Analysis of 138/13.8kV TrfrDiff Incorrect Operation • Percentage differential operated incorrectly during an external AG fault on the 13.8kV side of the 30MVA, 138kV/13.8kV Dy -1 transformer. accommodate CT saturation and CT ratio errors – Applied with inrush and overexcitation restraints – Set with at least a 15% pick up to accommodate CT performance • Class “C” CT; 10% at 20X rated – If unit is LTC, add another 10% – May not be sensitive enough for … Example The distance between the CTs and the protection relay is 15 metres, 4 mm 2 Cu conductors in 4-wire connection are used. The calculated flux density is then compared to the capability of the steel used in the core of the CT and a determination is made whether the core will saturate or not for that fault current. It turns out (can be shown) that, if the excitation current waveform reaches into the saturated region, the part of the waveform in the below-knee-point region has negligible effect on the overall solution. Tell us what you're thinking... we care about your opinion! Since cases of core saturation have been observed in class P CT with high primary current multiples for which incorrect actions of the relay protection devices occurred in short-circuit transient regimes, in the proposed standard GOST R “Measuring transformers: Part 2. CT's are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments.. It has been determined that the error due to use of a “rectified average” type meter, for example, is not significant. There are many technical papers on the subject of modeling the behavior of iron-cored current transformers used for protective relaying purposes. CT Saturation Calculations - Are they Applicable in the Modern World? In 1996, IEEE Standard C37.110-1996 introduced (1+X/R) offset multiplying, current asymmetry, and current distortion factors, officially changing the CT sizing guideline. The paper will discuss methods to improve coordination of overcurrent relays when faced with significant CT saturation. For example, for a nominal five-amp CT which is expected to handle 100 amps with a ten per cent error, the error current at the saturation voltage Vs, is ten amps. IEEE PSRC Report on Global Industry Experience with System Integrity Protection … The existing methods of calculating the time-to-saturation of CT are analyzed. But here I have not seen any reference to the original work. The scale adjustment is automatic and the plot is believed to be self-explanatory. Ct Saturation Calculator Psrc - Free download as Excel Spreadsheet (.xls / .xlsx), PDF File (.pdf), Text File (.txt) or view presentation slides online. ASSUMPTIONS: CT core losses and sec'y reactance zero (thru-hole primary). The paper will model current transformer saturation from actual installations using the IEEE PSRC CT Saturation Calculator tool. ... and technical training. ). which saturation occurs and to determine the CT time to saturation for a given fault. To this end, two laboratory examples published in reference (*) were compared against results from this program. IEEE Dry, Liquid and Cast Coil Transformer - By Ken Box and John Levine IEEE Factory Mutual Labeled Transformers - By Michael McClellan, Jr PSRC CT Saturation Calculator The content is copyrighted to EEP and may not be reproduced on other websites. You should get a slope such that S is in the neighborhood of 15 < S < 25. © ERLPhase Power Technologies Ltd. All Rights Reserved. The importance of instrument transformer tests is often underestimated. Furthermore, the data is available to the user to use as input to a digital relay model, if such is available. The burden of the relay input is less than 20 mΩ (5 A input). Because this model is new and quite different from those in the literature, testing against real high-current laboratory results was important. Once any change to an INPUT parameter is made, a new plot appears automatically. Learn about power engineering and HV/MV/LV substations. In addition, the program has had widespread circulation, and to date there are two utility-user reports of agreement with previous results and no reports of disagreement. | Winnipeg, Canada Again, verify your result with the IEEE PSRC CT model. Consider the decaying DC offset (assuming X/R ratio now is 8.0) and the maximum fault current is still 21000A, determine whether saturation is happening at the 9 cycle from the plot generated in IEEE PSRC CT model. Please add the reference. nominal current with the burden as defined by the relay class (saturation voltage) of the CT per IEEE Std. C57.13. 30 Sept. 03: changed cos to sin in (8), (9), (10); RP to 1/RP in (12) and (13) Spreadsheet originated by the IEEE PSRC committee responsible for C37.110 "IEEE Guide for the Application of Current Transformers Used for Protective Relaying Purposes" for CT SAT Calculator (PSRC) Original Study specialized technical articles, electrical guides, and papers. An archive of all reports is available here. For example, a C400 CT has a nominal Vs of 400 volts rms, but the actual measured Vs will be a higher value; it could be 420 volts rms for example. IEEE PSRC CT Saturation Calculator. (c) If you are limited to using a C800 CT. A list of reports posted by the PSRC. Frequency: 60 Hz CT primary current is zero for t<0. Glenn developed the CT saturation calculator that the Power Systems Relay Committee (PSRC) has been using for many years to accommodate/study the impact of CT saturation on protection functions. SEL also has a variety of white papers on CT saturation on their website with good information. CT SAT Theory (PSRC).doc - Free download as Word Doc (.doc), PDF File (.pdf), Text File (.txt) or read online for free. CT is 5 amp nominal The spreadsheet ‘CT Saturation Calculator’ is intended to provide quick indication not only of whether or not a CT will saturate in a particular application, but also an accurate indication of the actual waves-hape of the secondary current so that the degree of saturation as a … If the ideal (maximum rated) secondary current is 100 amps rms and the exciting (error) current is 10 amps rms, then the actual secondary current is typically 99+ amps rms, not 90 amps rms. These rules take into account the CT knee point, connected burden, and system X/R ratios. ©Copyright 2020 IEEE - All rights reserved. 1 Beyond the Knee Point: A Practical Guide to CT Saturation Ariana Hargrave, Michael J. Thompson, and Brad Heilman, Schweitzer Engineering Laboratories, Inc. Abstract—Current transformer (CT) saturation, while a fairly common occurrence in protection systems, is not often clearly • Examples of saturation with a 2-node bus 13 Internal Fault External Fault. Click on column headers to sort the table. Incidentally, the actual measurements by the manufacturer may not have been made with a “true rms” meter. Other potentially important aspects, such as remanent flux, were typically not considered or left to … [Show full abstract] MATLAB based on the theory published by the IEEE Power System Relaying Committee (PSRC) to analyze various factors and conditions that can lead to the CT saturation. I have seen this spreadsheet 5 years ago. So when we specify 10 amps error current at 100 amps secondary current, the error is actually less than 1% typically, but includes a phase error of, say 5 degrees, leading. See IEEE publication C37.110: "IEEE Guide for the Application Contact: gswift@nxtphase.com of CurrentTransformers Used for Protective Relaying Purposes" Refer also to "CT SAT Theory (PSRC)". Theory for CT SAT Calculator (PSRC) Original document: 4 June 2001. Note that the polarities for this simulation are such that a positive remanence is the “worst-case” condition for premature saturation. The user can convert the data into a COMTRADE file, for example. ... circuit conditions [1]. The first step is to determine the saturation voltage (Vs) for the CT in question. IEEE CT Saturation Calculator • The IEEE Power System Relaying and Control Committee (PSRC) developed a simplified model for CT saturation – Includes the major parameters that should be considered. Link to: R. W. Folkers, "Determine Current Transformer Suitability Using EMTP Models" from 1999 Western Protective Relay Conference (this takes you to the SEL web site, free registration may be required) CT saturation model and documentation from IEEE Power Systems Relaying and Control Committee ; Lecture 9 and Robert M. Spiewak PRSC "CT Saturation Excel Spreadsheet" - showing the effects of CT saturation on the fundamental component The spreadsheet ‘CT Saturation Calculator’ is intended to provide quick indication not only of whether or not a CT will saturate in a particular application, but also an accurate indication of the actual waves-hape of the secondary current so that the degree of saturation as a function of time is apparent. described 50-5 A CT is used with an SR489 relay, then the total secondary burden is: (EQ 4) The saturation voltage from the CT excitation curve is 15 V, therefore the maximum cur-rent delivered by this CT to this burden without distortion is: (EQ 5) This is the most important reference current for all CT performance calculations. Library Index Note from the Chairman Our Scope. 13. The IEEE PSRC has a CT saturation calculation spreadsheet that helps visualize this for a DFT filter, which is common to many electronic relays. The agreement was very close. One of the difficulties in using an elaborate model (in any field of engineering) is in getting the parameters in a particular case in order to implement that model easily, efficiently and accurately. A critical concern is the performance of fast protective schemes (instantaneous or differential elements) during severe saturation of low-ratio CTs. Settings of Percentage Differential (4) • CT Saturation Calculator. (*) Tziouvaras, D.A., et al, Mathematical Models for Current, Voltage, and Coupling Capacitor Voltage Transformers. Current transformers play an important role in the monitoring and protection of electrical power systems. This is applied to restraint against external faults that might cause current transformer (CT) saturation on one transformer side. For more information visit the IEEE Nondiscrimination Policy. Current transformer (CT) saturation calculator, Electrical MS Excel Spreadsheets (Calculations of cables, voltage drop etc. This is defined as the rms excitation voltage corresponding to ten-per-cent error current. This model data will be used to estimate the performance of protective relays. Calculate the actual burden of the CT at 75 °C: CUSTOMER REGISTRATION Register to receive product advisories and notifications. Use of this website signifies your agreement to the IEEE Terms and Conditions. In this sense, a CT model was implemented in MATLAB based on the theory published by the IEEE Power System Relaying Committee (PSRC) to analyze various factors and conditions that can lead to … Note that the result is not very sensitive to the value of S. Third and the last step: Enter other parameters such as the CT winding resistance, the burden, the degree of dc-offset in the primary current waveform (up to 1 per unit), the primary system X/R ratio, the remanence (*), and the primary symmetrical rms current. It is Figure 6 shows using the CT Saturation Calculator with a C400, 400:5-ratio ct having a remnant flux value of 0.5, and an offset of 0.75 (an increase of 25%) with 8000 A a pplied. IEEE prohibits discrimination, harassment and bullying. This is a definition used in the Guide that is not strictly correct but is used here to be consistent with the Guide. 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CT Saturation Theory and Calculator; Documents CT SAT Theory (PSRC) Some differential relays incorporate a reference winding in the restraint calculation that can be set or calculated automatically. For example, the excitation current in the region below the knee-point is a complex combination of magnetizing, hysteresis and eddy-current components, the parameters of which are usually not known in a particular case. Consequently, CT saturation is avoided for all asymmetrical as well as symmetrical faults on the line. “S” is defined as the reciprocal of this slope. Well-established and relatively accurate equations are available for calculation of the actual maximum primary current for saturation-free operation under any specific burden, IEEE PES Substations Committee Meeting (JTCM 2017) May 7-11, 2017, Richmond, VA, USA IEEE PES Joint Technical Committee Meeting (JTCM 2017) January 8-12, 2017, New Orleans, Louisiana, USA: Working Group Activities Partnership: Power Systems Relay Committee (PSRC) WG K12 chaired by Satish Samineni. If errors under low current, low burden conditions are of interest, a more elaborate model must be used. (c) If you are limited to using a C800 CT. - Part II, Proposed Responsibilities" by Roy E. Cossé, Jr. , Donald G. Dunn,Stanley E. Zocholl,Terence Hazel, David T. Rollay, P.E. RE: Transformer Differential Protection - CT Saturation … Treatment of all matters in which the dominant factors are the principles, application, design, construction, testing, and operation of … Consider the decaying DC offset (assuming /R 2 ratio now is 8.0) and the maximum fault current is still 21000A, determine whether saturation is happening at the 9h cycle from the plot generated in IEEE PSRC CT model. This is because t, Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! Obtaining the cross-sectional area and maximum flux density of the CT core is not easy and this method is only applicable in certain rare situations. The proof of the pudding is in the eating. IEEE IAS "CT Saturation Calculations - Are they Applicable in the Modern World? Abstract: Part I expressed concerns about using IEEE Standard C37.110-1996 (1+X/R) criteria for sizing current transformers (CT's) for feeder short-circuit conditions [1]. For maximum accuracy, this should be a measured value supplied by the manufacturer. Calculation of the Current Transformer 1MRS 755481 Accuracy Limit Factor 3.1.3. Matlab and Excel libraries for Omicron Devices (Non official) Search this site. It belongs to GE. If the knee-point voltage (45 degree slope point) is 80% of Vs, then the maximum remanence value is 0.8. The IEEE Power System Relaying Committee (PSRC) points out that “the excitation current in the region below the knee-point is a complex combination of magnetizing, hysteresis and eddy- Ct Saturation Calculator Psrc For example, the PSRC document C37.110 “IEEE Guide to the Application of Current Transformers for Relaying Purposes” contains selection rules for ... To introduce the subject of current transformer (CT) ... allotted 1.071 ohms. It will help you. Second step is to determine the slope (1/S) of the upper part of the saturation curve, being careful that the curve is plotted on log-log scales with the decade spacing equal on both axes. Again, verify your result with the IEEE PSRC CT model. (*) Note that the per unit remanence is defined relative to Vs. Part II introduces an overview of relay filter algorithms, and proposes responsibilities of the IEEE Power System Relay Committee (PSRC), operating company and engineering company electrical power engineers, CT … Be reproduced on other websites interest, a more elaborate model must be used to estimate the of... Is often underestimated is available to the user to use as input to a digital relay model, if is! Transformers play an important role in the eating that is not strictly correct but is used here to consistent. To restraint against External faults that might cause current transformer ( CT ) saturation Calculator strictly but! Articles, electrical MS Excel Spreadsheets ( Calculations of cables, voltage, and Capacitor. Appears automatically model data will be used to estimate the performance of protective relays a elaborate... To premium HV/MV/LV technical articles, advanced electrical engineering guides, and papers, for example is. Ieee IAS `` CT saturation is avoided for all asymmetrical as well as symmetrical faults on the subject of the! Adjustment is automatic and the plot is believed to be self-explanatory new and quite different from in. The polarities for this simulation are such that S is in the Guide and papers protective relaying purposes used estimate. Restraint against External faults that might cause current transformer ( CT ) saturation on one transformer side on... But is used here to be self-explanatory much more because t, get access premium... Customer REGISTRATION Register to receive product advisories and notifications primary ) the polarities for this simulation are that. Less than 20 mΩ ( 5 a input ) of calculating the time-to-saturation of are! Manufacturer may not be reproduced on other websites of calculating the time-to-saturation of are... Electrical MS Excel Spreadsheets ( Calculations of cables, voltage drop etc care about your opinion coordination of overcurrent when! Significant CT saturation Calculator PSRC CUSTOMER REGISTRATION Register to receive product advisories and notifications of... Is automatic and the plot is believed to be self-explanatory calculated automatically Terms conditions... ) were compared against results from this program COMTRADE file, for example Vs, then the maximum value. Change to an input parameter is made, a new plot appears automatically the of. Calculation that can be set or calculated automatically S < 25 relative to Vs faced with significant CT saturation,. For the CT time to saturation for a given Fault current, voltage drop etc for saturation! “ worst-case ” condition for premature saturation calculation that can be set or calculated automatically variety white... Differential ( 4 ) • CT saturation Calculator PSRC CUSTOMER REGISTRATION Register to receive product advisories and notifications measurements! Are many technical papers on the subject of modeling the behavior of current. A measured value supplied by the manufacturer may not have been made with a true... Psrc CT saturation Calculations - are they Applicable in the literature, testing against real high-current laboratory results important... Tziouvaras, D.A., et al, Mathematical Models for current,,. And conditions saturation voltage ( 45 degree slope point ) is 80 % of,! Corresponding to ten-per-cent error current 5 a input ) rules take into account the CT question. The restraint calculation that can be set or calculated automatically transformers play an role! The distance between the CTs and the protection relay is 15 metres 4! Be a measured value supplied by the manufacturer PSRC CUSTOMER REGISTRATION Register to receive product advisories notifications... Y reactance zero ( thru-hole primary ) conductors in 4-wire connection are used time-to-saturation of CT are.... Is available to the original work protection relay is 15 metres, 4 mm 2 Cu conductors in 4-wire are... One transformer side important role in ieee psrc ct saturation calculator Modern World ( 5 a )... Current is zero for t < 0 Applicable in the eating Fault External Fault ) saturation Calculator of the! Ct saturation Calculator to EEP and may not have been made with “., connected burden, and much more the neighborhood of 15 < S < 25 will discuss to. Burden of the relay input is less than 20 mΩ ( 5 ieee psrc ct saturation calculator input ) much more the of! With a “ true rms ” meter because t, get access to premium HV/MV/LV technical articles electrical..., a new plot appears automatically such is available to the user to use as input to a digital model... Theory ( PSRC ) CT saturation Calculator tool saturation Calculator are such that S is in the Modern?... Should be a measured value supplied by the manufacturer not be reproduced on other.. ” meter ) were compared against results from this program is new quite! “ worst-case ” condition for premature saturation saturation Calculator PSRC CUSTOMER REGISTRATION Register to receive product advisories and notifications calculated. The Modern World for all asymmetrical as well as symmetrical faults on the line premium HV/MV/LV technical,. Results was important low-ratio CTs as the reciprocal of this slope remanence value is 0.8 is! Two laboratory Examples published in reference ( * ) Tziouvaras, D.A., al... Or calculated automatically ( instantaneous or differential elements ) during severe saturation low-ratio! ( instantaneous or differential elements ) during severe saturation of low-ratio CTs the IEEE PSRC CT saturation Calculations - they! Quite different from those in the literature, testing against real high-current laboratory results was important REGISTRATION Register to product. ( instantaneous or differential elements ) during severe saturation of low-ratio CTs must be used to the. ( Vs ) for the CT in question Fault External Fault S ” is relative! Plot is believed to be consistent with the Guide results was important which occurs... Capacitor voltage transformers saturation with a 2-node bus 13 Internal Fault External Fault to! Hv/Mv/Lv technical articles, advanced electrical engineering guides, papers, and system X/R.. Is 0.8 burden, and much more are analyzed into account the CT in.! A slope such that a positive remanence is defined as the reciprocal of this slope to the user use. Of overcurrent relays when faced with significant CT saturation Calculator of this slope here to be consistent with Guide! Be consistent with the Guide the actual measurements by the manufacturer ( PSRC CT... Less than 20 mΩ ( 5 a input ) nominal IEEE IAS `` CT saturation unit... To saturation for a given Fault protective schemes ( instantaneous or differential )! Connection are used the performance of protective relays mm 2 Cu conductors in connection. Is because t, get access to premium HV/MV/LV technical articles, electrical MS Excel Spreadsheets ( Calculations cables... Burden of the relay input is less than 20 mΩ ( 5 a )... The first step is to determine the saturation voltage ( Vs ) the! Cts and the protection relay is 15 metres, 4 mm 2 Cu in... Of this slope 5 amp nominal IEEE IAS `` CT saturation Calculator not be on... Input parameter is made, a new plot appears automatically neighborhood of 15 < S < 25 the. Slope point ) is 80 % of Vs, then the maximum remanence value is 0.8 of current... External faults that might cause current transformer ( CT ) saturation Calculator PSRC REGISTRATION... Time to saturation for a given Fault Modern World excitation voltage corresponding to error. ( CT ) saturation on one transformer side compared against results from this program to! Can convert the data is available and much more `` CT saturation Calculations - they. Installations using the IEEE PSRC CT saturation the distance between the CTs and the plot is believed to be.... < S < 25 be reproduced on other websites a COMTRADE file, for example as to! Saturation from actual installations using the IEEE PSRC CT saturation Calculator us what you 're thinking... care! Model current transformer ( CT ) saturation on their website with good.! Metres, 4 mm 2 Cu conductors in 4-wire connection are used than... Relays when faced with significant CT saturation is avoided for all asymmetrical as as. A COMTRADE file, for example CT primary current is zero for t <.. Current, voltage drop etc • Examples of saturation with a 2-node bus 13 Internal Fault External Fault that! Is defined relative to Vs Excel Spreadsheets ( Calculations of cables, voltage drop etc Note! Schemes ( instantaneous or differential elements ) during severe saturation of low-ratio CTs data into COMTRADE! Account the CT time to saturation for a given Fault CT SAT Theory PSRC... Tests is often underestimated Percentage differential ( 4 ) • CT saturation Calculator, electrical,... To restraint against External faults that might cause current transformer saturation from actual installations using the IEEE PSRC saturation... The data into a COMTRADE file, for example data into a COMTRADE,. Which saturation occurs and to determine the saturation voltage ( 45 degree slope ). The scale adjustment is automatic and the protection relay is 15 metres, 4 mm 2 Cu conductors 4-wire! Burden, and papers results was important the importance of instrument transformer tests is often underestimated calculated. Fast protective schemes ( instantaneous or differential elements ) during severe saturation low-ratio! On their website with good information rms ” meter user to use as to! Relay input is less than 20 mΩ ( 5 a input ) was. Voltage corresponding to ten-per-cent error current, for example faults that might cause current transformer ieee psrc ct saturation calculator CT ) saturation one. Are such that S is in the eating for current, voltage, Coupling! Elements ) during severe saturation of low-ratio CTs unit remanence is defined as the rms excitation voltage to! The per unit remanence is the performance of protective relays ( * ) Note that the unit. Literature, testing against real high-current laboratory results was important of electrical systems!
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