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Product category: Electrical and Electronic Testing and PAT Equipment
News Release from: Dranetz-BMI | Subject: Power quality monitoring systems
Edited by the Engineeringtalk Editorial Team on 22 June 2006

The case for power quality monitoring

Selecting a power quality monitoring system requires energy but offers significant payback.

In its purest sense, power quality monitoring instrumentation can be compared with a home security system If a home doesn't have one, there's a chance that consequences may never be suffered

However, in the event that a situation does occur and there's no alarm system in place, the consequences could be grave.

So which scenario is worse: having the insurance and not needing it, or not having it and potentially subjecting your family to a dangerous and potentially disastrous situation?.

Power quality monitoring is no different.

If you have it but your business never experiences a power shortage or sag, there is still the peace of mind that comes with knowing your operation is protected.

However, in the event that a power event does occur, the investment you've made in the instrumentation can certainly be justified by the damage you may have prevented to your business operations.

What's more, given that the cost of power quality monitoring devices has decreased significantly over the past decade, the investment has become far less severe and the return on the investment much quicker.

Modern power quality monitoring systems also provides the added benefit of simultaneously monitoring demand, energy and other parameters greatly increasing their value and benefits to the user.

So you've made the decision that power quality monitoring is a worthwhile endeavor.

You've also determined that for a myriad reasons (ie being proactive, constant system vigilance, larger database), permanent monitoring will serve your purposes better than portable monitoring.

What now?.

The following guidelines should be followed when structuring a permanently installed power monitoring plan.

The first, and perhaps most crucial step, is deciding where and what to monitor.

One of the most popular places is the utility service entrance where power is fed to the facility.

Typically, the utility company is not fully aware of the quality of power that they are providing.

Monitoring the supply they're feeding you is an effective way to have a figurative leg up on the utilities.

In fact, customers have often been able to prove utility failures and recoup losses to equipment and operational downtime thanks to a carefully designed monitoring system.

Generators can also be monitored, as can the switches that transfer the source of power between the utility and the generator.

And, in certain facilities where computer usage is particularly critical (such as data centres or banking centres), there are often uninterruptible power supplies (UPSs) that not only supply power to the computers and other machines, and help negate the effects of voltage fluctuations or other problems unrelated to power.

The system acts as the referee and ends finger pointing by providing quantitative information as to the source of the problem.

A UPS is not guaranteed against failure though, so monitoring the input and output of this device can be very beneficial.

Monitoring the UPS is also a guard against non-power-related situations, such as server reboots caused by malfunctioning operating or other problems unrelated to power.

Next, there are what might be termed second tier locations where power quality is not a burning issue, but where measuring demand and energy might be sensible.

In less critical operations, there may still be one specific process that is important enough to require monitoring - perhaps in a semiconductor fab or other manufacturing and production lines.

These processes can be individually monitored as needed.

In order to choose an appropriate power quality monitoring system, there are a number of factors to consider.

Naturally, compliance with the latest standards is a fundamental concern with the most highly recognised standards being IEC61000-4-30 and, domestically, IEEE1559.

Although not required in the USA, Class A compliance with IEC61000-4-30 indicates the system provides reliable and repeatable measurements that can be trusted.

Obviously, simplicity of operation is an essential element, but even more important is that the instrument incorporate a web browser interface that can be used with any standard browser such as Netscape Navigator or Microsoft Explorer.

The upside of the Web browser interface is that it allows a number of users to share power quality information without costly dedicated workstations or user licenses.

This network is particularly crucial should a power event occur, as it will ultimately lead to quicker problem resolution.

Given that in most mid- to large-size data centres, the building owner, electrical contractor, and one or more consultants are most likely to deal with an issue, having simultaneous access to this information is a huge advantage.

Let's face it, you don't usually see rogue users hacking into power quality systems.

Regardless, just having a password protected system so that personnel who don't know what they're doing will not cause problems or subvert the system is a good approach.

Therefore, it's a good idea to choose a system that supports basic security features such as a username and password to enter the system.

Permanent power quality monitoring systems can record a lot of information that can be viewed by many users.

Because more than one computer is generally used to collect data remotely, the Internet is by far the most efficient and cost effective technology available for connectivity.

If a company is utilising old serial technology such as RS232, it is likely that they are also using older, outdated instrumentation.

Ideally, a newer system will have very flexible communications and will work on both hard wired and wireless Internet systems.

Many long-time users of power quality systems are familiar with the procedure of browsing data on a regular basis and performing timeline trends, event lists, and other reports by interrogating the system to determine if any events had occurred used to be standard operating procedure.

Systems now are capable of providing the end user with data automatically via e-mail, cellphone, or pager that pushes important information to the users.

They can still be proactive if desired and manually interrogate the system, but the need to be "eternally vigilant" is essentially eliminated.

What's more, notifications can be set for different sensitivity levels with the delicacy of the data dictating the notification.

The oscillating wave shapes that basic systems record are of little use to anyone who is not an electrical engineer.

A system that can characterise data with no need for complex interpretation is a major plus, allowing users of all levels to recognise and understand a power event.

This simplicity is especially integral to the concept of directivity - that is, being able to identify the exact location of a problem.

For example, when a problem is detected from a device positioned at a service entrance, it is important to determine if it is an "upstream" problem, for which the utility is responsible, or a "downstream" problem, which falls on the user.

This applies to other locations within the mentoring system.

In any reasonably large organisation there are information technology (IT) concerns.

If you intend to access the existing network when connecting the power quality instrumentation, you should work closely with the IT department.

It may be a simple act of courtesy, as the instrumentation rarely interferes with network performance, but it also ensures that the devices enjoy the network's full connectivity.

It is also possible to create a separate network for the instrumentation, a much easier task than in years past, given the availability of functional and user-friendly network products sold at retail electronic outlets.

Safety must be the first consideration in any monitoring installation.

Qualified personnel should spearhead this task, with full attention paid to local and national codes, as well as any corporate requirements.

For a licensed electrician, whether in-house or contracted, the job is not particularly difficult, perhaps a four on a complexity scale of 10.

Typically, there are two types of connections to be made: one for voltage and one for current.

The voltage connection is a straightforward task, requiring simple direct wire connections.

The optimal choice to make these connections is an instrument that does not need transformers or other ancillary equipment under 600V.

Current connections present a bit more of a challenge, as they require a special sensor or current transformer.

Further, there is an issue as to whether the connections can be made "live" (power on) or "dead" (power off).

A dead connection that allows for disconnecting the wires can use much less expensive current transformers and is far less expensive, but the idiosyncrasies of the specific business may preclude this option.

The cost of the connection also rises substantially when clamp-on current transformers are employed - sometimes 10 or 20 times more for an individual component.

If existing current transformers can be used in piggyback fashion, a substantial savings in both time and money can be realised.

Whether it is the supplier, installer, or outside consultant, someone has to shoulder the responsibility of ensuring that the installation was completed correctly, and train the system users.

Regardless who takes this task, it is an installation aspect that should be addressed early - even before the system is purchased.

Once the instrumentation is installed, users must determine how they will use it.

Will they employ a reactive approach, allowing them to go back in time to see if an event occurred?.

Or will they be more proactive, allowing them to determine if something is deteriorating and may become an issue in the future and require corrective measures?.

What happens if and when there is an actual power problem?.

Is there in- house expertise that can diagnose the predicament?.

Are there measures to mitigate the problem?.

Knowing in advance who to call if a problem arises can greatly reduce the time to get back up and running.

Typically, power quality monitoring instrumentation requires no maintenance other than yearly calibration.

For companies that are ISO9001 certified, calibration of all instrumentation is a requirement; consequently, the monitoring devices will fall under that aegis.

The majority of reputable instrumentation manufacturers offer such services since many businesses don't have internal resources to perform the calibration.

While calibration should certainly be on the corporate "to do" list, it is not the most critical matter when it comes to power quality monitoring.

Many of these devices are extremely accurate, and should one be a bit out of whack, performance will not be significantly impacted.

However, annual calibration ensures the continual health of your system and reliability of data.

It is evident that the selection of proper equipment for power quality monitoring requires a significant amount of time, energy and education.

Yet given the ramifications of having the wrong system or no system at all, it is just as evident that it is time well spent since you will live with your choice for years to come.

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