Why does srandom(time(NULL)) behave differently within main() function and that of a user defined function?

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void sep_gen(void);

int main()
{
srandom((unsigned)time(NULL));
printf("Random Numbers\n");

sep_gen();
sep_gen();
sep_gen();

return(0);
}

void sep_gen(void)
{
long int r;
int i;

for (i=0;i<10;i++)
    putchar('-');
putchar('\n');

r=random();
printf("%ld\n",r);
}

The above code generates three different integers as intended. However, when the srandom((unsigned)time(NULL)) is used sep_gen() function, the integers generated are the same all the three times. (Code below)

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void sep_gen(void);

int main()
{
printf("Random Numbers\n");

sep_gen();
sep_gen();
sep_gen();

return(0);
}

void sep_gen(void)
{

srandom((unsigned)time(NULL));
long int r;
int i;

for (i=0;i<10;i++)
    putchar('-');
putchar('\n');

r=random();
printf("%ld\n",r);
}

My question why is that random() function generates different numbers when the srandom() functioned is placed in the main function, but doesn't do so when in sep_gen() function?