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

    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 electronic components such as electronic reactances for lighting, electronic light intensity variators, electronic ignitors, AC/DC power supplies, frequency variators (installed in computers, energy-saving lamps, air conditioners, TVs, etc.) which 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 switch

    orange check iconAC-type differential switches 

    Not suitable for installations with electronic receivers which nowadays include almost all industrial and domestic supplies… 3.5 ITC-24 RBT. Not permitted in Germany and Switzerland EN61008 and EN61009 ANNEX ZB). The first differential devices on the market were the AC-type, sensitive only to alternating leakage currents. They also incorporated protection against certain atmospheric and manoeuvring transient overvoltages (circuit connection and disconnection).Until they began to be incorporated into frequency converter networks, electronic ignitors, computers, etc., which may have leaks of pulsating direct currents (rectified alternating currents) with or without a superimposed continuous component that are as dangerous as alternating currents. These currents with or without a superimposed continuous component cause dangerous voltages for people, which are not detected by this kind of differential switch.

    orange check icon A-type differential switches 

    Suitable for installations with electronic receivers Art. 3.5 ITC-24 RBT. In order to solve the problems mentioned above, of non-action due to leaks of pulsating continuous currents with or without a continuous component, type-A differential switches are used, improving the magnetic core so that these currents can be detected.

    orange check icon High Immunization Type-A Differential Switches 

    E.g. ABB AP-R-type, Circutor RGE-R or Schneider Superimmunized (SI) Differential Switches).

    Despite being used in installations with type A electronic differential elements, unexpected trips are still caused in installations subjected to strong electronic element loads such as electronic lighting reactances, variable speed drives, electronic ignitors, and a large number of computers. In addition to a lack of safety due to the blocking of the trip or obstructing of the differential switch when there are high-frequency leakage currents, preventing it from acting when there are other defects that are dangerous for people.

    To avoid these problems, these types of differential switches usually incorporate:

    orange check iconHigh frequency filters which prevent obstruction of the differential switch as well as unexpected trips due to the number of high-frequency emitting devices accumulated under each differential switch.

    orange check icon It also incorporates anenergy accumulation circuit that substantially increases its protection against transient overvoltages, which allows the vast majority of transient overvoltages caused by atmospheric and manoeuvring discharges to be overcome without tripping, differentiating them from a real defect in such a way that it does not open until it is real.

    orange check icon Its trigger curve approaches the limits set by Standard 61008-1.

    The installation of Immunized Type-A Differential Switches substantially reduces unexpected trips and improves safety for people by preventing the blocking (non-triggering) of the Differential switch in the event of a pulsating DC leakage or high frequency leakage.

    The use of more than one differential switch is recommended, in accordance with the BT-25 Guide of the Electrotechnical Regulation for LV

    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 advisable to provide individual differential protection.

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

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

    orange check icon Separate the kitchen and oven or air conditioning circuit from the rest.

    orange check icon Replace the differential switch that is tripping with a rearmable switch.

    orange check icon Electrification of terrace or garden. A differential switch separate from that of the indoor circuits.

    Other recommendations

    Avoid installing long cables under a single differential switch, reducing the leakage intensity to transient-type capacitive earth (LV manoeuvring) or permanent high frequency (harmonic currents).


    Recommendations for ensuring the safety of persons

    1. Press differential switch test button once a month.
    2. Ensure good grounding to guarantee that current does not cut off in the event of a fault (earth lines and electrodes).
    3. Maintain proper insulation as this ensures the capacity and isolation of the installation.
    4. Good connection between the earth conductor and the ground of the receiver to avoid voltages that are dangerous for people.
    5. Ensure continuity of the ground loop between the earth circuit and metallic masses.
  • 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.

    Then, you must turn on the power control switch (PCS). If it still trips when everything is switched off, call 900 333 999.

    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 by calling 900 333 999, 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.