Harmonic Analysis a Root Cause Finder for Repet...


Harmonic Analysis | Encon Engineers How NLL affect today's electrical power system? A study of electrical power harmonic analysis helps to know the root cause of equipment and drive failure for correctional power-related steps. Today's Engineers are finding a power quality problem that is becoming increasingly apparent is the harmonic distortions of the fundamental waveform. The problem has arisen due to extensive use of Non-Linear Loads (NLL) in today's electrical power system, which alter sinusoidal shape of the sine wave, and thereby cause harmonic generations and distortion power factor (PF) in the power System. Harmonics are as old a phenomenon as the introduction of the AC System. Mercury Arc Rectifier (MAR) developed in 1920's and Semiconductor Controlled Rectifiers (SCR) and Thyristors developed in 1950's created harmonics due to their nature of non-linear-load. Its usage was much lesser then, typically 5% in 1960, that could not have created any significant impact on the power system. However, economic prosperity coupled with technological advancements have mandated today's comfort conditions those necessitate employing matching controls which are increasingly introducing nonlinear loads which are altering the very sinusoidal characteristic of current and voltage waveforms and creating Harmonics and bad Power Quality. Measurement units of Power Quality Harmonics are defined by Total Voltage Harmonic Distortion THDv and Total Current Harmonic Distortion THDi. THD values are calculated as the sum of square root of individual harmonics namely 2nd, 3rd, 4th, 5th, 6th, 7th, ... nth divided by fundamental current/voltage. The fundamental harmonics are the 50hz/ 60hz values for voltage and current. The Conventional engineering design: It lowers the plant's Load Factor wherein the degree of equipment derating scales up with the degree of Nonlinear loads. It helps in skirting the problem but with a guzzling infrastructure that not only produces lesser quality of products but also requires higher investment cost for having higher sized equipment. The plant's power system though manages to survive the harmonics onslaught, the virus remains in a dormant stage that occasionally could strike under its favorable power quality conditions. The least it creates energy losses and occasional equipment tripping. Electronics are first to fail as being the most susceptible followed by capacitors, fuses, switchgears, motors -ac/dc/servo, ct, pt, transformers, cables and its terminations. The most common Harmonic Problem that we encounter while conducting field measurement and harmonics analysis is capacitor and detuned filter drawing high current, bulging, flashing and even blasting of capacitors, reactors or switchgear. Capacitors themselves do not cause any harmonic problem. But if significant Nonlinear loads are present in the electrical power system it aggravates a potential harmonic problem. Any combination of capacitance and inductance forms a Resonance Frequency at which the capacitive and inductive reactance equals. If significant harmonic energy is present either inside the plant or outside in the Grid and its frequency matches with the resonance frequency formed by the Power Factor (PF) correcting capacitors or Detune Filters, it excites current into an oscillation, and results in high harmonic magnifications. Its effect can damage equipment and reflect in an excessively high harmonic distortion, both in voltage and current. Our harmonic audit across most industry segments find following types of equipment failures due to harmonic distortions and bad power quality failures.

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