Protective Relay _ Circuit, Working, Types, Codes & Its Applications.pdf
- 1. Protective Relay : Working, Types, Circuit Applications An electrically operated switch like a relay plays a key role in controlling an electrical circuit th independent low-power signal, otherwise used where a number of circuits should be controlle single signal. First, relays were used as signal repeaters within long-distance telegraph circuit that, widely used in early computers & telephone exchanges to achieve logical operations. Th types of relays available and each type is used based on the requirement. So this article discu overview of a protective relay or protection relay – working with applications. What is a Protective Relay? A protective relay definition is; a switchgear device used to detect faults & begin the circuit bre to separate the faulty element of the system. These relays are self-contained & compact devi abnormal conditions occurring within the electrical circuits by measuring the electrical quant which are dissimilar in fault & normal conditions. In fault conditions, the electrical quantities m current, voltage, phase angle & frequency. The protective relay diagram is shown below. Projects › Project Ideas IC › Embedded Sensors Components Tools › Info ELECTRICAL ELECTRONICS COMMUNICATION PROJEC HOME › › › ROBOTICS
- 2. Protection Relay Protective Relay Working Principle A protective relay is used to protect the device once the fault is detected within a system. Onc detected, the fault location is found and then provides the tripping signal to the circuit breake relays work on the two principles like electromagnetic attraction & electromagnetic induction Electromagnetic attraction relay simply works on both supplies like AC & DC and it attracts th electromagnet poles. These types of relays instantaneously work & it doesn’t delay while the Electromagnetic induction relay simply works on only AC supply & it utilizes the induction mo the torque. So these are regularly used like directional relays to protect the power system & a speed-based switching operation applications. Protective Relay Types Protective relays are available in different types which are used based on requirements. Overcurrent Relays Overcurrent relays operate through the current. The overcurrent relays may get actuated throu This relay includes a pick-up value and this relay activates once the measurement and quanti exceed that pick-up value. Overcurrent Relay These relays are available in two types instantaneous and time-delay types where these two r provided within a single container. These two are activated by a similar current; but, their sepa
- 3. values can be separately adjusted by changing the tap settings within the input. Overcurrent relays are not expensive, so used on low-voltage circuits and also in specific high system applications. The main disadvantage of this relay is, it may also select the fluctuation well as the faults within the nearby zones. Electromechanical Relays Electromechanical relays are the earliest relays but they are using in many areas still today. T works using a magnetic field generated by an electromagnetic coil once a control signal is pro This relay changes the voltages & currents to electric, magnetic forces & torques that push ag strains within the relay. The spring strain & taps on the electromagnetic coils within the relay a processes through which a user sets a relay. Please refer to this link to know more about an Electromechanical Relay. Electromechanical Relay Directional Relays These relays are activated by the flow of current in a certain direction. It may detect a variatio actuating & reference current. This relay is used in combination with some other relays like ov so that the capacity & selectivity of the protective relay system will improve. This relay simply variation of the phase angle between both the actuating & a reference current is known as the quantity.
- 4. Directional Type Distance Relays This distance relay is used to distinguish between normal operating conditions & a fault and a differentiates faults within a particular area & within a different element of the system. The di operation is inadequate to a particular range of impedance pickup values. This relay picks up impedance measurement is low or equivalent to the preferred pickup impedance value. Distance Type In this relay, the parameters like voltage & current are balanced from each other & this relay re voltage & current ratio which is the transmission line’s impedance from the location of the rela point of interest. This impedance is used to determine distance through a transmission line, t as a distance relay. These relays are available in different types like reactance, mho & impeda Please refer to this link to know more about Distance Relay. Pilot Relays
- 5. The pilot relay is used to determine whether a fault is inside or outside the protected line. If th internal toward the protected line, then all the circuit breakers (CBs) at the line terminals are t maximum speed. Similarly, if the fault is external toward the protected line, then the circuit bre blocked or prevented. There are three types of pilot relays available wire, power line carrier & m which are used for protective relaying. Pilot Relay Differential Relays A differential protective relay simply works by contrasting the main difference among the ente leaving current magnitude as well as values. If the difference is above the pickup value then th be separated & the breaker circuit (CB) is triggered. Differential Type Protective Relay Circuit
- 6. The protective relay is used to detect abnormal conditions within the electrical circuits by me different electrical quantities constantly under normal as well as fault conditions. The electric which may vary in fault conditions are; current, voltage, phase angle & frequency. A typical protective relay circuit is shown which can be separated into three parts which are d below. Protective Relay Circuit The first part of the circuit is the primary winding of a CT which is also called a current tran CT is connected with the transmission line in series to be protected. The second part includes the secondary winding of the current transformer, CB & the opera relay. The final part of the circuit is the tripping circuit which may be either AC/DC. So it mainly in source of power supply, the circuit breakers trip coil & the stationary contacts of the relay. Working Once a short circuit at the ‘F’ point on the transmission line occurs, then the flow of current w transmission line will increase to an enormous value. So this causes to flow heavy current thr relay coil and makes the protective relay function by simply closing its contacts.
- 7. Consequently, it closes the trip circuit of the CB and makes the CB open & separating the faul from the system. So in this manner, this protective relay ensures the security of the equipmen from breaking & typical working of the system. Protection Relay Codes In electrical power system design, the ANSI codes indicate what features a protective device relay/circuit breaker. These devices simply protect electrical systems as well as components once an electrical fault takes place. ANSI codes are very useful in identifying medium voltage microprocessor device functions. The protection relay ANSI codes are listed below. Protection of Current Functions The protection of current functions with codes is listed below. ANSI 50/51 indicates phase over current. ANSI 50N/51N (or) 50G/51G indicates an earth fault. ANSI 50BF indicates breaker failure. ANSI 46 indicates an unbalanced or negative sequence. ANSI 49 RMS indicates thermal overload. Directional Current Protection The protection of directional current with codes is listed below. ANSI 67 indicates the directional phase over-current. ANSI 67N/67NC indicates a directional earth fault. Directional Power Protection Functions The protection of directional power with codes is listed below. ANSI 32P indicates directional active over power. ANSI 320/40 indicates directional reactive over power.
- 8. Machine Protection Functions The machine protection function with codes is listed below. ANSI 37 indicates phase undercurrent. ANSI 48/51LR/14 indicates a locked rotor or extreme starting time. ANSI 66 indicates starts per hour. ANSI 50V/51V indicates voltage/ restrained over current. ANSI 26/63 indicates Buchholz/thermostat. ANSI 38/49T indicates monitoring of temperature. Voltage Protection Functions The voltage protection function with codes is listed below. ANSI 27D indicates a positive sequence under voltage. ANSI 27R indicates remanent under voltage. ANSI 27 indicates under voltage. ANSI 59 indicates overvoltage. ANSI 59N indicates displacement of neutral voltage. ANSI 47 indicates a negative sequence overvoltage. Protection Functions of Frequency The protection functions of the frequency with codes are listed below. ANSI 81H indicates over-frequency. ANSI 81L indicates under frequency. ANSI 81R indicates frequency rate change. ANSI 81R indicates frequency rate change. Protection Relay Testing
- 9. In current power systems, protection relays play a key role so their reliable operation has to ch times. So, these relays should be tested during their life cycle. Additionally, relay testing on a n required to make sure the right operation is maintained. If the testing of the protection relay is well on a regular basis, electrical faults may occur and cause equipment damage & harm to w There are three types of protection relay tests that are performed bench testing, commission maintenance testing which are discussed below. Bench Testing This test is performed to test the relay on its own & that it equals the design. This avoids mor as time-consuming troubles from occurring at later stages within a project. Commissioning Testing When the electrical system has been designed, commissioning the protective relay involves c larger system works as expected. So, for instance, once the protective relay is connected to t then it should work as expected, and respond to interlocks & other replicated conditions. In th function of the relay will have been verified. Maintenance Testing Once maintenance testing is performed then the whole design purpose is assumed, however, the protective relay should be verified for below operation. Apart from particular failures, this notice changes within the characteristics of a system like network loads being modified over long-term changes may need the protection relay to be reprogrammed to make sure the estim is maintained. While doing protection relay testing there are many parameters that need to be tested freque the type of test like the relay’s visual inspection, connection parts, opening & closing of circuit protection functions, logic functions, protective relay binary & analog input and outputs, Prima Insulation resistance testing & secondary injection testing. Advantages & Disadvantages
- 10. The advantages of a protection relay include the following. This relay monitors different parameters continuously like current, voltage, power & freque It Improves system stability through the isolation of defective section This relay clears the error in no time, so it reduces the damage. This relay detects failures & faulty sections in the system. It reduces the fire risk. It provides electrical security & protects a person while working on the system. It improves the performance, stability & reliability of the system. The operation of these relays is very fast & also very fast to reset. These can be utilized in both the power supplies like AC & DC. These relays simply work in milliseconds & the outcome is instant. These are the most reliable, robust, compact & very simple. It is applicable in different fields. The disadvantages of a protection relay include the following. A protective relay cannot avoid faults within a power system, so, this relay spends more tim system monitoring. It needs periodic maintenance as well as testing not static relays. The operation of this relay can be simply affected because of the component’s aging, pollu which results in false trips. These relays provide security and consistency which is required to operate with confidence Applications The applications of a protection relay include the following. A protection relay is used in serve electrical protection. The protection relay detects a problem during its early stage & significantly reduces or elim to equipment. This relay device is mainly designed to trip a CB (circuit breaker) once a fault is noticed. This relay works like a detecting device, so it detects the faults, knows its position & lastly i tripping signal to the circuit breaker
- 11. This is a switchgear device used to detect the faults & begins the circuit breaker operation faulty element from the system. These are very helpful in high-voltage & medium-voltage protection and overcurrent to com protection. What are the Key functions of Protective Relays? The main functions of protective relays are; It detects the presence of a fault. It detects the fault location. It detects the presence of fault type. It closes the trip circuit & operates the CB (circuit breaker) to separate the faulty system. What type of protective relay is used in an induction motor? The MPR or motor protection relay is used for protecting the high-voltage induction motor. What are the essential elements of a protective relay? The essential elements of a protective relay mainly include a sensing element, comparison el control element. What are protective relays used for? A protective relay is used to detect faulty equipment and monitors the current & voltage with What are the types of relays used for 3-phase protection? A 3-phase voltage control relay is used in three-phase protection. Thus, this is an overview of a protective relay – working with applications. In order to operate relay satisfactorily, it must have these qualities like speed, selectivity, reliability, simplicity, sen economy, etc. Here is a question for you, what is a circuit breaker? SHARE THIS POST: Facebook Twitter Google+ LinkedIn Pinterest
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