There are several classes of accuracy for instrument transformers defined by the IEEE, CSA, IEC, and ANSI standards. Instrument transformers are the most common and economic way to detect a disturbance. During a disturbance, such as system fault or overvoltage transients, the output of the IT is used by a protective relay to initiate an appropriate action (open or dose a breaker, reconfigure the system, etc.) to mitigate the disturbance and protect the rest of the power system. Protection ITs require linearity in a wide range of voltages and currents. Generally, the metering ITs require high accuracy in the range of normal operating voltage and current. The function of these instrument transformers is to transfer voltages or currents in the power lines to values which are convenient for the operation of measuring instruments and relays.ĭepending on the requirements for those applications, the instrument transformer design and construction can be quite different. This is why the use of circuit breaker is essential! Please note that isolator cannot be used to open a circuit under normal conditions! It is because it has no provision to quench the are that is produced during opening operation. You should read about CB types in this technical article. There are several main types of high voltage circuit breakers in use nowadays. It is so designed that it can be operated manually (or by remote control) under normal conditions and automatically under fault conditions. First of all, open the circuit breaker in this section and then open the isolators 1 and 2. This procedure will disconnect section II for repairs.Īfter the repair has been done, close the isolators 1 and 2 first and then the circuit breaker.Ī practical working explanation how it works (VIDEO)Ī circuit breaker is an equipment which can open or close a circuit under normal as well as fault conditions. II, the procedure of disconnecting this section will be as follows. Each section can be disconnected with the help of isolators for repair and maintenance.įor instance, if it is desired to repair section No. The entire Substation has been divided into V sections. Figure 2 – Typical use of isolators in a substationįigure 2 shows the use of isolators in a typical Substation. If the isolators are to be opened, the C.B. In other words, isolator switches are operated only when the lines in which they are connected carry no current.įor example, consider that the isolators are connected on both sides of a circuit breaker. This is accomplished by an isolating switch or isolator.Īn isolator is essentially a knife switch and is designed to open a circuit under no load. In power substations, it is often desired to disconnect a part of the system for general maintenance and repairs. Any presence of an excessive amount of contamination MUST be reported to the supervisor as it may require corrective measures.Īlso, mountings of insulators should be checked for evidence of rust and corrosion and to ensure proper alignment and securement. Insulators should be regularly cleaned to remove any contaminating materials that may be present. Insulators are such equipment that should be regularly examined for cracks, chips, breaks, and evidence of tracking or flashover.īad insulators MUST be replaced. The hole in the cap is threaded so that busbars can be directly bolted to the cap. A post insulator consists of a porcelain body, cast iron cap and flanged cast iron base. pin type, suspension type, post insulator etc.) and their use in the substation will depend upon the service requirement.įor example, post insulator is used for busbars. There are several types of insulators (e.g. Single busbar system with sectionalisation.So, let’s get into core substation elements! Nowadays, all these elements are getting more and more advanced and technically better, but the core base is the very same as they were 30 years ago. There are many variations and combinations of equipment for example switch disconnectors or circuit breakers, combined CTs and Vts into one, digital protection relays and so on. Note that described elements described are the main ones. Learn HV substation elements (graphic symbols, basics & connection schemes)
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