Analytical derivation of PSS parameters for generator with static excitation system

This paper presents a methodology for PSS design which results in a PSS producing a nearly pure damping torque component in a wide frequency range. The derivation is based on the Heffron-Phillips single-machine infinite-busbar model and for a generator with static exciter and speed-based PSS. The choice of time constants is very simple and the only parameter still to be optimized is the PSS gain. Effectiveness of the PSS has been confirmed by tests conducted on single- and multi-machine power system model

Improving sensitivity of residual current transformers to high frequency earth fault currents

For protection against electric shock in low voltage systems residual current devices are commonly used. However, their proper operation can be interfered when high frequency earth fault current occurs. Serious hazard of electrocution exists then. In order to detect such a current, it is necessary to modify parameters of residual current devices, especially the operating point of their current transformer. The authors proposed the modification in the structure of residual current devices. This modification improves sensitivity of residual current devices when high frequency earth fault current occurs. The test of the modified residual current device proved that the authors’ proposition is appropriate