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Are you looking for an overview to help you understand our product better, or to dive deep into the technology to understand it from an electrical engineering perspective? Either way, we’re here to help. Our educational content is divided into two paths: overview level content for a business audience, and technical content for an engineering audience.
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The silent threat.
The premise of the SmartGATE™ is simple. Overvoltage is a ubiquitous condition that negatively affects buildings. It increases power consumption causing you to pay for more power than necessary, and oversupplies electrical equipment making it wear out faster. SmartGATE™ measures the overvoltage condition and, programmed with the voltage requirements of your building, throttles it down to a more appropriate level. This happens in real-time and dynamically changes throughout the day as the incoming voltage from the grid changes. SmartGATE™ does this using an extremely efficient auto-transformer, electronic switching, an industry-grade meter, and proprietary intelligence and control technology.
For most audiences, understanding that the device reduces voltage is easy to accept. The real question is…
How does reducing voltage save energy?
Think of a 100 watt light bulb. It operates at 100 watts in a building that has optimum voltage. But overvoltage makes the light burn brighter and hotter than it needs to - brighter and hotter than it was designed to be. It’s now burning as bright as a 120 watt bulb.
By throttling your building’s voltage down to optimum, the light goes back to 100 watts. The 20 watts per bulb your building no longer uses is your energy savings. Now operating within design parameters, the bulb lasts longer and needs to be replaced less often. This is how the SmartGATE™ maximizes equipment life, reduces maintenance costs, and saves you money.
Where does that 20 watts of saved energy go? It stays in the grid as supply that can be used by others making the entire grid a little more efficient.
But my building is more complicated
than incandescent lights…
You are right, it is. Your building is an assortment of many different types of loads with some of them reacting heavily to overvoltage and others less. But no matter how efficient your building is, there are always reactive loads impacted by overvoltage. With a SmartGATE™, everybody saves. It’s just a matter of how much.
An inefficient building with very reactive loads tends to fall at the top end of the savings spectrum at 6-8%. These buildings benefit heavily from overvoltage correction. A very efficient building tends to be at the bottom of the spectrum at roughly 2%. The vast majority of buildings sit somewhere in the middle and achieve 4-5% energy savings.
Multiply this over 10-15 years with an ever-increasing cost of power and energy consumption in excess of 1 million kwh per year and the dollar savings are substantial.
What about the wear-and-tear impact of overvoltage?
In addition to pure dollar savings achieved by using less power, overvoltage has a damaging effect to electrical equipment. For instance, say the heat in your building is controlled by a highly efficient and modern thermostat. Overvoltage constantly drives your HVAC harder than it should. But when your building heats up to the right temperature, the thermostat shuts the system off. Heating the building faster uses roughly the same amount of energy as heating it slower.
But the HVAC system is constantly operating at the top-end of its design threshold. Imagine what happens to this over supplied system over time. It wears out. It breaks. Overvoltage is often the silent killer of electrical equipment making it breakdown more often and require more maintenance than it should.
Why did one building get 7 years out of their HVAC system while another using the same equipment got 20? A likely cause is that the natural overvoltage condition is worse and wore out the system faster than it should have.
Understanding the energy-saving potential of voltage management.
Electrical distribution systems in North America are designed around a common set of voltage standards to ensure reliable operation of all electrical equipment within connected buildings. In Canada, voltage levels are dictated by CSA CAN3-C235-83(2015)1. This standard outlines voltage levels and tolerances for electrical distribution systems for commercial and residential buildings for 120V to 600V electrical systems.
Though nominal voltage levels are prescribed for each facility, the standard allows for a wide window of operation. On a typical 600V 3 phase commercial feed, the standard allows voltage to fluctuate by +4.2% -8.3% (550V – 625V) during normal operation, as measured at the service entrance of the facility.
Controlling the voltage to a fine level at every facility is extremely challenging due to the layout of typical electrical grids. Since substations and feeders often supply a large number of buildings, a compromised voltage level that balances the needs of multiple buildings is typically deployed. Voltage supplied to a particular facility is rarely static; changing daily, weekly, and seasonally as conditions on the electrical grid change. As a result, all facilities experience higher than nominal voltage supply at times. Reduced energy consumption and improved power quality can be achieved by actively managing voltage during times when a facility’s supplied voltage is higher than nominal.
The relationship between managing voltage and saving energy is well established in industry and within the academic community. Numerous studies from BC Hydro2, New York University3, and Hydro Quebec4 have shown that reducing system voltage results in substantial, power and energy reductions.
Legend Power's SmartGATE™ monitors and controls voltage coming into a facility at a 3 phase 600V level. The system consists of a high-efficiency autotransformer paired with an intelligent controller that can produce a voltage reduction of up to 8%. When installed in a facility, the product monitors the incoming voltage from the grid, identifies instances of high voltage, and in real-time reduces the voltage of the entire facility to produce a power and energy reduction.
The SmartGATE™ always keeps the facility well within the guidelines established by CSA CAN3-C235-83(2015). The system includes the ability to produce no voltage reduction if the incoming voltage as supplied by the grid is temporarily too low to support a reduction.
How much energy can be saved?
Every facility has the potential to save both energy and its associated costs by managing voltage. The SmartGATE™ will always produce a reduction in power and energy once installed. In order to fully understand the mechanism of energy savings, it is useful to review a load model and example.
The electrical load of a commercial building is difficult to measure at a fine level because it is comprised of many individual points of use that are constantly changing with weather, season and building use. A useful model for analyzing a building’s electrical load is a 3-part ZIP model5. This model views static electrical loads as being comprised of 3 components: constant impedance (Z), constant current (I) and constant power (P). The ZIP model provides a convenient mechanism for analyzing a load’s power variation in response to varying voltage.
In practical application, no individual load in a facility is entirely comprised of one component, but each load can be viewed as a linear combination of the 3 components. Within the same paradigm, an entire building can be viewed as a complex combination of multi-component loads and therefore modeled in the same way. By analyzing the response of each of these load types to a voltage reduction using basic circuit analysis techniques, the mechanism of how an entire building will save power and energy can be understood.
A circuit example can be used to illustrate the mechanism by which voltage management leads to power and energy reductions. For simplicity, a 120V base system will be discussed which is commonly derived from a 3 phase 600V system. Consider a system supplied with 122V from the grid with 3 loads (Figure 1):
1. Z - Constant impedance of 150 Ω
2. I - Constant current of 1A
3. P - Constant power of 100W
The total power is given by: Ptotal = P1 + P2 + P3 where P1 represents power for Z, P2 represents power for I, and P3 represents power for P (a fixed constant of 100W). With 122V supply solving for P1, P2 and P3 yields:
Therefore, the total load at grid supplied voltage of 122V is 321.2W.
With a SmartGATE™ installed, the voltage is reduced by 8% for an incoming grid voltage of 122V. The voltage to the load is now 112.2V. Note both 122V and 112.2V are well within the range of 110V to 126V established by CSA CAN3-C235-83(2015). Solving for PVM1, PVM2 and PVM3 where PVM1 represents power for Z, PVM2 represents power for I, and PVM3 represents power for P (a fixed constant of 100W) under reduced voltage. Using the same equations and methodology as previously shown:
Therefore, the total load at grid-supplied voltage of 122V is 296.1W with a SmartGATE™ operating with voltage management at maximum 8%.
The difference in power between grid-supplied condition and SmartGATE™ can be expressed as:
Therefore, in this example there is a power and energy reduction of 7.8% with a voltage reduction of 8%.
The above example illustrates the mechanism for achieving real and significant power and energy savings in a commercial building.
1. CSA CAN3-C235-83(2015): “Preferred voltage levels for AC systems, 0 to 50 000 V”
2. V. Dabic, S. Cheong, J. Peralta, and D. Acebedo, “BC Hydro’s experience on voltage VAR optimization in distribution system,” presented at the IEEE Power Energy Soc. Transm. Distrib. Conf. Expo., New Orleans, LA, 2010
3. Marc Diaz-Aguiló, Julien Sandraz, Richard Macwan, Francisco de León, Senior Member, IEEE, Dariusz Czarkowski, Member, IEEE, Christopher Comack, Member, IEEE, and David Wang, Senior Member, IEEE, 2013,’Field-Validated Load Model for the Analysis of CVR in Distribution Secondary Networks: Energy Conservation’, IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 28, NO. 4, pages 2428- 2436
4. D. Kirshner, “Implementation of conservation voltage reduction at commonwealth Edison,” IEEE Trans. Power Syst., vol. 5, no. 4, pp. 1178–1182, May 1990.
5. A. Bokhari, A. Alkan, A. Sharma, R. Dogan, M. Diaz-Aguilo, F. de León, D. Czarkowski, Z. Zabar, A. Noel, and R. Uosef, “Experimental determination of ZIP coefficients for Modern Residential, Commercial and Industrial Loads,” IEEE Trans. Power Del., IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 29, NO. 3, JUNE 2014