Per-unit system advantages: 

Circuits are simplified.

The per-unit values for various components lie within a narrow range regardless of the equipment rating

For example, voltages have the same range in per-unit in all parts of the system from EHV system to distribution and utilization.

When expressed in the per-unit, machines parameters usually fall in narrow range regardless of machines size.

For example, generator reactances in per unit are similar for both 100 MVA machines and 1000MVA machines. This facilitates data checking and hand calculations.

For circuits connected by the transformers, per- unit system is suitable. By choosing a suitable base kV for the circuits, the per-unit reactance remains the same referred to either side of the transformer. Therefore, the various circuits can be connected in the reactance diagram.

• Sqrt (3) factor in the three phase circuit calculations is eliminated.
• Per-unit (pu) system is ideal for computer simulations.

Powder coating is a method of coating a substrate in a polymer powder via directional spray equipment. The big difference between this and wet spraying is that the wet spray principle requires a carrier or solvent to allow the material to be successfully atomised and transferred from gun to the substrate, here the powder is carried out of the spray equipment with low pressure air and is drawn towards the substrate via an electrostatic charge which is induced at the exit of the spray equipment.

The powder is then cured via an oven to flow the powder out across the surface fusing the particles together in a chemical crosslink.

There are two types of powders used, Thermo plastic, which re-melts with any further application of heat and the more common Thermosetting powders which are much more widely used.

The Thermoset system are primarily composed of relatively high molecular weight solid resins of between 30 and 50 um in particle size and cure agent or catalyst which forms or assists in the formation of crosslink between the polymer chain to form a none reversible polymer film that will not re-melt if subjected to heat for a second time..

The primary resins used in the formulation of thermosetting powders are:

• Epoxy
• Polyester
• Polyester /Epoxy blends (known as Hybrids)
• Acrylic
• Polyurethane

There are many advantages that make the choice of applying thermosetting powder coatings so attractive;

• Powder coatings emit zero or near zero VOC
• Powder is immediately ready for use
• Less powder wastage during the application process, as overspray can be recycled
• Reduced health hazard in case of exposure of operators
• Robust cured-film properties