Figure 1 - Selection of static relays. The microprocessor based relays have minimum burden on the instrument transformers. 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. History of Relay: The static relay are next generation relays .The Solid Static relays was first introduced in 1960’s. Speed. There exist different types of static relays. Greater sensitivity and high pickup ratio. Handles more power than dry reed relays; Consistently low contact resistance Main disadvantages. A few of those are: Electronic Static Relay. 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. Working of Static Relay . Fast Resetting. The relay hardware consists of standard modules resulting in ease of service. 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 Solid State relays are advantageous over electromechanical relays due to various factors. What is static relay? This filtered signal is given to rectifier where it is converted from AC into DC (Electronics equipments works on DC supply) is connected to transmission line and secondary is connected to some filter circuit. All faults below the oil in transformer result in the localized heating & breakdown of the oil, some degree of arcing will always take place in a winding fault & the resulting decomposition of it will release gases such as hydrogen, carbon monoxide & hydrocarbons. Sensitivity. These principles and design criteria determine how well the basic function is performed and how in practice it deviates from the ideal. More expensive than dry reed relays The term ‘static’ implies that the relay has no moving mechanical parts in it. Main advantages. A scientist named Fitzgerald showed a carrier current test which conveys the … 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. List the advantages and disadvantages of static relays. Introduction to Static Relays: Characteristic Functions of Protection Relay: Characteristic Functions of Protection Relay elements using different operating principles. The comparison and measurement are done by the static circuits thus have no moving parts. Unlike, electromechanical relays that have moving parts, solid state relays are static in nature thus have inbuilt components like transistors, diodes, capacitors, etc. 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. Static relays are those in which the designed response is developed by electronic or magnetic means without mechanical motion. Working of Static Relay. Compared to the Electromechanical Relay, the Solid Static relay has longer life-span, decreased noise when operates and faster respond speed. 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. These electronic static relays were the initial ones to be known in the classification of static relays. This directly affects the possible sensitivity of the relay. Author: Ravi Barwad Category: Electrical Articles 14 Aug 14. Buchholz relay . This means, that the designation ‘static relay’ covers the electronic relays of both the analog and digital designs. With static relays, tripping time of ½ cycle or even less can be obtained. Low burden. The primary of C.T. 6. Solid state relays come with a rather large and perhaps intimidating upfront price tag when compared to an electromechanical relay.