Partial discharge (PD) measurements have proved their reliability for health monitoring of insulation systems in power system components including synchronous generators, power transformers, switchgear and cables etc. Online condition monitoring and pro-active detection of PD faults have been highly demanded over the last two decades. This paper provides results from a research project to develop advanced non-intrusive sensing technologies that are cost effective, reliable and efficient for early detection of PD faults in medium voltage (MV) and high voltage (HV) air-insulated switchgear. Three sensors (high frequency E-field (D-dot) sensor, Rogowski coil and loop antenna) have been developed and tested under various PD faults and their performance were evaluated in comparison with high frequency current transformer (HFCT) which is being used commercially for PD testing and measurement. Among these three sensors, it is shown that D-dot sensor and Rogowski coil are more dependable when it comes to the PD measurements due to their high signal to noise ratio and hence high accuracy. These sensors can be customized according to a specific application and can be connected together with one data acquisition device while developing an online condition monitoring system.
Electricity demand in a certain locality varies during the day, depending on weather conditions, daily life routines, or a social event in a town. During high/peak demands, expensive power plants are put into operation, which affects electricity prices. Moreover, power lines are overloaded. If generation capacity is insufficient, a blackout may result. Demand response (DR) programs are widely proposed in energy research to tackle these problems. Although the benefits of DR programs are well known, customer response levels to these programs is low. This is due to the small fraction of benefits they receive against the loss of comfort, lost leisure time, and other inconveniences. The objective of this work is to study DR costs from the customer perspective by considering these factors. A customer survey-based direct approach is used to evaluate the willingness of customers to accept (WTA) a certain compensation when shifting the load is adopted. Two different methods are used to calculate DR costs: percentage compensation, which customers are WTA, and one based on a macroeconomic model, which considers the dependency factor of customers on loads and hourly wage. A linear mathematical model is presented based on both these techniques. This study reveals that DR costs are much less than interruption costs paid by the utility company, and hence is in the best interests of all stakeholders, i.e., customers, utility company, and transmission company.
Partial Discharge (PD) measurements are considered as the early detection of insulation degradation in power system equipment. In switchgear and power cables, multiple PD faults may exist, which make the detection and location of such incipient faults challenging. This paper deals with identification of multiple PD faults by a hybrid detection technique, by combining conventional and unconventional measurement methods.Unconventional PD measurements rely on detection of physical emissions due to such faults, e.g. detection of radio frequency (RF) electromagnetic (EM) fields in the vicinity of PD activity, ultrasonic waves, optical emissions and heat produced by the PD, whereas the conventional measurement methods are based on detection of high frequency current and voltage, superimposed on the power frequency current and voltage.In this paper, the apparent charge of PD events is calculated by using conventional measurement technique and EM signal energy is calculated based on unconventional method. The high frequency electric field was measured using a D-dot sensor. The comparison between the two parameters show that a second degree polynomial relation exists between the EM energy and apparent charge. The scatter plots between the two variables show a number of patterns due to the number of PD faults. Therefore, the detection of multiple faults is possible.
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