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Residual Current Devices (RCDs)
- Types and their applications
by Dahari M. Siran

Residual Current Device
Definition:
A mechanical switching device or association
of devices intended to cause the opening of
the contacts when the residual current attains
a given value under specified conditions.
What is the meaning of residual?
“Protecting people (life) from electrocution and protecting
properties from fire”

06.07.2021 Presentation title 3
LOAD
Residual Current Device
I1
I2
Iresidual
Kirchhoff’s current law
LOAD
I1 + I2 = 0
I1 + I2 + Iresidual = 0
RCD
Measuring vector sum of the currents

Residual Current Devices
RCD
A generic term for all types of Residual Current Devices.
RCD
RCCB (ELCB) PRCD RCBO
(MCB + RCD)
SRCD RCD
Ad-on

RCDs – The standards
IEC 61008
Residual current operated circuit-breakers without integral
overcurrent protection (RCCB) for household and similar uses
IEC 61009
Residual current operated circuit-breakers with integral
overcurrent protection (RCBO) for household and similar uses
62423
Type F and type B residual current operated circuit-breakers with and
without integral overcurrent protection for household and similar uses

RCD – the concept
Primary Winding
Secondary Winding

RCD - Operation of Device
S N
F3
Torroid/CT
Relay
F2
Induced current
LOAD
R

RCCB – the construction
Torroid/CT
Arc splitter
Arc chute
Relay
Contacts Toggle/handle

Question 1
06.07.2021 Presentation title
Please send your answer to:
the LINK or QR code provided in TEAMS
Or WhatsApp Ms. Fatin @ 012-9780028
Name at least 3 important parameters in selecting an RCCB.
1.
2.
3.

RCCB to IEC 61008 & 62423
1. Nominal current In
10-16-25-40-63-80-100A
2. Tripping Current (Sensitivity) In
10-30-100-300-500mA
3. Conditional Breaking Capacity (Inc)
4. Class ‘G’ & ‘S’
5. Types AC, A, B, B+ & F
6. Number of poles (2 or 4)
7. VI or VD
Selection Parameters

RCCB to IEC 61008
1. Trade mark
2. Manufacturer reference number
3. Rated voltage
4. Rated frequency (if other than 50 & 60 Hz)
5. Rated Current: In (A)
6. Rated residual operating current: In
7. Conditional breaking capacity: Inc
8. IP (unless IP20)
9. S = selective (no marking for “G”)
10. T = test button
11. Wiring diagram
12. AC, A, B, B+ or F type
Marking (IEC 61008: Clause 6.0)

Question 2
Based on the RCCB photo,
please provide the details for
the following 4 parameters:
1. In =
2. In =
3. Poles =
4. Class/type =

RCCB – circuit design
40A
40A
63A
40A
40A
40A
25A
WATER HEATER
40A
MCB
RCCB
63A
Selection of nominal current (In)
10-16-25-40-63-80-100A
A B C

63A
MCB
RCCB
63A
40A
63A
40A
40A
40A
40A
40A
40A
25A
25A
WATER HEATER
Selection of nominal current (In)
A B C

Residual Current Devices
Levels of sensitivity & its application
RCD application
10mA Water heater, fountain
Wet area
30mA Personal protection.
Sockets
100mA Limited personal protection
Lighting, A/C, fans
300mA building / properties against
fire

Recommended circuit design
63A 2P
40A 2P
Lightings/Fans/Air-cond Socket outlets

Question 3
63A, 2P, 100mA, Type A,
Inc = ?
MCB
RCCB
63A, 2P, Type C,
Icn = 10kA
Selection of conditional short circuit breaking capacity (Inc)
LOAD
Please select the best Inc
Rating for the RCCB below:
Inc = ?kA

63A, 2P, 100mA, Type A, Inc = 10kA
MCB
RCCB
63A, 2P, Type C, Icn = 10kA
Selection of conditional short circuit breaking capacity (Inc)

Question 4
For discrimination purpose, is this a good design? Y/N
2P RCCB
40A, 100mA
Type G, AC
2P RCCB
40A, 30mA
Type G, AC
LOAD
SUPPLY Please send your answer to:

RCCB – Circuit design
Type-G (general) and Type-S (selective)
2P RCCB
40A, 100mA
Type G, AC
2P RCCB
40A, 30mA
Type G, AC
LOAD
SUPPLY

Standard values of break times (s) and non-
actuating times (s) at a residual current I equal to:
Table 1 IEC 61008-1
> 0.03
G Any value Any value 0.3
In 2 x In 5 x In 500A
Maximum break times
Maximum break times
Minimum non-actuating
times
0.15 0.04 0.04
0.5 0.2 0.15 0.15
0.13 0.06 0.05 0.04
> 25
S
In A
In A
Type
RCCB – Tripping time

100mA ‘G’ type RCD
Gap
‘S’ type - ‘G’ type Discrimination
Windows of operation at 150mA
40ms
t
130ms
300ms
500ms
100ms
200ms
400ms
30mA ‘G’ type RCD
100mA ‘S’ type RCD
Overlap
Overlap = No discrimination
Gap = Discrimination

RCD - discrimination
63A
0.03A
63A
0.1A
63A
40A
0.1A
63A
40A
0.03A
63A
0.3A
Type S
40A 40A 20A
25A
0.01A
WATER HEATER
POWER (SOCKET)
LIGHTING

Current leakages
Earth fault current
A fault current flowing to earth. Typically due to a breakdown of the insulation
* to be prevented
Standing leakage
A current, which flows to earth, or to extraneous-conductive-parts, in a circuit
which, is electrically sound. This current may have a capacitive component
including that resulting from the deliberate use of capacitors.
* to be considered

Standing leakage
Total earth leakage current < 30% In
RCD

1.0 mA to 2.0 mA - for computers
0.5 mA to 1.0 mA - for printers
0.5 mA to 0.75 mA - for small portable appliances
0.5 mA to 1.0 mA - for telecopiers/fax
0.5 mA to 1.5 mA - for photocopiers
around 1.0 mA - for filters
Estimated standing leakage current for electrical & electronics
appliances:
Calculation of the total leakage current from different appliances does not
follow an arithmetic sum and needs to be corrected by a factor of 0.7/0.8.
Standing Leakage
1. IEC-60950 for IT equipment
2. IEC-60335 for Household Electrical Appliances

Question 5
How many computers can be connected to a 30mA RCCB?
Hints:
- Each computer has 2mA residual leakage current.
- Diversity factor = 0.8
1. IEC-60950 for IT equipment
2. IEC-60335 for Household Electrical Appliances
Max. allowable residual leakage = 30mA X 30% = 9mA
No. of computers = 9 / (2 X 0.8) = 5.63
= 5 computers only
28

RCCB to IEC 61008
1. Nominal current In
10-16-25-40-63-80-100A
2. Tripping Current (Sensitivity) In
10-30-100-300-500mA
3. Conditional Breaking Capacity (Inc)
4. Class ‘G’ & ‘S’
5. Types AC, A, B, B+ & F
6. Number of poles (2 or 4)
7. VI or VD
Important Parameters

‘AC’ ’A’ ’B’
Class/Type

Full type F features + Detection of smooth DC currents
and AC current up to 1kHz
Type B
RCD Types
Title, Presentation, Author, Department, Date 31
According to the capability to detect different waveforms of residual current and the relative
sophisticated type testing, today the spectrum of RCDs types covers from pure AC loads up to high
frequency and DC related applications with an increasing level of protection passing from AC and A
types up to F and B types and variants.
Alternating current only
Type AC
Full type AC features + Detection of pulsating current
with DC components
Type A
Full type A features + Detection of mixed frequency
currents.
Type F
Full type B features + Detection of high frequency AC
currents up to 20kHz
Type B+
“Basic” level of earth fault protection – minimum to have.
*Banned in some countries (Germany, France etc).
Minimum to have for loads that consist electronic
devices: computers, tv, radios etc.
It detects mixed frequencies (AC+DC curves): 1-phase
inverter driven washing machine, fridge, A/C…
Type B detects smooth DC current: PV installations,
electric vehicles charging system etc…
Type B+ resistance to higher frequencies at higher
currents: lifts … *currently only in DIN VDE standard.

Title, Presentation, Author, Department, Date 32
RCD Types

RCD - Technology
Electro-mechanical Electronics
Voltage Independent (VI) Voltage Dependent (VD)

RCBO – IEC 61009
◼ Combination of circuit breaker & RCD
◼ Will automatically disconnect…
- Overloads
- Fault currents
- Earth fault currents
◼ Provides protection against…
- Overheating
- Fire
- Electric shock

Question 5
Are we allowed to use RCD VD for residential building?
Y/N

LOAD LOAD
RCD – VI vs VD
Voltage
Independent
(VI)
Voltage
Dependent
(VD)
RCD VD will not work if
there is no voltage.

RCBO – IEC 61009-2-2
RCBO – Electronic (with FE)
Protective Earth
Neutral
Electronic circuit
MOV

Hager RCD range
RCCB ELR
RCBO Add On block

RCD – Add On Block

Special Features
1. PCI
2. Trip indicator
3. IP20
4. Cable guide
5. Built-in “Nuisance Tripping Filter”
6. Accessories
• Aux contact & alarm contact
• Shunt trip
• Under Voltage coil
• Auto Reclosure

RCCB – nuisance tripping
63A
0.1A
MCB
RCCB
63A
63A
0.03A
MCB
RCCB
63A
63A
0.1A
Type G
MCB
RCCB
63A
RCCB without nuisance
tripping filter
Surges due to lightning
or switching
Standing leakages
Too many electronic devices
Design fault
SPD is installed after RCCB
RCCB is of type G
- Install SPD
- Use RCCB type HI/kV
- Split the circuits
- Use more RCCBs
- Install SPD before RCCB
- Or use RCCB type S
1 3
2

Testing the RCCBs
1. Shorting neutral cable to earth
2. Lighting a bulb with the neutral end connected to earth
3. Use a socket plug-in tester
Which test method do you use?
4. Use a proper digital RCD tester

Testing the RCCBs
LOAD
SUPPLY

Maintenance
End user must be consulted and instructed on the correct maintenance
required to maintain the reliability of the equipment installed.
RCD test label must be fixed in a prominent position at or
near the origin of the installation.
MS 1979 COP56 – RCD must be tested at least twice a year.

ELR
06.07.2021 Presentation title

Question
What is the difference between ELR & EFR?

All Hager RCD devices are
manufactured to and comply with
the latest IEC harmonized
Standards

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