Your early reply will be highly appreciated. If a CT saturates before the relay trip level is reached, the fault will remain undetected, leading to equipment damage and serious danger to personnel. According to timing characteristic, the relays can be divided into the following classes. These characteristics can be obtained by induction disc and induction cup relays. For ground back-up protection on most lines having pilot relaying for primary protection. : 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. Relays are used to protect the electrical system and to minimize the damage to the equipment connected in the system due to over currents/voltages. Figure 4 shows the connection of a distance relay for line protection. The uncertainty of the operating time and the necessary operating time may require a grading margin of 0.4 to 0.5 seconds. Its operation is independent of the magnitude of current above the pick-up value. Based on the inverseness it has three different types: The accuracy of the operating time may range from 5 to 7.5% of the nominal operating time as specified in the relevant norms. Suitable for protection of distribution feeders with peak currents on switching in (refrigerators, pumps, water heaters and so on). Classification of Over-Current Relays Overcurrent relays are classified on the basis of their operation time, in the following three categories: 1) Instantaneous Overcurrent Relay: These relays instan­ taneously send a trip command to the breaker as soon as the fault is … This characteristic is shown by curve I in Fig. Electrical Engineering, Devices, Relays, Overcurrent Relays, Classification of Overcurrent Relays. Introduction To Relay & Different Types Of Relays | Its Terminals, Working & Applications Relays are the essential component for protection & switching of a number of the control circuits & other electrical components. Refer to the type of protection classifications shown in the following table and select a Relay suitable to the atmosphere in which it is to be used. Overcurrent relay is a basic element of overcurrent protection. Relays with inverse time-current characteristics are widely employed in distribution networks and industrial plant systems. Used where there is a reduction in fault current, as the distance from source increases. In such a relay the saturation of the core occurs at a still later stage, as illustrated by curve III in Fig. f) Starting Over Current Protection In case of actuation of Class-A1 protection, Generator Circuit Breaker and Filed Circuit Breaker are opened along with turbine tripping. Before uploading and sharing your knowledge on this site, please read the following pages: 1. • The value of preset current above which the relay operates is called the pickup value. In SGP subject. Learn about power engineering and HV/MV/LV substations. You can use combinations of curve types to achieve the design requirements. IDMT Relay Low Current setting: Over Load Current setting is 125%, Plug setting of Relay is 0.8 Amp and Time Delay (TMS) is 0.125 Sec, Relay Curve is selected as Normal Inverse Type. Based on Function Over current Relay. Other Relay Classifications. Basically overcurrent relay is a type of protective relay which operates when the load current exceeds a preset value. 3. An inverse characteristic is obtained if the value of plug setting multiplier is below 10, for values between 10 and 20 characteristics tend towards definite time characteristics. Solid State Relay (SSR),Terminals Of SSR Relay, Input Or Control Terminals, Normally Open (NO) Terminals, Normally Closed (NC), Terminals , Operation Schematic Model, Types Of SSR Relay, Classification Based On Input/Output, DC-To-AC SSR Relay, AC-To-AC SSR Relay, DC-To-DC SSR Relay, DC-To-AC/DC SSR Relay, Classification Based On Switching Property, Instant ON SSR Relay, Zero … As well as protecting their own designated areas, the protective zones can overlap into other areas. The overload relay working/function is discussed below.. Classification of Protective Relays. It owes its application from the fact that in the event of fault the current would increase to a value several times greater than maximum load current. This curve is known as very inverse characteristic curve. In this type, two conditions must be satisfied for operation (tripping), current must exceed the setting value and the fault must be continuous at least a time equal to time setting of the relay. Three conditions must be satisfied for its operation: current magnitude, time delay and directionality. According to the relays operating characteristics, the relay may be classified as follows:-1) Solenoid type: In this type of relay, an iron core or plunger is moved into the solenoid coil. Discrimination by both ‘Time’ and ‘Current’. This is in place to show greater stability in the classifications which are based on compliance over five years instead of the standard ... Current classification lists. It become so helpful for me. IDMT Relay High Current setting : Plug setting of Relay is 2.5 Amp and Time Delay (TMS) is 0.100 Sec, Relay Curve is selected as Normal Inverse Type Overcurrent is used for automatic testing of directional and non-directional overcurrent relays with auto-assessment of the trip time characteristic, the directional boundaries of the current stages, and the pick-up/drop-off ratio. The protection should not operate for starting currents, permissible overcurrent, current surges. Jignesh Parmar has completed M.Tech (Power System Control), B.E (Electrical). Classification of Protective Relays • Based on Technology • Based on Function 2. Short circuits occur when a "hot" wire (an ungrounded wire, usually black or red) touches another hot wire or comes in contact with a neutral wire (a grounded wire, usually white).Shorts can also happen if there is a break in a wire in the circuit. Types and Applications Of Overcurrent Relay (1), Cost of protection / against cost of potential hazards. Very Inverse Relay 6. When the motor’s current falls below the setpoint, CR’s contacts open and de-energize M. Depending upon the time of operation, overcurrent relays may be categorized as: 1. Very often the relays do not need to be directional and hence no PT supply is required. Hence fast fault clearance is always desirable on short circuits. Used against overloads and short-circuits in stator windings of motor. Primary requirement of Overcurrent protection, Difference between Overcurrent and Overload protection, Instantaneous Overcurrent relay (Define Current), Inverse Time Overcurrent Relays (IDMT Relay), Inverse Time Overcurrent Relay (IDMT Relay), Related Phase Overcurrent relays and Earth Fault relays, Speed Fast operation to minimize damage and danger, Discrimination Isolate only the faulty section, Instantaneous Overcurrent (Define Current) Relay. The other terminology used for overcurrent is hi-set and low-set. It is difficult to co-ordinate and requires changes with the addition of load. Attraction armature type relay is the most simple both in construction as well as in its working principle. Normal inverse time Overcurrent Relay is relatively small change in time per unit of change of current. The continuity in the supply cannot be maintained at the load end in the event of fault. This type of relay operates instantaneously when the current reaches a predetermined value. Faster to trip at high fault currents. 4 . In this over current relay there is one current operated element is present. For the protection of alternators, transformers. Carmel Swim Club Takes Down Another NAG (13-14) Record; This Time in 400 Free Relay. A relay that operates or picks up when its current exceeds a predetermined value (setting value) is called Over-current Relay. England and Wales. TABLE V. COMPARISON RELAY SETTING ON 20 KV - "Setting Analysis of Over Current Relay and Ground Fault Relay on Transformer Protection System of High Voltage Substation System" a) Transmission lines b) Transformers c) Motors Image Guidelines 4. If the magnitude of the incoming signal is outside a preset range, the relay will operate, generally to … These types of electromagnetic relays can be utilized as either magnitude relay or ratio relay. In the event of switching arc jumps across the contacts which results to melting of the contact surface over a small section. •A comparison of the time it takes protective ... •Protective relay characteristics and settings •Fuse ratings •LV circuit breaker ratings, characteristics, and settings. Used when Fault Current is dependent on fault location. Over current relay is the relay which operates at the value of current is greater than the setting time of relay. An arrangement of overcurrent relay connected to operate as a differential relay … 3.24 and is known as definite time characteristic. They are, thus more suitable for installations with large inrush currents after an outage. ... Degradation over Time of Latching Relay Holding Ability. Suitable for the protection of machines against overheating. Prohibited Content 3. The grading margin may be reduced to a value in the range from 0.3 to 0.4 seconds when overcurrent relays with very inverse characteristics are used. The time characteristics can either be entered directly in current/time tables or based on a wide range of pre-defined relay and recloser characteristics. Shellfish production and relay areas are classified according to the levels of E. coli detected ... system. The non-unit schemes, while also intended to protect specific areas, have no fixed boundaries. Main protection to outgoing feeders and bus couplers with adjustable time delay setting. Separate earth fault relay provided makes earth fault protection faster and more sensitive. Why have seperate relays when a single relay can be used to implement multiple elements such as protection against ground faults, as well as ac instantaneous overcurrent? Overcurrent induction disc relays used offshore usually have a current/time operating characteristic in accordance with BS EN 60255-151 for an inverse definite minimum time relay. In fact, some of the first computers ever built used relays to implement Boolean gates.. Definite time over current relay. He is member of Institution of Engineers (MIE), India. Operates in a definite time when current exceeds its Pick-up value. Widely used for the protection of distribution lines. if it is much impressive… Any one may wud like to donate for site and app development …..make app ease for quick reference, Superb andriod app thanks a lot one of the best apps in the world …knowledge treasure, sir , what do u mean by 1.3 secs at Ni at tms =1, sir , thank you for your information . For this the heating element is kept in series with the motor. A relay which senses and operates the phase difference between the current entering into the electrical system and the current leaving the electrical system is called a current differential relay. Please suggest us to reduce these frequent tripping of relay, what will be the characteristics of relay to be set ( definite time, normal inverse or very long inverse etc. 10. Therefore, relay connected for earth fault protection is different from those for phase to phase fault protection. The main application of long time overcurrent relays is as backup earth fault protection. TD’s normally closed contact opens after TD times out, enabling CR to protect the pump from a low-liquid situation. This is inherent in electromagnetic relays due to saturation of the magnetic circuit. In our co-gen Plant , we are facing the problem of frequent tripping of grid breaker on stand by earth fault protection due to 110 KV line earth fault or even due to small disturbance at 110 KV line or at 110 KV substation where we are exporting the power. How we can select power transformer Rating? Types of Relays. Constant tripping time independent of in feed variation and fault location. When this strip is energized it tends to bend, this property is used in such a way that the bending nature makes a connection with the contacts. Figure 2 – Overcurrent relay arrangement with CT’s, including 50/51N. Current Transformer Types. Protection schemes can be divided into two major groupings: Unit type schemes protect a specific area of the system, i.e., a transformer, transmission line, generator or bus bar. Content Guidelines 2. The overcurrent protection is a bigger concept So that the overload protection can be considered as a subset of overcurrent protection. An inverse time relay is one in which the operating time is approximately inversely proportional to the magnitude of the actuating quantity. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. Over current Relays 1. Classification is based on the mechanical capacity activated by the speed of gas or liquid outflow, pressure. On some sub transmission lines where the cost of distance relaying cannot be justified. (i) Radial or loop circuits having a few sections, (ii) As backup protection for other types of protection and. This delay is fixed and it is independent of PSM value. It has a limitation that it can be applied only to simple and non costly equipments. Extremely inverse time relay Page 2 Department of Electrical Engineering, NIT Rourkela, Odisha, India - 769008 Certificate This is to certify that the work in this project entitled “Development of microcontroller based over-current relay controls” by Subham Swagat Patel(111EE0224),Sanat Kumar Sethy(111ee0233) and Satyajit Lal(111ee0448) has been carried out under my supervision in Selectivity amongst such relays is obtained if there is difference of 0.5 s in the time settings of the two successive relays. It protects the equipment of the power system from the fault current. The lowest time dial setting (fastest operating time) is generally 0.5 and the slowest is 10. Scribd is the world's largest social reading and publishing site. When the power system is not radial (source on one side of the line), an overcurrent relay may not be able to provide adequate protection. Used when Fault Current independent of normal changes in generating capacity. Gives more inverse characteristics than that of IDMT. A latching relay is a relay which maintains its state after being actuated, that’s how … Such relays are employed for restricted earth-fault and other types of circulating current protection. Such as the motor takes 3 to 5 … For feeder protection, there would be more than one overcurrent relay to protect different sections of the feeder. They generally have current setting multipliers ranging from 50 to 200% in steps of 25% which is refered to as plug setting [PS] for each relay is determined by the fault current. Be sure to carefully check the actual load before use.) Measuring transformers … Digital input/Communication module Input Module The Power system operates with analog parameters. Although there will be a short time interval between the instant of pick-up and the closing of the relay contacts, no intentional time delay is provided. OverCurrent Relay gives protection against: Overcurrent includes short-circuit protection, and short circuits can be: Short-circuit currents are generally several times (5 to 20) full load current. Generally, there are two types of relays used for DC and AC switching: Electromechanical and Solid-state relays. Over current Relay • Definite time over current relay • Instantaneous over current relay • Inverse time over current relay • Inverse definite minimum time (IDMT) over current relay • Very inverse –time over current relay • Extremely inverse time over current relay There are four typical types of current transformers: window, bushing, bar, and wound.The primary winding can consist merely of the primary current conductor passing once through an aperture in the current transformer core (window- or bar-type), or it may consist of two or more turns wound on the core together with the secondary winding (wound type). The curve IV in Fig. So by varying the point of saturation different characteristics are obtained. This is because of their ability to ride through starting currents and surges, providing at the same time fast operation under fault conditions. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.. According to applications the relays may be classified as: (i) Overvoltage, Overcurrent and Overpower Relay: The relay operates when the voltage, current or power rises above a specified value. •An organized time-current study of protective devices from the utility to a device. Report a Violation 11. Used when Fault current independent of normal changes in generating capacity. Short Circuits . It helps you. Hi to all engineers in here may I ask for a LINE PROTECTION CALCULATION and Over Current protection calculations? Account Disable 12. This is the simplest of the ways to protect a line and therefore widely used. Voltage Rating: The voltage rating of the overcurrent protective device must be at least equal to or greater than the circuit voltage. A relay which senses and operates the phase difference between the current entering into the electrical system and the current leaving the electrical system is called a current differential relay. Classification or types of protective relays. IDMT is low set. Instantaneous, in old days used to be high set (i.e., trips without delay for respective plug setting). This comes under the classification of reed relay which uses a mercury switch and the contacts in this relay … Inverse time overcurrent relays: Slow to trip at low currents. Thermal Overload Relay. Types of Over Current Relay Depending upon time of operation, there are various types of Over Current relays, such as, Instantaneous over current relay. 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. The operating currents are progressively increased for the other relays when moving towards the source. The high powered analog signals are stepped down with current tran… For the different characteristics of circuit and equipment over current relays are of different types. Terms of Service 7. Relays with very inverse time-current characteristics are employed on feeders and long sub-transmission lines. Dear Sirs, I hope you can make an article as well comparing IEC and ANSI curves thank you! Overcurrent and Earth-fault Protection Overcurrent Protective Relay-5 • A protective relay that operates (trips) when the load current exceeds a preset value is known as an overcurrent relay. An instantaneous overcurrent relay is one in which no intentional time delay is provided for operation. So the protection against the over current or exceeds current in the line is the essential protection for the device. The use of extremely inverse overcurrent relays makes it possible to use a short time delay in spite of high switching-in currents. They are normally more inverse near the pick-up value of the actuating quantity and become less inverse as it is increased. As the name implies, these relays are used to prevent the electric motors from damage by over current and short circuits. The more pronounced the effect is the more inverse the characteristic is said to be. It is possible to use a set of two O/C relays for protection against inter-phase faults and a separate Overcurrent relay for ground faults. If the magnitude of the incoming signal is outside a preset range, the relay will operate, generally to close or open electrical contacts to initiate some further operation, for example the tripping of a circuit breaker. Modern relays may contain more than one stage of protection each stage includes each own current and time setting. 2) Attracted armature type: This type of relay is connected in a circuit and this type of relay operate when the current of the circuit increase beyond the normal. Overload relays are classified into two types namely thermal overload relay and magnetic overload relay.. Introduction To Relay & Different Types Of Relays | Its Terminals, Working & Applications Relays are the essential component for protection & switching of a number of the control circuits & other electrical components. In these schemes, the effects of any disturbance or operating condition outside the area of interest are totally ignored and the protection must be designed to be stable above the maximum possible fault current that could flow through the protected area. At values of current less than pick-up value, the relay never operates: At higher values, the operating time of the relay decreases steadily with the increase of current. Differential relaying provides selectivity by providing a zone of protection with a circuit of interconnected CT’s. While this can be very beneficial for backup purposes, there can be a tendency for too great an area to be isolated if a fault is detected by different non unit schemes. EEP Portal is Beautiful gift for all Electrical Engineers……Nothing but Knowledge treasure…Thanks a lot for educating for us. Now a days we have options to set many stages of fault current for tripping. Hello sir.. My name is Aidil and i am undergraduate in Bachelor degree in Electrical Engineering at Universiti Teknologi Malaysia.. I’m not understand clearly on earth fault relay.. hot its work actually? Inverse-Time Overcurrent Relay 3. I commonly use inverse-time, definite-time, and instantaneous elements, all on the same relay. Of extremely inverse overcurrent relays but basic working principle of overcurrent relays equipment over current relay ( IDMT ).! Knowledge treasure…Thanks a lot for educating for us instantaneous / definite time when current exceeds low-current! Cup relays characteristic, the time of operation the overcurrent protective device rating although. Cup relays progressively increased for the purpose of protection / against cost of potential hazards contact forms, as... 4 motor which is not desirable in on direction of current flow can be utilized as either magnitude relay ratio... Is detected delay in spite of high switching-in currents illustrates that the nearest... To implement Boolean gates into a bimetallic strip input/Communication module Input module the power which. Boolean gates work and a few of their steep characteristics margin of 0.4 to 0.5 seconds overcurrent is hi-set trip! Protective relay that functions on a wide range of setting what you 're thinking... care. 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