THERMAL CONSIDERATIONS The losses in the windings and the core cause temperature rises in the materials. This is another important area in which the temperatures must be limited to the long-term capability of the insulating materials. Refined paper is still used as the primary solid insulation in power transformers. Highly refined mineral oil is still […]
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The term load losses represents the losses in the transformer that result from the flow of load current in the win dings. Load losses are composed of the following elements. Resistance losses as the current flows through the resistance of the conductors and leads. Eddy losses caused by the leakage field. These are a function
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For voltages higher than about 300 to 500 kV, the cascading of transformers is a big advantage, as the weight of a whole testing set can be subdivided into single units and therefore transport and erection becomes easier. Also, with this, the transformer cost for a given voltage may be reduced, since cascaded units need
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For voltages higher than 400 KV, it is desired to cascade two or more transformers depending upon the voltage requirements. With this, the weight of the whole unit is subdivided into single units and, therefore, transport and erection becomes easier. Also, with this, the transformer cost for a given voltage may be reduced, since cascaded
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Transformer magnetic material characteristic is nonlinear. This non linearity is the main reason for harmonics during excitation. Sources of harmonics in transformer may be classified into four categories as follows: 1. NORMAL EXCITATION: Normal excitation current of a transformer is non-sinusoidal. The distortion is mainly caused by zero sequence triplen harmonics and particularly the third
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Harmonics has effect on transformer in various ways, e.g.: 1. Core loss: Harmonic voltage increases the hysteresis and eddy current losses in the lamination. The amount of the core loss depends on harmonic present in supply voltage design parameter of core materials and magnetic circuit. 2. Copper loss: Harmonic current increases copper loss. The loss
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Transformers are susceptible to damage by secondary short-circuit currents having magnitudes that can be many times rated load current. The damage results from the following effects: >> The I2R losses in the winding conductors are increased by the square of the current. This increases the temperature rise of the windings. >> Because protective devices limit the duration of
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