General diagram

The energy that is consumed in a cement mill represents always an important part of the total production costs and the monthly invoice is, in general, quite high.

By other side, the problems related to power quality are very relevant, considering that the equipment existing in the mill is more and more sensitive as well considering the power that is involved (large variable speed drives are quite common in this industry) and also considering the contractual conditions with the energy provider.

The cost resulting from a sudden shutdown due to power quality problems or referring to a non-compliance event of contractual terms with the energy provider may be very high.

For these reasons, a Power Quality Monitoring and Energy Management System is a fundamental tool for this industry, as it will allow:

• Cost reduction.
• Convenient allocation of costs by the different departments / products.
• Clearly show how much, where, how, in what conditions the energy is consumed.
• Identification of possibilities for improving energy efficiency.
• Identification of power quality problems in the connection point with public grid as well related with internal equipment.
• Collection of important data for planning the maintenance interventions as well for new investments.

Main features of the system

Monitoring at the connection with public grid (60 kV)

• Monitor the contractual compliance.
• Disturbance logging.
• Identify the direction of the disturbance.
• Standards compliance - EN50160; IEC 61000-4-30.
• Peak demand control.

Monitoring at the MV level (6 kV)

• Disturbance detection and recording on the 6kV switchgears, transformers, MV motors.
• Interconnection with protection devices.
• Status from different points recorded simultaneously, through digital inputs.
• The analysis of status inputs allows seeing the sequence of occurrences in the time.
• Waveform recording can be triggered by a change in a digital input.
• The analysis of collected data may give important information for understanding the root causes of the occurred disturbances / faults
• Based on this data, maintenance interventions can be planned before occurring catastrophic failures on equipment.
• The consequences of an unscheduled shutdown are in general worse by comparison with a planned intervention.

Monitoring at the BT level BT (400V)

• There is low voltage equipment that, by the importance that has for the production process or by the consequences of an unscheduled shutdown, totally justifies monitoring.

Integration with other systems / equipment

• In a mill is quite common to find other devices, already installed, that can provide data that can be integrated within the energy monitoring system (EMS) (protections, dispersed meters ...); this data can be collected by the EMS and integrated with the data from the EMS itself.
• In similar way, devices that are specifically installed in the scope of the EMS can provide important data for other systems (SCADA).
• The communication can be directly at the device level (Modbus), OPC connection between servers or connection between databases.
• Besides the data referring to electrical energy, there is also data referring to the production process that is important to integrate into de EMS.
• Calculation of energy indicators, specific consumption, equipment usage rate etc.
• The EMS can be connected to the existing SCADA both for data exchange and also for executing commands.
• Selective load shedding for peak demand control, reactive energy compensation.

Monthly report – Global energy consumption by day, with allocation by sectors

Specific consumption by day and by sector

Energy metering at each sector of the mil / Load forecast

• The comparison in real time of effective energy consumption with the forecasted, allows you to identify deviations or eventual anomalies if any.
• Based on the production plan, the EMS can forecast the electrical energy load diagram.
• The simulation of different usage profiles of the equipment/facilities, together with the tariff system, may become an important tool for defining the production plan that minimizes de total energy cost.
• Combining the data referring to consumed energy with the one referring to production, you can calculate and monitor important indicators (KPI’s) for production management (kWh / produced tones / type of product).

Monthly invoice – graphical presentation

Monthly invoice

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