The primary effect of harmonics on power cables is the additional heating due to increase in the I2R losses. This can be attributed to the two phenomena known as skin effect and proximity effect, both of which vary as a function of frequency as well as conductor size and spacing. Also, cables involved in system resonance, may be subjected to voltage stress and corona, which can lead to dielectric (insulation) failure.
Monday, August 22, 2011
The detrimental effects of harmonics on motors and generators are usually taken for granted due to complacency or lack of knowledge. For example, the increase application of variable frequency drives (VFD) has subjected motors to considerably higher harmonic levels compared to when it was still using traditional controllers. As a consequence, the machine efficiency and torque developed are significantly affected.
Friday, August 19, 2011
Active Harmonic Filters (AHF) are power quality devices that monitor the nonlinear load and dynamically provide controlled current injection, which cancels out the harmonic currents in the electrical system. They also correct poor displacement power factor (DPF) by compensating the system’s reactive current. The concept applied is relatively old, but the lack of effective methods hampered its development for a number of years. Presently, the widespread use of Insulated Gate Bipolar Transistors (IGBT) and the availability of Digital Signal Processing (DSP) components are paving the way for the emergence of active harmonic filters.
Thursday, August 18, 2011
IEEE 1531 has outlined key harmonic filter design considerations for its proper selection. They are grouped into performance and rating criteria. The former relate to normal expected operating conditions. Meanwhile, the rating criteria refer to unusual conditions that may place a more severe duty on the equipment.
Sunday, August 14, 2011
The purpose of this ETAP Tutorial is to show how to size a shunt passive harmonic filter using the Harmonics Module. It illustrates the advantage of using the ETAP software to improve the speed and accuracy in conducting the power quality study needed to determine the appropriate capacitor and reactor ratings. This is made easy with the help of the Harmonic Filter editor, which provides all the practical and popular filter structures for the user to choose from.
Saturday, August 13, 2011
hey are built using a series of capacitors (capacitance) and reactors (inductance) forming an LC circuit in parallel with the power source. More complex designs may involve multiple LC circuits, some of which may also include a resistor. The passive harmonic filter
Tuesday, August 9, 2011
Harmonic Filters are used to mitigate the power quality problem known as harmonic waveform distortion. Consequently, they minimize the thermal and electrical stress on the electrical infrastructure, eliminate the risk of harmonics-related reliability issues and allow for long-term energy efficiency and cost savings. Harmonic filters will play a vital role in ensuring a better power quality, especially now that most modern electrical devices are of the nonlinear type.
Sunday, August 7, 2011
According to Reuters report, there have been three large explosions from the sun in the past days, and that sun storms are set to hit the Earth. These incidents have pressed the U.S. government to warn “users of satellite, telecommunications and electric equipment to prepare for possible disruptions over the next few days."
Saturday, August 6, 2011
True RMS Multimeter, as the name suggest, measures the real root mean square value of the input current and voltage. It utilizes an integrated circuit that derives the true RMS of dynamic and complex waveforms of all shapes and sizes. This capability allows the true RMS multimeter to provide accurate measurements regardless of current and voltage waveform (i.e. pure sinewave, square, harmonic-distorted or non-sinusoidal).
Friday, August 5, 2011
Power System Harmonic Analysis provides a comprehensive input about harmonics in the power system and the corresponding theories and discussions. It gives sufficient information regarding harmonics - a growing issue in this electronic age, including analytical and modelling tools for the evaluation of power quality. On the contrary, the book was not able to converse about the different mitigation techniques against harmonics, which could have made it a comprehensive reference for both power quality engineers and students.
Thursday, August 4, 2011
K-Factor Transformer, also known as K-Rated transformer, is designed for nonlinear or harmonic generating loads that a standard transformer could not adequately handle due to overheating. K-factor transformers are specially assembled with a double sized neutral conductor, heavier gauge copper and either change the geometry of their conductors or use multiple conductors for the coils. These properties allow them to endure the additional heat caused by harmonic currents much better than a standard transformer.
Wednesday, August 3, 2011
Single-phasing is the worst case of unbalance and can either be due to an open phase in the primary or secondary side of a transformer. However, this post will only tackle single-phasing on transformer primary, which exposes electrical equipment such as three-phase motors to unbalance voltages. Consequently, excessive unbalance currents will exist with one line to have at least 230% of normal current drawn by the motor.
Tuesday, August 2, 2011
The negative effects of harmonics on transformers are commonly unnoticed and disregarded until an actual failure happens. Generally, transformers designed to operate at rated frequency have had their loads replaced with nonlinear types, which inject harmonic currents into the system. Consequently, transformers that have operated adequately for long periods have failed in a comparatively short time.
- I am a Professional Electrical Engineer with a Masters Degree in Business Administration. My interest is in Power Quality, Diagnostic Testing and Protective Relaying. I have been working in an electric distribution utility for more than a decade. I handle PQ studies, power system analysis, diagnostic testing, protective relaying and capital budgeting for company projects.