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INDUSTRY 4.0/SMART FACTORIES
them, they must be detected and diagnosed in the first place. With effective power quality monitoring systems in place, operators can access all the data they need to understand the issue, infer the cause of it, determine how long it has been present, and come up with a solution. While supply side issues can and do occur, many power quality issues can be traced back to a lack of mitigations at the facility, rather than problems with the supply. Solving any apparent mystery always
starts with gathering information, and fault diagnosis in automation systems is no different. Sensor technology, as well as the monitoring systems that can interpret and convey the signals generated, has grown significantly more sophisticated in recent decades. Modern monitoring systems can combine historical, current and trend data to quickly and efficiently diagnose latent, emerging or unexpected issues, but in order to achieve this quickly and effectively, it is advisable to follow established processes, which will ideally have been fine-tuned over some time to ensure that problems are investigated, diagnosed and remedied quickly.
1. GATHER INFORMATION In order to get to the root of any problem, it is vital to gather as much information as possible, and so it is important to have access to the monitoring data. This may seem obvious, but understanding what has happened before is crucial to understanding what is happening now. And furthermore, human knowledge is still as important now as it ever was, particularly when it comes to legacy equipment. Checking with those who know the machinery intimately can also help to uncover issues that have been accumulating.
2. SET UP FOR MEASUREMENTS Once the maintenance team has enough data to move forward, the next step is to take measurements. A problem cannot be fixed until you first know what it is. As such, an instrument that offers a wide range of measurements, such as a power quality analyzer, can be used to help find and fix problems quickly.
If possible, it is good practice to install the
power quality analyzer before switching the breaker back on. Once the tool is installed, be sure to double check all the connections, while considering:
Are the voltage leads connected to the right phases?
Are the current probes connected to the right phases?
Are the probes oriented correctly?
Check the reading on the measurement device - modern analyzers, such as Fluke Reliability’s 3540 FC series of three-phase power monitors, will often have a feature that automatically indicates correct connection. This particular device reliably measures power (A), voltage (V), power (W), frequency (Hz), apparent power (VA), reactive power (var) power factor (PP), and total harmonic distortion / THD (%) as either a mobile or stationary unit. If limits are exceeded or undercut, the system automatically issues an alarm in real time (including via push message on mobile devices). Power supply can also be an issue to consider, particularly if readings will need to be taken over an extended period. Some modern analyzers have the ability to draw power straight out of the measurement circuit, which
removes the need for separate battery power, or proximity to a wall outlet.
3. POWER UP THE SYSTEM Next, reset the breaker and return power to the system. At this point, it is important to look for answers to the following two questions:
1. Is the voltage within the expected tolerance of +/- 10%?
2. Is the current being drawn to the expected range?
The answers to these questions can provide a quick indication of where the problem might be. For instance, if the voltage is outside of the expected tolerance or the current draw is too high, the breaker might trip. Power factor is also a consideration. A power factor below 0.85 is wasteful, and can indicate loading problems. However, this is relatively easy to fix. If the basics are looking normal, check the
total harmonic distortion (THD) – this can indicate that some loads are creating problems. Check the unbalance percentages or look at the phasor diagram on the analyzer itself for voltage and current.
4. LEAVE THE DATA ANALYZER IN PLACE If the above steps have all been carried out and you are no closer to finding the cause of the power quality issues, a further step can be to leave the data analyzer in place so that continuous information can be logged. If the breaker trips for a fourth time, the logger can capture everything that happens both before and after the trip. This can help to provide a timeline of the events and conditions that led up to the trip, which can then inform the correct solution to resolve it.
Fluke Reliability
reliability.fluke.com
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