Power Quality Monitoring

gridvis-3The EN50160 standard describes the main features of power quality supplied by public low voltage and medium voltage distribution systems at the point of common coupling (PCC) under normal operating conditions.
Subject standard specifies the target limits and tolerances of different parameters of the delivered power quality. The standard does not touch typical situations or conditions of public distribution systems. The relevance of a reliable electrical power supply for the national economy and the increasing awareness of the clients for a high availability and a good power quality have been crucial for customer, to install a comprehensive power quality management system.
It was looked for an intelligent solution for the data collection and evaluation of measurement values of the power quality. With help of the evaluation software package DATARECON and a adequate number of power quality analysers of type JANITZA UMG 510 installed across the supply network at the critical supply points and finally networked and connected to a SCADA system with all data transferred to a central operation room it was possible to realize a totally integrated power quality management system.
The former analysis was done manually with a high time input. Contents of the analysis was for example the graphical evaluation and comparison of the sequences of the event recording , the data preparation for the Federal Network Agency for Electricity, comparison of the harmonic distortion factors and the load and utilisation of different parts of the integrated network. All these different actions are automatically executed with the help of a totally integrated power quality management system and are much more efficient.

Increased requirements for the power supply industry
gridvis-5Constantly increasing requirements for the power supply industry in view to the supply quality and supply security of the customers are unlike to the shareholders’ request for more efficiency and higher profit margins. On one hand the liberalization of the energy markets comes along with a harder competition which affects the safety margins and causes a reduction in infrastructure investments.
On the other hand more and more parts of the everyday life up to life-saving utilities are utmost depending on a reliable and safe power quality. Unfortunately this extreme circumstance was visible during recent years in worldwide power failures (black outs) in USA, Italy and Denmark and at the latest 2006 in Western Europe. Due to those facts it is necessary to strike a new path for a safe and reliable power quality supply. That means that simply monitoring of the electrical basic parameters like nominal voltage and current peaks is absolutely insufficient nowadays. The only solution of this complex of problems is a higher transparency of the power quality supply with a totally integrated power quality management system.

The importance of a reliable power supply.
gridvis-4The electrical current has different criteria which are responsible for the quality of the current. The both top criteria are availability and usability. The usability without any voltage interruption is described as voltage quality. The voltage quality becomes more important due to the use of increasing quantity of non-linear consumers who create system perturbations and have a high sensitivity e.g. IT devices at the same time. Electronic control equipments are sensitively responsive on voltage fluctuations even if the voltage fluctuation is just for a fraction of a second. But also the increased awareness of the energy consumers and the public utility plays an important role. The power quality is a complex topic and contains a lot of different parameters. This topic has an exceptional position especially in view of the continuous and direct interaction between generation and consumption. Other industrial products have clearly fixed product characteristics and, hence, a product quality process ensures that a product will be delivered with a clearly defined quality level. But the use of the electrical current, i.e. all connected loads, has a direct influence on the electrical current due to system perturbations, i.e. the power quality for the entire electricity system will be influenced by each individual connected and operated load. And all adjacent customers are affected by these perturbations.

Control room
The entire information of the power quality management system is accumulated in the control room. The essential measurement data are easily accessible in a SQL database format. Switching operations are done to protect the transformer stations or distribution network and equipment. In the majority of cases the damage is kept in reasonable limits if the operator receives the right information on time and is able to do a fact based decisionand take care for adequate counter measures right in time.

Transparency for the power supply network
The first step on the way to a totally integrated power quality system and energy management system is creating transparency in the power network. This is the base for wide-area decisions, e.g. to avoid costly new investments into an additional power sub station.Further the data can be used for power quality measures, e.g. active harmonic filters. Time-consuming investigations to identify root causes for perturbation of the power network become unnecessary.

The obligation to evidence the power supply reliability and power quality according to EN 50160 standard was the original motivation factor for any power utilities in the past. Now the advantages of a totally integrated power quality management system, providing a high level of transparency, become more and more important and visible:

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