ELECTRICAL SYSTEM STUDIES: Specification of Equipment for New Power Substations
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- Mar 27, 2020 9:01 pm GMT
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When a power utility or electrical system operator is setting the values of a future substation, the premise is meeting a need for power or energy traffic in a certain region. Several studies will be done to define the rated values of currents and voltages.
The main studies carried out to define the values of the substation are :
(a) load flow studies,
(b) short circuit studies and
(c) system stability studies.
Along the life of the electrical equipment within a substation, in addition to "normal" steady situations we have "abnormal" situations such as short circuits and overvoltages.
In normal situations, the currents and voltages are not significantly higher than the rated nominal values of the equipment. A device properly designed, if used within the nominal values, will have a normal aging and lifetime. An example is when the temperature rises of metal parts, fittings and insulation do not exceed the limits specified in technical standards, for temperature rise tests. On the contrary, if the voltages or current values exceed certain limits, the equipment is subjected to accelerated aging and failures.
The common abnormal situations are:
a) Short time overcurrents caused by short circuits(durations of the order of up to 3 s)
b) Long duration overcurrents caused by overloading(dozens of seconds or minutes).
c) Long duration overvoltages caused by disturbances in the electric system or by intentional operation to supply lower voltage levels in the end parts of the system(seconds or dozens of seconds)
d) Very short duration overvoltages (4 to 6 Un peak with durations of S) as impulse voltages
This article gives an overview about these studies. Here is the link for the complete article.