How to wire the secondary side of an open-type current transformer
Aug 07, 2026| I. Basic Wiring Specifications
1. Terminal Definitions: S1 is the secondary side terminal with the same polarity, S2 is the non-polarity terminal, and wiring must follow the principle of subtracting polarity.
2. Conductor Requirements: Copper core conductors with a cross-sectional area ≥ 2.5mm² must be used. Using thin conductors is prohibited to avoid open circuits.
3. Grounding Requirements: S2 terminal must be reliably grounded at a single point. Multiple grounding points are prohibited to prevent circulating current interference with measurement accuracy.
II. Wiring Methods for Different Scenarios
1. Ammeter Connection Scenarios: S1 connects to the positive terminal of the ammeter, S2 connects to the negative terminal of the ammeter, and a separate grounding wire is led out from S2.
2. Electricity Meter Connection Scenarios: S1 connects to the current coil inlet terminal of the electricity meter, S2 connects to the current coil outlet terminal of the electricity meter, and S2 is reliably grounded to prevent reverse metering.
3. Protection Device Connection Scenario: Connect S1 to the positive terminal of the protection device's current input, and S2 to the negative terminal of the protection device's current input. The grounding wire is independently led out.
4. Three-Phase System Scenario: All S2 terminals of multiple current transformers are connected in parallel and then grounded at a single point using a star connection.
III. Core Safety Operation Points
1. Strictly follow the sequence of connecting the secondary lines first, then closing the current transformer openings, maintaining a closed secondary circuit throughout.
2. It is strictly forbidden to install easily disconnectable components such as fuses or switches in the secondary circuit to avoid circuit risks at the source.
3. After wiring is completed, use a multimeter to check the circuit continuity to confirm there are no loose connections or breaks before proceeding with subsequent installation operations.
