DIRECTIONAL OVERCURRENT RELAY

Functionality and distinctive features:

• You can assess the effect of the short-circuit type and fault location (in relation to the installation location of the protection) on the phasor diagrams and the directional overcurrent relay;
• In the model, three types of the directional overcurrent relay are realised with the following methods of directional measurement: phase quantities (corresponding to the 90° connection, i.e. phase current with cross-polarised line voltage), with positive sequence quantities, with negative sequence quantities;
• System impedances are purely reactive. It is further assumed that X₁=X₂;
• The impedance of the line is ohmic. It’s further assumed that X₁=X₂, R₁=R₂;
• The values of the line voltages of the power systems and their impedances can be entered in V or in Ω as well as in p.u.. The scale of the figure changes automatically;
• To model the power flow on the line, the rotor angle difference between the power systems can be changed;
• The marker can be used to move the fault location along the line;
• Along the power line curves of the positive-sequence voltage (green) and the negative-sequence voltage (blue) are shown;
• Changing the currents is accomplished in two steps: first the phasor values are changed to be able to evaluate the dynamics (increase or decrease in current), then the scale is changed and all phasors are realigned within the boundaries of the screen.