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Miscellaneous – Substation Design Calculations

Posted on by QUANG ANH
vietnam substation construction
01
Mar

Miscellaneous – Substation Design Calculations

Transformer noise calculations

transformer noise - substation design calculations
Figure 24: The transformer core is made of laminated sheets of metal (to minimize eddy current loss). A downside to this is vibration induced by 60hertz alternating current. Noise is not only generated in core. The coil, mounting, housing, conduits, fans, pumps etc. all generate noise.
Why conduct transformer noise calculations
Power transformers generate audible noise, typically greater than 60db. This can be over-bearing.

If the substation is located in a city, the constant hum from a new transformer may be unacceptable by local ordinances (especially at night time.)

Outcome of transformer noise calculations
Specify standard sound transformer if the noise generated is acceptable. Otherwise, mitigate the noise using either sound walls or by specifying low-sound transformer.

Harmonic analysis

Power Substation Design Calculations - A Checklist of 18 Studies for Engineers to Consider 4
Figure 25: Substations feeding facilities containing VFDs or UPS systems and substations containing SVC’s or HVDC converter stations, require harmonic analysis. Picture credit: ABB drives US.
Why conduct harmonic analysis?
Non-linear loads (characterized by changing impedance as it draws power) injects harmonics into supply voltage and current. The resulting waveform is not smooth but one marred by spikes and dips. When these propagate into the high voltage system, they damage power transformers and affect the power quality of other customers.
Outcome of harmonic analysis
In substations where harmonics are present, specify equipment to filter them out. The methods and means of doing this are mentioned here.

Fire protection study

Power Substation Design Calculations - A Checklist of 18 Studies for Engineers to Consider 5
Figure 26: Firewall around oil filled transformer. Image credit: FortisBCHollywood substation.
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Figure 27: Water deluge system for the transformer.
Why conduct fire protection study?
Short circuit at any location inside the substation generates an incredible amount of heat, as high as 40,000F – enough to cause the oil to catch fire, vaporize copper or aluminum material and burn any other material caught in its path.
Outcome of fire protection study
Install firewalls. Fireproof the control building, not just sidewalls but penetrations in the floor as well.

Passive fire protection system (like smoke detectors) are typically installed however, in urban areas, some form of fire suppression system is also installed. These active systems could be deluge system (figure 27) or clean agent suppression system.

QUANG ANH