Electrification Israel Railroads: Network Frequency Instability and Challenges of Distribution Voltage Control

Abstract

Electrification of Israel railroads is a successful project being realized during present time. Among the well-known advantages of electric train exploitation are high energetic efficiency, regenerative breaking, diminished pollution, flexibility of traffic control and improved transportation dynamics. However, the use of electric train is accompanied with some specific hurdles caused by significantly stochastic power flows. While in transit between stations an electric train has different phases of movement, during some consuming energy, but from time to time throughout braking processes they become generators transmitting energy back into the electric grid. This circumstance may produce voltage instability in distribution lines, which should be kept inside permissible limits to allow normal operation of electric equipment. Tap-changers on distribution transformers considered for a voltage regulation have sluggish response of ~7-8 sec. Therefore, fast changes of power stream can cause significant voltage deviations. If the voltage overcome explicit allowable level a trigger of a protection system is engendered disconnecting vehicles from a grid. The last causes extremely dangerous detriments and should be maximally prevented.Rapid and considerable changes in train power consumption, in addition may cause network frequency instability which in turn can violate electricity supply.Present article provides an original examination of the future stability of network frequency and distribution voltage which may be assumed when 420 km of Israel railroads will be electrified in the following 5–10 years. For such study special algorithm based on simulation approach was developed and applied. Predicting scenarios for frequency and distribution lines voltage control are represented below in the following text.