If you have worked in the electronics or information technology fields for any length of time, you have probably blamed power fluctuations for causing problems to your systems. Most of us have heard the urban legend about the computer that crashed around the same time every evening and the clever technician-hero who discovered that it occurred at the same time the janitor plugged in a vacuum cleaner on the other side of the wall.
Poor electrical power quality is easy to blame for problems you are experiencing with your organization's IT systems because most people don't know much about it and aren't responsible for its generation, distribution, or the natural or human events that cause disruptions.
But once power quality is cited as the culprit, the IT professional often has to take action. To help you get started, this article will provide some basic information about electrical power quality.
To conduct a power quality study, you need a power quality analyzer for testing the integrity of electrical power distribution systems and for locating faults.
The analyzer will give you the ability to validate power quality coming from your supplier; detect problems external and internal to your room or building; help categorize and diagnose problems; uncover hidden or intermittent issues; verify electrical system capacity; and measure energy usage.
The Fluke 430 Series Power Quality Analyzer, AEMC 3945 Power Quality Analyzer and the Dranetz-BMI Power Quality Analyzer offer the features for a comprehensive power quality study and cost under $10,000.
Surface Combat Systems Center (SCSC) in Wallops Island, Va., uses the Dranetz-BMI PowerVisa 440D with Dran-View 6 software (DADMS ID #49679).
But a word of caution: Power analyzers and other electrical test equipment should be connected by a certified electrician.
Resolving the Problem
There are four steps to satisfactorily resolve your power quality problems: planning, monitoring, evaluating and mitigating. Don't bypass the first three steps because they are as important to successfully mitigating power quality problems as properly preparing a surface is to a satisfactory paint job.
If you suspect a power quality problem, carefully plan where to connect the analyzer. SCSC has two analyzers which are often used in pairs. One is located at the electrical panel closest to the equipment experiencing the problem, and the other is located closest to the source of power for the building. You may be surprised to learn there are more power quality problems generated inside your building than coming from the source of electricity.
After connection, install the memory card and set up the instrument configuration. The monitor we use provides automatic, wizard, upload or manual setup options. Use the automatic setup option and then check the analyzer phasor diagram to make sure the electrician connected each probe to the corresponding A-B-C neutral leg.
To capture intermittent events and collect enough data for analysis, we recommend 60 days for power quality studies.
During the collection period, the technicians need to keep a log with the date, time and description of equipment problems. This will help focus the data analysis effort. Data are recorded on a compact flash card. A 256 megabit compact flash card will hold approximately 30 days of data. If the card fills up in a day or so, you probably have installed the unit incorrectly.
Once you have collected enough power quality data, it is time to analyze it. The analyzer software allows you to view the information as event lists, graphs, or you can create custom reports.
We initially run a report that summarizes all disturbances by category and magnitude. If we find measurements outside industry standards or customized limits, we compare notes and any other available