101

residual current device

Contents

Principle of operation page 103

Symbols page 104

Protection by page 105Residual Current devices

Special installations page 106-107and locations

Discrimination page 108-109

Add-on blocks page 110

Commercial devices page 111-112-113-114

Earth fault relays page 115-116

Torroids page 117

Avoidance of page 118unintentional operation

Testing of page 119Residual Current Devices

Fault finding page 120

Maintenance page 121

102

residual current device

Residual Current DevicesRCD is a generic term for all types of residual current operateddevice which by definition is: - A mechanical switching device orassociation of devices intended to cause the opening of the contacts when the residual current attains a given value under specified conditions. The more common types are...

Residual Current Operated Circuit Breaker (RCCB)A mechanical switching device designed to make, carry andbreak currents under normal service conditions and to cause theopening of the contacts when the residual current attains a givenvalue under specified conditions. Depending on the age of thesedevices they will comply with either BS EN 61008 or BS 4293.

The British Standard BS 4293 was withdrawn on 1st July 2000and its moratorium period will end in July 2005, which meansmanufacturers may continue to produce residual current devicescomplying with BS 4293 up to 2005 providing the devices are inproduction before July 2000. In line with the Company’s forwardthinking and innovative approach to product development, Hagerhas already introduced residual current devices complying withthe Harmonised Standards

Residual Current Operated Circuit Breaker With IntegralOvercurrent Protection (RCBO)A residual current operated circuit breaker designed to performthe functions of protection against earth fault currents, overloadsand short-circuits. These devices comply with BS EN 61009.‘Appendix G’ of this Standard also covers RCD add-on blocksfor BS EN 60898 circuit breakers

Circuit Breaker Incorporating Residual Current Protection.(CBR)A circuit breaker providing overcurrent protection and incorporat-ing residual current protection either integrally or in combinationwith a residual current unit, which may be factory fitted or fittedin the field. These devices comply with BS EN 60947-2: CircuitBreakers - Annex B.

Socket Outlet Incorporating A Residual Current Device.(SRCD)A socket outlet for fixed installations, which incorporates an inte-gral sensing circuit that will cause the switching contacts in thecircuit to open automatically at a predetermined value of residualcurrent. These will comply with BS 7288: 1990.

Earth Fault Relay A device incorporating the means of detection of an earth faultcurrent, comparing its value to the earth fault current operatingvalue and giving a signal to an associated switching device toopen the protected circuit when the earth fault current exceedsthis value. Relays can be directly connected or fed from a sepa-rate torroid. There is currently no specific standard for this typeof device. It should therefore comply with IEC 755 generalrequirements for residual current operated protective devices.

103

residual current device - principle of operation

Principle of operationResidual current devices monitor the current flowing in a circuitby means of a torroid, which is a small current transformer specially designed to detect earth fault currents. All live conductors will pass through this coil, the currents flowing in thelive conductors of a healthy circuit will balance and therefore nocurrent will be induced in the torroid. Live conductors of a circuitinclude all phase and neutral conductors. When an earth fault ispresent on a circuit, current will be flowing to earth through anabnormal or unintended path. This earth fault path could bethrough a person in contact with live parts as shown in Figure 20as Ic or where insulation has failed through an exposed conductive part shown as Id.

This earth fault current, known as ‘Residual Current’ (Ires), isseen by the torroid as an imbalance. When the magnitude of thisresidual current reaches the sensitivity setting I∆n of the device,it will operate to open the contacts.

Fig 20Current flowing through torroid in healthy circuit

Ires = I1-I2 = 0

Current flowing through torroid in circuit with earth faultIres = I1-I2=Ic + Id

Id

I2

Id

I1

Ic

TechnologyThere are two types of technology available in residual currentdevices, electromagnetic & electronic and both offer very reliableperformance. Electromagnetic devices use a very sensitive torroid, which operates the trip relay when it detects very smallresidual currents. These devices generally require no referenceearth lead and are unaffected by temporary loss of supply, as thepower to trip the device is derived directly from the fault current.

Electronic devices do not need such a sensitive torroid as electronic circuits within the device amplify the signal to operatethe trip relay. However, these devices often require a safety earthreference lead to ensure that the device will continue to operatein the event of the supply neutral being lost. The power to tripthe device is taken from both the fault current and the mainssupply, enabling the overall size of the devices to be reduced.These devices should be disconnected whilst carrying out insulation resistance tests to prevent damage to the device andto avoid incorrect test results. Hager manufacture a range ofdevices using both technologies. The RCCB range, CBR CB add-on blocks and two module RCBO range are electromagneticdevices, while the single module RCBO range and Earth FaultRelays use electronic technology. The CBR MCCB add-ons areavailable in both technologies.

Splitter plates

Trip relay

Torroid

Symbols.A number of different symbols and values are used to identifydevices. It is important to be able to read and understand thesevalues especially when periodically inspecting and testing aninstallation, as the original design data may not be available.

In Rated current of the contacts- Expressed in amperes e.g. 100A.

It is important to remember that where a residual current devicedoes not incorporate overcurrent protection a fuse or circuitbreaker must always be used.

I∆n Sensitivity or residual operating current- Usually expressed in amperes e.g. 0.03A for

30mA

Selective type- Indicates that the device incorporates a tripping

time-delay feature

∆t Time delay setting- Usually expressed in seconds e.g. 0.3

Ue Operational voltage- This is the supply voltage at which the device is expected to operate, however it should be noted that the devices are current operated and therefore may be able to operate at other voltages. Hager two pole RCCB devices are suitable for both 230Vac and 110Vac.

lm Rated making and breaking capacity expressed in amperes e.g. 1500A

Inc Rated conditional short-circuit current

The Hager RCCB range has a making and breaking capacity (Im)of 1500A, which means it can open, or be closed onto a fault ofthat magnitude without damage.If the RCCB is coordinated correctly with a fuse or circuit breaker the manufacturer canassign a rated conditional short-circuit current Inc. This beingthe maximum value of fault current (r.m.s.) without imparing itsfunction.

with MCB’sshort circuit MT NB NC ND

RCCB current capacity 6-63A 6-63A 6-63A 6-63Aof the RCCB onlyB B C D

2 poles

16A 1500A 6kA 10kA 10kA 6kA

25A 1500A 6kA 10kA 10kA 6kA

40A 1500A 6kA 10kA 10kA 6kA

63A 1500A 6kA 10kA 10kA 6kA

80A 1500A 6kA 10kA 10kA 6kA

100A 1500A 6kA 10kA 10kA 6kA

4 poles

16A 1500A 6kA 6kA 6kA 4.5kA

25A 1500A 6kA 6kA 6kA 4.5kA

40A 1500A 6kA 6kA 6kA 4.5kA

63A 1500A 6kA 6kA 6kA 4.5kA

80A 1500A 6kA 6kA 6kA 4.5kA

100A 1500A 6kA 6kA 6kA 4.5kA

Table 35

short circuit current capacity with BS 1361 fuses with BS 88 fuse

RCCB of the RCCB only 60A 80A 100A 60A 80A 100A

2P

16A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

25A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

40A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

63A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

80A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

100A 1500kA 13kA 6kA 3.5kA 11kA 5kA 5kA

4P

16A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

25A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

40A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

63A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

80A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

100A 1500A 13kA 6kA 3.5kA 11kA 5kA 3kA

Table 36

There are situations where these tables are not applicable. Anexample is when an RCCB is incorporated in a consumer unitcomplying with BS EN 60439-3 Annex ZA. Annex ZA prescribesthe conditional short-circuit test to verify the capability of theassembly to safely withstand a 16kA fault.

Hager RCCB devices also feature an earth fault indicator, whichindicates whether the device has operated due to a residual current or to remote tripping by an undervoltage release or shuntdevice. If the device has been operated manually the indicatorwill not change.

AC class These devices detect residual sinusoidal alternating currents, whether these are suddenly applied or rise slowly. However, they may not detect non-linear residual currents which have a dc component, due to power semiconductor switching systems or computer-based equipment connected to the circuit.

A class Devices that will detect both residual sinusoidal alternating currents and residual pulsating direct currents, whether suddenly applied or slowly rising. This type of device is sometimes referred to as ‘dc sensitive’ but cannot be used on pure dc circuits.

This symbol indicates the suitability of thedevice as a disconnector to perform the function of isolation. The RCCB & RCBO devices are lockable by using an MCB locking kit MZ175 and a suitable padlock.

Hi High level filtering - All RCDs manufactured by Hager incorporate a filtering circuit to help eliminate the nuisance tripping that voltage and current transients may cause. These transients may be due to switching of large or non-linear loads, faults on other parts of the installation or disturbances on the supply network.

Disconnector

S

104

residual current device - symbols

105

residual current device - protection by residual current devices

Protection by Residual Current DevicesResidual current devices in their many forms are used on electrical installations to provide protection against three typesof hazard associated with electricity.

(i) Direct contact, defined as ‘contact of persons or livestockwith live parts.

(ii) Indirect contact, defined as ‘contact of persons or livestockwith exposed-conductive-parts which have become liveunder fault conditions.

(iii) Electrical fires caused by arcing in high resistance earthfaults.

Protection against direct contact must be achieved using one ofthe basic measures detailed in regulation 412-01-01 of BS 7671.Where necessary, residual current devices can be used to provide additional supplementary protection, provided therequirements of regulation 412-06 are met, but they must not beused as the sole means of protection against direct contact.

A residual current device will reduce the risk of electric shockprovided it has a residual operating current not exceeding 30mAand an operating time not exceeding 40ms when a residual current of 150mA flows. These characteristics are derived fromthe graph shown in Fig 21 ‘effects of current on the humanbody’, which is taken from IEC 479-1.This illustrates that thehuman body can tolerate very small currents for reasonably longperiods and moderate currents for very short periods.

Fig 21

In zone 2 a person would usually experience no harmful effects,so 20mA for 500ms or 100mA for 100ms would be deemed safe.If a 100mA current was allowed to flow for 200ms it would fallwithin zone 3. This is a more dangerous situation and if allowedto continue for 500ms or more it would enter zone 4, indicating ahigh risk of lethal effects.

Requirements of the Regulations There is an increased risk from electric shock by direct contactwhen equipment is used outside the equipotential zone, due tothe increased likelihood of persons being in hand-held contactwith the equipment and the increased earth fault path impedancelikely to be encountered.

Regulation 471-16 ‘Supplies for portable equipment out-doors’.- Socket outlets rated at 32A or less reasonably expected to

supply portable equipment for use outdoors, as detailed in regulation 471-16-01.

- Circuits supplying portable equipment for use outdoors, connected other than through a socket-outlet by means offlexible cable or cord having a current-carrying capacity of32A or less as detailed in regulation 471-16-02.

Here a residual current device with the characteristics detailed in412-06-02 must be used as the protection is against direct contact i.e. 30mA or less with a maximum disconnection time of40ms when a residual current of 150mA flows.

Section 413 ‘Protection against indirect contact’Residual current devices can be used where protection againstindirect contact is provided by ‘earthed equipotential bondingand automatic disconnection of supply’ and the conventionalmeans of achieving automatic disconnection by fuses or circuitbreakers cannot be met due to high earth fault path impedancepreventing disconnection within the specified times.

- The selection of device sensitivity calculated using the formula Zs I∆n ≤ 50 V from regulation 413-02-16 for TN supply systems.

Where circuits extend beyond the equipotential zone on a TNsystem and are protected by a residual current device, this section may be treated as TT.

Residual current devices are the preferred method of achievingautomatic disconnection of circuits on TT systems detailed inregulation 413-02-19.

- The selection of device sensitivity calculated using the formula RA I∆n ≤ 50V from regulation 413-02-20 for TT supply systems.

Regulation 471-08 ‘Protection by earthed equipotential bond-ing and automatic disconnection of supply’.

- Where protection by earthed equipotential bonding and automatic disconnection is used to protect against indirectcontact on TT systems, regulation 471-08-06 requires that allsocket outlet circuits be protected by a residual currentdevice.

I f

earth electrode

earthingconductor

I f

I f

I f

I f RA

C.P.C.MET

RA Relectrode Rearthing conductor RC.P.C.= + +

I f

I fP.M.E.earthing conductor

I f

I fI f

C.P.C.MET

106

residual current device - and specialinstallations and locations

Part 6 special installations or locationsThe more onerous situations encountered on electrical installations are detailed in part 6 of BS 7671. Extra protectivemeasures need to be taken in these areas. In many cases theuse of residual current devices is a recognised method ofachieving compliance with the regulations.

Section 601 ‘Locations containing a bath or shower’Zones 0, 1,2 & 3 specified in 601-02-01.

601-08-02 for a shower cubicle installed in a room otherthan a bathroom or shower room e.g. bedsitroom or guest bedroom any socket outlet that isnot SELV or a shaver supply unit must be protected by an RCD with I∆n ≤ 30mA.

601-09-02 (iii) fixed current using equipment other than in (i),(ii) and (iv) installed in Zone 1 e.g. ELV transformer for lighting, must be suitable forconditions of that zone and the supply circuit is to be protected by an RCD with I∆n ≤30mA.

601-09-03 in zone 3 current using equipment other thanfixed current using equipment e.g. wall mountedhair dryers, shall be protected by an RCD withI∆n ≤ 30mA.

Although not a requirement of BS 7671 in Section 601, the useof RCD’s to protect electric shower units is common. The manufacturers of electric showers often recommend the use of30mA RCD to protect the shower supply circuit. It is also quitecommon to find RCD protection specified to protect immersionheater supplies, particularly where it is considered there is a riskof the end user gaining access to live parts of the terminal boxon the water cylinder.

Section 602 ‘Swimming Pools’The area in and around a pool is divided into zones.

Zone A is effectively the basin of the pool and/or foot bath.

Zone B extends 2.0 metres beyond the rim of the basin horizontally and 2.5 metres vertically. If there are diving boards, starting blocks or chutes the verticalmeasurements must be taken also from the plane ofthese items but the horizontal measurement is limitedto 1.5 metres.

Zone C extends a further 1.5 metres beyond zone B horizontally and 2.5 metres vertically above thisplane.

Each Zone has specific regulations regarding the type of equipment and the measures of protection to be provided. The use of residual current devices may be used to provide protection.

- If a socket outlet, switch or accessory is to be installedinside the Zones then it is preferable for it to be in Zone C.602-07-02 allows this provided it is either ‘protectedindividually by electrical separation’, ‘protected by SELV’,

‘protected by a residual current device of 30mA or less’ or‘a shaver socket to BS 3535’.

- If it is not possible to locate socket outlets outside Zone Bthen they may be installed inside, providing they comply withBS EN 60309-2 and meet all the requirements of 602-07-01.This requires them to be more than 1.25m (arms reach) outside the border of Zone A, at least 0.3m above the floorand protected by either an residual current device of30mA or less, or by electrical separation with a safety-isolating transformer placed outside all three of theZones.

- Other equipment installed in Zone C must be protected in accordance with 602-08-03 protection individually by electrical separation, SELV or a residual current devicerated at 30mA or less.

Due to the nature of the installation further protection by enclosures of a high IP rating is also required.

Section 604 ‘Construction site installations’Regulation 604-04-01 requires that on TN systems the maximumdisconnection times for circuits meet the times laid out in table604A. For 230V circuits this means a reduced disconnection timeof 0.2 seconds.

- Residual current devices may be used if the overcurrent protective devices cannot meet the disconnection times intable 604A. (604-04-07)

- Regulation 604-04-08 requires that for TN systems the formula in 413-02-16 be replaced by Zs I∆n ≤ 25 V reducingthe maximum touch voltage to 25V

- Regulation 604-05-01 requires that for TT systems theformula in 413-02-20 be replaced by RA I∆n ≤ 25 V.

RCD maximum Zs or RA values

maximum touch voltage

I∆n (A) 25V 50V

0.01 2500Ω 5000Ω

0.03 833Ω 1666Ω

0.1 250Ω 500Ω

0.3 83.3Ω 166.6Ω

1 25Ω 50Ω

3 8.33Ω 16.66Ω

Earth electrode resistances over 200Ω are likely to be unstable.

- For compliance with regulation 604-08-03 every socket outletmust be protected by one or more of the following

• automatic disconnection and reduced low voltage system

• A residual current device rated at 30mA or less

• SELV

• Electrical separation

When using residual current devices to supply a complete installation, consideration should be given to ‘S’ type or time-delayed devices, particularly if heavy cranes, for example,are to be operated. In this instance the use of a 30mA device toprotect the whole system would be ill advised due to the potential loss of construction time if the device were to operate.

The scope of section 604 does not extend to installations in construction site offices, cloakrooms, meeting rooms, canteens,restaurants, dormitories, toilets etc., where the general requirements of the IEE Wiring Regulations apply.

107

residual current device - and specialinstallations and locations

Section 605 ‘Agricultural & Horticultural Premises’These require more careful consideration as there is increased danger from environmental conditions such as the presence ofwater, fire risk from storage of combustible materials such asstraw and hay, and the susceptibility of livestock to the effects ofelectric shock.

• To safeguard against the risk of fire Regulation 605-10-01requires that a residual current device having a rated residualoperating current not exceeding 500mA protect circuits notessential to the welfare of livestock. A device of ≤300mA maybe required for compliance with 482-02-06 where com-bustible materials are stored or processed.

• Regulation 605-05-09 requires that for TN systems the formula in 413-02-16 be replaced by Zs I∆n ≤ 25 V reducingthe maximum touch voltage to 25V.

• Regulation 605-06-01 requires that for TT systems the formula in 413-02-20 be replaced by RA I∆n ≤ 25 V.

• Regulation 605-03-01 requires all socket outlets not suppliedby a SELV source be protected by a 30mA RCD, evenreduced low voltage sockets must be protected in thesetypes of installation.

Section 606 ‘Restrictive conductive locations’Section 606 outlines the extra precautions to be taken when equipment is intended to be used in locations where movementis restricted and contact with conductive parts is likely.

• Where the Class II equipment is used to provide protection against indirect contact, as detailed in 606-04-01, further protection must be provided by a residual currentdevice rated at 30mA or less.

Section 608 division one ‘caravans & motor caravans’

• Regulation 608-03-02 requires all circuits not protected byClass II or equivalent insulation to be supplied by a residualcurrent device with a maximum sensitivity of 30mA.

• If RCBO devices are used on the final circuits instead of onemain 30mA RCCB then they must be of the two-moduleSPSN type that disconnects all live conductors in accordance with regulation 608-04-01. A live conductor canbe phase or neutral.

Section 608 division two ‘caravan parks’

• Regulation 608-13-05 requires all socket outlets connectingto caravans to be protected individually or in groups of notmore than three by a 30mA residual current device. As thereis no way of discriminating between the devices in the caravans and on the site it is advisable to install the sitedevice in the caravan pitch supply equipment enclosure adjacent to the socket to avoid unnecessary inconvenienceto the consumers.

GeneralRecent changes in BS 7671 : 2001, have addressed the issue ofusing RCD’s to prevent the initiation of fires in areas of increasedfire risk due to arc faults arising from a breakdown of insulation.482-02-06 (i) requires wiring systems other than mineral insulated or busbar trunking to be protected by an RCD with I∆n≤ 300mA in accordance with 531-02-04 i.e. ensuring to minimiserisk of nuisance tripping.

108

residual current devices - discrimination

DiscriminationTo achieve discrimination only the protective device immediatelyupstream of a fault must disconnect, leaving the remainder ofthe installation energised. Regulation 533-01-06 requires thatwhere necessary to prevent danger any intended discriminationmust be achieved. Where residual current devices are used tosupply multiple circuits, due to the very low residual operatingcurrents it is impossible to guarantee time/current discriminationbetween the upstream RCD and the downstream fuses or circuitbreakers. The use of builtin time delays will provide discrimination.

Typical RCCB Time/Current Characteristics

Discrimination between Circuit Breakers with add on RCCBs.Having decided on the type and the limit of discrimination of the circuit breakers in the system, it is very important to consider thediscrimination between any add on RCCBs. In theory it is possible to achieve current discrimination between RCCBs butthe limit of discrimination is too low for practical purposes. Timediscrimination is by far the best method and is achieved bydelaying the tripping of the upstream RCCB.

Note that the limit of discrimination is the instantaneous settingof the associated circuit breaker. In other words if the earth faultcurrent is greater than the instantaneous trip setting of the associated circuit breaker, the circuit breaker will trip regardlessof the time delay on the RCCB.

40ms

100mA ’S’ type device

100mA type device

30mA type device

130ms 300ms 500ms

Earth fault 150mA

Downstream 30mA

Upstream 100mA

Tripping Time

109

residual current devices - discrimination

Where it is necessary to provide residual current protection to allor large numbers of circuits the best method is to install RCBOdevices in parallel with each other. In this way compliance with314-01-01 would be achieved and discrimination between residual current devices would not need to be considered.

The main drawback with this solution is cost, so a compromisewould be to split circuits into smaller groups and use residualcurrent devices in parallel. Devices of differing sensitivities canbe utilised to provide the required level of protection.

On TT systems where residual current devices are commonlyused at the origin of the installation, the practice of having amain switch-disconnector feeding two or more residual currentdevices which each feed one or more final circuits is only one ofseveral methods of achieving compliance. On larger installationsthe need for devices in series is often a requirement. Due to thevery low operating currents of residual current devices, it isunlikely that current discrimination will be achieved betweengeneral purpose devices as the prospective earth fault current islikely to be much higher than the I∆n settings of the devicesinstalled.

Regulation 531-02-09 dictates that where two or more residualcurrent devices are in series, and discrimination is necessary toprevent danger, the characteristics of these devices shall providethe intended discrimination. This refers to selective type or time-delayed residual current devices. These incorporate an in-built or adjustable time delay, which allows upstream devicesto use this delay to give downstream units sufficient time tooperate. The discrimination achieved by using ‘S’ type devicescan be illustrated by referring to table 1 of BS EN 61008-1.

For simple single phase TT installations a good compromisewould be to use a split-load time-delayed consumer unit with a100mA ‘S’ type RCD main switch feeding the entire board, butwith a number of final circuits also fed through a 30mA generalpurpose ‘G’ RCD.

Where RCBO devices are to be installed downstream of an ‘S’type RCD the RCBO must disconnect all live conductors of thecircuit. This is to prevent a loss of discrimination in the case of aneutral to earth fault, which would not be cleared by a devicewhich only disconnected the phase conductors.

Note: A neutral conductor is defined as a live conductor.

N

SPSN RCBO

100mA 'S' type RCCB

N

N

N

SPSN RCBO

SPSN RCBO

SPSN RCBO

MCB

30mA RCCB

100mA 'S' type RCCB

MCB

MCB

MCB

MCB

MCB

MCB

MCB

Disconnector

MCB

30mA RCCB

100mA RCCB

MCB

MCB

MCB

MCB

MCB

MCB

MCB

Disconnector

SP&N RCBO

SP&N RCBO

SP&N RCBO

SP&N RCBO

RCCB add-ons Commercial applications

110

residual current device - add-on blocks

MCB & RCCB add-on association chart

RCCB add-ons3 sensitivities 30mA, 100mA & 300mA instantaneous.2 sensitivities 100mA & 300mA time delayed.RCCB add-ons can be associated with devices rated from 0.5 to 63A in 2 and 4 poles.

Wiring diagram

connection capacity

63A = 16mm2

63A = 25mm2

characteristicseasy coupling (drawer system)easy disassembly (without damage)conforms to BS EN 61009 Appendix G

Mounting

1 31 3

2 4

2 pole 4 pole

In ≤63A ≤63A

sensitivity 30mA 100mA 300mA 30mA 100mA 300mA

cat. ref. (standard) BD264 BE264 BF264 BD464 BE464 BF464

cat. ref. (time delayed) BN264 BP264 BN464 BP464

MCB suitability

NB 6-63A 6-63A 6-63A 6-63A 6-63A 6-63A

NC 0.5-63A 0.5-63A 0.5-63A 0.5-63A 0.5-63A 0.5-63A

ND 6-63A 6-63A 6-63A 6-63A 6-63A 6-63A

width when combined 4 module 7 modulewith MCB 70mm 122.5mm

30mA 300mA 300mA 30mA 300mA 300mAtime delay time delay

NM BD285 BF285 BP285 BD485 BF485 BP485

80 - 100A 80 - 100A 80 - 100A 80 - 100A 80 - 100A 80 - 100A

5.5 modules 10.5 modules96.25mm 183.75mm

2 1

In E

111

residual current device - commercial devices

On larger systems more than one level of time-delay devicesmay be required to achieve discrimination and Hager MCCBCBR & Earth Fault Relay ranges allow delays of up to 3 seconds.Where adjustable devices are used and someone other than askilled or instructed person is likely to operate it, the devicemust be designed or installed in such a way that it is not possible to modify or adjust the settings without the use of atool or key, and that the modification results in a visible indication of its setting or calibration as required by regulation531-02-10.

CBR devices are available for MCCBs up to 250A and offeradjustable settings for both sensitivity and time delay. Earth faultrelays can be used for all MCCB devices

Frame size125A

Characteristics

product H125B

number of poles 3, 4

electrical characteristicsnominal current max (40º) in A 125A

240-415V

relayssensitivity I∆n 0.03, 0.1, 0.3,

1, 3, 10A

inst 0.06, 0.15,0.3, 0.5,1

test button mechanical yes

test button electrical yes

reset button yes

sensitivity selection yes

optical scale yes

fault indication yes

50% I∆n contact indication yes

anti transient yes

cable capacitiesrigid mm2 70

flexible mm2 70

dimensions 101 x 140 x 74

weight (kg) 4 pole 2.5

mountingdin rail yes

fixing lateral

Frame size 160 - 250A

Characteristics

product H160B H250B

number of poles 4 4

electrical characteristicsnominal current max (40º) in A 160A 250A

240-415V 240-415V

relayssensitivity I∆n 0.03, 0.1, 0.3,1.3,

10A

inst 0.06, 0.15,0.3,

0.5,1

test button mechanical yes yes

test button electrical yes yes

reset button yes yes

sensitivity selection yes yes

optical scale yes yes

fault indication yes yes

50% I∆n contact indication yes yes

anti transient yes yes

cable capacitiesrigid mm2 120 120

flexible mm2 120 120

dimensions 140 x 104 x 91

weight (kg) 4 pole 2.75 2.75

mountingdin rail no no

fixing direct to product

112

residual current device

Residual current blocks for MCCB’sElectromechanical versions are prevented from unwanted trippingcaused by transient leakage currents (type AC)

In addition to the electromechanical type, electronic version alsoaffords protection against direct current faults (type A)

Indication of a fault residual- upon detection of residual fault current:

1 the ‘reset button of the RCD releases automatically2 the breaker lever switches to position ‘O’

- it is impossible to re-engage the breaker as long as the RCD has not been re-engaged, with the ‘reset’ button depressed, or as long as the fault residual persists in the system - positive safety.

Reset buttonpermits the RCD to be re-engaged after tripping, thus also allowingthe re-engagement of the breaker

Test buttonpermits periodic testing of the residual detection function. Themaximum residual fault current which can be tested in I∆n.

LED display- an ‘on’ display indicates the RCD is functioning correctly

- a display ‘50% I∆n’ indicated when a residual current of 50% ofthe setting is detected

SD contact + 50% contacta fixed contact (3A-250V) allows remote indication of a trip, a furthercontact permits a signal to be transmitted indicating when the faultcurrent level has passed beyond 50% of the set value I∆n

range of settings- sealable settings for both sensitivity and time delay

- an RCD adjusted to a sensitivity of 30mA cannot support a time delay - the tripping must be instantaneous

On 125A, 160A and 250A RCD’s the mechanical test button alsoassures isolation of the RCD’s electronic circuit, permitting risk freeinsulation tests up to 2500V

Release

N L1 L2 L3

N L1 L2 L3

CA

125ATestbutton

N L1 L2 L3

N L1 L2 L3

Testbutton

CA

50%

ELECTRONICCARD

ON

125A250A

113

residual current device

Push to trip

HB 101312101

230-415 V M50/60 HzIn 125 AIEC 60947-2

53 54

50 %IDn

(0,1 A - 250 V )M

12 11 14

CA

(3 A - 250 V )M

test

RCD blocks 125A

RCD blocks 160A and 250A

Electromechanical version

• fixed sensitivity

• instantaneous trip

• anti-transient (nuisance trips)

• residual fault output contact

• reset button

• test button

Electronic version

• adjustable sensitivity (30, 200mA, 1, 3, 10A)

• adjustable trip delay

• anti-transient and DC sensitive

• contact for signalling trip

• contact for signalling 50% fault level

• LED indication of - functioning- isolation level

• reset button

• test button

• adjustable sensitivity (30, 200mA, 1, 3, 10A)

• adjustable trip delay

• anti-transient and DC sensitive

• contact for signalling trip

• contact for signalling 50% fault level

• LED indication of - functioning- isolation level

• reset button

• test button

5354

50 %

IDn

(0,1

A -

250

VM

)

1211

14

CA

(3 A

- 2

50 V

M)

V M V M

1

2

test

reset

HB 211334211 1

Push to trip

127-415 V M 50/60HzIn 250AIEC 947-2

D50 % I n ON

114

residual current device

Breaker + RCD add-on block 400ASwitch + RCD add-on block 400A

The RCD block is mounted at the factory, and only onbreakers of the electromechanical type

electronic add-on RCD 320A and 400A

• adjustable sensitivity (30, 100, 300,500mA)

• trip delay 0 to 1s (inst, 60, 100, 250, 500ms and 1s)

• sealable settings

• test button

• trip signal terminal plus front display

• power supply from above (obligatory)

• anti-transient (nuisance trips) and DC sensitive

The RCD block causes the breaker to trip via a specific trip coil.

The 3 wires make an SD signal contact when an RCD tripoccurs.

HB 701 312701 5 0,03

IDn (A)

0,1

0,3

0 0,15

0,2

test

110/480 V M50/60HzIn 400 AIEC 947-2

0,5

1

31030

0,5

1

2

Dt (s)

3

12

V~6 A

N

Blue

Black

RedN

➀ test button

➁ I∆n adjustment

➂ delay adjustment

115

residual current device - earth fault relays

Earth Fault RelaysThese residual current sensing devices are used in conjunctionwith either a contactor, an alarm or more typically, moulded casecircuit breakers. They enable protective conductor protection tobe provided on devices up to 800A. Earth fault relays are manufactured to and comply with IEC 755.

The devices monitor the residual current of a circuit by means ofa separate torroid. This can be mounted remotely up to 50mfrom the relay and is sited where it is most convenient in respectof the circuit cables to be monitored, particularly useful wherelarge conductors have been used.

Regulation 531-02-02 requires that all live conductors of the protected circuit shall be enclosed by the magnetic circuit transformer, with the exclusion of the associated protective conductor. This is easily achieved with standard RCCB & CBRtype devices. With Earth Fault Relays the sensing transformer ortorroid is sited remotely and therefore more care needs to beobserved when installing cables. The torroid will then sense anyimbalance in the circuit conductors and when the value reachesthe I∆n setting the earth fault relay will provide a signal to operate the device, disconnecting the supply.

Regulation 531-02-06 states that when a residual current deviceis powered from an auxiliary source, it must either operate automatically in the case of failure of the auxiliary circuit, or oneof the following conditions must be fulfiled.

1. Protection against indirect contact is maintained even in thecase of failure of the auxiliary source, or

2. The device is incorporated in an installation intended to besupervised, tested and inspected by an instructed or skilledperson.

non adjustable adjustableHR100 HR120 HR200 HR210 HR211 HR212 HR213

supply voltage ~50/60HZ 220-240V 220V - 240Vresidual voltage ~50/60Hz 500V max 500V maximumpower absorbed 5VA 5VAoutput volt free contacts volt free contactscontact rating 10A / 250V AC1 10A/250V AC1sensitivity I∆n 0.03A 0.3A 0.03A/0.1A/0.3A/1A/3Ainstantaneous/time delay instantaneous instantaneous instantaneous or time delay 0.13s/0.3s/1s/3storroid withstand capacity 50kA / 0.2s 50kA/0.2sdistance between torroid and relay 50 metre maximum 50 metre maximumrelay cable connection - rigid 1.5 to 10 1.5 to 10

- flexible 1 to 6 1 to 6

torroid cable connection - rigid 1.5 to 4 1.5 to 4

- flexible 1 to 2.5 1 to 2.5

relay working temperature -5°C to +40°C -5°C to +40°Cstorage temperature -25°C to +40°C -25°C to +40°C

torroid working temperature -5°C to +80°C -5°C to +80°Cstorage temperature -40°C to +80°C -40°C to +80°C

1 3 5 7 9 11 13

2 4 6 8 10 12 14

HR 213

reset

test

rese

t

test

5 15 30 45 60 75

31

0,3

0,1 0,03 3 1

0,3

0,10,03

% In

In (A) t (s)

BE

control protective

device

116

residual current device

main characteristics“Reset” buttonWhen pressed, the output remains switched and return to normalis obtained by either: by pressing the “reset” clear pushbutton or cutting off the power supply. If the “reset” button is not pressedthe device remains in the fault position.

Test buttonPressing the test button allows a fault simulation which operatesthe relay and the output contacts.The fault level display is shown by an LED on the front of the product.

I∆n selectorsensitivity setting: 0.03A instantaneous only0.1A/0.3A/1A and 3A instantaneous or time delay

Time delay selector ∆tadjustable time setting - instantaneous/0.13s/0.3s/1s and 3s

Sealable settingsa sealable cover prevents interference once the settings havebeen made.

Standard output (1 C/O contact)switching to state 1 on:– failure of the core/relay connection– fault current in the monitored installation

Positive safety outlet (1 C/O contact)switching to state 1: switching on the powerswitching to state 0: failure of the core/relay connection

fault current in the monitored installationfailure of relay supplyinternal failure of relay

Optical scale display by 5 LEDs of the fault in % of I∆nCommon pin 6:State 1 : output terminal 8State 0 : output terminal 4

electrical connections

fed from either input or output side

117

residual current device - earth fault relay torroids

circular torroids

rectangular torroids

mounting of circular torroids

B1,5

A

14D 175,5

C E

33,5

BA1

A2

2.5

14

D

G

E C

H

F

mounting of torroid upstream downstream

with cables

type of torroid

U 1000 RO2VSWA cables with internal sheath

U 1000 RO2VSWA cables with internal sheath removed

U 1000 RO2Vinsulated and sheathed singles

HO7VKinsulated single cables

torroid 70 4 x 95 4 x 150 4 x 70 4 x 120

torroid 105 4 x 240 4 x 300 4 x 185 4 x 240

torroidtorroidtorroid torroid

reference type dimensions (mm)

A B C D E

HR911 Ø70 70 132 115 60.5 98

HR912 Ø105 105 175 158 82 141

HR913 Ø140 140 218 200 103.5 183

reference type dimensions (mm)

A1 A2 B C D E F G H

HR920 70x175 70 175 172 258 85 225 22 40 8.5

HR921 115x305 115 305 232 400 116 360 25 50 9.5

HR922 150x350 150 350 281 456 140 415 28 50 10.5

118

residual current device - avoidance of unintentional operation

Avoidance of unintentional operationIn order to maintain the continuity of supply to an installation, itis important to select the most appropriate equipment and components at the design stage before work is undertaken.Every installation should be divided into circuits to avoid dangerand minimise inconvenience. This requirement is particularlyimportant where residual current devices are to be used due tothe relatively low operating currents. Consideration must begiven to circuit protective conductor currents and to earth faultcurrents.

Nuisance trippingOne of the most widely experienced problems with residual current devices is nuisance tripping. This is the unwanted operation of the device causing inconvenience to the end userdue to protective conductor currents, transients or switching of capacitive circuits. The best way to safeguard against this is touse devices only where they are necessary for compliance withBS 7671 or where it is deemed necessary due to the nature ofthe installation. The practice of connecting general purpose circuits to the portion of a split-load protected by a residual current device on a standard domestic distribution board couldincrease the possibility of nuisance tripping and lead to subsequent non-compliance with BS 7671. Regulations 314-01-01 & 314-01-02 require that circuits be subdivided to avoid danger and minimise inconvenience anddanger that can arise from loss of supply, especially to lightingcircuits.

Protective conductor CurrentWhen selecting devices care should be taken to avoid unwantedtripping, making it necessary to consider protective conductorcurrents. These are currents that flow to earth, or to extraneous conductive parts, in a circuit that is electrically sound. This current may have a capacitive component including that resultingfrom the deliberate use of capacitors.

Filters used in IT equipment to protect against transients are atypical example of equipment that as a normal function of itsoperation use the circuit protective conductor as a functionalearth to dissipate protective conductor currents safely. The protective conductor currents for each piece of equipment aregenerally very low, usually less than 3.5mA, but their effects willbe cumulative, particularly on socket outlet circuits in officeswhere a number of items of equipment incorporating filters are tobe used.

Regulation 607-07-01 states that when more than one item ofequipment having a protective conductor current exceeding3.5mA in normal service is to be supplied from an installationincorporating a residual current device, the circuit arrangementshall be such that the residual current which may be expected tooccur, including switch on surges, will not trip the device.

Typical causes of unwanted RCD tripping problems.The cause of intermittent tripping problems can often be difficultto determine and resolve, the cause can come from within aninstallation or from the electrical supply entering the installation.

Possible causes upstream of the device• Loose connections

• Mains borne disturbances, the effect of these can be worsewhen the device is under no load.

• Switching of large machinery or plant.

• Lightning activity

Possible causes downstream of the device• Loose connections

• Mains borne disturbances, the effect of these can be worsewhen the device is under no load.

• Incorrectly selected (too sensitive)

• Standing protective conductor currents from equipment and appliances

• Wet plaster on new installations

• Moisture ingress or condensation

• Old appliances with insulation breaking down (particularlyfridges and freezers)

• Mineral insulated cables

• Heating elements, electric cookers etc.

• Neutral to earth faults (TT & TN-S systems - trip, TN-C-Ssystem - no trip)

• Crossed neutrals on split-load consumer units

• Highly capacitive circuits

• Faulty appliances, appliances such as washing machineshave a program cycle, it is possible that the earth fault isonly present during particular parts of that cycle.

• Damage or deterioration to cable insulation, particularly toold cables.

• Capacitance in long cable runs

• Interference by radio transmitters

Ph

cpc

N

230V~

1mH

1mH

Protectiveconductorcurrent

I

47 nF

47 nF

I = V = 230 = 3.39mAZ 67700

Xc = 1 = 67.7kΩ at 50Hz2πfC

Z = X + X2 2

L C

119

residual current device - testing residual current devices

Testing of devicesTo ensure that all devices operate correctly and that all intendedsafety measures are covered, it is imperative that the devices aretested after they have been installed and at regular intervalsthroughout their service life. Initial testing of the residual currentdevice should be undertaken before connecting the outgoing circuit cables to the device to ensure that only the device isbeing tested and that no parallel fault paths which may exist inthe circuit wiring interfere with the results. The need to disconnect the load conductors before testing is even moreimportant when testing ‘S’ type devices, as a potentially dangerous voltage could be present on exposed- and extraneous-conductive-parts. Regulation 713-13-01 requiresresidual current devices to be tested independently of any internal testing facility on the device, such as the test button.Testing must be carried out with a proprietary residual currentdevice test meter, which is regularly calibrated and is suitable forthe devices installed. The procedure recommended by Hager is;

1. 1/2 I∆n trip test

2. 100% I∆n trip test

3. 5 x I∆n trip test (if applicable)

4. DC test (if applicable)

5. operation of the test button

The test results should be within the parameters set out in theapplicable standard.

The new Harmonised Standards of BS EN 61008 & BS EN 61009allow the device to operate within 300ms at 100% I∆n. The previous Standard BS 4293 had a limit of 200ms. When testingdevices care must be taken to ensure that the test results arecompared to the correct Standard. Guidance can be found in thelEE on-site guide. The trip time parameters at a test current of 5 x I∆n remain unchanged and are 40ms for all Standards.

When periodically testing a residual current device with a meter,it is often advisable to undertake the 5 x I∆n test first. If thedevice fails this test, it is a good indication that the quarterly testbutton check has not been carried out and that dirt or dust onthe contacts may be causing a slower operation than normal.Before rejecting the device completely, the test should be carriedout twice more, as it is quite usual for the device to operateproperly after these two subsequent operations. In the same wayas when testing the device initially, the outgoing or load cablesshould be removed before the test is carried out.

To ensure the device continues to operate within the definedparameters it is important that the device is tripped periodicallyby operating the test button. This should be done at regularintervals not exceeding three months.

Standard Type I∆n 1⁄2 x I∆n (t) I∆n (t) 5 x I ∆n

≤ 30mA ≤ 40msBS EN 61008 G ≥ 2000ms ≤ 300ms

S > 30mA 130-500ms N/A

≤ 30mA ≤ 40msBS EN 61009 G ≥ 2000ms ≤ 300ms

S > 30mA 130-500ms N/A

< 30mA ≤ 40msBS4293 G ≥ 2000ms ≤ 200ms

Time-delay > 30mA 300-400ms N/A

Table 37

120

residual current device - fault finding with residual current devices

Fault finding with residual current devicesThere are many problems that may be encountered whilst fittingand testing residual current devices. The problems can beencountered at the installation stage or at anytime after installation. The majority of problems are installation related. Asimple flowchart is provided to aid problem solving. Access tolive parts is required to carry out the complete sequence therefore it should only be carried out by a competent electrician.

Electricians RCD fault diagnosis chart

Device trips (will not reset)

Device trips intermittently

Device does not trip (test button)

Remove load cables & retest

Remove load cables press test button

Remove load cables & retest

Test device with RCD Tester

Test device with RCD Tester

Disconnect all loads

Locate & repair fault in circuit wiring

Neutral to earth fault on switched circuit

Intermittent fault

Phase to earth fault on switched circuit

Switch on or reconnect circuit phase conductors one at a time

Re-connect circuit neutral conductors one at a time and reset device

device resets?

device resets?

device resets?

device resets?

device resets?

socket circuit?

obvious fault

Replace RCD

Disconnect all circuit neutral conductors

Device OK check for circuit /

external faults

pass tests?

pass tests?

earth fault on circuit wiring

Switch off or disconnect circuit phase conductors & reset the device

Locate & repair faulty appliance

Unplug all appliances reset the device

Repair fault

pass 50% I∆n test?

pass I∆n test?

pass 5 x I∆n

test?

pass 100% I∆n test?

No

No No

No

NoNo

No

No No

No

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes Yes

Yes

Yes

Yes

Yes

No

Fig 22

121

residual current device - maintenance

MaintenanceChapter 34, Maintainability Regulation 341-01-01 requires thatan assessment be made of the frequency and quality of maintenance that the installation can reasonably be expected toreceive during its intended life. This assessment shall, whereverpracticable, include consultation with the person or body whowill be responsible for the operation and maintenance of theinstallation. Having regard to the frequency and quality of maintenance expected, the requirements of Parts 4 to 7 shall beapplied so that during the life of the installation:

(I) any periodic inspection, testing, maintenance and repair likely to be necessary can be readily and safely carried out,and

(ii) any protective measure for safety remains effective, and thereliability of equipment is sustained.

Before an installation is handed over to a client, proper instruction on the use and maintenance of residual currentdevices must be given and precise written instructions should beleft with the installation operating manual or user instructions

Regulation 514-12-02 requires that a label be fixed at or near theorigin of the installation, with the wording shown, in every installation that includes a residual current device.

Accessibility of equipmentThe correct and adequate sitting of residual current devices isvery important if the end user is to be able to operate the tripbutton on the device. For compliance with BS 7671, positioningof residual current devices must take into considerationRegulation 513-01-01 which states that every piece of equipment that requires operation or attention by a person shallbe so installed that adequate and safe means of access andworking space are afforded for such operation or attention.

Compatibility Radiated immunity:

For residual current devices:

• Do not put a high intensity cable close to the device: In < 200A for a cable in contact with the side of a device. In < 300A for a cable at 1 cm from the side of the device. In < 400A for a cable at 2cm from the side of the device.

• Do not put a high breaking capacity MCB (Icu > 25kA) sideby side with the RCD.

• Do not put a transformer side by side with the RCD.