Increase the value of your business with SmartGATE™

The premise of the SmartGATE™ is simple. Power Quality is a ubiquitous condition that negatively affects buildings: it decreases the uptime and lifetime of your equipment, and increases power consumption and operating costs, negatively affecting your business. The SmartGATE™ platform measures the risk and waste in your buildings and automatically improves many of the issues, while saving energy at the same time. This happens in real-time and dynamically changes throughout the day as the incoming power conditions from the grid change. SmartGATE™ does this using an extremely efficient auto-transformer, electronic switching, an industry-grade meter, and proprietary intelligence and control technology.

 
 

How does SmartGATE™ protect my building?

Poor power quality results in three outcomes: decreased uptime, quicker failure, and more repair and replacement expenses. Equipment that is critical to a building’s success such as elevators, HVAC, security systems and control systems are all vulnerable to power quality issues. The good news is that SmartGATE™ can act as a firewall to protect your building, while saving energy and increasing the value of your business.

SmartGATE™ provides power quality improvements in 5 areas: voltage sags and swells, consistent undervoltage, consistent overvoltage, power factor correction, phase unbalance and power factor improvement.

Voltage Control: Quick disturbances in voltage that can lead to equipment restarting or malfunctioning. SmartGATE™ can buck and boost voltage to ride-through some sags and swells. This can help increase uptime and protect the lifetime of the building’s equipment. SmartGATE™ can also protect from sustained undervoltage and overvoltage which can cause increased wear on equipment. This can lead to quick failure of critical pieces of equipment such as motors or sensitive electronics. Consistent overvoltage also wastes energy. 

Phase Balancing: SmartGATE™ provides voltage balancing on the three phases of electricity in your building. Phase unbalance causes 3-phase equipment such as chiller motors, elevators and industrial equipment to operate inefficiently by generating excess heat. This increases your electric bills and can cause rapid failure of equipment. SmartGATE™ independently balances each phase to ensure long lifetimes and maximum energy savings.

Power factor Improvement: Power factor shows up on most utility bills and is a rough measurement of a building's efficiency. SmartGATE™ improves your building's efficiency and will improve this parameter, reducing extra costs paid to your utility.

 
 

How does SmartGATE™ save energy?

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SmartGATE™ saves energy by setting the voltage at the optimal point of the approved range. Around 112 volts the majority of electrical equipment will operate at peak efficiency without sacrificing performance. On average, SmartGATE™ reduces energy waste by 5-6% of a building’s total energy use. Voltage optimization has been practiced by utilities for decades, however, only Legend has been able to combine energy savings and power quality improvements into a small, cost-effective solution for entire commercial buildings.

 
 

Understanding the technical potential of power management

 

Electrical distribution systems in North America are designed around a common set of power standards to ensure reliable operation of all electrical equipment within connected buildings. Power standards are primarily dictated by ANSI 84.1 for steady-state conditions and the Information Technology Industry Council, SEMI, IEEE and other third-party associations for non steady-state conditions. These standards and guidelines outline voltage levels and tolerances for electrical distribution systems and end-use equipment for commercial and residential buildings for 120V to 600V electrical systems.

Controlling the voltage to a fine level at every facility is extremely challenging due to the layout of typical electrical grids and the increasing usage of distributed energy resources. Since substations and feeders often supply many buildings, and power supply is becoming more decentralized, a compromised voltage level that balances the needs of multiple buildings is typically deployed. Voltage supplied to a facility is rarely static; changing daily, weekly, and seasonally as conditions on the electrical grid change. As a result, all facilities experience sustained higher than nominal voltage supply, voltage sags & swells and voltage unbalance. Reduced energy consumption and improved power quality can be achieved by actively managing voltage.

The role of the power utility is the keep the grid operating; power quality and energy efficiency are often secondary concerns. The established power standards and industry recommended guidelines help govern distributed power quality. However, these guidelines should not be taken as the gold standard for efficient and reliable building operations. Operating equipment near or beyond the upper or lower edges of established power standards will result in building deficiencies, primarily presenting as: equipment malfunctions, premature equipment failure and energy waste.

Though nominal voltage levels are prescribed for each facility, the ANSI 84.1 standard allows for a wide window of operation. On a typical 480V 3 phase commercial feed, the steady state standard allows voltage to fluctuate by ±5% (456V – 504V) during normal operation, as measured at the service entrance of the facility.

Short-term voltage level guidelines (non steady-state conditions) allow for a much wider window than ANSI 84.1 steady-state conditions prescribe. The ITI Curve is one of the most broadly referenced voltage ride-through standards and is often found within a utility’s services agreement. The ITI Curve recommends that equipment (primarily IT and electronic-based loads) be capable of riding-through voltage sags of up to 70% for 30 cycles, Most power utilities view sags of this magnitude and duration as an acceptable supply standard.

Beyond steady-state and short-term voltage levels, voltage phase balance is also of high importance. NEMA and ANSI both provide voltage phase balance guidelines which most North American utilities adhere to. Similar to supply voltage levels, phase balance also varies throughout the day and year. Although the primary cause of phase unbalance is load-side (equipment within the building), most utilities deem a voltage supply unbalance of up to 2.5% as acceptable.

Legend Power's SmartGATE™ monitors and controls voltage coming into a facility at a 3-phase 480V level. The system consists of a high-efficiency autotransformer paired with a DC to DC bridge that can boost and buck voltage, phase by phase ±8% of supply conditions. When installed in a facility, the SmartGATE monitors the incoming voltage from the grid, identifies instances of high, low and unbalanced voltage, and in real-time,holds all three phases of power to an established target for efficient, reliable building operation.

How does improved power quality increase the up-time and lifetime of electrical equipment?

 
 

Voltage sags and swells are commonplace on the electrical grid. The average grid-connected building will experience 40-50 voltage sags or swells per year. Equipment manufacturers and building operators are expected to ensure their equipment is capable of riding-through short-term low and high voltage events.

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Although all equipment is susceptible to poor power quality, modern electrical equipment is particularly sensitive to malfunctions and failure when voltage levels deviate from ANSI 84.1 steady-state conditions. The ITI Curve (presented below) is one of the industry's most referenced short-term power quality guidelines. Equipment is expected to function within these conditions, but often equipment begins to malfunction well before the “cut-off” point is reached. Operating near, or worse, beyond the ITI Curve is not the recommended best practice. Elevators, IT equipment, motor controls and life & safety equipment are all subject to malfunctions, leading to disruption and failure as voltage conditions get closer to the ITI “Cut-off” threshold.

Legend’s SmartGATE platform is an onsite 'buck & boost' voltage regulator that can increase or decrease voltage by up to 8%, responding to grid conditions and adjusting voltage on a cycle by cycle basis. The SmartGATE increases a building’s voltage ride-through capability, increasing equipment up-time and lifetime while limiting exposure to poor power quality events.

Phase unbalance is also a point of concern for building operators; phase unbalance is a driver of energy waste and premature equipment failure. NEMA and ANSI both provide guidelines on phase unbalance. Balanced voltage is the ideal, but generally unattainable target, in most commercial buildings. Voltage unbalance greater than 2% starts to produce significant current unbalance, increasing motor losses and motor operating temperatures.

The SmartGATE regulates supply voltage on a phase by phase basis and can produce balanced voltage ±8% of supply conditions. Correcting for phase unbalance saves energy and also increases the useful life of most three-phase, inductive loads.

How much energy can be saved?

 

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, leads to reductions.

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
6. https://www.epri.com/#/pages/product/1017340/