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Distribution System Overhead Line Configuration
- Thread starter Fazlay
- Start date
davidbeach
Electrical
No. There are a multitude of configurations that would come up with the same Geometrical Mean. If you have some idea of the configuration you can narrow things down considerably.
- Thread starter
- #3
bacon4life
Electrical
GMD=[D1D2D3]^(1/3)
If you assume flat equal spacing, then you can assume: D1=D2=0.5*D3 resulting D1~=46 inches
Unfortunately, equal spacing is a bad assumption. Typically distribution either has 2 wires on one side of the pole and 1 wire on the other side of the pole, or the center phase is elevated by a foot or more on a peaker pin.
The Line to Neutral spacing could refer to:
The diagonal distance from the neutral to nearest phase
the vertical distance from the neutral to the bottom phase conductor
the vertical distance from the neutral to the geometric center of the phases
the diagonal distance from the neutral to the geometric center of the phases
Where did you get the GMD from? It could also be an average of various kind of construction owned by a utility, as utilities do not individually model the different impedances for corners, deadends, alleyarms, or other oddball configurations.
If you assume flat equal spacing, then you can assume: D1=D2=0.5*D3 resulting D1~=46 inches
Unfortunately, equal spacing is a bad assumption. Typically distribution either has 2 wires on one side of the pole and 1 wire on the other side of the pole, or the center phase is elevated by a foot or more on a peaker pin.
The Line to Neutral spacing could refer to:
The diagonal distance from the neutral to nearest phase
the vertical distance from the neutral to the bottom phase conductor
the vertical distance from the neutral to the geometric center of the phases
the diagonal distance from the neutral to the geometric center of the phases
Where did you get the GMD from? It could also be an average of various kind of construction owned by a utility, as utilities do not individually model the different impedances for corners, deadends, alleyarms, or other oddball configurations.
Although it is important to observe and comply with GMD minima, of greater importance to me is choosing an appropriate geometric configuration for your application...
Flat horizontal may not perform well in windy conditions, planar vertical won't handle either sleet jump or galloping conductors in winds with freezing rain, triangular dispo with neither vertical nor horizontal equilibrium between phases may be more unwieldy and expensive.
As Bill / waross is [ quite correctly! ] fond of saying, it depends.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
Flat horizontal may not perform well in windy conditions, planar vertical won't handle either sleet jump or galloping conductors in winds with freezing rain, triangular dispo with neither vertical nor horizontal equilibrium between phases may be more unwieldy and expensive.
As Bill / waross is [ quite correctly! ] fond of saying, it depends.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
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