Calculating Flash Protection Boundary Distances
In NFPA 70E, the short-circuit symmetrical ampacity from a bolted 3-phase fault at the transformer terminals is calculated with the following formula:
[pmath]I_{sc} = {{MVA_{Base} * 10^6} / {sqrt{3}*V}} * {100 / %Z}[/pmath]
where
Isc = Amperes,
V = Volts,
%Z = transformer MVA.
A typical value for the maximum power (in MW) in a 3-phase arc can be calculated using the...
Philippines Economic Outlook 2020 and Overseas Filipino Workers
The economy of the Philippines based on Economic Forecasts - 2019-2021 Outlook indicate an levelled economy relative to 2019. Trade deficit will increase by 25%. Foreign exchange rate will increase by about 2.5%.
The weakening of the Philippine Peso (PhP) means that the Overseas Filipino Workers (OFW) will have a bit of advantage this year. This...
Effects of harmonics on Electrical Equipment
Harmonic distort the fundamental frequency of the mains voltage waveform which affects the performance of other electrical equipment and creates additional losses and heating.
A total harmonic voltage distortion of 2.5% can cause an additional temperature rise of 4 deg.C in induction motors. In cases where resonance can occur between the system capacitance and reactance at harmonic frequencies, voltage distortion...
Resistance of a Single Earth Electrode
The resistance of a single earth can be calculated if the soil resistivity is known. An earth rod driven vertically, the electrode resistance can be calculated using the following formula.
where:
R = electrode resistance, Ω
ρ = Soil resistivity, Ω-m
L = Length of electrode buried... 
Greenfield and Brownfield Projects
People who have been involved in project implementation may know what "Greenfield" and "Brownfield" projects mean.
Prior to being employed by EPCM companies, I never knew what these terms mean. Being a farm kid, the greenfield I knew was totally different from the greenfield I currently know.
In project terms, the meaning of these terms are
Greenfield Project - A project...
