## Programmable Scheme Logic (PSL) in Numerical Relays

Programmable Scheme Logic or PSL is a kind of feature provided in Numerical Relays to implement the protection scheme of a particular type. This feature of Numerical Relays makes it easier to implement many protection schemes in a single Numerical Relay for example, in Distance...

## Events resulting into Magnetizing Inrush Currents – Study of Sympathetic Inrush

I would suggest to read Transformer Inrush Current before reading this article for better understanding. Any event on the power system that causes a significant increase in the magnetizing voltage of the transformer core results in magnetizing inrush current flowing into the transformer. The three...

## Calculation of Stabilizing Resistor in High Impedance Differential Protection

Before going into the calculation part of Stabilizing Resistor, I will first explain the purpose of Stabilizing Resistor in High Impedance Differential Protection. Stabilizing Resistor in High Impedance Differential Protection is used to prevent the operation of Relay in case of through fault. Through fault...

## Concept of Subtransient, Transient & Steady State

The concept of Subtransient, Transient and Steady State arises in case of fault in an Alternator. Let us assume a sudden short circuit in three phase of alternator. The fault current will flow in all the three phases of alternator and its waveform will be...

## Types of Relay Output Contact

We know that 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...

## Philosophy of Primary and Back-up Protection

The protection provided by the protective relaying equipment can be categorized into two types as: a) Primary protection b) Back-up protection The primary protection is the first line of defense and is responsible to protect all the power system elements from all the types of faults. The...

## Unit and Non-Unit Protection Scheme

Protection schemes can be divided into two major groupings: a)    Unit schemes b)    Non-unit schemes a) Unit Protection Scheme: Unit type schemes protect a specific area of the system i.e. a transformer, transmission line, generator or bus bar. The unit protection schemes are based on...

## Zones of Protection and Dead or Blind Zone in Power System

Zoning in Power system Protection is an important philosophy and must be done carefully so that no part of the system remains unprotected in any condition. To limit the extent of the power system that is disconnected when a fault occurs, protection is arranged in...