Interpreting The Readings

"Becoming the Power Quality Specialist / Consultant"

Here we tell you a few secrets of what makes others a lot of money. In the event you think it's extremely specialised, don't. Interpreting power quality issues is a lot more logical than many want to have you believe (because that's how they make their money!). The instruments available on the modern market make it possible to become seriously involved in power quality overnight.


The Quick Buck: (a warning to customers!)

The crunch! The fact modern instruments and recorders are that much easier to use has attracted what can only be called "cowboys" into the PQ arena.

Power Quality requires solid electrical and electronic knowledge and experience. It defies belief when stories fill the papers of technicians suddenly being adept at PQ after purchasing the latest whiz-bang instrument to hit the market. Pulling a fancy piece of kit out of the bag does not reflect a person's ability in any way whatsoever.

There are only a few real PQ specialists throughout the world (let's just say I would not run out of fingers counting them!). If you're looking for someone to do a bit of PQ sniffing for you, do your homework so you too don't fall prey to the specialist con artist!

Be exceedingly wary of the "free power quality survey" as these are more often than not 'offered' by makers or distributors of some or other power anomaly mitigating device. Here it's "buyer beware". There ain't such a thing as a free lunch! Question everything they tell you. Challenge their findings. And ask for a written statement of the problem before adopting their (obviously slanted) recommendations.

If you have any doubts, get a second opinion from a genuine qualified source. I have lost count of the times I have been called in to verify findings (usually the reports are very biased and therefore seriously flawed - c'mon, they want you to buy their kit, don't they?). Though this may cost a little money, it could well save you even more!

Lest you think I am against the "cowboys", please don't. The only issue I have with them is their potential to bring the PQ fraternity into disrepute through their customers parting with hard earned cash along the way yet yielding little or no results. Other than that, they are of service to me as they are the very crowd boosting my business as I have to go in after them and fix what they fouled up!

As a customer, this section will offer at least a means to verify the content of the report you've been given with regards your power (it cannot, however, verify that the issues in the report were recorded from your power!).

A few pointers...

Able to perform a survey does not a PQ specialist make:

The pressure placed on major users of electricity by the likes of G5/4 (permitted harmonic content) has seen an increase in companies (usually small) who offer harmonic survey services. It sure does not take long for an owner/user of a PQ instrument to learn how to perform a recording of the power and have the software spew out a reasonable looking report.

An example: "A non-engineering type is rather confident in his ability to quickly and cheaply determine and solve power quality problems (harmonics, grounding, transients, etc.). He sells this ability to cure a customer's problem for ±US$1000. His technique is to borrow the RPM Portable Power Recorder, collect a few minutes of data, and give some graphs to the customer.

There are literally hundreds who can perform such services. It does not take much experience to determine the harmonic content of a site. But this is not the end of the story!

"However, there is a wonder why the problem continues to exist. He asks a more learned colleague to review the limited data, but the wonder grows when the colleague does not have a solution (on limited data!). The final insult is he asks the colleague to step in and save some face! Full PQ Investigation proposals can reach US$3000 to $5000. The usual result is the customer walks away because they've already been promised a solution with the original price."

It takes extensive experience to notice small but significant issues within a recording, and more so when needing to propose solutions. These hundreds of concerns offering "PQ survey services" are putting the companies that employ them at an inordinately high risk!

The Starting Point:

Knowing the instrument and its capability is only the first requirement. The next is the need to understand the subtle but all important difference between a Survey and an Investigation becomes paramount. The difference is:

Survey:- This is done to obtain trend data for existing or the planning and implementation of further loads or the upgrading of a network.

Investigation:- This is the study of a network's quality to ascertain the potential impact on, or the cause of a client's already present annoyance, loss of productivity, and/or damage to equipment.

As said earlier, the former is simple. Ability to do the latter can only be achieved with a long road of experience and one that must be travelled before a person can adorn the label of 'PQ specialist'.

It's specifically when only half the story is known that things become a little tricky. Instances such as when the voltage and current disturbances don't coincide that one needs to ask whether or not the fault is internal or external to the site. But again, applying a little logical thought often provides the answers.

Many look to the voltage to ascertain the fault or power quality issue. One should rather investigate how the current reacted to the change in voltage, being especially careful not to discount any changes in the current causing voltage fluctuations.

When it comes to interpreting results there are some products that have software that writes the report for you. But herein lies a another little word of warning. It is becoming more evident that people are starting to rebel against the "automatically generated" report as it has no means to make decisions. The programmers err on the side of caution and merely present the recorded data in a compact form. It may be fine for a survey, but does not help in an investigation.

And So...

It has hopefully become evident that just because somebody has an electrical engineering degree and a power quality analyser does not make them qualified in power quality issues. A wrong diagnosis can cost shed-loads of money and downtime.

The fundamental requirement to being a power quality specialist is to be a superb all-rounder with many years experience in various disciplines. The moment there is any speciality in just one field, power quality issues are going to be exceedingly difficult to trace.

Being previously involved with IT, having good knowledge of LANs, routers, switches, and servers, will not stand one in good stead trying to determine a power quality issue on a process control system where 4-20mA loops are being affected. Vice versa is just as true. A true PQ specialist can work in all spheres!

We start this section with a very important rule. "never dismiss a thing!" and continue with "Don't Over-Analyse".

Once we have the basics out of the way, we start having a look at what the intruments are trying to tell us, and work our way through to some captured faults. We then complete the tour with a section on "presenting the findings".

Never Dismiss a Thing!  >>

The data and screenshots in this section have come from my own client archive.
Names and site details have been removed for obvious reasons of maintaining privacy.

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© 11.03.04