3.24 and is known as definite time characteristic. One of the most important considerations in overcurrent and overvoltage protection is the speed of operation. The lowest time dial setting (fastest operating time) is generally 0.5 and the slowest is 10. especially applicable where the fault magnitude is mainly dependent on the system generating capacity at the time of fault. For feeder protection, there would be more than one overcurrent relay to protect different sections of the feeder. Very very thanks to the Resp.author. Generally, there are two types of relays used for DC and AC switching: Electromechanical and Solid-state relays. The operating time of all overcurrent relays tends to become asymptotic to a definite minimum value with increase in the value of actuating quantity. It has pick-up and time dial settings, desired time delay can be set with the help of an intentional time delay mechanism. Over current relay meant for sensing any internal short circuit, over load condition, earth fault thereby reducing the system failure & risk of fire. 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. Distance Relay – In this relay operation depends on the ratio of the voltage to the current. Electromechanical Relays. While, the overload protection protects against the situation where. Shellfish production and relay areas are classified according to the levels of E. coli detected ... system. 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 . Electrothermal relay: When two different materials are joined together it forms into a bimetallic strip. 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. Directional relays responds to. 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. You can use combinations of curve types to achieve the design requirements. Classification of Current Transformers Depending on their application, current transformers can be classified into measuring and protection current transformers. Copyright 10. Please let me know that this 7SJ614 can be used in the Switchgear Panels (33kV and 13.8kV) for ARC FLASH Protection by sensing light, Pressure and heat . Earth fault current is always less than phase fault current in magnitude. In general, relays classification is dependent on the electric capacity which is activated by current, power, voltage, and many other quantities. Over current Relays 1. Thermal 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. 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. a) Transmission lines b) Transformers c) Motors So the protection against the over current or exceeds current in the line is the essential protection for the device. (ii) Under-Voltage, Under-Current and Under-Power Relay: The relay operates when the voltage, current or power falls below a specified value. As well as protecting their own designated areas, the protective zones can overlap into other areas. The non-unit schemes, while also intended to protect specific areas, have no fixed boundaries. In the event of switching arc jumps across the contacts which results to melting of the contact surface over a small section. 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. Input Module 2. Inverse Definite Minimum Time (IDMT) Relays 5. Depending on the time of operation the overcurrent relay is categorized into following types. what are the differences between definite time and IDMT compared to hi-set and low-set overcurrent. a) Instantaneous relays b) Definite time lag c) Inverse time lag d) All of these Ans: (d) 22. This type of relay operates in on direction of current flow and blocks in the opposite direction. 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 … Account Disable 12. Such a relay is one in which operating time is approximately inversely proportional to fault current near pick-up value and becomes substantially constant slightly above the pick-up value of the relay, as illustrated by curve II in Fig. These are the types of overcurrent relay: Definite current relay operate instantaneously when the current reaches a predetermined value. Application: This type is applied to the outgoing feeders. Attraction armature type relay is the most simple both in construction as well as in its working principle. Types of Over Current Relay Depending upon time of operation, there are various types of Over Current relays, such as, Instantaneous over current relay. This characteristic can be achieved with the help of hinged armature relays. Disclaimer 8. Types of Relays. The most simple of these schemes measures current and incorporates an inverse time characteristic into the protection operation to allow protection nearer to the fault to operate first. It has more inverse characteristics than that of IDMT and very inverse overcurrent relay. Back up protection to differential relay of power transformer with time delay. 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. The relay is used for the purpose of protection of the equipment connected with it. Over current relays are to protect an electrical system or equipment from over current faults like thermal current or short circuit current. An instantaneous overcurrent relay is one in which no intentional time delay is provided for operation. Relay Applications. if you don’t mine please send me power system protection book on my mail id [email protected], Thanks alot for the helpful information you provide. The general practice is to employ a set of two or three overcurrent relays and a separate overcurrent relay for single line to ground fault. ... Degradation over Time of Latching Relay Holding Ability. Particular suitable for grading and coordinates with fuses and re closes. The instantaneous relay is effective only where the impedance between the relay and source is small compared with the impedance of the section to be protected. As the name implies, these relays are used to prevent the electric motors from damage by over current and short circuits. 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). Electromagnetic attraction type relay. It’s used when Fault Current is dependent on, Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! Current transformers Principle of operation of CT A current transformer is defined as "as an instrument transformer in which the secondary current is substantially proportional to the primary current (under normal conditions of operation) and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections." It is not suitable for long distance transmission lines where rapid fault clearance is necessary for stability. 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 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. They are, thus more suitable for installations with large inrush currents after an outage. 3.24. 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. Is it correct to say that IDMT is low-set and Instantaneous is hi-set? Title: Over Current Relay Working Principle Types Electrical4u Com Author: wiki.ctsnet.org-Sandra Maurer-2020-10-03-09-03-04 Subject: Over Current Relay Working Principle Types Electrical4u Com For Operation of Definite Time Overcurrent Relay operating time is constant. A. Prohibited Content 3. It depends on the zero sequence impedance of the system. It become so helpful for me. Overcurrent protection protects against excessive currents or currents beyond the acceptable current ratings, which are resulting from short circuits, ground faults and overload conditions. 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? In this article, we will look at how relays work and a few of their applications.­ I commonly use inverse-time, definite-time, and instantaneous elements, all on the same relay. These ratings include voltage, ampere and interrupting rating. 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. 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. The numeric relay can be called as a miniature computer as they both have similar hardware architecture with slight differences. The content is copyrighted to EEP and may not be reproduced on other websites. a) Power b) Voltage c) Current d) Reactance Ans: (a) 23. 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. Types of Relay Based on the principle of operation. This is inherent in electromagnetic relays due to saturation of the magnetic circuit. ­­A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. 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. (iii) On systems with wide variations of fault current due to source impedance. Title: Over Current Relay Working Principle Types Electrical4u Com Author: media.ctsnet.org-Sandra Lowe-2020-10-01-05-44-17 Subject: Over Current Relay Working Principle Types Electrical4u Com 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. Overload Relay Connection Diagram. Based on Function Over current Relay. In such a relay, the relay contacts close immediately after the current in the relay coil exceeds that for which it is set. 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" Used when Fault Current is dependent on fault location. consider it is feeding for 4 Motor which is rated 100KW each and it has 6 times of starting current. The overcurrent relay can be used as overload (thermal) protection when protects the resistive loads, etc., however, for motor loads, the overcurrent relay cannot serve as overload protection Overload relays usually have a longer time setting than the overcurrent relays. Digital input/Communication module Input Module The Power system operates with analog parameters. Depending upon time of operation, there are various types of OC relays, such as, 1. Used when Fault current is dependent on fault location. If the interrupting rating is not properly selected, a serious hazard for equipment and personnel will exist. Current Transformer Types. Their architecture can look confusing but we can just simplify whole architecture into these major categories 1. Thus when over heat occurs the bi-metallic strip connected to the motor heats up and in turn releases a spring to operate the contacts of the relay. These are the most important purposes of overcurrent relay: In order for an overcurrent protective device to operate properly, overcurrent protective device ratings must be properly selected. Such a relay operates after a specified time irrespective of the magnitude of the fault current. Instantaneous Overcurrent Relay 2. Extensively also at power-transformer locations for external-fault back-up protection. The relai will be used as Micom P-127 relay, I have set the In (Over current) 6In with 30 milli secs (Curve IDMT) and Thermal over load is 100% IN =1In with time of 60 minutes. Relay have difficulties in distinguishing between Fault currents at one point or another when fault impedances between these points are small, thus poor discrimination. • Contact Resistance This value is the combined resistance of Latching Relays. The directionality of current flow can be identified using voltage as a reference of direction. Suitable for protection of distribution feeders with peak currents on switching in (refrigerators, pumps, water heaters and so on). Current relay CR energizes when the motor’s current exceeds the low-current setting. Operates when current exceeds its pick-up value. So, for a better protection of the system. Classification of Relays. Tell us what you're thinking... we care about your opinion! 6_Classification of relays.ppt - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. IDMT is low set. Very often the relays do not need to be directional and hence no PT supply is required. Used where there is a reduction in fault current, as the distance from source increases. Discrimination by both ‘Time’ and ‘Current’. The overcurrent protective device rating can be higher than the system voltage but never lower. Types of Over Current Relay . Content Guidelines 2. Other Relay Classifications. Single phase fault currents are NOT always lower than Phase fault currents. Relays with inverse time-current characteristics are widely employed in distribution networks and industrial plant systems. Back up protection of distance relay of transmission line with time delay. Over voltage relay meant for sensing over voltages & protect the system from insulation break down and firing. The more pronounced the effect is the more inverse the characteristic is said to be. 15.2Types of Overcurrent Relay Time delayed Definite Time Relay: A definite time over-current relay can be adjusted to issue a trip output after a specified delay when the relay picks up (PSM>1). This type of relay operates instantaneously when the current reaches a predetermined value. Their relatively flat time-current characteristic permits them to achieve reasonably fast operation over a wide range of short-circuit currents. Below given figure illustrates that the time-current characteristics of an inverse-current relay. Main protection to outgoing feeders and bus couplers with adjustable time delay setting. Over-current protection protects electrical power systems against excessive currents which are caused by short circuits, ground faults, etc. Study specialized technical articles and papers. Memory 4. 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. 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. [gravityform id="1" title="false" description="false" ajax="true"]. Operating time depends on the magnitude of current. dear sir please inform me about the when 132kv line frequancy higt what we do and what is excitation have a book plz send me in my email, First of all i would like to thanks you very very much, your lesseon are so valuable To introduce myself, my name Binh, i am Vietnamese, i work for shipyard that many electrical issue i met everyday make me many questions about it, Could you please agree to put myself in your group that can help me to follow all comments from all engineers and also i can send my question on it. provide over current protection, directional over current protection (for selectivity in case of multiple parallel lines), under/over voltage protection, breaker failure protection (in case the breaker fails to trip even after receiving the trip command), etc [5]. Electromagnetic Relay Working. 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. •An organized time-current study of protective devices from the utility to a device. Normal inverse time Overcurrent Relay is relatively small change in time per unit of change of current. Extremely inverse time relay 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. 5.2.1 Definite-Current Relays. 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. The uncertainty of the operating time and the necessary operating time may require a grading margin of 0.4 to 0.5 seconds. It helps you. The setting is chosen so that, at the substation furthest away from the source, the relay will operate for a low current value and the relay operating currents are progressively increased at each substation, moving towards the source. The relay operation time is inversely proportional to the fault current. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. Although there are different types of overcurrent relays but basic working principle of overcurrent relay is more or less same for all. Measuring transformers … For this the heating element is kept in series with the motor. Based on the relay operating characteristics, overcurrent relays can be classified into three groups: definite current or instantaneous, definite time, and inverse time. It is difficult to co-ordinate and requires changes with the addition of load. How we can select power transformer Rating? EEP Portal is Beautiful gift for all Electrical Engineers……Nothing but Knowledge treasure…Thanks a lot for educating for us. Very Inverse Relay 6. The main application of long time overcurrent relays is as backup earth fault protection. 10. Multiplexer and Analog to digital converter 5. •A comparison of the time it takes protective ... •Protective relay characteristics and settings •Fuse ratings •LV circuit breaker ratings, characteristics, and settings. Slower ) by adjusting the ‘ time ’ and ‘ current ’ years experience in transmission & distribution-energy detection. Well as protecting their own designated areas, the time settings of the system generating capacity,! Circuits, ground faults, etc with very inverse overcurrent relays may contain more than one overcurrent to. Of gas or liquid outflow, pressure zones can overlap into other areas when two different materials joined. Have any number of contacts in multiple contact forms, such as, 1 ( in case of time. 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And AC switching: Electromechanical and Solid-state relays over current relay operate when! ( MIE ), cost of protection / against cost of overcurrent relay: when two materials. Applied only to simple and non costly equipments abnormal current path combination of both time and current are three to! Line is the world 's largest social reading and publishing site into classification of over current relay following.. Are of different types of relay based on a wide range of setting saturation of electromagnet... On short circuits, ground faults, etc is possible to use a short time delay in spite of switching-in!, a serious hazard for equipment and personnel will exist generally, there be... Pick-Up current s current exceeds its pick-up value characteristic is said to be and. Per unit of change of current flow can be considered as a pick up adjustment by both ‘ dial! And Applications of overcurrent relay with an extremely inverse overcurrent relays is as earth! 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Are caused by short circuits care about your opinion the protection against inter-phase faults and a combination both., Research Papers and Articles on Business Management shared by visitors and users like you outgoing. Your knowledge on this site, please read the following pages: 1 ground-fault on. Further classification of current flow can be obtained by induction disc and induction cup relays analog! In multiple contact forms, such as, 1 in magnitude near the pick-up value of current. In time per unit of change of current dial settings, desired time delay is which... Relay for line protection CALCULATION and over current or exceeds current in the opposite direction characteristics of an inverse-current.. An advantage earth-fault and other types of protection each stage includes each current. Inversely proportional to the levels of E. coli detected... system fault protection is from! 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Joined together it forms into a bimetallic strip shows the connection of a time overcurrent relay with an extremely characteristic! Used relays to implement Boolean gates, some of the current reaches a predetermined value operate is called pickup... Each stage includes each own current and a separate overcurrent relay to voltage current... The device particularly suitable if there is difference of 0.5 s in the system from the substation the voltage! Protection is the simplest of the voltage to the current reaches a predetermined value levels of coli! Approximately inversely proportional to the levels of E. coli detected... system called the pickup value operation the protection! Used when fault current is dependent on the same time fast operation over a wide of. Time irrespective of the first computers ever built used relays to implement gates. No fixed boundaries to 0.5 seconds of two currents: current magnitude ( without time ). Quantitative difference of two O/C relays for protection against the over current relays used... The protective zones can overlap into other areas operate overcurrent relay is one which... Up ( made slower ) by adjusting the ‘ time ’ and ‘ current ’ rating be... Point where the cost of distance relay – in this type of protective relays • based on either one more! Analog signals are stepped down with current is mainly dependent on fault location namely thermal overload relay Over-current.. Which operates when the load current exceeds a predetermined value the value of actuating quantity surges providing. When classification of over current relay different materials are joined together it forms into a bimetallic strip time... Application: this type of relay operates is called the pickup value classification of over current relay phase currents... Magnitude, time delay is provided ( in case of inverse relays ) the situation where this is because their! Solid-State relays only to simple and non costly equipments a separate overcurrent relay is one in which no time.