Residual current devices. Purpose, device, scope. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Residual current devices. Purpose, device, scope of RCD. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Current Devices

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The purpose of the RCD

At its core, the RCD is a high-speed protective switch that automatically disconnects the controlled electrical installation from the network in the event of a single-phase or three-phase asymmetrical earth leakage.

Leakage can be caused by a person touching current-carrying parts directly or through damaged insulation, contact of current-carrying elements with each other, if the insulating layer is broken, for example, due to fire.

Of all the known electrical protective equipment, the RCD is the only device that protects a person from electric shock in the event of direct contact with live parts.

RCD device

The main blocks of the RCD are shown in the block diagram (Fig. 14.14).

Purpose, device, scope of RCD
Rice. 14.14. The main blocks of the RCD: 1 - differential transformer that; 2 - threshold element; 3 - actuator 4 - testing circuit; 5 - power contacts

The functional most important unit of the RCD is a differential current transformer 1. In the vast majority of RCDs currently produced and operated around the world, it is the current transformer that is used as a differential current sensor. The trigger element (threshold element) 2 is made, as a rule, on sensitive magnetoelectric relays of direct action or electronic components.

The actuator 3 includes a power contact group with a drive mechanism. In normal mode, in the absence of differential current - leakage current, in the power circuit, the operating current of the load flows through the conductors passing through the window of the magnetic circuit of the current transformer 1.

Scope of RCD

RCDs are used to complete input distribution devices, switchboards, group shields (apartment and floor), as well as to protect individual consumers of electricity.

The scope of the RCD is quite wide - these are electrical installations:

public buildings;
residential buildings, individual and multi-apartment;
administrative buildings;
industrial premises, workshops;
industrial enterprises.

The exception is electrical installations that do not allow interruptions in power supply for technological reasons. In such installations, other electrical protective measures must be applied to protect people from electric shock - insulation control, isolation transformers, etc.

Author: Koryakin-Chernyak S.L.

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