Instrument Safety Factor or Instrument Security Factor (ISF)

ISF (Instrument Security Factor)

An ammeter is connected in the secondary circuit of a current transformer. The ammeter measures the current through the primary of the current transformer. Impact of Fault Current on Secondary Current Now, suppose a fault occurs in the system. Consequently, a large fault current starts flowing through the primary of the current transformer. If the fault current … Read more

What is Accuracy Limit Factor of CT? Complete Details

ALF (Accuracy Limit Factor)

Current transformers (CTs) play a crucial role in power systems, especially in protection and metering applications. The Accuracy Limit Factor (ALF) is one of the key parameters that determines the performance of current transformers. This article provides an in-depth understanding of the ALF. The article covers its significance and its impact on the reliable operation … Read more

Rated Short Circuit Making Current and Breaking Current 

Definition of Making Current The rated short circuit making current of a circuit breaker is the maximum peak current that the circuit breaker can close without any damage. It is the maximum peak current that a circuit breaker can make safely.  Definition of Breaking Current The rated short circuit breaking current, on the other hand, … Read more

Zero Current Crossing Method in A Circuit Breaker

This zero current crossing method is only applicable to alternating current circuit breaker. We all know that an alternating current naturally passes through zero at regular intervals (every half-cycle of the AC waveform). This method safely interrupts the alternating current at the natural zero-crossing of its waveform. Working Principle of a CB based on Zero … Read more

Small Inductive Current Interruption by Circuit Breakers

Normal Short Circuit Rating of Circuit Breaker Engineers design high voltage circuit breakers to handle very high short-circuit currents. Manufacturers build these breakers to interrupt extremely high fault levels effectively. They typically rate circuit breakers for short-circuit breaking capacities such as 25kA, 31.5kA, 40kA, or even 50kA and more. Such ratings define their ability to … Read more

GAP-Type HTLS Conductors

A Gap-type HTLS conductor is a special type HTLS conductor. It exhibits a separate high strength low elongation steel core surrounded by layers of thermal resistant aluminum alloy strands. The typicality of a gap type HTLS conductor is, it maintains a deliberate annular gap between the core and the first layer of aluminum alloy strands. … Read more

Insulators Used in Overhead Transmission Lines

Insulators Used in Overhead Transmission Lines In overhead transmission lines, insulators support the conductor on metallic tower structures. At the same time, they electrically isolate the high-voltage conductor from the metallic body of the supporting towers. In high-voltage overhead transmission lines, engineers typically install insulator strings at the tip of the cross arms of towers. … Read more

Local Breaker Backup (LBB) Protection – Explained

What is LBB Protection? Local Breaker Backup (LBB) Protection is a special protection scheme. This protection isolates a fault from the electrical power system when a circuit breaker fails to do so. When a fault occurs at a particular point in a power system, the primary protection relay associated with that part of the system detects … Read more

CT Saturation and its Causes & Effects – A Complete Guide

Current transformers (CTs) play a critical role in protection and metering. The proper operation of protection relays depends on CT accuracy to detect faults. Additionally, the accuracy of CT is more important for metering purposes. However, when a CT experiences core saturation, its secondary output no longer represents the true replica of the primary current. … Read more