Phasor diagrams in relay protection

This course consists of three parts. During the course we will to a great extent make use of our interactive models, which have been programmed by Andrew and can be found here. The course is currently in preparation. We ask for your patience!

Part 1: The first part deals with the theory of alternating current. We will remember how phasor diagrams come into being and how they are used in relay protection. We will talk about the relationship between current and voltage on the most important elements, transformers and three-phase electrical networks. We will finish the first part with the method of symmetrical components, which is of great importance for analysing faults in an electrical network.

Part 2: In the second part of the course, we will analyse the main operating modes of power grids. We will start with normal load operation and post-fault operation. We will then move on to short circuits, earth faults, open-phase conditions, etc., i.e. the specific processes in the network that directly affect the work of a protection engineer.

Part 3: The third part essentially deals with the conversion of primary quantities into secondary quantities, i.e. the quantities that are actually recorded by the protection device. Here we’ll look at different circuits of CT’s and VT’s. We will also direct our attention to the most interesting cases, e.g. the operating mode or phasor diagrams of an directional overcurrent relay. In the end of the course we’ll go through topics like the disadvantage of using a circuit with two CT’s in the case of a double earth fault and other interesting phenomena that you may come into contact with in your work as a protection engineer.