BENDER WR Transformer Selection

The conductor should be aligned with the center of the inner hole of the transformer as much as possible to avoid eccentricity. Eccentricity can lead to uneven magnetic field distribution and reduce measurement accuracy. A conductor can only be bent within the minimum bending radius specified by the manufacturer, excessive bending may damage insulation or alter magnetic field distribution. For multiple conductors, it should be ensured that they are tightly arranged to avoid the formation of additional current loops. If the monitored circuit contains a PE line, the PE line must bypass the transformer and cannot be threaded through. For the busbar system, the busbar should pass through the inner hole smoothly to avoid friction with the inner wall of the transformer. The installation location should avoid strong vibration, high temperature, humidity, and corrosive gases. Transformers can be installed in any position, but it should be ensured that the screws are firmly fixed to prevent loosening during operation.

Selection verification when replacing discontinued modules

If you are replacing a discontinued measuring current transformer or residual current monitoring module, you cannot just look at the external dimensions. The following items should be carefully checked: whether the original system evaluator model is RCM, RCMS, or EDS; Whether the transformer ratio and accuracy level match; Can the inner hole size pass through existing cables or busbars; Is the load current ≥ 500 A and does it require SP shielding type; Is the secondary side connection method two-wire or other; Whether the cable length exceeds the allowable value; Does the shielding layer require single ended grounding; Is the installation space sufficient; Is the ambient temperature within the allowable range; Whether the short-term thermal current and dynamic current meet the system's short-circuit capacity.

If the original system is an IT ungrounded system for insulation fault location, it is necessary to confirm whether the new transformer is suitable for EDS positioning current measurement. If the original system is a TN/TT system for residual current monitoring, it is necessary to confirm the compatibility between the new transformer and the RCM/RCMS evaluator. If the original system uses busbars, it is recommended to prioritize the WR... SP series. If the original system cable is long, shielded cables should be used and single ended with PE, with a length controlled within 40 meters. If the original system requires high accuracy, it should be confirmed whether accuracy level 5 is met. If there are DC components such as frequency converters and UPS in the system, it should be confirmed whether the combination of evaluators and transformers supports AC/DC sensitive monitoring.

Common troubleshooting

1. Residual current monitoring false alarm. Check if the PE line passes through the transformer, if the N line is mixed with other circuits, if the conductor does not pass through in the correct direction, if the shielding layer is grounded at both ends, and if there is interference from high current busbars or frequency converters nearby. If the load current is high, consider replacing the WR... SP shielded type.

2. EDS positioning is inaccurate. Check whether each branch transformer only passes through the conductor of this branch, whether there are multiple branches mixed, whether the P1/P2 directions are consistent, whether the positioning current is sufficient, and whether the address and channel settings of the evaluator are correct. If the signal is weak, check whether the inner hole of the transformer is too large, whether the conductor is eccentric, and whether the connecting cable is too long.

3. The measured value is low or zero. Check whether the conductors pass through at the same time, whether the N wire is missing, whether the PE wire is mistakenly threaded, whether the secondary side wiring is loose, and whether the polarity is reversed. If it is zero, it may be a fault in the input channel of the evaluator or an open circuit on the secondary side of the transformer.

4. The measured values fluctuate greatly. Check for high-power equipment start stop, frequency converter carrier interference, busbar vibration, and poor grounding nearby. Use shielded cables and single ended grounding, and if necessary, add filtering or adjust the response delay of the evaluator.

5. The transformer heats up or makes abnormal noises. Check if the load current exceeds the rated continuous thermal current of 100 A, if the conductor is rubbing against the inner hole, if the screws are loose, and if the installation environment temperature is too high. If the short-term fault current exceeds 14 kA/1 s or dynamic 35 kA/30 ms, it may damage the transformer.

6. The shielding effect of SP is not significant. Check whether the shielding layer is reliably grounded, whether the shielding cable passes through the transformer, and whether the SP type installation direction is correct. The shielding layer should be connected to PE at one end and cannot form a ground loop.

7. The evaluator displays over range. Check whether the residual current is truly too high, whether the response value is set too low, whether the conductor is threaded incorrectly, and whether there is an external strong magnetic field. If it is a busbar system, confirm whether SP type is selected.