The fourth and last of the PSTs (Phase Shifting Transformers – transformers with phase angle regulation) has arrived in the Hradec u Kadaně substation. The Czech transmission system operator is expecting all of the machines to be put in operation by the end of June. This will make possible the regulation of energy flows also on the second interconnector with the eastern part of Germany.
The device consists of two parts – a series unit and a shunt unit –, which will be now put together. Afterwards, the device will be connected to the substation equipment, tested and put into test operation. Only after that the operation of the transformer will be included in the energy management system.
“The PSTs will allow to maintain electricity flows within safe limits. Setting up the regulatory parameters will be coordinated with foreign partners with the primary objective of ensuring
the reliability of the operation of electricity networks throughout the region of Central Europe,” says Jan Kalina, Chairman of the ČEPS, a.s. Board of Directors.
On one of the two interconnectors with the eastern part of Germany, dispatchers started regulating electricity flows on January 13. The ČEPS Company took a decision to launch two of the four machines due to the delayed delivery of the last, fourth transformer. The Czech and German substations are connected by two 400 kV power lines. Two PSTs will be connected
in parallel on each of the lines.
“The partial commissioning helped minimize the use of expensive emergency corrective measures. Even until all the PSTs are launched, that is during the first six months of this year, we can save tens of millions of crowns,” adds Kalina.
Phase-shifting transformers are machines that are used to control the power flow of real power through manipulation of the phase angle of the voltage between the transmitting end and
the receiving end of the line. Put simply, if we imagine the transmission system as a reservoir with many tributaries and distributaries, the PST works as a valve, which reduces, or increases the flow in the given distributary. Reducing the flow on one power line results in redistribution of flows in the entire interconnected system. Since electricity takes the path of least resistance, part of the flows will move to other power lines with more available capacity, thus eliminating possible overloads in the transmission network.
The operation of our PST transformers together with similar devices operating at the Germany-Poland border will help stabilize the transit flows. The goal of PST transformers is not to prevent electricity flowing through our transmission system. ČEPS aims to transfer the maximum amount of electricity, but safely, without compromising the reliability of the power supply in the Czech Republic. And this is what this special type of transformer has to offer. The role of the PST will be to ensure the safe operation of the transformers in our transmission system, not only in times of extreme transit flows, but also during long-term limitation of transmission capacity due to extensive reconstructions of power lines.
The total investment costs for the construction (project preparation, expansion of the substation, the devices) shall not exceed CZK 2 billion.
“This is a unique piece of equipment with an estimated lifespan of more than 40 years. The cost for the construction of these transformers are high, but a possible widespread power failure
in the transmission system would cause far greater damage,” says Kalina.
High unscheduled flows between northern Germany and its neighboring countries – Czech Republic and Poland – are a threat to the safe operation of transmission systems. Corrective measures for maintaining reliability that the individual grid operators must take are often very expensive. In addition, the overflows also affect the international electricity trade. From
a security standpoint, it is necessary to allocate part of the cross-border transmission capacities specifically for the unscheduled flows. After putting all four PSTs into operation, the released capacities may be utilized for the realization of electricity trades.