The relay operates as soon as the current gets higher than a preset value. trailer << /Size 237 /Info 190 0 R /Root 193 0 R /Prev 367817 /ID[<72f082dab9c6bec1e89516da9ea07cff><82ed7aa8271f32b9d527c68813e1fcd4>] >> startxref 0 %%EOF 193 0 obj << /Type /Catalog /Pages 184 0 R /Metadata 191 0 R >> endobj 235 0 obj << /S 941 /Filter /FlateDecode /Length 236 0 R >> stream SetC REAL Sets user-dened C parameter for inverse curve cal-culation (see Equation 1). Extremely Inverse Directional overcurrent Relay Go back to Index 1. 2. It will be necessary Relay operation time only, user to add allowances for error and switchgear operation time. I I r r r 8. IEC long-time inverse: IEC normal inverse _:12691:109: Inverse-T 1:Reset : instantaneous disk emulation . The work strategy is presented in three steps: solving the coordination problem by designing non standard curve for 7SJ602 relay, minimizing the operating time using Definite Time curve and creation of self back up protection in the proposed model. The formula and curve constants used to determine the trip times are shown below: t ( I) = T M S ( k ( I I s) 1) A typical fuse time-current curve is shown below. time + trip coil delay time + circuit breaker mechanism operating time. Text: time, moderately inverse , inverse ,very inverse , extremely inverse ; see time/ overcurrent curves , inverse ; see time/ overcurrent curves ; curves apply up to 20 x pickup or 20 x sensor (whichever is less , amp CT input s ANSI , IAC or IEC/BS142 curves s 20 260 V AC/DC control power , is set to OFF, the TOC is disabled. This relay is referred as definite (instantaneous) overcurrent relay. There are different characteristic curves available for Inverse Definite Minimum Time (IDMT) overcurrent relays. Overcurrent relaying is one of the most simple and economical types of protection used for power system feeders, transformers, generators and motors. The consent submitted will only be used for data processing originating from this website. Trip curve Relay pickup current (A) Fault current (A) Time Multiplier Setting (TMS) See Also Cable Sizing Calculator AS/NZS 3008 U.S. Most instantaneous overcurrent relays operate on minimum operating time. The fact that the curves are based on a mathematical formula makes it easy to sense Since the advent of simple electromechanical elements, to advanced microprocessor applications used in modern relays, overcurrent protection has been at the heart of the power system for centuries. The IEC who develop international standards for all electrical, electronic and related technologies, have defined 4 curves to be used. Calculate the tripping time for a relay set at 1000A pickup current and TMS setting of 1 (IEC Very Inverse) with 10kA of fault current. ANSI extremely inv. ANSI Time-Dial setting is given by the formula: Time Dial Setting = [Desired IEC Time-Multiplier Setting + 0.0370] / [0.1037] Table of Coefficients for Use with the CurveGen Program Coefficients Curve Type A B C P IEC Extremely Inverse 5.334 0 1 2 IEC Very Inverse 0.900 0 1 1 IEC Inverse 0.009333 0 1 0.02 0000016942 00000 n Schneider equivalent time setting. Instantaneous Overcurrent Relay - Definite Current Operates in a definite time when current exceeds its Pick-up value. G. Pradeep Kumar (2006), Power System Protection, notes on Power System Protection Training, Visayan Electric Company, Cebu City, Philippines. Extreme inverse > very Inverse > Standard Inverse > Long Time Standard Inverse. The phase current input quantities can be programmed as fundamental phasor magnitude or total waveform RMS magnitude as required by the application. ETAP Enterprise Solution for Electrical Power Systems Online Help. 0000005990 00000 n An example of data being processed may be a unique identifier stored in a cookie. 0000016920 00000 n Your feedback is greatly appreciated. WireSizeCalculator.net | m{+L{%>>c3 +`2wPz`h#X3>*.48p$4A=LXG&+y?bRb)ji~)]3.PH"+!e#r$8Y!ib"EQE0Fa&,%&%Dn P$EHM$BEQ>hafK.$:$Lvk0qiAp>}An* 6A{`&%TmRa/vAOXH-sGG\\o; IEC Extremely Inverse . S_\Mh[ settings between 0.05 and 1. maximum clearing time when the strip completely breaks and the arc fully extinguished. This allows slow operation on overload and fast on fault. Basically, four types of relays are being manufactured based on their characteristics curve (Characteristics curve means the relay manufacture defines how the relay operates with respect to time). t(I)= TMS \displaystyle \left( \frac {k}{\displaystyle \left(\frac{I}{Is}\right)^\alpha-1}\right) %PDF-1.2 % The equation for operating time from IEEE C37.112-1996 trip curves is as follows: Where, Is = the current setting and I = the actual current and A, B and p are the curve type constants. U3-Very Inverse fb_InverseTimeCurveU3 TD (0.0963 + 3.88 Overcurrent coordination with fuses is a little tricky, especially for a remote backup fuse. They are Standard inverse (LV), Very inverse (LV, MV), extreme inverse (LV,MV, HV and EHV), and longtime standard inverse (VLV, LV,MV, HV and EHV).if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[250,250],'electrical4u_net-medrectangle-4','ezslot_3',109,'0','0'])};__ez_fad_position('div-gpt-ad-electrical4u_net-medrectangle-4-0'); For your easy understanding, the relay sensitivity works such as. 0000002563 00000 n curve : ANSI long-time inv. The more inverse the curve shape, the greater difference in trip times. This should be 0.50 - 15.00 for U.S. curves and 0.05 - 1.00 for IEC curves. S.I. in Figure 14.33 below. IEC Long-Time Inverse . IEC 60255-3/BS142 and IEEE C37.112-1996 standards and are often the basis of the electromechanical Inverse Definite Minimum Time is a type of calculation which provides the relay tripping time varies to the fault current, which means when the fault current low means we get high tripping time and the relay operates by certain time meanwhile while the fault current is high means, the relay operates at less time. 0000007740 00000 n If you would like to change your settings or withdraw consent at any time, the link to do so is in our privacy policy accessible from our home page.. Being such, fuses operate on a continuous-ampere rating. Operating equations and allowances are provided in the standard. The generic Inverse Definite Minimum Time (IDMT) time current curve calculator will allow you There are four curve types used in IEC 60255 which are: standard inverse, very inverse, extremely inverse and long time and IEC curves. Instantaneous Element allows for protection for faults. t = T ( 0.0963 + 3.88 M 2 1) Very inverse curve t = T ( 0.0352 + 5.67 M 2 1) Extremely inverse curve Where, t = Trip time (seconds) T = Time Dial setting (typically 0.5 to 15) M = Multiples of pickup current (e.g. Definite (instantaneous)-current protection. This again can be obtained from manufacturers data, commissioning, or timing therefore to check the relay model with manufacturers data to determine the curve type. 0000001873 00000 n This calculator allows you to choose both U.S. For any of the curves and a current multiplier (I/Is), a time is calculated, this time is the point at which the relay sends a signal. The maximum operating current is of primary importance for the setting. The effect of the current multiplier, the time multiplier setting, and definite time threshold can be shown So, in other words, Modern digital relays are programmable and thus curve shapes can easily be changed without the need for replacement. ':e^ ^ 4CDvLRCTR(x n&% 0m`l`` #c %`-%)2444 FL c4LI ]q(`4]p;QnIXA&C2s.U =\h\-D20-J4ILa) D}G6@r@ b> endobj 195 0 obj << /ProcSet [ /PDF /Text ] /Font << /F1 211 0 R /TT2 204 0 R /TT4 197 0 R /TT6 198 0 R /TT8 199 0 R /TT10 216 0 R /TT11 214 0 R /TT13 220 0 R /TT15 226 0 R >> /ExtGState << /GS1 234 0 R >> /ColorSpace << /Cs5 202 0 R >> >> endobj 196 0 obj << /Type /FontDescriptor /Ascent 891 /CapHeight 656 /Descent -216 /Flags 34 /FontBBox [ -568 -307 2028 1007 ] /FontName /TimesNewRoman /ItalicAngle 0 /StemV 94 /XHeight 0 >> endobj 197 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 122 /Widths [ 278 0 0 0 0 0 667 0 333 333 389 584 278 333 278 278 556 556 556 556 556 556 556 556 556 556 278 0 0 0 0 0 0 667 667 722 722 667 611 778 722 278 500 667 556 833 722 0 667 0 722 667 611 722 667 944 0 667 611 0 0 0 0 0 0 556 556 500 556 556 278 556 556 222 0 500 222 833 556 556 556 0 333 500 278 556 500 722 500 500 500 ] /Encoding /WinAnsiEncoding /BaseFont /Arial /FontDescriptor 201 0 R >> endobj 198 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 121 /Widths [ 250 0 0 0 0 0 778 0 333 333 0 0 250 333 250 0 500 500 500 500 500 500 0 0 500 500 278 0 0 564 0 0 0 722 667 667 722 611 556 0 0 333 0 722 0 889 722 722 556 0 667 556 611 722 722 0 0 0 0 0 0 0 0 0 0 444 500 444 500 444 333 500 500 278 0 500 278 778 500 500 500 500 333 389 278 500 500 722 500 500 ] /Encoding /WinAnsiEncoding /BaseFont /TimesNewRoman /FontDescriptor 196 0 R >> endobj 199 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 116 /Widths [ 250 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 500 0 444 556 444 0 0 0 278 0 0 278 833 556 500 556 0 444 389 333 ] /Encoding /WinAnsiEncoding /BaseFont /TimesNewRoman,Bold /FontDescriptor 200 0 R >> endobj 200 0 obj << /Type /FontDescriptor /Ascent 891 /CapHeight 0 /Descent -216 /Flags 34 /FontBBox [ -558 -307 2034 1026 ] /FontName /TimesNewRoman,Bold /ItalicAngle 0 /StemV 133 >> endobj 201 0 obj << /Type /FontDescriptor /Ascent 905 /CapHeight 718 /Descent -211 /Flags 32 /FontBBox [ -665 -325 2028 1037 ] /FontName /Arial /ItalicAngle 0 /StemV 94 /XHeight 515 >> endobj 202 0 obj [ /CalRGB << /WhitePoint [ 0.9505 1 1.089 ] /Gamma [ 2.22221 2.22221 2.22221 ] /Matrix [ 0.4124 0.2126 0.0193 0.3576 0.71519 0.1192 0.1805 0.0722 0.9505 ] >> ] endobj 203 0 obj << /Type /FontDescriptor /Ascent 935 /CapHeight 718 /Descent -211 /Flags 32 /FontBBox [ -182 -307 1000 1086 ] /FontName /ArialNarrow /ItalicAngle 0 /StemV 78 /XHeight 515 >> endobj 204 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 121 /Widths [ 228 0 0 0 0 0 0 0 273 273 319 479 0 273 228 0 456 456 456 456 456 456 456 456 456 456 0 0 0 479 0 0 0 547 547 592 592 547 501 638 592 228 410 547 456 683 592 0 547 0 592 547 501 0 547 774 0 547 501 0 0 0 0 0 0 456 456 410 456 456 228 456 456 182 0 0 182 683 456 456 0 0 273 410 228 456 410 0 410 410 ] /Encoding /WinAnsiEncoding /BaseFont /ArialNarrow /FontDescriptor 203 0 R >> endobj 205 0 obj 707 endobj 206 0 obj << /Filter /FlateDecode /Length 205 0 R >> stream Inverse Definite Minimum Time (IDMT) curves are used in both mechanical and electronic protection devices. Overcurrent (ANSI 67) Bus S G 1 2 Load 1 Load 2 Load 3 Load 4 F1 F2 F3 F4 Load 5 Increasing time 51 67 Time Overcurrent Relays U I ECE525 Lecture 11 . The minimum current at which the relay operates (pick up current) and time before trip are both adjustable. The thermal element acts as protection from overloading while the magnetic element is for protection from faults. Here the curve constant k and are given below and it will be varied based on the type of characteristics curves are used. 0000004699 00000 n LV and MV cables up to 33 kV with current capacity in accordance with BS 7671, ERA 69-30 and IEC 60502. Rev 01/13/99 RECLOSER CURVES Time Overcurrent Curve Equation Trip Time . We and our partners use data for Personalised ads and content, ad and content measurement, audience insights and product development. The ANSI standard curve constants are defined in the table below. The IDMT curve formula to calculate the trip time is: \(t(I)= TMS \displaystyle \left( \frac {k}{\displaystyle \left(\frac{I}{Is}\right)^\alpha-1}\right)\), \(t(I)= TD \displaystyle \left( \frac {A}{\displaystyle \left(\frac{I}{Is}\right)^p-1}+B\right)\). The following are some of the advantages and disadvantages of fuses: Learn More Transformer Tertiary Winding Basic Application, Learn More How Do Reclosers Work? 0000006012 00000 n Settings and Operation, IEC 60909 Short-circuit: Meshed vs Non-meshed, IEC 60909: Far from Generator Short-Circuit, Electro-mechanical or Solid-State Trip Device, Inverse Definite Minimum Time (IDMT) Overcurrent Relay, overcurrent protection and coordination study, Explore Overcurrent Coordination using ETAP Software, ETAP Star Coordination on Focus | Detailed Example, Detailed Example | ETAP Star Coordination On Focus PAC Basics, Development Of IDMT Relay Curves PAC Basics, Understanding Time Current Curves PAC Basics, Vector Group of Transformer Dyn1|Dyn11|Ynd1|Ynd11, kAIC Rating of Circuit Breakers | Calculation in Low Voltage System, minimum melting time the time when the metal strip starts to melt, and. The pickup current is adjustable and the application engineer can choose various settings from a wide range. 0000003057 00000 n 0000015168 00000 n Miniature Circuit Breakers (MCBs), Molded Case Circuit Breakers (MCCB), Air Circuit Breakers (ACB) fall into this category and are usually used in low voltage applications. specific curve produced for the input time multiplier but also a range of curves for time multiplier The time delay settings are adjustable and set following an overcurrent coordination study. 80. The standard defines an integral equation for microprocessor relays that ensures coordination not only in the case of constant current input but for any current condition of varying magnitude. Curve Equation: 2 Trip = TimeDial * [28.2/(I - 1) + 0.1217], where I is a multiple of Ir. However, some general comments can be made: o Use a comparable shape within a system segment for easier coordination. 2. TimeDial curve goes to flat response at 14xIr with a shorter time of TimeDial function or . Two settings are used to determine the time for a relay to initiate a trip: current setting (Is) and time multiplier setting (TMS). Short-Time Element the intermediate protection between overloading and faults. Curve - Select the Curve setting of the time overcurrent relay. Thermal Magnetic trip devices may be fixed or adjustable based on the ampere rating. Calculate Reset Pickup - Enter the pickup setting of the time overcurrent relay in primary amps. 4Sz^;t',8+GoF6HyN @)a|8U!d}qtE(j mgk=1>l"IAO-y$DE%yyAL'*.9hk-XU5zgAx2OLH;m~ Switching devices are another basic category for overcurrent protection devices. jUmfK: The function will reset as soon as the value falls below 95 % of the pick-up value. In mathematics, an elliptic curve is a smooth, projective, algebraic curve of genus one, on which there is a specified point O.An elliptic curve is defined over a field K and describes points in K 2, the Cartesian product of K with itself. 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To start our discussion on common overcurrent protection devices, let us review the basic considerations of a coordination study. Also, the IEEE section C37.112-1996 defines the IDMT timing in seconds by the below formula, t(s)= TD/7 ((A / (I(F)/Is)p 1) + B)if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[300,250],'electrical4u_net-banner-1','ezslot_7',126,'0','0'])};__ez_fad_position('div-gpt-ad-electrical4u_net-banner-1-0');if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[300,250],'electrical4u_net-banner-1','ezslot_8',126,'0','1'])};__ez_fad_position('div-gpt-ad-electrical4u_net-banner-1-0_1'); .banner-1-multi-126{border:none !important;display:block !important;float:none !important;line-height:0px;margin-bottom:7px !important;margin-left:auto !important;margin-right:auto !important;margin-top:7px !important;max-width:100% !important;min-height:250px;padding:0;text-align:center !important;}, T(s) = 0.143 * TSM * ((A / (I(F)/Is)p 1) + B), The IDMT is equal to 0.143 times of time setting multiplier TSM multiplication of sum of curve constant B and the ratio of curve constant A to the ratio of power of p of ratio of fault current IF to the relay current set value Is and minus 1. Page 47: Ansi / Ieee Inverse Time Protection Curves 4.3.1.3 ANSI / IEEE Inverse Time Protection Curves "IEEE (The Institute of Electrical and Electronics Engineers, Inc.) C37.112-2006: IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays - Description" standard describes the protection curves named as below. that the trip time is inversely proportional to the fault current. Purpose: The purpose of this standard is to provide an analytic (formula) representation of typical relay operating characteristic curve shapes of various inverse-time relays to facilitate representation by microprocessor-type relays and promote a degree of standardization in the inverse shape of a selected curve. Visit the Terms of Use and Privacy Policy for this site. While the over current pickups for both relays are the same, 2.10 Amps . and the definite time threshold is 20. Inverse Definite Minimum Time (IDMT), also referred to as Inverse Time Over Current (TOC), or Time Over Current (TOC), Extremely inverse (U4) 5.67 0352 5.67 2.00 . Thanks to the advent of the digital relay, its possible to have all of the advantages that come with the different types of relay elements packed into a single programmable unit. 0000008639 00000 n Cooper / ANSI Curve Association Chart I - Current t - Time. Related: Protective Relay Testing and Maintenance Overview, Powered by Discourse, best viewed with JavaScript enabled, Inverse Time Overcurrent Relays and Curves Explained, Protective Relay Testing and Maintenance Overview, Power System Protection: Overcurrent Protective Relays, IEEE C37.112-2018 - IEEE Standard for Inverse-Time Characteristics Equations for Overcurrent Relays. The Time Overcurrent Relay Operate Time Calculator will calculate the operate time In our previous discussion on overcurrent protection and coordination study, the following considerations were presented: Overcurrent protection devices can be categorized into three main types: Fuses are essentially made up of a metal wire or strip that melts when excessive currents flow through. This is depicted for five of the ST settings as a dashed horizontal lines. This may help in considering alternative settings. The trip time of an inverse curve is calculated from the following parameters: How long it takes for the relay to trip will vary depending on the curve slope, these curves can be used by engineers to coordinate with other protective devices upstream for selectivity and backup. 1 . Privacy Policy, Distance Between Conduit Supports Calculator, Time Overcurrent Relay Operate Time Calculator, Maximum Wire Ampacity for Current-Carrying Conductors in Raceway 30C Table, Maximum Wire Ampacity for Current-Carrying Conductors in Free Air 30C Table, Maximum Wire Ampacity for Current-Carrying Conductors in Raceway 40C Table, Maximum Wire Ampacity for Current-Carrying Conductors in Free Air 40C Table, Full-Load Current for Three-Phase AC Motors Table, Three-Phase AC Motor Wire Sizes and Circuit Protection Table, Distance Between Rigid Conduit Supports Table. Let us know how we can improve. b$AD` &~Dt@HLv A"Pq.10 @ ,X The primary device which can be another fuse should clear the fault before the minimum melting time of the remote backup fuse. There is no intentional time delay set. In electromechanical relays the curve is set by means of a dial which is why the setting is referred to as the time dial setting or TDS. Ideally, the same type should be used throughout the system. The Normal Inverse portion of the of the curve will be no faster than the Short Time Setting. Fault current (A). for a time overcurrent relay given the curve, time dial, pickup, and fault current. The Inverse Time Over Current (TOC/IDMT) relay trip time calculator calculates the protection trip time according to IEC 60255 and IEEE C37.112-1996 protection curves. : IEEE. Instantaneous relays operating time are usually less than 3 cycles. The relationship is as follows: The following is a description of the user entry and calculation field given in the image of the IDMT Positive and zero sequence impedance to IEC 60609. There are five different types of time overcurrent relay according to American standards. HT[o0~WG# 6:iSZ}Y@2w|I!k*MvYL)6 0-IA.8[)T2-!` b1z jXww \ZXO Te(yFnY!h* This means that the operating time decreases with increasing current magnitude. These are. means that the trip time is inversely proportional to the fault current. %PDF-1.2 % hn8_ Continue with Recommended Cookies. constant B which is added to the expression. Relay pickup current (A). You have entered an incorrect email address! 17555 Effective 03/97 from either AC or DC control power, and provides true RMS sensing of each phase and ground current. The "Phase time overcurrent" element can provide a specified time-delay operating characteristic versus the applied current or be used as a simple definite time element. W\W(DBqw#u; E9t)4%q Time Dial - Enter the Time Dial setting of the time overcurrent relay. check the relay settings and of course electronic relays use the same curves. %PDF-1.5 % We must also factor in the time B. iec 61952 iec 62155 estudio comparativo normas iec y ansi para cortocircuito. About | For 100/5 CT with P.S at 100%, TMS=0.1, using the standard inverse 3/10 curve, the SEPAM relay will be set based on the following: Is = 100A Type of curve =SIT/A If the setting mode is set as 10I/Is then T= XTMS = 2.97 X 0.1 = 0.297. 0000015783 00000 n Very inverse - CO-9 Extremely inverse - CO-11 The formula for co-8 inverse curve will be t (s) = TD (0.18 + (5.95 / (I/Is) 2 - 1)) if a standard inverse function is required then that is built into the specification of the relay. A. Definite-time relays operate with some intentional time delay and is adjustable along with the current pickup level. Enter your email address to subscribe and receive notifications of new posts by email. Relays detect and isolate faults indirectly. See table below. 0000005181 00000 n Settings and Operation. The three standard time charac-teristics are as follows: INVERSE TIME relays (see Table 1) are generally applied where the short-circuit current magnitude is Hence the name Inverse Definite Minimum Time. Electro-mechanical or Solid-State trip devices are more complex than Thermal Magnetic trip devices in that their trip characteristics can be divided into three sections. Extremely Inverse (EI) Type The 'EI' type IDMT relay curve operates at very fast at high short-circuit currents and very slow at low short-circuit currents. Low-voltage power fuses can withstand 110% of their rating under controlled conditions. Terms of Use | FxGHCqQsf74{c-[=%Z5R8)hywUM=]u9`4#uocvM` Hb```f``}AX,=Pv1+gd(>ee5E/DNFiA$w601eXs">]r? 2 . This type of IDMT curve is most suited for coordination with fuses. have to be declared if manufactured and tested in accordance with IEC 60255. tests but as a guide for the purposes of an arc flash calculation a generic allowance can be built in. Enter the information below to calculate the operate time for a time overcurrent relay. 1. In some relays a Time Dial Multiplier (TDM) is specified instead of a Time Dial (TD). 0000013909 00000 n Low-level overcurrent takes a long time interval to melt the fuse while large overcurrent levels tend to melt fuses very quickly. Extremely Inverse Speed (U.S., U4) Curve Type Device Type TCC Number PDF Excel; Average Tripping: S&C Overcurrent Control: TCC Number 691-9-U4: PDF: It provides an analytic representation of typical electromechanical relays operating characteristic curve shapes in order to facilitate coordination when using microprocessor-type relays. Calculate the tripping time for a relay set at 1000A pickup current and TMS setting of 1 (IEEE Very Inverse) with 10kA of fault current. These relays operate when the current exceeds the pick-up value and with an operating time that varies inversely the magnitude of the current. The relationship is as follows: TDM = TD 7 See the below table. We and our partners use cookies to Store and/or access information on a device. A few examples are: ANSI Extremely Inverse, Very Inverse, Inverse, Short Time Inverse; or IEEE Moderately Inverse, Very Inverse and Extremely Inverse. In Europe the shape of the overload relays tripping curves are defined by ANSI or IEEE standards. 0000002360 00000 n Learn More IEC 60909 Short-circuit: Meshed vs Non-meshed, Learn More IEC 60909: Far from Generator Short-Circuit. To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below. The Instantaneous, shown as a separate response, can be set to OFF. 0000001251 00000 n 4EplX=R^qC4QN#ZQM22 rlvo -ZW*wz0;Db\SxLggY:p8s%ZV0-euV.)&GnwibXp8mla(bb9j?@I1Da)>w~-- ( Py LDn60;?l )~?=PDBK]. SetR REAL Sets user-dened R parameter for inverse curve cal-culation (see Equation 2). Page 2 I.B. Kn?r|=d38xlY@Tikr|4Eu%HMzZ}PUP.p;Olj As mentioned in parameters, a Time Dial Multiplier (TDM) is sometimes specified by the relay manufacturer instead of a Time Dial (TD). IEC standard, very, extremely, and long-time inverse curves. 0000007234 00000 n IEEE Curve: American standard IDMT relay tripping Calculation: According to American standard the over current relay is classified based on the following, Definite minimum- CO-6. Fuses operate in a time-current band, between. Nearly any combination of instantaneous, definite-time, and inverse-time elements may be used. 0000004496 00000 n 0000015574 00000 n IEEE Time Dial (TD). These relays operate without an intentional time delay, so they are referred to as instantaneous units. The electrical current pickup set point Is in the relay. The calculator can be used wherever IDMT curves are used which are normally but not exclusively 120. Hb```f``g`c``Y |@Q5Wn7Ikq!s-8Bf;DlU!s"aV67c&JnM-.dc=Y3kQph(p4RR)b^]h$p$Lmog B = Timer coefficient for over-current trip.