Shunt Reactor Switching in Brazilian Grid: A Critical Analysis of Circuit-Breaker Standard Requirements and the Actual Stresses in the Network

In the Brazilian transmission system (U ≥ 230 kV), which comprises approximately 180,000 km of transmission lines, nearly 1,100 shunt reactor banks are currently in operation, of which about 530 are switchable. This widespread deployment highlights the need for careful assessment of shunt reactor circuit-breaker requirements during the planning and specification stages.

This paper analyses the transient recovery voltage (TRV) imposed on circuit-breakers during switching operations of shunt reactors with solid grounding, as well as reactors grounded through a neutral reactor. The influence of reactor current magnitude on the TRV peak is discussed, emphasizing the importance of type testing circuit-breakers with test currents equal to or lower than the reactor rated current.

The standardized framework established by IEC 62271-110 [1] and IEC/TR 62271-306 [2] is revisited and critically assessed with respect to its applicability to practical field conditions. The paper argues for a revision of the minimum test current requirements specified in IEC 62271110, aiming at a better representation of real operating conditions, particularly for circuitbreakers rated at 245 kV and below. Furthermore, it is shown that the switching of shunt reactors—especially those grounded through neutral reactors—may impose more severe dielectric stress on circuit-breakers than currently assumed by IEC test procedures.

Without adequate consideration during specification and verification, such switching duties may pose significant operational risks, including the possibility of catastrophic equipment failure. The paper highlights critical aspects of shunt reactor circuit-breaker application and provides technical guidance for the specification and operation of this class of equipment.