SUBJECT: The Joy of 60Hz AC Power When I was in college, I had this Job interview at an electric utility company. The guy who interviewed me had the personality of a turnip. Like, no personality at all. Zero. My eyes grew heavy. His voice started getting far away. I began to slip into dreamland. I nearly fell asleep, just listening to him describe the wonderful department he worked in. You never want to fall asleep in a job interview. Late that night, I lay awake pondering... what could cause this man to be so monotone, so featureless, so completely... blah? Suddenly it hit me: This man listens to 60 Hertz transformers humming day and night. 'Round the clock, 24/7. It's his job to keep that sixty cycles per second going, 365 days a year, without fail, so that our toasters and microwave ovens keep toasting toast and popping popcorn. Indeed, this 60 Hertz AC power is the very bedrock of civilization itself. Should that power ever fail, we'll be plunged into the dark ages again, with chaos, bedlam, looting and riots. And if the 60 Hertz hum ever stops, it's HIS neck on the guillotine blade. Well, I didn't take that job. I took this job instead. Designing these networking gizmos and whatnot here at B&B Electronics. So the other day we got this call. It's a guy named Matt from a power utility. Matt is another one of the loyal servants of mankind who keep the transformers humming. Matt wanted to talk about his substations. Matt liked his 60 Hertz but what he was not too enamored with was the 1200 Baud. That's the speed at which the substations' RTU communicated with the computer system in the Mother Ship. Plus, Matt's crew was making 2-3 trips a week to the substations to reprogram breaker settings and retrieve history logs - sometimes in blizzard conditions. Trucks might be overturned on the highway. Lovers might be separated. But Matt had a duty to mankind which his team never failed to fulfill. You probably don't know that most of those big high-tension power lines have fiber optic cables on 'em? The substation has two Single Mode Fiber Optic Cables coming in from headquarters. Matt replaced the expensive RTU and 1200 baud with a high speed LAN and a simple terminal server box. Not only does he get the usual monitoring of voltages, currents, breaker status, power usage, transformer temperature, etc., but he can reprogram devices and bring back history reports that the original SCADA system didn't support. He doesn't have to make these trips anymore. Trucks may be overturned on the highway and lovers may be separated, but engineers can reprogram devices and retrieve data from their offices. Reports show millisecond by millisecond data during fault conditions, and an Automated Meter Reading System collects data for the billing computer. The magic is achieved with a surprisingly simple array of DIN Rail mount devices from our catalog: - An industrial-grade Fiber to Copper converter puts the data on the ever-familiar Blue Ethernet cable. http://www.bb-europe.com/product.asp?dept%5Fid=125&sku=EMD%2D100FSC&s=ee072204 - A series of 5- and 8- port Industrial Ethernet switches distribute the data throughout the substation. http://www.bb-europe.com/product.asp?dept%5Fid=125&sku=IASW5P&s=ee072204 and http://www.bb-europe.com/product.asp?dept%5Fid=108&sku=EIP308&s=ee072204 - Serial Servers convert Ethernet to RS-232, extending Intranet access to all the serial devices. http://www.bb-europe.com/product.asp?dept%5Fid=125&sku=ESP904&s=ee072204 - An RS-232 to RS-485 converter allows multi-drop communication to SCADA devices with RS-485 ports: http://www.bb-europe.com/product.asp?sku=485LDRC9&dept_id=3&s=ee072204 - Some serial devices here are optical, to reduce electrical noise; this converter links the fibers to standard RS-232: http://www.bb-europe.com/product.asp?sku=FOSTCDR&dept_id=28&s=ee072204 -For some devices, we need up to 2,000 volts of isolation. This devices provides that: http://www.bb-europe.com/product.asp?sku=232OPDR&dept_id=73&s=ee072204 My newfound curiosity about power distribution led me to call Dave, an old college buddy who chose Power as his field. Dave always gets a bit miffed when I poke fun at his life where the definition of high frequency is 61 Hz and low frequency is 59. So I said to Dave: "So really, this power distribution stuff isn't really as boring as it sounds - you guys actually do some pretty cool networking and data acquisition tricks, huh?" Dave sez to me, "This stuff IS interesting. But Mike," he says, an alienated man yearning to be understood, "The 60Hz transformer hum IS interesting too." Huh? Trying to be open minded, I asked him to explain. "You make it sound so...one dimensional, and it's just not that way. There's 4160 volts... there's 13,800 volts, 35,000 volts, 115,000 volts and even 345,000 volts. "There's not one phase, there's three. There's phase to phase, and phase to ground. I'm telling you, transformer hums come in all shapes and sizes. "And it's not even confined to 60Hz. All those transformers have half-wave rectification effects and hysteresis, which makes an infinite series of harmonics - 120 Hz, 180 Hz, 240, 300, 360 - a Fourier series. Inside those humming transformers is a complex world of voltages, harmonics, and deadly chemicals." He sure showed me. I just wish the guy had explained all this at my job interview. Had I understood this, I would never have accused him of having the personality of a turnip. I am now enlightened. So... Let it be known that here at B&B Electronics, we think ALL of our customers are exciting. Yes - even the guys who keep the transformers humming. Happy connections, Mike Fahrion, B&B Electronics Rants? Raves? Psychotic angles on Transformer Hum? Email me: mailto:support@bb-europe.com