Ratel is indeed using d3js.org for graph rendering.
It’s most likely a slightly outdated overkill for your use case, but Ratel has long list of requirements.
Previously we used vis.js but that library is no longer maintained.
Sadly there aren’t many graph visualization libraries, or at least not as many options as for bar or line charts.
I’d look into http://js.cytoscape.org/ or
paperjs if I were starting a visualization project from scratch.
If you share specifics of the data you need to display I can try to think of a better alternative.
Is it simply nodes and edges? Are there any regularities you need shown, what interactions do your users need? (selecting, dragging, adding/removing pieces). Do you know where your nodes must be placed on the page or would library need to decide that?