On exceptional occasions, the power supply may be affected by unforeseen cuts. Supply interruptions are caused by incidents arising anywhere along the supply chain: at power stations, along the transport or distribution network or in the customer’s own installation.

To resolve any supply interruption as quickly as possible, we need to establish whether the fault has occurred in the customer’s or distributor’s installation.

  • Identify the components

    Power Control Switch (PCS)

    This is located next to the General Control Panel and Protective Box. It controls and limits the contracted power. If the sum of the power connected simultaneously exceeds the contracted amount this device will respond by leaving the particular installation without power.

    General Automatic Switch (GAS)

    This protects the house’s entire installation from overloads and short-circuits. It is a switch that has been added recently.

    Differential Switch (DS)

    This quickly protects and disconnects the electric installation where there is an earth fault, keeping people safe from harm.

    Small Automatic Switches (SASs)

    These protect against incidents caused by short-circuits and overloads in each of the internal circuits (lighting, heating, household appliances, etc.). The number of SCBs will depend on the extent of electrification or complexity of the electrical installation of the house or premises. 

  • Information on Differential Switches

    Differential switches must be present in all domestic electrical installations and serve to protect people from the risk of death caused by “direct contact” with the metal cases of electrical appliances accidentally subject to an electrical current due to an insulation error in the installation, ultimately protecting against fires which may be caused by these bypasses due to insulation errors.


    Differential switches protect people first and installations second


    In recent years, a major change has been observed in household appliances and other equipment that have begun to be used in homes. Above all, we have begun to use different electronic components such as electronic reactances for lighting, electronic light intensity variators, electronic igniters, power supplies and frequency variators (installed in computers, energy-saving lamps, air conditioners, TVs, music players, etc.) which, together with the presence of storms, often cause differential switches to trip unexpectedly.

    In order to adapt to these new receivers and to avoid unexpected trips as much as possible, differential switches have evolved to improve their operation.


    Type of domestic differential switches for domestic use


    orange check iconAC-type differential switches. The symbol for this is 

    This type of residual current device is only sensitive to alternate leakage current. They were the first to reach the market and must be installed as a minimum requirement in any household installation. They work correctly in installations that have practically no electronic components and are also located in zones where storms are not frequent. However, if the house is located in a zone where there are frequent summer storms and atmospheric discharges (lightning) that cause power surges and earth leakage, or if the interior installation has several receptors with electronic components (smart electrical appliances, low-consumption or dimmable lighting, computer power supplies, air conditioning units, music player, television, etc.) where there could be pulsed direct current leakage (which can be as dangerous as alternate current but is not detected by AC residual current devices), this type of residual current device is not suitable for installations with electronic components or in areas where there are frequent storms, and they will trigger when not required due to the distortion caused by these receptors. In fact, they are no longer permitted in some countries, like Germany and Switzerland.


    orange check icon A-type differential switches. The symbol for this is 

    This type of differential switch is sensitive to alternating and continuous leakage currents and also includes a high-frequency filter which improves its magnetic core to prevent unexpected trips caused by harmonic currents that are generated when there are different receptors with electronic components. These features mean this type of differential switch is suitable for installations with receivers with electronic components.


    orange check icon Superimmunized A-Type differential switches. The symbos for this is  and 

    This type of differential switch is the same as A-type differential switches, but their trigger curve approaches the limits set by Standard 61008-1, which enables them to function correctly in installations with strong loads of receptors with electronic components, such as the electronic lighting reactances, variable speed drives, electronic igniters and a large number of computers.

    This type of differential switch also includes an energy accumulation circuit which significantly reduces unexpected trips caused by occasional earth leakages associated with transient surges caused primarily by atmospheric discharges, differentiating them from a real defect. This means this type of differential switch is sensitive to alternating and continuous leakage currents, greatly reducing unexpected trips, so this type of differential switch is more suitable to installations with receivers with electronic components or which are located in areas where storms are common.


    There are other types of differential switch, such as “Delayed” (S-type) for installation upstream of other differential switches; “Industrial” (B- and F-type) for recharging vehicles, engine ignitions and variable speed drives; and “Rearmable” for unattended installations that require a guarantee of continuity of service, but are more generally used in industrial or commercial installations. But in domestic supplies, to maximise protection of people and prevent unexpected tips, the conclusion is that:


    For domestic use, it is recommended always to install superimmunized differential switches


    Installation recommendations


    In accordance with the ITC-BT-25 Guide of the Electrotechnical Regulations for LV (low voltage) in domestic installations, the following instructions are recommended to be followed:

    orange check icon To prevent a single differential switch from disconnecting certain devices such as computer equipment, refrigerators and freezers. For this type of circuit it is highly advisable always to provide individual differential protection for the installation.

    orange check icon Where there is a single differential switch or several in parallel, they will have an instantaneous trip (0.05s) and a maximum sensitivity (differential-residual intensity) of 30 mA. But if there are differential switches installed in series, there must be selectivity between them. This is achieved if the differential switch located upstream has a certain delay in its activity (S-type) and if its sensitivity is at least three times greater than that of differential switches located downstream.

    orange check icon Never install the differential switches upstream of the surge protections.

    orange check icon At least one differential switch shall be fitted for every five installed circuits.

    orange check icon For the electrification of a terrace, garden or exterior installation, at least one differential switch independent of the interior circuits must be installed.

    orange check icon In the event of frequent unexpected tripping and after checking that this is not due to insulation faults or differential misalignment:

    • Separate the kitchen and oven or air conditioning circuit from the rest.
    • Replace the differential switch that trips for a superimmunized switch, and if it is already a superimmunized switch, replace with another superimmunized switch, but a “Rearmable” one.

    orange check icon Avoid installing excessively long cables downstream of a differential switch in order to reduce the intensity of the earth leakage currents.


    Recommendations for ensuring the safety of persons


    1. Ensure a good grounding, which guarantees the continuity of the current in the event of a defect, both for the protection lines (green/yellow earth cable) and the electrodes (earth bars).
    2. Maintain proper insulation, both for the different apparatus connected to our interior installation and the cabling and fuse boxes it is composed of, as they establish the capacity and insulation of the installation.
    3. Ensure a good connection between the protective conductor and the ground of the receiver to avoid dangerous voltages for people who may come into contact with the cases of the different receivers and apparatus.
    4. Ensure continuity of the ground loop between the protective earth circuit and metallic masses of the different receivers or apparatus.
    5. Press the “Test” button of each differential switch once per month to ensure it is working properly.


  • Initial checks


    Once the components have been identified, any switch on the panel found down must be switched up.

    If no devices trip again, the problem is resolved.

    If, on the other hand, a device goes down again, continue with the checks.



    Disconnect and switch off all the switches: the General Switch (GAS), the Differential Switch (DS) and the SASs.

    If you don’t have electricity at home, you can now access your private area to check if your Power Control Switch (ICP) has been disconnected and, if so, reconnect it. If you don’t have electricty after a few minutes, please notify the issue at your private area.

    If the PCS does not trip, you must turn on the General Automatic Switch (GAS). If this trips it means there is a fault in some part of the installation, so you must call an authorised electrician.

    If the GAS does not trip, turn on the Differential Switch (DS). If this trips it means there is a fault in some part of the installation, so you must call an authorised electrician.

    If the DS does not trip, switch the Small Circuit-Breakers (SCBs) on, one by one. If one of the SAS trips it means there is a fault in the corresponding circuit, so you will need to call an authorised electrician.

    If none of the SAS trip, you can connect the receivers (light, electrical appliances, boiler, etc.) one by one until you locate the fault. If the SAS turns off when you connect the receiver appliance, this means the appliance is faulty and should be repaired.


    listaIf you are still unable to locate the fault, you must contact a private installer.

    Generally, when everything in the house is connected and the CPS trips, this is because the power demanded by the electrical appliances is greater than the amount of contracted power.

    One temporary solution to this problem is to disconnect some appliances to reduce the amount of power required, to prevent the PCS from tripping. In order to connect all appliances simultaneously, you must ask a supplier to increase the amount of contracted power you have.

  • How to respond

    A network supply interruption must be reported at your private area, as soon as the following are detected:

    listaAn area without service.

    listaA building which is partially or totally without service.

    listaIncidents in electrical installations or any other hazardous situation.

    Whenever a fault is detected (through the company’s own systems or a customer communication), we take measures to restore the service as quickly as possible.

    Once the maintenance team reaches the site of the fault, they evaluate the problem and estimate the amount of time it will take to resolve. In fact, where the network’s configuration so allows, the service will be re-established via other substations, lines or transformer stations that are unaffected by the fault before the repair work gets under way, so customers will have a power supply once that work starts.

    In emergency situations caused by atmospheric conditions, our company works in co-ordination with the emergency services who put the appropriate protocols in place for each situation.

  • Tips

    If there is a blackout, it is recommended that you follow the tips below:

    listaIt is useful to have torches and replacement batteries to hand, to avoid having to use candles, thus reducing the risk of fire.

    listaDo not open the fridge or freezer, to conserve the cold and preserve the food.

    listaTo prevent appliances from being damaged when the service is resumed, it is useful to unplug them until the power comes back on.

    listaFor safety reasons, do not touch the electricity panel or operate any of its mechanisms with wet or damp hands.