Power quality management in supermarkets

PQM in Supermarkets

Project description supermarkt

The problem

Despite very similar buildings and consumer structures, the consumption and loads in supermarket stores can be very different. The reason for this can be the various manufacturers of deep freezers, lighting and ventilation systems which often have very different levels of energy efficiency but it can also be due to the various sites with different weather conditions (snow, hours of sunlight etc), the number of customers each day or the environmental awareness of the employees.

Furthermore, non-linear consumers frequently lead to serious problems with regard to power quality. Therefore, it makes sense to measure consumption levels and loads together with the general power data in the stores, collect the data and benchmark the stores with each other.

The task

A supermarket chain wanted to measure the loads, consumption data and power quality in the main feeders and several outputs in the respective stores and then collect the data in one main PC. With the help of concrete measurement data, stores with high consumption levels were intended to be identified in order to find reasons for the particularly high consumption and peak loads.

The supermarket chain then wanted to reduce peak loads using peak demand management and monitor the power quality in the individual outputs with regard to harmonics, as produced by deep freezers for example. In addition, the consumption of gas and water was also to be measured and the data was to be provided to the facility management. The communication media was an ISDN connection.

The solution

Stores:

A UMG 507E was deployed in the main feeder which enabled direct access through an ISDN router. On one hand, the device monitors power quality in the complete network and on the other hand, allows peak demand management for six sheddable loads using the Emax function. The unit can be extended by up to 32 Emax channels using an external WAGO module. Additional superfluous consumptions can be avoided using a time switch program e.g. automatic switch-off for lighting when the store closes.

 

Voltage breaks and other events can be sent by e-mail with a document attachment upon request. The sub measurements are connected to the UMG 507E using an RS485 which also functions as a gateway. Data from four outputs (freezers, ventilation, lighting and compressors) are collected using four UMG 96S´s with the clock and memory. The consumption of gas and water is measured using pulse meters and the pulse is passed on to the integral ProData®.

Headquarters:

The data is compiled on a main data server. The measurement value memory in the instruments is conveniently read-out using the PSW professional analysis software in the individual stores. Due to the number of stores, the instruments are only read once per month. The measurement data can easily be processed for the required time period comparison in MS Excel sheets. These are integrated using MS Excel macros which read the data produced by PSW professional into the database.

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