Electrical Substation

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Electrical substation for distribution system is the main supply to convert the high voltage (HV) to low voltage (LV) and the place where load are distributed to the consumers. In Malaysia, Tenaga Nasional Berhad Distribution (TNBD) used the
33/0.433kV, 22/0.433kV, 11/0.433kV and 6.6/0.433kV voltage system for the electrical system to supply for domestic consumer and industrial consumer such as factory which will supplied directly from Transmission Main Intakes (PMU), Main Distribution Sub –station (PPU) or Main Switch Sub – station (SSU).
Electrical substation is the place where all electrical equipments such as high voltage switching, three phase transformer, high voltage cables, low voltage cables, low voltage feeder
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II. Gas
Gas (SF6) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the SF6 to quench the stretched arc. III. Vacuum
Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material), so the arc quenches when it is stretched to a very small amount (<2–3 mm). At or near current zero the arc is not hot enough to maintain a plasma, and current ceases; the gap can then withstand the rise of voltage. Vacuum circuit breakers are frequently used in modern medium-voltage switchgear to 35,000 volts. Unlike the other types, they are inherently unsuitable for interrupting DC faults.

Maintenance 1) Visual Maintenance * To observe the switchgear to check any physical damage. 2) Insulation Test * Should be less then 40 Ω with insulation resistance more than 100MΩ. 3) Change of oil. * The oil in the switch gear tank need to be replaced in a period of time as it will become dirtier.

5.2 Transformer
A transformer is a power converter that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a
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