Tricky but Easy Electrical Engineering!
Most of us are aware of Electromagnetic Relays and Static Relays but most us may not be well acquainted with Numerical Relay. If I define a Numerical Relay, honestly speaking it will seem to be quite tough but in reality they are very user friendly and easy to implement different types of protection scheme. However … Read more
Relay is a switch which senses fault in a system and once fault is sensed by the Relay, it issues trip command to the Circuit Breaker, CB to isolate the faulty section of the network from the healthy section. The Relay detects the abnormal condition by continuously monitoring electrical quantities which are different for healthy … Read more
In earlier posts we discussed, Concept of Symmetrical Components and Calculation of Symmetrical Components. It is recommended to go through these topics before analyzing Single Line to Ground Fault. You must read, Concept of Symmetrical Components and Calculation of Symmetrical Components Let us consider a three phase system with earthed neutral as shown below. Let us … Read more
Electrical Faults can be classified into two categories: Shunt Faults and Series Faults. Shunt faults include power conductor or conductors to ground or short circuit between the conductors. Series type of fault is basically unbalance in system. Suppose we have used Fuse / Breaker to protect the circuit. If one or two phases open while … Read more
We are now aware of the concept of Sequence components of current / voltage. If you have miss this concept, please read Concept of Symmetrical Components. Now we are at a stage to calculate the zero, positive and negative sequence components of current / voltage. As already discussed any three phase unbalanced voltage / current can … Read more
Being an Electrical Engineer, it is very important to have clear concept of Symmetrical Components used for the analysis of fault or unbalance in a Power System. Basically Symmetrical Components are mathematical modeling used to simplify the calculation while maintain the physical significance of components. The concept of Symmetrical Components can be stated as: … Read more
Sensitive Earth fault Protection scheme is used for the detection of earth fault. Protection against phase to ground faults can be a difficult problem since ground fault currents vary within a large range, becoming almost negligible in some situations. The ground fault current magnitude depends on the power system grounding which can vary from solidly … Read more
Restricted Earth Fault (REF) protection is basically a Differential Protection. The only difference in between the Differential Protection and REF Protection is that, latter protection is more sensitive as compared to the former protection scheme. In earlier posts we have already discussed Differential Protection of Transformer and various characteristics of Differential Protection. In this post … Read more
SOTF Protection stands for Switch On to Fault. This protection is provided for high speed clearance of detected fault immediately after Manual Closure of Circuit Breaker. Let us suppose that a fault is existing and we gave a closing command to Breaker, then in that case SOTF protection will immediately trip the Breaker. SOTF Protection … Read more
The majority of faults on a power system occur between one phase and ground or two phases and ground. These are known as shunt faults and arise from lightning discharges and other over voltages which initiate flashovers. Alternatively, they may arise from other causes such as birds on overhead lines or mechanical damage to cables … Read more