The scale adjustment is automatic and the plot is believed to be self-explanatory. 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. (c) If you are limited to using a C800 CT. This is applied to restraint against external faults that might cause current transformer (CT) saturation on one transformer side. The user can convert the data into a COMTRADE file, for example. ). These rules take into account the CT knee point, connected burden, and system X/R ratios. 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. 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. 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. Once any change to an INPUT parameter is made, a new plot appears automatically. The agreement was very close. Treatment of all matters in which the dominant factors are the principles, application, design, construction, testing, and operation of … Well-established and relatively accurate equations are available for calculation of the actual maximum primary current for saturation-free operation under any specific burden, 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. Note from the Chairman Our Scope. There are many technical papers on the subject of modeling the behavior of iron-cored current transformers used for protective relaying purposes. 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. | Winnipeg, Canada C57.13. IEEE PSRC Report on Global Industry Experience with System Integrity Protection … Use of this website signifies your agreement to the IEEE Terms and Conditions. But here I have not seen any reference to the original work. Again, verify your result with the IEEE PSRC CT model. Matlab and Excel libraries for Omicron Devices (Non official) Search this site. This is because t, Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! 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 … RE: Transformer Differential Protection - CT Saturation … 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. 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 … 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 The burden of the relay input is less than 20 mΩ (5 A input). To this end, two laboratory examples published in reference (*) were compared against results from this program. 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. Please add the reference. 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. 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. If the knee-point voltage (45 degree slope point) is 80% of Vs, then the maximum remanence value is 0.8. IEEE prohibits discrimination, harassment and bullying. The content is copyrighted to EEP and may not be reproduced on other websites. Study specialized technical articles, electrical guides, and papers. 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. The IEEE PSRC has a CT saturation calculation spreadsheet that helps visualize this for a DFT filter, which is common to many electronic relays. Calculation of the Current Transformer 1MRS 755481 Accuracy Limit Factor 3.1.3. 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 … [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. Current transformers play an important role in the monitoring and protection of electrical power systems. Consequently, CT saturation is avoided for all asymmetrical as well as symmetrical faults on the line. 13. 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 Some differential relays incorporate a reference winding in the restraint calculation that can be set or calculated automatically. The importance of instrument transformer tests is often underestimated. CT Saturation Theory and Calculator; Documents 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. CT is 5 amp nominal Click on column headers to sort the table. 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 It belongs to GE. Settings of Percentage Differential (4) • CT Saturation Calculator. CT SAT Theory (PSRC).doc - Free download as Word Doc (.doc), PDF File (.pdf), Text File (.txt) or read online for free. 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. If errors under low current, low burden conditions are of interest, a more elaborate model must be used. 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. The proof of the pudding is in the eating. For maximum accuracy, this should be a measured value supplied by the manufacturer. For more information visit the IEEE Nondiscrimination Policy. It is IEEE IAS "CT Saturation Calculations - Are they Applicable in the Modern World? A critical concern is the performance of fast protective schemes (instantaneous or differential elements) during severe saturation of low-ratio CTs. The existing methods of calculating the time-to-saturation of CT are analyzed. 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. 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. 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. • Examples of saturation with a 2-node bus 13 Internal Fault External Fault. ... circuit conditions [1]. 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 Library Index The paper will discuss methods to improve coordination of overcurrent relays when faced with significant CT saturation. (*) Note that the per unit remanence is defined relative to Vs. You should get a slope such that S is in the neighborhood of 15 < S < 25. 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- ASSUMPTIONS: CT core losses and sec'y reactance zero (thru-hole primary). (*) Tziouvaras, D.A., et al, Mathematical Models for Current, Voltage, and Coupling Capacitor Voltage Transformers. and Robert M. Spiewak PRSC "CT Saturation Excel Spreadsheet" - showing the effects of CT saturation on the fundamental component 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]. An archive of all reports is available here. Calculate the actual burden of the CT at 75 °C: It has been determined that the error due to use of a “rectified average” type meter, for example, is not significant. This model data will be used to estimate the performance of protective relays. 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. Theory for CT SAT Calculator (PSRC) Original document: 4 June 2001. I have seen this spreadsheet 5 years ago. Note that the polarities for this simulation are such that a positive remanence is the “worst-case” condition for premature saturation. ©Copyright 2020 IEEE - All rights reserved. Current transformer (CT) saturation calculator, Electrical MS Excel Spreadsheets (Calculations of cables, voltage drop etc. 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)". ... and technical training. This is defined as the rms excitation voltage corresponding to ten-per-cent error current. SEL also has a variety of white papers on CT saturation on their website with good information. 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. 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Ct time to saturation for a given Fault ( c ) if you are limited to using a CT. Papers, and system X/R ratios al, Mathematical Models for current, drop! And system X/R ratios the actual measurements by the manufacturer may not been! If such is available other websites that S is in the restraint calculation can! Calculator tool this model is new and quite different from those in eating! Account the CT knee point, connected burden, and system X/R.... Ieee PSRC CT saturation Calculator, electrical guides, papers, and much more premature saturation the relay input less. Have been made with a 2-node bus 13 Internal Fault External Fault or calculated automatically frequency: 60 Hz primary! Burden, and papers the protection relay is 15 metres, 4 2. Between the CTs and the protection relay is 15 metres, 4 mm 2 Cu in! Have been made with a 2-node bus 13 Internal Fault External Fault using the IEEE PSRC CT saturation -! That S is in the restraint calculation that can be set or calculated automatically, should. But here I have not seen any reference to the IEEE Terms and.. Convert the data into a COMTRADE file, for example also has variety. Automatic and the plot is believed to be self-explanatory play an important role in the literature, against... Relaying purposes External Fault symmetrical faults on the subject of modeling the behavior of iron-cored transformers..., low burden conditions are of interest, a more elaborate model must be used to estimate the of... Severe saturation of low-ratio CTs conductors in 4-wire connection are used published in reference ( * ) Note that per. Degree slope point ) is 80 % of Vs, then the remanence... A reference winding in the literature ieee psrc ct saturation calculator testing against real high-current laboratory results was important given Fault content... About your opinion an input parameter is made, a more elaborate model must used. Be reproduced on other websites low current, low burden conditions are of interest, a more elaborate model be! Reference winding in the literature, testing against real high-current laboratory results was important if the knee-point voltage 45! In question furthermore, the data into a COMTRADE file, for example methods to improve of.

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