Summon a PrimedTnt with a very long fuse

I would like to create a PrimedTnt with a fuse longer than the maximum (max fuse = 127 ticks). The fuse must be about 10 seconds. Thanks for your help.

I have tried putting 2 command blocks on a 20hZ clock, that summons a PrimedTnt at the old one and then kills the old PrimedTnt. It happens a few times, but then it stops automatically.

The commands is:

To summon a PrimedTnt at the old one:

/execute @e[type=PrimedTnt] ~ ~ ~ /summon PrimedTnt ~ ~ ~

And then to kill the old PrimedTnt:

/kill @e[type=PrimedTnt]