arion
Member
- Location
- sapporo Hokkaido Japan
OK we had a winds storm recently i have been staying at am american friends home. in Washington state. they lost power to only half the house 6 times in a row each interruption lasting 30 sec at regularly spaced intervals of 2 min as recorded by the datacom pfe recorder on the ups that was on the affected bus the second ups system had no loss of primary mains only the under-volt transfer events logged by both ups units are common those are correlated with the timestamps on data packets retrieved from Puget sound energy's scada telemetry on various primary re closer operations. the lineman that arrived while i was out getting a bite to eat was not able to recreate the loss of the service leg by manipulating the service drop feeding the premises. and he verified that all primary and secondary terminations were solid. i went through the premiss side lugs myself with a torque bar and verified all the lugs on the feeders and breakers were tight also when i returned. the entire electrical system in this home is new only a year old from the pecker head clean down to the last outlet in line. the feeder between the main service and the distro panel inside is 3/0x2 2/0x1 1/0x1 copper. length of the run between main and load center is aprox 57 feet in a 2 1/2 ridged pvc conduit.
the only section of the system that i can see having a fault is the aprox 80 feet of 1/0 overhead AL+alcsr messenger that composes the service drop or the pole pig itself as these are the only two components aside from the meter that have not been replaced since the home was installed on the lot in 1982. i may be mistaken about the pig that's roosting on that pole out front but its getting pretty rusty under the secondary lugs. and no pardon my french ohmes law doesn't change the resistance of aluminum wire is the same in free air or in conduit your not going to pull 200 amps or the 390 pse's load calc claims through a 1/0 al cable without a stupid amount of line loss i put a 100 amp load on that thing and on a recently calibrated fluke 117 dvmm i repeatedly get an 11 volt drop on L1 and 10 volts on L2 both are below the ucom min of 114v. the math puts the resistance of that wire at almost 1/8 ohm. a properly sized service drop should allow half the service load rating to be drawn without falling below 115 volts so someones load calc in the eng depart is a crock of horse bunk. you can draw 200A at 80 volts through 1/0 copper welding cable it will warm it up nicely but reliability wise 2/0 would be recomended
the only section of the system that i can see having a fault is the aprox 80 feet of 1/0 overhead AL+alcsr messenger that composes the service drop or the pole pig itself as these are the only two components aside from the meter that have not been replaced since the home was installed on the lot in 1982. i may be mistaken about the pig that's roosting on that pole out front but its getting pretty rusty under the secondary lugs. and no pardon my french ohmes law doesn't change the resistance of aluminum wire is the same in free air or in conduit your not going to pull 200 amps or the 390 pse's load calc claims through a 1/0 al cable without a stupid amount of line loss i put a 100 amp load on that thing and on a recently calibrated fluke 117 dvmm i repeatedly get an 11 volt drop on L1 and 10 volts on L2 both are below the ucom min of 114v. the math puts the resistance of that wire at almost 1/8 ohm. a properly sized service drop should allow half the service load rating to be drawn without falling below 115 volts so someones load calc in the eng depart is a crock of horse bunk. you can draw 200A at 80 volts through 1/0 copper welding cable it will warm it up nicely but reliability wise 2/0 would be recomended