ROTATING MACHINE AS A SOURCE OF HARMONICS

Rotating machines also act as source of harmonics in power system. Causes of harmonics generation in rotating electrical machines are classified into following categories:

1. MAGNETIC NONLINEARITIES OF THE CORE MATERIAL: Nonlinear magnetization characteristics of the core material cause harmonic generation.

2. NON UNIFORM FLUX DISTRIBUTION IN AIR GAP: often it is assumed that the air-gap flux distribution is uniform and the operating principles of rotating machines are discussed based on this assumption. But in most of the rotating machines, flux distribution in air-gap is not uniform which leads to harmonics production.

3. SLOT HARMONICS: slots are inevitable in rotating machines. Alternate presence of slot and teeth changes the reluctance of the magnetic flux varies in similar type of alternating fashion. This variation acts as a reason for harmonic generation. Harmonics produced due to pitch factor and distribution factor.

4. DESIGN PARAMETERS LIKE PITCH FACTOR AND DISTRIBUTION FACTORS: harmonic generation in synchronous generator depends on the different design factors like pitch factor and distribution factors.

5. ROTOR SALIENCY: rotor saliency brings the variation of reluctance in the magnetic path and reactance in electric path which contribute to the harmonic generation.

6. CRAWLING: it is a common problem faced by induction motors. During this fault, odd harmonics like 5th and 7th orders appear. Fifth harmonics rotates in the same direction as of the fundamental but 7th order harmonics rotate in opposite to this direction. It changes the operating characteristics of the motor. During crawling, 7th harmonics is dominating over the 5th harmonics and lowers the stable operating zone to one seventh speed of the rated value.

7. COGGING: It is a problem where induction motors fail to start at all. Harmonic production from the motor during this condition is different from the normal condition.

8. ROTOR MISALIGNMENT: rotor misalignment causes variation of flux linkage in each cycle of rotation contributing to harmonic generation.

9. MASS UNBALANCE: with the aging, mass unbalance is observed specially in the rotor side. This refers to the core property and adds in harmonic generation.

10. BAR BREAKAGE: bar breakage in an induction motor, either symmetrically or asymmetrically, is reflected in harmonic generation in rotor circuit as well as in stator side.

11. FRACTAL ERROR: fractal error in core material produces harmonics.

12. UNSYMMETRICAL FAULT: unsymmetrical fault is also a reason for harmonic generation related to negative sequence components.

PRIMARY SECONDARY AND TERTIARY FREQUENCY CONTROL IN POWER SYSTEMS

Primary, Secondary and Tertiary Frequency Control in Power Systems Author: Engr. Aneel Kumar Keywords: frequency control, primary frequency control, automatic generation control (AGC), tertiary control, load-frequency control, grid stability. Frequency control keeps the power grid stable by balancing generation and load. When generation and demand drift apart, system frequency moves away from its nominal value (50 or 60 Hz). Grids rely on three hierarchical control layers — Primary , Secondary (AGC), and Tertiary — to arrest frequency deviation, restore the set-point and optimize generation dispatch. Related: Power System Stability — causes & mitigation Overview of primary, secondary and tertiary frequency control in power systems. ⚡ Primary Frequency Control (Droop Control) Primary control is a fast, local response implemented by generator governors (dro...

Advantages of Per Unit System in Power System Analysis | Electrical Engineering

Advantages of Per Unit System in Power System Analysis In electrical power engineering, the per unit (p.u.) system is one of the most widely used techniques for analyzing and modeling power systems. It is a method of expressing electrical quantities — such as voltage, current, power, and impedance — as fractions of chosen base values rather than their actual numerical magnitudes. This normalization technique provides a universal language for system calculations, minimizing errors, simplifying transformer modeling, and enabling consistency across multiple voltage levels. Because of these benefits, the per unit system is essential in fault analysis, load flow studies, transformer testing, and short-circuit calculations . ⚡ What is the Per Unit System? The per unit system is defined as: Q u a n t i t y ( p u ) = A c t u a l V a l u e B a s e V a l u e Quantity_{(pu)} = \dfrac{Actual \ Value}{Base \ Value} Q u an t i t y ( p u ) = B a se ...

CASCADED TRANSFORMERS METHOD FOR GENERATING AC HIGH VOLTAGE

High-Frequency AC High Voltage Generation Using Cascaded Transformers Author: Engr. Aneel Kumar Figure 1: Infographic representation of cascaded transformers method for generating high AC voltages. Introduction In high voltage engineering , generating very high alternating current (AC) voltages is essential for testing equipment like insulators, circuit breakers, power cables, and other apparatus. One common and effective method for producing such voltages is the cascaded transformers method . This technique uses a series connection of specially designed test transformers , where the secondary of one transformer feeds the primary of the next. In this way, voltages are built up step by step, achieving levels in the range of hundreds of kilovolts (kV) or even megavolts (MV). Working Principle The principle of cascaded connection relies on the fact that each...

ADVANTAGES AND DISADVANTAGES OF CORONA EFFECT IN TRANSMISSION LINES | ELECTRICAL ENGINEERING GUIDE

Advantages and Disadvantages of Corona Effect in Power Systems In high-voltage overhead transmission lines , the corona effect plays a critical role in system performance. Corona occurs when the air around a conductor becomes ionized due to high electric stress. While often seen as a drawback because of power losses and interference , it also provides certain engineering benefits . This article explains the advantages and disadvantages of corona effect in detail, with examples relevant to modern electrical power systems. ✅ Advantages of Corona Effect Increase in Virtual Conductor Diameter Due to corona formation, the surrounding air becomes partially conductive, increasing the virtual diameter of the conductor. This reduces electrostatic stress between conductors and minimizes insulation breakdown risks. Related Reading: Electrostatic Fields in High Voltage Engineering Reduction of Transient Surges Corona acts like a natural cushion for sudden ...

ADVANTAGES OF INTERCONNECTED GRID SYSTEM

Interconnected Grid System: Working, Advantages, Disadvantages, and Comparison with Isolated Grids Author: Engr. Aneel Kumar Figure 1: Infographic showing key advantages of an interconnected grid system. Introduction An interconnected grid system refers to a network of multiple power generation sources, transmission lines, substations, and distribution systems that are linked across regions, states, or even countries. Unlike an isolated grid (or islanded grid) which operates independently, an interconnected grid allows electricity to flow between interconnected nodes, enabling numerous benefits and some trade-offs. In today’s energy landscape—where demand, renewable generation, reliability, and cost pressure are all increasing—understanding how an interconnected grid works, what factors are essential, and what its advantages and disadvantages are is critical for utility planners, reg...

Control Strategies for TCSC: Techniques for Dynamic Power Flow Management

Introduction As power transmission networks grow more complex, real-time voltage and impedance control becomes essential for ensuring grid reliability. Thyristor Controlled Series Capacitors (TCSC) play a key role in dynamically adjusting transmission line reactance, but their effectiveness depends on advanced control strategies . Different control methodologies —ranging from open-loop and closed-loop systems to AI-driven predictive models —allow TCSC to optimize power flow, improve stability, and enhance energy efficiency . In this article, we will explore: ✅ Different types of TCSC control strategies ✅ The role of real-time monitoring in optimizing power flow ✅ How AI and machine learning improve TCSC performance Keywords: AI-Based Power Flow Control, TCSC Dynamic Impedance Regulation, Real-Time Voltage Stabilization, Smart Grid FACTS Controllers Understanding TCSC Control Strategies A TCSC regulates transmission line reactance by adjusting thyristor switch...

DIFFERENCE BETWEEN GRID STATION AND SUB STATION

An electrical power substation is a conversion point between transmission level voltages (such as 138 KV) and distribution level voltages (such as 11 KV). A substation has one or more step-down transformers and serves a regional area such as part of a city or neighborhood. Substations are connected to each other by the transmission ring circuit. An electrical grid station is an interconnection point between two transmission ring circuits, often between two geographic regions. They might have a transformer, depending on the possibly different voltages, so that the voltage levels can be adjusted as needed. The interconnected network of grid stations is called the grid, and may ultimately represent an entire multi-state region. In this configuration, loss of a small section, such as loss of a power station, does not impact the grid as a whole, nor does it impact the more localized neighborhoods, as the grid simply shifts its power flow to compensate, giving the power station o...

ENGINEERING ARTICLES

Search This Blog