## PN Junction Diodes and BJT Transistors: an Introduction

This article provides a brief introduction to PN junction diodes and BJT transistors. Doping Silicon: N-Type and P-Type Semiconductors PN junctions play an important role in semiconductor fabrication for integrated circuits. An undoped silicon with a valence of four has an intrinsic concentration of ${{n}_{i}}=1.1\times {{10}^{16}}\text{ }carriers/{{m}^{3}}$ at room temperature. …

## Three Phase Power Measurement in Three Phase Circuits

Different methods are utilized in order to measure three-phase power in a three-phase circuit. In this particular article, we are going to discuss the following methods in detail: One Wattmeter Method Two Wattmeters Method Three Wattmeters Method A customer of a three-phase electrical service, three-wire or four-wire, will have a …

## Single & Three Phase Grounding

The National Electrical Code (NEC) defines “ground” as  “A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.” Single-Phase Grounding The grounding of a typical residential, single-phase service is represented in Figure …

## Grounding Electrical System | Purpose of Grounding Electrical Systems

According to the common practice that was followed years ago, many electrical installations were not grounded. Perhaps the need for adequate grounding was not fully recognized, understood, or considered necessary. Today, electrical grounding is considered important to most, but not all, electrical installations. Yet, the importance of proper electrical grounding …

## Per Unit Calculation | Per Unit System Examples

The per unit (PU or P.U.) method of calculation is often used as an aid in the analysis of electrical systems that operate at different voltage levels. The determination of per unit values is not the end objective of a study. Rather determined per unit values serve to assist in …

## Electricity Tariffs Explained | Residential and Industrial Tariff

As is the case with many English words, the word “tariff” has more than one definition. A common definition is a tax imposed on imported goods. The second definition is the rate structure charged by a party for services or goods. This second definition is used by many utilities in …

## Protective Relaying Principles and Applications

The applications of the different types of protection systems for the protection of various types of equipment and transmission lines are described in this section. These discussions are confined to protection for the high-voltage, bulk-power system components. Generator Protection The protection system provided to the synchronous generator must be able …

## Swing Equation in Power System

Swing Equation The motion of a synchronous machine is governed by Newton’s law of rotation, which states that the product of the moment of inertia times the angular acceleration is equal to the net accelerating torque. Mathematically, this may be expressed as follows: \$\begin{matrix}   J\alpha ={{T}_{a}}={{T}_{m}}-{{T}_{e}} & {} & \left( …

## Transient Stability in Power System

Power system stability refers to the ability of the various synchronous machines in the system to remain in synchronism or stay in step, with each other following a disturbance. Stability may be classified as steady-state, dynamic, or transient stability. Steady-state stability refers to the ability of the various machines to …

## Types of Protective Relays

The protective relay is the device that responds to signals from the transducers by quickly initiating or allowing a control action to be implemented in order to prevent damage to the faulted equipment and to restore service as soon as possible. The operating characteristics of the more commonly used protective …

## Power System Protection Components

The operation of a power system is affected by disturbances that could be due to natural occurrences such as lightning, wind, trees, animals, and human errors or accidents. These disturbances could lead to abnormal system conditions such as short circuits, overloads, and open circuits. Short circuits, which are also referred …

## Types of Faults in Power System | Unsymmetrical Faults in Power System

The normal operation of the power system at steady state is affected, sometimes dramatically, by the occurrence of such disturbances as overloads and short circuits. Of primary concern are short circuits, not only because they can cause large damage to the affected system component but also because they may lead …

## Symmetrical Components in Power System

The method of symmetrical components is used to solve power system problems involving unbalanced polyphase voltages and currents. It is analogous to the Fourier analysis of nonsinusoidal wave shapes wherein a non-sine wave is resolved into a number of sine waves of various frequencies. In symmetrical components, the unbalanced set …