Improving power system stability

Brazil, Tucumã and Feijó

For Zopone Group, ANDRITZ is the first choice to supply three synchronous condensers for more grid stability in the Acre region of Brazil.

ANDRITZ Hydro Brazil recently received an order to provide three synchronous condenser systems, including electrical power systems, digital control, and protection system. The contractor and at the same time our customer is Transmissora Acre II, part of Zopone Group. They are undertaking the expansion projects of the transmission grid in the northern region in Brazil.

One of the expansion projects involves the installation of one +150/-90 MVAr synchronous condenser at the 230 kV Tucumã Substation near Rio Branco, the capital of Acre.

The other two synchronous condensers, +-45 MVAr each, will be installed at the 230 kV Feijó Substation, located about 360 km west of Rio Branco, halfway to the Brazilian border with Peru.

Two-element stator of a synchronous condenser preassembled at Weiz, Austria workshop for testing purposes

The substations, which will improve their technical capabilities to support the energy transition towards more renewable energy, are located in the state of Acre. The project supports expansion, enhancement, and increase of stability of the electric power transmission grid. The cities, villages, and farms within the region need very long transmission lines, which end up requiring more system inertia, more system strength, and better reactive power flow capabilities.

We are proud to have been awarded this contract, which presents logistical challenges but is also important in providing electricity to the local population. This order is an opportunity for ANDRITZ to further strengthen its market position in the synchronous condenser business in Brazil and South America.

Synchronous condensers

So far SVCs (static VAR compensation) and STATCOMs (static synchronous compensator) were the preferred options for power grid compensation solutions. System strength and system inertia were not in focus, as they were available in abundance due to the so far high share of synchronous generators connected to the grid. Due to the increasing share of wind and solar generation, battery energy storage systems and direct current network lines interconnected via inverters (IBRs, inverter-based resources) with transmission and subtransmission systems the situation changed significantly.

High penetration of IBRs results in lower stability of the electric power system, namely reduced frequency stability, reduced voltage stability, reduced rotor angle stability, reduced resonance stability and reduced converter driven stability. SVCs and STATCOMs support only regarding the voltage stability, and not regarding other stability issues. Therefore the long proven, robust and reliable solution of synchronous condenser systems undergo a renaissance after they basically disappeared from the market since the 1980s. One of the first installation for synchronous condensers dates back to 1911, even synchronous condensers became wider spread only starting in the 1950s. SynCons as those systems are also called in short are synchronous machines which’s shaft is not connected to any loads (like in case of a synchronous motor) or any driving force (like in case of synchronous generators). The shaft spins freely, acting like a shock absorber for the electric power system, in maintaining the system frequency and the voltage level.

Technical performance

Technical Details

Tucumã (230 kV substation)
Units:	1 × 165 MVA
Speed:	900 rpm (8-pole salient)
Short circuit contr.:	546 MVA
Inertia time const.:	2.4 s (natural)

Feijó (230 kV substation)
Units:	2 × 50.5 MVA
Speed:	1,800 rpm (4-pole)
Short circuit contr.:	195 MVA
Inertia time const.:	2.2 s (natural)