Switching surge & power quality measurement for railways

Power Quality (PQ) is an issue that is becoming increasingly important to electricity consumers at all levels of usage. In railway systems, the electrical locomotives are considered big single-phase loads for the traction supply system. As the speed and mechanical conditions of the train change frequently, they exert non-linear and time-varying loads, thereby injecting a certain number of conducted electrical disturbances that propagate on the supply line, even reaching other trains or even the power substation. On the other hand, the electrical substations absorb energy from the high-voltage AC grid to feed the locomotives at a lower voltage level. Obviously, many of the Power Quality (PQ) problems in the high-voltage AC network are transferred to the rail traction supply system.

Also, AC electric rolling stock, AC-DC electric locomotives, EMUs, and MEMUs are fitted with single-phase bridge-connected silicon rectifiers with smoothening reactors for feeding the DC traction motors. These rectifiers also introduce harmonic currents into the 25 kV power supply. In recent years, high-speed railways have become a prevalent transportation system due to their excellent advantages in safety, environmental friendliness, comfort, and timeliness. It is of utmost importance to conduct the assessment of power quality parameters to foster the efficiency of the whole railway system by “awarding” the good PQ delivered and absorbed.

Harmonics: current and voltage distortions; frequency: under and over frequencies; current and voltage unbalance; power factor and rapid voltage changes; transients, voltage dips, and short-term overvoltages; sags and swells; and voltage interruptions are all critical power quality parameters to assess.

1.0 Significant test facilities are available at ERDA for Power Quality Measurement
ERDA has a test facility for power quality measurement for single-phase and three-phase systems, including RMS voltage, RMS current, active power, reactive power, apparent power, power factor, voltage THD, current THD, and individual harmonics in both voltage and current up to 50th order, current and voltage unbalance, sags, swells, etc. with four numbers of power analysers compliant with IEC 61000-4-30, Class A. Based on guidelines given in IEEE 519:2014, ERDA undertakes the measurement of power quality parameters at the point of common coupling (PCC) and at harmonic generating loads for metros.

 

2.0 Major evaluation facilities are available at ERDA for Switching Surge Measurement at the site.
ERDA is equipped with a Capacitive Voltage Divider having the capacity of measuring switching voltages up to 270 kV peak and high voltage probes with a capacity of up to 14 kVrms. We also have a high bandwidth oscilloscope of 500 MHz.