Consider a system of three charges $\frac{q}{3},\frac{q}{3}$ and $-\frac{2q}{3}$ placed at points $A,B$ and $C$ respectively, as shown in the figure below. Take $O$ to be the centre of the circle of radius R and angle $CAB=60°$

The electric field at point $O$ is $\frac{q}{8\pi {\epsilon }_0{R}^2}$ directed along the negative $X$-axis

The potential at point $O$ is $\frac{q}{12\pi {\epsilon }_{0}R}$

The magnitude of the force between the charges at points $C$ and $B$ is $\frac{q^2}{54\pi {\epsilon }_0{R}^2}$

The potential energy of the system is zero