In this issue:

Waveform of the Month

Please respond to this email address with any comments , questions or if you would like to unsubscribe to this newsletter.

Case Studies Sample Report Conference Call Press Releases Data Sheets

Prescribing unbiased power and environmental solutions since 1995!

March 2008

~ Current, the "New Voltage"

~ Waveform of the Month

~ By viewing the waveform below, you can tell that it is a severe 1 cycle sag that has multiple zero-crossings and can be very damaging to a system since it occurred at 8:43AM.

~ Monitoring voltage is what everybody thinks of when monitoring the power quality. Keep in mind that in order to monitor the power, you must monitor both voltage and current. Previously, when everything was a resistive load, monitoring voltage was the key to understanding what was going on the utility feeder. Today, due to the prevalence of switch-mode power supplies and electronics, you must monitor the current to understand what is going on. Modern electronics draws current in fast pulses, causing voltage waveform distortion. Knowing if the load is causing the distortion or if there are other loads on the feeder is important to understand the total picture of the feeder. Often a utility device (e.g. PFC capacitors) will switch on and cause damage to the electronics but the symptom does not occur for several hours. Why is that? Well, if you monitor the current, you’ll often notice that the system was not used during the time that the damage occurred so that the time of the event is off by several hours. Not having current makes it impossible to know if the events are related.

~ Monitoring current also indicates the affect certain wave forms have on the load. The degradation can be attributed to events that cause a reaction to the utility event. Without monitoring current, these low amplitude low frequency events caused by the utility would go unnoticed. Monitoring the phase current also gives a clue as to the actual loading on the feeder (rather than the theoretical).

~ The last benefit of monitoring current is the benefits you get from logging he ground current. May system cause a slight ground current under operation but tracking the ground current can provide indication of pre-mature failure. Knowing the actual ground current allows for more predicable system uptime. No longer is monitoring only the voltage enough for equipment based monitoring and the real key is to understanding the current flow.