POWER PLANT SENTINELS
CD 2487093 E&MP15.012
Electric Circuits, Breakers
July 5, 1930
When hundreds of thousands of horsepower traveling with the speed of lighting are instantly halted, you may be sure there will be a grand disturbance.
And there is, but all the fuss is confined in steel tanks 25 feet tall and 10 feet wide, filled with oil.
Two such tanks are shown on the front cover of this week's SCIENCE NEWS-LETTER.
They are said to be the largest oil circuit breakers in the world and the picture shows them being tested by the Westinghouse Electric and Manufacturing Co.
They will soon be interrupting power on a 220,000 volt transmission line in New Jersey.
When all is well on the power line each will allow 600 amperes of current to flow through it.
But when a thunderstorm sends a big rush of current down the line to them, which if allowed to pass would damage transformers and generating apparatus, they will instantly open the circuit.
In this way they can break an arc of 8,000 amperes at 220,000 volts, or 3,000,000 arc kilovolt-amperes.
Such an arc would flame high in open air, melting its contacts and burning nearby apparatus.
It would not be stopped in time to save the transformers and generators.
But the flame is quenched in each breaker by 22,000 gallons of highly purified oil.
Original Caption by Science Service