Modular residual current device

Thanks to its design, the modular residual current device type A (MRCD) 5SV8101-6KK is compatible with all molded case circuit breaker designs and can therefore be combined with 3VA1 molded case circuit breakers/switch disconnectors and with molded case circuit breakers from the 3VA2 series.

The modular residual current device is installed on a DIN rail (35 mm) as close as possible to the molded case circuit breaker/switch disconnector.

Operating principle

The modular residual current device is connected to a summation current transformer through which all live conductors (including neutral conductor where applicable) must be routed. The residual current is detected in the summation current transformer and transferred to the MRCD. If this current exceeds the limit value for the set rated residual current IΔn, the residual current device trips the molded case circuit breaker/switch disconnector by means of a shunt trip or undervoltage release.

Front view

Description of front panel view

Display of ready-to-operate and tripped and alarm states

The status of LED ① indicates whether the device is ready to operate or has tripped:

  • Green LED: The device is in operation.

  • Red LED: The set residual current has exceeded the response current, the device has tripped.

LED ② is an alarm indication:

  • Yellow LED: The set residual current has exceeded the response current alarm threshold.

Parameterization of the MRCD

For a description of MRCD parameterization procedures and other operating options, please refer to the operating instructions for the unit.

Summation current transformer


Summation current transformer 5SV8702-0KK (35 mm inside diameter)

Suitable summation current transformers

Depending on the rated operational current or maximum current of the circuit to be monitored, the following summation current transformers can be used:


Alignment of conductors in the summation current transformer

In order to prevent measurement errors or spurious tripping, it is important to ensure that the conductors are properly aligned or arranged in the summation current transformer.



The summation current transformer used for the application must have an inside diameter which is at least 1.5 times larger than the outside diameter of the conductors which pass through it.

When installing the MRCD, the summation current transformer and the release, make sure that they are positioned as close as possible to one another so that the cables from the MRCD to the transformer and from the MRCD to the molded case circuit breaker/switch disconnector are as short as possible (please observe the specified minimum clearances!) Further information about the cables to be used is available on request.

Combinations of molded case circuit breaker, MRCD and shunt trip/undervoltage release

Modular residual current devices, molded case circuit breakers, and shunt trips or undervoltage releases UVR can be combined as indicated in the tables below:



Suitability for use with 3VA23 and 3VA24 molded case circuit breakers on request

Example of wiring

The circuit diagram below shows a typical MRCD circuit with an undervoltage release.

The MRCD has a separate power supply (230 V) in the example application.


LED ready to operate and tripped display

LED alarm display

Reset button

Test button

Setting button for alarm/frequency

Setting button for auto (reclose) for alarm

Setting button for factory setting (0.03 A, instantaneous)

Setting button for residual current

Setting button for non-tripping time