation depends on the ratio of the voltage to the current. Principle of operation. Principle of Operation: April 28, 2018 at 3:28 pm . L + R. STAB + R. relay) Metrosil required if V. P > 3kV 2000 A. Introduction and Architecture of Numerical Relay. 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. It is a type of a magnetic switch which uses the magnet for creating a magnetic field. 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. Instantaneous Relays – These relays employed after a small time duration from the incidence of the current or other quantity resulting in operation. Each relay element is in software so with modular hardware the main signal processor can run a vast variety of relay elements. 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. This resolution may be inadequate for metering purposes. … It detects the intolerable or undesirable condition with an assigned area and gives the commands to the circuit breaker to disconnect the affected area. Numerical relays are based on the use of microprocessors. A single Numerical relay can monitor multiple parameters like current, voltage, Frequency, onset time, offset time, etc. 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… Analogue signals are converted to digital form using an A/D converter. 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. value of line to line fault current for the operation of the relay is: Reply. The implementation of logic in a relay is not new, as functions such as intertripping and auto-reclose require a certain amount of logic. Numerical Relay; Classification based on Actuating Signals. When the circuit of the relay senses the fault current, it energises the electromagnetic field which produces the temporary magnetic field. Reference // Network Protection & Automation Guide by Alstom Grid. However I am going to define a Numerical Relay. The ADR241A continuously monitors all phases and earth current, 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. Get ideas for your own presentations. 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 alternative is to provide each input with a dedicated A/D converter and logic to ensure that all converters perform the measurement simultaneously. The internal communications bus links the hardware and therefore is a critical component in the design. Study specialized technical articles, papers, and electrical engineering video courses. According to timing characteristic, the relays can be divided into the following classes. The output from the Filter is then fed to. The output from the Filter is then fed to Sample and Hold (S/H)circuit. The standard normally used is an IRIG-B or IEEE 1588 signal, which may be derived from several sources including a GPS satellite receiver. 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. Also the operator can program the relay remotely with a group of settings if required. In principle, the hardware setup discussed above can be used for both measurement and protection function. Incorrect results are then obtained. -Working & Types of UPS Explained. Learn about power engineering and HV/MV/LV substations. 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. It is placed in the motor circuit in such a way that the current to the motor flows through its poles. [-09 – Rev01] Argus 7 Numerical Check Synchronism Relay Section 1 – Page 4 DESCRIPTION OF OPERATION Each of the status inputs can be programmed to … 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. Traditional electromechanical and static protection relays offers single-function and single characteristics. – Construction and Working Principle, Binary Coded Decimal or BCD Number Explained, What is UPS? The content is copyrighted to EEP and may not be reproduced on other websites. 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. Other software depends on the function of the relay, but can be generalized as follows: The relevant software algorithm is then applied. The main operation of a relay comes in places where only a low-power signal can be used to The relay algorithm is a set of mathematical operations implemented in a low level program (C/C++ compiler). Modern numerical relays will have comprehensive self monitoring to alert the user to any problems. The most attractive feature of such relay is that it works on FIFO (First In, First Out). ), Communications built in (serial, Ethernet, teleprotection, etc. Tell us what you're thinking... we care about your opinion! The principle of operation of the simulated numerical relay is based on the IEEE Standard Inverse-Time Characteristic Equations for Over-current Relays . The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. 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. Function parameters are usually displayed on the front panel of the relay and through an external communications port. A big difference between conventional electromechanical and static relays is how the relays are wired. The memory can easily be expanded to allow storage of a greater time period of input data, both analogue and digital, plus the state of the relay outputs. 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. This magnetic field moves the relay armature for opening or closing the connections. Minimum voltage setting prevents mal-operation of the relay when fuse failure/MCB tripped conditions. Operation of Electromagnetic -attraction Relay:Figure shows a typical electro mechanical relay. INTRODUCTION Inrush or overexcitation conditions of a power transformer produce false differential currents that could cause differential relay misoperation. The relay will now use 30% of this ITOTto derive its actual restraint current, i.e. Conf. The Hardware part is briefly described below. Practical experience indicates that numerical relays are as reliable as relays of earlier technologies. 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. 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. The relation between time of operation and plug setting multiplier is plotted on a graph paper, and this is known as time/PSM graph. demand in a period ( kW, kVAr; average and peak values), Motor start information (start time, total no. As the power of microprocessors continues to grow and pressure on operators to reduce costs continues, this trend will continue. ROM is also needed for storing Event and Disturbance data. Characteristic Angle Setting: The Relay Characteristic Angle RCA is given in relay Phase fault protection settings. Electro Mechanical Relay • Memory of previous Fault records, Actual Value of Fault Current, etc. 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. Memory:Memory is of two types. A typical Numerical Relay can store as much as 520 Events and 50 Disturbances. 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. 1 thought on “Basic Principle of Relay Operation” SystemProtection. ... and apply multifu nctional numerical relay s for HV shun. 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. 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. This ensures that truncation and numerical precision problems associated with finite precision arithmetic do not cause significant loss of accuracy. The argument against putting many features into one piece of hardware centres on the issues of reliability and availability. Numeric relays are programmable rel… In relays the time between instant of relay operation and instant at which tripping of contacts takes place can be controlled. the overcurrent relay exceeds a setpoint amount, the relay operates with or without an intended time delay and trips the associated circuit breakers [13]. The distinction between digital and numerical relays is particular to Protection. protective relays encounter several problems as revealed in [2]. ... 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 … A numerical relay can record all of these parameters and hence be configured to send an alarm when maintenance is due. A good design guideline is to choose a processor with double the number of bits of A/D converter. 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. The range is (-95 to +95 Degrees). Note that not all functions are found in a particular relay. However, during the change from one setting to another, loss of information can take place. 2000 A. ABB has delivered numerical relays worldwide. 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