What is a measurement concept?
The measurement concept is the foundation of effective operational energy management. With the help of the measurement concept, you can obtain a structured and comprehensive picture of the structure of the energy infrastructure in the company by breaking down the existing measurement points. It includes both the metadata of the measuring points, such as the designation, and the assigned physical measurement by a measuring device. The creation of a measurement concept often begins with an inventory of the existing infrastructure. However, it is also used to plan new measuring points and to design the measuring technology required for them.
Why do I need a measurement concept?
Energy management is becoming increasingly important in companies in all sectors due to legal requirements and internal cost pressure. A holistic measurement concept serves to fulfill legal requirements and regulations within the scope of certifications and audits. But also the use of funding opportunities, such as BAFA funding, set requirements for industrial companies on the topic of energy management and in particular also on the development of a measurement concept.
In addition, there are further regulations and verification requirements, for example, if you have your own generation facilities and would like to profit from possible benefits in this respect. In addition, the measurement concept includes an inventory of the current situation. Furthermore, it serves the structured planning of the extension of the measurement system. With the help of the measurement concept, it is possible to map the topology, i.e. the relationships between the various measurement points in your plant, in addition to a pure listing of plants and other logical measurement points. As a result, the energy distribution of different media such as electricity or gas in your plant can be displayed, e.g. in the form of the well-known Sankey diagram. The measurement concept is also an elementary part of an energy monitoring and management software, which makes it possible to identify and then realize optimization potentials in your company through the transparency created.
What should be considered when creating a measurement concept?
When creating a holistic measurement concept, the necessity of a measurement that conforms to calibration law must also be considered. This means that the measurement technology used for these measuring points must meet the requirements of a measurement that conforms to calibration law.
The creation of a measurement concept usually comprises three major steps, which in turn consist of subtasks. In order to arrive at the target image of a holistic measurement concept, we have to enter the existing measurement points and plan further ones. In addition, we have to design and procure the appropriate measurement technology for those measurement points where measurement is envisaged. And of course, this measurement technology also needs to be installed and configured.
Where do I start measuring?
Unnecessary or wrong meters can quickly increase the cost of the energy management system by 5,000€ or more for no reason. Therefore, we recommend starting the measurement at the transfer meter and the main distributions. Only after a first data-based analysis should the system be extended to specific plants.
Three meter levels: Transfer meter, main distribution and subdistribution
The electrotechnical topology is the same in almost every industrial plant: The energy is supplied by the power grid at the transfer point and recorded there by the transfer meter. This meter is the energy-relevant meter for billing. Industrial companies receive the 15-minute load curve from their supplier as basic information. In fact, there are considerably more parameters in the meter and fundamental errors can already be detected with regard to load peaks, standby consumption, voltage fluctuations or power asymmetries. We recommend starting with such an analysis in order to decide whether there is any savings potential at all.
Often the transfer meter is the only meter on the 20kV level and therefore necessary for the determination of transformer or distribution losses. From the point of view of the energy industry, "submetering" begins after the transfer meter.
Directly behind the transfer meter is the 20kV distribution with the transformers. The transformers feed the busbars of the low-voltage main distribution boards (NSHVT). It is at this point on the "transformer underside" that some type of metering is usually located.
Depending on the year of manufacture and equipment, you can find power quality meters, multifunction meters or analog current and voltage meters at the bottom of the transformer. In most companies, we recommend normal universal measuring devices. These have the best price-performance ratio and can be read out, for example, via Modbus TCP with very high data quality with any evaluation software. High-quality power quality meters should be used if power quality disturbances occur frequently (e.g. screen flickering, UPS).
In older installations you can usually find the four analog indicators. One is for the voltages and the other three for the phase currents. Although the devices cannot be read out, they reduce the work for the electrician considerably: both the current transformers and the voltage tap can simply be reconnected to a modern universal measuring device (caution when converting: current transformers should always be short-circuited). The holes in the control cabinet door can also still be used, as the installation dimensions are identical. The new universal measuring device replaces all four displays. The three holes in the control cabinet door that become free create space for additional submeters.
The low-voltage main distribution boards have the task of distributing the current coming from the transformer via the busbar. In this respect, the main distribution boards are usually ideally suited for measuring devices: the cables are easily accessible. In addition, there is no need for cabling for communication lines, as several meters can be installed in one place. This is a major advantage over metering in the subdistribution board or directly at the plant.
The costs of the measuring system can be optimized if not all plants are equipped with measuring devices at once. The best result is achieved when proceeding step by step along the energy distribution. First, only the transfer meter is recorded in order to determine from the load curve whether energy management is worthwhile at all. Then, the transformer underside is connected to the system at the feed-in of the low-voltage main distribution board.
1. meter selection: Universal meters have the best price-performance ratio. A variant with Modbus TCP should be used. These are compatible with all evaluation systems. Manufacturer-specific protocols or pulses should always be avoided!
2. meter location: The low-voltage main distribution boards are the ideal location for meters. Here, multiple meters can be placed at the incoming and outgoing feeders, thereby reducing wiring requirements for the communication lines. Only if the individual plant cannot be tapped at the low-voltage main distribution board, a meter installation at the plant makes sense.
The decisive factor for the extension of the data acquisition is always the unmeasured remainder. If this can be fully explained both in the Sankey diagram and in the time course of the stacked chart, no further meter is necessary. If it is not clear which plant is responsible for the consumption characteristic, further meters should be installed.
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