Ct knee point voltage calculation pdf files

The saturation voltage vsat is graphically found by locating the intersection of the straight portions of the excitation curve on loglog axes 3. C ratio error can be determined by calculation from the. Reflected to the primary the auxiliary ct secondary burden is 4. Knee point voltage of current transformer ps class. The sinusoidal voltage of rated frequency applied to the secondary terminals of current transformer, with other winding being open circuited, which when increased by 10% cause the exiting current to increase 50%. The knee point determines the saturation voltage of a. Voltage output to 250 v is connected to the secondary terminals of the current transformer between the common of the main current output and the active tap of out1 so as to allow the measurement. A handy formula for resistance versus awg american wire gauge number is. Ct, the knee point voltage vk is defined as the point on this. How cts work in its simplest form, a ct consists of two sets of wire windings around an iron core, as shown in 1. Pdf the impact of currenttransformer saturation on. In order to properly test the kneepoint the connections must be as follows. This is the reason, in definition it is said that knee point voltage of a current transformer is defined as the voltage at which 10 % increase in voltage of ct secondary results in 50 % increase in secondary current.

The knee point voltage of the current transformers should be at least twice the relay setting. To measure this first demagnetise the ct and apply voltage gradually from secondary keeping primary winding open circuited. Knee point voltage of current transformer electrical. This means that an increase in 50% current will lead to just an increase in 10% voltage. Ct knee point voltage calculation transformer volt. It then explainhow s this core activity corresponds to the ct equivalent circuit, ansi voltage ratings, and the familiar ct excitation graph. Exciting reactance calculated from the excitation curve in figure 3. Stabilizing resistor 280 kneepoint test with pte100c.

Cahiers techniques is a collection of documents intended for engineers. Ct knee point voltage can be calculated using formula. The ct lead resistances can be calculated from the layout drawings. R is the total resistance of the secondary of the ct. Demagnetization, ct ratio, knee point, saturation, polarity and phase deviation test displays multiple instantaneous saturation curves with knee point integrated 1 kv dc insulation test system color daylight viewable graphical display. Please help me how to calculate the same its very argent. Knee point voltage of current transformer this is the significance of saturation level of a ct core mainly used for protection purposes. K same as c class, except the kneepoint must be greater.