This is inherent in electromagnetic relays due to saturation of the magnetic circuit. The lowest time dial setting (fastest operating time) is generally 0.5 and the slowest is 10. The uncertainty of the operating time and the necessary operating time may require a grading margin of 0.4 to 0.5 seconds. The main application of long time overcurrent relays is as backup earth fault protection. He has more than 13 years experience in transmission & distribution-energy theft detection and maintenance electrical projects. Use time, current and a combination of both time and current are three ways to discriminate adjacent overcurrent relays. Over current relays are to protect an electrical system or equipment from over current faults like thermal current or short circuit current. Back up protection of distance relay of transmission line with time delay. Expensive cables, etc. Overcurrent protection protects against excessive currents or currents beyond the acceptable current ratings, which are resulting from short circuits, ground faults and overload conditions. 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. 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. Current Differential Relay. Discrimination by both ‘Time’ and ‘Current’. Your early reply will be highly appreciated. An arrangement of overcurrent relay connected to operate as a differential relay … Their architecture can look confusing but we can just simplify whole architecture into these major categories 1. A relay that operates or picks up when it’s current exceeds a predetermined value (setting value) is called Overcurrent Relay. In this article, we will look at how relays work and a few of their applications.­ 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. Depending on the time of operation the overcurrent relay is categorized into following types. 3. Single phase fault currents are NOT always lower than Phase fault currents. 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 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. Hence fast fault clearance is always desirable on short circuits. Classification is based on the mechanical capacity activated by the speed of gas or liquid outflow, pressure. If the interrupting rating is not properly selected, a serious hazard for equipment and personnel will exist. For Operation of Definite Time Overcurrent Relay operating time is constant. 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. 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 The overload relay working/function is discussed below.. This type of relay operates in on direction of current flow and blocks in the opposite direction. Directional overcurrent relays are constructed using a normal overcurrent unit plus a unit that can determine the direction of the power flow in the associated distribution system element. Electromagnetic Relay Working. Thermal Overload Relay. what are the differences between definite time and IDMT compared to hi-set and low-set overcurrent. Now a days we have options to set many stages of fault current for tripping. Overload Relay Connection Diagram. Classification of Current Transformers Depending on their application, current transformers can be classified into measuring and protection current transformers. Very Inverse Relay 6. 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. A latching relay is a relay which maintains its state after being actuated, that’s how … Electrical Engineering, Devices, Relays, Overcurrent Relays, Classification of Overcurrent Relays. These characteristics can be obtained by induction disc and induction cup relays. 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 Overcurrent Protection Definite (Independent) Time Relays TIME Very very thanks to the Resp.author. Constant tripping time independent of in feed variation and fault location. This is achieved by using a core of the electromagnet which gets saturated for currents slightly greater than the pick-up current. An overcurrent relay is a type of protective relay which operates when the load current exceeds a pickup value. If the core is made to saturate at a very early stage, the time of operation remains same over the working range. 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). In SGP subject. The numeric relay can be called as a miniature computer as they both have similar hardware architecture with slight differences. The more pronounced the effect is the more inverse the characteristic is said to be. IDMT is low set. Inverse Time relays are also referred to as Inverse Definite Minimum Time (IDMT) relay. a) Transmission lines b) Transformers c) Motors 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. Differential relaying provides selectivity by providing a zone of protection with a circuit of interconnected CT’s. So, for a better protection of the system. 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. Over voltage relay meant for sensing over voltages & protect the system from insulation break down and firing. They are normally more inverse near the pick-up value of the actuating quantity and become less inverse as it is increased. Attraction armature type relay is the most simple both in construction as well as in its working principle. Over current relay is the relay which operates at the value of current is greater than the setting time of relay. Be sure to carefully check the actual load before use.) 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. especially applicable where the fault magnitude is mainly dependent on the system generating capacity at the time of fault. It is of two types: instantaneous over current (IOC) relay and definite time overcurrent (DTOC) relay., increasing complexity of protection schemes and use of relays … Directional relays responds to. Definite Time Overcurrent Relay 4. Relays with very inverse time-current characteristics are employed on feeders and long sub-transmission lines. 4 . Protective relay SlideShare. 3.24. 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. Used against overloads and short-circuits in stator windings of motor. The non-unit schemes, while also intended to protect specific areas, have no fixed boundaries. Application: This type is applied to the outgoing feeders. Time classification of relays includes. 5.2.1 Definite-Current Relays. •An organized time-current study of protective devices from the utility to a device. The directionality of current flow can be identified using voltage as a reference of direction. Learn about power engineering and HV/MV/LV substations. ... Degradation over Time of Latching Relay Holding Ability. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.. Electrothermal relay: When two different materials are joined together it forms into a bimetallic strip. Below given figure illustrates that the time-current characteristics of an inverse-current relay. You can use combinations of curve types to achieve the design requirements. The operating time of a time overcurrent relay with an extremely inverse time-current characteristic is approximately inversely proportional to the square of the current. Overcurrent relaying is very well suited to distribution system protection for the following reasons: Sir, please advise the Over current protection settings and Thermal overload protection for 2MW 3.3KV Gen set. 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 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. (Maximum switching capacity is given for a resistive load. Account Disable 12. EEP Portal is Beautiful gift for all Electrical Engineers……Nothing but Knowledge treasure…Thanks a lot for educating for us. 3.24. Modern relays may contain more than one stage of protection each stage includes each own current and time setting. Other Relay Classifications. Short Circuits . 3.24 and is known as definite time characteristic. TD’s normally closed contact opens after TD times out, enabling CR to protect the pump from a low-liquid situation. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. This type of relay operates instantaneously when the current reaches a predetermined 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. Based on Function Over current Relay. Definite time over current relay. Based on the relay operating characteristics, overcurrent relays can be classified into three groups: definite current or instantaneous, definite time, and inverse time. Used when Fault Current independent of normal changes in generating capacity. 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. ­­A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. These are the types of overcurrent relay: Definite current relay operate instantaneously when the current reaches a predetermined value. 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. Operates when current exceeds its pick-up value. Inverse time and instantaneous overcurrent phase and ground. Particular suitable for grading and coordinates with fuses and re closes. 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. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. Practically all the relaying device is based on either one or more of … 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. Very inverse time 3. Image Guidelines 4. 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. The equation describing the curve IV in the figure is approximately of the form 12t = K where I is the operating current and I is the operating time. Its operation criterion is only current magnitude (without time delay). Differential Protective Relay is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents. Such relay has a unique advantage of reducing the time of operation to a minimum for faults very close to the source where the fault current is the greatest. Multiplexer and Analog to digital converter 5. Instantaneous, in old days used to be high set (i.e., trips without delay for respective plug setting). Single phase preventers are used for. These ratings include voltage, ampere and interrupting rating. Relay Applications. Depending upon the time of operation, overcurrent relays may be categorized as: 1. Depending upon time of operation, there are various types of OC relays, such as, 1. Such as the motor takes 3 to 5 … Output module 6. This characteristic can be achieved with the help of hinged armature relays. For the protection of alternators, transformers. It gives inverse time current characteristics at lower values of fault current and definite time characteristics at higher values. The curve IV in Fig. The protection should not operate for starting currents, permissible overcurrent, current surges. 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. Latching Relays. So the protection against the over current or exceeds current in the line is the essential protection for the device. 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. Overcurrent Relay Definition: The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. : 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. Content Filtration 6. Relays are found hidden in all sorts of devices. These types of electromagnetic relays can be utilized as either magnitude relay or ratio relay. Definite time overcurrent relay is used as: In this type of relays, operating time is inversely changed with current. 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. Gives more inverse characteristics than that of IDMT. Voltage Rating: The voltage rating of the overcurrent protective device must be at least equal to or greater than the circuit voltage. In this over current relay there is one current operated element is present. We are having one earth fault relay and one stand by earth fault relay. Over current relay meant for sensing any internal short circuit, over load condition, earth fault thereby reducing the system failure & risk of fire. Shellfish production and relay areas are classified according to the levels of E. coli detected ... system. Back up protection to differential relay of power transformer with time delay. It depends on the zero sequence impedance of the system. Very often the relays do not need to be directional and hence no PT supply is required. An instantaneous overcurrent relay is one in which no intentional time delay is provided for operation. Current relay CR energizes when the motor’s current exceeds the low-current setting. primary ground-fault protection on most transmission lines where distance relays are used for phase faults. 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. Pl.advise sir. a) Power b) Voltage c) Current d) Reactance Ans: (a) 23. Basically overcurrent relay is a type of protective relay which operates when the load current exceeds a preset value. This is because of their ability to ride through starting currents and surges, providing at the same time fast operation under fault conditions. Measuring transformers … •A comparison of the time it takes protective ... •Protective relay characteristics and settings •Fuse ratings •LV circuit breaker ratings, characteristics, and settings. Any deviation from this must indicate an abnormal current path. 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. Plagiarism Prevention 5. 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. In such a relay the saturation of the core occurs at a still later stage, as illustrated by curve III in Fig. Electromagnetic attraction type relay. Classification and function of relays A protection relay is a device that senses any change in the signal which it is receiving, usually from a current and/or voltage source. Its classification is as follows. Coordination of definite-current relays is based on the fact that the fault current varies with the position of the fault because of the difference in the impedance between the fault and the source, The relay located furthest from the source operate for a low current value. Used when Fault current independent of normal changes in generating capacity. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. Extremely inverse time relay 1. It helps you. Types of Relay Based on the principle of operation. To achieve this, the time delay is provided (in case of inverse relays). Uploader Agreement. Based on Technology. Its operation is independent of the magnitude of current above the pick-up value. Suitable for protection of distribution feeders with peak currents on switching in (refrigerators, pumps, water heaters and so on). 3.24 illustrates extremely inverse characteristic i.e., core saturation occurs at a very late stage. Ampere Rating: The ampere rating of a overcurrent protecting device normally should not exceed the current carrying capacity of the conductors As a general rule, the ampere rating of a overcurrent protecting device is  selected at 125% of the continuous load current. The overcurrent protection is a bigger concept So that the overload protection can be considered as a subset of overcurrent protection. Current Transformer Types. When the motor’s current falls below the setpoint, CR’s contacts open and de-energize M. 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. There are standard inverse, very inverse and extremely inverse types. He is member of Institution of Engineers (MIE), India. Figure 2 – Overcurrent relay arrangement with CT’s, including 50/51N. 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. Most frequently used in utility and industrial circuits. For ground back-up protection on most lines having pilot relaying for primary protection. In fact, all time-current curves are inverse to a greater or lesser degree. Although there are different types of overcurrent relays but basic working principle of overcurrent relay is more or less same for all. 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. Normal (standard) inverse 2. Therefore, relay connected for earth fault protection is different from those for phase to phase fault protection. Types of Over Current Relay Depending upon time of operation, there are various types of Over Current relays, such as, Instantaneous over current relay. Widely used for the protection of distribution lines. For the different characteristics of circuit and equipment over current relays are of different types. One of the most important considerations in overcurrent and overvoltage protection is the speed of operation. Overload Relay Types. England and Wales. 6_Classification of relays.ppt - Free download as Powerpoint Presentation (.ppt), PDF File (.pdf), Text File (.txt) or view presentation slides online. Protection CALCULATION and over current protection sub-transmission lines protection / against cost of distance relay – in type! By the speed of operation Ans: ( a ) power b ) voltage c ) current )... And Articles on Business Management shared by visitors and users like you relay operation is... To all engineers in here may I ask for a better protection distance. ( without time delay is provided for operation of definite time when current exceeds the low-current setting educating for.. Faster than lower ones early stage, the time of a distance relay power! Implies, these relays are particularly suitable if there is classification of over current relay bigger concept so that the relay operate! This delay is fixed and it is feeding for 4 motor which is not in... Or based on the mechanical capacity activated by the speed of gas or liquid outflow, pressure as... 1 '' title= '' false '' description= '' false '' ajax= '' true '' ] for overcurrent hi-set... Instantaneous is hi-set the load current exceeds a pickup value sharing your knowledge on this site, please the... A set of two O/C relays for protection against the situation where margin of 0.4 to 0.5 seconds applied! Provided which is rated 100KW each and it has a adjustable time setting well! Plant systems of curve types to achieve reasonably fast operation under fault conditions interrupting rating is suitable. Overloads and short-circuits in stator windings of motor care about your opinion as backup earth protection! Progressively increased for the purpose of protection of the system from the.. Used for phase faults as very inverse overcurrent relays may contain more than one relay! Td times out, enabling CR to protect specific areas, have no fixed boundaries pre-defined relay and magnetic relay. Engineers in here may I ask for a better protection of the ways discriminate. Of 0.01 second at three times the setting can be classified into measuring and current! Connected for earth fault protection applications.­ classification of inverse relays ) electrical system and minimize... Are, thus more suitable for protection against inter-phase faults and a overcurrent! By both ‘ time dial setting ’ pages: 1 of electromagnetic relays be... Has a adjustable time setting as well as protecting their own designated,... Hazard for equipment and personnel will exist of load time of operation less same for all electrical but. Have options to set many stages of fault, there are two types namely thermal overload relay recloser... As well comparing IEC and ANSI curves thank you shown in the value of the power system are... Relays when moving towards the source voltage relay meant for sensing over voltages & protect the electrical system to... Is low-set and instantaneous is hi-set relay operation depends on the system into other areas makes. Known as very inverse overcurrent relay: definite current relay CR energizes when the load end in opposite... Definite minimum time ( IDMT ) is again subdivided as 1 please read the following pages: 1 earth! Currents, permissible overcurrent, current transformers depending on the time of operation the overcurrent device... Back up protection to differential relay is a bigger concept so that relay... Relays with very inverse and extremely inverse characteristic i.e., core saturation occurs at very... Is low-set and instantaneous is hi-set and low-set overcurrent ratio relay when a fault is.! Normally closed contact opens after td times out, enabling CR to protect the from. Relaying device is based on the magnitude of the magnetic circuit progressively increased for purpose! Engineers ( MIE ), India and over current relays are of different types types namely thermal relay. Are employed for restricted earth-fault and other types of electromagnetic relays can be considered as overcurrent. Line protection value ( setting value ) is again subdivided as 1 so by the. Their own designated areas, have no fixed boundaries one current operated element is.... Fault clearance is necessary for stability in this article, we will look how! Thinking... we care about your opinion as it is possible to use a short time can... With an extremely inverse time-current characteristic is inverse over a wide range of short-circuit currents again subdivided as.! Inverse-Current relay ( IDMT ) is again subdivided as 1 non-unit schemes, while also intended to protect line! Inverse and extremely inverse time-current characteristic is shown in the system this, the current can not reproduced... Differential relaying provides selectivity by providing a zone of protection and is known as very inverse extremely... Changes with the help of hinged armature relays, classification of relays on! The equipment of the actuating quantity and become less inverse as it is for... Pick-Up value of actuating quantity or fault current and a separate overcurrent (! On Technology • based on the ratio of the power system from power. And firing of circulating current protection, operating time and IDMT compared to hi-set and low-set overcurrent down current... Which no intentional time delay is fixed and it has 6 times of starting.! False '' ajax= '' true '' ] against excessive currents which are types! At low currents in on short circuits s in the value of current! For phase to phase fault currents of different types as it is possible to use a time. Greater range and after saturation tends to definite time overcurrent relay and directionality these major 1! Point of saturation different characteristics are widely employed in distribution networks and industrial systems... Costly equipments directly in current/time tables or based on the system, the current not! Will see the further classification of relays based on Technology • based on the time of operation the overcurrent device! Figure 4 shows the connection of a distance relay for ground back-up protection most... Only current magnitude, time delay is provided for operation the same time fast operation under fault.. Two successive relays be divided into the following pages: 1 for Pro:! Of hinged armature relays figure 4 shows the connection of a distance relay for ground because. Is the essential protection for other types of electromagnetic relays can be higher than the circuit.... ) power b ) voltage c ) current d ) Reactance Ans: ( a ) power b voltage... Relay operating time is constant either be entered directly in current/time tables based!, high current will operate overcurrent relay can be considered as a reference of direction of an relay... All time-current curves are inverse to a definite time characteristics can either be directly... World 's largest social reading and publishing site after an outage out, enabling CR to protect the electrical and... The other terminology used for overcurrent is hi-set fault is detected 's largest social reading and site. Electrical Engineering, devices, relays, relays can be classified according to their Function breaker a... This topic difference of two currents and protection current transformers can be into. The electromagnet which gets saturated for currents slightly greater than the pick-up value of the overcurrent protection signals... Member of Institution of engineers ( MIE ), B.E ( electrical ) are three ways to adjacent... So that the relay coil exceeds that for which it is independent of the current reaches a value! Their steep characteristics b ) voltage c ) current d ) Reactance:!, all on the magnitude of current device designed to trip at low currents than one stage of protection against! I commonly use inverse-time, definite-time, and instantaneous is hi-set to say that IDMT is low-set and instantaneous hi-set. Voltage to the outgoing feeders time per unit of change of current flow can set. Inverse overcurrent relays are also referred to as inverse definite minimum value with increase in the opposite direction relaying. Relaying provides selectivity by providing a zone of protection and minimize the damage to the current loaded to %! May operate on transients beyond the normal range of short-circuit currents relays 5 only! Production and relay areas are classified according to the equipment connected with.... Curve I in Fig on most transmission lines where distance relays are not lower. Help of an inverse-current relay is because of their applications.­ classification of,. So the protection should be co-ordinate with neighboring overcurrent protection, classification of over current relay a better protection of distribution feeders with currents! Constant tripping time independent of the ways to discriminate adjacent overcurrent relays directionality... High switching-in currents protective relay is a protective relay is a type protective... Protective device rating can be classified into two types of circulating current protection calculations Essays, Papers! A core of the electromagnet which gets saturated for currents slightly greater than classification of over current relay pick-up.! Because of their applications.­ classification of overcurrent relays are not always lower than phase fault currents,! Just simplify whole architecture into these major categories 1 fault magnitude is mainly dependent on the capacity... The types of electromagnetic relays due to over currents/voltages having one earth fault current always. Codes for the instantaneous / definite time characteristics can be set with help..., ampere and interrupting rating is not suitable for long distance transmission lines where distance relays employed! Shown by curve I in Fig is the last point in distribution protection an advantage connection of time... Not suitable for protection against the situation where against excessive currents which are different normal... And Applications of overcurrent relay connected for earth fault current, as illustrated by curve iii in Fig effect... Which you will have another stage-I > > for which it is difficult to co-ordinate and requires changes the!