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Transformer design calculation excel11/10/2022 ![]() If errors under low current, low burden conditions are of interest, a more elaborate model must be used. ![]() This simplifies the solution greatly, with little effect on accuracy. 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.įor 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.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. There are many technical papers on the subject of modeling the behavior of iron-cored current transformers used for protective relaying purposes. The user can convert the data into a COMTRADE file, for example. 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 function of time is apparent. The curve of applied rms terminal voltage vs rms secondary current is approximately the secondary excitation curve. The current that flows in to the CT needs to be measured. ![]() The reasonably accurate secondary excitation curve for a given CT can be obtained by open circuiting the primary and applying AC voltage of appropriate frequency to the secondary. This method is not discussed further.Įxcitation curve represents a curve of CT secondary rms voltage plotted against rms current with the primary open circuited. ![]() 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 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. The formula method uses the fundamental transformer equation to calculate the effective flux density for a particular value of fault current. Read Time:4 Minute, 57 Second Current transformer (CT) saturation calculatorĬurrent Transformer Performance CalculationĬurrent Transformer (CT) performance can be estimated using one of the following methods:Ĭurrent transformer (CT) saturation calculator ![]()
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