perunitrepresentationer

Perunitrepresentationer is a system for expressing electrical quantities such as voltage, current, impedance, and power as dimensionless ratios relative to a base value. This simplifies complex power system analysis by eliminating the need to work with large or small numbers and the associated units. The "per unit" value is calculated by dividing the actual value of a quantity by its chosen base value. For example, if the base voltage is 100 kV and the actual voltage is 110 kV, the per unit voltage is 110/100 = 1.1 pu. Similarly, base current is determined by base voltage and base power, while base impedance is derived from base voltage and base power. A key advantage of the per unit system is that impedance values remain the same regardless of the voltage level of the transformer winding they are associated with. This is because the base voltage changes proportionally with the transformer's turns ratio. This consistency greatly aids in the analysis of interconnected power systems with multiple voltage levels, such as those found in transmission and distribution networks. The per unit system is widely used in power system engineering for load flow studies, short-circuit analysis, and stability calculations.