Five safety rules

When working in and on electrical systems, certain rules apply in many countries to avoid electrical accidents , which are essentially summarized in five safety rules .

The five safety rules

Unlock

"Isolation" is the term used to describe the all-pole and all-round disconnection of an electrical system from live parts. An isolating distance of different lengths must be established between live and dead system parts, depending on the operating voltage.

For safety reasons, when working on electrical equipment from a certain operating voltage or operating current , it must always be disconnected, provided that no special measures are taken for working under voltage . In Germany, Austria and Switzerland it is 50  V alternating voltage or 120 V direct voltage , in Switzerland it is also currents above 2  A (low voltage installation ordinance, NIV).

The isolation can be done by operating the main switch, the professional removal of fuses, the pulling of plug connections, in high-voltage systems by the disconnector provided for this purpose . If the worker does not activate himself, as is the case in some cases in high-voltage systems , and the activation is triggered by a control center via remote control, work may only be started once the activation has been confirmed verbally, by telephone, in writing or by telex . It is not permissible to agree on a point in time at which activation should take place.

Secure against being switched on again

A “do not switch” sticker as an example

In order to avoid that a system that is currently being worked on is accidentally switched on again, it must be reliably prevented from being switched on again and this must be indicated with a prohibition sign before it is switched on again. For legal reasons, a distinction is made in terms of the scope of protection as to whether the facility is accessible to laypersons in electrical engineering or whether it is located in a closed area, room or area that is only accessible to qualified electricians .

Switching on again in areas that are freely accessible to laypersons, such as the sub-distribution in the household fuse box, must always be carried out in such a way that the lock can only be removed by using additional tools. Simply switching off the circuit breaker is not sufficient. A line circuit breaker should always be secured against being switched on by disconnecting the outgoing line or by means of a switch lock , or the unscrewed fuses should be replaced by lockable blocking elements. If a disconnection device that is freely accessible to laypeople, such as the fuse box in the household, is merely "secured" against being switched on again with an adhesive label or a simple notice, this is considered to be grossly negligent in Germany .

If the switchgear is in a locked area that is only accessible to qualified electricians - this is always the case with systems with high voltage and in electrical operating rooms - it is sufficient to put up a prohibition sign against restarting for the duration of the work. This sign should also contain information about who is authorized to remove this prohibition sign after the work is finished. In remote-controlled switchgear , a virtual switch lock is set in the control area through a configuration, which indicates to the operator in the control center that it is not allowed to switch on.

Determine the absence of tension

The person working on site must use suitable measuring / testing equipment such as the voltage tester to determine that all poles are de-energized. This is important because it is used to determine whether there is still residual voltage from electrical devices (e.g. frequency converters ) or whether the wrong line has been accidentally disconnected.

When voltage detectors for systems up to 1 kV is two-pole versions (with glow lamp and Tauchspulmesswerk , with glow lamp and moving-coil; with LEDs and function test). An existing voltage is indicated either by a glowing lamp, by a measuring device or by light-emitting diodes. These devices can also be used to determine the voltage level of the system. Newer testing devices have an unbalance motor , the frequency of which depends on the voltage level to be measured.

Voltage testers for systems with nominal voltages above 1 kV are single-pole. The measuring device is typically designed in the form of an electrically insulated lance up to several meters long, which is brought up to the high-voltage conductor by hand. The presence of the high voltage is indicated optically and acoustically by a test circuit installed in the lance by means of capacitive voltage division. The use of low-voltage measuring devices such as multimeters and other test and measuring devices of measurement categories CAT I to IV is prohibited due to the high risk of accidents in high-voltage systems.

The voltage testers used must be tested for functionality on a definitely live source before and after use. Before, because the voltage tester could be defective, and then because it could have suffered a defect while in use. Single-pole high- voltage testers for nominal voltages above 1 kV have a built-in test device, which simplifies the function test.

Are short-circuit-proof quick earth electrodes used in power engineering systems such as B. spring-controlled earthing disconnectors in switchgear, the actuation of the earth electrode counts as "determining the absence of voltage".

Earth and short-circuit

Once the absence of voltage has been established, the conductors and the earthing system are connected to one another using short-circuit-proof earthing and short- circuiting devices such as an earthing rod . This measure has the effect that if the upstream overcurrent protection devices are switched on inadvertently, lines lying in parallel, such as overhead lines , are not charged atmospherically due to the capacitive coupling or influence . The earth connection, if it is carried out with movable equipment such as the earthing rod, should be close to and within sight of the work site. In the case of high voltage, this may even have to be done several times and not just at one point.

It should also be noted that earthed first and then short-circuited. In systems with low voltage , with the exception of overhead lines and distribution networks, grounding and short-circuiting may be omitted if rules 1 to 3 have been carried out in accordance with regulations (Switzerland: only " if there is no risk of voltage transmission or feedback ", cf. Art. 72 Paragraph 4 Heavy Current Ordinance). In principle, these measures must also be taken at low voltage (<1 kV) if there is a risk that the system could still be energized, e.g. B. if 2 overhead lines cross or emergency power generators are available. The first bridging in emergency power is usually done by battery systems, which can still be easily determined ( determine whether there is no voltage ). The large aggregates (e.g. ship diesels in hospitals, etc.) first require a certain amount of time (sometimes several minutes) to start up and only then switch on.

Cover or cordon off neighboring, live parts

In the case of systems below 1 kV, insulating cloths, hoses, plastic covers, etc. are sufficient for covering. This part can also be neglected if items 1 to 3 are properly executed for voltages below 1 kV AC or 1.5 kV DC.

When working in electrical systems with voltages above 1 kV, additional covers can be made with specially designed insulation mats, which provide sufficient protection against contact with neighboring system parts in the medium voltage range . Appropriate work clothing must be worn depending on the situation. Additional warning signs, ropes or shut-off devices may be required in systems with high and maximum voltage, which visibly delimit the precise and safe working area and which must not be left. In special cases, such as spatially cramped conditions, the additional deployment of a control person who is not directly involved in the work may be necessary, who continuously monitors compliance with the safety distances during the work and can point out inattentions.

Measures before switching on again

• Remove tools and aids
• Leave the danger area
• First remove short-circuiting and earthing at the place of work, then at the other points
• First lift the earthing cable from the system parts, then from the earth
• System parts and lines without an earthing cable (if present) must no longer be touched
• Reinstall removed protective covers and safety signs
• Do not remove protective measures at the switching points until the work stations have been reported to be vacant

• When working with several employees, it must be ensured that nobody is in the danger zone.

Country-specific details

Germany

In Germany these are the five safety rules , which are summarized as follows according to the DIN VDE 0105 series of standards :

1. Unlock
2. Secure against being switched on again
3. Determine all-pole absence of voltage
4. Earth and short-circuit
5. Cover or cordon off neighboring, live parts

These five safety rules should be applied in the order given above before working on electrical systems. After the work, they are picked up in the reverse order.

These rules are assumed to be known to every qualified electrician. Most of the accidents reported in Germany result from failure to observe rules 1 (23.7%), 3 (12.5%) and 5 (8.8%).

The determination of the absence of voltage in low-voltage networks (electrical systems with operating voltages of up to 1 kV alternating or 1.5 kV direct voltage) may only be carried out by a qualified electrician or an electrician for specified activities (EFffT). In the case of high-voltage systems with operating voltages greater than 1 kV, the absence of voltage may only be determined by a qualified electrician.

Special technical and organizational measures are generally not required when working under voltage if the following conditions are met:

• both the voltage between the active parts and the voltage between the active parts and earth is not higher than 50 V AC or 120 V DC (SELV or PELV); or
• the short-circuit current at the work site does not exceed 3 mA alternating current (effective value) or 12 mA direct current; or
• the energy does not exceed 350 mJ; or
• the circuits are intrinsically safe in accordance with DIN EN 60079-14 (VDE 0165-1) and DIN EN 61241-14 (VDE 0165-2).

Switching language / switching conversation

The so-called switching language standardizes terms and designations within a "network" area. This clearly regulates what is meant and what is to be carried out; A uniform switching language applies, and uniform terms apply in a switching call or in a written implementation and cancellation instruction. This serves to avoid mix-ups and thus to prevent electrical accidents.

In the new federal states , the general service instructions for power plant operations (ADK) and the NNÜ [formerly: general service instructions for network operations (ADN)] usually apply. This does not apply in the old federal states , where every network or power plant operator has its own switching regime. For example, in the ADK and NNÜ (formerly ADN) a strict distinction is made between two types of earthing and short-circuiting measures: ready-to-use "fmb" (ie earthed at the switching points) and ready-to-release "fgb" (also earthed at the work stations - visible earth) .

Second example: a disconnector is either closed or opened and a circuit breaker is switched on or off .

Third example: In the "area" of the ADK / NNÜ, switching commands and commands must be repeated.

France

In France the safety rules, the Consignation d'appareil électrique, are defined in the UTE C18-510 standard. The five rules laid down there are:

1. Unlock ( Séparer )
2. Secure against being switched on again ( Condamner )
3. Define and secure the work zone ( identifier )
4. Voltage-free ( Vérification d'absence de tension (VAT) )
5. Earth and short-circuit ( Mettre à la terre et en court-circuit )

Austria

In Austria, the safety rules in the "Ordinance on the Protection of Employees from Dangers from Electric Current" (Electrical Protection Ordinance 2012 - ESV 2012) are defined in Section 12 as follows:

1. Unlock,
2. secure against being switched on again,
3. Determine the absence of voltage,
4. Grounding and short-circuiting:

   a) in any case in high-voltage systems,

   b) in extra-low voltage or low-voltage systems, if there is a risk that the system will be energized,

5. Cover or block off neighboring, live parts.

Switzerland

Five safety rules

In Switzerland, the five safety rules for work in the high-voltage sector are defined at ordinance level in Art. 72 of the Ordinance on Electrical Power Systems (SR 734.2). They are as follows:

«Before starting work on high-voltage systems, the workplace must be prepared in accordance with the following five safety rules:

a) isolate and disconnect on all sides;

b) secure against being switched on again;

c) check for no voltage;

d) earth and short-circuit;

e) protect against neighboring live parts. »

For the low-voltage sector, work safety is defined in Art. 22 of the Ordinance on Low-Voltage Electrical Installations (SR 734.27).

«Before starting work is

a) disconnect;

b) secure against reclosing;

c) to check that there is no voltage;

d) to be earthed and short-circuited if there is a risk of voltage transmission or feedback;

e) to cover against neighboring parts that remain live. "

In the low-voltage area, earthing and short-circuiting may be dispensed with, provided there is no risk of voltage transmission or feedback. (see also SR 734.2, Art. 72, Para. 4)

literature

• Ernst Hörnemann, Heinrich Hübscher: Electrical engineering specialist training in industrial electronics. 1st edition. Westermann Schulbuchverlag, Braunschweig 1998, ISBN 3-14-221730-4 .
• Günter Springer: Expertise in electrical engineering. 18th edition. Verlag - Europa - Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9 .

Legal bases and standards

Germany

• DIN VDE 0105-100 VDE 0105-100: 2015-10; Operation of electrical systems - Part 100: General requirements

France

• UTE C18-501; Consignation d'appareil électrique

Austria

• Ordinance on the protection of employees from the dangers of electrical current (Electrical Protection Ordinance 2012 - ESV 2012) § 10

Switzerland

• Ordinance on electrical power systems (SR 734.2), Art. 72
• Ordinance on electrical low-voltage installations (SR 734.27), Art. 22

Individual evidence

1. ↑ EN 50110-1: 2008-09; Section 6.2 "Working in a voltage-free state"
2. ↑ http://www.elektronik-kompendium.de/sites/grd/1506081.htm voltage tester
3. ^ BGI 519 Safety when working on electrical systems, professional association for precision mechanics and electrical engineering 2002; [1]
4. ↑ DIN VDE 0105-100: 2009-10; Point 6.2 Working in a voltage-free state; Page 25
5. ^ Seibel: Presentation of accident figures and prevention measures. (PDF; 2.5 MB) Slide 10 "Reported electrical accidents". Professional Association of Precision Mechanics and Electrical Engineering, Department of BK investigations and statistics, May 8, 2007, accessed on April 3, 2012 . 
6. ↑ DIN VDE 0105-100: 209-10 Section 6.3
7. ↑ Entire legal regulation for electrical protection regulation. (PDF) 33rd Ordinance. February 6, 2012, accessed October 16, 2012 .