With static relays, tripping time of ½ cycle or even less can be obtained. While it is possible to arrange for the d.c. supply to be generated from the measured quantities of the relay, this has the disadvantage of increasing the burden on the CT’s or VT’s, and there will be a minimum primary current or voltage below which the relay will not operate. However, integrating an SSR rather than an EMR may result in an equal or even lower overall cost depending on the particular application, something we will discuss a little later. The term ‘static’ implies that the relay has no moving mechanical parts in it. RELAY: A Relay is a protection device that senses the fault in the circuit and gives a trip signal to the Circuit Breaker to isolate the faulty circuit. is connected to transmission line and secondary is connected to some filter circuit. To understand simply it is like a brain in our human body, when the brain gives the sense the body parts are operate to do any work. A scientist named Fitzgerald showed a carrier current test which conveys the … Compared to the Electromechanical Relay, the Solid Static relay has longer life-span, decreased noise when operates and faster respond speed. More expensive than dry reed relays A few of those are: Electronic Static Relay. This directly affects the possible sensitivity of the relay. Solid state relays come with a rather large and perhaps intimidating upfront price tag when compared to an electromechanical relay. The relay hardware consists of standard modules resulting in ease of service. History of Relay: The static relay are next generation relays .The Solid Static relays was first introduced in 1960’s. There exist different types of static relays. This means, that the designation ‘static relay’ covers the electronic relays of both the analog and digital designs. These principles and design criteria determine how well the basic function is performed and how in practice it deviates from the ideal. 6. Greater sensitivity and high pickup ratio. Main advantages. Mercury-wetted reed relays are similar in construction and operation to dry reed relays, but a small amount of mercury is added to the glass tube to provide more consistent contact resistance. Author: Ravi Barwad Category: Electrical Articles 14 Aug 14. Working of Static Relay . The primary of C.T. These electronic static relays were the initial ones to be known in the classification of static relays. Figure 1 - Selection of static relays. Handles more power than dry reed relays; Consistently low contact resistance Main disadvantages. Unlike, electromechanical relays that have moving parts, solid state relays are static in nature thus have inbuilt components like transistors, diodes, capacitors, etc. Speed. The comparison and measurement are done by the static circuits thus have no moving parts. Introduction to Static Relays: Characteristic Functions of Protection Relay: Characteristic Functions of Protection Relay elements using different operating principles. Disadvantages or demerits: High burden level instrument transformers are required (CTs and PTs of high burden is required for operating the electromagnetic relays compared to static relays) The directional feature is absent in electromagnetic relays; Requires periodic maintenance and testing unlike static relays This filtered signal is given to rectifier where it is converted from AC into DC (Electronics equipments works on DC supply) Solid State relays are advantageous over electromechanical relays due to various factors. Buchholz relay . Fast Resetting. Low burden. The microprocessor based relays have minimum burden on the instrument transformers. List the advantages and disadvantages of static relays. Sensitivity. 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