Static Relay Presentation 1. However, it takes up more room and is slower than an SSR. Rectifier Bridge Relays 4. A transductor comprises essentially a magnetic core carrying two groups of windings usually known as operating windings and control windings. 1. Where, I is the relay current, t is the time of operation and n is the characteristic index of relay and K is constant. The protective relays are either single actuating quantity relays such as overcurrent, under-voltage, earth fault relay or double actuating quantity relays such as distance relays, differential relays. The voltage so developed is very small and it is difficult to detect it. 4.11 (a) is deleted. These relays could not meet practical requirements and hence never reached the commercial stages. ω I1max cos ωt, or VH α I1max I2max sin [ωt –(ωt – α)] α I1max I2max sin α …(4.4). A new chapter on Microprocessor Applications to Protection has been added. Magneto resistors are sensitive to the magnetic field strength and not to the rate of variation. Content Filtration 6. These latter types of applications are described in detail in “Phase Control Using Thyristors” (AN1003). Content Filtration 6. Typical EMR Table 1: Physical Size Comparison of SSRs and EMRs Part Package Number of Poles Area per Pole (mm2) For an overcurrent relay-, For Iinput > Ithreshold ; Ioutput = Present. When the coil is de-energized, springs can move the contacts back to the OFF position. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. Static overcurrent relay is made in the form of a single unit in which diodes, transistors, resistors, capacitors etc., are arranged on printed board and are bolted with epoxy resin. The general equation for time characteristic is given as –. Gauss Effect Relays. Operation occurs when the two ac quantities under comparison are in phase. Terms of Service 7. : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency. The block diagram of a static overcurrent time relay is shown in Fig. Static relays are contrasted with electromechanical relays, which use moving parts to create a switching action. This phenomenon is called the magneto resistivity or Gauss effect. Electromagnetic relays are those relays which are operated by electromagnetic action. With n = 1; It = K. The characteristic becomes inverse characteristic. When the phase angle between V and I exceeds certain predetermined value, the directional relay operates with a condition that the current is above the pick-up value. Overcurrent relays are also employed in conjunction with distance relays to provide backup protection. The secondaries of the line CTs are connected to a summation circuit (not shown in the figure). A telephone type relay can be directly operated from the Hall voltage. Static relays are classified according to the type of the measuring unit or comparator as follows: 1. So the output voltage will be –, VH α (V1 – V2) α {[I1(dI2/dt)] – [I2 (dI1/dt)]}, α I1max sin ωt x I2max ω cos (ωt – α) – I2max sin (ωt – α). The relay which consists static and electromagnetic relay is also called static relay because the static units obtain the response and the electromagnetic relay is only used for switching operation. 4.2 (a)] and the other makes use of a phase comparator [Fig. Staticrelays Components of static relays Block diagram of static relays Types of static relays Prepared By Mr.K.Jawahar, M.E., Assistant Professor Department of EEE Static Relays Kongunadunadu College of Engineering and Technology Depar tment of EEE 2. The induction cup type of electromagnetic relays, even though are very sensitive, have dead zone in their operation. Share yours for free! In some metals, this effect is noticeable at room temperature, as in case of bismuth. Output module 6. What is a Relay? Transductor (Magnetic Amplifier Relays) 3. Indium antimonite and indium arsenide are more sensitive in comparison to bismuth or mumetal. In this article, the different types of relays like overload protection relay, solid state relay, solid state contactor relay, Buchholz relay, Mercury Wetted relay and … The RSR-72 type relay for re-start and reacceleration is deigned to perform the automatic motor restarting, after control and protection device opening, as a consequence of a momentary line voltage interruption or drop-out. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. Such a characteristic is known as definite time characteristic of overcurrent relay. Image Guidelines 4. Account Disable 12. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. Fault current level detectors are termed overcurrent relays. Low CT burden – The VA consumption of static overcurrent relays is quite low (7 mVA to 100 mVA) as compared with that of electromagnetic relays (1VA to 3VA) so that smaller CTs are required. In the case of transmission lines supplied from both ends, it is employed with directional relays. In static relays, the measurement is performed by electronic/magnetic/optical or other components without mechanical motion. The operating winding is wound in such a way that the ampere-tums so produced oppose the restraining ampere-turns in one limb and strengthen them in the other. Instantaneous overcurrent relays are also useful in other protective relay systems. If time delay is desired, a timing circuit is introduced before the level detector. Time delay overcurrent relays are used in overcurrent protection of utility equipment, distribution circuits, protection of transformers, generators, motors etc. Compact in size – The size of a single three-phase overcurrent relay may be about one-fourth of three electromagnetic relays. The current from the line CT is reduced to 1/1000th by an auxiliary CT, the auxiliary CT has taps on the primary for selecting the desired pick-up and current range and its rectified output is supplied to level detector I (overload level detector) and an R-C timing circuit. In conventional electromagnetic relays, n may vary between 2 and 8. Such a circuit would need only one level detector. For maximum sensitivity of relay ɸ should be equal to θ. By varying values of R and C the time can be varied without difficulties. Static Instantaneous and Definite Time Overcurrent Relays: The block diagram of an instantaneous overcurrent relay is shown in Fig. According to the principle of operation and construction, the relay may be classified such as the electromagnetic attraction type, electromagnetic induction type, electrodynamic type, moving coil type, electro-thermal type, physics electric type, and static relays. On the other hand if it is used as a phase comparator to achieve higher sensitivity it will depend on an external ac supply which is sometimes difficult to arrange. ered to a load. Fitzgerald presented a carrier current pilot relaying scheme for the protection of transmission lines in 1928. Two basic arrangements of relays based on transistor comparators are shown in Fig. Many are downloadable. Rectifier Bridge Relays 4. Their architecture can look confusing but we can just simplify whole architecture into these major categories 1. When a conductor is kept perpendicular to the magnetic field and a direct current is passed through it, it results in an electric field perpendicular to the directions of both the magnetic field and current with a magnitude proportional to the product of the magnetic field strength and current. Polarizing current is not required and output is relatively higher. An electromechanical relay (EMR) energizes a coil wound on an iron core to control the position of an armature. each type of relay. The output of phase comparator is fed to the level detector. History of Relay. After operation of the measuring unit, the output is amplified by the amplifier. That is why a heavy duty telephone type relay is employed with large setting. Instantaneous overcurrent relays are used for short-circuit protection of large equipment. Report a Violation 11. This is due to the absence of moving parts, which facilitates the application of automatic reclosing of breakers. 4.11 is given as –. CPU 3. This type works with voltage input signals derived from PTs. View Static Relays PPTs online, safely and virus-free! The restraining voltage is applied to the control winding through an impedance ZR and a rectifier. 4.7 where two input signals are the sinusoidal ac currents I1 and I2. The IEEE defines protective relays as: “relays whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action ”. Privacy Policy 9. Input Module 2. The term previously applied to this type of relay was semistatic relay. The book is a thoroughly revised and updated second edition of a successful text. Electronic Relays: These were the first to be developed in the series of static relays. Digital input/Communication module Input Module The Power system operates with analog parameters. Fault current level detectors are termed overcurrent relays. The most common are relay comparators based on rectifier bridges, which can be arranged as either amplitude or phase comparators. Types of Relays. On occurrence of ground fault, the zero sequence current will flow through the relay coil and relay will operate if the relay current exceeds the threshold value. Smoothening circuit and filters are introduced in the output of the bridge rectifier. Such relays became popular because of development of semiconductor diodes. The restraining current so obtained is rectified and partially smoothened by the short-circuit effect of the rectifier on the control winding and also due to the short- circuited coupling winding. Relay will operate when IS < I cos(ɸ – θ). Static relay with output contacts – A static relay having a contact in one or more of its output circuit (s). It incorporates the latest developments in semiconductor technology and its applications to power system protection. New developments in commercial relay manufacture are also included. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. The fact that a transistor can be employed both as an amplifying device and a switching device makes it suitable for achieving any functional characteristic. Plagiarism Prevention 5. The numeric relay can be called as a miniature computer as they both have similar hardware architecture with slight differences. Learn new and interesting things. On the other hand the windings of the different groups are not magnetically linked. Electrical Engineering, Devices, Relays, Static Relays, Static Overcurrent Relays and Its Types. Position of relay: Relay can be installed at any location and at any position. In addition to these the other types of static relays are: Hall effect relays; Inverse time overcurrent relay; Directional static overcurrent relay; Static differential relay; … I1 = I1max sin ωt and I2 = I2max sin (ωt – α) …(4.2), Flux through crystals I and II will be ɸ1 α I1 and ɸ2 α I2, and current through the crystals will be I’1 [α (dI2/dt)] and I2 [α (dI1/dt)] …(4.3), Two crystals I and II are connected in such a way that their output voltages are in opposition. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. Because of the high cost of Hall element, low output and large temperature error, this comparator is normally not used. The control windings are energized with dc and the operating windings with ac. Response of Tower-Like Structures to Wind Loading | Wind Engineering, Unconventional Machining Processes: AJM, EBM, LBM & PAM | Manufacturing, Material Properties: Alloying, Heat Treatment, Mechanical Working and Recrystallization, Design of Gating System | Casting | Manufacturing Science, Forming Process: Forming Operations of Materials | Manufacturing Science, Generative Manufacturing Process and its Types | Manufacturing Science. In an actual relay, Ithreshold can be adjusted. The static relay is the next generation relay after electromechanical type.The Solid Static relays was first introduced in 1960’s. The high powered analog signals are stepped down with current tran… Disclaimer 8. 1. The effect of this is to drive both the limbs on which the operating winding is wound into saturation. The operation depends on the difference of the average rectified voltage (V1-V2).Here the rectifiers are not protected against higher currents. [gravityform id="1" title="false" description="false" ajax="true"]. Transistor Relays 5. Types of solid state relays include reed relay coupled SSR, … Extremely inverse overcurrent relays are used for the fuse coordination and thermal protection of transformers and induction motors. A solid state relay is composed of both static and electromechanical units in which the response is accomplished by the static units. Uploader Agreement. Gravitational force can affect the relay. The transistor circuits cannot only perform the essential functions of a relay (such as comparison of inputs, summation and integrating them) but they also provide necessary flexibility to suit the various relay requirements. The device thus acts as a pure phase comparator. Possibility of Instantaneous Reset. The inputs are supplied to the phase comparator. Solid State Relays We will discuss all of them in detail below. Hence less panel space is required in case of static overcurrent relays. 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