  We are carrying out the GPPS survey by using the FAST, the most sensitive
systematic pulsar survey in the Galactic plane. In addition to about 500
pulsars already discovered through normal periodical search, we report here the
discovery of 76 new transient radio sources with sporadic strong pulses,
detected by using the newly developed module for a sensitive single pulse
search. Their small DM values suggest that they all are the Galactic RRATs.
More radio pulses have been detected from 26 transient radio sources but no
periods can be found due to a limited small number of pulses from all FAST
observations. The following-up observations show that 16 transient sources are
newly identified as being the prototypes of RRATs with a period already
determined from more detected sporadic pulses, 10 sources are extremely nulling
pulsars, and 24 sources are weak pulsars with sparse strong pulses. On the
other hand, 48 previously known RRATs have been detected by the FAST. Except
for 1 RRAT with four pulses detected in a session of five minute observation
and 4 RRATs with only one pulse detected in a session, sensitive FAST
observations reveal that 43 RRATs are just generally weak pulsars with sporadic
strong pulses or simply very nulling pulsars, so that the previously known
RRATs always have an extreme emission state together with a normal hardly
detectable weak emission state. This is echoed by the two normal pulsars
J1938+2213 and J1946+1449 with occasional brightening pulses. Though strong
pulses of RRATs are very outstanding in the energy distribution, their
polarization angle variations follow the polarization angle curve of the
averaged normal pulse profile, suggesting that the predominant sparse pulses of
RRATs are emitted in the same region with the same geometry as normal weak
pulsars.
