Category Archive for: «Protection»

Features of 3 circuit protection devices (MCB, RCCB and RCBO) you have probably forgotten

Circuit Protection Devices Traditionally, fuses were the main devices chosen for final circuit protection, up until the 1970’s when circuit breaker technology started to become dominant. Today, the three principle circuit protection devices are: Miniature Circuit Breakers (MCBs), Residual Current Circuit Breakers (RCCBs) and Residual Current Circuit Breakers with Overcurrent protection (RCBOs) Miniature Circuit Breakers […]

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What Would Be The Worst Type Of Three Phase Faults (And Why It Happens)

When Three Phase Faults Occur… In a three phase power system, the type of faults that can occur are classified by the combination of conductors or buses that are faulted together. In addition, faults may be classified as either bolted faults or faults that occur through some impedance such as an arc. Each of the basic […]

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5 anomalies in AC power that can damage your home devices

AC Power Fluctuations In addition to lightning, there are a number of other disturbances that can come in on the AC power lines and damage equipment. Some surge protectors can reduce or eliminate damage from some of these perturbations. There is considerable confusion about the overlap between damage from AC power disturbances and from lightning. […]

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3 Main causes of false differential current in transformer

Differential current // Certain phenomena can cause a substantial differential current to flow, when there is no fault, and these differential currents are generally sufficient to cause a percentage differential relay to trip. However, in these situations, the differential protection should not disconnect the system because it is not a transformer internal fault. Such phenomena can be […]

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The Basics Of Molded Case Circuit Breakers You MUST Know

Molded Case Circuit Breakers (MCCB) // Molded case circuit breakers are interrupting devices with self-contained, current-responsive elements. These breakers are assembled as an integral unit in a supported and enclosed housing of insulating material. Depending on the amount of protection required, these breakers can sense internally and then clear undervoltage, overcurrent, and short circuit conditions. […]

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5 Means Of Identifying Grounded Conductors (By NEC 200 Article)

Determining grounded conductors // NEC 200 Latest NEC requirements state at least five means of identifying grounded conductors. So, let’s go through each of them // Sizes 6 AWG or smaller Sizes 4 AWG or larger Flexible cords Grounded conductors of different systems Grounded conductors of multiconductor cables 1. Sizes 6 AWG or Smaller An […]

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Arc Flash Hazard Calculation In 9 Steps Using IEEE 1584

Arc Flash Hazard – Safe practices The Institute of Electrical and Electronic Engineers (IEEE) published the IEEE 1584 “Guide for Performing Arc Flash Hazard Calculations”. It contains detailed methods and data that can be used to calculate arc flash hazards for the simplest to the most complex systems. IEEE spent many years developing these methods. […]

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Where Do Electrical Faults Occur The Most?

Causes of electrical faults // A fault is not a natural occurrence. It is an unplanned event which occurs unexpectedly. Electrical faults in an electrical installation or piece of equipment may be caused by // Negligence – that is, lack of proper care and attention Misuse – that is, not using the equipment properly or correctly […]

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Important points about grounding of electronic equipment

Safety grounding // Grounding electronic equipment for personal safety and clearing of faults is no different than that of any other equipment. Safe grounding requires fast opening of circuit breakers or fuses and minimization of voltage differences between exposed metal surfaces on all of the involved electrical system and equipment, to levels that are safe […]

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Measurement of residual currents on a distribution feeder

Residual currents (earth fault) The measurement of the earth fault or residual currents on a distribution system feeder can be done by the so-called summation connection, where the three current transformers, one in every phase, are connected and the summated current is brought to the inputs of an earth fault protection relay. This is a […]

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