Transmission losses spatial analysis of the supply system of electrified urban transport network
1) The purpose of the research.
The issue of electric energy saving in public transport is currently becoming a key area of interest, a fact connected both with an increase in society’s environmental awareness and a rise in the prices of fuel and electricity. Electricity can be saved by reducing transmission losses in the supply system. The article presents a method of measurement and analysis of transmission losses in the supply system of electrified public transport on the example of trolleybus transport in Gdynia.
The problem of transmission losses in catenary power supply systems of public transport has been marginalised for many years. Most scientific works publish the values of transmission losses based only on theoretical simulations. The author of the present paper propose the method based on measuring of the voltage and current of the vehicles, which does not require the knowledge of the supply system resistance. Additionally, there is no need to carry out measurements in every vehicle.
2) The principal results and accomplishments and their significance.
The measurements were conducted on traction substations and in trolleybuses. To that effect, an on-board system of registration of the consumed energy was used along with the record GPS position over time, provided in units operating in Gdynia. This allows the determination of precise energy consumption in each supply section. During the measurements in vehicles, the values of the supply voltage and current taken from the supply system were measured. The average transmission losses are on the level 8%, but in case of some sections they reach the value of 15%.
3) The major conclusions.
The method presented allows measurement of transmission losses in traction supply system, which requires the registration of the vehicle current, vehicle supply voltage, substation voltage and the GPS localisation of the vehicle. These values can be easily measured. The efficient energy in a particular place of the supply system can be set. The method can be used for diagnostic purposes of supply systems and energy efficiency assessment as part of the energetic audit of the public transport system. The conducted measurements and simulations indicate a strong relationship between the traffic conditions, spatial structure of the supply system and the transmission losses.
Generally, transmission losses in the supply system are less than 10%, but it should be underlined that in unfavourable situations they can reach high values, even greater than 15%. This has a significant impact on the total energy consumption. It confirms the desirability of performing detailed measurements of transmission losses, which can help in finding the weak points in the supply system.