## Harmonic Restraining in Differential Protection

In this post we will discuss about the feature of Harmonic Restraining feature of Differential Protection. First we should know why Harmonic Restraining is needed? Suppose we are going to energize the Transformer, obviously the Transformer will have an Inrush current which is around 6...

## Percentage Differential Protection – Slope in Differential Protection

As discussed in the post “Transformer Differential Protection”, differential protection is supposed to operate for the internal faults or for the zone of protection it is intended for. Differential protection is not supposed to operate for a through fault. Through fault means a fault outside...

## Basic Criteria for Selection of 33 kV/ 11 kV Or 66kV/11kV Substation

Basically 33 kV / 11 kV is used for distribution of power at the substation and 66 kV / 11 kV is also used for the distribution. But whether to use 66/11 kV or 33/11 kV depends on many factors. Following are some of the...

Harmonic voltages and currents in a Power System are a result of non-linear electric loads. In a normal AC Power System, the current varies sinusoidally at a specific frequency, usually 50 or 60 Hertz. When a linear electrical load is connected to the system, it draws...

## Dynamic Braking and Plugging

Dynamic Braking: Apart from Regenerative Braking, another method of reversing the direction of torque and Braking the motor is dynamic braking. In this method of braking the motor which is at a running condition is disconnected from the source and connected across a resistance. When...

## Regenerative Braking

In the last post “Need for Electrical Braking in Electrical Drives“, we discussed the various reasons which call for Electric Braking. Brakes are used to reduce or cease the speed of motors. Braking of Motor can be classified into three types: Regenerative Braking. Plugging type...

## Need for Electrical Braking in Electrical Drives

There are two types of Braking: i)     Mechanical Braking and  ii)     Electrical Braking. In Mechanical Braking the speed of the machine is reduced solely by mechanical process but Electrical Braking is far more interesting than that because the whole process is depended on the current and...

## What will happen if DC Motor run at a Higher RPM than the Rated RPM?

This may come in our mind that what exactly will happen if we operate a DC Motor at a speed more than the rated speed. In fact, the thermal capacity of the motor decides at what speed it can run and for how long. There...