Feel the Power
There are so many items in a radio or TV facility that we classify as mission-critical; but what can possibly be more mission-critical than the station's power source? Living in a large metropolitan area — such as I do — one of the worrisome aspects of summertime is the possibility of rolling power blackouts. And that's just one reason for the power to go off.
Precipitated by the Clear Air Act, in 1979 the EPA advanced new source performance standards from stationary sources, which includes ac power generation equipment. New standards were developed (known as Tiers 1, 2, 3 and 4) but it wasn't until 2006 that the final regulations were set in stone. In the interim period, different states developed different standards. Today the EPA requirements in Tiers 1 through 4 are the minimums that any particular state must meet (see CFR 40 part 60). Tier 1 regulations were phased in from 1996 to 2000; Tier 2, from 2001 to 2006; Tier 3, from 2006 ‘til 2008; and finally Tier 4 from 2008 through 2015. The purpose of the tiers is to diminish over time the release of particulate matter (PM) and NOx (nitrogen oxides) into the atmosphere. In 1998 the EPA estimated that by 2010 NOx emissions would be reduced by about a million tons per year — the equivalent of taking 35 million passenger cars off of the road.
A new model for power
Buying a new generator today means that you'll be getting more than just an old, smelly beast that sits out behind the transmitter building, practically out of site and all too often out of mind. Aside from running cleaner, many come with modern communications facilities that can make our lives as radio engineers a little easier. For instance, Kohler makes an extensive line of generator sets, over a very wide range of power and different fuel systems, such as diesel and LPG/natural gas. A recent addition is the Powerscan Monitor System, a monitoring and alarm system that communicates outbound via the GSM cellular system. User-defined alarm conditions and telemetry are forwarded to a control center via the wireless connection, and thereafter forwarded for action to whomever is designated by the generator owner. Messages can be sent by e-mail, telephone, fax or to a pager. A website is maintained at the control center as well, allowing the end-user to remotely monitor the generator.
Not to be outdone, Cummins/Onan offers a wide range of power levels as well, with the typical fuels: diesel, LPG/natural gas and gasoline. Its monitoring and communications system is known as Power Command Iwatch and is a browser-based system that allows the generator set to be operated and monitored via LAN/WAN or the Internet (or even a good old-fashioned telephone line modem). Start/stop capability in addition to telemetry is available via what Cummins calls an easy-to-grasp GUI. Alarm conditions are reported to the end-users of the genset by way of e-mails.
Cummins is also working on a commercially-viable SOFC (solid oxide fuel cell) in conjunction with the Department of Energy. The power level is 10kW, and its introduction to the market is expected no later than 2011. Natural gas is the fuel source for the SOFC, by the way. The goal for the cost of the system is $400/kW.
Caterpillar is a familiar large manufacturer of generator sets powered by diesel or natural gas. Probably the most interesting aspect of Caterpillar is the maximum sizes that it builds — over 10MW for diesel and about 5MW for natural gas.
Generac is yet another familiar generator manufacturer. In addition to its line of compression-type engines (i.e., those running on diesel fuel) and spark-ignition types (gas) it also offers a Bi-Fuel system, which is actually a redundant fuel system. When the generator starts, it runs on diesel; but as the load is applied, natural gas is substituted. Just enough diesel is left in the mix so that the compression inside the cylinders will continue to ignite the fuel mix. The primary advantage asserted by Generac to a system such as this is the greatly extended run time due to a reduced draw on the diesel fuel itself. Should the source of natural gas be missing for some reason, the generator will run 100 percent on diesel.
If you can't be satisfied with just a single generator for standby power at your facility, you may want to consider multiple units, with their outputs combined via large switching panels and synchronization of the output waveforms. All the manufacturers I've mentioned — Cat, Generac, Cummins and Kohler makes systems to accomplish that.
It's obvious in this day and age — with a radio or TV facility almost completely reliant upon computers for the generation of program material — that keeping the power available during the time it takes to switch over to the standby power source after a power failure is an absolute necessity. That's where the UPS comes into the picture. For our purposes there are basically two types of UPSs: off-line and online (commonly known as double-conversion).
If you are planning on backing up ac power that feeds computers, avoid the off-line UPS types. The problem with that type is that it needs time to not only detect a loss of ac, but to switch over to its internal backup source. This series of events is going to take around 20 milliseconds; during that time the power supplies that feed the computers, routers and all other equipment are going to have to use their internally stored energy (in those big power supply capacitors) to make up the difference, and when that happens all kinds of havoc can occur.
So, assuming you are settling on the online type, you then must decide to what level you want your system backed up. Will you protect individual racks that hold important servers, for example? Or will you provide a backup for your entire technical core? There are many factors to be considered in that decision, but I do want to bring to your attention some manufacturers and what they offer.
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