Indepth Electrical engineering

Methods for Reducing Harmonics in Electrical Systems Harmonics are one of the biggest challenges in modern electrical systems, especially with the growing use of non-linear loads such as Variable Frequency Drives (VFDs), rectifiers, and electronic devices . Excessive harmonics can lead to equipment overheating, reduced efficiency, nuisance tripping, and overall poor power quality . Fortunately, several methods exist to reduce harmonics and improve system reliability. Let’s explore the most effective solutions. 1. DC Choke Application: Commonly used in VFDs (a major source of harmonics). Working Principle: A DC choke is an inductor in series with the DC link of the semiconductor bridge circuit. Effect: Reduces 5th and 7th order harmonics Improves current waveform smoothness Comparable to AC-side line reactors (though THD reduction is slightly less). ✅ Key Point: DC chokes are simple, cost-effective, and wide...

Harmonics in Electrical Systems: Causes, Effects, and Impact on Equipment What Are Harmonics? Harmonics are unwanted voltages and currents in electrical systems that distort the fundamental waveform (50 Hz in India). They arise due to non-linear loads that draw current in abrupt pulses rather than smooth sinusoidal waves. In simple terms, harmonics are like pollution in electricity —they degrade power quality without necessarily affecting power availability. Classification of Harmonics Harmonics are integer multiples of the fundamental frequency (50 Hz): 2nd harmonic (100 Hz) 3rd harmonic (150 Hz) 4th harmonic (200 Hz) … up to the 11th harmonic (550 Hz) and beyond. Depending on their order: Negative Sequence Currents: 2nd, 5th, 8th, 11th Zero Sequence Currents: 3rd, 6th, 9th Positive Sequence Currents: 4th, 7th, 10th Why Are Harmonics Increasing? The rise in harmonics is directly linked to the increasing use of electronic and power conversion de...

Electricity from Potatoes and Fruits: Science Behind the Experiment Generating electricity from simple household items like potatoes, lemons, or apples may sound like a classroom trick, but the concept is deeply rooted in electrochemistry . The principle is the same as that used in early batteries: when two dissimilar metals are placed in an electrolytic medium , an electron flow (electric current) is created. Basic Principle When metals such as zinc and copper are inserted into an electrolyte (like potato juice or lemon juice), a chemical reaction occurs. The electrolyte enables ions to move between the electrodes. The difference in reactivity of the two metals creates a potential difference, which drives electron flow through an external circuit. Zinc electrode → acts as the anode (oxidation occurs). Copper electrode → acts as the cathode (reduction occurs). Electrolyte (potato/fruit juice) → provides the ionic medium. This setup is essentially a Galvanic Cel...

Synchronous machines construction depends upon type of prime mover used in machines. There are following types of prime movers used in power generation:- 1.        Steam turbines 2.        Hydraulic Turbines 3.        Diesel Engines Let’s discuss them :- 1.      Steam turbine:- These types of synchronous machines have high speed.  Generators driven by steam turbine are also called Turbogenerators. Maximum speed of Turbogenerators is 3000 RPM as per formula Frequency= PN/ 120; Where P is no. of poles N is no. of revolutions In 2 Pole machine at 50 HZ frequency Speed of Turbogenerator comes out to be= 50X120/ 2= 3000 RPM With Such high speed lower value of armature diameter is to be designed. Lower diameter is selected to limit the centrifugal forces which have very much influence on the generator design. Peripheral Speed of a Machine is given by f...

Why Armature Winding is Placed on Stator and Field Winding on Rotor in Synchronous Machines? In synchronous machines—both synchronous generators (alternators) and synchronous motors—the armature winding is always placed on the stator while the field winding is mounted on the rotor . This construction is not accidental; it offers clear technical and economic advantages. Let us analyze these reasons step by step with practical examples. 1. Better Economy of Construction If the armature winding were placed on the rotor , slip rings would need to carry very high currents at high voltages , making the system bulky, costly, and inefficient. Example: Consider a 3-phase, star-connected, 500 MVA, 11 kV synchronous generator : Line current, I = 500 × 10 6 3 × 11 × 10 3 = 26 , 244  A I = \frac{500 \times 10^6}{\sqrt{3} \times 11 \times 10^3} = 26,244 \text{ A} If this huge current were carried through slip rings, we would require 3 slip rings rated for 26.2 kA each , insulate...

Cable Fault Detection Methods in Electrical Systems In electrical systems, cables are prone to faults due to insulation failure, moisture ingress, overloading, mechanical damage, or aging. Detecting and locating the fault accurately is crucial because replacing long underground cables can be expensive and time-consuming. Here are the most widely used methods of cable fault detection : 1. Megger Testing (For LT Cables) Purpose: Checks insulation resistance of low-tension cables. Process: Apply 500V/1000V DC using a Megger. Infinite reading → Cable is healthy. >100 MΩ → Acceptable (may have slight moisture, which usually dries when load is applied). 50–100 MΩ → Usable for light loads. ≈0 Ω → Faulty cable (short between conductors or between conductor and armour). 🔹 Additional Use: Resistance measurement between two terminals using Megger. 2. Hi-Pot Testing (For HT Cables) Purpose: Tests insulation strength of high-tension (HT) cables. Pro...