record including with the graphs. Delay in operation: Easily provided The extra facilities in numerical relays may avoid the need for other measurement and control devices to be fitted in a substation. A digital protective relay may also be called a "numeric protective relay". The reset has been done by either pressing Reset with the following protocols. It means the LED reset itself and ), Communications built in (serial, Ethernet, teleprotection, etc. 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. Advantages of Numerical relays 1. However, Electromechanical Relays are still being used. RE: differences between static, digital, and numerical relays DiscoP (Electrical) 23 Mar 09 17:05. trip signal to the Circuit Breaker to isolate the faulty circuit. 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. The following are the various types of numerical relays, Your email address will not be published. The continuing reduction in the cost and size of microprocessors, memory and I/O circuitry leads to a si… The digital signal processor (DSP) in a numerical relay normally can handle both the relay protection function calculations and general management of the relay such as HMI and I/O. This calculation is repeated for all of the quantities of interest. One of the significant advantages of a solid state relay over an electromechanical relay is its response time (ability to turn on and turn off). 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. Binary Outputs are the Commands In Electromagnetic relays operating current flows through the coil. The argument against putting many features into one piece of hardware centres on the issues of reliability and availability. trip command given However, if the DSP is overloaded it cannot complete the protection algorithm calculations in the required time and the protection function is slowed. Also numerical relays have functionality that previously required separate equipment. 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. This paper discusses methods of analysing waveform recordings from numerical relays to diagnose power system events and confirm relay operations. VT supervision is made more complicated by the different conditions under which there may be no VT signal, some of which indicate VT failure and some occur because a power system fault has occurred. Following are the various protocols 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. No maintenance is needed like Logic functions are well suited to implementation using microprocessors. One relay can be used in many ways. Numerical Relays Advantages, Binary Inputs, Binary Outputs, Common Features, Digital Inputs, Digital Ouptputs, Latch LED, LED Configuration, Numerical Relay, Relay … Relays are compact in size and If suitable VTs are used, supervision of the VT/CT supplies can be made available. by the relay to breaker in the case of fault. Fault levels are significantly different on parts of the network that are energized under normal and emergency generation. A numerical relay can record all of these parameters and hence be configured to send an alarm when maintenance is due. 2. different Setting groups. any case relay fails to operate, it leads to crores rupees loss to the Many numerical relays have the facility for time synchronisation from an external clock. This relay has to be installed straight only and away from magnetic field. ), Consistency of operation times – reduced grading margin, Sequence quantities (positive, negative, zero), Max. To understand simply it is like a brain in our human Other software depends on the function of the relay, but can be generalized as follows: The relevant software algorithm is then applied. 2) Flexibility: We can modify its functional operation by changing codes in software. Front side of any Numerical Relays usually have the following components. θ is the angle by which S 2 lands S 1.If β 1 = β 2 =90 o, the comparator is called cosine comparator and if β 1 =0 and β 2 =180 o, it is a sine comparator. Different configurations may require different relay settings to maintain the desired level of network protection. Numerical relays, on the other hand, operate on digitized secondary signals. Unlike electromagnetic relays, these do not contain any moving parts and thereby serving all the benefits of static relays as well. The typical architecture of a numerical relay is shown in Figure 6. Note that not all functions are found in a particular relay. of starts/reaccelerations, total running time, The different software versions in existence x the differences between each version. It requires less wiring so it is not having complex architecture. It is also called numerical relay. Source(s): Basler Electric's BE1-11f FEEDER PROTECTION … microprocessor and programming software these relays work. Many functions previously implemented in separate items of hardware can then be included in a single item. Many complicated functions can be They are reliable. Any LED can be configured in two This property of multitasking is further strengthened on the account that the numerical system can accommodate different types of relay characteristics. Numeric relays are programmable relays. The implementation of logic in a relay is not new, as functions such as intertripping and auto-reclose require a certain amount of logic. Consists of no mechanical moving System operators normally require knowledge of the state of all circuit breakers under their control. Study specialized technical articles, papers, and electrical engineering video courses. parts hence accurate operation. software discipline etc. It consists of one or more digital signal processors, some memory, digital and analogue input/output (I/O), and a power supply. One of the many advantages numerical relays provide is the ability to save the settings in a file by downloading them with communications software as shown in Figure 2. Function parameters are usually displayed on the front panel of the relay and through an external communications port. configured LED picks up as soon as the indication exists and remains picked up them and also with HMI through modem. Binary Inputs gives the status of The software provided is commonly organised into a series of tasks operating in real time. 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. Users can configure relay according to their system requirement. 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 various equipment to the relay in the form of 1’s and 0’s, for e.g. It may be inconvenient to download the record immediately, so facilities may be provided to capture and store a number of disturbances. Also the operator can program the relay remotely with a group of settings if required. 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. RELAY: A Relay is a protection device that senses the fault in the circuit and gives a The Advantages of Electromechanical relays are-They are quick acting and can be reset fast. These relays are useful for protection of 3-phase AC induction motors against various hazards. The numeric relays are mostly used in the generating stations and substations for automated protection. This session gives insights on Numerical relay and its advantages over electro mechanical relays. Relays are available from various companies such as Siemens, ABB, Schnieder Electric, Alstom, Texas instrumentations, etc. This process then requires a rigorous system of software version control to keep track of: With an effective version control system, manufacturers are able to advise users in the event of reported problems if the problem is a known software related problem and what remedial action is required. 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. used. The values that the relay must measure to perform its protection function have already been acquired and processed. Electromechanical, have been gradually been replaced by Static and then by Numerical Relays. And the simulation results show the advantages of the proposed method in reducing the time needed by the relay to clear the electrical fault. Get numerical relays at best price with product specifications. 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. Software problems are minimized by rigorous use of software design techniques and the ability to download updated software. Firstly the quantities of interest are determined from the information in the data samples. It is now possible to implement a substation automation scheme using numerical relays as the main hardware provided at bay level. Numerical relays are natural developments of digital relays due to advances in technology. 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. Circuit breaker status is given by BI is either ON/OFF. However, it is sufficiently accurate for an operator to assess system conditions and make appropriate decisions. Advantages of Numerical Relays: Numerical relay consists of many functions in one relay thus replace many traditional relays with one. relays is communication between relays and other equipment in the network is Incorrect results are then obtained. Modern numerical relays will have comprehensive self monitoring to alert the user to any problems. (1 relay can be used as over current only for under voltage we use another relay). This uncomplicated, serial These are the advanced version of relays by using Numerical relays perform many more functions than earlier generations of relays so testing them is more complex. Frequent configuration is not needed. Modern numerical relay protection scheme offers multi-function and multiple characteristics, and other several advantages[9]. Similarly, the amount of data that must be recorded is much larger, requiring larger storage. Numerical relay is flexible, using software and the hardware with slight modifications in 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. Advantages of Numerical relays: Compact Size: Electromechanical Relay makes use of mechanical comparison devices, which cause the main reason for the bulky size of relays. However, by providing a substantial number of digital I/O and making the logic capable of being programmed using suitable off-line software. In industrial and small distribution networks, this may be all that is required. The Latch As the power of microprocessors continues to grow and pressure on operators to reduce costs continues, this trend will continue. 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. Electro Mechanical Relay • Memory of previous Fault records, Actual Value of Fault Current, etc. 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. 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. This is often done using a Discrete Fourier Transform (DFT) and the result is magnitude and phase information for the selected quantity. For faster real time processing and more detailed analysis of waveforms, several DSPs can be run in parallel. There are two types of phase comparators: The numerical relay is one of electrical base of the software protection against to detect the natural & unnatural fault in the electrical machinery. When the operating current becomes large, the magnetic field produced by electromagnet is high such that this magnetic field pulls the armature or plunger making the trip circuit contacts to close. Reference // Network Protection & Automation Guide by Alstom Grid. 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. body, when the brain gives the sense the body parts are operate to do any work. These protocols helps to communicate relays among Electromechanical and static relays have fixed wiring and the setting is manual. Analogue signals are converted to digital form using an A/D converter. Advantages of numerical relays. These can then be printed or uploaded to the user’s database facilities. Any numerical relay usually consists of the following essential parts. From these samples numerical relays calculates root-mean-square values of … Some relays have 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. Gives entire details of fault B. Typical functions that may be found in a numerical relay other than protection functions are described in this section. Conducting Materials and Their Applications: Numerical relay consists of many The content is copyrighted to EEP and may not be reproduced on other websites. Several extra quantities may be derived from the measured quantities, depending on the input signals available. Relay back side usually consist of different Terminal Blocks [TB] for giving the Digital and Analog inputs, outputs . Numerical Relays working explained in this post with the help of a Numerical relay used in industrial applications. The problems have been addressed with software to automate the preparation and download of relay setting data from a laptop PC connected to a communications port of the relay. change the entire settings of the relay by simply changing Group setting. Where multiple processors are used, one of them is a general controller of the I/O, Human Machine Interface (HMI) and any associated logic while the others are dedicated to the protection relay algorithms. Listed numerical relays manufacturers, suppliers, dealers & exporters are offering best deals for numerical relays at your nearby location. Tell us what you're thinking... we care about your opinion! CT supervision is carried out more easily. Users can configure relay according to their system requirement. Required fields are marked *. functions in one relay thus replace many traditional relays with one. Multiple relay characteristics The range of operation of traditional models is narrow while numerical relays are diverse and evolution adaptable. With their unique advantages they eliminate use of a thermal/bimetal relay for motor protection. Some of the new issues that must be addressed are as follows: Numerical relays perform their functions in software. Numerical relays are classified broadly into four different types as Overcurrent relays, Distance relays, Directional relays and Differential relays ... advantages over the other relays such as reduced size, reduced number of protection elements, reduced cost, increased speed etc. Unfortunately, power systems change their topology due to operational reasons on a regular basis, such as supply from normal or emergency generation. Practical experience indicates that numerical relays are as reliable as relays of earlier technologies. As part of the process, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! Numeric relays, on the other hand, are programmable relays where the characteristics and behavior can be programmed. The first numerical relays were released in 1985. One relay can be used in many ways. appearance is good. Disturbance records and data relating to energy consumption requires time tagging to serve any useful purpose. Advantages ① It has been widely used in numerical control and automatic control. 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. This is not possible for electromechanical relays. The introduction of numerical relays replaces some of the issues of previous generations of relays with new ones. Now a day for - A numerical relay usually provides many more features than a relay using static or electromechanical technology. 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. The general principle is the calculation of a level of negative sequence current that is inconsistent with the calculated value of negative sequence voltage. An interface is added to bring the microprocessor-based-relay feature. Digital sine and cosine filters (Figure 7) extract the real and imaginary components of the signal. A copy of the setting data (including user-defined logic schemes where used) can also be stored on the computer. ways either Latch or Unlatch. Numerical relays are microprocessor-based relays whereas the other relays are controlled electromechanically. setting can be manually changed. These relay can protect various components such as feeder, Motor, Generator, Transmission line, Transformers and Bus bars. but numerical relay is having LCD to indicate the alarm and relay activation. An EMR may be able to respond hundreds of times per minute, but an SSR is capable of switching thousands of times per minute with no chattering or bounce. [info]It then has the capability to act as a disturbance recorder for the circuit being monitored, so that by freezing the memory at the instant of fault detection or trip, a record of the disturbance is available for later download and analysis. Numerical relays are natural developments of digital relays due to advances in technology. Learn about power engineering and HV/MV/LV substations. 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. 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