For seamless integration of offshore renewable generation with onshore grid using LF-HVac network it is essential to develop a robust protection system. Under low frequency transmission, the transmission line impedance is reduced that helps to increase the power transfer capability of the system. Power transfer capabilities are almost comparable to HVdc systems under very low frequencies. The key difference between developing a protection scheme for LF-HVac compared to a HVdc system is the essential zero-crossing of the ac current/voltage. Some literature's have proposed the use of conventional ac breakers to interrupt faults on the LF-HVac transmission side. Reduction of system impedance on the low-frequency ac side results in higher fault current. In our study we have worked on and improved a previously proposed low-frequency circuit breaker (US 9,263,880 B2). Our design and operation shows a faster interruption of the fault current. Along with that we proposed a new hybrid circuit breaker design that has a serial operating structure contrary to the parallel operating one as was previously proposed. We have extensively tested the operational characteristics of the modified design and the newly proposed serial circuit breaker design.