Assuming equality of restraining and operating turns, and neglecting the finiteness of permeability, the operating current would drive out of saturation, the limb in which operating current opposes the restraining ampere-turns, when the peak value of the operating current exceeds the magnitude of restraining current. Terms of Service 7. Gravitational force can affect the relay. Share yours for free! The block diagram of a static overcurrent time relay is shown in Fig. Gauss Effect Relays. Plagiarism Prevention 5. The book is a thoroughly revised and updated second edition of a successful text. 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. The relay is simple, reliable and has small operating time, easy adjustment and good sensitivity. Each group may comprise only one winding but if there is more than one winding in a group all those windings are magnetically linked. The amplified output is given to the output circuit to cause trip/alarm. In case of static overcurrent relays instantaneous reset is possible. In both types of relays, the desired characteristic is that the operating time (t) ... E. W. Kimbark disclosed a static overcurrent relay including a non-linear voltage modifying circuit using zener diodes or the like for modifying the DC voltage applied to a series RC circuit as a function of the amount of overcurrent. In some metals, this effect is noticeable at room temperature, as in case of bismuth. Thus directional relay is a double actuating quantity relay with one input as current I from CT and the other input V from PT. 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. If transductor is employed as amplitude comparator its sensitivity is limited due to the sensitivity of the slave relay in its output circuit. The same construction may be used for under-voltage, overvoltage or earth fault relays too. 4.11 is given as –. Definite time overcurrent relays are used for wide variations of systems conditions, as backup relays for differential and distance protection, and differential protection of transformers to avoid mal-operation during magnetization inrush currents. This type works with voltage input signals derived from PTs. These latter types of applications are described in detail in “Phase Control Using Thyristors” (AN1003). The numeric relay can be called as a miniature computer as they both have similar hardware architecture with slight differences. Actually relay is nothing but a 4. Such relays became popular because of development of semiconductor diodes. Fault current level detectors are termed overcurrent relays. In an actual relay, Ithreshold can be adjusted. Before uploading and sharing your knowledge on this site, please read the following pages: 1. Transistor which acts like a triode can overcome most of the limitations posed by the electronic valves and thus has made possible to develop the electronic relays more commonly known as static relays. 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; … Both types of relay control electrical circuits through a switch that is open or closed depending upon an electrical input. Uploader Agreement. Actually, a relay is nothing but a combination of one or more open or closed contacts. Protective Relays 3. 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. When the coil is de-energized, springs can move the contacts back to the OFF position. Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism. Electrical Engineering, Devices, Relays, Static Relays, Classification of Static Relays. INTRODUCTION In a protection relay, the term 'static' refers to the absence of moving parts to create the relay characteristic. Because reverse ARP is enabled by default, no additional commands are required. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. 2. The double frequency term can be eliminated by cross-connecting two Hall generators, as illustrated in Fig. Hall device is much simpler in construction and does not require auxiliary dc supply while the transistorized circuits require about 10V dc supply. Then it suddenly increases and becomes very large for a small value of operating current. This effect depends upon the ratio of depth to width and increases with the increase in this ratio. The term previously applied to this type of relay was semistatic relay. Electronic Relays 2. The basic R-C circuit can also be arranged in several series-parallel combinations to have different values of TC. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. Two basic arrangements are shown in Fig. Such a relay is considered better than Hall Effect relay because of simpler construction and circuitry. The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays. One uses an amplitude comparator [Fig. The term ‘static’ implies that the relay has no moving mechanical parts in it. Transistor relays are the most widely used static relays. The most common are relay comparators based on rectifier bridges, which can be arranged as either amplitude or phase comparators. 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. Transistor Relays 5. Disclaimer 8. The magnitude of this voltage is proportional to the product of strength of the magnetic field and current. If time delay is desired, a timing circuit is introduced before the level detector. In static relays it is advantageous to choose a circuit accommodating a wide range of alternative inverse time characteristics, precise minimum operating levels, definite minimum times and additional high set features, if necessary. Image Guidelines 4. Typical EMR Table 1: Physical Size Comparison of SSRs and EMRs Part Package Number of Poles Area per Pole (mm2) The control windings are energized with dc and the operating windings with ac. Many are downloadable. Privacy Policy 9. Such a characteristic is known as definite time characteristic of overcurrent relay. 4.7 where two input signals are the sinusoidal ac currents I1 and I2. 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 For an overcurrent relay-, For Iinput > Ithreshold ; Ioutput = Present. The device thus acts as a pure phase comparator. The inputs are supplied to the phase comparator. Static relays 3. Possibility of Instantaneous Reset. Operation occurs when the two ac quantities under comparison are in phase. Report a Violation 11. Digital input/Communication module Input Module The Power system operates with analog parameters. If you have a dynamic IP address or multiple static IPs, this isn't as much of an issue. The performance of CT under short-circuit condition is also improved. When the relay contacts close simultaneously with an AC single phase power source, because the electrical life of the contacts suffers extreme shortening, care is necessary. Memory 4. 1. But in some semiconductors such as indium arsenide, indium antimonite, indium phosphate, germanium etc., this voltage is enough for measurement with a sensitive moving coil instrument. Rectifier Bridge Relays 4. Types of Relays. Terms of Service 7. Electronic Relays 2. Static relay with output contacts – A static relay having a contact in one or more of its output circuit (s). In the case of transmission lines supplied from both ends, it is employed with directional relays. Content Guidelines 2. Hence less panel space is required in case of static overcurrent relays. Where, IS is the magnitude of set current, ɸ is the phase angle between V and I and θ is characteristic angle. Less maintenance, long life and not affected by shock and vibration. With n = 7 or 8, the characteristic becomes extremely inverse. The voltage so developed is very small and it is difficult to detect it. 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 … Overcurrent ground fault protection can be obtained with only one overcurrent relay by connecting it across a zero phase sequence current filter. 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. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. Functions: 1 relay can perform various functions. Where, I is the relay current, t is the time of operation and n is the characteristic index of relay and K is constant. For complete protection against phase and ground faults, generally three CTs and two phase and one ground overcurrent relays are employed in the system. Based on operation mechanism protection relay can be categorized as electromagnetic relay, static relay and mechanical relay. Static Relay Presentation 1. History of Relay. 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. Relays are broadly classified into three categories depending upon their construction and working. 4.2 (b)]. The same operation is repeated on the other limb during next half cycle. 4.2. Compact in size – The size of a single three-phase overcurrent relay may be about one-fourth of three electromagnetic relays. In static directional relays this problem is less serious because static comparators are very sensitive and it is comparatively easier to make a static directional unit reliable down to 1% of system voltage which is well within the minimum fault voltage. Transistor Relays 5. Types of solid state relays include reed relay coupled SSR, … Electrical Engineering, Devices, Relays, Static Relays, Static Overcurrent Relays and Its Types. POLYTECHNIC MAYURBHANJ, TIKARPADA 2. A single coil which permits use … When this happens a voltage is induced in the output winding and the relay gets energised. 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. Two basic arrangements of relays based on transistor comparators are shown in Fig. In the latter arrangement one ac quantity is connected to the control grid and the other to the screen grid of the electronic tube. Prohibited Content 3. Time delay overcurrent relays are used in overcurrent protection of utility equipment, distribution circuits, protection of transformers, generators, motors etc. They are more complicated in static form as compared to their electromagnetic counterparts. Content Guidelines 2. UNIT II - RELAY CIRCUIT Static relay circuit (using analog and digital ic’s) for over current: The Solid State Relay (Static Relay): History of Relay: The static relay are next generation relays .The Solid Static relays was first introduced in 1960’s. Directional relay senses direction of power flow by means of phase angle between V and I. The choice of directional unit depends upon the type of comparator used. With n = 1; It = K. The characteristic becomes inverse characteristic. The output of this summation CT is fed to an auxiliary CT, whose output is rectified, smoothened and supplied to the measuring unit (level detector). The dynamic assignment is performed by the inverse ARP feature. On the other hand the windings of the different groups are not magnetically linked. each type of relay. The induction cup type of electromagnetic relays, even though are very sensitive, have dead zone in their operation. In the above expression the first term on the right hand side is a dc voltage proportional to the vectorial product of the two inputs—flux and current—the second term is an ac voltage of double frequency. The comparator used in directional overcurrent relay may be Hall Effect generator; Rectifier bridge comparator; Instantaneous coincidence comparator or integrating coincidence phase comparator. Content Filtration 6. ω I1max cos ωt, or VH α I1max I2max sin [ωt –(ωt – α)] α I1max I2max sin α …(4.4). Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. ered to a load. Instantaneous overcurrent relays are used for short-circuit protection of large equipment. Relay is a statically typed and type-inferred language, allowing programs to be fully typed while requiring just a few explicit type annotations. 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. A transductor comprises essentially a magnetic core carrying two groups of windings usually known as operating windings and control windings. As there is no moving part, operating time of the order of 0.02 s (1 cycle) can be achieved. The static relay is the next generation relay after electromechanical type.The Solid Static relays was first introduced in 1960’s. The components used were electronic valves for measuring unit. Figure 4.15 represents the static directional relay with two inputs (V and I). The first static relays developed were the high speed differential relays and the distance relays. The high powered analog signals are stepped down with current tran… Electronic Relays: These were the first to be developed in the series of static relays. Inverse-time relays are used where the source impedance is much smaller than the line impedance. The technique of overcurrent relaying is still widely used as a means of fault detection on distribution system and on transmission lines supplied from one end. Types of Relay Elements: The Important Types of Relay Elements or also called Electromagnetic Types are 1.Induction Disc Relay The shaded pole type gives the most effective form of an electromagnet since it has the following: Higher torque/VA. A phase shifter is included in the voltage input circuit, whose output is fed to the phase comparator; so that the output from phase comparator under phase faults/earth fault condition is maximum. However, static overcurrent relays offer several advantages over the electromagnetic form: 1. where M is time-multiple setting, I is multiple of tap current; Ip is the multiple of tap current at which pick-up occurs, n is characteristic index of relay, t is time of operation in seconds and K is design constant of the relay. Electromagnetic Relay. Plagiarism Prevention 5. A new chapter on Microprocessor Applications to Protection has been added. 4.11 (a) is deleted. These relays could not meet practical requirements and hence never reached the commercial stages. 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). Transductor (Magnetic Amplifier Relays) 3. [gravityform id="1" title="false" description="false" ajax="true"]. Uploader Agreement. 4.9. The directional overcurrent relay can be made either instantaneous or time-lag type. 1. 4.5. For maximum sensitivity of relay ɸ should be equal to θ. But its use in static relays is limited because of high cost of crystal. They are more complicated in static form as compared to their electromagnetic counterparts. If the relay picks up at top value current i.e., Ip = 1. then t = K M/In – 1, The static overcurrent time relays can have the following typical characteristics. In static relays, the measurement is performed by electronic/magnetic/optical or other components without mechanical motion. The output of phase comparator is fed to the level detector. Report a Violation 11. The term ‘static ’ implies that the relay has no moving parts. A telephone type relay can be directly operated from the Hall voltage. Electromagnetic relays 2. Polarizing current is not required and output is relatively higher. Before uploading and sharing your knowledge on this site, please read the following pages: 1. Multiplexer and Analog to digital converter 5. [gravityform id="1" title="false" description="false" ajax="true"]. This phenomenon is called the Hall Effect. The measuring unit determines whether the quantity has attained the threshold value (set value) or not. Hall Effect Relays 6. Transductor (Magnetic Amplifier Relays) 3. CPU 3. New developments in commercial relay manufacture are also included. 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. Fitzgerald presented a carrier current pilot relaying scheme for the protection of transmission lines in 1928. Copyright 10. An electromechanical relay is robust and versatile. No over-reaching tendencies and more accurate time-current characteristic. 3. No effect of Gravity on operation of static relay. These were the first to be developed in the series of static relays. That is why a heavy duty telephone type relay is employed with large setting. Learn new and interesting things. An electromechanical relay (EMR) energizes a coil wound on an iron core to control the position of an armature. When the voltage on the timing capacitor VC attains the threshold value of the level detector II, tripping occurs. Such a circuit would need only one level detector. In the former arrangement two ac quantities under comparison are rectified and applied in opposition in the control grid circuit of an electronic tube and the operation occurs when one quantity exceeds the other by an amount depending on the bias. Static Instantaneous and Definite Time Overcurrent Relays: The block diagram of an instantaneous overcurrent relay is shown in Fig. The static instantaneous overcurrent relays can have operating time of as small as 10 or 20 ms while in case of conventional electromagnetic relays it is of the order of 0.1 second. Therefore solid state relays are also called as static relays. 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. Prohibited Content 3. Fault current level detectors are termed overcurrent relays. Image Guidelines 4. Figure 4.6 illustrates the basic Hall generator where the Hall crystal in the form of a slab is connected to a battery so that a current I flows through the slab in the manner shown in the figure and the magnetic field is applied so that it is perpendicular to the slab of the Hall crystal. Engineering, Devices, relays, the characteristic becomes a straight line parallel to current for! To θ in phase ɸ – θ ) were electronic valves for measuring unit is less the... Relay NAME- ROHIT KUMAR MARNDI REGD NO- F15152002039 BRANCH- electrical Engineering YEAR -... 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Has to be fully typed while requiring just a few explicit type annotations be classified:! Resistivity of some metals, this comparator is fed to the magnetic field some. Were developed to protection has been added of transmission lines supplied types of static relay both ends, it takes more! The transductor relays are classified according to the sensitivity of relay ɸ should be to.