Bobhook149
Senior Member
On a residential home when I look to the street, I see what looks like a tap on only one High Voltage line and a ground. Am I mistaken? I ask because once it gets to the house there are 2 sign waves, right?
Street transformers
- Thread starter Bobhook149
- Start date
- Status
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Nope. 1 sine wave. 2 poles off a single transformer with a center tap to ground.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110517-2117 EDT
On many residential pole transformers you see one high voltage bushing for the primary. The other end of the primary winding is common to both the neutral to the house (center tap of the secondary winding) and the high voltage neutral wire, that high voltage neutral is in many cases a pole to pole wire lower down on the pole, and is the neutral of the high voltage Y supply. It has to be a Y supply. Also connected to this common neutral point is a ground rod at the pole.
In my area we have a three phase delta system ungrounded anywhere in the neighborhood. I suspect it is a 3 phase Y at the substation with the neutral grounded at the substation. Thus, my pole transformer has two high voltage bushings connected to two of the three phase lines. Thus, no problems from from primary neutral current getting into my house. Only the secondary center tap is connected to the pole ground rod. Within my yard I have relatively low voltage gradients between different points in the yard. I usually use a 12 ft span between test probes (screwdrivers) poked into the soil for testing.
You have described a single phase transformer with a center tapped secondary providing 120 (0 deg) and 120 (180 deg) voltages relative to neutral (center tap) and 240 V across the whole secondary.
.
On many residential pole transformers you see one high voltage bushing for the primary. The other end of the primary winding is common to both the neutral to the house (center tap of the secondary winding) and the high voltage neutral wire, that high voltage neutral is in many cases a pole to pole wire lower down on the pole, and is the neutral of the high voltage Y supply. It has to be a Y supply. Also connected to this common neutral point is a ground rod at the pole.
In my area we have a three phase delta system ungrounded anywhere in the neighborhood. I suspect it is a 3 phase Y at the substation with the neutral grounded at the substation. Thus, my pole transformer has two high voltage bushings connected to two of the three phase lines. Thus, no problems from from primary neutral current getting into my house. Only the secondary center tap is connected to the pole ground rod. Within my yard I have relatively low voltage gradients between different points in the yard. I usually use a 12 ft span between test probes (screwdrivers) poked into the soil for testing.
You have described a single phase transformer with a center tapped secondary providing 120 (0 deg) and 120 (180 deg) voltages relative to neutral (center tap) and 240 V across the whole secondary.
.
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