In addition detailed coverage of proper protective device selection and application is provided. Why is Relay Coordination Study and Analysis Performed? So the networks of electricity companies become very complicated. Another time to revisit the protection coordination study is when equipment is experiencing nuisance tripping: this can be caused by abnormal currents in the equipment, or a faulty relay. Why do I need a protection coordination study? In any power system netowrk, protection should be designed such that protective relays isolate the faulted portion of the network at the earliest, to prevent equipment damage, injury to operators and to ensure minimum system disruption enabling continuity of service to healthy portion of the network. During our course you will learn the analysis fundamentals prior to learning to use the software. Such an approach eliminates the need to deal with the drawing office support for the protection study. Also, a good graphical monitor and laser quality printer is required.
The main purpose of the protective coordination software is to produce one-line diagrams, calculation of relay settings and time current coordination drawings. Thus it can be concluded that the results obtained by both the methods i. The short-circuit currents calculated with the preceding as- sumptions will be slightly higher, on the conservative side, than if the neglected values were used in the calculations. The overcurrent relay coordination in radial network is highly constrained op- timization problem. In modern era, the demand for electrical power generally is increasing at a faster rate in economically emerging coun- tries. Using the software, the device characteristics can be called from the library and used for the coordination studies.
Apart from the fault or short circuit conditions, protection system must also be designed to provide protection against thermal-withstand limits, motor stalling, negative sequence current with-stand limits, protection against abnormal frequencies, and protection against unbalance operating conditions as applicable to various equipments and operating situations. This is possible only through computer programming. How do I get one done? If you liked this article be sure to share with the buttons below and sign up for our where you will get these posts in your inbox and special offers. Alternatively, these files can be copied and pasted in word processing documents. The relays in the power system are to be coordinated properly so as to provide primary as well as back up protection, and at the same time avoid mal function and hence avoid the unnecessary outage of healthy part of system.
The Institute of Electrical and Electronics Engineers, Inc. Dates and Locations Participant slots are limited to 12 to maximize student involvement. To optimize your training funds, on-site training at your facility is also available for seven or more students. Knowledge of protective device operating characteristics and their impact on arc flash hazards within a system are crucial. At the far right is the fuse. These exercises will be especially useful when transformers are set on taps that do not match the system nominal voltage. And go on increasing the time upstream till next such delta star transformer is encountered that is when unbalance in line currents due to fault current is not reflected on the other side.
The protective relays must also be able to discriminate between faulted conditions, normal operating conditions and abnormal operating conditions and function only for the specific protection for which they are designed, without operating for any normal and short term acceptable abnormal events for which they are not intended to act and provide protection. The highest short-circuit current of the system is the right-hand limit of the curves. Mostly relay coordination study and analysis is computer aided. It is extremely hard to print curves to scale for overlaying, and to try multiple options when an issue presents itself. The short circuit analysis methodology presented here is the method used generally in industries with reference to ect 158 of Schneider Electric. In the process of plotting the time-current characteristic curves, it must be remembered that all currents must be referred to a common voltage, either primary or secondary, before attempting to determine coordination.
By performing the study on a personal computer, several alternatives can be examined before arriving at the final solution. For a current course brochure. Purpose of this study is to get the best coordination of protective device when three phase overcurrent were occurred, represented by time-current curves and each setting of protective device. The major function of protection device is to clear the fault and to isolate the faulted network, in order to minimize equipment damage due to fault. The library includes models for overcurrent relays, ground relays, static trip breakers, moulded case circuit breakers, data for cable damage curve, and data for transformer damage curve, motor overloads and reclosers. This course is structured to provide information and methods needed to conducting a short circuit and protective device coordination study for both low voltage and medium voltage distribution systems. All the faults are considered bolted, that is, the fault im- pedance is assumed to be zero.
Index Terms — earth fault settings , etap simulation , hand calculation, over current relay settings, radial system, relay coordination, short circuit analysis. The term or phrase relay coordination therefore covers the concept of discrimination, Selectivity and backup protection as explained in the foregoing discussion. Hence, protective device shall operate as fast as possible against faulted point. Relay coordination is an important aspect in the protection system design as coordination schemes must guarantee fast, selective, and reliable relay operation to isolate the power system faulted sections. The overcurrent relays phase and earth fault are the major protection devices in a distribution system. Selective Coordination The time-current characteristic curves of protective devices should not overlap if selective coordination is to be achieved, nor should the primary device of the transformer trip on inrush.
The protective equipment should be set to defend motors, cables and system gear from overlay as well as short-circuit states. In it I explain the various methods that you can use to complete a power system study, which can work for any individual study. This time is critical information for an , and will greatly affect the severity of an arc fault. If you have any queries, Click on Protective Relay Coordination. Hence, protective device shall operate as fast as possible against faulted point. In power system protection relay and circuit breakers is the major instrument for large interconnected power system. The percent of impedance value is 793.