# Power Systems

## Critical Clearing Angle

The critical clearing angle is defined as the maximum change in the load angle curve before clearing the fault without loss of synchronism. In other words, when the fault occurs in the system the load angle curve begin to increase, and the system becomes unstable. The angle at which the fault becomes clear and the …

## Equal Area Criterion

The equal area criterion is a simple graphical method for concluding the transient stability of two-machine systems or a single machine against an infinite bus. This principle does not require the swing equation for the determination of stability conditions. The stability conditions are recognized by equating the areas of segments on the power angle diagram …

## Classification of Substations

The substation is the medium of transferring the power from generating unit to the consumer end. It consists different types of equipment like transformer, generator, power cable which helps in the power transmission. The generation, transmission and distribution are the main work of the substation. The substation which generates the power is known as the …

## Step & Touch Potential

When a fault occurs, the fault current flow to the ground due to which the potential gradient near the electrical equipment developed. This potential gradient may affect a person in two ways, either by step-to-step contact or by touch contact. Step-Potential – Step potential is the potential difference between the feet of a person standing on …

## Static VAR Compensator

A static VAR compensator is a parallel combination of controlled reactor and fixed shunt capacitor shown in the figure below. The thyristor switch assembly in the SVC controls the reactor. The firing angle of the thyristor controls the voltage across the inductor and thus the current flowing through the inductor. In this way, the reactive …

## Thyristor Controlled Reactor & Thyristor Switched Capacitor

Thyristor Controlled Reactor Thyristor controlled reactor consist reactor L placed in series with the thyristor valve. This reactor is the controlled element of the TCR, and it controls the thyristor valve. TCR consists two opposite poled thyristor which conducts every alternate half cycles of the supply. In TCR the duration of current flowing through the …

The potential gradient in a power system is defined as the rate of change of electric potential with respect to the distance from the base of the electrical structure. The resistance of the earth electrode is not concentrated at one point, but it is distributed over the soil around the electrode. When a fault current …

## Symmetrical Components

When the system is unbalanced the voltages, currents and the phase impedances are in general unequal. Such a system can be solved by a symmetrical per phase technique, known as the method of symmetrical components. This method is also called a three-component method. The method of symmetrical components simplified the problems of the unbalanced three-phase …

## Short Circuit Current

When two or more conductors of different phases come in contact with each other in a power line, power transformer or any other power element, then the part of the impedance is shunted out of the circuit due to which a large current flow in the un-faulted phases, such current is called the short circuit …

## Peterson Coil Grounding

Peterson coil is an iron core reactor connected between transformer neutral and ground. It is used for limiting the capacitance earth fault current which is flowing when the line ground fault occurs in the line. The coil is provided with the tapping so that it can be adjusted with the capacitance of the system. The …