In this category, it should be possible to expand specialist knowledge. These include topics such as new standards, new products on the market, etc.

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Project study: Resonance suppression through a special active filter

Problem description

After installing a second photovoltaic system on a low-voltage grid with a high proportion of inverters, frequent faults were detected in the first and larger solar system. The inverters of this system, but also of the newer PV system, frequently switched off with the message “grid fault”.

During a grid quality measurement carried out by the local power supply company, high voltage distortions and exceeding of the limit values according to EN 50160 as well as EN 61000-2-2 could be determined at times. However, no cause was given or determined.

Since a CHP unit with a higher output is to be connected to this network and further disturbances were to be expected, we were commissioned with a network and harmonic analysis. The goal here is always the clear determination of the cause and the subsequent planning of suitable solutions.

Approach and analysis

First, we obtained an overview of the overall situation of the voltage supply by measuring with a special network analyzer. Already after connecting the first measurement to the transformer infeed, very high voltage distortions were detected (see the following picture of the voltage and current waveform).

Voltage distortions

Since this is a customer-owned grid, we applied the limit values of EN 61000-2-4 class 2 for the evaluation of the voltage quality. Of course, these limits were also exceeded, in some cases very significantly in the case of individual harmonics and interharmonics.

Two causes are already evident in the current and voltage waveforms. Firstly, the grid is almost exclusively loaded with 6-pulse converters (typical for frequency converters). And secondly, a clear resonance oscillation is recognisable. The latter can usually be seen as the main cause of fault messages from sensitive or particularly protected electrical equipment, such as solar inverters.

Parallel resonance arises as an interaction between transformer inductance and capacitive components in the low-voltage grid. In most cases, these are distributed over several systems and therefore cannot be specifically eliminated as the cause of the problem. During further measurements in this network, we were therefore able to identify several feeders that are involved in the resonance. On the one hand, these were mainly lighting systems and, on the other hand, the disturbed photovoltaic systems. In both cases, the use of unchoked or only slightly choked capacitors as main or filter components is typical. Thus, the disturbed system components are also involved in the disturbance itself. In addition, there was also a frequent shift of the resonance frequency, the cause of which was the switching on and off of the components involved.

The solution

Therefore, there were only two possible solutions. The first way would be a comprehensive restructuring of the network and therefore very time-consuming and expensive. The second way turned out to be feasible in the short term and was preferred by the customer.

As a short-term solution, a special active filter was installed and parameterized by us. Selection, installation, and commissioning were carried out in close cooperation with our customer and the supplier of the filter. The objective was to eliminate the resonance oscillation as the cause of the inverter’s fault messages and also the greatest risk of faults in the CHP to be installed later.

The results are clear:

At the time of commissioning, the resonance was not so pronounced. Therefore, the voltage in the image without the filter is also less distorted than in the first image. Nevertheless, the installed filter also caused a permanent and reliable suppression of the resonance oscillation in the course of the verification measurement over two weeks.

The remaining voltage distortions in the right picture are due to the frequency inverters and contain only slight exceedances of the limit values according to EN 61000-2-4. These do not lead to disturbances at the solar inverters but can be reduced to below the limit values by an additional filter if necessary.

All the systems, including the CHP unit that has since been put into operation, have been working trouble-free since the filter was put into operation.

Imprint:
PQ Professionals GmbH
Landsberger Street 4
04157 Leipzig
represented by the Managing Director Dipl.-Ing. (FH) Frank Strobel

 

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Towards condition-based maintenance

Intro Energy transition and climate neutrality

Before we get to the topic of “towards condition-based maintenance”, here is a higher-level digression. Namely, discussions about climate neutrality have reached a new evolutionary stage. This means that nations are actually addressing it extensively politically. Whereby it is also clear that the competence of political intentions is not reflected in the feasibility of time and technology. However, and this encourages me in this discussion, companies are extremely technologically involved in change. Not to show their charity, of course, but to develop growth-oriented and profitable business models from it. Be it decentralised and renewable energies, e-mobility or the complex issues of a smart grid.

The motivation of towards condition-based maintenance

One thing is certain about all climate neutrality projects: we need a lot more electrical energy. This means that in addition to the many known decentralised generators, other types and systems will also be added to a) ensure security of supply and b) protect against a blackout. For both, for example, the VDE ETG ITG technical committee is currently discussing modern and flexible cellular energy systems.

But the focus is not only on the supply of more energy, but also on the reduction of existing consumption. All this in order to improve the CO2 footprint. ISO50001 helps to achieve this, and in Germany, among other countries, it formally calls for energy saving with subsidies. And this is precisely where the topic of “towards condition-based maintenance” comes in. Incidentally, it could also be called “future-oriented maintenance”. You can read why here.

Why maintenance at all?

Here I briefly explain why maintenance makes sense at all. Of course, I make no claim to completeness, as with all the other paragraphs.

  • To guarantee production reliability and avoid breakdowns as far as possible
  • Extend the service life of the equipment
  • Improve cycle times and thus efficiency
  • Ensure the quality of products
  • Not to impair downstream components
  • etc.

Some key basic problems in maintenance

Already with predictive maintenance, the topic begins to struggle with itself. Namely with the aspect of “looking ahead”. It is often the case that you cannot see inside a system or a machine. Unless the hydraulic oil is already dripping onto the floor. As Mr Pirmin Cavelti of Gubser Service put it: “You can’t really see inside. And just from holding your hand on it, like a glass ball, it doesn’t necessarily get better.”

And why the idea of towards condition-based maintenance?

Manufacturing companies in particular can sing a song especially well: Shortage of skilled workers. Finding suitable personnel for demanding technical and manual jobs is becoming more and more of a tragedy. While these types of professions are attractive in principle, they naturally do not correspond to trendy studies or ITC careers. Furthermore, it has been observed for a long time that plants are being pushed to the limit more and more. One exception would be compressors – but we’ll get to that later.

For the sake of simplicity, I will list a few more reasons that may favour the topic of “condition-based maintenance”:

  • Scarcity of resources for wear material due to the current COVID shortage
  • Maintenance is shown as a pure cost factor in the P&L and not seen as a benefit
  • Lack of or inadequate maintenance strategies
  • Rapidly increasing digitalisation in all areas
  • CO2 reduction with national energy strategies
  • Measures versus results (lack of “fitness coach”)
  • Reduced cost budgets to secure and increase margins
  • Demand for more documentation and evidence
  • Trend towards number orientation and balancing in “extra-monetary” areas
  • etc.

Possible solution parameters for condition-based maintenance

If we now look at examples of motors that are used to drive something or to generate something, we can draw on informative parameters. These already indicate the current “state of health” of a drive system. These would be, as always not conclusive, as follows:

  • Temperature
  • Vibration
  • Cavitation
  • Electrical quantities
  • Ultrasonic
  • Humidity
  • Existing historical values
  • etc.

If these parameters are now considered in a permanent context, i.e. as a whole, completely new insights can be gained. Specifically, we already know the individual parameters that make up a “normal” operation. If you now apply various limits and threshold values to all parameters, you can visualise the state of the system in a short time and, if necessary, intervene at an early stage. Or vice versa. Instead of intervening at intervals, you can see the actual state, whether it would be necessary at all.

Temperature and ultrasonic as important indicators

The temperature on motors, bearings, etc. as well as the measured ultrasound in dB on bearings, shafts, gears, etc. provide important information. For example, the ultrasound value changes upwards, i.e. it becomes louder, targeted and dosed lubrication measures can be carried out. If the dB value is reduced, the lubrication has a positive effect. Does the value increases during lubrication, overlubrication could be the cause. If the dB value continues to increase permanently, this could indicate a defect in the near future, which could also be seen as a symptom in the rising temperature.

Electrical values as very useful additional information

Here, you as a maintenance engineer and operator have the opportunity to save energy by intervening at an early stage. This can be seen very quickly by recording the electrical characteristic curves. With their help, increased and reduced KW/h can be expressed immediately in money and CO2. In addition, trends can be derived from the electrical parameters, such as when which power consumption takes place, which efficiency levels the motors have and how they change, etc. Even grid-specific phenomena would become visible, e.g. harmonics, transients during switch-ons or switch-offs, interruptions, etc. Furthermore, you would already be able to find out in which load behaviour your drives usually are. This is particularly interesting for compressors whose (non-)generated compressed air costs the operator enormous amounts of money.

And now imagine that all this would be integrated into an energy monitoring system in your company – i.e. absolutely scalable for all company areas and their infrastructure. Not only for maintenance.

What could such a system look like?

To simplify matters, I’ll let pictures speak for themselves here.

Towards condition-based maintenanceTowards condition-based maintenance with gears

Towards condition-based maintenance at bearings

Barriers to condition-based maintenance?

In the interest of fairness, however, we should also address the elements that are less favourable to the issue of “condition-based maintenance”. These would be as follows:

  • Saving energy means technical as well as HR-intensive initial effort and requires investment
  • Investments have to be approved and are anchored in the annual budget
  • Electricity costs (KW/h) are too cheap in many countries ≠ Energy saving
  • Repairs are usually not investments and easier to approve (forced investment)
  • Predictive maintenance at time intervals is easy and can be planned well
  • etc.

Conclusion of condition-based maintenance?

In summary, we can say that the topic of condition-based maintenance can generate the following benefits:

  • Matching motors to drives (efficiency)
    Damage detection
  • From predictive maintenance to condition-oriented and thus future-oriented maintenance
  • Recognising if and when problems are imminent
  • Maintenance is only carried out when the condition indicates the need for it
  • Logbooks, documents and records are automatically digitised.
  • Automatically contributes to CO2 reduction
  • ISO50001 compliant
  • PEX and OPEX are automatically reduced
  • The whole system is scalable – ROI is fast.
  • There is no need for a maintenance strategy for the objects in question, as this is automated
  • Sustainability and resource conservation are positively influenced
  • The data can be balanced
  • etc.
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Electrical data security

Data center data security reliability depends on many different factors. For example, from the energy supply and operational reliability of the power supply. This is what we refer to in this blog as electrical data security. Electrical data security conditions must be constantly monitored to achieve Tier 1 – 4 levels. It is advisable for you to monitor parameters of power quality, energy and fault current detection as well as cyber security together.

Figure 1: https://www.hpe.com/ch/de/what-is/data-center-tiers.html (31.1.2020); Source: Camille Bauer Metrawatt AG (own design)

Electrical data security and the problem

Various studies have shown that poor network quality causes costs. These run into the billions every year. As early as 2007, the Pan-European LPQI Power Quality Survey estimated that the damage amounts to the equivalent of $150 billion annually. In the meantime, the challenges this poses for everyone have steadily increased. And that’s especially true for data centers.

The basic requirements for a data center

There are many requirements to consider when planning the power supply for a data center:

  • Secure location in terms of energy supply and environmental conditions
  • High energy efficiency to minimize operating costs
  • Maximum availability due to redundancies (UPS, generators)
  • High security (fire protection, access, defense against cyberattacks)
  • System stability and reliability of the devices used
  • Possibility for later expansion
  • Compatibility with the standard e.g. according to DIN EN 50600,etc.
  • etc.

Possible solutions for electrical data security

1. investment protection through good power quality (PQ)

Figure 2: Power quality simplified; Source: Camille Bauer Metrawatt AG

2. system protection by residual current and fault current monitoring

The risk

Residual current monitoring (RCM) in low-voltage networks (e.g. data centers) that is not detected or is detected too late represents a significant safety risk:

  • Fault currents and insulation decay are caused by defective / bad components (e.g. switching power supplies, LEDs, server systems, PV, etc.)
  • In the data center should / must not be switched off in the event of a fault!
  • Overheated cable insulation causes a fire risk!
The solution

Detection of risky fault currents by means of permanent residual current measurement, thereby increasing the safe operation of electrical systems.

Figure 3: Residual current monitoring Source: Camille Bauer Metrawatt AG

Advantages
  • Time-consuming manual checks are no longer required (shutdown issue)
  • Continuous monitoring instead of status quo
  • Legal security with regard to the law, auditors (asset protection) and insurance companies
  • Permanent damage prevention to people and equipment

3. electrical data security through cyber security

Threat from cyber attacks

Figure 4: Threat of cyber attacks

The topic of cyber security is becoming increasingly important due to the constantly growing level of networking. Especially in the areas of critical infrastructure. Due to the threat situation, effective cyber security is essential there. Thus also very specific in data centers and considered under the topic of “electrical data security”.

You can find the complete blog post on cyber security here

Find complete solutions for your data center here

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Power quality issues emerge

Power quality issues challenge utilities as solar is added to the grid, survey finds

Power quality issues emerge in terms of voltage swags, swells, flickers, and harmonic distortions, among other things. Many utilities said they are not happy with their ability to gather useful data to address the problems.

Editor: David Wagman

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Fields of application of measuring instruments

In this article we will show you possible fields of application for measuring instruments. Certainly, this is only one option and not conclusive.

 

Fields of application of measuring instruments

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Ensuring grid quality on a small scale

Ensure power quality! These claims are becoming stronger and louder. This is confirmed by utilities, industrial companies, but also by many of the electrical specialists who are increasingly confronted with the topic on the part of their customers. The question often arises as to which measuring device should be used, with which expertise and with which budget.

Ensure the quality of the network for industrial needs. This is now offered by the LINAX PQ1000 series power analyzer according to IEC61000-4-30 class S. The measuring instrument is specially designed for the area of “Demand Side Power Quality” (DSPQ). There you will find the process for securing the power quality on the consumer side (according to the PoCC as per IEC TR 63191).

But why class S and not class A

Standards

Measuring instruments according to IEC 61000-4-30 Class A generally provide measured values that are comparable across measuring instruments and manufacturers. In case of legal cases, class A is mandatory and is particularly relevant for distribution system operators.

IEC 61000-4-30 class S power quality analysers are intended for basic / advanced power quality analysis and provide useful monitoring data. Instruments that meet Class S performance requirements are used for statistical power quality surveys and other applications and measurement services. There are no potential disputes there. Thus, comparable measurements are also not mandatory. The performance requirements for Class S are less stringent than for Class A. Among other things, this also results in a lower price. They are often used in industrial and supply engineering at the IPC(according to IEC [TR] 63191 this is the network distribution according to the Point of Common Coupling (PoCC)). Even in data centers, these are strongly recommended according to EN50600-2-2:2019-08 [Kapitel 6.2.3 Spannungsqualität] within the infrastructure.

Ensuring power quality with certification even for class S

A very important criterion for correct and repeatable measurement of power quality is compliance with standards for the measurement procedure. These are not to be confused with power quality compliance standards. For this reason, class S measuring devices should also be certified. With the LINAX PQ1000, this is ensured on the basis of the big brothers LINAX PQ3000 & PQ5000 by METAS, the Swiss Federal Institute of Metrology. Swiss precision.

Ensuring network quality with the highest standards of cyber security

Cyber Security

The topic of cyber security is also becoming more and more important due to the constantly growing networking. Especially in the areas of power distribution, whether in public or private networks. Due to the threat situation, effective cyber security is essential. To this end, the LINAX PQ1000offers many of the same effective protective features as its larger siblings. These include:

Designs of the LINAX PQ1000

LINAX PQ1000 all views

The PQI, according to Definition according to IEC 62586-1/2 for the analysis of power quality in power supply systems also called Power Quality Instrument (PQI), is available in various options. With the common 96x96mm form factor, the meter fits well anywhere. Whether for panel mounting with TFT display or for DIN rail mounting with or without TFT display. All variants are possible and offer high flexibility. Added to this is the simplest operation and communication via integrated web browser. Without additional software, operation, parameterization and monitoring are made child’s play.

More tutorials (e.g. on the topics UPS, PQ analysis, PQEasy reporting, data export, etc.) can be found here.

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Load Study with DranXperT

DranXperT Survey Study: officially published by Dranetz

Introduction on this load study

The National Fire Protection Association (NFPA) publishes NFPA 70, the National Electric Code (NEC). The NEC is the US reference for the safe installation of electrical systems. Although the NEC is not mandated by the US federal government, most states and/or municipalities in the US require compliance with NEC requirements.

NEC article 220 is for branch circuit, feeder, and service calculations and section 220.87 covers the requirements to determine existing loads. Compliance with NEC 220.87 is a requirement to determine available capacity when adding loads. For this purpose a load study with DranXperT was executed.

NEC 220.87 requirements

NEC 220.87 states that it is permissible to use the actual maximum demand when determining existing loads, but there are conditions.

The first condition is that the maximum demand data is available for 1 year. Practically speaking, unless the facility has existing branch circuit or other monitoring, 1 year of demand data may only be available at the utility service from utility billing.

There is an exception if maximum demand data is not available for 1 year – the calculated load can be measured at the feeder or service. Such a measurement requires a minimum 30-day load study by a power logger measuring the demand averaged over a 15-minute period. The load study must be taken while the space is occupied and include
measurements or calculations of the heating and cooling equipment (whichever is larger). Refer to NEC 220.87 for specific details.

Another condition is that 125% of the maximum demand plus the new load does not overload the circuit. The requirements for overload protection are covered elsewhere in the NEC.

Configuring the measurement device for the load study

For this study a DranXperT device has been used. Configuring DranXperT for a NEC 220.87 load survey is simple, and the settings are virtually identical to any other load study. It is important that you do the following to meet the requirements of NEC 220.87:

  • On the Survey Setup page set the Demand Interval to 15 minutes and the Journal Interval to 900 seconds (15 minutes). Doing so will program DranXperT to record the 15-minute average information required by NEC 220.87.
  • On the Instrument Setup page make sure that the Max DB File Seconds setting is set to the default of 31 days (or longer). This will meet the requirement of a minimum 30-day survey, and the data will recorded in one data file.

Determining the maximum demand

Determining the maximum demand or amperage is as simple as loading the data file into Dran-View XP (or Pro & Enterprise) and reading the maximum values for demand and amperage directly off the 30+ day trend plot.

 

In the right, the maximum demand and amperage occurred on June 7, 2021. The maximum demand was 260Kw and the maximum amperage was 891A on phase C. This is the information required to determine the available capacity for additional loads.

 

 

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Multifunctional system overview

Especially in the area of data monitoring you rightly demand a highly appealing HMI [Human Machine Interface]. Finally, a multifunctional system overview is to be generated from this. However, you should keep the growing complexity in mind. There is a danger of creating new data graveyards that previously cost money and produce no benefit. It certainly doesn’t help you to seemingly see more and more. And still you lose the overview due to an excess of information.

Multifunctional system overview? What can help you

We suggest the SmartCollect® SC² for this purpose. This is a scalable HMI/SCADA software. This conveniently visualizes your measurement data. Either for your electrical distribution as well as other physical quantities. But the software can also process physically independent information. Unlike the usual less visually appealing SCADA software systems, the SmartCollect® SC² is built on a new ultra-modern web-based platform. In the following you will learn more about the essential core modules.

Interactive single line diagram as multifunctional system overview

Interactive one-line diagram of the SmartCollect SC2

In principle, the structure of the software begins with this module. It continuously monitors all the data included in the
Infrastructure integrated circuits. In doing so, it offers you a compact overview. For the overview display as a single line diagram, you can effortlessly define your individual application design. Tailored to your needs.

Interactive 2D/3D views for your manager perspective

Interactive 2D/3D views of the SmartCollect SC2

Would you like to see energy infrastructure from a manager’s perspective? This is how you want it to be as a business manager or even as a manager with overall responsibility. In fact, this allows you to monitor specific individual performance indicators of a factory, a single plant, an entire complex, etc. Last but not least, to possibly benchmark with other comparable companies or locations.

Multifunctional system overview from the energy monitoring system [EMS]

Energy Monitoring System [EMS] of the SmartCollect SC2The high level of data collection gives you full transparency on energy data. For analytical purposes (e.g. reduction of CO2 emissions, increase of energy efficiency as well as for evaluation of savings potential, etc.) the EMS supports you. Various panel views within the EMS dashboard help you to do this. In addition, various reporting functions support you in your individual business analytics.

Multifunctional system overview with a sophisticated zoom function

Sophisticated zoom function of the SmartCollect SC2The zoom function allows you to perform detailed analysis directly on the dashboard. When zooming, all parameters in the overview are synchronized on the dashboard. Thus, you are able to put all related quantities in relation to each other.

Best in class WebGUI integration

Optimal WebGUI integration of the SmartCollect SC2The software supports your individual integration of device WebGUIs. This allows you to directly access various additional details of the measuring point, depending on the device function. You can also easily perform remote configuration. At Camille Bauer measuring devices, of course, exclusively with the very high cyber security standards according to ENEL GSTQ901.

Functional trend dashboard as multifunctional system overview

Functional trend dashboard of the SmartCollect SC2The state-of-the-art trend dashboard reliably shows you all relevant information. You have a permanent overview of all critical measured values. The data design is built to your individual needs. Again, the nifty zoom function helps you analyze. In addition, you define your individual time ranges that you want to overview as a trend.

Flexible data communication – a must

The software also offers you a wide variance of different data formats. This for your incoming, outgoing and protected data (e.g. Modbus TCP/IP, IEC61850, DNP3, IEC60870-5-104, UPC UA/DA, etc.). You can also export data in csv format by default. And this in actual raw format or also formatted for an MS Excel application. Other formats can be programmed and configured individually.

Learn more at SmartCollect® SC².

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