Today's manufacturing processes have been incorporating much more efficient systems thanks to the evolution of power electronics. However, this type of solution generates disturbances that sometimes cause the unexpected tripping of the residual-current devices (RCD’s) for no reason.

In the following video, we describe the causes that can lead to unexpected tripping and what solutions you can install to prevent this from happening, ensuring the continuity of supply of your installation and avoiding cost overruns.

What features does a residual-current device need to avoid unexpected tripping?

Many of the residual current trips in facilities are due to the new technologies in use in the connected loads. Many of them currently rely on power electronics for their control, which improve their performance but create a series of problems in the installation

Loads such as variable speed drives, solar inverters or electric vehicle chargers are some examples of this type of technology.

These types of loads require the connection of EMI filters to prevent electrical noise from being coupled to the installation in order to ensure its operation.

On the other hand, simply because they are connected, they generate an earth leakage or fault current, which increases depending on the voltage level of the installation and even in the presence of voltage harmonics, and can cause the residual current protection to trip unexpectedly.

For this reason, RCD’s must be prepared to prevent unexpected tripping, caused by the normal operation of the loads, and even to discard other transient events that arise during the connection or disconnection of the loads.

–
RGU-10A

Type A ultraimmunized residual current protection & monitoring relay

To avoid unexpected tripping in your installation, we recommend installing ultra-immunised protection relays, as the added features of this type of solution will allow you to ensure maximum continuity of supply, avoiding production stoppages that affect the economic viability of your activity.

For this reason, the new residual current protection relay type A RGU-10A responds to these needs by means of three features that provide a greater guarantee to ensure continuity of service:

Trip margin between 85%-100% of the leakage value

Those devices without an ultra-immunised system may trip due to a fault greater than 50% of their sensitivity, as required by the RCS’s regulations, and may trip with a leakage current much lower than the tripping limit.

As an example, in switchboards where there are several lines, it could happen that the accumulation of leakage current to earth is less than 30 mA and that the device trips at 15 mA, a threshold much lower than the 30 mA above which the current begins to be dangerous for human beings.

Therefore, there is a real fault that is not dangerous for people or for the installation that is causing the RCD to trip, causing service stoppages and indirect costs to the installation.

To avoid this effect, we propose the installation of ultra-immunised residual current devices, which guarantee tripping from 85% of the device sensitivity. In other words, following the previous example, these devices ensure tripping from currents above 25 mA and never exceeding the 30 mA required by the protection system, bringing the tripping level as close as possible to the actual rating of the residual current protection device.

Ultra-immunised RCD’s offer a better frequency response because they discriminate all faults with frequencies above 50/60 Hz. High-frequency currents can affect the measurement of the toroidal transformer, leading to erroneous measurements and unexpected tripping.

For this reason, by "making them invisible" to harmonic currents, we guarantee continuity of supply, tripping only with real fault values at 50 Hz.

Ultra-immunised residual current devices are not affected by transient disturbances that may appear in electrical installations, such as those associated with environmental factors like lightning strikes or those created by switching of loads present in the installation, whether inductive or capacitive loads.

It is common for the distribution grid to be affected by external phenomena such as lightning strikes, which induce fleeting overcurrent, or transients, which clear very quickly. These disturbances can affect the relay, which is not prepared to deal with this type of signal, leading to unexpected tripping.

For this reason, the ultra-immunised system ensures the continuity of supply, not affecting the installed RCDs when a transient effect of up to 3 kA and 8/20 µs duration appears.

Easier to analize

The RGU-10A residual current protection relay makes it even easier to interpret data than its predecessor RGU-10.

Its backlit display changes colour depending on the status of the device to identify the status of the line to be measured at a glance, showing red when the relay has tripped due to accumulation of leakage current, yellow when the fault level exceeds the pre-alarm limit, blue when setting and white when in non-alarm monitoring mode (Standby).

The pre-alarm level is fully adjustable to a customised set point from 20% to 100% of the set trip sensitivity allowing, before reaching the trip point, preventive maintenance to be carried out in anticipation of a shutdown of the installation.

Where could I install it?

The RGU-10A relay is the most complete type A protection to guarantee the safety of people and ensure the continuity of supply in electrical installations.

Its ultra-immunised system guarantees that a trip will only occur when it is totally necessary, avoiding economic losses due to unexpected tripping.