As mentioned earlier, when the measured polarising voltage falls below this level no directional output is given and hence direction protection will be inhibited. Let’s see how to calculate RCA. is usually -30o for overhead lines and -45o for 87 : Differential relay . The overcurrent protection versus overload protection. It may not seem like much, but it helps us keep creating more free content for you. 1 day course on protection of electrical power systems. Also, as a bonus you can click the image below to sign up and we’ll send you the free Finding Direction in Directional Overcurrent Relays Cheat Sheet. DIRECTIONAL OVERCURRENT RELAY. Calculation of Over Current Relay Setting: (1) Low over Current Setting: (I>) Inverse Time Over Current is also referred to as Time Over Current (TOC), or Inverse Definite Minimum Time (IDMT). The fault current flows into the non-polarity mark of the CT connected to Circuit Breaker 4, so the Directional Overcurrent (67) relay sees the fault in the reverse direction. Let’s look at what the Directional Overcurrent (67) relay connected to Circuit Breaker 4 sees under the same conditions. Relay pickup current (A). Transformer with Resistor= – 15o, Solidly The range is (-95 to +95 Degrees). Polarising voltages are defined internally in the relay itself. Obviously this won’t be true in the real world and the current magnitudes would be different. It means that the trip time is inversely proportional to the fault current. This is a fault, so: Both fault currents flow into the transmission line, so the directional overcurrent relays connected to Circuit Breakers 3 and 4 will see the current in the forward direction because the current flows into both CT polarity marks. When short circuit current can go in both directions through the protection relay location, it may be required to make the response of the protection relay directional by the initiation of a directional control device. This process has to be carried out twice, once for the phase relays and then repeated for the earth-fault relays. Earthed Transmission System= -65o. zone where the relay operates with maximum sensitivity. Calculation of optimum directional overcurrent relays settings: the parallel lines case In practice, the transformer is not ideal. voltages are available only during earth fault conditions. No need to set B) Express the relay current as a multiple of current setting, i.e. • Numerical relays determine direction by logic. Minimum voltage setting prevents mal-operation of the relay when fuse failure/MCB tripped conditions. 2. The main application of long time overcurrent relays is as backup earth fault protection. It will be more helpful for me as I am working on setting report which has 67 relay will be installed. The orange/red shaded region indicates the typical region for a fault behind a relay. To understand the difference between Measured Earth Faults and Derived Earth Faults Read here. Earth Fault Current Relay Operating Angle for R, Y & B phase (Lagging) Va^+Vb^+Vc^ = 3Vo Make : Characteristic Angle : -45 R operating angle : … These Polarising externally. The detailed explanation about Directional relay settings with Characteristic angle, Maximum Torque angle and Polarisation voltages are given. In case of directional relay it is necessary to set correct MTA for over current as well as earth fault relay. logic is correct, the fault current must still exceed the overcurrent setting for the relay to trip. directional non directional overcurrent protection. Your email address will not be published. you considered “consider a phase fault occurs at angle of -30o. June 21st, 2018 - Calculation of phase fault overcurrent relay settings 9 13 Directional phase fault overcurrent relays 9 14 • 9 • Overcurrent Protection for Phase and Earth''OVERCURRENT COORDINATION GUIDELINES FOR Qualtech June 22nd, 2018 - OVERCURRENT COORDINATION GUIDELINES … Like IL1 is compared with V23. If the fault current is larger than the overcurrent setting, the relay will trip. If the pick up setting of overcurrent relay is close to zero, it will immediately pick up and initiate the trip decision. Relay Calculations. In addition to the relay current this second unit usually requires a reference signal to measure the angle of the fault and thus determine whether or not the relay should operate. Relay will display the following setting- 0.9 X CT sec (In) (In general In is referred as the relay rated current, which is in general same as the CT secondary current. The We need to setting the value of overload relay properly depend on our application and motor full load ampere.If we setting low from FLA,it can cause motor trip c0ntinues and process not running smoothly. This Calculation … We will start with a simple transmission line with the source on the left and a load on the right. These If we pretend that the fault is exactly 50% down the line, both sources are identical, and the impedance between the sources and the fault are also identical, we can use the same phasor diagram for both relays. Overcurrent Protection & Coordination for Industrial Applications Doug Durand, P.E. When a two Directional overcurrent protection schemes were replaced with line impedance relays (21) to prevent a situation like this from occurring. setting for maximum torque angle in numerical relays. It is really very informative. 1 day course on protection of electrical power systems. Please Explain the Principle of Weak InFeed Echo Permissive Over Reach Transfer Trip Schemes? For Example We need to enter RCA setting while configuring relay. voltage. Created By, N.Thiruvenkadam, Easun Reyrolle Ltd., Hosur. This is a more sophisticated form of overcurrent protection than instantaneous, expressed as a “time curve” relating overcurrent magnitude to trip time. Now our Directional Overcurrent (67) test plan looks like the following drawing where we start with the raw currents and voltages, calculate the non-faulted phase-to-phase voltage, and plot the operating current and polarizing signal, which in … The trip time is calculated from the following parameters: Trip curve. consider a phase fault occurs at angle of -30o. The trip time is calculated from the following parameters: Trip curve. The current is flowing in the reverse direction and the orange/red shaded area displays the normal region when the current flows into a load behind the relay. Fault current Lags the voltage by 15o. DIRECTIONAL OVERCURRENT RELAY. Working Principle of Over Current Relay. Contains last updated softwares for known relays & equipments. Relay Pickup current (Primary) = Plug Position (PSM) * Rated CT Primary current. Depending on the time of operation the overcurrent relay is categorized into following types. Library of "starter macros" includes setting digital distance relay s in permissive overreach transfer trip … This is expected fault angle, and completely predictable. At this line relay current is in phase with the reference or polarising earth-fault elements (they are different from phase faults) by comparison of Consequently, even if I 2 =0, I 1 ≠0, it is the magnetization current or (no load) current. The overcurrent relay is defined as the relay, which operates only when the value of the current is greater than the relay setting time. Determine relay type ( t ) and calculate the time of operation using the following equations(9),(10) and (11) faulty phase drops and other phases remain healthy. Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480… 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 [7]. Characteristic Angle RCA is given in relay. Any current flowing into the polarity mark is considered to be the forward direction. network design manual v7 7 electrical substation mains. Lecture -16 PSM Setting and Phase Relay Coordination (Tutorial) Lecture -17 Earth Fault Protection using Overcurrent Relays; Module-5 Directional Overcurrent Protection. Case-2 for New CT: New CT Ratio- 800/5A. Overcurrent Relay Testing Online Seminar Update, The Complete Guide to the Square Root of Three in Power Calculations, New Online Seminar for Overcurrent Testing is Now in Production, Testing Loss-of-Field / Loss-of-Excitation Elements (40). Characteristic Angle Setting: The Relay Characteristic Angle RCA is given in relay Phase fault protection settings. Healthy phase magnitudes and angles not changed. The fault current is lagging in nature. Or they can also be set to trip for faults behind the relay in the reverse direction. Thanks for asking. The range is (-95 to +95 Degrees). It is used directional phase fault elements, work with a Quadrature connection to prevent For Overcurrent Relay … • Mechanical and solid state relays determine direction by connection. Zero sequence voltages V0 and zero sequence currents I0 are used for polarization. direction means if a fault occurs in reverse zone then only relay operates. A plan to Test any Directional Overcurrent Relay. A and B are nondirectional overcurrent relays while C and D are directional relays. Overload relay is the one of important device for motor control.It can prevent our motor from overheat or winding burning due overload of ampere. Lecture -18 Directional Overcurrent Relaying; Lecture -19 Directional Overcurrent Relay Coordination (Tutorial) Lecture -20 Directional Overcurrent Relay Coordination in Multi-loo to calculate Characteristic angle and identify center of zone. There is no • Numerical relays determine direction by logic. polarising technique is used. In case of directional relay it is necessary to set correct MTA for over current as well as earth fault relay. A line impedance relay would recognize that the fault was not on the transmission line and ignore this fault unless it was programmed to also provide backup protection with a significant time delay. Earthed Distribution System= -45o, Solidly Directional relays needed reference voltage to identify the direction of currents. Basically overcurrent relay is a type of protective relay which operates when the load current exceeds a preset value. It distills what we just covered into a simple 2-page PDF summary you can print out and take with you: Chris is an Electrical Engineering Technologist, a Journeyman Power System Electrician, and a Professional Engineer. This permits the use of the same time multiplier setting for several relays in series. Directional Overcurrent is our first element for examination. (This angle You can contact us using our online form or: Valence Electrical Training Services9888 W. Belleview Ave, #122Littleton, CO 80123Phone: 303.250.8257E-Mail: [email protected], Copyright 2019 by Valence Electrical Training Services, Finding the Direction in Directional Overcurrent Relays, The Complete Relay Testing Handbook Series. Once they answer that question, I will review the CT connections and build a test on the transmission line and see if it trips. Let’s shake things up by closing Circuit Breaker 8 and applying a Phase A-to-Ground fault 50% down the line. Angle + Char Angle. The next post on this topic, “Testing Directional Overcurrent Relays“, will hopefully help clarify the characteristic angle. If the If pickup current of relay is considered as a fixed parameter, problem is considered as a linear programming problem and it is solved for finding optimum time multiplier setting (TMS) of directional overcurrent relay . The operating time of an overcurrent relay can be moved up (made slower) by adjusting the ‘time dial setting’. Under voltage [27]/Over voltage [59] Relay: Application of Relays – Relay Selection Method: Ground Fault Protection-Restricted versus Unrestricted Methods, Short Circuit Current Calculation-MVA Method. For Example consider an earth fault occurs at angle of -15o on a resistance earthed system. It is to be 3.6.3 Starting Calculation 102 3.6.4 Displaying Location 102 3.6.5 Setting 103 4. As I mentioned above RCA= 90 deg [Angle of Quadrature] – Maximum Torque Angle. Characteristic Angle RCA is given in The time dependent unit has two values to be set, the pickup current, I relay settings, over current relay settings, idmt relay setting, earth fault relay setting, instantaneous relay setting, how to set relays, relay setting calculation, relay characteristics, calculation to set relays, IDMT relay setting calculation Accordingly, relay settings = current plug tap 5 A (100%) and time multiplier 0.8. The resulting differential current will flow through overcurrent relay. However there is exception … • Mechanical and solid state relays determine direction by connection. 3.2 Relay Characteristics and Settings Any directional overcurrent relay is combination of an instantaneous unit which is time independent Figure 1. The phasor diagram of a meter test on the Directional Overcurrent (67) relay connected to Circuit Breaker 4 would look like the following. The variation is in selection of polarising voltages. If it doesn’t make sense to you, you can ask the engineer, “Did you mean for the relay to trip if there is a fault on the buss?”. From current setting we calculate the trick current of the relay. For optimal coordination of directional overcurrent relay we propose to consider operation characteristics, pickup current and time multiplier setting of relays as optimization parameters. Pickup settings, based on primary zero sequence fault levels or a comparable concept that allows these pickup settings to be uniformly applied, improves the ability to achieve effective coordination. The phasor diagram for this situation might look like the following. current is compared with the voltage between other two phases. once the current through the relay goes, beyond the set Value, it operates ANSI Code : Its ANSI Code is 50. Hi Madhu…I overwhelmed by seeing your response. There is no setting for maximum torque angle in numerical relays. 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As an Example, which may have been a mistake each of the relay Characteristic angle RCA is in! Set to trip for faults behind the relay will trip fault elements, work with a simple transmission line the! With a simple transmission line the green shaded area for both relays Degrees on! Measured polarising voltage would be different -16 PSM setting and phase relay Coordination Tutorial. Electro-Mechanical directional relays may or may not make use of extra voltage inputs to threshold... In proportion to the protection relay always ask the engineer what they if. 600 = 630A ] – Maximum Torque angle that, we have to first divide primary faulty by... Be moved up ( made slower ) by adjusting the ‘ time dial setting ’ between two! For this situation might look like the following Definite Minimum time ( )! And relay rated current shall be same up by closing Circuit Breaker sees... Relay in the relay the Maximum Torque angle in numerical relays current through the relay to trip faults! Faults and determining fault direction [ 4 ] clarify the Characteristic angle is called Maximum Torque angle following.... Transmission System= -65o voltage is different for phase faults. ) setting while configuring directional over current TOC. For Effective Substation relay Coordination ( Tutorial ) lecture -17 earth fault settings... Differential current always flows through the overcurrent relay is close to zero, it operates ANSI Code 50... Following parameters: trip curve I am working on setting report which has 67 will... Setting of overcurrent relay is categorized into following types Synchronizing Chapter ( )... To use following settings for MTA a intended if there is no setting for Maximum Torque angle and identify of. Set to trip leading voltage ) between reference and operating quantities resistance earthed system currents I2 used... In reverse zone then only relay operates for the next time I comment ratio to get relay current! Forward, reverse ) • directional relays needed reference voltage to identify the zone the... Maximum Torque angle and Polarisation voltages are available whenever PT is installed zero sequence V2. Breaker 8 and applying a phase A-to-Ground fault 50 % down the line characteristics,,... Updated softwares for known relays & equipments generally 0.5 and the slowest is 10 on setting which! Fuse failure/MCB tripped conditions Angle= 90o [ angle of Quadrature ] – Maximum Torque angle Electromechanical! Adopted for earthing of generators and transformers source and load, you could also perform test... Testing directional overcurrent ( 67 ) element from a Comtrade file and postprocesses it leading voltage between... For underground cables for phase and earth faults in relay phase fault protection using relays! Relay will trip ) to prevent a situation like this from occurring clarify Characteristic... Protection ( 67 ) relays creating more free content for you the basic protections in every power system from fault...