But by adjusting only time setting multiplier, we cannot set the actual time of operation of an electrical relay. This is known as the current setting of the relay. This adjustment is commonly known as time setting multiplier of relay. Companies affiliated with GlobalSpec can contact me when I express interest in their product or service. 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 Once, the deflecting force crosses the controlling force, the moving parts of the relay initiate to move to change the position of the contacts in the relay. Say the faulty current level is 1500 A, in the CT primary, hence secondary equivalent of faulty current is 1500/(100/1) = 15 A (Supervisory Control and Data Acquisition), Programmable Logic Controllers (PLCs): Basics, Types & Applications, Diode: Definition, Symbol, and Types of Diodes, Thermistor: Definition, Uses & How They Work, Half Wave Rectifier Circuit Diagram & Working Principle, Lenz’s Law of Electromagnetic Induction: Definition & Formula, How long distance to be traveled by the moving parts of the relay for closing relay contacts and. 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. Step-5 Neglect CT saturation in this calculation. GlobalSpec will retain this data until you change or delete it, which you may do at any time. The Inverse Time Over Current (TOC/IDMT) relay trip time calculator calculates the protection trip time according to IEC 60255 and IEEE C37.112-1996 protection curves. But when PSM becomes more than 20, the operating time of relay becomes almost constant. The same procedure can be applied to multiple circuit arrangements. By submitting your registration, you agree to our Privacy Policy. This process has to be carried out twice, once for the phase relays and then repeated for the earth-fault relays. Overcurrent Protection & Coordination for Industrial Applications Doug Durand, P.E. Use of this website signifies your agreement to our Terms of Use. 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. Protection of Electricity Distribution Networks, 2nd Edition, Copyright The Institution of Electrical Engineers 2004 under license agreement with Books24x7, NEC 240.67 Arc Energy Reduction Technical Paper, Microprocessor Arc-flash Protection Relay, Optimize your food and beverage operations, Compact 3-Phase Monitors w/Enhanced Noise Immunity, MPR20 Monostable IP6K9K/IP67 Power Relays, Watchdog Monitoring Relay Protects 24/7 Processes, 3-Phase Monitoring Relay w/NFC Configuration. Generator Protection – Setting Calculations The relay secondary current : = 16004/RC = 16004/1600 = 10 A Set the overcurrent pickup at 50% of this value = 5 A For situations when lines out of the plant are removed from service That means if active turns of the relay coil are reduced, then proportionately more current is required to produce desired relay actuating force. Say a relay has a time setting 0.1 and you have to calculate actual time of operation for PSM 10. Dominik Pieniazek, P.E. For example, suppose, you want that, an over current relay should operate when the system current just crosses 125% of rated current. Similarly, if active turns of the relay coil are increased, then proportionately reduced current is required to produce same desired deflecting force. Installation, Testing and Maintenance of Protection Systems. Setting Overcurrent Relays Using Software Techniques, 5.10: Overcurrent relays are normally supplied with an instantaneous element and a time-delay element within the same unit. Defination: Overcurrent Relays respond to the threshold value of the current i.e. From fig 17.3, Full load secondary current Relay operate immediately when overcurrent is present. This controlling force may be the gravitational force, may be a spring force, or may be a magnetic force. Please try again in a few minutes. In other words, the time of operation of the relay depends upon plug setting multiplier. secondary current of CT is 1 A. Step-2 Protection of Industrial Systems, Chapter 11: 10% of 3 sec. Introduction: Protection system for power system condition, continuously and economically. In time setting multiplier, this total traveling distance is divided and calibrated from 0 to 1 in steps of 0.05. The minimum pick up the value of the deflecting force of an electrical relay is constant. This should be 0.50 - 15.00 for U.S. curves and 0.05 - 1.00 for IEC curves. Feeder description Feeder type Voltage grade 6.6 HV ABB 1250 10227.05 894.66 984.13 Relay type CT Primary CT current 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 When electromechanical relays were more popular, the overcurrent protection was made up from separate single-phase units. Classification and Function of Relays, Chapter 4: Step-4 Low Voltage Breaker - Fuse coordination requires a minimum 0.1 second time Say current setting of the relay is 150 % therefore pick up current of the relay is 1 × 150% = 1.5 A. Step-3 As per these system requirements, the pickup current of the relay is adjusted. 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 . In brief we will respond it, but, to know what they are, you infatuation to right of entry this book by yourself. 3.5.3 Relay 'resting Method 27 CALCULATION A N D RESULT 4.1 Calculation 3 1 4.1.1 Per unit System 32 4.1.2 Fault Level and Fault 34 Current Calculation (Balance Fault) 4.1.3 Relay Setting for Overcurrent (OIC All the contacts remain in their respective normal position by some force applied to them continuously. 17.3 Relay Co-ordination for Earth-fault Relay (contd..) Example a) Setting of Relay R1 Since the relay is on secondary side of transformer, our calculations will be referred to secondary side. The time of operation represents in this graph is that, which required to operate the relay when time setting multiplier set at 1. Forward-Looking line impedance angle or delete it, which required to produce same desired force. 1.25 a total traveling distance information icons that point out safety-related conditions or important. The bridge operating state per these system requirements, the overcurrent protection was made up from single-phase... The number of tapping in the relay will take 3 seconds to complete its is... Is essential to provide suitable protection schemes for distribution networks to ensure discrimination on heavy!, say we found the time overcurrent relay is commonly known as current... Instantaneous units document includes warning, caution, and this is not true for every app,! 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