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Keeping the Lights On

 Reducing EPA fines by conditioning the voltage

 Abstract

Voltage fluctuations are a fact of life. There is nothing the Electric Utilities can do to prevent voltage sags (BLIPS) and short term outages from occurring on the electrical distribution system. These variations in voltage cause many different types of equipment to stop operating and in some cases to suffer from component failure. This includes Ultra Violet lighting systems. UV systems used for disinfection are very sensitive to a reduced voltage supply. In the event they turn off due to low voltage the largest problem is the length of time they take to re-strike and start operating again. The time taken to restart is dead time and contaminated water flows for the full duration, which in large systems could be millions of gallons of water per event. The EPA levies penalties under the Clean Water Act to Industry and Municipalities that fail to treat water in excess of a small percentage of the annual water flow.

Installing the latest voltage conditioning equipment to prevent this eventuality often has a single event payback or better. The equipment used today is a very efficient high performance solution to maintain a solid voltage supply to the lamps. This results in longer life of the UV lamps as well as “Keeping the Lights on” when the electrical system fails. We discuss the technology in detail and discuss the results of third party testing that highlight the advantages to the UV operator.   It is imperative to reduce the risk of EPA fines and this tool provides a simple solution to an expensive problem

Introduction

Around the World Electric Utilities battle every day to improve the reliability of the supply to their customers. Even though the Utilities are getting better at reducing voltage fluctuations they cannot prevent them from occurring. In the mean time as we get more and more advanced equipment that provides us with higher productivity and better effectiveness and efficiency, the one downfall they all have is that they are more and more sensitive to voltage variations. These voltage sags and outages are due to electrical faults typically as result of a lightning strike on a transmission line, animals being electrocuted on the lines or a traffic accident with a utility pole.

The majority of these events are voltage sags and not complete blackouts. These sags, however, are often deep enough to shutdown all operating equipment.

 Figure 1: Voltage sags are the main issue

Twenty-five years ago 90% of all voltage disturbances were voltage sags as shown in figure 1. These numbers have been confirmed to be identical today by more recent studies completed in 2002 and 2004.The most interesting fact from these studies is that only about 3% of all voltage disturbances are complete blackouts.

Figure 2:2002 voltage disturbance data

Figure 2 shows more detail regarding the distribution of these events and long outages can be seen to be a very rare event.

These power BLIPS, as they are known, (Brief Lapse in Power) cause industrial and commercial equipment along with municipal loads to trip offline and often create a very large interruption in continuous processes.

In the case of water and wastewater treatment this interruption results in discharge of untreated water in to public waterways. This obviously creates a health hazard to the general public. The EPA has jurisdiction over the public water system and under the Clean Water Act has the right to impose fines and/or criminal charges for polluting the water system.

The Issue – Ultra Violet lights

There are many varieties of UV lamps on the market today each of them has their own unique characteristics. There is one common denominator and that is they all need a reasonable amount of voltage to operate.

How do UV lights work?

Ultraviolet lights use a physical method of microbe destruction instead of the more common chemical methods (i.e. chlorination). The key elements of UV light systems are a ballast and lamp combination, a Teflon or quartz sleeve to protect the lamp and a properly designed reactor chamber. The ballast is the controlling device that drives the lamp at the desired electrical conditions. UV lights work best when voltage or cycle variations do not exceed manufacturer’s specifications. The lamp is very similar in design to a florescent light. UV light is emitted when an electrical current passes through mercury vapor located between two electrodes that are at opposite ends of a tube-like lamp. With a UV light, the lamp is constructed with quartz which allows for 93% of the lamp’s UV light to pass to the outside. (With florescent lights the lamps are lined with a coating of phosphor which lets very little UV light escape to the outside.) Water enters through the bottom part of the ultraviolet light reactor chamber, swirls around the ultraviolet lamp with its protective tube and comes out the top. Exposure of the water to the UV light in the reactor chamber kills the microbes in the water.

The UV Lamps are costly and their productive life is based on the lamp being operated within the manufacturers electrical specifications.

UV light is not only effective, but also very efficient. It can disinfect water at about one-tenth the cost of other treatment methods. The main reason is because the equipment is so small.

As an example a UV light facility which provides 1.4 billion gallons of water a day, would take the space of almost one football field. An ozone facility, by comparison, would require 500 to 1000 times more space. The city, which will need to significantly upgrade its water treatment to meet the new EPA regulations, would save literally millions of dollars on the installation of a UV facility.

 When do UV Lights not work?

There are two main issues with using UV systems, the first is that they turn off under low voltage conditions and then require a long time to cool down before they can restart, thus allowing a large discharge of water to pass through untreated. The second item is when Lamp is continuously fed with a low voltage some lamps operate at a severely reduced intensity. This results in untreated or improperly treated water getting out into the public domain.

Low Voltage

When the electric supply is in a brownout condition (low-line) the intensity of the UV lamps is reduced dramatically. In fact, a 5% drop in voltage results in a 10% drop in power at the lamp (Square law). Any dip in voltage deeper than that will result in unacceptable levels of intensity. This will equate to poor treatment of the water system. Continuous regulated voltage at the manufacturers’ recommended voltage levels are mandatory to ensure the correct treatment of the water supply.

Voltage Sags or outages

If the voltage dips far enough, typically around 65% of nominal voltage for a very short time (35milliseconds), the UV lamp will shut down. It will attempt to restart after the voltage has recovered but only when it has cooled down sufficiently. This can take between 15 and 20 minutes and results in a long period of time when the water goes untreated. There is nothing one can do to speed up this process except to prevent it from happening at all. Using a high speed voltage conditioner provides this protection.

It is very important to have metering on your incoming voltage to capture these sub-cycle events as the most cost effective way to correct the voltage issues is to protect for the problem on that site and not to protect for all and any eventuality.

The solution

In order to reduce or eliminate the EPA fines as a result of these interruptions in water treatment one must install a product designed to correct all types of voltage conditions.

This voltage conditioner must be available in Low and Medium Voltage and be able to perform the following functions:

  1. Correct for deep voltage sags (1-phase up to 80% correction) in less than ½ a cycle
  2. Continuously provide voltage regulation for +/-10% voltage
  3. Maintain voltage balance to all loads it feeds
  4. Reduce voltage harmonics
  5. Be 99% efficient, as every kWh lost is expensive
  6. Have a small foot print, and have an option for storage so that you can get the back up diesel generators online without dropping out the lamps.

Active Voltage Conditioner

Industry today benefits from the performance and efficiencies of modern electronic equipment and because of it automation and computing have entered virtually all aspects of the industrial world.   Such equipment is now critical to process operation, performance and safety.

The correct operation of such equipment is reliant on a well-regulated supply voltage.  Unfortunately, however, the nature of widespread power distribution networks means that voltage disturbances are relatively common.

Utility voltage sags typically occur ten times more often than complete outages and sags often have sufficient magnitude to cause electrical and electronic equipment to trip or malfunction.  As a result, voltage sags have been identified as the most costly of all power quality problems.  Traditional voltage regulation devices such as automatic tap changing transformers lack speed of response, have limited correction potential and usually do not offer imbalance and single phase correction.  All of these features are necessary to protect modern electronics in large industrial applications.

The AVC2 range of high performance, high powered, voltage conditioning products has been designed to provide protection for sensitive loads against these commonly occurring voltage disturbance problems.  The Active Voltage Conditioner is an “active” system that achieves voltage conditioning by injecting an appropriate correction voltage, at the correct phase angle, in series with your power supply.

The AVC2 provides extremely fast voltage and phase correction protecting the load through dangerous sags or even surges.

In addition the AVC2 provides continuous +/-10% regulation of supply voltages, and can eliminate phase unbalance and flicker voltages.

The AVC2 can greatly reduce direct (lamp failure) and indirect (EPA Fines) costs caused by poor power supplies.

Standard Active Voltage Conditioner systems are available as multi-MVA low voltage systems, through to models suitable for direct connection to individual machines.

Custom solutions are built for multi-MVA medium voltage applications.

The AVC can be used for other loads such as Variable Frequency Drives.

How does the AVC Work?

Figure 3: AVC One-line diagram

The AVC2 consists of a voltage source inverter which drives a series connected injection transformer installed in the supply to a load.  It measures the incoming supply voltage and provides almost instantaneous correction voltages for any disturbances.

The AVC monitors the voltage vectors of the incoming supply and injects a compensating vector through the injection transformer to maintain a corrected voltage on its output. Due to the way the AVC corrects the voltage vectors the AVC can:

  • Continuously regulate three-phase utility under-voltages to 90% of the nominal supply voltage.
  • Continuously regulate three-phase utility over-voltages up to 110% of the nominal supply voltage.
  • With an “Option for storage” provide 30 seconds of ride through for complete blackouts.
  • Correction of three-phase utility sags
    • 100% correction from 60% of remaining supply voltage, for at least 30 seconds, model dependant.
    • 90% correction from 50% – 40% model
    • 70% correction from 40% – 40% model
  • Complete correction of single-phase utility sags from 35% to 90% remaining voltage, for at least 30 seconds
  • Correction of voltage unbalance from utility supply
  • Correction of vector phase angle errors created by faults in the supply system
  • Attenuation of flicker voltages in the utility supply.

The Active Voltage Conditioner thus provides the user with a high quality supply, protecting loads from the majority of common voltage disturbances.

Figure 4: Performance results of AVC

The AVC with UV Lamps

The Electrical Power Research Institute (EPRI) performed tests on the AVC at a major manufacturer of UV Systems for wastewater treatment. The intention of these tests was to verify that the AVC will provide the correction desired under certain conditions. The test will verify the immunity protection provided by the AVC.

Immunity Testing for UV Lighting System

EPRI, performed “immunity” testing on a 60 kW three-phase bank of ultraviolet (UV) lights.  Immunity testing results in voltage versus time plots showing the borderline where a piece of equipment will ride-through versus drop-out given a certain voltage and time parameter.  Figure 5 is a sample of the result of immunity testing on several pieces of equipment.

Figure 5 – Sample Immunity Test Result

Typically, immunity testing data is plotted against a known or recognized standard such as the Computer and Business Equipment Manufacturer’s Association (CBEMA) curve (also commonly called the Information Technology Industry Council – ITIC curve) or the SEMI F47 curve for the semiconductor industry.  In this way, multiple pieces of equipment can be tested and compared to each other and these standard curves.  In addition, testing is often performed with and without power conditioning such as sag correction equipment in front of the equipment under test (EUT).  In this case, multiple plots are show demonstrating the effect of the power conditioning equipment versus the inherent ride-through of the EUT without power conditioning.  Figure 6 demonstrates this comparison.

Figure 6 – Immunity Testing with and without Power Conditioning Equipment

Test Setup

EPRI designed and built a 200 Amp sag generator for this type of testing. EPRI has performed very similar testing for many customers in the past in various industries.  Many times, such as in this case, the end user is very interested in the immunity of a specific piece of equipment but in some cases, a “system” is tested to discover weak links.

The sag generator was connected in series with the power conditioning equipment (equipped with a bypass switch) and then to the load bank (UV lights).  Figure 7 illustrates the setup.

Figure 7 – Test Setup

Monitoring

Power quality monitoring equipment was connected at the output of the sag generator and at the input to the UV lights.  This data clearly demonstrated the voltage and time of the simulated events.  This data is then plotted as data points on an Excel spreadsheet plot against the ITIC curve.  Current monitoring will verify the proper operation during the immunity testing but in general, with UV lights, a pass is lights ON and a fail is lights OFF.

Testing is performed with and without the power conditioning equipment in series with the load.  When the power conditioning equipment is not in the circuit, the output of the sag generator and input to the UV lights will be identical but when the power conditioning equipment is in the circuit, the output of the sag generator and the input of the UV lights will be different.  Both curves will be plotted on the ITIC curve.

Variations during Testing

In performing immunity testing on a three-phase load, variables are:  voltage, time, number of phases and phase angle at which the event occurs.  On a real power system, voltage sags and interruptions are random and every one of these variables is likely to be different in every case in the field.  In this controlled environment during testing, we are very careful to change one variable at a time to ensure that we completely understand the response of the EUT given specific conditions that may occur in the field.

Results of the testing

Figure 8: AVC results

Figure 8 shows how the AVC corrected the voltage to protect the UV ballast from the voltage sag.

Figure 9: Deeper voltage sag test for a longer duration

For a sag of 55% for 60 cycles the AVC corrected the voltage almost back to 100%.

Figure 10: All results plotted to show overall AVC performance     

In figure 10 the results have been plotted for the UV lamps prior to installing the AVC. The red line is the point at which the UV lamps and their ballast turned off. After installing the AVC the level of Immunity dropped to the light blue line. This is very large improvement and proved an AVC can provide the desired immunity. If the site has many events below the bottom blue line, an AVC with storage and 30 seconds of blackout protection might be the correct solution.

Conclusions

EPA fines can be astronomical and the AVC has been proven by an independent third party (EPRI) to correct for the vast majority of the voltage fluctuations that cause UV water treatment systems to shutdown and stop treatment of the water supply.

This is a solution that costs less than one single failure for the UV lamps and by using its regulations capabilities will also lengthen the life of the Ultra Violet Lamps.

 References

  1. Intelec 1982. “The Quality of US Commercial AC Power”. Goldstein and Speranza
  2. EPRI PQA 2004, “Medium Voltage Active Utility Voltage Correction – A Case Study”, David Ezer and Robert MacDonald.
  3. EPRI PQA 2006, “Compatibility Issues with Large Scale Voltage Conditioners in Power Systems: “The application of voltage conditioners in power systems is increasing dramatically, but it is important to understand the compatibility issues for the system protection, the system reliability and the system stability.””, Ezer, D. and Penny, J
  4. Web Site: Public Health – Grey Bruce Health unit
  5. EPA “Interim Clean Water Act Settlement Penalty Policy”, March 1, 1995