The Wyman Dam Mystery, Revealed
We thought you'd enjoy this response to a question posed in a John Gould essay: What is the electrical-generator doohickey that makes clocks run on time?
I am writing in response to John Gould's column of June 21 ["Two Electrifying Ideas That Never Lit Up the World," Page 17], in which he tells of a disappointment. He had not heard back from his electric utility, which had promised him a letter more than 60 years ago describing a device at Wyman Dam in Moscow, Maine, that controlled the pulse of power to keep clocks on time.
When I started this job of responding to customers' questions a few years ago, I had no idea there was an unanswered one going back to the 1930s.
We supply electricity at 60 cycles AC. This means that the voltage alternates between a positive and negative charge 60 times a second. The speed at which the generator rotates determines the cycles per second. Clocks with small synchronous motors are very sensitive to the frequency of the electricity supplied. If it is less than 60 cycles a second, they run slow. If it is more than 60 cycles a second, they run fast.
The generators at Wyman Dam are tied into a regional power grid, the New England Power Pool (NEPOOL). Frequency on the grid is monitored by NEPEX, the operating arm of NEPOOL. It sends signals via microwave to generating stations around New England to increase or decrease power to the generators to maintain proper frequency.
When the generator shaft at Wyman Dam is rotating at 138.5 revolutions per minute, the generator puts out 60-cycle current. To change the frequency, the governor (not John Reed, the former Maine governor Mr. Gould referred to) on the water turbines is adjusted to increase or decrease the flow of water, which in turn spins the generator faster or slower.
Dana Sullivan in Hydro recalls in the 1970s seeing a device that monitored frequency at Wyman and made automatic adjustments to the governors. It was tied into the National Bureau of Time Standards via the phone lines. Perhaps this is what Mr. Gould should have been shown on his tour in the 1930s.
Uncle Sam, as the official timekeeper, runs the master atomic clock in Washington. The National Bureau of Time Standards also has a radio station, WWV, that broadcasts the correct time. Every several years there needs to be a few-second adjustment to clocks to keep them in sync with the atomic clock. Uncle Sam sends word to NEPEX and other operators nationwide to increase or decrease frequency ever so slightly for a few hours to bring electric clocks back to the correct time.
If John Gould would like another tour of Wyman Dam, we would be honored to show him around. And I hope he forgives us for the delay in this response.
Central Maine Power Company
Consumer Affairs Specialist
John Gould replies:
Specialist Alioto's timely explanation is appreciated. In the 1930s, when Wyman Dam was first in hydropower operation, NEPOOL and NEPEX did not exist, as Maine had its Fernald Law, which forbade sending surplus electrical power to foreign places, including New Hampshire. We folks thought it prudent to keep the power home and get the good of it.
Yes, our microwave oven has a timepiece, but it fails with the PFs, pronounced "pfff't." What electric clocks we have are battery-operated, and reliable through a PF. If we lose power, they don't know it. But our cherished household clock is a schoolroom model with cherry case that strikes the hour and half-hour and operates on a 14-cycle frequency. I give the clock key seven twists on the time and seven twists on the strike every Saturday evening at bedtime, and the thing brings us ding-ding time all week. If I forget to wind, and the clock falters, I do not consult the radio signals of the United States Bureau of Standards, which are enunciated every five minutes and usually cause a tedious wait. Instead, I tune in the Canadian international time signals from Toronto, which come every minute in both French and English. In this crude way we have never missed a meal on time.
One hundred and fifty-five feet high, Wyman Dam raises the level of the Kennebec River 135 feet and stores 6 billion cubic feet of water. It is 10:30 a.m.