What as a Vector Diagram?
A vector diagram is a diagram on which one or more vectors can be represented. On a vector diagram, alternating quantities are represented by an arrow. The length of the arrow represents the rms value of the alternating quantity. The angular position represents the relative position of a vector (alternating current or voltage) with respect to another vector or to a reference axis. The arrowhead represents the direction in which the vector is acting. When an electrical quantity acts away from the source towards the direction of load, the vector represents the quantity is considered a positive vector.
Transformer Vector Diagram
Three phase electrical quantities can be represented by a vector diagram. Vector diagrams which represent three-phase quantities are known as three-phase vector diagrams.
A transformer three-phase vector diagram is required for determining the fault calculation of an electrical power system. Practically, almost every electrical power system deals with three phase power.
Three-phase vector diagrams are commonly used to represent 3 phase transformers are known as transformer vector diagrams.
The voltages of a three phase system is shown in the figure below:
The phase sequence of the vectors, representing voltages, is shown in the figure by an arrow. The term phase sequence is used to indicate the order in which vectors are placed in relation to one another for counter-clockwise rotation. In the figure above three phase-to-neutral voltages are rotating.
This means they would reach their maximum positive values in the sequence first R, then Y and then B. This sequence is referred to as a positive sequence. This represents the normal healthy condition of the system. You can learn more about vector diagrams and transformers by studying our electrical MCQs.