Syafruddin Hasan

Magnetizing Current, Harmonic Content and Power Factor as the Indicators of Transformer Core Saturation

Abstrac t—The paper proposes a measurement method for obtaining the parameters needed to calculate a reliable indicator of the state of transformer core saturation. The major nonlinear effects in transformer core are saturation, eddy current and hysteresis. Saturation is the predominant effect in power transformers, followed by eddy current and hysteresis effects. In saturation, a transformer core act as a source of current generating harmonics, some of which will flow directly toward the primary and secondary windings. The method is based on magnetization current, harmonic content and power factor evaluated of the transformer no-load current with high magnetic flux density subjected. The investigation is done on single phase model core type transformer. The transformer is connected to variable voltage variable frequency (VVVF) source and the investigation is done on various flux densities. The results show that the magnetization current and harmonic content increase significantly when high magnetic flux densities are injected and vice versa with power factor that decrease sharply. These phenomena can be used as the indication of transformer core saturation.

Effect of DC bias on magnetization current waveforms of single phase power transformer

An investigation of magnetizing current waveforms of single phase power transformer due to DC bias injection through simulation and experimental study is present in this paper. A method base on MATLAB simulation that is capable of predicting of magnetizing current without and with DC bias is used. The experimental study is done by the DC bias current injected simultaneously with AC source to primary winding of transformer and the secondary side is open circuit. The results show that the waveforms distorted when the DC bias exist. The pulsated waveforms are pushed to half cycle in which the bias current is in the same direction as magnetizing current (unsymmetrical pulsated) and even harmonics are significant. The simulated waveforms have good agreement with the measured one.

K-factor due to implementing of DC unbalanced/balanced of a transformer

This paper presents the effects of harmonic distortion on loaded single phase two winding transformer.The impact on K-factor is studied by implementing DC unbalanced and balanced configurations. The measurements are done online from the primary side. The result shows that the current total harmonic distortion (THDi), power factor (PF) and K-factor not only depend on type of loads but also depend on the voltage level which supplies to primary winding. By determining the K-Factor which influence the heating effect, then an appropriate transformer can be designed.

Harmonics Performances of Single Phase Transformer due to DC Bias

The investigation of the direct current (dc) bias effect on single phase power transformer through their harmonics performance is present in this paper. The experimental study is done by the dc bias current injected simultaneously with alternating current (ac) source to primary winding of transformer. The input ac voltage to primary winding is maintained constant during investigation and the dc currents increased gradually. Compare to pure ac power applied, the results show that the waveforms distorted when the dc bias exist. The pulsated waveforms are pushed to half cycle in which the bias current is in the same direction as magnetizing current (unsymmetrical pulsated) and even harmonics are significant.

Survey of Droop Control Technique for Parallel Inverter Operation

Increasing demand for large-scale power delivery with high reliability and quality necessitates the use of multiple distributed energy resources to be connected in parallel; for example, parallel inverters operation. Proper operation of parallel inverters requires sophisticated control techniques and many have been proposed and continue to evolve. This paper depicts the droop control techniques for the parallel inverter systems. The recent improvements and variants of this control technique are presented

Effects of Different Voltage Sag Types on Induction Motor

This paper analyzes effects caused by voltage sag types A, B, C and D on induction motor based on experimental test. The effect can be investigated in term the current peaks and speed variation. The magnitudes depend on magnitude of sag and duration, voltage sag types, during and recovery voltage sag. Several of voltage sag characteristics have been conducted in different magnitude, duration and sag types. The results show that the current peaks generated reach more than 4 times of normal current and it was achieved at recovery voltage instant. Sag magnitude has great influence on the current peak but sag duration is not significantly. Type A voltage sag only can cause the motor stop running and it was achieved when it was subjected to sag magnitude of 10% and 6s in duration. The motor stops running in shorter duration when it was subjected to interruption with sag duration of 4s. Therefore voltage sag of type A lead to more severe on induction motor if compared with other sag type. This is according to number of phase that experience sag. The magnitude and duration of voltage sags have influenced significantly on the motor speed only for low sag magnitude and long sag duration.

Accurate phase to phase fault resistance calculation using two terminal data

Faults can occurred at the transmission line due to lightning strike, broken conductor, cross arm or tower falls, danger tree, crane or animal encroachment, polluted insulator etc. Each type of fault will represents a fault resistance value. Fault resistance will affects the accuracy of protection relays in fault location and fault zone detection. Phase to phase fault is one type of unsymmetrical fault at the transmission line. This paper represents the accurate way to calculate the actual phase to phase fault resistance value by using data from both local and remote substations. From the finding, the actual fault resistance can be represented by fault resistance as seen from local substation in parallel with the fault resistance as seen from remote substation. To prove the finding, simulation has been carried out and the results show the validity of the proposed theory.

Core loss characteristics analysis of power transformer under different frequencies excitation

This paper presents a simplified method for determination the separation of hysteresis and eddy current losses characteristic of power transformer. The model tuning is performed by energized the transformer core in no-load condition with sinusoidal voltage waveform, different frequencies and the magnetic flux density in transformer core always constant maintained. The core loss splitting is obtained by using two-frequency method. The results show that at low frequency, the appearance of hysteresis loss is visible, but at higher frequency, the eddy current loss is more significant.

Effects of DC line voltage environment on different types of compact fluorescent lamps operation

Compact fluorescent lamps are tested under DC operating conditions. Five random samples are evaluated in term of their starting and operation response compared to normal AC environment. Experiment result shows that DC line supply has successfully able to start and operate any conventional CFL at almost the same lux level and power consumption rate of 240ac rms.

Harmonic content as the indicator of transformer core saturation

The paper proposes a measurement method for obtaining the parameters needed to calculate a reliable indicator of the state of transformer core saturation. The major nonlinear effects in transformer core are saturation, eddy current and hysteresis. Saturation is the predominant effect in power transformers, followed by eddy current and hysteresis effects. In saturation, a transformer core act as a source of current generating harmonics, some of which will flow directly toward the primary and secondary windings. The method is based on harmonic content evaluated of the transformer no-load current with high magnetic flux density subjected. The investigation is done on single phase model core type transformer. The transformer is connected to variable voltage variable frequency (VVVF) source and the investigation is done on the same flux density. The result has been compared with normal frequency supply (50 Hz). The results show that the harmonic content increase significantly when high magnetic flux densities are injected.