RCCB – Residual Current Operated Circuit-Breaker Without Integral Overcurrent Protection

What Is an RCCB?

The term ‘residual current operated circuit-breaker without integral overcurrent protection, RCCB (abbreviation)’ is officially defined within the IEC 61008-1-2013 as:

residual current operated circuit-breaker not designed to perform the functions of protection against overloads and/or short-circuits.

IEC 61008-1-2013

Currently, there continues to be confusion over terminology, as many incompetent persons often use the general term “RCD” instead of the correct and specific term “RCCB”.

A residual current operated circuit-breaker without integral overcurrent protection is a type of residual current device which is not equipped with integral overcurrent protection. The RCCB must therefore be protected against both overloads and short-circuits by overcurrent protection devices, which are circuit breakers and fuses.

These devices are intended to protect persons against indirect contact, the exposed conductive parts of the installation being connected to an appropriate earth electrode. They may be used to provide protection against fire hazards due to a persistent earth fault current, without the operation of the overcurrent protective device.

RCCBs having a rated residual operating current not exceeding 30 mA are also used as a means for additional protection in case of failure of the protective means against electric shock.

The RCCBs under consideration are intended for use by ordinary persons and do not require maintenance. They can be used as disconnectors.

Benefits of RCCB

The main benefit of RCCB is that it can detect and interrupt current leakage and thus provide a higher level of protection for people and appliances.

Other benefits include:

  • Improved safety: RCCB can detect and interrupt dangerous current leakage caused by insulation faults, ground faults, and other electrical hazards. This helps to protect people and appliances from electric shock and electrocution.
  • Early detection of problems: RCCB can detect current leakage and other electrical problems before they cause serious damage or injury. This allows for early intervention and repairs, which can save time, money, and resources.
  • Increased energy efficiency: RCCB can help to reduce energy consumption by detecting and interrupting current leakage, which can lead to improved energy efficiency and lower energy costs.
  • Enhanced reliability: RCCB is designed to be reliable and durable, and can withstand the rigors of daily use in various environments.
  • Easy to install and maintain: RCCB is easy to install and maintain, and can be integrated into existing electrical systems without the need for extensive modifications or upgrades.

Overall, RCCB provides a high level of protection against electric shock, electrocution and other electrical hazards, while also being energy efficient and easy to install and maintain. It’s a must have in any building for safety purpose.

How Does the RCCB Work?

For detailed information on the principle of working of any residual current device (including the RCCB), read the article: RCDs Explained

Requirements

International requirements for household RCCBs are described in IEC 61008-1. This International Standard applies to residual current operated circuit-breakers functionally independent of, or functionally dependent on, line voltage, for household and similar uses, not incorporating overcurrent protection (hereafter referred to as RCCBs), for rated voltages not exceeding 440 V a.c. with rated frequencies of 50 Hz, 60 Hz or 50/60 Hz and rated currents not exceeding 125 A, intended principally for protection against shock hazard.

IEC 61008-1 defines basic terms and their definitions; classifies RCCBs; discusses characteristics of RCCBs, their standard and preferred values; and lists information that must be marked on RCCBs and contained in manufacturer’s documentation; requirements for RCCBs design, performance, and environmental conditions; conditions to be met by RCCBs during normal conditions, overloads, and short-circuits; the scope and methods of testing RCCBs; and other requirements and recommendations.

This standard applies to devices performing simultaneously the functions of detection of the residual current, of comparison of the value of this current with the residual operating value and of opening of the protected circuit when the residual current exceeds this value.

For RCCBs incorporated in, or intended only for association with socket-outlets, the requirements of this standard may be used, as far as applicable, in conjunction with the requirements of IEC 60884-1 or the national requirements of the country where the product is placed on the market.

RCCBs including batteries are not covered by this standard.

Note 1. In the UK, the plug part of an RCCB shall comply with BS 1363-1 and the socket-outlet part(s) of an RCCB should comply with BS 1363-2. In the UK, the plug part and the socket-outlet part(s) of an RCCB need not comply with any IEC 60884-1 requirements.

Note 2. In DK, plugs and socket-outlets shall be in accordance with the requirements of the heavy current regulations, section 107.

Installation and application rules of RCCBs are given in the IEC 60364 series.

Characteristics of RCCBs

The characteristics of an RCCB shall be stated in the following terms:

  • type of installation;
  • number of poles and current paths;
  • rated current In;
  • rated residual operating current IΔn;
  • rated residual non-operating current IΔno;
  • rated voltage Un;
  • rated frequency;
  • rated making and breaking capacity Im;
  • rated residual making and breaking capacity IΔm;
  • time-delay, if applicable;
  • operating characteristics in case of residual currents with DC components;
  • degree of protection (see IEC 60529);
  • rated conditional short-circuit current Inc;
  • rated conditional residual short-circuit current IΔc;
  • method of mounting;
  • method of connection.

For RCCBs functionally dependent on line voltage:

  • behaviour of the RCCB in case of failure of line voltage.

Type of Installation

According to the type of installation:

  • RCCB for fixed installation and fixed wiring;
  • RCCB for mobile installation and corded connection (of the device itself to the supply).

Number of Poles and Current Paths

According to the number of poles and current paths:

  • single-pole RCCB with two current paths;
  • two-pole RCCB;
  • three-pole RCCB;
  • three-pole RCCB with four current paths;
  • four-pole RCCB.

Two-pole and four-pole RCCBs are the most widely used in the electrical installations of buildings, used respectively in single-phase two-wire and three-phase four-wire electrical circuits. Three-pole RCCBs, which are used in three-phase three-wire circuits, are manufactured in small quantities. However, they have a much smaller field of application.

RCCBs
Figure 1 – Residual current operated circuit-breakers without integral overcurrent protection (RCCB): 1 – two-pole, 2 – four-pole

Figure 2 shows actual models of a 2-pole (left) and 4-pole (right) RCCB:

RCCB two-pole and four-pole
Figure 2 – RCCB: two-pole (left) and four-pole (right)

Method of Mounting

According to the method of mounting:

  • surface-type RCCB;
  • flush-type RCCB;
  • panel board type RCCB, also referred to as distribution board type.

NOTE – These types may be intended to be mounted on rails.

Method of Connection

According to the method of connection:

  • RCCBs, the electrical connections of which are not associated with the mechanical mounting;
  • RCCBs, the electrical connections of which are associated with the mechanical mounting.

NOTE – Examples of this type are:

  • plug-in type;
  • bolt-on type;
  • screw-in type.

Some RCCBs may be of the plug-in type or bolt-on type on the line side only, the load terminals being usually suitable for wiring connection.

Rated voltage (Un)

The rated operational voltage (hereafter referred to as “rated voltage”) of an RCCB is the value of voltage, assigned by the manufacturer, to which its performance is referred. The same RCCB may be assigned a number of rated voltages.

The rated voltage Un of two-pole RCCBs is usually 230 V, three-pole and four-pole RCCBs are 400 V. Special RCCBs are also available with higher rated voltages, e.g. 500 V.

Rated Current (In)

Rated current In is the value of current, assigned to the RCCB by the manufacturer, which the RCCB can carry in uninterrupted duty.

Preferred values of rated current are 10 – 13 – 16 – 20 – 25 – 32 – 40 – 63 – 80 – 100 – 125 A.

RCCBs with a rated current In of 25 A and 40 A are the most common in the electrical installations of buildings. RCCBs with a rated current of 16 A are used less frequently. They are usually used for protection of one current-using equipment. RCCBs with 63, 80, 100, and 125 A rated currents also have a smaller application area. These devices are installed on the inputs of low-voltage switchgears or are used to protect electrical circuits to which powerful current-using equipment are connected.

Rated Residual Operating Current (IΔn)

Rated residual operating current IΔn is the value of residual operating current, assigned to the RCCB by the manufacturer, at which the RCCB shall operate under specified conditions.

For an RCCB having multiple settings of residual operating current, the highest setting is used to designate it. RCCBs with continuously adjustable settings are not allowed.

Standard values of rated residual operating current are 0,006 – 0,01 – 0,03 – 0,1 – 0,3 – 0,5 A.

Note – In Korea and Japan, the values of 0,015 A, 0,2 A and 1 A are also considered as standard values.

General purpose RCCBs with a rated residual operating current IΔn up to and including 0.03 A are normally used in the electrical installations of buildings to provide additional protection against electric shock.

General purpose RCCBs with IΔn equal to 0.10; 0.30 and 0.50 A are typically used in the electrical installations of buildings to provide protection in case of a fault as part of the automatic disconnection of the power supply as well as in those electrical circuits that have high leakage currents.

RCCBs of type S have a rated residual operating current of 0.10; 0.30 or 0.50 A. They are usually used to protect the whole or parts of the electrical installation of a building. Some companies make special RCCBs of type S with an IΔn of 1.00 A.

Rated Residual Non-Operating Current (IΔno)

Rated residual non-operating current (IΔno) is the value of residual non-operating current, assigned to the RCCB by the manufacturer, at which the RCCB does not operate under specified conditions.

The standard value of residual non-operating current is 0,5 IΔn.

NOTE – For residual pulsating direct currents, residual non-operating currents depend on the current delay angle α.

Rated Frequency

The rated frequency of an RCCB is the power frequency for which the RCCB is designed and to which the values of the other characteristics correspond.

A vast number of RCCBs are designed for use in 50 Hz and 60 Hz AC electrical circuits. Some companies make special RCCBs designed for use at higher frequencies, such as 400 Hz.

NOTE – The same RCCB may be assigned a number of rated frequencies.

Rated Making and Breaking Capacity (Im)

Rated making and breaking capacity (Im) is the r.m.s. value of the AC component of prospective current, assigned by the manufacturer, which an RCCB can make, carry and break under specified conditions.

The minimum value of the rated making and breaking capacity Im is 10 In or 500 A, whichever is greater.

The rated making and breaking capacity (Im) of manufactured RCCBs are usually 500-1500 A.

Rated Residual Making and Breaking Capacity (IΔm)

Rated residual making and breaking capacity (IΔm) is the r.m.s. value of the AC component of residual prospective current, assigned by the manufacturer, which an RCCB can make, carry and break under specified conditions.

The minimum value of the rated residual making and breaking capacity IΔm is 10 In or 500 A, whichever is greater.

The rated residual making and breaking capacity IΔm of manufactured RCCBs are usually 500-1500 A.

Time-Delay (RCBO type S)

A time-delay RCCB which complies with the relevant part of Table 1, and Table 2 if applicable.

Limit values of break time and non-actuating time for alternating residual
currents (r.m.s. values) for type AC and A RCCB
Table 1 – Limit values of break time and non-actuating time for alternating residual currents (r.m.s. values) for type AC and A RCCB
Maximum values of break time for half-wave pulsating residual currents (r.m.s. values) for type A RCCB
Table 2 – Maximum values of break time for half-wave pulsating residual currents (r.m.s. values) for type A RCCB

Operating Characteristics in Case of Residual Currents with DC Components

RCCB type AC

RCCB type AC is an RCCB for which tripping is ensured for residual sinusoidal alternating currents, whether suddenly applied or slowly rising.

RCCB type A

RCCB type A is an RCCB for which tripping is ensured for residual sinusoidal alternating currents and residual pulsating direct currents, whether suddenly applied or slowly rising.

RCCBs of the AC type, which trip under sinusoidal AC residual currents, and RCCBs of the A type, which trip under both sinusoidal AC and pulsating DC residual currents, are manufactured in series. Some companies have started to manufacture RCCBs of type F and type B, additional (to IEC 61008-1 and IEC 61009-1) requirements to which are described in IEC 62423. These RCCBs are designed to operate with more complex forms of residual current (type F) and even with constant residual current (type B).

Rated Conditional Short-Circuit Current (Inc)

Rated conditional short-circuit current (Inc) is the r.m.s. value of prospective current, assigned by the manufacturer, which an RCCB, protected by an SCPD, can withstand under specified conditions without undergoing alterations impairing its functions.

Up to and including 10 000 A the values of the rated conditional short-circuit current Inc are standard and are 3 000 – 4 500 – 6 000 – 10 000 A.

NOTE – In KR, the values of 1 000 A, 1 500 A, 2 000 A, 2 500 A, 7 500 A, 9 000 A are also considered as standard values.

For values above 10 000 A up to and including 25 000 A a preferred value is 20 000 A. Values above 25 000 A are not considered in IEC 61008-1-2013.

The rated conditional short-circuit current (Inc) of series-produced RCCBs is usually 6000 or 10000 A.

Rated Conditional Residual Short-Circuit Current IΔc

Rated conditional residual short-circuit current IΔc is the value of the residual prospective current, assigned by the manufacturer, which an RCCB, protected by an SCPD, can withstand under specified conditions without undergoing alterations impairing its functions.

Up to and including 10 000 A the values of the rated conditional residual short-circuit current IΔc are standard and are 3 000 – 4 500 – 6 000 – 10 000 A.

The values of 500 A, 1 000 A and 1 500 A are also standard for RCCBs incorporated in or intended for association with socket-outlets.

For values above 10 000 A up to and including 25 000 A a preferred value is 20 000 A. Values above 25 000 A are not considered in IEC 61008-1-2013.

Classification of RCCBs

RCCBs are classified:

1. According to the method of operation.

NOTE – The selection of the various types is made according to the requirements of IEC 60364-5-53.

  • RCCB functionally independent of line voltage;
  • RCCB functionally dependent on line voltage.

Opening automatically in case of failure of the line voltage, without or with delay:

a) Reclosing automatically when the line voltage is restored;
b) Not reclosing automatically when the line voltage is restored.

Not opening automatically in case of failure of the line voltage:

a) Able to trip in case of a hazardous situation (e.g. due to an earth fault) arising on failure of the line voltage (requirements under consideration);
b) Not able to trip in case of a hazardous situation (e.g. due to an earth fault) arising on failure of line voltage.
NOTE – The selection of the RCCBs of b) is subject to the conditions of 531.2.2.2 of IEC 60364-5-53:2001.

2. According to the possibility of adjusting the residual operating current.

  • RCCB with a single value of rated residual operating current;
  • RCCB with multiple settings of residual operating current by fixed steps.

3. According to resistance to unwanted tripping due to voltage surges.

  • RCCBs with normal resistance to unwanted tripping (general type as in Table 1, and Table 2 if applicable);
  • RCCBs with increased resistance to unwanted tripping (S type as in Table 1, and Table 2 if applicable).

RCCBs in general use are sufficiently resistant to electric current surges that may be caused in the electrical installation of a building by lightning or switching overvoltages. They do not trip against current surges with a peak value of 250 A. Some companies make RCCBs of general use, which have a higher resistance to current surges – up to 3000 A. RCCBs of type S are characterized by increased resistance to unwanted tripping from current surges with a peak value of 3000-5000 A (8/20 μs).

4. According to behaviour in presence of DC components.

  • RCCBs of type AC;
  • RCCBs of type A.

5. According to time-delay (in presence of a residual current).

  • RCCB without time-delay: type for general use;
  • RCCB with time-delay: type S for selectivity.

In addition to RCCBs without time delay for general applications and S-type RCCBs with time delay, there are RCCBs which have a short time delay for tripping. The tripping times of these RCCBs exceed 0.01 s, but do not exceed the maximum tripping times for RCDs of general use. RCDs of these types do not trip under residual current pulses of less than 0.01 s, which often occur during switching of electrical equipment due to transients, e.g. in interference suppression capacitors connected between hazardous-live-parts and exposed-conductive-parts of class I electrical equipment connected to protective conductors.

6. According to the protection against external influences.

  • enclosed-type RCCB (not requiring an appropriate enclosure);
  • unenclosed-type RCCB (for use with an appropriate enclosure).

7. According to the type of terminals.

  • RCCBs with screw-type terminals for external copper conductors;
  • RCCBs with screwless type terminals for external copper conductors;
  • RCCBs with flat quick-connect terminals for external copper conductors;
  • RCCBs with screw-type terminals for external aluminium conductors.

8. According to the number of poles and current paths.

  • single-pole RCCB with two current paths;
  • two-pole RCCB;
  • three-pole RCCB;
  • three-pole RCCB with four current paths;
  • four-pole RCCB.

An approximate nomenclature of RCCBs manufactured in series by various companies according to IEC 61008-1 and IEC 61009-1 is given in the table below. Modifications of RCCBs are marked with a “+” sign. A “-” sign means that RCCBs with the specified characteristics are generally not manufactured.

Table 3: Approximate nomenclature of Type AC and Type A RCCBs
In, A IΔn, mА Two-pole RCCBs Four-pole RCCBs
General use Type S General use Type S
16 10 +
30 +
25 10 +
30 + +
100 + + + +
300 + + + +
500 + + + +
40, 63, 80, 100, 125 30 + +
100 + + + +
300 + + + +
500 + + + +

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