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MV


Breaker 35 KV Vacuum Breaker. This compact unit pro- tects the substation’s output side. It’s basically a brass box on four legs with six insulators on top for in-and-out of three phases.


base. The insulators are mount- ed on angles to get the maximum separation to prevent arc-over. I first attempted to machine the housing out of a single piece of aluminum, but this didn’t work. I went about machining sepa- rate pieces for the breaker hous- ing. It’s all assembled on a cen- ter mandrel, which is a piece of 3/32-inch brass rod. One chal- lenge that stands out was mill- ing the canted seats to mount the insulator bases on the breaker end. Another challenge was cre- ating the all-brass base. I wanted to limit the use of styrene to only the add-on details. Soldering the base was harder than I expected, and in retrospect, I would have designed it differently. The pro- totype has an assembly of angle brackets that tie the housings to the base. I tried to replicate this in 1:48, and it created many sol- der joints in close proximity to one another, resulting in lots of re-soldering after pieces kept falling off.


After installing the insula- tor bases on each breaker unit, the breaker housings had to be glued to the base with the outer units splayed out at 30 degrees. I couldn’t solder this since it was aluminum to brass, so J-B Weld epoxy provided the grip. Once all


the breakers were in place and cured, several more things had to be added: six observation win- dows that enable personnel to see the position of the breaker and disconnect mechanism; the control cabinet; the insulator stacks; and control wiring. Sim- ulated cables are 32 AWG black iron wire. To get the observa- tion windows to conform to the breaker body’s circumference, I glued sandpaper onto a mandrel machined to the housing diam- eter. After a few strokes on this sanding device, the window body conformed perfectly. The control cabinet and other styrene box- es were straightforward builds. The observation windows were punched out of clear styrene with a hollow-core punch.


CCVTs Of all the apparatus, the


CCVTs were probably the easiest to construct so (of course) I had to complicate it a bit by designing and fabricating the lattice stands completely out of styrene. I used a different auto fastener for the insulators. In all cases, these in- sulators need holes down their center so a brass wire can be in- serted. This brass wire serves to mount the insulators to the ap- paratus and to hold the top caps.


Depending on the in- sulator, I used the lathe to drill this hole or sometimes just held it in pliers and used the Dremel to drill the holes. Incidentally, I’ve found that my micro-


drills last much longer especially when drilling brass if I use a tiny amount of TapMagic cutting flu- id. They make it for both brass and aluminum, and it’s terrific. Even so, I’m now buying some sizes of drills by the dozen.


Center-break Disconnect The center-break disconnect presented another skills chal- lenge. I should have been satis- fied to make a static model, but after all the experience I was gaining, I designed a bell-crank mechanism that would allow the arms to prototypically open as they would when the circuit is being de-energized. I thought the arms would separate in the same direction (like a pair of double doors) and was far down the construction path when I re- alized that this was incorrect. I couldn’t find pictures in ABB’s literature showing the arms in the open position. The arms ac- tually swing opposite from each other (like a restaurant kitchen’s in and out doors). By the time I realized this, I had already cut a 45-degree angle on the arm ends, which now prevented them from separating in the new direc- tion. Even though the bell-cranks


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