Application of a Digital Signal Analyzer to the easurementTofF Power System Ground Impedances
A new method is described for measuring the impedance of power system ground systems where, because of a significant reactive component or the presence of a large residual power system voltage, conventional ground resistance measuring instruments cannot be used. A white noise source together with a digital signal analyzer are used. Results of three applications are given.
Online Monitoring of Substation Grounding Grid Conditions Using Touch and Step Voltage Sensors
A grounding grid of a substation is essential for reducing the ground potential rises inside and outside the substation during a short-circuit event. The performance of a grounding grid is affected by a number of factors, such as the soil conductivity and grounding rod corrosion. Industry always has a strong desire for a reliable and cost-effective method to monitor the condition of a grounding grid to ensure personnel safety and prevent equipments damage. In view of the increased adoption of telecom and sensor technologies in power industry through the smart grid initiative, this paper proposes an online condition monitoring scheme for grounding grids. The scheme monitors touch and step voltages in a substation through a sensor network. The voltages are created by a continuously-injected, controllable test current. The results are transmitted to a database through wireless telecommunication. The database evaluates the grid performance continuously by comparing the newly measured results with the historical data. Many of the limitations of the offline measurement techniques are overcome. Computer simulation studies have shown that the proposed scheme is highly feasible and technically attractive.
Ground Fault Current Distribution Between Soil and Neutral Conductors
When a phase-to-ground fault occurs on a grounded power network, the current returns to the generating sources through the soil and the neutral conductors. The magnitude of the fault current and its distribution in soil and neutral conductors are of prime importance to, design safe grounding installations, calculate accurately electromagnetic induction on neighbouring circuits and determine the optimum setting of the protective relays.