I also want to to the same something like this:
@NLconstraint(cgecam, eq[it in IT] , pm[it] == pwm[it]er(1 + tm[it]) if pwm[it]>=0.0 )
in otherwords I create a contraint only if pwm[it] is greater than zero. In GAMS it works well with $ operator. For Julia/Jump I have failed to do this.