Three points charges are placed at the comers of an equilateral triangle of side L as shown in the figure.  

 

 

 

 

The system can be considered as two dipoles placed like as shown in figure  

$p_{\text{net }}=\sqrt{p^2+p^2+2p^2\cos 60}$ where $p=q\times L$ $Therefore p_{net}=\sqrt{3}qL$

 Potential at centroid = $\frac{kq}{r}+\frac{kq}{r}+\frac{k(-2q)}{r}=0 where r =\frac{L}{\sqrt{3}}$ 

Electric field at the centroid = 2$\left(\frac{kq}{r^2}\right)\cos {30}^0-\frac{k\left(2q\right)}{r^2}\not\equiv 0$