Compatibility Part 3: Applying compatibility concepts to today’s lighting products

Nov. 29, 2010
Part 3 of PHILIP KEEBLER’s series on compatibility looks at what compatibility means for today’s electronic lighting products, and how manufacturers of LED lighting devices/systems in particular can benefit from applying the compatibility concept.


This article is the third part of an ongoing series on the compatibility of lighting products:

Part 1: Compatibility and reliability are key factors in the design of LED lighting
LEDs Magazine Sept/Oct 2010 p.69

Part 2: System compatibility testing improves reliability of LED lighting devices and systems
LEDs Magazine Nov/Dec 2010 p.75


What does compatibility mean for today’s electronic lighting products?

Providing utilities and their customers with electronic lighting products (ELPs) that have been performance-tested at EPRI identifies products that are compatible with the electrical environment. Fig. 1 illustrates how electronic lighting products sit with respect to two electrical environments. Products are fed power from the electrical equipment inside the customer’s facility. The operation of this equipment and the other loads that it supports define the customer’s electrical environment. Wiring and grounding systems inside the facility play a vital role in determining if the environment is acceptable or not acceptable for the lighting product. Wiring and grounding errors can “amplify” electrical disturbances that may otherwise be unharmful to lighting products.

FIG. 1. The utility electrical environment is defined as the environment outside of the customer’s facility. This environment includes all of the electrical disturbances that originate on the utility power system from operation of the system. Utilities must engage power-system equipment such as automatic reclosers, tap changers, and switched capacitors to maintain system stabilization and voltage control for their customers. The utility environment also includes all of the faults that are initiated on the power system. Faults are caused by events such as thunderstorms that produce lightning strikes to the system, animals that crawl on insulators and conductors, tree limbs that come in contact with power conductors, and penetrations in underground cables caused by construction digging. Compatibility testing carried out at EPRI reproduces these disturbances that occur in these environments and applies them to the product to determine how the product reacts.

How can manufacturers utilize EPRI to apply the compatibility concept to their products?

EPRI is a non-profit 501(c)3 company that provides engineering research, development, and testing for the utility industry—domestic and international. EPRI’s utility customers range from utility generation companies to utility transmission companies to utility power distributing companies including federal and local power companies. EPRI’s customer base also extends to manufacturers of all types of equipment including equipment used by utilities to operate the power system to end-use equipment used by utility customers (i.e. the loads) to provide everyday necessities like electrically-produced light. Almost all of today’s loads are electronic end-use loads. Even in the days when loads were not electronic-based, utility customers would experience damage to their load equipment that was later deemed to be the cause of electrical disturbances incident upon the equipment. The fact that essentially all of today’s loads increasingly use electronics makes them more susceptible to upset and damage from common everyday electrical disturbances occurring on the power system and inside customer facilities.

Because EPRI had already worked with a number of manufacturers to make their products more robust to disturbances, utilities wanted to see these efforts continued to increase the compatibility between the public power system and end-use products. In the early 1990s, EPRI initiated a major research project called the System Compatibility Research Project. The purpose of this project was to determine compatibility of end-use electronic loads – such as computer power supplies, adjustable speed drives, and electronic fluorescent ballasts – with the public power system. Each type of load was evaluated for its energy performance, emissions performance, and immunity performance. Compatibility performance of end-use products in these three areas was determined according to test protocols developed by EPRI. Test protocols contained both industry standardized tests and compatibility tests designed by EPRI to determine how these loads reacted to a gamut of disturbances such as voltage sags and other disturbances. Some of the tests would determine just how much of a certain disturbance a load could really tolerate. If the product is too susceptible to a common everyday disturbance, then EPRI compatibility engineers study the product design to determine why and work with the manufacturer to alleviate the problem. Product improvements not only lower susceptibility but also increase compatibility. This project continued for several years until dozens of end-use loads were evaluated.

Because of the highlighted value of applying EPRI’s System Compatibility concept to hundreds of end-use loads, EPRI continues to work with product manufacturers to apply the concept to the same types of loads and to new loads. Among these new loads are new types of dimmable and non-dimmable ELPs including electronic linear fluorescent ballasts, compact fluorescent lamps, induction lamps and systems, LED lamps and systems and other advanced lighting technologies.

How do manufacturers benefit from using the concept?

There are a number of excellent benefits for manufacturers in applying the System Compatibility concept to electronic lighting products. Manufacturers want to know as much about their products as they can, especially when it comes to how they perform in real-world electrical environments in customer facilities. Although there are similarities between customer environments of the same type, no two environments are the same. The electrical environment in one residential area will be different than the electrical environment in another. Why? Two customer areas may be fed from a different distribution circuit or from distribution circuits fed from two different substations. Commercial and industrial environments are also very different. One commercial facility may include only offices but fed from a feeder that also powers a commercial facility containing different types of loads characteristic of generating a type of voltage transient known to damage CFLs.

The physical location of customer facilities also plays a critical role in establishing the facility environment. One facility may be in a high exposure area characteristic of lightning strikes or high-energy surges that travel down the distribution system circuit to the facility. Some distribution feeders are more susceptible to surges caused by lightning strikes than others. Distribution circuits utilize a lot of hardware to ensure the circuit is properly connected. However, the reliability of distribution feeders does vary from circuit to circuit. As one can see here, environments vary considerably thus warranting the need to determine compatibility levels for lighting products. EPRI compatibility tests are designed to determine how susceptible lighting products are to these environments.

Subjecting an electronic lighting product to EPRI’s System Compatibility concept will allow the manufacturer to determine product performance in a variety of areas with respect to what occurs on lighting branch circuits in customer electrical environments. In today’s energy-savings society, product efficiency and how much energy saving can be gained from using a high-efficiency product are two areas of much attention. However, if customers experience early failures and continuous malfunctions, then customer satisfaction will go down, and word may go around that products from a certain manufacturer may be known to experience early failure. Manufacturers will receive numerous complaints about the performance of their products. Product performance knowledge must go far beyond determining efficiency and energy savings. A lighting product that exhibits early degrading performance or failure will cause shifts in customer expectations. Customers will no longer be so concerned with efficiency and how much energy they can save by using an energy-saving lighting product. Instead, customer focus will shift towards product reliability: “Can I keep the lights on?”

Manufacturers must learn how to put the minds of their customers at ease when it comes to product reliability and assuring customers that efficiency levels will remain close to what is expected in the early life of the product. Lumen output must not degrade as a result of common everyday electrical disturbances. Industry standards are just now being developed and applied for SSL products and still receiving attention in fluorescent and HID products. Photometric testing at EPRI not only determines static efficiency and lumen-output levels under varying steady-state voltage input conditions but also determines dynamic efficiency and lumen-output levels under dynamic conditions. Under dynamic conditions, steady-state voltages are applied to the product while supporting steady-state disturbances. Some electronic lighting products have been found to exhibit appreciable changes in lumen output when the steady-state voltage is corrupted by certain types of commonly occurring electrical disturbance without causing product failure.

Moreover, manufacturers aim to design product warranties that are matched with the products they sell. A well-designed and effective warranty program will put forth a warranty period that compliments product performance. Regardless of the size of the manufacturer, costs associated with honoring product warranties must be kept under control. Manufacturers must be able to predict the performance of their products when they are used in typical customer environments. An underlying susceptibility problem with a product caused by an incompatibility issue can suddenly cause a major product reliability concern affecting market penetration. This can be especially hazardous to the success of a new lighting product like many of the SSL products.

The EPRI System Compatibility concept is designed to flush out product performance in all critical key areas including energy performance, emissions, and immunity. With EPRI’s test data, manufacturers will know how their product performance with respect to these three areas. Efficiency and energy savings is not only a concern at full brightness, but now also at each dimming level as many products are dimmable. The performance of a lighting product will vary as it is dimmed. Performance metrics like input total current harmonic distortion and true power factor are important for manufacturers and utilities to know as products are dimmed in customer facilities. Some manufacturers struggle with meeting regulatory requirements for radiated and conducted emissions to ensure their products pass prescribed emissions limits promulgated by the Federal Communications Commission (FCC) and other agencies both here and abroad. In several cases, manufacturers suddenly find out that their product no longer passes an emissions test when sampled from the production line. EPRI compatibility engineers can evaluate and review product designs to ensure that products always pass these tests with comfortable safety margins without increasing product cost.

Under the EPRI immunity tests, manufacturers learn exactly where the weak links are located in their product designs and what causes weak-link performance to occur. It is not uncommon for EPRI to discover a concerning weak link in product design resulting from common everyday electrical disturbances incident upon the product in the customers’ environment. What is astonishing is that the majority of these weak-link issues are resolved by very low-cost changes to the product (circuit) design. With this, manufacturers are able to alleviate known problems and avoid underlying problems while eliminating high warranty costs.

Once manufacturers become fully aware of how their products truly perform in customer electrical environments, then they can educate their customers on real product performance and convince them that early failure is highly unlikely and product reliability has been addressed from a real-world perspective.

How can the LED lighting devices/systems industry benefit from applying the compatibility concept?

Lighting device and systems manufacturers cannot afford to launch products without knowing how they perform in real-world customer environments. With the growing number of new lighting products and competition among manufacturers in the SSL industry, determining the compatibility performance of new SSL products is vital to the success of the SSL industry as a whole. Early product failures have already occurred and are still occurring with some types of products. These failures have been associated with design issues and verification of component performance among other causes. Many products have also failed due to high product susceptibilities to common everyday electrical disturbances. LED devices and systems are even more susceptible to such disturbances than products like CFLs. LED devices contain more sensitive electronic devices on average. The electronic device nature of the light source in SSL products adds another layer of susceptibility concern to SSL products. Exposure of SSL product systems to electrical environments places the whole system at risk to upset and damage caused by electrical disturbances.

From recent discussions on product survivability, it is obvious that product reliability is a major concern for the future of SSL products and the industry itself. Compatibility performance of SSL products plays a vital role in determining overall product reliability. EPRI’s compatibility concept for SSL products is designed to capture all of the standard reliability factors and combine them with results and goals of compatibility testing to ensure that the predicted reliability of the SSL product includes what does happen in the customer’s electrical environment and the public power system.

Power quality on the utility power system is improving, but EPRI research has shown that compatibility problems with ELPs still occur. Some manufacturers can clearly see this from the number of returned products and customer dissatisfaction. Utility and customer electrical environments remain complex, with more non-linear loads coming on line, increased power system control responsibilities to ensure power is delivered to these changing environments, and changes in world climate conditions producing more weather activity. If the compatibility of ELPs does not continue to be addressed, manufacturers will be placing themselves in a higher risk category, making it more difficult to penetrate targeted markets and invoke customer satisfaction. Market penetration must continue to grow but only by providing SSL products to customers that manufacturers know are reliable and will perform as specified and promised.

How has it already helped manufacturers of other electronic lighting products?

Manufacturers of electronic linear fluorescent ballasts, compact fluorescent lamps, and electronic HID ballasts continue to address reliability and compatibility for their products today as existing products are revised and as new products are developed. In all cases, manufacturers were surprised to find the types of weak links in product design that were found by applying the EPRI System Compatibility concept. As mentioned above, the majority of these changes needed to improve reliability and compatibility were very low-cost changes which resulted in orders-of-magnitude product improvements. EPRI’s concept not only identifies the weak links but also determines why they occur, and moreover, how to alleviate them. When a solution to a compatibility problem is identified and resolved, EPRI continues to work with the manufacturer to verify that product performance has improved. Manufacturers who have worked with EPRI in applying the compatibility concept have already saved millions of dollars in warranty costs and costs associated with failed lighting products and products that could have exhibited continued poor performance in customer environments.