Investigation on Zero-miss Phenomenon in Shunt Reactor Compensated Long HVAC Cable for Offshore Wind Farm

Recent offshore wind farms are increasingly located between tens and hundreds of kilometers from the coastline. An important characteristic of long-distance submarine cables is their high inherent capacitance, which is typically compensated by shunt reactors. In some projects, shunt reactor installation is limited to one cable end due to responsibility boundaries between the grid operator and the wind farm owner. Owing to space constraints on offshore platforms, the offshore shunt reactor and submarine cable are often connected within the same bay and switched simultaneously using a single circuit breaker. Under such conditions, particularly when the shunt reactor compensation degree exceeds 50%, combined energization may lead to a zero-miss phenomenon, characterized by the absence of current zero crossings for a prolonged period of time. This condition becomes hazardous if there is a fault in cable during energization, as the circuit breaker may be unable to interrupt the current in extended duration due to the absence of current zero. The zero-miss phenomenon adversely affects the correct operation of protection systems and may damage circuit breakers and associated equipment. Therefore, understanding the mechanisms leading to zero-miss in circuit breakers is essential to ensure reliable design and safe operation of offshore wind farms. This paper investigates the mechanisms responsible for the zero-miss phenomenon using electromagnetic transient simulations. The main system components, including submarine cables and shunt reactors, are modelled in detail. Different shunt reactor compensation schemes are analyzed to demonstrate the occurrence of the zero-miss phenomenon. Mitigation measures based on controlled switching devices are proposed to optimize the switching instant with respect to the system voltage, thereby eliminating or significantly reducing the zero-miss effect.