Electron paramagnetic resonance (EPR) was used to study the T-V2a center in 4H-SiC, which was previously attributed to the isolated Si vacancy but with different charge states: neutral, single negative, and triple negative, corresponding to different spin states S=1, S=3/2, and S=1/2, respectively. The T-V2a EPR spectra observed in dark and under light illumination in as-grown high-purity semi-insulating 4H-SiC in the absence of the negatively charged Si vacancy (V-Si(-)) provide direct evidence confirming the spin triplet (S=1) ground state of the center. A model with a triplet ground state and a singlet excited state is proposed to explain previously obtained results. The T-V2a center can be detected in as-grown material annealed at 1600degreesC.