Check (VDE)

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The testing of electrical installations describes making sure the function and safety with appropriate test and measurement procedures after erection, you extend or modify such facilities. Central regulations for the German and z. Some European scope can be found in the DIN VDE standards, especially in DIN VDE 0100-600 and DIN VDE 0105-100. These measures may only be carried out by a person trained as a specialist in electrical engineering with the help of suitable and approved devices.

Visit

Visiting a system is described in the VDE as "the most important point". In this test section, by looking and touching, shaking, pulling and the like, all cables and electrical components are checked for their firm hold (if necessary), correct connection, correct dimensioning (e.g. of cables and fuses ), fixed connection and all component-related features checked. The test of the safety devices is also part of this point. Above all, the test of residual current circuit breakers , protective measures (such as obstacles, housings) and the correct connection of the protective conductor are essential sub-points that everyone should pay attention to when viewing. In the event of negligence or carelessness, there is a risk to life for everyone who comes into contact with the system and has to work with it. Sub-items are:

  • General inspection
  • Check the protective measures against direct contact
  • Check the protective measures with protective conductor
  • Checking the protective measures without a protective conductor

General inspection

The "general inspection" in the sense of VDE 0100 is understood as a rough inspection by a qualified electrician. The general inspection of an electrical system is, strictly speaking, an initial visual inspection by the builder. The following four points are summarized under the general inspection of an electrical system (or these four points must be checked):

  • The equipment must withstand the external influences at the place of use.
This point ensures that the system has also been equipped against local influences. For example, if there is another electrical system in the immediate vicinity of the system that causes violent vibrations, the new system to be tested must be attached or anchored in such a way that there is no danger.
  • The overcurrent protection devices are to be dimensioned according to the line cross-sections.
At this point it is checked whether the selected overcurrent protection devices ( LS switches or fuses ) are adapted to the weakest link in the circuit.
As an an example:
1.5² = 18 A
Socket = 16 A
Switch = 10 A
So you would choose a 10 A fuse here.
  • The individual circuits must be labeled.
At this point, you must check whether all circuits on the system are marked. E.g. that main circuits, control circuits and circuits with low voltage are clearly marked (with different colored lines).
  • Circuit diagrams - if necessary - must be available.
It must be checked whether all circuit diagram documents for the system are located on the machine itself or separately; And whether these correspond to the system.

Protective measures against direct contact (basic protection)

The basic rule of protection against electric shock is that dangerous, active parts must not be touchable and that touchable, conductive parts must not become dangerous, live parts under normal or individual fault conditions.

The precautions for basic protection under normal conditions include basic insulation of active parts, which can only be removed by destroying them, as well as covers and casings that must meet certain requirements for the degree of protection and can only be removed with a tool. To ensure safe operation, all covers and casings must be completely installed in accordance with the device description and undamaged.

For special conditions, exclusively for use in systems that are only operated and monitored by qualified electricians or electrotechnically trained persons (e.g. in locked electrical operating areas), obstacles (barriers) and arrangement outside the reach of the hand are permitted as measures.

Protective measures with protective conductor

  • Protective conductors, ground conductors and protective equipotential bonding conductors must be properly laid and connected in a reliable electrical manner. Connection and connection points must be protected against loosening and corrosion and must be accessible for inspection. The conductors must have the required cross-section. The protective conductor establishes an electrical connection between accessible metallic housings (body of electrical equipment) and the main earthing rail either by means of a permanent connection or by means of the protective conductor contacts in sockets. The earthing conductor connects the main earthing rail with an earth electrode (usually foundation earth or other earth electrodes such as ring earth electrodes). The protective equipotential bonding conductor is used to ensure equipotential bonding and connects external conductive parts (water pipes, heating, air conditioning, railings, etc.). with the main earthing rail.
  • Protective conductor and protective conductor connections must be marked in accordance with the standard. The protective conductor, also called PE conductor (protective earth), is a conductor for the purpose of safety, for example to protect against electric shock in the event of a fault. Connection points for the protective conductor are marked with the protective conductor symbol (earth symbol in a circle).
  • The protective conductor and neutral conductor may no longer be connected to each other (and of course not interchanged) after the PEN has been disconnected for the first time in a system. The neutral conductor is an active conductor and is able to contribute to energy distribution. Active conductors must be protected against contact.
  • Residual current protective devices (RCDs, Fi) or insulation monitors in IT systems and surge arresters must be designed in accordance with current standards, the application and for the respective network system (TN-TT-IT-).

Protective measures without protective conductor

The power sources with protection by low voltage SELV or PELV must be equipped with a safety transformer or a comparable power source with galvanic isolation (battery, generator, etc.) to meet the requirements for safe isolation.

Plugs and sockets for SELV or PELV systems must not fit into sockets or plugs for other voltage systems and plugs and sockets in SELV systems must not have a protective conductor contact.

The protective measure of protective separation with an ungrounded power source (SELV) allows only one consumable per power source (secondary winding of an isolating transformer or motor generator).

For special systems that are only operated and monitored by qualified electricians and electrotechnically trained persons, special regulations apply to "non-conductive environment", "protection through floating local equipotential bonding" and "protective separation with more than one consumable".

Note: The functional extra-low voltage (FELV) typically has no safe separation and requires additional measures for basic protection and for fault protection, so it cannot be included in the protective measure: "Protection by extra-low voltage using SELV or PELV".

measure up

Protective conductor measurement

According to DIN VDE 0100 Part 600, a protective conductor measurement must be carried out after installation, expansion or repair of electrical systems before commissioning. This takes place in the voltage-free state. This measurement must be recorded.

This measurement is not used to ensure that the safety devices are triggered. During this measurement, the continuity of the protective and equipotential bonding conductors is checked. The triggering of the safety devices (e.g. line circuit breaker , residual current circuit breaker (RCD), insulation monitor ) is carried out with the loop impedance measurement, since the resistances up to the power source (e.g. transformer ) must also be measured and evaluated here.

A simple multimeter is not sufficient for this measurement, as the measuring current must be at least 200 mA at 4 - 24 V AC / DC. The resistance of all conductive parts that can be touched over a large area or that can be grasped by hand (e.g. motor housing or handles) and a potential equalization or protective conductor connection point (e.g. plug) is measured. The measuring current can also be 10 A with appropriate measuring devices, which has the advantage that broken cables and oxide layers or similar (rust, (lime) deposits) can be detected. With the latter, the contact can be 'burned free' due to the high measuring current - sparks can occur. When measuring with higher currents, it must be ensured that the protective conductor can withstand these currents without damage. With the 10 A measurement, the protective conductor cross-section should not be less than 1 mm². It should also be noted that the high output (up to 240 W → 24 V * 10 A) in the system can cause damage or increase existing ones. When measuring with DC, the polarity must be changed (exchange measuring tips). If different values ​​arise, this indicates an error (similar to a diode ).

The resistance must be low, for this there are different maximum (empirical) values ​​e.g. B. "usually about 1 ohm". Clear fixed upper limits are not specified in DIN VDE 0100-600 or ...- 701-702. The following values ​​can be found in DIN VDE 0100 part 701-702 for systems / devices with a rated current of up to 16 A: Up to 5 m cable length 0.3 Ω - every additional 7.5 m + 0.1 Ω - however, up to a maximum of 1 Ω. For all other systems, the calculated value (cable length, cross section, electrical conductivity ← depending on temperature) is the limit value. Plus every 0.0001 Ω (0.1 mΩ) per connection point (contact resistance).

Conductor cross-section

in mm²

Conductor resistance

in mΩ / m (20 ° C / 30 ° C)

1.5 12.2 / 12.58
2.5 7.56 / 7.57
4th 4.7 / 4.74
6th 3.11 / 3.15
10 1.84 / 1.88
16 1.16 / 1.19

IEC 60228 / DIN EN 60228 (VDE 0295)

The worst measured (highest) and the calculated value are documented.

Measurement of insulation resistance in electrical systems

Most faults in electrical systems are caused by aging, thermal, chemical and mechanical stress. Since such errors can cause a reduction in the insulation, the insulation between the active conductors and the protective conductor is measured ( insulation measurement ). In hazardous areas, all are measured against all conductors. For this measurement, a voltage is required which is higher than the operating voltage. Devices that can be damaged by the measuring voltage and devices that could falsify the measurement (e.g. transformers) must be disconnected from the circuit to be measured. Furthermore, all fuses and switches should be switched on so that the entire system can be measured as far as possible. However, the electrical system must be voltage-free. Direct current is used for measurements, since alternating currents could generate capacitive or inductive reactance and would falsify the measurement result.

Measure the loop impedance

The loop impedance is the sum of all resistances in the distribution network and the lines in the final circuit. The resistance must be so low that in the event of a short circuit, enough current flows to trigger the fuses. In practice, the loop impedance is a maximum of 1 Ω. The loop impedance may also be> 1 Ω as long as the short-circuit current is still large enough for the protective device to trip. It is usually determined with multi-function measuring devices (e.g. Fluke ) that display the short-circuit current and the loop impedance directly.

Measuring the operating voltages

To ensure safe operation, all the voltages required must be measured after the system has been switched on. In the household networks common in Germany, for example: outer conductor to outer conductor 400 V, outer conductor to neutral conductor 230 V, outer conductor to protective conductor 230 V, neutral conductor to protective conductor 0 V. This measurement can be carried out with a two-pole voltage tester (Duspol) or a multimeter.

Try it out

Testing according to DIN VDE 0100-600 proves the effectiveness of the protection and signaling devices according to DIN VDE 0100-410. There must be no danger to people, farm animals or property. Tests must be carried out if a function cannot be verified by inspection, which is generally the case with residual current protective devices (RCDs), insulation monitoring devices and emergency stop switching devices.

This happens e.g. B. by:

  • Actuation of the test buttons on RCDs, FI protective devices and insulation monitoring devices
  • Proof of the function of EMERGENCY STOP devices
  • Function control of reporting devices

Pressing the test button on residual current devices (RCDs) only tests the function of the device itself. The function of the protective measure as a whole and its effectiveness cannot be proven here; measurements are mandatory for this.

literature

  • M. Kampler, H. Nienhaus, D. Vogt: Testing before commissioning of low-voltage systems (=  VDE series of publications . Volume 63 ). 3. Edition. VDE Verlag, Berlin / Offenbach 2008, ISBN 978-3-8007-3112-1 , p. 252 .
  • Electrical engineering expertise. 25th edition. Europa Verlag, Haan-Gruiten 2006, ISBN 3-8085-3157-6 .
  • Electrical engineering: power engineering. 1st edition. Klett Verlag, 1994, ISBN 3-12-870700-6 .
  • Qualifications in electrical engineering: industrial engineering. Education publisher E1NS, 2005.
  • Basic and specialist level electrical engineering: energy technology. Kieser Verlag, 1999, ISBN 3-8242-4290-7 .

Norms

  • DIN VDE 0100-600: 2008-06 Installation of low-voltage systems Part 6: Tests
  • DIN VDE 0100-610: 2004-04 Construction of low-voltage systems Part 6-61: Tests - initial tests " withdrawn standard "
    • End of the transition period: September 1, 2009, replaced by DIN VDE 0100-600 VDE 0100-600
  • DIN VDE 0105-100: 2009-10 Operation of electrical systems Part 100: General specifications

See also

Web links

Individual evidence

  1. ↑ DIN EN 61140: 2007 (VDE 0140-1: 2007-3 section 4)
  2. ↑ DIN VDE 0100-410: 2007-06 Appendix A
  3. ↑ DIN VDE 0100-410: 2007-06 Appendix B
  4. ↑ DIN VDE 0100-540: 2012-06 Sections 542, 543, 544 and Appendix B
  5. ↑ Symbol 02-15-03 according to DIN EN 60617-2: 1997-08 Graphic symbols for circuit diagrams - Part 2: Symbol elements, labels and other circuit symbols for general applications (page 33)
  6. ↑ DIN VDE 0100-540: 2012-06 section 543.4.3
  7. ↑ DIN VDE 0100-540: 2012-06 section 543.3.3
  8. ↑ DIN EN 61558-2-6; VDE 0570-2-6: 2010-04 Safety of transformers, chokes, power supply units and the like for supply voltages up to 1100 V - Part 2-6: Special requirements and tests on safety transformers and power supply units that contain safety transformers.
  9. ↑ DIN VDE 0100-410: 2007-06 section 414.3
  10. ↑ DIN VDE 0100-410: 2007-06 section 414.4.3
  11. ↑ DIN VDE 0100-410: 2007-06 section 414.1.2
  12. ↑ DIN VDE 0100-410: 2007-06 Appendix C
  13. ↑ DIN VDE 0100-410: 2007-06 section 411.7
  14. ↑ Electrical engineering, Europa Verlag, Haan-Gruiten, 2006, 25th edition, p. 345.
  15. ↑ a b HUSS-MEDIEN electrical practitioner: test according to DIN VDE 0100-600
  16. ↑ Electrical engineering Hillebrand training and further education: Commissioning of electrical systems according to DIN VDE 0100 - 600 section 2.2.2.
  17. ↑ LAPPKABEL table T11