Control panel tip

Personal safety in the Control Cabinet – How you can provide the best possible protection for system operators? Tips on residual current protection in case of leakage currents.
Personal Safety in the Control Cabinet

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Even if control cubicles are designed by experts, it is essential for them to ensure that the finished product is user-friendly. Not every system operator can intuitively recognize potential hazards caused by electrical current and prevent them like an electrical expert. That is why control cabinet builders must ensure that even third-party personnel is protected from accidents in case of direct or indirect contact. The DIN VDE 0100-410 VDE 0100-410:2018-10 standard defines which precautions need to be taken for personal safety in the control cabinet.

Tips for you!

Personal safety in the control cabinet can basically be divided up into three levels:

 

  • Protection precautions for basic protection: They are intended to prevent direct contact with live parts. This includes measures such as insulation of live parts or mounting with sufficiently large clearance.
  • Protection precautions for fault protection: These protective measures prevent indirect contact of other conductive live parts. Fault protection comes into play if basic protection fails and includes protective isolation.
  • Additional protection: If both basic and fault protection fail, or if a system is subject to improper use, the enhanced protection prevents risk for personnel. Effective protection is provided by highly sensitive residual current circuit breakers (RCCBs), which in case of residual currents disconnect the circuit from the network and prevent electrical accidents.

An RCCB measures and compares the level of the input and return current. If the currents differ, there is possibly a dangerous fault. If the difference between the output and input current exceeds the rated residual current, the RCCB triggers, disconnecting the monitored circuit from the infeed. With RCCBs for additional protection, the rated residual current is 30 mA. Through quick disconnection from the supply network, the RCCB prevents electrical fires and danger to personnel due to electrical shock.

Even in error-free operating electrical systems, residual currents can occur, so-called leakage currents. During operation, they flow to ground or to an external conductive part. An RCCB is not capable of distinguishing between operation-related leakage currents and residual currents caused by faults. If the leakage current exceeds the rated residual current of the RCCB, it will trip. Leakage currents are caused by electrical parts:

  • Components of drive technology
  • Power supply components
  • Interference suppression modules

They can occur both dynamically and statically. Dynamic leakage currents occur, for example, when switching devices with filter switching, and reach very high values for a short time. Static leakage currents are constant when operating a system.

The impairment of RCCBs through leakage currents can be prevented by reducing static leakage currents to a maximum of 30% of the rated residual current of the RCCB. So with the lowering of current leakages, you can achieve error-free function of the RCCB and thus a high level of reliable operation and system availability.

The consequences the installed components have for leakage currents of an electrical system should already be taken into account in the planning phase. The following measures are suitable for minimizing them: 

  • Use of low leakage current filters
  • Minimize the cable lengths
  • Use of short motor cable lengths
  • Adjustment of the switching frequency
  • Installation of a separate function transmitter, which is treated like a neutral conductor

Are you interested in additional measures for lowering the leakage current, or other questions on all aspects of personal safety in the control cabinet? You can find additional information on relevant topics such as residual current safety, leakage currents, as well as EMC and personal safety, in our White Paper.

Do you want more information?

Contact:
Gerhard Flierl
Manager Integrated Control Panels

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