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The following earthing terms are defined according to NEC standard (National Electrical Code) which is a foundational pillar of NFPA 70 (National Fire Protection Authority). Having a good understanding of the terms used within Article 250 of NEC is critical to understanding the grounding and bonding requirements within the NEC. The following definitions are commonly used throughout Article 250, and knowing them is essential to installing an effectively grounded and bonded electrical system. Ground - The earth Grounded (Grounding) - Connected (connecting) to the ground or to a conductive body that extends the ground connection. An example of a conductive body that extends the ground connection is the first 5 feet of a water pipe entering a building. It is permitted to connect at this point even though it is not a grounding electrode, as the first 5 feet of the pipe are not physically in contact with the earth. Grounded Conductor - A system or circuit conductor that is intentionally gr...

The type of protection available for a given transformer depends on the size, complexity, and revenue derived there from it. For these reasons, different protection schemes are employed for power and distribution transformers. The type of protection used should minimize the time of disconnection for faults within the transformer and reduce the risk of catastrophic failure. Any extended operation of the transformer under abnormal conditions such as faults or overloads compromises the transformer's life. This implies that the speed of isolation upon a fault is essential. Causes of Transformer Failure Transformers throughout the power system, experience different levels of through-fault currents in terms of magnitude, duration, and frequency.  Through-faults in transformers can produce physical forces that cause insulation wear and friction-induced displacement in the winding. These effects are cumulative and should be considered over the life of the transformer. Classification of Fai...

 The selection of a current transformer is a simple task. There are four phases in the selection procedure -  1. Define customer requirements: Based on the primary circuit and the metering and protection chains 2. Select from the catalog of the reference CT's the most suitable unit for the customer's need 3. If not selected from the general catalogs - the standardized CT are the most suitable unit for the customer's need 4. If none are feasible ask for feasibility studies - However, even if the special unit can be manufactured, it will nevertheless be a special make-up with all the problems which may endanger lives Download the PDF file below -  Current Transformer Selection Guide - PDF download

 As session begins in most Nigerian university, polytechnics and colleges of education. It is thus advisable for students to keep there self updated and alert for urgent tests and exam as might be decided by the lecturer.  UNESCO in a brief UNESCO is responsible for coordinating international cooperation in education, science, culture and communication. It strengthens the ties between nations and societies, and mobilizes the wider public so that each child and citizen: • has access to quality education; a basic human right and an indispensable prerequisite for sustainable development; • may grow and live in a cultural environment rich in diversity and dialogue, where heritage serves as a bridge between generations and peoples; • can fully benefit from scientific advances; • and can enjoy full freedom of expression; the basis of democracy, development and human dignity. UNESCO's messages are of increasing importance today, in a globalized world where interconnections and divers...

 As session begins in most Nigerian university, polytechnics and colleges of education. It is thus advisable for students to keep there self updated and alert for urgent tests and exam as might be decided by the lecturer.  UNESCO in a brief UNESCO is responsible for coordinating international cooperation in education, science, culture and communication. It strengthens the ties between nations and societies, and mobilizes the wider public so that each child and citizen: • has access to quality education; a basic human right and an indispensable prerequisite for sustainable development; • may grow and live in a cultural environment rich in diversity and dialogue, where heritage serves as a bridge between generations and peoples; • can fully benefit from scientific advances; • and can enjoy full freedom of expression; the basis of democracy, development and human dignity. UNESCO's messages are of increasing importance today, in a globalized world where interconnections and divers...

Most industrial types of equipment are inductive loads hence, they required two kinds of power been consumed by them ( kW - to perform the actual work and kVAR - reactive power to sustain the magnetic field of the load ). Example of inductive load - Electric motors, Induction furnaces, Lighting ballasts, etc basically loads with the composition of coils for their design. While kW is the useful power required to keep the machine running. The kVAR basically does not perform any useful work except to help to sustain the magnetic field in the equipment. For example - if you had an electric motor that was operating at 100kW and the apparent power was 125kVA. Hence, power factor will be 0.8 (kW/kVA = 100/125 = 0.8pf). This means kVA decreases if pf increases. As an example - A 100kW load operating at 142kVA will have 0.7pf (70% efficient) and at 105kVA the pf will be 0.95(95%). This means the more you correct your pf the lesser the kVA that will be consumed and the lesser the utility you ar...

Sensors One type of feedback frequently needed by industrial-control systems is the position of one or more components of the operation being controlled. Sensors are devices used to provide information on the presence or absence of an object. Types of Sensors The following are the types of sensors used in industrial automation: 1. Photoelectric sensor 2. Inductive sensor 3. Capacitive sensor 4. Ultrasonic sensor 5. Temperature sensor 1. Photoelectric sensor -  Photoelectric sensors detect objects, changes in surface conditions, and other items through a variety of optical properties. A photoelectric sensor consists primarily of an emitter for emitting light and a receiver for receiving light. When emitted light is interrupted or reflected by the sensing object, it changes the amount of light that arrives at the receiver. The receiver detects this change and converts it to an electrical output. The light source for the majority of photoelectric sensors is infrared or visible light (...