Principles of Frequency Regulation in Pumping Units
For a deeper understanding of the principle of frequency regulation of engine operating modes, let’s consider one of the most common cases of using this method – managing the operation of pumping units in water supply systems.
The importance of this issue can be assessed by analyzing the statistics of electricity consumption in Ukraine: about 50% of all electricity is consumed annually to power the drives of pumping and other pumping units.
Pressure in the Water Supply System
In order to ensure water supply to end consumers, it is necessary to maintain a certain level of pressure in the pipelines at the outlet of the pumping stations. The pressure level consists of two main components:
- Static component: the difference in absolute height levels of the consumer and the pumping station plus the necessary pressure at the consumption point;
- Dynamic component: the pressure required to overcome the hydraulic resistance that occurs during the passage of fluid through the pipeline network.
This dependency defines the operation of the entire water supply system, indicating the pressure head that needs to be ensured at the outlet of the pumping station so that the most remote consumer has adequate water pressure.
Mechanism of Pumping Unit Operation
The performance of a pumping unit is calculated as the product of the pressure supplied at the outlet and the amount of water passing through the pipes per unit of time. In fact, this parameter is proportional to the rotational speed of the pump shaft.
Until recently, one pump with the required power and output was used to maintain the necessary pressure. This increases the likelihood of accidents since the more a section of pipe is throttled by a valve, the lower the pressure in the main line. Depending on the level of automation, this method allows for controlling the pressure in the pipeline.
Innovative Approach: Frequency Regulation
The method of frequency regulation of the performance of pumping units, which has only been widely applied in recent years, radically changes the principle of pressure control in the network. It is not the parameters of the pipeline that are regulated, but the performance of the pumping station, which depends on the rotational speed of the engine shaft. This speed, in turn, is determined by the characteristics of the voltage supplied to the engine. Frequency converters are used for this.
Modern frequency converters not only automatically regulate the necessary level of pressure at the outlet of the pumping station based on sensor readings but also provide:
- reliable protection of the system from emergency situations;
- protection of the engine from voltage spikes in the electrical network;
- automation of the process of managing the operational modes of the pumping station;
- significant savings in electrical energy;
- reduction of water consumption in water intake and water supply systems.