Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. The most important self-diagnostic functions implemented in digital multi-function relays are detailed below. are required to construct this protective relay.. Very helpful article. 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. Thus the cost of CT and PT is reduced. This also verifies the analogue data acquisition system including multiplexer, programmable gain amplifier and ADC. Tell us what you're thinking... we care about your opinion! 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. What is idmt relay: The IDMT relays are protection relays. Relay calculates the differential current (Id) and restraining current (Ir) per phase. Hence for complex, reliable, multi-functional requirement numerical relays shall be used. A number of extra quantities can be derived from the measured quantities, depending upon the input signals available. The number of protective relays and auxiliary relays are reduced. The relay user can also make custom built logic by using internal elements and inputs, i.e. IEC 61850 based solutions are now supporting a full interoperability between intelligent electronic devices (IED) from different manufactures. 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. 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. Figure 1 – Block diagram of numerical relay Communication between the processors is provided by the dual-ported memory. Utilities are now demanding IEC 61850 capabilities available in any substation related hardware or software. For example, we have the following protections in numerical relays in-built into one relay. Memory 4. This is the result of the huge development of computer technologies that are used in power system protection. 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. The block diagram of the inverse-time overcurrent relay is shown in the figure. >Manual Close 4. The 3-Ø voltage and current signals are analog in nature. Recommended reading: Testing protection IEDs in IEC 61850 based substation automation systems, Testing protection IEDs in IEC 61850 based substation automation systems. Adaption #3 – In distance relays, for different system configurations like parallel feeder in, and parallel out and grounded, different settings can be adapted for this condition. 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. Relay is tested for high frequency disturbance, fast transient, electrostatic discharge, radio frequency and impulse as per IEC 1000-4 and ANSI 37.90. Power supply voltages and ground are connected to the analogue input channels of the multiplexer and checked against warning and failure thresholds. I am a retired Engineering Consultant. Waveform record stores the analogue and digital channel values during the relay operation or on demand. Overcurrent and earth fault protection, and temperature protection. Fig 2 shows a block diagram of numerical relay. 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. 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 … Fault record gives the complete information about the fault, i.e. Output module 6. Numeric relays are programmable rel… Although a separate high-end communication system is available today for numerical relay data communication and control, a simple communication system is also possible for remote control and monitoring using telephone line as a communication medium. Thus the size of instrument panels is reduced, thereby resulting in further cost reduction. Need of Programmable Logic Controllers: Programmable logic controllers are solid state system designated to perform logic functions previously accomplished by components such as electromechanical relays, drum switches, Mechanical timers/counters etc. The schematic of a generalized numerical relay structure is shown in Figure 1 [4], [5]. The PSL imposes no delay on logic throughput, using concurrent processing being used instead of sequential equations and avoiding any logic ‘race’ issues. The main components of numerical relay are- 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. I seek every opportunity to update my educational and experienced background. So a single intelligent device can support different functions such as protection, control, metering and fault recording. The multiplexed analogue signal is sampled and converted into digital data using the ADC. Traditionally, electromechanical and static protection relays offered single-function, single characteristics, whereas modern numeric protection offers multi-function and multiple characteristics. Current and voltage transformers produce these relay input quantities and discussed in chapter 3.2. Multi-functions like protection, control, monitoring and measuring are available today in numeric power system protection devices. This record gives the nature of fault waveforms (transient) and instantaneous values, etc. Also in motor protection relays, additional information pertaining to positive sequence, negative sequence, equivalent current and difference current (between phases) is available. 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. The block diagram is shown in the fig above. 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. However, it is sufficiently accurate for an operator to assess the system conditions and take appropriate decisions. This check-sum is then compared with the calculated check-sum of the set-points stored in the RAM every time a set-point task is executed. VT/CT supervision. The REJ 523 is based on a microprocessor environment. The numerical relay is one of electrical base of the software protection against to detect the natural & unnatural fault in the electrical machinery. Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. These are given below. Nice to see and read your articles . This is perhaps the most obvious and simplest function to implement, as it involves the least additional processor time. Well written in broken down sections. 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! All these functions can be built into one relay, which will be very compact in size and also reduced weight. CPU 3. Working Principle of Over Current Relay. >Block I» NO >Block le>> NO 3. Very useful article, and well written. Thank you very much. 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. The ADC’s conversion time is also checked to see if it is within the specification. These records can also be fed to the harmonic analyzer software to find out the harmonic content in the fault quantities. Simulink/MATLAB is used to model the distance relay components such as ADC and digital filters. Fig. The first protection devices based on microprocessors were employed in 1985. Similarly in distance relays fault location is also possible. Some protections also offer adaptable characteristics, which dynamically change the protection characteristic under different system conditions by monitoring the input parameters. The differential characteristics define the … The following sections cover relay hardware, relay software, multiple protection characteristics, adaptive protection characteristics, data storage, instrumentation feature, self-check feature, communication capability, additional functions, size and cost-effectiveness. First generation numerical relays were mainly designed to meet the static relay protection characteristic, whereas modern numeric protection devices are capable of. A big difference between conventional electromechanical and static relays is how the relays are wired. An iron core is surrounded by a control coil. So useful article Edvard, it always adds new information to our experience in the field of protective relays and power transmission substations in general. The relay measures the line current of each phase from each of the windings of the transformer. Numerical relays carry out the processing of input quantities using a digital technique. Also, the communication capability of these devices facilitates remote control, monitoring and data transfer. Not as active as I used to but will use the information from your site to assist when I am visiting my homeland, in addition to local colleges in Ontario. Fig 27.4 shows the functional block diagram of a digital relay. 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. Flash memory is used for storing the programme and RAM (random access memory) is used for temporary storage of variables, target information and oscillography. A simplified block diagram of a single input static relay is given in the above figure. The first numerical relays were released in 1985. 1 shows a simplified functional block diagram for a numerical protective relay. Other components such as varistors, chokes and ferrite beads, are also applied to suppress surge voltages and EMI. 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. —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. Description and definition. The relay has 32 PSL timers could be conveniently configured in PSL, setting or from the relay front panel. 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. Pre-Configured Matching Unit, Retrofit solution for Microshield Overcurrent relay (MSOC), Brochure (English - pdf - Leaflet) Pre-Configured Matching Unit, The solution to mitigate risk and save costs on relay upgrades, Flyer (English - pdf - Leaflet) This adds to savings in wiring material and labour. 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.). P14D Functional Block Diagram • Digital output subsystem. Block diagram of a digital relay ... A numerical relay commonly found in the power distribution systems is used for testing. 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. The relay switchover from one group setting to the other during the running condition. 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. 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. On the other hand, in the modern protection schemes, smart protection relays support more functions in one piece of device. A digital protective relay may also be called a "numeric protective relay". Numerical Relay Is Also A Digital System, Which Is Concisely Communicating With Substation Automation. Multiplexer and Analog to digital converter 5. Electromechanical and static relays have fixed wiring and the setting is manual. CT and PT of lower VA burden are sufficient. Fig.1. The first protection devices based on microprocessors were employed in 1985. The processed data can be accessed through the relay communication port. The high powered analog signals are stepped down with current tran… • A processor along with RAM (data scratch pad), main memory (historical data file) and power supply. comparators – Block diagram of Numerical relays – Overcurrent protection, transformer differential protection, distant protection of transmission lines. The size of the numerical relays is much less as compared to that of electromechanical and static relays due to the multi-functionality approach of the former. It should be suitable for 2 kV dielectric voltage, 5 kV impulse voltage and insulation resistance > than 1000 M-ohms. It is also possible to calculate the relay operating time and breaker operating time. Event record stores inside the relay all the changes taking place in the system like protection element, pick-up, and drop-off operation, output and input energization and setting change, etc. Thus improvements in numerical relays can be upgraded at site without despatching the relay to the manufacturer which reduces the relay downtime. 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. It is also possible to upload the revised software to the relay at site without sending the relay back to the manufacturer. 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. That the relay at site without sending the relay operating time and breaker operating time and separate panel meters. 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