Memory 4. The analogue signal inputs (voltage and current), contact status inputs and communication circuits are conditioned and protected to withstand the harsh electrical and environmental conditions of the sub-station and power plant. Numerical relays carry out the processing of input quantities using a digital technique. Relay calculates the differential current (Id) and restraining current (Ir) per phase. Fig 27.4 shows the functional block diagram of a digital relay. Block diagram of numerical relay have encouraged the design and development of microprocessor based protective relays are their economy, compactness, reliability, flexibility and improved performance over conventional relays. Some examples of these adaptions are: Adaption #1 – In motor protection relay, different settings can be adapted for the starting condition and running condition. The primary method of reducing unwanted induced AC voltage is to bypass these voltages to ground with capacitors. Multiplexer and Analog to digital converter 5. Numerical relay is the relay in which the measured AC quantities are sequentially sampled and converted into numerical data that is mathematically and/or logically processed to make trip decisions. Fig.1. Simplified functional block diagram for a numerical protective relay 3. The standard ratings for protective relays are normally 5 A and 110 V, 50 Hz. The software provided in a numerical relay is commonly organized in a series of tasks operating in real time. The relay switchover from one group setting to the other during the running condition. Communication capability makes the numerical protection system more intelligent and pro-vides valuable information to the user. Once the through fault current is above the set value, the relay bias automatically increases to facilitate greater stability for through fault condition. Knowledge is an ocean . All the events are time-stamped. Waveform record stores the analogue and digital channel values during the relay operation or on demand. These records can also be converted into the ‘comtrade’ format, with which data can be played back into the relay using the digital test system. The block diagram of the inverse-time overcurrent relay is shown in the figure. The voltage and current data are derived using the power system simulator (PSB power system block set for SIMULINK/MATLAB). Fault record gives the complete information about the fault, i.e. Wiring Diagram For A 12v 40 Amp Relay. 1: Block Diagram of Numerical Relay Description: The microprocessor based relay works on numbers that quantities value of signal its works on numbers so that’s why it’s known as “Numerical Relay” In which fig CT/PT are used to sense the current and voltage of … >Manual Close 4. Working Principle of Over Current Relay. The 3-Ø voltage and current signals are analog in nature. As CTs and VTs used for protection functions may have a different accuracy specification than those used for metering functions, such data cannot be sufficiently accurate for tariff purposes. Contact inputs and outputs, user inter-face (keyboard and liquid crystal display) and the serial communication ports (RS-232 and RS-485) are interfaced to the host processor. And the quantizer will sample the output in the form of discrete (step wise). The electro-mechanical relay operates when operating torque/fence exceeds the restraining torque/force. Fig. Fig 2 shows a block diagram of numerical relay. 1 shows a simplified functional block diagram for a numerical protective relay. Communication between the processors is provided by the dual-ported memory. The RAM is tested by writing and reading a test pattern. Thus the cost of CT and PT is reduced. These may include: The accuracy of the measured values can only be as good as the accuracy of the transducers used (VTs, CTs, A/D converter, etc.). Modern numerical protection devices have multiple protection elements and this technique makes the cost of the relay comparable with that of electromechanical and static relays (discrete). However, it is sufficiently accurate for an operator to assess the system conditions and take appropriate decisions. This is the result of the huge development of computer technologies that are used in power system protection. Thank you very much. In a nutshell, in the conventional protection schemes, all primary equipment such as circuit breakers, CT/VTs and power transformers are connected to the secondary system using the hardwires. 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. Input Module 2. Auxiliary relays like Buchholz relay alarm/trip, and winding temperature alarm/trip contacts, which can be connected to relay as logic input and details of relay operation can be seen in the event log sheet. All these functions can be built into one relay, which will be very compact in size and also reduced weight. In a static relay, the measurement is performed by static councils. The values that the relay must measure to perform its protection function have already been acquired and processed. Numerical relays are provided with a metering function and separate panel mounted meters can be eliminated. Multi-functions like protection, control, monitoring and measuring are available today in numeric power system protection devices. 36 COST OF NUMERICAL RELAYS Modern numerical protection devices have multiple protection elements and this technique makes the cost of the relay comparable with that of electromechanical and static relays … Current and voltage transformers produce these relay input quantities and discussed in chapter 3.2. Thus the size of instrument panels is reduced, thereby resulting in further cost reduction. Similarly in distance relays fault location is also possible. I seek every opportunity to update my educational and experienced background. Thank you Edward. modern digital and numerical relays. The first numerical relays were released in 1985. Study specialized technical articles, papers, and electrical engineering video courses. Digital input/Communication module Input Module The Power system operates with analog parameters. The digital signal processor executes a variety of signal processing algorithms to estimate several parameters of the digitized voltage and current signals, and transfers them to dual-ported memory. Figure 4, shows the block diagram of the developed distance relay. CT and PT of lower VA burden are sufficient. These records can also be fed to the harmonic analyzer software to find out the harmonic content in the fault quantities. Flash memory is used for storing the programme and RAM (random access memory) is used for temporary storage of variables, target information and oscillography. >Block I» NO >Block le>> NO 3. Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. The multiplexed analogue signal is sampled and converted into digital data using the ADC. Adaption #2 – In transformer protection relay, the third slope is called the bias slope limit, which is used to afford greater stability and this can be achieved by monitoring the through fault current. Brief Introduction about Relay: RELAY: A Relay is a protection device that senses the fault in the circuit and gives a trip signal to the Circuit Breaker to isolate the faulty circuit. The flash ROM contents are checked by calculating the check-sum and comparing it with the pre-computed and stored check-sum. We know that most of the high end industrial application devices have relays for their effective working. VT/CT supervision. • A processor along with RAM (data scratch pad), main memory (historical data file) and power supply. Flash memory is used for storing the programme and RAM (random access memory) is used for temporary storage of … The relay hardware design includes a watchdog timer re-set circuit to take the processor through an orderly re-set should the programme get lost due to hardware/software glitches. The first protection devices based on microprocessors were employed in 1985. The filtered signals are multiplexed using an analogue multiplexer and amplified, if needed, by using a programmable gain amplifier. Simulink/MATLAB is used to model the distance relay components such as ADC and digital filters. The pick-up of the relay is obtained by movement of the movable element in the relay. The relaying voltage and currents are passed through an isolation transformer. From the set of possible values of the electric measures that feature the EP’s operation, PI The content is copyrighted to EEP and may not be reproduced on other websites. —W^ÞZñtÉç]îí¼>^ß[,ØVp¬ vŠöRC±¶\M5їƒQÖºÌ öTHuhDRî ¹«JXK²+Ÿ©#CR nG³ÃSÒ:‚­tV'O²ƒ%÷ò»å”±ÙM¥Ð2ùæd(pU¬'_çÞþõ@¿Å5 öÏ\Ðs*)ý&º‹YShIëB§*۝b2¨’ù¹qÆp?hyi'FE'ʄL. The design of the relay input, output and power supply circuits must incorporate filtering to reduce EMI (electromagnetic interference). Set-points are stored in the serial EEPROM and a copy of these set-points is also stored in the RAM for executing relay logic. C. Numerical Relay Fig 8: Block diagram of numerical relay Here, also the input is given as sine wave with the amplitude of 400V. The fault record gives all information about the fault to the operating personnel. It is therefore a simple task, The relay hardware and software are continuously monitored by the relay itself, Nowadays all protection relay manufacturers are trying, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! comparators – Block diagram of Numerical relays – Overcurrent protection, transformer differential protection, distant protection of transmission lines. A relay is generally suitable for temperature as per IEC 255-6 for storage at -25°C to +70°C, and for operation at -25°C to +55°C. for the control and operation of manufacturing process equipment and machinery. be used only in the Numerical relays. CPU 3. A relay is generally suitable for humidity as per IEC 68-2-3, for enclosure protection IP 52 as per IEC 529, for siesmic, shocks and bumps as per IEC 255-21 for Class 1 and for Class for vibration test as per IEC 255-21. You never get tired or exhausted . 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. Block Diagram of Numerical Relays / Digital Relay 59. Adaption #4 – In IDMTL relays, depending upon the system condition like the number of incomers and outgoing feeders, different settings can be selected and better protection can be achieved. The ADC’s conversion time is also checked to see if it is within the specification. The main components of numerical relay are- IEC 61850 based solutions are now supporting a full interoperability between intelligent electronic devices (IED) from different manufactures. JND 040 provides differential protection for power transformer. Whenever any set-point is changed, the check-sum of the set-points is calculated from the contents of the EEPROM. So a single intelligent device can support different functions such as protection, control, metering and fault recording. Very helpful article. • Digital output subsystem. Protective relay must be isolated from the high-voltage system but require current and voltage quantities proportional to those on the electric supply system. Following are some of the key tests to be conducted at various design phases of digital multi-function relays: Recommended reading: Commissioning of protection relays using test equipment and software, Commissioning of protection relays using test equipment and software. Thus improvements in numerical relays can be upgraded at site without despatching the relay to the manufacturer which reduces the relay downtime. Modern numerical relays have other additional functions like: Recommended reading: Mastering switchgear control circuits – AC/DC circuits and circuit breaker closing circuit, Mastering switchgear control circuits – AC/DC circuits and circuit breaker closing circuit. Modem power system protection devices are built with integrated functions. Output module 6. In motor protection relay, the instrumentation mode can also display motor status, time to trip (during abnormal condition), time to start (if the protection is locked out), the last starting time, last starting current, positive, negative, difference current values, etc. The more complex relay uses multi-processor architecture wherein the digital signal processor executes complex algorithm calculations and the host processor performs all the other tasks. Block diagram of a digital relay ... A numerical relay commonly found in the power distribution systems is used for testing. These are given below. >LED reset NO 2. Recommended reading: Testing protection IEDs in IEC 61850 based substation automation systems, Testing protection IEDs in IEC 61850 based substation automation systems. The measuring principles and techniques of conventional relays (electromechanical and static) are fewer than those of the numerical technique, which can differ in many aspects like the type of protection algorithm used, sampling, signal processing, hardware selection, software discipline, etc. The schematic of a generalized numerical relay structure is shown in Figure 1 [4], [5]. Overcurrent protection, earth fault protection, unbalance protection and stall protection cannot be set at a very sensitive level during start-up because the starting current will influence these settings. First generation numerical relays were mainly designed to meet the static relay protection characteristic, whereas modern numeric protection devices are capable of. Interesting reading: Fault event reconstruction using data pulled from intelligent electronic devices (IEDs), Fault event reconstruction using data pulled from intelligent electronic devices (IEDs). developed numerical protection systems. Connection Diagram Current Input Voltage Input Binary Input Factory Settings: 1. This relay f~rmerly is located at the Qislributi~n substati~n and The time-graded protection can also be implemented with definite time underimpedance relays. Numeric relays are programmable rel… The numeric relay can be called as a miniature computer as they both have similar hardware architecture with slight differences. Also, the communication capability of these devices facilitates remote control, monitoring and data transfer. Self-check feature improves the protection system reliability. The digital protective relay is a protective relay that uses a microprocessor to analyze power system voltages, currents or other process quantities for the purpose of detection of faults in an electric power system or industrial process system. Very informative article! On the other hand, in the modern protection schemes, smart protection relays support more functions in one piece of device. This record gives the nature of fault waveforms (transient) and instantaneous values, etc. Modern numerical protection devices offer innumerable features as compared to static and electromechanical protection system. Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. Utilities are now demanding IEC 61850 capabilities available in any substation related hardware or software. Please keep it up . These scaled signals are filtered by using a low-pass filter to prevent a liasing of the high-frequency components into the fundamental frequency component. The differential characteristics define the … Numerical Relay Is Also A Digital System, Which Is Concisely Communicating With Substation Automation. >CB Ready NO 5. • Digital relay/ Numerical relay consists of functional block diagram • Analog input subsystem. The processed data can be accessed through the relay communication port. The facts about numerical relays that every electrical engineer should know, Electrical engineer, programmer and founder of, Additional Functionality of Numerical Relays, filtering to reduce EMI (electromagnetic interference), Sequence quantities (positive, negative, zero), Maximum demand in a period (kW, kvar; average and peak values), Motor start information (start time, total number of starts/re-accelerations, total running time), Circuit breaker conditions monitoring including programmable digital output and inputs for various logic build generally for blocking. A faster method is phase splitting the wave ... relay has a microprocessor, it lacks the attributes of a digital/numeric relay, and hence the term “microprocessor Relay is tested for high frequency disturbance, fast transient, electrostatic discharge, radio frequency and impulse as per IEC 1000-4 and ANSI 37.90. fault current magnitude, type of fault, fault phase details, etc. Some protections also offer adaptable characteristics, which dynamically change the protection characteristic under different system conditions by monitoring the input parameters. In the numerical relay the analog signals from CT & PT are processed through the series of hardware blocks and finally supplied to the computer/processor in a digital form where the software algorithm processes the digital signal and takes decision about the trip signal. It should be suitable for 2 kV dielectric voltage, 5 kV impulse voltage and insulation resistance > than 1000 M-ohms. Recommended reading: IEC 61850 for digital substation automation systems, IEC 61850 for digital substation automation systems. A number of extra quantities can be derived from the measured quantities, depending upon the input signals available. 2 Protection installations – principles 2.1 Operational block diagram of the protection installations PI and EP form together an automatic protection system, which is an automatic system in open circuit. The host processor receives these parameters from the dual-ported memory and per-forms relay logic and other timing functions to generate appropriate trip or alarm output signals. In an over current relay or o/c relay the actuating quantity is only current.There is only one current operated element in the relay, no voltage coil etc. The relay has 32 PSL timers could be conveniently configured in PSL, setting or from the relay front panel. The main component is the real time operating system (RTOS) whose function is to ensure that other tasks are executed as and when required on a priority basis. The most important self-diagnostic functions implemented in digital multi-function relays are detailed below. The records can also be manually triggered and viewed to verify the phase relationship during commissioning. If possible , I might also contribute . Well written in broken down sections. Numerical relays can adapt themselves to different system conditions by monitoring the operat-ing quantities from the digital inputs of the relay. Overcurrent Relay Technical Reference Manual 3. TYPICAL BLOCK DIAGRAM OF NUMERICAL PROTECTION RELAY • Typical block diagram • Hardware and software architecture • Sampling interval • Extension of capabilities of relays in numerical design • From individual protection relays to a complete protection management system • Structure of the Intelligent Electronic Device (IED) Electromechanical and static relays have fixed wiring and the setting is manual. The relay user can also make custom built logic by using internal elements and inputs, i.e. fault record, event record and waveform record. Protection is enhanced due to their complex, multiple protection characteristic. This also verifies the analogue data acquisition system including multiplexer, programmable gain amplifier and ADC. The check-sum is calculated as the modul-256 sum of all the bytes. In numerical relay data storage is done in three formats, i.e. It can be seen that a digital relay consists of: Analog input subsystem Digital input subsystem Digital output subsystem A processor along with RAM (data scratch pad), main memory (historical data file) and power supply. It is also possible to calculate the relay operating time and breaker operating time. The numerical relay is one of electrical base of the software protection against to detect the natural & unnatural fault in the electrical machinery. with time stamping. An iron core is surrounded by a control coil. In simple Inverse definite minimum time lag (IDMTL) overcurrent and earth fault relays, multiple characteristics like NI, VI, El, LTI and DTL characteristics are available in relay and the required characteristics can be selected at site. This is perhaps the most obvious and simplest function to implement, as it involves the least additional processor time. 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