Voltage Dip Immunity of Equipment and Installations

The CIGRE/CIRED/UIE  joint working group C4.110 report on “voltage dip immunity of equipment and installations” is out and can be downloaded from the following link: http://www.uie.org/node/401.

The report summarises on the following:

• Aspects of voltage sag characteristics that equipment manufacturer should account for and test especially during equipment development;
• Recommendations on equipment testing for voltage sags;
• Industrial process immunity assessment to voltages sag problems;
• Proposal for a classification of equipment based on voltage-dip immunity.

A small part of my doctoral research ‘process immunity to voltage sags’ work contributed to this report.

Power Quality Course at University of Manchester

University of Manchester’s power systems group is organising a power quality course between the 25th – 27th January 2010. The course seeks to provide attendees a thorough understanding of major Power Quality issues facing customers and electrical power system operators with substantial distributed generation penetration. The most interesting part of this course will be the presenters’ list, these are some of the finest academics and researchers in the field of Power Quality.

Download the brochure. The document includes course scope, schedule, and presenter biographies.

I have been a student at the university, completing a masters and a doctoral degree, between 2003-2008. Since leaving school  I’ve been in contact with the power system group staff and colleagues at the university. This comes as a surprise to me seeing the group organising this specialised Power Quality course inviting renowned researchers in this field.  Not that the group has’t invited people or has not been visited by top researchers before, but never to my knowledge was a course for 3days like this one. Well done Power Systems group.

Hope the attendees will find it useful. Good luck!

Identifying/Isolating Sources of Voltage Sags Quickly

Recently I’ve attended a Power Quality (PQ) Seminar organised by Fluke in Manchester, UK as part of their Fluke 430series PQ Analyzer promotion campaign. During this seminar, they talked about power quality problems, their experiences in identifying those using Fluke monitors, how they helped customers solve these problems, gave us an hand-on experience in using PQ monitor equipment.

The following are the two quick tips recommended during this seminar on how to identify the source of voltage sags.

• If voltage sags coincides with depression in current flow into the customer’s feeder then the source of voltage sag source is external to customer’s facility;
• However if the voltage sag coincides with increase in load current flow into the customer’s supply feeder then the source of voltage sags problem is within the customer’s facility.

Principle:

Typical causes of voltage sags due to external utility are faults and switching on/off of large loads (induction motors etc.) at the utility network or at the neighbouring customer’s facility connected to the point of connection (or supply) as our customer. In this case, the cause of voltage sags is due to large voltage drops across circuits caused by large currents drawn during system events (faults, sudden connection of large load etc), and our customer’s facility as a result will receive reduced current. Therefore for external causes of voltage sags, the voltage sags coincide with depression current consumption in to our customer’s feeders.

On the other hand, the same system events (faults etc.) when arise within our customer’s facility, then large currents are drawn by customer’s supply feeders causing voltage to depress, and thereby having increased current consumption coinciding with voltage sags.

The above voltage sag source detection logic is simple, yet has hugely practical implication in isolating the problem quickly.

There is also considerable amount online resource available on various power monitoring and application aspects at the Fluke UK Application Notes section. Hope you will learn something new here having thoughts like: ‘Hey! That’s interest and useful, I didn’t know that before.’, or feel good at heart thinking ‘Ah! I knew that and I could teach some folks perhaps’. However you feel, hope you will have a good time perusing through them.

Have fun!