Design Review

Architecture & Engineering Firms

The job of architects and engineers in a consulting firm is to design facilities for their customers. Regardless of facility type—residential, commercial or industrial—each facility must be designed specifically for the customer to meet their business requirements. All facilities have become glorified warehouses for powering and using of electrical and electronic equipment. Almost every piece of electrical equipment contains electronics. All equipment that contains electronics contains an internal electronic power supply. Ninety-nine percent (99%) of all electronic power supplies are electronic switching power supplies. This makes all electrical equipment in a facility susceptible to malfunctions and failures caused by common every day electrical disturbances. 

Consulting engineers who design electrical systems for customer facilities are aware of power quality. They are aware of how to design systems that provide the power required to operate customer loads. They are also aware of how to design systems to reduce the risks associated with electrical shock to humans and fire prevention. Their engineering is focused on distributing 60 hertz power to facility equipment. Facility electrical systems for the most part work well at 60 hertz. Up until the invention of the transistor by Bell Laboratories (www.pbs.org/transistor/album1), all electrical equipment designed were based on resistance, capacitance and inductance. Today's power quality problems are caused by the use of traditional 60-hertz facility electrical systems to power electronic-based electrical equipment and pure electronic equipment. 

All facilities require a grounding system that keeps electrical equipment bonded to an electrical conductor that can be traced back to the Earth's soil. Equipment frames and internal components are connected to a ground conductor which is part of the grounding system. Frames and internal components are kept at a zero voltage as long as the bonds and connections that establish a continuous path to Earth are intact and tight. When any one of them become slightly loose, the path back to Earth is unreliable and will not likely carry any current that tries to flow through the ground conductor back to Earth. When a loose bond or connection develops, the impedance of the ground conductor will increase. Impedance increases depend on how loose the bond or connection is among other factors. 

When desktop computers with electronic switching power supplies hit the market over three decades ago, facility electrical systems started having to support non-linear switching currents. As the number of electronic-based equipment grew, facility electrical systems aged while facility support staff started to shrink. The electronic loads installed in facilities were low power (e.g., 50 to 100 watts). The technology to design and build high-power electronic loads didn't exist yet. Advances in facility grounding systems to support switching currents didn't occur for good reason. However, component researchers at General Electric (see ge.com) developed a single ceramic device with a voltage-sensitive resistance. This device, called a metal-oxide varistor (MOV), had a very high resistance under normal operation (e.g., at 120 Vrms) but a very small resistance when the voltage across the device crossed a pre-designed threshold. 

Researchers developed this device in response to concerns that high-voltage transients were occurring on building electrical systems were causing electronic power supplies to fail. GE introduced this device to the electronic design industry, and power supply designers began using it in their designs. Component and applications research continued and resulted in the development of surge protective devices. This opened the door for designing electronic mitigation components that could be used to protect sensitive electronic equipment (SEE). Electronic equipment, powered by traditional facility electrical systems which were known to have circuit performance limitations, need protection from common every day surges. 

Further research continued into why facility electrical systems increased the magnitude of voltage surges. Whether surges originated on the utility power distribution system or from the operation of contactors and circuit breakers inside a facility, when they got into a facility electrical system wiring and grounding errors in the facility caused the surges to magnify. This increased the threat of damage to electronic equipment. 

Today's facility electrical systems have an even more compromised performance for managing disturbance currents. These systems must support a plethora of electronic switching equipment: low, medium and high power. While the density of low-power equipment has reached a high level and still growing, the density of medium- and high-power equipment is increasing quickly. Disturbances from high-power equipment have more energy and will travel further through a system. Their threat to SEE is higher, especially if a lot of low-power SEE is powered on the same branch circuits as high-power equipment. 

Facility wiring and grounding systems aren't designed to manage disturbance (e.g. surge) currents to steer them away from SEE.   New wiring and grounding (and bonding) techniques can be integrated into electrical system designs to keep disturbance currents away from SEE.  This means that each facility must be capable of providing a large enough “sink” for disturbance currents when large non-linear loads are operated as well as providing a high enough voltage quality so other equipment will operate correctly. It is so much easier to included higher-performance techniques when the system is still in the design stage on paper (or on CAD these days) as opposed to trying to add new techniques to an existing grounding system.

Customers don’t have time for facility engineering reworks or downed production lines while changes are made to electrical infrastructures that should have been during the design phase. Best power quality engineering design practices should be part of every facility electrical system design. Some commercial and industrial facilities plan to operate more electrical and electronic equipment than others, or more equipment known to be more sensitive than other equipment. Some facilities will be powered from utility feeders with more energetic power quality disturbances than other feeders. Some facilities will be located adjacent to transmission towers. Some facilities will be built on soil with compromised conductivity, leaving grounding performance to be challenged. Some facilities will purchase and operate medium- and high-power equipment from one manufacturer that generates more disturbances than the same type of equipment from another manufacturer. Some facilities will use radio-frequency (RF) generating equipment that will inject disturbances into the electrical system. No two facilities are alike when it comes to the equipment the use, how they use it and the usage of their electrical infrastructure.

Having Electrotek expert PQ engineers conduct a design review of a facility electrical system and the characteristics of planned electronic loads before the design is finalized and before equipment is selected is very cost effective as opposed to the costs associated with lost production time, equipment repairs and missed order delivery times to name a few. In all cases this activity saves thousands, if not millions, of dollars for customers who own, operate and use facilities.

Electrotek developed a process for reviewing facility electrical systems that improves the PQ performance of the system. Electrotek also provides justification documentation for design changes that increase design costs, so that customers clearly understand why proactive PQ management measures are the lower-cost investment. Electrotek can provide a detailed proposal for a facility design review, depending on the facility type and other factors that impact the PQ performance at a facility. Topics include wiring and grounding, location, and type of PQ monitoring, modeling, and simulation of electrical conditions including faults, lightning protection, arc flash protection and PQ mitigation among others.

Equipment Manufacturers

Every end-use electronic product manufacturer must purchase an OEM power supply or design their own. Regardless of the approach, the power supply is still the front-end electronics that interfaces to facility electrical system. Exposure to this system which is exposed to the grid subjects the product and its power supply to malfunction and damage caused by PQ electrical disturbances. Electronic designers must be concerned with how well the power supply and its downstream electronics (i.e., the product load) is protected from the exterior electrical environment. Traditional PQ protection approaches relied solely on the metal-oxide varistor (MOV) technology to provide protection for voltage surges. 

Reliance on only MOVs to provide whole surge protection in today's facility electrical systems and their electronic switching loads does not provide the PQ protection required to adequately protect customers' electronic investments. This approach leaves "open doors" for disturbances to damage these loads, resulting in unmanaged risks of equipment failures and significant financial losses. This is compounded by the architecture in today's electronic loads. Traditionally, electronic switching loads were designed using all analog electronic components: discrete transistors, diodes, etc. Simple digital electronics didn't enter the designs of electronic loads until the late 1970's. Even then, simple digital electronics were only used deep into computer circuitry, not in the power supplies. 

Nowadays, digital electronics with much higher switching speeds are used in the front ends of electronic switching power supplies to correct for poor power factor and reduce the amount of harmonic currents utilities and facilities must supply to these loads. Moreover, all electronic switching power supplies today use three to six digital electronic chips. With today's electronic load designs using a much higher county of digital electronics, the risks associated with malfunctions and failures caused by common every day PQ disturbances is much higher than when analog components were used in loads. 

Mitigation against damage caused by PQ disturbances for today's electronic loads is more difficult to achieve. This is because of the nature of the disturbances incident upon these loads. The power quality in today's commercial and industrial facilities is much more complex than it was even 10 years ago. The characteristics of the disturbances circulating in today's facility electrical systems allow them to attack the electronic loads at a greater number of points besides just through the AC input. Electronic loads can even participate in the flow of disturbance currents from one area of a facility to another. 

Managing the exposure of today's electronic loads to damage caused by complex disturbances is best handled through a detailed design review of the product. Electrotek's expert PQ engineers developed an approach to accomplish this challenge. Engineers review product schematics (including the power supply) along with a physical laboratory testing-based review. This allows Electrotek to determine the weak links in the design that need attention. Engineers work to identify the type of PQ mitigation component and its location in the circuit required to achieve protection across the design. In some cases, protection components can be added to the circuit by hand in our laboratory. In other cases, they must be added to the schematic and PCB layout. After such improvements have been made, Electrotek engineers re-evaluate the design and expose it to some real-world PQ disturbances to determine how much the PQ immunity performance has improved. 

Designers have found this Electrotek PSPQ engineering service to be very helpful during their design (or re-design) efforts. Manufacturers can also work with Electrotek to determine how such improvements and verification of enhanced PQ immunity performance can be used as a marketing tool to their customers.