Kurapin V.N., Tsyganov V.V. Application of RCDs in electrical installations with the TN system grounding type
The use of residual current devices that react to differential current (RCD) in electrical installations with the type of grounding of the TN system. Teaching-methodical manual / Comp. V.N. Kurapin, V.V. Tsyganov; Volgograd. State. S.-. Acad. - Volgograd, 2006 - 83s.
The manual is intended for students studying in the reduced terms of training on specialty 110302 "Electrification and automation of agriculture" and is recommended for use in course and diploma design.
The manual "Application of residual current protective devices that react to differential current (RCD) in electrical installations with the TN system grounding type" provides information on the device and the operation principle of RCD, technical requirements for RCDs, as well as provisions of regulatory documents governing the use of RCDs.
In the manual, the procedure for designing electrical installations is given and schemes of electrical installations using RCD are considered. Technical data of some types of RCD manufactured by the industry are given.
Introduction.
From the first half of the 1990s to the present, Russia is working to unify the GOST and standards in the field of electrical safety and the relevant IEC standards.
During this time, a set of standards GOST R. 50571 was adopted, changes were made to the PUE, VSN, SNIP and other normative documents. Since 1.01.2002 GOST R. IEC 61140-2000 "Protection from electric shock" has come into effect.
Based on this GOST and GOST R. 50571, the seventh edition of the PUE adopted the concept of electrical safety, based on the implementation of the basic rule of electrical safety - "Dangerous current-carrying parts should not be accessible, and accessible conductive parts should not be dangerous under normal conditions and in the presence of a malfunction."
This rule is sometimes referred to as the "Basic rule for the installation of electrical installations", because in accordance with the above regulatory documents, when designing electrical installations for residential, public and industrial buildings, first of all, the issues of ensuring the safety of people and animals should be resolved, and only then the issues of normal functioning of electrical installations.
In the GOST and PUE all contacts with the conductive parts of the electrical installations of the building, dangerous for humans and animals, are reduced to two types of touches - direct and indirect touch. Accordingly, all measures of protection against electric shock are classified into protection against direct contact and measures of protection against indirect contact. According to the PUE, the following protection measures should be applied to protect against electric shock in the normal mode (direct contact):
- the main insulation of current-carrying parts;
- fencing and shell;
- installation of barriers;
- placement out of reach;
- application of ultra-low (low voltage).
To protect against electric shock in case of insulation damage (indirect touch), the PUE provides the following protection measures, the main ones of which are:
- protective earthing;
- automatic power off;
- Equalization of potentials;
In the protection system formed by the standards are also "automatic switches controlled by a differential current." In the national regulatory documentation, the equivalent term "protective cut-out device" (RCD) is widely used.
Thus, the RCD is a high-speed circuit breaker that reacts to the leakage current in conductors that conduct electricity to the protected electrical installation and is intended for:
- protection of people and animals from electric shock with accidental, unintentional contact with current-carrying parts of electrical equipment (direct contact);
- protection of people and animals from electric shock with accidental, unintentional contact to open conductive parts of the electrical installation, where dangerous voltage appears when the insulation is damaged (indirect contact);
- prevention of fires and fires, which occur as a result of leakage currents flowing and developing short-circuits to the body and ground. The principle of limiting the duration of the current flowing through the human body when it touches the electric circuit is the basis of the action of the protective shutdown devices.
The use of an RCD can not be the only protection measure and does not exclude the need for protective measures against direct and indirect contact mentioned above. The residual current devices can only be used as an additional measure of protection from electric shock when touched directly.
As a basic measure of protection against electric shock, the RCD can be used for indirect contact, in case of inefficiency of automatic power cutoff by overcurrent protection.
Contents of the manual:
Area of application of residual current devices
The device and the principle of action of U30
Classification of RCDs
Technical parameters of residual current devices
RCD documentation
The basic stages of electrical safety in electrical installations of buildings using RCDs
Designing of electrical installations using RCDs
Requirements for RCD installation
Testing of RCDs with acceptance tests
RCD operational control
List of used normative documents and literature
Appendix 1. Terms and definitions
Appendix 2. Some general parameters of RCDs and their application in accordance with GOST
Appendix 3. Technical characteristics of some domestic RCDs
The book "Application of RCD in electrical installations with the type of grounding of the TN system" ( DjVu , 1 mb )
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