SPE-PRCD

from Wikipedia, the free encyclopedia

A SPE-PRCD (Switched Protective Earth - Portable Residual Current Device = portable residual current protective device with switched protective conductor ) is a special portable protective device with protective conductor detection or protective conductor monitoring . The device is used to protect people from electrical accidents in the low voltage range (130–1000 V). The best-known implementation of a SPE-PRCD from a certain manufacturer is sold under the name “PRCD-S”. A SPE-PRCD must be suitable for commercial use and is used like an extension cable between an electrical consumer - i. d. Usually a power tool - and an outlet installed.

requirements

Before operating the electrical consumer, the SPE-PRCD must first be switched on. The socket used is checked for proper wiring. The SPE-PRCD can only be switched on if it is in a perfect and safe condition. Only then can the electrical consumer be switched on. With this function, the PRCD-S prevents accidents that are caused by faulty electrical installations (e.g. missing protective conductor or interchanging protective conductor and external conductor ). Faults of this type can usually only be identified by a closer examination of the electrical installation and are therefore particularly dangerous.

The currently used and available SPE-PRCD only fulfills this protective function if it is switched on with direct skin contact, i.e. without gloves, since it carries out a measurement through the user's body during the switch-on process.

After switching on the electrical consumer, the SPE-PRCD serves as a residual current circuit breaker and protects the user against dangerous currents that can be caused by defective electrical equipment (e.g. voltage on the metal housing of a concrete mixer due to an insulation fault ).

In addition, the SPE-PRCD has a so-called undervoltage release. This prevents electrical consumers (e.g. cut-off machines) from switching on again automatically and unexpectedly after a power failure, as soon as the power is available again.

Individual functions of the SPE-PRCD

1. Line examination

In order to be able to switch on the SPE-PRCD, the socket used must have functional outer conductors and neutral conductors . If one of the lines is not connected to the intended point of the socket, the SPE-PRCD cannot be switched on. Correct function of the residual current device of the SPE-PRCD is impossible without a neutral conductor. Therefore it is absolutely necessary for safe work.

2. Protective conductor detection

When the on-button of the SPE-PRCD is pressed, it checks whether the protective conductor of the corresponding power cable is connected to the intended point of the socket and that it is functioning properly. It can happen that the protective conductor is connected to the wrong terminal or is forgotten when the socket is installed. In some cases, however, the protective conductor is damaged by wear and tear, rough handling or amateur repair work even after the socket has been properly installed. The protective conductor is the most important safety element in an electrical installation. It is used to divert the majority of fault currents (dangerous currents) that occur to earth in order to prevent them from having to flow through a person's body.

3. Protective conductor monitoring

If the SPE-PRCD was connected to a safe socket and could be switched on, it continues to permanently monitor the presence and function of the protective conductor. In addition, it monitors the protective conductor for external voltage. A protective conductor can, for. B. when a third-party line is damaged, voltage is applied. The current flows through the protective conductor to earth. In this case the PRCD-S does not switch off the power supply in order to prevent further damage. Although the PRCD-S normally interrupts all 3 poles of a line in the event of a fault in order to ensure the highest possible safety level, in this case it maintains the connection to the protective conductor so that the current arriving via the external line can safely flow away via the protective conductor. The upstream safety devices, the line circuit breaker and / or the residual current circuit breaker, react and interrupt the damaged circuit as intended.

4. Undervoltage release

The power that returns after a power failure can be dangerous under certain circumstances. If the power suddenly fails, the power tools that have failed are often carelessly put aside in order to find the cause of the power failure. In doing so, people often forget to switch off the tools, since they no longer work without electricity. If the power supply is then restored, the power tools that have not been switched off are automatically switched on again. This can lead to serious injuries, especially with dangerous tools such as saws, cut-off machines or drills, as users often do not expect the power to return suddenly. The PRCD-S must be consciously switched on again after a power failure in order to prevent this type of accident.

5. Residual current device

One of the essential functions of the SPE-PRCD is the residual current device. After the SPE-PRCD has been switched on, this device functions as a residual current circuit breaker with a nominal residual current of 30 mA. Based on the principle of the summation current transformer , the SPE-PRCD compares the current conducted to the consumer via the external conductor with the current returned from the consumer via the neutral conductor. If the SPE-PRCD detects a difference that is greater than 15 mA - 30 mA (0.5-1x I Delta N), it switches off the circuit within 0.2 s, as the current obviously does not affect the circuit leaves the intended path. This can mean that the current, e.g. B. due to an insulation fault, flows through an electrical consumer through the body of a person to earth. The speed of the switch-off process and the switch-off at ≤ 30 mA ensure that the current flowing through the body is very unlikely to cause any electrical damage to health. However, it should be considered that there is a flow through the body, which is limited in time by the residual current device, but not in intensity.

Application area

A SPE-PRCD is used for commercial use to ensure occupational health and safety when handling electrical energy and is designed to be robust. Craftsmen in particular are often confronted with the problem that they have to connect their power tools to sockets whose functional reliability they cannot check. The pace of work, specialist knowledge and frequently changing locations do not allow checking of every single socket.

The high number and severity of accidents that have occurred in the past due to faulty electrical installations have the professional associations prompted in the BG information DGUV information (until May 2014 BGI 608) on technical solutions, including the use of 203 to 006 of RCDs for the safe operation of electrical equipment during construction and assembly work. In particular, the use of a portable protective device in accordance with DIN VDE 0661 with additional monitoring of voltage on the protective conductor, breakage of the protective conductor and maintenance of the protective conductor function in the event of external voltage is required. The technical solutions contained in the BG information do not exclude other, at least as safe solutions.

In the now repealed TRBS 2131 ( Technical Rules for Operational Safety ), the SPE-PRCD was also described as a portable protective device for the feed point during construction work on a small scale. (DGUV regulation 3 and VDE 0105-100 also apply)

The SPE-PRCD meets the requirements of the Federal Ministry of Labor and Social Affairs and the employers' liability insurance association for a portable protective device. With its help, workers in the commercial sector can continue to use existing sockets safely.

The use of an SPE-PRCD is also mandatory for fire brigades if a device is to be connected to an existing house installation instead of the power generator .

Other possible protective devices

  • Site power distributor according to DIN VDE 0660-501
  • Site power distributor according to VDE 0612, if the plugs and sockets are protected up to AC 230 V / 16 A and up to AC 400 V / 32 A by a residual current device (RCD) with IΔN ≤ 30 mA
  • Transformers with separate windings ( isolating transformer )
  • Replacement power generator according to DIN VDE 0100-551. See also BGI 867.
  • Special, tested branches of stationary electrical systems assigned to the construction site facility, including associated plug-in devices that are permanently marked as construction site feed points.
  • Miniature power distributors
  • Protection distributor

Regulations, laws and standards

literature

  • Altmann, S .; Jühling, J .; Kieback, D .; Zürneck, H., Electrical Accidents in Germany. Accidents caused by electricity in the workplace and in the private sector, 2nd edition. Bremerhaven: Wirtschaftsverlag NW Verlag für neue Wissenschaft GmbH 2006, BAuA research report 941, ISBN 3-86509-541-0 , pages 152.
  • KAN-Brief 2001-2: Portable residual current protective devices , published by the "Commission for Occupational Safety and Health (KAN)", accessed on September 24, 2018, PDF

Web links

Individual evidence

  1. ↑ Important safety information for the use of portable personal protection devices with extended protection functions (PRCD-S). (PDF; 367 kB) DGUV, accessed on September 24, 2018 .

See also