Three-phase synchronous motors are widely used in the industrial motor driven systems. Variable frequency drives (VFDs) which allow soft-start of motors produce PWM voltage. Numerical relays are used in the protection schemes of these high voltage motors. The location of current transformer (CT) is an important criterion in the protection circuit. Impact of harmonics and the location of current...

The knowledge of DC time constants in fault currents at system nodes is important to design the protection system and validate the calculation models for power system simulations. In this paper, we present methods to estimate Thévenin’s impedance and DC time constants in fault currents with application to disturbance records. Additionally, a comparison between both parameters is shown. We demon...

This paper proposed a new wavelet based method to identify inrush currents and to distinguish it from power system faults. The proposed algorithm extracts fault and inrush generated transient signals using DWT. Transient current signals at both sides of a transformer are firstly captured. The wavelet transform is a relatively new and powerful tool in the analysis of power transformer transient ...

The Hot Spot Temperature (HST) value depends on the ambient temperature, the rise in the top oil temperature (TOT) over the ambient temperature, and the rise in the winding HST over the top oil temperature. In this paper a new semi-physical model comprising of the environmental variables for the estimation of HST and loss of insulation life in transformer is proposed. The winding hot-spot tempe...

Power transformers are one of the most critical devices in power systems. It is responsible for voltage conversion, power distribution and transmission, and provides power services. Therefore, the normal operation of the transformer is an important guarantee for the safe, reliable, high quality and economical operation of the power system. It is necessary to minimize and reduce the occurrence o...

Original scientific paper Measurement of grid voltage harmonic components is an important part of power quality measurements. Current high voltage transformers with iron core are not linear and cannot easily be used for accurate measurement of "polluted" voltages in wide frequency range. In this paper, design details of a new coreless voltage transformer for power quality measurement are given....

Power transformers are important and expensive components in the electric power system. The knowledge of the actual status of the transformer insulation behavior, load tap changer performance, temperature, and load condition is necessary in order to evaluate the service performance concerning reliability, availability and safety. Systems abnormalities, loading, switching and ambient condition n...

This research embodies the design, construction and simulation of a feeder pillar (415VAC) with over-current, overload and earth-fault protection with the aid of a phase sequence relay, contactor, earth-leakage circuit breaker and three-phase overload relay. The analog voltmeters in the various bus-bars (red, yellow and blue phases) in a conventional feeder pillar is replaced with a digital pan...

Using a top-down design methodology, two levels of hybrid electric vehicle power system are presented in the paper. At the highest abstraction level, a behavior modeling method is used to develop models for 3-phase AC/DC converter and brushless DC motor controller, which reduce the simulation time without compromise of accuracy. At the second level of design, six diodes along with delta-delta a...

With the rapid development of power electronics technology, the applications of inductively coupled power transfer make the wireless power transmission reality. In order to explore the practical application in the field of ICPT, we analysis the core component of a loosely coupled transformer of ICPT and design it. We make a model and simulate the core magnetic field distribution of the loosely ...