Clik here to view.
Applications and Characteristics Of Overcurrent Relays (ANSI 50, 51)
Applications and Characteristics Of Overcurrent Relays (ANSI 50, 51)50/51 and 50/51N relaysOvercurrent relays are the most commonly-used protective relay type. Time-overcurrent relays are available...
View ArticleClik here to view.
Let’s analyse phase-to-earth faults in a single-incomer power system
Let’s analyse phase-to-earth faults in a single-incomer power systemDetect and isolate…Power-system protection should detect faults and isolate the faulty parts of the power system while keeping the...
View ArticleClik here to view.
Electrical life (durability) of LV circuit breakers due to the switching...
Electrical life (durability) of LV circuit breakers due to the switching operations (photo credit: unilec.net)Test requirementsAccording to the standard IEC 947-2, there is actually no defined...
View ArticleClik here to view.
An Example Of Transformer Overload and Short-Circuit Protection
An Example Of Transformer Overload and Short-Circuit Protection (photo credit: ABB; Mariano Berrogain)NEC Article 450 // Transformers VaultsTransformer protection consists of both overload protection...
View ArticleClik here to view.
Miniature Circuit Breakers (MCBs) For Beginners
Miniature Circuit Breakers (MCBs) For BeginnersDual functions of a switch and a fuseThis technical article focuses on the widely used miniature circuit breakers rated for 240 V or less. These are...
View ArticleClik here to view.
A real life analogy of the jurisdiction of the protection relay
An Example of Relay Used To Protect the Transmission Line Under Fault (For Beginners)To Protect the Transmission Line Under FaultFormally, a relay is a logical element which processes the inputs...
View ArticleClik here to view.
Ring Main Unit (RMU) as an important part of secondary distribution substations
Ring Main Unit as an important part of Secondary Distribution Substations (on photo: ABB’a 24kV RMU type ‘SafeRing’)RMUA Ring Main Unit (RMU) is a totally sealed, gas-insulated compact switchgear unit....
View ArticleClik here to view.
Maintenance and testing of the overcurrent protective devices
Maintenance and testing of the overcurrent protective devices (on photo: SIEMENS’s new 3VA2 molded case ciruit breaker up to 630 A, ETU, 400/690 V, up to 150 kA)Electrical system reliabilityWhen...
View ArticleClik here to view.
3 Overcurrent Protective Device Ratings You Must Properly Select
3 Overcurrent Protective Device Ratings You Must Properly Select (on photo: Schneider Electric’s ACB Masterpact 1600A; credit: elektro-celik.hr)Ampere, voltage and interrupting ratingIn order for an...
View ArticleClik here to view.
Selective Coordination with Circuit Breakers
Selective Coordination with Circuit Breakers (photo credit: enerprom.si)Introduction to Selective CoordinationSelective coordination is often referred to simply as coordination. Coordination is defined...
View ArticleClik here to view.
Example for Coordination of Cascaded Circuit Breakers
Inputs for Coordination CalculationA 440 V 60 Hz switchboard feeds a 4-wire distribution board for small loads such as socket outlets. The switchboard has a fault making capacity of 100kA rms. After...
View ArticleClik here to view.
Things About MCBs That Every Low Voltage Electrician Should Know
MCB Operation and characteristicsAn MCB is a thermo-magnetic device, meaning that it has two methods of circuit interruption. A thermal mechanism, usually a bi-metallic strip, provides protection...
View ArticleClik here to view.
Voltage Drop Calculations For Engineers – Beginners
Voltage drop formulas //Voltage drop calculations using the DC-resistance formula are not always accurate for AC circuits, especially for those with a less-than-unity power factor or for those that use...
View ArticleClik here to view.
8 Schemes To Supply MV Switchboard
MV switchboard supply solutions // Medium voltage networks are made up of switchboards and the connections feeding them. Let’s take a look at the eight different supply modes of these medium voltage...
View ArticleClik here to view.
Automatic Transfer System Explained in Details (Part 1)
The Role of the Automatic Transfer System Using the basic building blocks of utility power, system topology, on-site generation, and uninterruptible power supplies, the basic role of the automatic...
View ArticleClik here to view.
Automatic Transfer System Explained in Details (Part 2)
Continued from first part – Automatic Transfer System (ATS) in Details – 1 ATS operational requirements // In previous article I explained the role of the automatic transfer system and the operational...
View ArticleClik here to view.
7 Guidelines To Select Correctly Rated Circuit Breaker
Selection of rated circuit breaker // The general procedure for the selection of correctly rated circuit breaker follows the following scheme of seven major questions you should answer: What is the...
View ArticleClik here to view.
The Design Basics Of Motor Protection Circuit Breaker
Motor protection circuit breaker (MPCB) // Application-specific variations of the MCCB, these breakers combine the short-circuit and isolation functionality of the MCCB with the motor overcurrent...
View ArticleClik here to view.
Learn To Interpret Single Line Diagram (SLD)
Single line diagram (SLD) We usually depict the electrical distribution system by a graphic representation called a single line diagram (SLD). A single line can show all or part of a system. It is very...
View ArticleClik here to view.
The Basics Of Circuit Breaker Tripping Units
Circuit breaker releases / Tripping units The main objective of circuit breaker tripping units and protective functions in general is to detect faults and to selectively isolate faulted parts of the...
View Article