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This paper presents a method for voltage stability monitoring based on the maximum power transfer to the load. The only required information is the system topology, the data from PMUs and the operational status of synchronous generators. With this information, the Thevenin impedance seen from a load bus can be estimated and by using the Thevenin theorem for maximum power transfer an impedance based...
Protective relays used in power system today measure external signals to diagnose the internal state of the equipment they protect. Based on measurements of voltage, current, frequency at the bus, the decision is made whether the equipment is healthy or faulty. Due to advances in sensing and computing, it has become possible to use the external measurements to dynamically estimate the internal state...
Modern microprocessor-based relays can be vulnerable to attacks from sophisticated cyber-adversaries. In the case of synchronous generators, specifically, out of step (OOS) protection, we show that a “hacked” relay can be made to respond exactly contrary to design, which can be disastrous to system operation. We propose a computational alternative - using the concept of Dynamic State Estimation (DSE)...
The overlapping time of double-contact circuit breakers is defined as the time delay elapsing between the opening of the nominal and the arcing contacts. It is an important criteria for the circuit breaker lifetime. It is usually determined indirectly on live breakers, e.g. derived from the number of breaking operations and the interrupted current amplitude, or directly during the breaker overhaul,...
Generator Circuit Breakers (GCBs) are commonly used in electrical power generation systems to protect key equipment such as transformers and generators from damage due to overload or short-circuit. However the interruption and feeding of high currents lead to the ablation of the electrical contact system of the breaker. This deterioration process needs to be monitored in order to guarantee the healthy...
This paper presents a real-time voltage stability monitoring method based on estimation of maximum power transfer. The approach solely requires information from PMUs installed at concerned load buses at substations in addition to available information of system topology and load power obtained from SCADA/EMS or state estimator. The proposed algorithm estimates the Thevenin impedance seen at the load...
Voltage sags are short duration reductions in rms voltage caused by short circuits, overloads and starting of large motors. Voltage sag is much more of a global problem. For proper analysis and mitigation of voltage sag, their characterization is important. The magnitude and durations are main characteristics of voltage sag. In this paper voltage sag and their characteristics have been presented in...
All distributed generators (DG), especially those connected to low voltage distribution grids are required to detect islanding conditions. The methods for detecting islanding are classified in three main categories: passive, active and communication based. Passive methods are based on grid monitoring, are easy to implement but have a large non-detection zone in the case local generation meets the...
Experience with connecting farm biogas generation to rural distribution feeders in Ontario has revealed several challenges with electrical protection. The biogas projects are small (<;500kW), synchronous, farm-based, and looking for an affordable protection solution involving the use of only low-voltage equipments. The utility feeders are generally at the 8.3kV and 12.5kV voltage levels, can involve...
We propose a novel dual-mode neural stimulator circuit. For stimulation requiring small or medium amount of charge, the stimulator supplies a constant current to the stimulation load in the same way as any standard current-mode stimulator. For high-charge stimulation applications, the stimulator supplies a variable stimulus current, depending on the voltage available across the current generator circuit...
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