Split-core current transformers offer a significant advantage in that they can be installed around existing conductors without disconnecting or cutting the cable. This makes them particularly suitable for retrofit projects, energy monitoring upgrades, and situations where the power cannot be interrupted. The installation procedure is straightforward but requires attention to several critical details.
The first step is to open the CT by simultaneously pressing the two side buttons or latch mechanism on the CT housing-. Open the CT wide enough to position it over the conductor to be monitored. Avoid touching the surfaces inside where the CT opens, as any oils or debris in that area can worsen accuracy-. Before closing the CT, ensure that the mating faces of the core are clean and free from damage and debris. The sections of the core must be properly aligned, and the clamping mechanism must be done up tightly to ensure stated performance.
Slide the CT over the conductor of the circuit to be measured, then close the CT by engaging the latch-. Verify that the CT is fully closed. The CT should be installed so that the side with the polarity marking (often a white dot or arrow) points toward the power source. For most CTs, this means the P1 primary connection should face the power source. If the CT is installed backwards, it will show negative current readings.
Secure the CT using the required mounting method, such as a mounting bracket kit, bolt mounting, or DIN rail mounting, depending on the CT model and installation environment-. Do not force the CT over the primary conductor, as this could damage the insulation on the CT. Allow for reasonable clearance on the outside of the CT and do not force it between adjacent conductors.
A critical safety requirement for split-core CTs is that the secondary circuit must never be left open. Open current transformers can develop hazardous voltage on the secondary terminals and may damage equipment or create a shock hazard. If the CT must be installed without the secondary wiring connections made, install a shorting link between the secondary connections and only remove it when final secondary connections are made.
For three-phase applications, install split-core CTs on each phase conductor. When metering a three-phase system, the CTs should be positioned around the conductors of L1, L2, and L3 respectively. A single CT can sometimes be used on one phase if the three-phase load is balanced, but this approach reduces accuracy if the load is unbalanced.