Power Quality and Lighting
Power Quality and Lighting
Poor power quality of lighting equipment does not yet seem to be a great problem. But harmonic distortion has to be managed in the future.
In 1991, a major environmental group in Sweden attacked the utility-sponsored programs that promoted compact fluorescent lamps (CFLs). The group claimed that a screw-base CFL consumes much more energy than its rated power indicates, owing to its low power factor (PF). However, they had built their case around a misunderstanding: A 25-W CFL can typically replace a 100-W lamp with an equivalent light output. The 25-W CFL, with a typical PF of 0.5, will have an apparent power of 50 volt-amperes (VA).
Since voltage multiplied by amperes normally equals watts, this was mistakenly taken to mean that the active power consumption of such lamps is 50 watts. Although it is true that 50 VA is equivalent to 50 W of generating and distribution capacity, only the rated active power of 25 W will translate into electricity consumption when the lamp is used.
Thus, the CFL in the example above, with a PF of 0.5, will free about half rather than three quarters of the generating capacity. However, the lamp will still save about three quarters of the energy used for lighting. (Power factor is further explained in the guest article Power Quality for Beginners, IAEEL 3-4/95.)
PHASE SHIFT AND HARMONIC CURRENTS
The low power factor of conventional (electromagnetic) CFLs is due to the fact that their voltage and current are not in phase. If the utility has an underground distribution network (as in a city), the capacitance of the system itself will to some degree compensate for this phase shift. Capacitors can also be installed, either at the transformer substations or on the premises of large customers. In fact, most utilities actually charge large customers extra for having a low power factor, so improving it is in the customer's interest.
When it comes to electronic CFLs, as well as all other electronic equipment, things become more complicated: Electronics generate harmonic currents. There are basically two problems with harmonics: First, they are closely related to a reduced power factor, and second, harmonic currents can disturb other equipment. Very high harmonic distortion on a utility network will also reduce the efficacy of the transformers and could ultimately damage them.
An electronic CFL has a typical power factor of between 0.5 and 0.6, but the current cannot be compensated for with a capacitor. Instead, a filter has to be introduced, either in the lamp itself (in the ballast) or somewhere in the electricity network. In countries where the government has adopted the IEC (International Electroctechnical Commission) standards lighting equipment must have a PF better than 0.96 and total harmonic distortion (THD) below 33%. But the IEC lighting standards make an exception for equipment with a rated power of less than 25W, such as screw-base CFLs. This is one reason why so much of the power quality debate has been focused on CFLs, although even worse harmonic hooligans, such as the power supply units of TVs and computers, probably deserve much more attention. (Also see article on standards: Lighting Power Quality Standards - A Brief International Overview, IAEEL Newsletter 3-4/95.)
However, even where lighting equipment actually is subject to harmonic standards, users can find the fairly strict standards for hard-wired ballasts to be insufficient. For instance, Lund University Hospital in Sweden, a large research hospital, has chosen not to use them. Their buildings are packed with so much other electronic equipment that a large-scale introduction of electronic ballasts would add substantially to the THD in the building, they claim.
FEAR FOR FUTURE HARMONIC HOOLIGANS
Electric utilities must keep THD on their network below certain levels. If a utility is close to its so-called planning levels, even marginal additions may have an impact on the utility's ability to connect other large customers without additional investments.
One may thus ask if it wouldn't be better if all equipment were to be designed to have no harmonic emissions and high PF. Yes, it would. But it is also a matter of cost: For the Ilumex Project in Mexico, Philips delivered CFLs with good power characteristics, but they were also more expensive than standard CFLs. There is a fear that the higher price of power-factor-corrected CFLs would be too high for many consumers.
CFLs often have received an unfair amount of criticism for their poor power characteristics. This is true despite the fact that computers, microwave ovens, fax machines, answering machines, etc, add more to a utility's THD than CFLs would, even if the latter were to be used extensively. And, many of these devices are on 24 hours a day. On the other hand, some utilities claim that lighting makes up a relatively large share of the evening peak load and thus should be given special attention.
The overwhelming majority of electric utilities don't tend to see CFLs in residential applications as a problem today. But many fear what will happen in the near future, considering the explosive growth of electronic equipment in both homes and offices. They want all manufacturers, including those in the lighting industry, to take more responsibility for their products.
However, utility views vary depending on the status of their distribution system and their load characteristics. For instance, the electric utility serving Cleveland, Ohio, with a large industrial load, is reportedly not too worried. Con Edison in New York City, with a large commercial load, is said to be more worried, as is Tokyo Electric. English and Swedish utilities are also becoming increasingly worried about harmonic pollution.
"CLEAN" EQUIPMENT NOT FOR FREE
The lighting industry, on the other hand, thinks it is unfair to demand so much from CFLs since they serve an energy-conserving function as opposed to, for instance, TVs and computers. Lampmakers argue that improving the power quality of a TV set or a computer will only influence the price of that product marginally, whereas improving the power quality of a CFL can influence its price substantially. Many CFL manufacturers maintain that they want to do something about the problem, but need time for testing and for finding reliable solutions. On the other hand, power-factor-corrected CFLs have been available in the US for at least five years.
Eventually, harmonic standards for lighting will also apply to CFLs, but it will take time. This is a complicated, never-ending game of poker between manufacturers, governments and electric utilities. Both utilities and lampmakers say that improving power quality is expensive and that customers eventually must pay for it. But if the incentives are right and if competition works, costs could certainly drop for the lamps as well as the equipment used in the electricity networks. Experience gained in Swedish and US technology procurement programs shows that improvements in both the price and performance of products could be achieved if enough dedicated buyers go together to put pressure on manufacturers.
This may become a moment of truth for both utilities and lamp manufacturers. When it comes down to the nitty-gritty, will utilities consider this problem to be serious enough to bother with? And if someone comes up with large potential orders, will lamp manufacturers be able to meet demands at a reasonable cost?
Meanwhile, the poor power quality of CFLs does not seem to be a serious enough disadvantage to warrant that they not be used.
Nils Borg
Note: This article is partially based on a discussion in Stockholm with Mr. K Seshadri from Philips Lighting, Singapore, and Mr. Geoff Finlay of the UK Electricity Association, who also provided reports reflecting their views on the subject. BMR. Finlay's report is available from IAEEL on request. For an abbreviated and adapted version of A Rashid Ibrahim/Seshadri's report, see Power Quality For Beginners (IAEEL 3-4/95). See also Lighting Power Quality Standards - A Brief International Overview (IAEEL 3-4/95).