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CASE STUDY 2 - RTRPC Reduce Turkish State Railways Electricity Costs

The Turkish State Railways (TCDD) controls approximately 11,000 km of railways all around the country over two continents. The electricity is supplied through single phase 154 kV. Substations are used to reduce the voltage to 25 kV using two 7.5 MVA transformers (Figure 1). When a train reaches the substation network, the load is rapidly increased and goes back to nearly zero when the train leaves this network segment. The changes are of Mega watts in tenth of a second.

Figure 1 : General Diagram
Note: Real Time Reactive Power Compensation System(RTRPC)

The main objectives of the Turkish State Railways were:

Capacity : to allow more trains on the same railway segment simultaneously.
Stability : rapid load changes create voltage fluctuations.
Power Factor penalties: strict penalties regulations include both leading and lagging limits.
Infrastructure : reducing the costs of electricity generation and transportation.

Turkish State Railways installed 25 single phase RTRPC systems, with nominal size ranging from 1250 kVAr to 2750 kVAr each (Figure 2). The systems had nominal voltage of 500V or 690V (line-to-ground), and were connected to the 25kV network using step-up transformer. Parallel inductor is permanently connected to compensate the capacity of the long lines, while there is no load.

CASE STUDY

Figure 2 : RTRPC at TCDD

The RTRPC achieves full network compensation within maximum one network cycle. This results in unity power factor, improved power quality and energy savings. Therefore TCDD is able to use smaller transformer for the same load or increase the load on same substation (allowing more trains in the segment), together with enhanced network reliability.

RTRPC Reduce Turkish State Railways Electricity Costs

Figure 3 shows the RTRPC system performance, taken using PowerIQ, which allows remote control and operation of the systems. When the RTRPC was switched into Automatic mode the total network current was reduced from approx. 7000A to 3000A (more than 50%). The project included two stages, and only after the successful installation and operation of the first 6 systems (along the Istanbul to Ankara railway), TCDD continued to the next stage with additional 19 systems along 4 countrywide lines.

Figure 3 : Figure 3: Idealtepe Station With and Without RTRPC

Major Benefits:

Increasing Network Capacity
Enhancing Network Stability
Preventing Power Factor Penalties
Reducing Infrastructure Costs

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