1. Electrical Equipment A) Transformer

Transcription

1 Standards and Basic Equipment Date : 15 November 2010

2 1. Electrical Equipment 2. Terminology 3. Code & Standard

3 1. Electrical Equipment A) Transformer

4 A1) One Transformer and 11kV Switchgear in High Rise Building

5 A2) Three Transformers and 11kV Switchgear in High Rise Building

6 A3) Minimum Requirements for the Customer s Switchroom Adjacent to Substation ti for Multi-transformer transformer Installation ti

7 E) MCCB D) Fuses Combination Unit (Switch Fuse) B) Switch Board C) ACB

8 1. Electrical l Equipment B) Factory-built built-assembly bl (Switchboard)

9 Typical forms of separation by barriers of partition Form 1 Form 2 Form 3 Form 4 No separation Separation of busbar from the functional units Separation of busbar from the functional units and separation of all functional units but not of their outgoing terminals, from one another. Separation of busbar from the functional units and separation of all functional units, including their outgoing g terminals, from one another.

10 1. Electrical l Equipment C) Air Circuit Breakers (ACB)

11 1. Electrical l Equipment D) Fuse Combination Units and Switch- disconnections

12 1. Electrical l Equipment E) Moulded Case Circuit Breakers (MCCB)

13 I) KWH Meter F) Busbar Riser H) MCB G) MCB Distribution G) MCB Distribution Board

14 1. Electrical Equipment F) Busbar Risers

15 1. Electrical l Equipment G) MCB Distribution ib ti Boards

16 1. Electrical l Equipment H) Miniature Circuit Breakers (MCB) - 1

17 1. Electrical l Equipment H) Miniature Circuit Breakers (MCB) - 2

18 1. Electrical l Equipment I) KWH meter

19 L) Lighting Switch K) RCCB J) Consumer Unit M) Lampholder N) Socket Outlet O) Connection Unit

20 1. Electrical l Equipment J) Consumer Unit

21 1. Electrical l Equipment K) Residual Current Circuit Breakers (RCCB)

22 1. Electrical l Equipment L) Lighting Switches

23 1. Electrical l Equipment M) Lampholders

24 1. Electrical l Equipment N) Socket outlets t

25 1. Electrical l Equipment O) Connection Unit

26 1. Electrical l Equipment P) PVC Cable - 1

27 1. Electrical l Equipment P) PVC Cable - 2

28 2. Terminology - 1 Live Part A conductor or conductive part intended to be energized in normal use, including a neutral conductor. Electrical Installation An assembly of associated electrical equipment supplied from a common origin to fulfill a specific purpose and having certain coordinated characteristics.

29 2. Terminology - 2 Electrical Equipment Any item for such purposes as generation, conversion, transmission, distribution or utilization of electrical energy, such as machines, transformers, protective devices, wiring materials, measuring instruments, accessories, appliances and luminaries. Fixed Appliance An appliance which is fastened to a support or otherwise secured at a specific location in normal use.

30 2. Terminology - 3 Portable Appliance An appliance which is or can easily be moved from one place to another when in normal use and while connected to the supply. Earthing The act of connecting the exposed conductive parts of an installation to an earth electrode.

31 2. Terminology - 4 Protective Conductor A conductor used for some measure of protection against electric shock and intended for connecting together any of the following parts: Exposed conductive parts, Extraneous conductive parts, Main earthing terminal, Earth electrodes The earth point of the source

32 2. Terminology - 5 Equipotential Bonding Electrical connection maintaining various exposed conductive pats and extraneous conductive parts at substantially the same potential Exposed Conductive Part A conductive part of equipment which can be touched and which is not a live part but which may become live under fault conditions

33 2. Terminology - 6 Extraneous Conductive Part A conductive part liable to introduce a potential, generally earth potential, and not forming part of the electrical installation. Circuit Protective Conductor (CPC) A protective conductor connecting exposed conductive parts of equipment to the main earthing terminal.

34 2. Terminology - 7 Earthing Conductor A protective conductor connecting a main eathing terminal of an installation to an earth electrode or to other means of earthing. Direct Contact Contact of persons or livestock with live parts which h may result in electric shock.

35 2. Terminology - 8 Indirect Contact Contact of persons or livestock with exposed conductive parts made live by a fault and which may result in electric shock. Skilled Person A person with technical knowledge or sufficient i experience to enable him to avoid danger which electricity it ay create.

36 2. Terminology - 9 Instructed Person A person adequately advised or supervised by skilled persons to enable him to avoid dangers which electricity may create. Low Voltage (L.V.) Vl Voltage normally exceeding Extra Low Voltage Vl but not exceeding 1000V a.c.. or 1500 d.c.. between conductors, or 600V a.c.. or 900V d.c.. between conductors and earth.

37 2. Terminology - 10 Extra Low Voltage Voltage normally not exceeding 50V a.c.. or 120 d.c.,., whether between conductors or to earth.

38 3. Power Distribution and Wiring Design Consideration -1 Installation Cost Purpose and planned duration of the installation Environment factors and installation conditions Type of building construction Flexibility of the system and circuit arrangement Appearance of the finished installation Safety aspect Nature of power supply and type of earthing system

39 3.1 Installation ti at High Humidity Environment The wiring system should be selected and erected so that no damage is caused by high humidity or ingress of water during installation, use and maintenance. All joint should be suitably insulated and protected against the effects of moisture or water. Copperclad aluminum conductors should not be used. Every entry to finished ducts or trunking should be placed so as to prevent the ingress of water or be protected against such ingress. Where water may collect or condensation may form in a wiring system, provisions should be made to drain it away.

40 3.1 Installation at Adverse Ambient Temperature The wiring system including cables and wiring accessories, should be suitable for the highest and lowest ambient temperature that likely to encountered. The electrical insulation shall withstand the maximum permissible operating temperature of the class of insulation to BS Class Y A E B F H Temp( o C)

41 3.1 Installation at Adverse Ambient Temperature -2 For general-purpose PVC cable, the maximum permissible conductor of operating temperature is 70 o C and the maximum permissible ibl ambient temperature is 65 o C. In every vertical trunking or duct wiring installations, suitable internal barriers sould be provided between floors or at intervals of 5m whichever h is the less.

42 3.1 Installation at Adverse Ambient Temperature -3 Suitable measures shall be provided to avoid the effects of heat from external source including solar gain such as shielding or placing sufficiently far from the source of heat or selecting insulation suitable for those temperature.

43 3.1 Index of Protection The code that specifies the protection of encloses that t can be used within certain environment. The first numeral indicate the protection against ingress of solid bodies. The second number indicate the protection against the ingress of liquids. IP XX

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47 3.1 Index of Protection General Use Indoor Use: IP2X Outdoor Use: IP54 (Weather-proof)

48 3.1 Application of Wiring System Wiring System Surface wiring Conduit wiring 1. Concealed 2. Surface Wiring in trunking Risers in communal installation Flameproof cable Cable Type General Use 1/C PVC/PVC cables with Temporary wiring; separate cpc; Low-cost housing 2/C PVC/PVC cables with cpc; 4/C armored cables 1/C PVC insulated cables Office, Private hosing; Factory; Plant room 1/C PVC insulated cables Sub-main/laternal main distribution Bare Cu/Al bars in trunking Armored cables in cable duct Mineral-insulated insulated cables Rising mains for internal power distribution system Petrol station, Flammable areas

49 3.2 Typical Schematic Wiring Diagram for Internal Power Distribution System

50 3.2 Internal Power Distribution System a) Basic Requirements b) High Voltage Distribution c) Mains d) Sub - Main e) Lateral Main f) Installation Methods of Cables

51 3.2 Internal Power Distribution System a) Basic Requirements 1 Every installation ti shall be divided id d into circuits it as necessary to avoid danger in the event of a fault, and to facilitate safe operation, inspection, testing and maintenance. Each circuit should be separately protected by an overcurrent protective device. Separate circuits shall be provided for parts of the installation ti which h need to be separately controlled in such a way that these circuits are not affected by failure of other circuits.

52 3.2 Internal Power Distribution System a) Basic Requirements 2 Protective ti devices of each circuit it should be clearly l labelled ll or identified so that the rating of the devices and circuits they protect can be easily recognized.

53 3.2 Internal Power Distribution System B) High Voltage Distribution-1 Although residential and the majority of commercial installations are adequately served from LV-intake or HV-intake intake-lv distribution, there are many industrial and some large commercial development projects require HV intake with extensive HV distribution system through the sites or buildings. For example, a hospital or an university with a large campus, a cross harbor tunnel with high-tension motors for ventilation fans, a very ;large commercial block and a large factory with several electrode boilers. For these, the power company provides the main supply point through its own switchgear complete with bulk metering, and the customer is then responsible for the installation of suitable high voltage switchgear, all cabling and the required number of on-site substations.

54 3.2 Internal Power Distribution System B) HV Ring Main Distribution system Just similar to the ring main system which used by power company in their 11kV network

55 3.2 Internal Power Distribution System Standard method of ring main connection mixed with radial feeding

56 3.2 Internal Power Distribution System B) Advantage of HV Ring Main Distribution system Even in the event of a cable fault on the ring, it is still possible to maintain or restore supply to all points by opening the switches on both sides of the fault. Additional outlets to the ring may be easily installed without shut downs. Greater maintenance facilities are available both on the ring feeder circuit it breakers and the RMUs. In additional, if the main HV switchboard is sectionalized and fed from more than one supplier s s substations, a ring main may be supplied from two different sections, thus improving security. Apart from fault conditions, it is also possible to operate a ring main in open mode as the preferred arrangement but, for whatever purpose it must be ensured that neither of the section is overload.

57 3.2 Internal Power Distribution c) Mains -1 System Consumer main switch shall be installed and connected immediately before the supply co. s meter. A common main switch shall be installed to control all the communal installation of the same consumer. The consumer main switch should incorporate: Means of isolation and switching Means of protection against overcurrent, and Means of protection against earth leakage.

58 3.2 Internal Power Distribution c) Mains -2 System The main switch or circuit breaker shall have a short- circuit breaking capacity of 40kA at low voltage. The characteristic ti of the main switch shall disconnect within 5 seconds during an earth fault. The switchboard shall incorporate Castell key interlock or other means to prevent the supply transformers operated in parallel. l All interconnecting i devices including the bus-section section switch shall be of 4- pole type with electrical l and mechanical interlock.

59 3.2 Internal Power Distribution c) Mains -3 System Where standby generator is installed, mechanically interlocked 4-pole changeover device shall be used for interconnection between the normal and standby source. A local switch shall be installed after a changeover device. Single phase consumer main switch shall be of double pole type. A schematic wiring diagram showing the main distribution ib ti system should be displayed d near the main switch with rating 100A or above.

60 3.2 Internal Power Distribution c) Mains -4 System Each consumer installation shall provided his own earthing system For 3 phase installation with main switch rating of 160A and above, C.T. operated meter shall be installed. Warning Notice: DANGER-ELECTRICITY, ELECTRICITY, UNAUTHORISED ENTRY PROHIBITED with Chinese translation shall be painted or engraved on plastic boards permanently fixed outside the door of switchrooms. Each character shall not less than 50mm high.

61 3.2 Internal Power Distribution c) Mains -5 System The mina earthing terminal of the installation should be bonded by a conductor of not less than 150mm 2 copper to the electricity supplier s s transformer earth or metallic sheaths of service cable.

62 3.2 Internal Power Distribution System c) LV Distribution-1 LV distribution exist in nearly all electrical installations. Nearly all LV distribution are in radial from. The greater the impedance of the cable from the secondary of the transformer to the LV switchboard, the less be the potential short-circuit current, and therefore these cables should not be larger than necessary. If two 1500kVA transformer were connected in parallel, then the potential fault current could be as much as 60MVA. As this exceeds the breaking capacity of most standard LV switchboards ( which is usually only 31 MVA, it would entail the installation of much more expensive switchboard or special high-reactance transformers, or split the LV main switchboards into two or more separate sections, each section being fed from a transformer not exceeding 1500kVA.

63 3.2 Internal Power Distribution c) LV Distribution-2 System The greater the impedance of the cable from the secondary of the transformer to the LV switchboard, the less be the potential short-circuit current, and therefore these cables should not be larger than necessary. If two 1500kVA transformer were connected in parallel, then the potential fault current could be as much as 60MVA. As this exceeds the breaking capacity of most standard LV switchboards ( which is usually only 31 MVA, it would entail the installation of much more expensive switchboard or special high-reactance transformers, or split the LV main switchboards into two or more separate sections, each section being fed from a transformer not exceeding 1500kVA.

64 3.2 Internal Power Distribution c) LV Distribution-3 System If sectionised is used in switchboard interlocked bus-section section switches should be provided

65 Typical ring main feeding six distribution boards

66 Radial distribution diagram for typical small commercial building meters on each floor if required

67 3.2 Internal Power Distribution C) Rising Mains-1 System 1) Cable, including prefabricated tee-off cable. The selection of cable as rising mains is usually limited by its current carrying capacity (CCC) The cable may be single-core insulted cable, or multi-core armoured cable. For single-core, p.v.c.-insulated. Non-armoured cable, the largest cross sectional area is 1000mm2 giving a CCC of 1200A. As a rule of thumb, when the demand exceeds 800A, busduct is preferred.

68 3.2 Internal Power Distribution c) Rising Mains-2 System 2) Insulated busduct (or busbar) system, including feeder type and plug-in type busduct. The rating of busduct could be up to 5000A or even higher. The provision of plug-in unit provide flexibility for tee-off at any location/ floor at anytime when demand required. The bus may be insulated conductor or bare conductors totally enclosed in continuous steel trunking.

69 3.2 Internal Power Distribution System c) Rising Mains-3 The following factors affect the selection of the type of rising main: Load assessment Load distribution Environmental conditions such as ambient temperature and humidity Heights of riser Maximum allowable voltage drop Fault level l Likelihood of alternation and future extension/ expansion being frequently required form, types and usage of the building whether the wiring is to be installed during the construction of a building, in a completed building, or as and extension system. Capital outlay required Planned duration of installation

70 3.2 Internal Power Distribution d) Sub-main -1 System Any building of more than four floors including the ground floor and designed for occupation of more than one consumer shall be provided with 3 phase electrical rising mains with 3 phase and neutral tee- off at each floor Type of rising mains could be one of the followings: Insulated conductors in trunking/ conduit; Armoured cables suitably supported; Bare conductors in trunking

71 3.2 Internal Power Distribution d) Sub-main -2 System Each riding mains installation shall be protected against overcurrent and earth leakage and shall be equipped with suitable means of isolation. For busbar installation having a rated capacity not exceeding 400A in each phase of a 3 phase 4 wire system, the associated neutral busbar should have a cross-sectional sectional area not less than the cross-sectional sectional area of the phase busbar.

72 3.2 Internal Power Distribution d) Sub-main -3 System Riser earthing conductor cto for multi-tenant tenant installations shall be installed and the minimum i size of riser earthing conductor is 70mm 2 copper. The loadings on 3 phase rising mains should be properly balanced. The neutral conductor should have a suitable current carrying capacity to cater for any imbalance or harmonic current.

73 3.2 Internal Power Distribution d) Sub-main -4 System The design of rising mains installation should be agreed by the electricity supplier. No part of the communal installation should pass through any individual consumers unit within the multi-consumer building. No cable, other than that for lift installation governed by BS5655, shall be run in lift shaft.

74 3.2 Internal Power Distribution e) Lateral Mains -1 System Adequate space for lateral mains and meter board wiring shall be provided in meter room. The loading on 3 phase lateral l mains should be balanced as far as practicable. An installation requiring more than 60A is required to be arranged to service a 3-phase supply. Appropriate correction factors shall be applied for determining the current carrying capacity of cables.

75 3.2 Internal Power Distribution e) Lateral Mains -2 System Distribution board, switchgear and busbar chamber should have phase identification. Where cables, conducts, ducts pass through h structural element such as floors and walls, the openings shall be sealed by appropriate fire resistant t materials. In addition, internal fire-resistant resistant barriers shall be provided to prevent the spread of fire. Segregation of low-voltage circuits, fire alarm circuits and dt telephone/ /t telecommunication ti circuits it shall llb be made when they run together.

76 3.2 Internal Power Distribution e) Lateral Mains -3 System Connection between the electricity supplier s s meter and the consumer s s main switch should be not less than 4mm 2 stranded copper conductor. The insulation and/ or sheath of the cables shall be removed for a distance of 150mm from the connection, and replaced if necessary by suitable heat-resisting insulation when connecting the cable to bare conductors/ busbar.

77 3.2 Internal Power Distribution e) Lateral Mains -4 System Warning notice DANGER DANGER in red legible letter with Chinese translation shall be displayed near each distribution board, Each character shall not less than 10mm high. Where an installation ti is connected to rising i mains, agreement should be obtained from the owner of rising mains if new current demand exceed that before. Moreover, prior approval from the power company should be obtained before any alteration work is carried out.

78 3.2 Internal Power Distribution System f) Installation methods of cables According to he CP for WP or IEE Wiring Regulations, cables can be in the following ways: Open or clipped direct Embedded direct in building,materials In conduit In trucking In free air, on cleats, brackets or ladder In building voids In trenched

79 3.2 Internal Power Distribution System What is a final circuit?

80 3.2 Internal Power Distribution System Definition of Final Circuit A circuit connected directly to current using equipment, or to a socket outlet or other outlet points for the connection of such equipment.

81 3.2 Internal Power Distribution System Final Circuit Typical Arrangement 1 IEE Reg states that an installation comprises more than one final circuit, each shall be connected to a separate way in a distribution board and that the wiring to each final circuit shall be electrically separate from each other.

82 3.2 Internal Power Distribution System Final Circuit Typical Arrangement 2 Typical Arrangement shall be : Two lighting circuits it to ensure the whole unit will not be in darkness if a fault occurs on one lighting circuit. Circuit for 5A or 15A socket outlet to be fed by an exclusive radial final circuit. it The maximum loading of each socket outlet shall be 5A or 15A respectively.

83 3.2 Internal Power Distribution System Final Circuit Typical Arrangement 3 Circuit for 13A socket outlets complying with BS1363. Separate circuit for each large current-using using appliance such as room cooler, cookre or kitchen appliance. Lighting circuits should be electrically separate from power circuits except that it may be connected to bell transformers or electric clocks.

84 3.3 Conduit Wiring System Type of Conduit Steel Conduit to BS 4568 : Part 1 A) Light duty type: plain and conduits Limited to use in dry situation; Unsuitable for bending Low degree of mechanical protection B) Heavy duty type: screwed-end end conduits Back enamel for internal use in dry situation; Hot-dip galvanized for external use in situation subject to dampness or water condensation; Good mechanical strength and electrical continuity.

85 3.3 Conduit Wiring System Type of Conduit Steel Conduit to BS 4568 : Part 1 C) Classification for protection: ti Class Protection Applied 1 Light protection both inside & outside 2 Medium protection both inside & outside 3 Medium heavy protection : inside as Class 2; Outside as Class 4 4 Heavy protection both inside & outside Example Priming paint Stoved enamel; Air-drying paint Stoved enamel inside; Sherardized outside Hot-dip zinc coating, sherardizing

86 3.3 Conduit Wiring System Type of Conduit Steel Conduit to BS 4568 : Part 1 D) Heavy duty hot-dip galvanized steel conduit system is the most common use system for surface conduit wiring and concealed conduit wiring. i Conduit is supplied in standard lengths of 4 meters and is manufactured in accordance with BS4568.

87 3.3 Conduit Wiring System Plastic conduits Type of Conduit To BS4607 Part 1 and 2; Characteristics : light, easily bend, less installation time, no water condensation, lower cost; Heavy duty PVC conduits can be concealed but CPC are required.

88 3.3 Conduit Wiring System Copper Conduits Type of Conduit High resistance to corrosion; Last for long time; Higher cost; Act as excellent circuit protective conductor (CPC)

89 3.3 Conduit Wiring System Aluminum Conduits Type of Conduit Light weight and lower cost; Not so good in mechanical protection Flexible Conduits To BS731 :Part1 Used for final connection to machinery; CPC are required.

90 3.3 Conduit Wiring System Sizing -1 EMSD s COP for the Electricity (Wiring) Regulations provides the following tables for ease of conduit sizing: Table A, B for 1/C PVC cables in a straight run 3m; Table C, D for 1/C PVC cable in conduit run > 3m. The conduit size is considered satisfactory if the conduit factor is equal to or exceeds the sum of the cable factors

91 3.3 Conduit Wiring System Sizing -2 Type of Conductor C.S.A. of Conductor (mm 2 ) Factor Solid Stranded Table A Cable factors for short straight runs

92 3.3 Conduit Wiring System Sizing of Conduit -3 Conduit Diameter (mm) Factor Table B Conduit factors for short straight runs

93 3.3 Conduit Wiring System Sizing -4 Type of Conductor C.S.A. of Conductor (mm2) Solid or Stranded Factor Table C Cable factors for long straight runs, or runs incorporating bends

94 3.3 Conduit Wiring System Sizing -5 Refer to Table A and B Table D Conduit factors for runs incorporating bends

95 3.3 Conduit Wiring System Example Sizing -6 In a conduit installation ti the length of run is 10m, assuming 2 right-angle bend. What is the conduit size to enclose four 2.5 mm 2 PVC cables? From Table C, factor for one 2.5mm 2 cable = 30 Therefore, four 2.5mm 2 cables = 4 x 30 = 120 From Table D, suitable conduit size with a factor of 141(>120) is 20mm. [10m Vs 2 bends, cable factor : 141]

96 33Tr 3.3 Trunking Wiring System - 1 Use in conditions where a considerable no. of cables are required in an installation or where cables are too large for drawing into conduits. Erection time is reduced (wiring is easier and quicker) Multi-compartment trunking provides circuit segregation.

97 33Tr 3.3 Trunking Wiring System - 2 Typical types of trunking A) Steel trunking for busbar rising mains. B) PVC skirting 3-compartment trunking for fitting-out wiring works where different category circuits such as Telephone cable, CABDS cable & power supply cable are to be installed in same run. C) Floor trunking to BS 4678 : Part 2 provides cabling to service boxes flushed with floor level (e.g. in open-plan plan office or dental room) D) Tap-on trunking in factory for internal power supply to machinery by plugging into the overhead trunking. E) Steel surface trunking for cable to BS 4678 : Part 1

98 33Tr 3.3 Trunking Wiring System - 3 Classification for protection against corrosion: Class 1 Electroplated l t zinc having a minimum i thickness of zinc coating of mm, inside and outside. Class 2 Class 3 As Class 1 but additional coating of stoved or air drying paint, applied at least to the external surface. Hot dip zinc coated steel.

99 33Si 3.3 Sizing ingoftr Trunking - 1 Type of Conductor C.S.A of Conductor (mm2) Factor Solid Stranded Table E Cable factors for trunking

100 33Si 3.3 Sizing ingoftr Trunking - 2 Dimension of Trunking (mm x mm) Factor 50 x x x x x x x x x x x Table F Factors for trunking

101 33Si 3.3 Sizing ingoftr Trunking - 3 Example What is the maximum no. of 10mm 2 PVC cables permitted in 50mm x 50mm trunking? From Table E, factor of 10mm 2 conductor = 36.3 From Table F, factor of 50 x 50mm trunking = 1037 Maximum no. of cable= = (say 28)

102 33D 3.3 Ducting - 1 It provided mechanical protection for cable run in the ground or under concreted floor. Types of ducting: Concrete ducts Steel underfloor ducts Fibre underfloor ducts Maximum m spacing factor is 35%. It should be securely fixed and protected against corrosion and mechanical damage.

103 33D 3.3 Ducting - 2 Entries to duct must be protected against the inflow of water. Cables installed in underground ducts shall have a metal sheath. Underfloor trunking should be fabricated with sheet steel of not less than 12mm thickness for compartment width up to 100mm, but at least mm thickness for compartment t width over 100mm. The minimum thickness of 1mm shall be used for the partitions i and connector material.

104 33S 3.3 Segregation of fci Circuits it - 1 1) Suitable segregation between enclosed circuits with different categories shall be provided in wiring. For example, a low voltage circuit shall be separated from an extra-low voltage circuit. 2) Types of Circuit: Category 1 Circuit Category 2 Circuit Category 3 Circuit Category 4 Circuit A circuit (other than a fire alarm or emergency lighting circuit) operation at low voltage and supplied directly from a main supply system With the exception of firm alarm and emergency lighting circuits, ant circuit for telecommunication (e.g. radio, telephone ) which is supplied form a safety source. A fire alarm circuit or an emergency lighting circuit. A high voltage circuit.

105 33S 3.3 Segregation of fci Circuits it - 2 3) Low Voltage circuit shall be segregated form extra-low voltage circuit. Extra-low voltage cables shall not be drawn into the same conduit or duct, or terminated in the same box or block as low voltage cables unless the former are insulated for the highest voltage present in the low voltage circuit. 4) Cables of fire alarm and emergency lighting circuits shall not in any circumstances be drawn into the same conduit duct or ducting of other cables.

106 33S 3.3 Segregation of fci Circuits it - 3 5) Electrical services shall not be installed with pipes or tubes of non-electrical services (e.g. air, gas, oil, or water) in the same conduit, ducting or trunking. This requirement does not apply where the various services are under common supervision and it is confirmed that no mutual detrimental influence can occur. 6) For cables of category 1,2,3 circuits that are installed without enclosure or underground, a minimum separation of 50mm should be provided between different category circuits or alternatively at least 25mm separation with slabs of concrete inserted between the circuits and the shortest path round the concrete should exceed 75mm.

107 33S 3.3 Segregation of fci Circuits it - 4 7) Insulated bridge of at least 6mm thick should be used for separation of surface wiring of Category 1,2,3 circuit running across each other. The bridge should overlap the cables by at least 25mm on either side of point of crossing. 8) For cables of Category 4 circuit that are installed without enclosure or underground, a minimum separation of 300mm should be provided between Categories or alternatively a reduced separation with 50mm thick slabs of concrete inserted between the circuits and the shortest path round the concrete should exceed 180mm.

108 3.3 Standard Circuit for 13A Socket Outlet The development of the BS1363 plug and socket system and the associated concept of ring circuit have made possible the provision of large numbers of socket outlets at lower installation costs. All ring circuits shall be run in the form of a ring looping into the terminals of the socket outlets and returning to same protective device. The circuit protection conductor (cpc cpc) should also be run in a ring unless it is provided in form of metallic conduit or trunking. Typical standard circuits are tabulated as follows: Type of circuit Overcurrent Protective Device Rating Type Minimum Copper PVC insulated cable Max. Floor Area Ring 30A Any 2.5mm 2 100m 2 Radial 30A HRC fuse; Circuit Breaker 4mm 2 50m 2 Radial 30A Any 2.5mm 2 20m 2

109 Q&A