What are they and what is their scope?
The five rules serve as a reminder of the voltage suppression steps outlined in Annex II of Royal Decree 614/2001. They are applied after identifying the area and the components of the installation where the work will be carried out. Each step addresses a different problem: power supplies, reconnections, checking the electrical status, accidental energization, and exposure to nearby components.
This sequence does not authorize self-intervention nor does it replace the specific procedure. Operations to de-energize and restore power must be carried out by authorized workers and, in high-voltage situations, by qualified workers. The assessment must also consider the risks present during preparation, when all the conditions for working without power have not yet been established.
First rule: disconnect
The work area must be isolated from all relevant power sources. The analysis must identify alternative power supplies, return paths, and energy storage equipment. An open switch or a stopped machine does not, by itself, guarantee that all affected elements have been isolated. Identification must be supported by appropriate documentation and verified on the actual installation.
The regulations address components that may remain energized after disconnection, such as capacitors, and require their handling using appropriate devices. This procedure is part of the technical process and requires the necessary equipment and personnel. The planning phase must resolve this issue before granting access, preventing the apparent absence of operation from being used as sufficient evidence of electrical safety.
Second rule: prevent feedback
The devices used for disconnection must be secured against possible reconnection, preferably by locking the mechanism, with signaling when necessary. The aim is to maintain the achieved condition even if another person intervenes or a remote control is used. The protection must consider auxiliary power sources and automated systems capable of altering the state of the installation.
Lockout /tagout helps organize energy control, but it must be adapted to the installation and the work. A tag alone does not offer the same physical function as a lockout/tagout device. When regulations allow equivalent measures, their effectiveness must be addressed within the established procedure; it is not appropriate to improvise them during an intervention due to a lack of suitable devices.
Third rule: check for absence of tension
The absence of voltage must be verified on the affected live components, in the work area or as close to it as possible, using appropriate devices and procedures. It cannot be inferred from a black screen, a command sent to the system, or verbal confirmation. Verification is a separate step, distinct from disconnection and ensuring against reconnection.
Annex II establishes specific requirements, including those relating to verifying the operation of high-voltage devices. The equipment used must be appropriate and in working order. If the identification of conductors is doubtful or the result does not match expectations, the stage should not be considered complete; preparations must be halted and the discrepancy resolved technically.
Fourth and fifth rules
Earthing and short-circuiting are required in high-voltage installations and in low-voltage installations that may become accidentally energized by induction or other reasons, in accordance with Annex II. Their necessity and implementation must be determined in the applicable procedure. It is not acceptable to omit them out of habit or to treat all low-voltage installations as having the same conditions.
The final stage protects against nearby live components and delimits the area with safety signage. Barriers, distances, and other measures must be appropriate for the installation and the anticipated movement of people, tools, and materials. Delimitation does not replace the necessary protection against electrical contact or other hazards associated with the work.
Practical example
A company schedules the replacement of a component and discovers that the equipment has both main and auxiliary power supplies. Before beginning work, the responsible personnel identify both, prepare their isolation, and define the measures to maintain it. They then perform the necessary checks and the remaining applicable steps, including those related to nearby components that will remain in service.
Authorization to begin occurs when the procedure confirms the expected conditions, not upon pressing the first switch. If an unidentified power supply is encountered during preparation, the work must be reassessed. This example illustrates an organizational decision; it does not constitute a sufficient operational sequence for intervention in a specific installation, whose characteristics and risks must be assessed by competent personnel.
Maintaining conditions and restoring tension
During the work, the established safety measures must be maintained, and personnel changes, shift changes, or simultaneous interventions must be controlled. Communication is especially important when several people depend on the same isolation area. The procedure must prevent one person from considering their task complete and restoring power while another continues working within the protected zone.
Restoring power has its own regulated process: after the work is completed, non-essential personnel must be removed, and tools and equipment must be collected. Once one of the measures taken to work without power is removed, the affected area must be considered energized. Therefore, closing the work area requires coordination and a controlled decision, not simply an informal reversal of actions.
Common mistakes
The most significant errors are confusing shutdown with isolation, omitting auxiliary sources, relying on unverified indicators, and withdrawing measures without coordination. It is also incorrect to use the five rules as a generic list that anyone can follow. The distinction between authorization and qualification determines who can perform operations based on the type of facility and task.
Preparation may involve exposure to electric arcs and other hazards before safe conditions are established. Protective measures must address this phase. System quality is verified by reviewing procedures, competence, equipment, and actual application, not simply by maintaining a signed checklist that doesn’t reflect how the intervention was carried out.
