Also in motor protection relays, additional information pertaining to positive sequence, negative sequence, equivalent current and difference current (between phases) is available. The values that the relay must measure to perform its protection function have already been acquired and processed. These are given below. Hence for complex, reliable, multi-functional requirement numerical relays shall be used. 1 shows a simplified functional block diagram for a numerical protective relay. The ADC’s conversion time is also checked to see if it is within the specification. CT and PT of lower VA burden are sufficient. 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. A big difference between conventional electromechanical and static relays is how the relays are wired. Relay calculates the differential current (Id) and restraining current (Ir) per phase. The differential characteristics define the … The numerical relay is one of electrical base of the software protection against to detect the natural & unnatural fault in the electrical machinery. Waveform record stores the analogue and digital channel values during the relay operation or on demand. Block diagram of a digital relay ... A numerical relay commonly found in the power distribution systems is used for testing. This also verifies the analogue data acquisition system including multiplexer, programmable gain amplifier and ADC. Description and definition. are required to construct this protective relay.. Whenever any set-point is changed, the check-sum of the set-points is calculated from the contents of the EEPROM. The voltage inputs of the relay are scaled down from the nominal voltage to a low level determined by the ADC (analogue-to-digital converter) input range. Fig 27.4 shows the functional block diagram of a digital relay. 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. Multi-functions like protection, control, monitoring and measuring are available today in numeric power system protection devices. The REJ 523 is based on a microprocessor environment. The filtered signals are multiplexed using an analogue multiplexer and amplified, if needed, by using a programmable gain amplifier. Numerical relays can adapt themselves to different system conditions by monitoring the operat-ing quantities from the digital inputs of the relay. On the other hand, in the modern protection schemes, smart protection relays support more functions in one piece of device. The block diagram is shown in the fig above. Communication capability makes the numerical protection system more intelligent and pro-vides valuable information to the user. It is also called numerical relay. Figure 4, shows the block diagram of the developed distance relay. Relays are Output module 6. 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. Thus the cost of CT and PT is reduced. Thus improvements in numerical relays can be upgraded at site without despatching the relay to the manufacturer which reduces the relay downtime. 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. Flash memory is used for storing the programme and RAM (random access memory) is used for temporary storage of … The fault record gives all information about the fault to the operating personnel. 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). The primary method of reducing unwanted induced AC voltage is to bypass these voltages to ground with capacitors. The relay switchover from one group setting to the other during the running condition. Conventional electromechanical and static relays are hard wired relays.Their wiring is fixed, only their setting can be manually changed. The high powered analog signals are stepped down with current tran… The schematic of a generalized numerical relay structure is shown in Figure 1 [4], [5]. Knowledge is an ocean . Numeric relays are programmable rel… The analog input filter is used to filter the AC components of the waveforms. 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 flash ROM contents are checked by calculating the check-sum and comparing it with the pre-computed and stored check-sum. The ability to detect and correct a failure before the protection system has to operate is in contrast to the traditional protection system wherein a relay failure remains undetected until it fails to operate correctly during an event or until the next maintenance test. >LED reset NO 2. • Digital input subsystem. In numerical relay data storage is done in three formats, i.e. 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. be used only in the Numerical relays. Traditionally, electromechanical and static protection relays offered single-function, single characteristics, whereas modern numeric protection offers multi-function and multiple characteristics. Recommended reading: IEC 61850 for digital substation automation systems, IEC 61850 for digital substation automation systems. Digital input/Communication module Input Module The Power system operates with analog parameters. Once the through fault current is above the set value, the relay bias automatically increases to facilitate greater stability for through fault condition. Flash memory is used for storing the programme and RAM (random access memory) is used for temporary storage of variables, target information and oscillography. The following cost reduction benefit the consumer: Numerical relays are tested as per IEC 255-5 for dielectric, impulse voltage and insulation resistance. VT/CT supervision. Thank you Edward. This record gives the nature of fault waveforms (transient) and instantaneous values, etc. In a static relay, the measurement is performed by static councils. 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. 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. Some protections also offer adaptable characteristics, which dynamically change the protection characteristic under different system conditions by monitoring the input parameters. The first protection devices based on microprocessors were employed in 1985. Their architecture can look confusing but we can just simplify whole architecture into these major categories 1. 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. Numerical Relay Is Also A Digital System, Which Is Concisely Communicating With Substation Automation. Protection is enhanced due to their complex, multiple protection characteristic. Fig.1. A number of extra quantities can be derived from the measured quantities, depending upon the input signals available. The standard ratings for protective relays are normally 5 A and 110 V, 50 Hz. 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. It helps you. Please keep it up . The design of the relay input, output and power supply circuits must incorporate filtering to reduce EMI (electromagnetic interference). 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. Connection Diagram Current Input Voltage Input Binary Input Factory Settings: 1. Communication makes the relay more intelligent and the operating personnel can set the relay and also download the fault information. 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. Multiplexer and Analog to digital converter 5. 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. It is also possible to upload the revised software to the relay at site without sending the relay back to the manufacturer. What is idmt relay: The IDMT relays are protection relays. Learn about power engineering and HV/MV/LV substations. 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. Electromechanical and static relays have fixed wiring and the setting is manual. 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. Very informative article! 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. Since this method involves smoothening, the operation is slow. This adds to savings in wiring material and labour. Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. Power supply voltages and ground are connected to the analogue input channels of the multiplexer and checked against warning and failure thresholds. Some relays can also give the energy meter function. What Is Numerical Relay. 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. 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. Working Principle of Over Current Relay. Well written in broken down sections. 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