The x-axis or horizontal axis of the Time/PSM graph represents PSM and Y-axis, or vertical axis represents the time of operation of the relay. If the relay is rated with 1 A, the normal pick up current of the relay is 1 A and it should be equal to secondary rated current of current transformer connected to the relay. It is essential to provide suitable protection schemes for distribution networks to ensure that faults are quickly remedied. Such terms are. Mohammed Tawfeeq 011 Overcurrent Relay Setting 50 Elements: Pickup Setting 51 Elements Pickup setting Time delay setting definite time: time setting Overcurrent Relay & Earth Fautt Relay Concept, Setting Calculation, Characteristics and Application in Power System explained in detail What is an Overcurrent Relay? Hence, fault current in the CT secondary, i.e., in the relay coil is, 1000 Ã 1/200 = 5A Problem 1: â Determine the time of operation of a 5-ampere, 3-second over current relay having a current setting of 125% and a time setting, multiplier of 0.6 connected to supply circuit through a 400/5 current transformer when the Similarly, if active turns of the relay coil are increased, then proportionately reduced current is required to produce same desired deflecting force. 9. GlobalSpec may share your personal information and website activity with our clients for which you express explicit interest, or with vendors looking to reach people like you. The current setting of overcurrent relay is generally ranged from 50 % to 200 %, in steps of 25 %. The force applied to the relayâs moving parts for changing the normal position of the contacts is called deflecting force. In addition to setting criteria guide lines prepared by Subcommittee on relay/protection under Task Force for Power System Analysis under Contingencies for 220kV, 400kV and 765kV transmission lines, the Subcommittee has prepared model setting calculation documents for Say a relay has a time setting 0.1 and you have to calculate actual time of operation for PSM 10. Companies affiliated with GlobalSpec can contact me when I express interest in their product or service. In all electrical relays, the moving contacts are not free to move. When calculating the fault currents, the power system is assumed to be in its normal operating state. This reference guide uses detailed examples and exercises to explain the co-ordination and inception of protection schemes. This should be 0.50 - 15.00 for U.S. curves and 0.05 - 1.00 for IEC curves. This feature is necessary to ensure discrimination on very heavy fault current flowing through sound feeders. Overcurrent Relay Setting Calculation Xls Author vps1.nordictrack.vn-2020-12-23-21-40-42 Subject Overcurrent Relay Setting Calculation Xls Keywords overcurrent,relay,setting,calculation,xls Created Date 12/23/2020 9:40:42 PM Relay operate immediately when overcurrent is present. The adjustment of traveling distance of an electromechanical relay is commonly known as time setting. When electromechanical relays were more popular, the overcurrent protection was made up from separate single-phase units. Dominik Pieniazek, P.E. Protection Schemes and Substation Design Diagrams, Chapter 14: ACCESS
Now, suppose fault current in the CT primary is 1000 A. Adaptive Protection with Group Settings Change, Chapter 6: Industrial Computers and Embedded Systems, Material Handling and Packaging Equipment, Electrical and Electronic Contract Manufacturing, Chapter 2: once the current through the relay goes, beyond the set Value, it operates From the time / PSM graph of the relay as shown below, we can see the total operating time of the relay is 3 seconds. Installation, Testing and Maintenance of Protection Systems. Hence, pick up current of the relay is, 1 Ã 150 % = 1.5 A Calculation of Short-Circuit Currents, Chapter 3: Co-ordination of Negative-Sequence Units, 5.8: From this graph one can determine the total time taken by the moving parts of an electromechanical relay, to complete its total traveling distance for different PSM. Co-ordination Across Dy Transformers, 5.7: It is also seen from the curve that, for a lower value of plug setting multiplier, i.e., for a lower value of fault current, the time of operation of the relay is inversely proportional to the fault current. Current and Voltage Transformers, 5.5: This deflecting force is always in opposition of controlling force and is present always in the relay. Calculator Parameters Inverse Time Over Current is also referred to as Time Over Current (TOC), or Inverse Definite Minimum Time (IDMT). _____ 1. Plug setting multiplier of relay is referred as ratio of fault current in the relay to its pick up current. 10% of 3 sec. UNLIMITED
The operating time of an electrical relay mainly depends upon two factors : So far by adjusting relay operating time, both of the factors to be adjusted. Overcurrent Protection & Coordination for Industrial Applications Doug Durand, P.E. Hence, actual operating time of the relay is 3 Ã 0.1 = 0.3 sec. WORLD'S
Neglect CT saturation in this calculation. In other words, the time of operation of the relay depends upon plug setting multiplier. The simulation is done in ETAP software. Say current setting of the relay is 150 % therefore pick up current of the relay is 1 Ã 150% = 1.5 A. Step-3 During study of electrical protective relays, some special terms are frequently used. Protection of Industrial Systems, Chapter 11: Overcurrent Relays with Voltage Control, 5.9: Low Voltage Breaker - Fuse coordination requires a minimum 0.1 second time Feeder description Feeder type Voltage grade 6.6 HV ABB 1250 10227.05 894.66 984.13 Relay type CT Primary CT current Hence say time setting of the relay is 0.1. This is not true for every app lication, however. The time setting dial is calibrated from 0 to 1 in steps of 0.05 sec. The current setting is sometimes referred as current plug setting. That means if active turns of the relay coil are reduced, then proportionately more current is required to produce desired relay actuating force. As per these system requirements, the pickup current of the relay is adjusted. As per definition, From the Time/PSM curve of a typical relay shown below, it is seen that, if PSM is 10, the time of operation of the relay is 3 sec. as well as subscriptions and other promotional notifications. FREE
The current setting is sometimes referred as current plug setting. Overcurrent relays are normally supplied with an instantaneous element and a time-delay element within the same unit. Therefore PSM of the relay is, 5 / 1.5 =3.33. To understand this concept easily, it is better to know about settings of the Electromechanical Relays. GlobalSpec will retain this data until you change or delete it, which you may do at any time. Now, after calculating PSM, we have to find out the total time of operation of the relay from Time/PSM curve. I agree to receive commercial messages from GlobalSpec including product announcements and event invitations,
The relation between time of operation and plug setting multiplier is plotted on a graph paper, and this is known as time/PSM graph. Overcurrent Coordination Page 3 Qual-Tech Engineers, Inc. 8. In brief we will respond it, but, to know what they are, you infatuation to right of entry this book by yourself. Although the deflecting force always presents in the relay directly connected to live line, as the magnitude of this force is less than controlling force in normal condition, the relay does not operate. These taps are brought out to a plug bridge. For example, suppose, you want that, an over current relay should operate when the system current just crosses 125% of rated current. So, if we get the total operating time of the relay for a particular PSM from time/PSM graph and if we multiply that time with the time setting multiplier, we will get, the actual time of operation of the relay for said PSM and TSM. This would be particularly true if the relay simply compared voltage and current from a common phase for a line to ground fault (e.g., I A Power system Protection Part â 5 Dr.Prof. The first step is to read the â¦ ETAP provides customized libraries for many devices that include typical, standard and manufacturer information. Step-4 Introduction: Protection system for power system condition, continuously and economically. This adjustment is commonly known as time setting multiplier of relay. Notify me about educational white papers.
Hence, it is clear that the speed of operation of an electrical relay depends upon the level of fault current. secondary current of CT is 1 A. Step-2 For part 2, 3, and 4 of Example 15.2, calculate the CT voltage if the phase relay burden is 1.2 , the residual relay burden is 1.8 , the lead resistance is 0.4 , and the CT resis-tance is 0.3 . From the curve, say we found the time of operation of relay is 3 second for PSM = 10. Relay setting, Over current relay, IDMT relay. Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current. The more modern microprocessor protection has a three-phase overcurrent unit and an earth-fault unit within the same case. If the actuating current in the relay coil increases gradually, the deflecting force in electromechanical relay is also increased. For getting a clear idea, let us have a practical example. Include me in professional surveys and promotional announcements from GlobalSpec. But by adjusting only time setting multiplier, we cannot set the actual time of operation of an electrical relay. For earth fault relay it is from 10% to 70% in steps of 10%.