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Product category: Manufacturing Information Technology systems
News Release from: Dranetz-BMI | Subject: Power quality monitoring
Edited by the Manufacturingtalk Editorial Team on 03 May 2006

Installing power quality monitoring

Energy spent on installing power quality monitoring pays off in industrial and commercial environment.

You've just experienced a power outage in your house It lasted just one minute, so it was over before you even noticed it

You see that the clock on your VCR is flashing, so you reset it.

You see that the clocks on your microwave and oven are also flashing, so you take care of those as well.

Other than the few minutes it took to reset these devices, you've come out of this power "event" relatively unscathed.

Now consider the same scenario at a chemical processing plant.

You're processing a plastic formulation, and it is in the molten or liquid state.

Then the power outage hits, and the entire line shuts down.

The plastic stops flowing.

Although the power comes back quickly, you've got a mess on your hands.

You've lost a large amount of costly raw material.

Worse, you' ve got to perform a full cleaning of the machine and the pipes to extract the suddenly rock-hard plastic.

It's a time-consuming, costly chore.

And you can't start the line back up until the cleanup is finished, meaning a serious loss of productivity.

It's clear from these diverse examples that while there is virtually no call for monitoring power quality in a residential setting, the need to do so in industrial and commercial settings is critical.

If continuous voltage and current is not available, equipment might stop working, in turn affecting the entire production process for which the electricity was being used.

The consequences, financially and otherwise, may be far-reaching.

As machinery has become more sophisticated in recent years- specifically due to the widespread use of microprocessors - the ramifications of poor power quality have grown substantially.

Even a minute drop in voltage can render the microprocessor ineffective.

A vast amount of industries depend on microprocessor-driven equipment.

For one, data centers, with their high volume of computers, are certainly a primary target.

Healthcare, which relies on sophisticated diagnostic and treatment apparatus such as MRIs, X-rays, and dialysis machines, is another.

Manufacturing is in the same boat, given how many machines are now governed by programmable logic controllers (PLC's), and auto assembly lines are a case in point, with PLC-driven robots at virtually every phase of production.

Power quality fluctuations can affect the ability of all these devices to work correctly; it can even trip them off-line and shut them down.

Interestingly, the susceptibility of computers to power fluctuations, more than any other device, is related to the unique nature of the industry.

Because of the ongoing struggle to produce computers at the lowest cost possible - which can subsequently result in highly competitive pricing at the commercial and retail level - manufacturers over the years have removed a capacitor here and there to save a few pennies.

These small savings per unit, multiplied by the staggering number of units that are annually sold, add up very quickly.

However, the quest for savings also results in a less robust device, one that is far more susceptible to power quality fluctuations.

As a result, new SEMI -47 and ITIC sensitivity curves have been developed by industry to address these issues.

There are two types of power interruption.

The worst, of course, is a blackout (like the 2003 surge that encompassed a large portion of the northeastern United States).

At the other end of the spectrum is voltage sag, which is defined by the IEEE 1159 standard as a 10% drop below normal voltage levels.

In terms of consumer products, a 10% drop in voltage would cause the clock on your VCR to go out, and then re-set.

Again, the consequences in this instance are relatively minor for a residential setting; however, they are far more devastating in an industrial setting.

The need to monitor power quality in the industrial and commercial areas from the point of generation through the point of use is unquestionable.

But the value of monitoring goes beyond reacting to a specific event; there is a proactive, preventative element as well.

With proper monitoring, the user can examine what happened in the power circuit, and determine where the problem occurred and, with some analysis, pinpoint the source of the problem.

Perhaps a large motor starts up and draws a lot of current, which reduces the overall voltage available and causes the equipment on the same circuit to succumb to the voltage sag.

If that situation can be recognized through observation of past event information, the cause can be detected, and preventive measures can be taken.

Possibly, the way the motor is started can be altered, or other critical devices can be removed from the same circuit so they won't be affected by the sag.

Voltage fluctuations can also be remediated by the use of Uninterruptible Power Supplies (UPS), as well as surge protectors in the event of lightning strikes or surges.

If it is determined that the problem is being caused by the electricity supplier, the supplier should be contacted immediately.

Having, evidence of a problem really helps in getting attention from the utility, which typically have ways of improving their voltage quality through the use of voltage regulators and capacitor banks.

Once the decision is made to engage in power quality monitoring, another issue must be addressed: whether to implement a portable monitoring or permanent monitoring system.

While portable monitoring can be effective, it carries certain drawbacks: If a power problem is suspected and a portable monitor is applied to the circuit to track the problem down, the procedure will be ineffective unless the problem occurs again while the monitor is in operation.

It's not unlike bringing your car to a mechanic and praying he'll hear the same noise you heard the day before.

The database of information captured will be relatively small; thus, it may not be of much help in terms of predicting power events over time.

If there is a minor problem that is easily identifiable, i.e., a faulty transformer or a groundswell because of a temperature change, a portable monitor can be effective.

However, the troubleshooting nature of portable monitoring makes permanent monitoring a far better solution.

To begin with, permanent monitoring ensures that power quality is being chronicled 24/7.

If a problem occurs, it will be recorded for easy identification.

Secondly, permanent monitoring enables users to build an extensive database of event information, allowing the tracking of trends over a long period of time.

This factor is critical in facilitating the creation of a sound preventive maintenance program.

The quandary of voltage "lows" that occur when equipment is added to an operation and efficiency dips on a motor because of increased harmonic levels can be virtually eliminated with the aid of permanent power monitoring.

Clearly, there are a number of benefits that accompany choosing a permanent monitoring device over a portable one.

However there are a number of permanent monitors available on the market today, so it's important to take a number of factors into account when specifying a permanent monitoring solution.

When considering the optimal permanent monitor for an industrial application, there are a number of factors that should be examined.

It is quite rare in the industry, but there are devices that will capture events triggered by both voltage and current: most devices will trigger on voltage only.

Obviously, dual functionality translates to a more flexible, accurate and reliable instrument, especially in cases where a transient voltage surge suppressor (TVSS) is employed to cap voltage.

Some monitors employ a web-based browser environment, allowing multiple users to view and share the same information simultaneously.

In an ideal situation, a plant engineer, plant manager, and utility operations person can all be analyzing a power event together, increasing the chances of a quicker resolution.

The value of a user-friendly interface should not be underestimated.

By utilizing sophisticated software, a quality instrument can present information in a way that allows non-technical personnel to understand it without extensive interpretation.

The software should be able to analyze the wave patterns and display and relay the exact nature of the difficulty to the user in simple, readable fashion.

Intelligence is another element of a quality system.

In most utility distribution systems, capacitors are used to maintain constant voltage.

These are typically switched in at some pre-designated hour of the morning.

Superior instrumentation can recognize these capacitor-switching events and can locate what direction they came from.

This capability is also helpful in pinpointing the source of fast voltage and current transients.

When voltage sag occurs, it's not uncommon for the utility to believe it happened on the customer side, and vice versa.

By positioning a reliable permanent monitor on the point of common coupling - the spot where the utility connects to the facility - the monitor can, in an independent and unbiased manner, locate the event source.

Because each user has a different power-monitoring requirement, modularity is a vital feature.

Users are looking for systems that they can configure themselves based on their individual needs.

Traditional instruments are equipped with four voltage and four current channels.

The highest level of configurability is available in instruments that offer the choice of voltage, current and data acquisition modules to build from one to four (or even more) virtual instruments in a single, compact format.

By combining four modules in one instrument for applications that previously required two or more instruments, users will save money, prevent integration aggravation and gain physical space.

It goes without saying that compliance with the latest standards is an essential ingredient for any power quality instrument.

The key standards include IEC 6100 4-30 Class A instrument and, domestically, IEEE 1159.

In the end, the use of power quality monitoring can be equated to an annual physical.

Essentially, what is tested and measured from year to year is consistent, but as age, lifestyle habits and conditioning change, so do the parameters of the appointment.

Predictive maintenance based on trended values and events can be employed to anticipate or prevent health problems.

Likewise, continuous monitoring allows users to monitor the performance of the power system, and the frequency of power quality events, to develop a database from which long term system health can be predicted and preventative maintenance steps initiated.

At that point, the device becomes invaluable.

Like a yearly physical, monitoring equipment can carry a substantial cost.

But the cost of not having it - regardless of the type of industrial or commercial environment - can be sky-high.

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