Cabur control terminal blocks have been designed to allow power supply authorities and users to easily verify measuring instruments, without interrupting the power supply during inspection or during any replacement of the instruments.

Each terminal block consists of an insulating base supporting the terminals, made of a copper-zinc alloy, to which the voltmetric and ammetric circuits are connected, along with the devices for disconnection and short-circuit operations. Each terminal block is supplied with a transparent cover (made of cellulose acetate), equipped with special captive screws to allow the assembly to be sealed.

In the two-phase and three-phase terminal blocks, the insulating base is made of Kelon (an acronym for Keramic + Nylon). This is a nylon 6-based polymer, self-extinguishing UL94V-0, enriched with special ceramic microspheres and subsequently thermally stabilized. The presence of the microspheres and the thermal process make the product extremely resilient—rigid yet capable of withstanding impact and wear.

The phases are identified by different colors, which must be specified at the time of ordering.

With MCM series terminal blocks, the following can be performed:

• Disconnection, both upstream and downstream, of the measuring instruments
• Insertion of a reference instrument, either before or after the measuring instrument
• Branch connection, using standard sockets, from the four connection terminals
• Voltage transfer from the ammeter input to the knife switch, by means of a jumper to be installed

In normal operation, the voltmetric supplies are connected to terminals R-S-T, while the ammetric supplies are connected to terminals marked R1-R2, S1-S2, T1-T2. The instruments are connected to terminals 1 and 2. The vertical sliding bridges are closed, while the horizontal sliding bridges are open.

When inserting control instruments, proceed as follows:

• Using standard plugs, branch the voltmetric circuits of the reference instrument to the voltage sockets of the knife disconnectors or fuse-holder plug-in blocks;
• Connect the ammetric circuits of the control instrument to sockets 1 and R1 or 2 and R2, and similarly for the other phases;
• Then disconnect the corresponding vertical slider.

When replacing measuring instruments, it is first necessary to close the horizontal sliders, disconnect the vertical sliders, and open the knife switches.

The incoming and outgoing power connections are made at the rear of the terminal block (rear panel entry), with conductors passing through holes made in the insulating base of the terminal blocks.