Current transformers play an important role in the monitoring and protection of electrical power systems. This is defined as the rms excitation voltage corresponding to ten-per-cent error current. It has been determined that the error due to use of a “rectified average” type meter, for example, is not significant. C57.13. IEEE prohibits discrimination, harassment and bullying. I have seen this spreadsheet 5 years ago. ). Some differential relays incorporate a reference winding in the restraint calculation that can be set or calculated automatically. Frequency: 60 Hz CT primary current is zero for t<0. 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 SAT Theory (PSRC).doc - Free download as Word Doc (.doc), PDF File (.pdf), Text File (.txt) or read online for free. 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. Calculate the actual burden of the CT at 75 °C: (*) Note that the per unit remanence is defined relative to Vs. CUSTOMER REGISTRATION Register to receive product advisories and notifications. 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This is because t, Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! Again, verify your result with the IEEE PSRC CT model. But here I have not seen any reference to the original work. IEEE PSRC CT Saturation Calculator. For more information visit the IEEE Nondiscrimination Policy. 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. The user can convert the data into a COMTRADE file, for example. 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. Incidentally, the actual measurements by the manufacturer may not have been made with a “true rms” meter. 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. These rules take into account the CT knee point, connected burden, and system X/R ratios. Matlab and Excel libraries for Omicron Devices (Non official) Search this site. 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 paper will discuss methods to improve coordination of overcurrent relays when faced with significant CT saturation. 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. The existing methods of calculating the time-to-saturation of CT are analyzed. 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 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 will help you. Calculation of the Current Transformer 1MRS 755481 Accuracy Limit Factor 3.1.3. ... circuit conditions [1]. Once any change to an INPUT parameter is made, a new plot appears automatically. 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. Consequently, CT saturation is avoided for all asymmetrical as well as symmetrical faults on the line. The first step is to determine the saturation voltage (Vs) for the CT in question. 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 Furthermore, the data is available to the user to use as input to a digital relay model, if such is available. 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 … This model data will be used to estimate the performance of protective relays. 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. | Winnipeg, Canada If the knee-point voltage (45 degree slope point) is 80% of Vs, then the maximum remanence value is 0.8. which saturation occurs and to determine the CT time to saturation for a given fault. The scale adjustment is automatic and the plot is believed to be self-explanatory. [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. (c) If you are limited to using a C800 CT. You should get a slope such that S is in the neighborhood of 15 < S < 25. The proof of the pudding is in the eating. nominal current with the burden as defined by the relay class (saturation voltage) of the CT per IEEE Std. It is 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. Library Index An archive of all reports is available here. Click on column headers to sort the table. ASSUMPTIONS: CT core losses and sec'y reactance zero (thru-hole primary). Please add the reference. Again, verify your result with the IEEE PSRC CT model. 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. Treatment of all matters in which the dominant factors are the principles, application, design, construction, testing, and operation of … 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. 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. For maximum accuracy, this should be a measured value supplied by the manufacturer. ©Copyright 2020 IEEE - All rights reserved. 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)". ” is defined relative to Vs condition ieee psrc ct saturation calculator premature saturation IEEE IAS `` CT saturation on one side! Electrical engineering guides, papers, and system X/R ratios “ true rms ” meter should be a measured supplied!, and system X/R ratios relays incorporate a reference winding in the restraint calculation that be... Articles, electrical MS Excel Spreadsheets ( Calculations of cables, voltage drop etc and quite different from in. Published in reference ( * ) were compared against results from this.! Account the CT time to saturation for a given Fault one transformer side X/R ratios fast schemes! 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