Clik here to view.
Five protection relay types used to detect grid disturbances and isolating
System protection relays Consider a medium voltage distribution system having local generation (e.g., captive power generation) as shown in figure. Read more
View ArticleClik here to view.
Wiring of power factor relay on LV and MV side (circuit diagrams)
Circuit diagram of PF relay In order to measure electrical power the relay needs to receive the line voltage and current from a current transformer (CT) installed close to the metering point, if...
View ArticleClik here to view.
Two main functions of an earth electrode and its installation parameters
To protect persons and LV instalations The prime function of an earth electrode is the protection of persons. That’s it. It is a fact that we live on Earth! And it is vital to earth. Read more
View ArticleClik here to view.
How good are you at reading electrical drawings? Take the quiz.
Electrical working drawings Every electrician, in every branch of electrical work, will need to consult and understand the information presented on electrical drawings to locate the various outlets,...
View ArticleClik here to view.
Three main techniques for mitigating step and touch potential hazards
Danger of ground potential rise Mitigating step and touch potential hazards is usually accomplished through one or more of the following three main techniques. Reduction in the resistance to ground...
View ArticleClik here to view.
8 essential relay operating principles of catching faults
Detection of Faults In general, as faults (short circuits) occur, currents increase in magnitude, and voltages go down. Besides these magnitude changes of the AC quantities, other changes may occur in...
View ArticleClik here to view.
Six network operating conditions under which ferroresonance can occur
Ferroresonance and its causes Due to the multitude of various sources of capacitances and non-linear inductances in a real power network and the wide range of operating conditions, configurations under...
View ArticleClik here to view.
Circuit breaker selections for low voltage installation (with discrimination)
LV installation The LV installation which forms the subject of this study is shown in figure 1 above. This study includes discrimination and coordination of protection between the LV equipment and the...
View ArticleClik here to view.
Thumb rules for surge arrester installation in different earthing systems
Installation rules for LV surge arresters A variety of documents deal with the subject of surge arrester installation: for example in France, standard NF C 15-531 focuses on the installation rules of...
View ArticleClik here to view.
Rules for dimensioning, disconnecting and protecting the neutral conductor
Contents Dimensioning of neutral conductor Smaller than the cross-sectional area of the phase conductors… Equal to the cross-sectional area of the phase conductors Greater than or equal… Neutral...
View ArticleClik here to view.
Network harmonics analysis – Installation with 6-pulse rectifier, capacitors...
Injecting a harmonics with 6-pulse rectifier The diagram in figure 1 represents a simplified network comprising a 2,000 kVA six-pulse rectifier, injecting a harmonic current spectrum, and the following...
View ArticleClik here to view.
The most frequent errors in specifying current transformers (CTs)
Proper specification of CTs Current transformers (CTs) form an essential link within the protection chain of electrical networks. Their specification, even if it is handled by specialists, often...
View ArticleClik here to view.
Typical power supply schemes for standby and production generator sets
Turbines and diesel engines The main types of prime movers used in engine driven generator sets for industrial sites and commercial buildings are Diesel engines, gas turbines, and steam turbines....
View ArticleClik here to view.
Why and where do internal faults happen in substation transformers
Progression of internal faults Transformers are subjected to many external electrical stresses from both upstream and downstream that can lead directly to internal fault(s). The consequences of any...
View ArticleClik here to view.
Protection of capacitor banks by fuses (during energization and operation)
Stress specific to the protection of capacitor banks by fuses, which is addressed in IEC 60549, can be divided into two types: Stress during bank energization (the inrush current, which is very high,...
View ArticleClik here to view.
The attached rod technique – better than fall-of-potential ground testing method
Fall-of-potential testing is extremely reliable, highly accurate, conforms to IEEE 81 and gives the operator complete control over the set-up. Unfortunately, it is exceedingly time consuming and labor...
View ArticleClik here to view.
Dangerous magnetic field exposure near transformer substation in the building
Transformer substations located close to the living areas could induce high long-term exposures to extremely low frequency magnetic fields of nearby inhabitants. Some of the researches have shown...
View ArticleClik here to view.
Sizing calculations for 20/3.3 kV, 12.5 MVA transformer feeder cable
Typical calculations for a 20kV transformer feeder cable are presented below. After correct cable voltage classification the following considerations apply: Current carrying capacity Short circuit...
View ArticleClik here to view.
How to recognize harmonics symptoms – What to look for and where to look?
Finding harmonics problem is relatively easy once you know what to look for and where to look. Harmonics symptoms are usually anything but subtle. This technical article provides some basic pointers on...
View ArticleClik here to view.
Current sensors as the eyes of RCD and tips for their correct installation
All residual current devices are made up of at least two components. First component act as the eyes of RCD – sensors – must be able to supply an electrical signal which is useful when... Read more
View Article