Load management
They were rotating generators that fed a 1050 Hz signal into transformers attached to power distribution networks.
This technology was a spin-off of his patented automatic telephone line identification system, now known as caller ID.
[6] At the request of the Alabama Power Company, Paraskevakos developed a load-management system along with automatic meter-reading technology.
The analysis may include scenarios that account for weather forecasts, the predicted impact of proposed load-shed commands, estimated time-to-repair for off-line equipment, and other factors.
If the power load factor is affected by non-availability of fuel, maintenance shut-down, unplanned breakdown, or reduced demand (as consumption pattern fluctuate throughout the day), the generation has to be adjusted, since grid energy storage is often prohibitively expensive.
Smaller utilities that buy power instead of generating their own find that they can also benefit by installing a load control system.
The utility in a sense "owns the switch" and sheds loads only when the stability or reliability of the electrical distribution system is threatened.
Demand response programs such as those enabled by smart grids attempt to incentivize the consumer to limit usage based upon cost concerns.
[8] The application of load control technology continues to grow today with the sale of both radio frequency and powerline communication based systems.
Consumers are usually rewarded for participating in the load control program by paying a reduced rate for energy.
Since the broadcast frequencies are in the range of human hearing, they often vibrate wires, filament light-bulbs or transformers in an audible way.
The transformers that attach local grids to interties intentionally do not have the equipment (bridging capacitors) to pass ripple control signals into long-distance power lines.
Inexpensive local electronics can easily and precisely measure mains frequencies and turn off sheddable loads.
In some cases, this feature is nearly free, e.g. if the controlling equipment (such as an electric power meter, or the thermostat in an air-conditioning system) already has a microcontroller.
Most electronic electric power meters internally measure frequency, and require only demand control relays to turn off equipment.
In contrast, as the grid recovers, its frequency naturally rises to normal, so frequency-controlled load control automatically enables water heaters, air-conditioners and other comfort equipment.
The cost of equipment can be less, and there are no concerns about overlapping or unreached ripple control regions, mis-received codes, transmitter power, etc.
[13] In many countries, including United States, United Kingdom and France, the power grids routinely use privately held, emergency diesel generators in load management schemes[14] The largest residential load control system in the world[15] is found in Florida and is managed by Florida Power and Light.
FPL has been able to avoid the construction of numerous new power plants due to their load management programs.
[16] Since the 1950s, Australia and New Zealand have had a system of load management based on ripple control, allowing the electricity supply for domestic and commercial water storage heaters to be switched off and on, as well as allowing remote control of nightstore heaters and street lights.
Ripple control receivers are assigned to one of several ripple channels to allow the network company to only turn off supply on part of the network, and to allow staged restoration of supply to reduce the impact of a surge in demand when power is restored to water heaters after a period of time off.
For those with load-managed supply but only a single meter, electricity is billed at the "Composite" rate, priced between Anytime and Controlled.
[21] Rltec in the UK in 2009 reported that domestic refrigerators are being sold fitted with their dynamic load response systems.
In 2011 it was announced that the Sainsbury supermarket chain will use dynamic demand technology on their heating and ventilation equipment.
There is also a programme that allows industrial loads to be disconnected using circuit breakers triggered automatically by frequency sensitive relays fitted on site.
