Protection
Primary injection testing of protection system for wiring errors between VTs / CTs and relays
This type of test involves the entire circuit – current transformer primary and secondary windings, relay coils, trip and alarm circuits, and all intervening wiring are checked. There is no need to disturb wiring, which obviates the hazard of open-circuiting… Read more
Dec 13, 2017 | By Edvard Csanyi
Electric Motor
Ten different duty types (load cycle) of a three-phase asynchronous motor
The term duty defines the load cycle to which the machine is subjected, including, if applicable, starting, electric braking, no-load, and rest de-energized periods, and including their durations and sequence in time. Duty considered as a generic term, for example,… Read more
Dec 11, 2017 | By Edvard Csanyi
Energy and Power
Seven Bad Effects Of Corona On Transmission Lines
All the diverse ionization processes involved in producing corona discharges in the highly stressed regions near the conductors of transmission lines, as well as the creation and movement of charged particles in the electric field, require an expenditure of energy…. Read more
Dec 08, 2017 | By Edvard Csanyi
Transformers
Voltage Regulation By Transformer Off-Load Tap Changer, On-Load Tap Changer and AVR
Almost all transformers incorporate some means of adjusting their voltage ratio, by adding or removing tapping turns. This adjustment may be made by an on-load tap-changer, or by means of an off-circuit tap-changer, or by the selection of bolted link… Read more
Dec 06, 2017 | By Edvard Csanyi
Energy and Power
Protections For Medium Voltage Synchronous Machines (Generators) – IEEE C37-2 Codes
The protection system for MV generators (synchronous machines) must be carefully selected and studied for the application it is destined for and it is not normally possible to define a single solution. Only medium voltage generators are analysed and large… Read more
Dec 04, 2017 | By Edvard Csanyi
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How Bad Harmonics Influence The Work Of Rotating Machines (Induction Motors)
The presence of harmonics in the work of induction motors can be pretty bad. Why? They produce elastic deformation, that is, shaft deflection, parasitic torques, vibration noise, additional heating, and lower the efficiency of rotating machines. The movement of the…...
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Dec 01, 2017 | By Edvard Csanyi
Transformers
Voltage Regulators Used To Control The Voltage At The End Of a Distribution Feeder
There are three main methods used to control the voltage at the end of a distribution feeder – By using control equipment to vary the voltage at the supply end of the feeder or at the load end and by… Read more
Dec 01, 2017 | By Edvard Csanyi
Electrical Lectures
Current Systems (AC/DC) And Voltage Levels Basics You Must Never Forget
There are many electrical engineering basics you really must know at any time, even in the middle of the night! The basics we will discuss here are current systems and voltage levels in transmission and distribution systems. Contents: Current Systems… Read more
Nov 29, 2017 | By Edvard Csanyi
Transformers
How To Choose System’s Earthing Point And What Is The Practice Throughout The World
Normally in directly earthed and effectively earthed systems, every available neutral point is earthed. Deviations from this occur when the transformer’s neutral points are left unearthed. This is done to limit the maximum earth fault current which can arise to… Read more
Nov 27, 2017 | By Edvard Csanyi
Protection
Secondary injection tests for checking the correct operation of the protection scheme
Secondary injection tests are always done prior to primary injection tests. The purpose of secondary injection testing is to prove the correct operation of the protection scheme that is downstream from the inputs to the protection relay(s). Why done prior… Read more
Nov 22, 2017 | By Edvard Csanyi
Protection
Differential Protection Of Feeders For Transformers And Tee-Offs (Tapped Lines)
On transformer feeders, the transformer and line or cable are connected in series and form a unit. In this manner, one CB can be saved. On feeders with tee-offs, transformers along the feeder are directly connected. In this case, a… Read more
Nov 20, 2017 | By Edvard Csanyi
Energy and Power
How To Control Reactive Power In Larger Electrical Plants With Multiple Incomers
Most compensation banks are controlled stepwise. For this purpose it is essential to ‘know’ when it is allowed to (de)activate a capacitor step by the power factor relay (controller). The so-called C/k value is calculated by the step size C… Read more
Nov 15, 2017 | By Edvard Csanyi
Cables
Overhead vs. Underground Residential Distribution Circuits. Which One Is ‘Better’?
This debate continues. Both designs have advantages (see Table 1). The major advantage of overhead circuits is cost. An underground circuit typically costs anywhere from 1 to 2.5 times the equivalent overhead circuit (see Table 2). But the cost differences… Read more
Nov 13, 2017 | By Edvard Csanyi
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We can load distribution transformer heavily when it is cold, but when it’s hot…
Distribution transformers (commonly mineral-oil-immersed type) are output rated and their loading and sizing guidelines of many utilities are based on ANSI/IEEE C57.91. Distribution transformers can deliver their rated kVA without exceeding temperature rise limits when the following conditions apply: The…...
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This content is not available in your premium membership plan. Please upgrade your plan in order to access this content. You can choose an annually based Basic, Pro, or Enterprise membership plan. Subscribe and enjoy studying specialized technical articles, online video courses, electrical engineering guides, and papers.With EEP's premium membership, you get additional essence that enhances your knowledge and experience in low- medium- and high-voltage engineering fields.
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Nov 09, 2017 | By Edvard Csanyi
Electric Motor
Practical Basics Of Synchronous Motors That Every Electrical Engineer Should Know
Like the asynchronous motor, the synchronous motor consists of a stator and a rotor separated by the air gap. It differs from the asynchronous motor in that the flux in the air gap is not due to a component of… Read more
Nov 08, 2017 | By Edvard Csanyi
