Electrical Services

Provide at least the following electrical services in Schools:

• Main Switchboard. (MSB)
• Distribution boards (EDBs), with RCD protection, controls, circuit breakers and labels.
• Underground reticulation for submains, consumers mains, sub-circuit,  communications and control cabling.
• Power installation.
• Lighting installations.
• Fan, heating and period bell installation.
• Structured cabling system (SCS) to enable the school administration and management software, learning computer networks, Audiovisual, Public Address and Telephone systems to be reticulated throughout the school.

Provide the additional electrical services in schools where required:

• Electronic security, Including CCTV or conduits for installation at a later date, as nominated for a particular project.
• Energy conservation devices or equipment.
• P.A.B.X. or Key system.
• Fire Detection (dry fire).

The completed system is to meet the regulatory requirements of the following:

• National Construction Code (NCC), Building Code of Australia (BCA)
• Australian Standards AS/NZS 3000
• Relevant Power Supply Authority requirements. 

Ensure that permanent electrical supply can be made available.

Engage an Accredited Service Provider Designer (ASP/Level3) to prepare the Application for Connection of Load for the local electricity Distribution Network Service Provider (DNSP) as soon as practicable.

To determine the availability of supply the Accredited Service Provider Designer will require information on what is proposed, including:

• The location of the project
• The extent of the works
• The anticipated maximum demand based on new or refurbishment works including the deduction for any load being removed

The following information will also be required:

• the proposed method of supply
• the preferred sub-station location, if required, or point of attachment
• fault level at point of supply
• any other requirements of the DNSP
• and any additional information likely to influence their deliberations

Substation Location

The preferred location for the substation is at the site boundary to the road reserve (away from school play ground).  There may be situations where this may not be the most cost effective solution:

• where it results in a long (and costly) low voltage service/consumers mains;
• if the DNSP nominates a maximum length for the service mains.

Alternate substation locations need to be discussed with DoE to ensure that they are appropriate and do not pose a risk to the school community. Generally, locate substations adjacent to the school car park as this allows access for maintenance and locates the substation away from play areas. 24 hour access to the substation will be required,  any gates must allow dual key access.

With deregulation of the electricity industry provision of electricity supply is divided into two categories:

• Monopoly: costs of work that must be provided by the DNSP.  These include the analysis of the network, providing information for the design process, inspection fees and commissioning fees.
• Contestable: this is normally undertaken by an Accredited Network Service Provider (ASP) – Level 3, registered with the NSW Department of Trade and Investment, [Refer to their website for a list of certified designers].  This includes both the design of the system and the construction of the works.

Monopoly work is to commence as soon as possible in the design phase.  The electrical project officer submits forms on behalf of DoE (as the developer) to the DNSP along with payment of any fees.

Contestable work (both design and construction):

A Level 3 Accredited Network Service Provider should be engaged as part of the design process and the design documents should be included with the tender documents.

Construction work should be included as part of the contract works. Construction work should be based on advice as received from the DNSP.  The Contractor is to provide the contestable services using an Accredited Network Service Provider:

A Level 1 ASP will be required to extend the overhead or underground network to reach the school property, or if the capacity of the existing network needs to be increased.  This may include high and low voltage works, substations and metering.

A Level 2 ASP will be required to:

• install, repair or maintain the overhead or underground service lines between the electrical wiring on the school premises and the electricity network
• install electricity metering equipment
• connect school service lines to the network and make the connection 'live'
• disconnect school premises from the network.

If a sub-station and/or HV cable easement is required, notify the client in writing so that Forms from the DSNP may be signed agreeing to provide an easement.

Where a site is to be serviced from a street pole adjacent to the boundary, request permission to utilise the electricity distributor’s distribution pole. This is preferable to installing an additional consumer’s pole on the school property. Use a pillar box with protective device at the property boundary as the point of supply.

61.03.1  EMERGENCY POWER SUPPLY TO SITE

A quick connection point for emergency backup portable generators is required for all projects in new and refurbished schools that are identified as at risk of power loss due to bushfire, flood, adverse weather events, and schools identified as a Community Evacuation Facility (CEF).     

The MSB design shall provide a quick connection point in the form of a Power Lock or Busbar Cable connection facility to a temporary mobile generator which may be installed in the event of a prolonged power supply failure.  The connection facility and generator capacity shall provide for full operation of the school.

Location of temporary portable generator

The portable generator may be positioned up to 200m maximum from the MSB without voltage drop. 

Truck Access

Design is to allow for vehicle access to the MSB (including trucks for delivery of the generator and refuelling), space provision for the portable generator and potential noise impacts to learning spaces and adjacent properties caused by operation. 

Delivery: Access for large trucks, refuelling tanker and crane is required. A generator is delivered to site on a trailer. It can be left on the parked trailer, or lifted off the trailer with a side loader and placed on the ground, or lifted off the trailer by a mobile crane and placed closer to the MSB.   A typical containerised 500kVA portable generator is 6m long x 2.4m wide x 2.6 high, Weight with fuel 10800kg, 1289 litre fuel tank capacity.

Generator: The Generator will need to be installed in a level location cleared of vegetation and any other obstruction to the operation of the generator and ideally no overhanging foliage. In some instances there may be a requirement to house a more permanent generator for a longer period. In this instance, provision must be made for servicing of the generator to ensure its ongoing operation.  Location of the generator should not impact universal access to the site. Any connection cables from the generator to the MSB must be suitably secured to not provide a trip hazard.

Refuelling: Typically the generator supplier refuels the inbuilt tank on the generator. Fuel consumption and generator use is monitored remotely. A diesel tanker requires access to refill the generator when needed. If operating at max capacity 8 hrs/day – the generator will typically require to be refilled every 2nd day. In preparation for refuelling, sandbags should be installed as a barrier around the generator to ensure that any diesel spills during refuelling are contained.

Vehicle Safety: Allow for safe manoeuvring and parking of the diesel fuel tanker, with no safety risk to students and adult users of the school or the public is required in assessing location of the generator.  Provide bollards where truck access is adjacent to buildings or student play and circulation areas.

Acoustic impact on school operation

Noise generated by the portable generator has potential impact on school teaching operations and adjacent residential areas.  An Acoustic Report evaluation of acoustic impact on learning spaces, library, admin and staff is to be considered in assessing the location of the generator. 

Ensure effective coordination between disciplines.

Organise the information from all sources to meet a set program.

The design of the electricity supply system and the selection of equipment is to be undertaken based on a Whole of Life approach to ensure that the completed system provides:

• Value for Money
• fit for purpose
• long term reliability
• minimal maintenance requirements
• low maintenance costs

During the design process, and by the Developed Design stage:

• Locate the main switchboard (MSB) and electrical distribution boards (EDBs) in consultation with the Architect, taking into consideration the point of supply and consumers mains length.
• Design cable reticulation system (including pits and other items involving other disciplines).
• Design switchboards, determine fault level and verify switchboard cupboard access and sizes, etc. Reassess switchboard locations if necessary.
• Develop an energy usage statement.
• Prepare schematic diagrams for the structured cabling system (SCS) including the various systems attached to it.
• Co-ordinate power to other services including architectural disciplines
• Prepare cost estimates as required.
• Develop Electronic Security layout, in conjunction with the DoE Security Unit where a security system is to be included.

Contact the local Telstra District office regarding specific requirements especially earthing details for communications system.

61.07.01 Secondary Schools

House the MSB in a separate main switchroom with the following features:

• External access for meter reading, out-of-hours operations etc.
• 2 hour (120/120/120) fire separation, including doors, from the remainder of the building, except where there is a greater requirement by AS or BCA
• Depth not less than 1.8m
• One straight wall of minimum length 3.0m, for MSB length up to 2.4m; or
• One straight wall of minimum length 4.2m, for MSB length from 2.4 to 3.6m
• Where MSB length is greater than 3.0m; or MSB prospective short-circuit current is 15kA or greater; or MSB is supplied by a circuit with a nominal capacity equal to or greater than 800 Amps per phase; or MSB frontal clearance is less than 3.0m; then provide two access doors, spaced well apart for adequate alternative egress paths from room
• Floor level 75 mm above corridor and adjacent rooms, to minimise danger of water entering cabling pits due to hosing down floors in adjacent areas, flash-flooding, etc.
• Artificially illuminated, to a minimum level of 160 lux. Position the luminaires to avoid casting shadows into the switchboard when switchboard covers are removed and not above equipment to enable safe access to lighting for maintenance
• Provide one double socket outlets for general maintenance use
• Provide natural ventilation to an adjoining area to remove generated heat. Ventilation should be to outside and all ventilation openings must retain the fire integrity of the room
• Cable pit under the MSB to facilitate the entry of the consumer’s mains and submains may be required                           

Refer to DG / ELECTRICAL SERVICES / CABLE DRAW-IN PITS

A typical drawing detailing the pit dimensions and architectural, structural & hydraulics requirements of the pit is included in the Specification Guide

Refer to DG DRAWINGS / MAIN SWITCHBOARD CUPBOARD PIT

• Switchroom doors should:
  • Be minimum 850 x 2100 (single) clear and/or 1600 x 2100 (double)  clear
  • Open outwards and be operable from within the room without the use of a key or tool
  • Be lockable  with a PWD “E” Keys
  • Have facility to be held in the open position without blocking passageways or pathways
  • Doors which include access to electricity metering must have dual locking function for local electricity distribution network service provider and PWD “E” keys
  • Provide work-as-executed site reticulation drawing on A3 laminated sheet within main switch room or cupboard

61.07.02 Primary Schools
 

Basic floor plans, such as the Component Design Range, include main switch rooms, and the details show the minimum size of these rooms. 

Generally comply with secondary school switchroom requirements.            

Refer DG / ELECTRICAL SERVICES / ROOMS AND CUPBOARDS FOR MSB / SECONDARY SCHOOLS

There may be situations where only a cupboard may be required for the main switchboard rather than a switchroom.  Provide a cupboard with the following features:

• External access for meter reading, out-of-hours operations etc.
• Minimum clear internal dimensions 2.0W x 0.7D x 2.5H
• Lockable doors with PWD “E” Keys, with a minimum door opening of 1.7 wide x 2.1 high
• 2 hour (120/120/120) fire separation, including doors, from the remainder of the building, except where there is a greater requirement by Code or BCA
• One double socket outlet for general maintenance use and future use
• To be in a sheltered location such as a covered entry where there is a covered area extending no less than 1000mm in front of the doors to allow all-weather access to the main switchboard
• Depending upon cable sizes being installed, a cable pit may be required under the main switchboard or alternatively externally to the main switchroom or cupboard.                
  Refer to SG DRAWINGS / DS61/2

If meters are located in a separate cupboard adjacent to the MSB cupboard, the meter cupboard size should be a minimum 1.2m x 1.2m x 0.6m deep, subject to approval by the local electricity Distribution Network Service Provider. Provide a pair of cupboard doors the same size as the cupboard.

If the meter and MSB are located in the same cupboard, the minimum clear internal dimensions are to be either (2.6W x 0.7D x 2.5H) or (2.0W x 1.5D x 2.5H preferred option).

61.09.01 General
 

In every new building, and wherever possible in old buildings, provide lockable cupboards for EDBs.  Where this is not possible EDBs need a lockable door. Locate cupboards so that access is available only directly from general circulation areas. It is not acceptable to walk through classrooms etc. to gain access to EDBs, or to locate them in storerooms.

These cupboards should have the following features:

• Minimum clear width dimensions to suit the electrical distribution board (including spare capacity)  x 2.1metres  high.  Allow space on either space of the board to facilitate servicing
• Lockable doors with PWD “E” Keys
• Outward opening doors, the full width of the cupboard, 180 degrees swing with latches to hold the doors in this position. In the open position doors must not obstruct passageways
• Unimpeded access to the EDB from the floor to door head height with cupboard doors open
• 1 hour (60/60/60) fire separation, including doors, from the remainder of the building, except where there is a greater requirement by AS or BCA
• Provide smoke seals on cupboard doors where cupboards is within path of egress where required by AS or BCA

Illuminate all EDBs to minimum 160 lux.  Install lighting and a double socket outlet within each cupboard or switchroom.

Generally, submains may be run underground, or within the building structure (on cable tray, ladder or troughing). During planning, take into account relevant site features and choose routes that will not affect future building development.

Submains are to be copper conductor cables. Aluminium conductor cables are not to be used.

Provide spare capacity as stated.

Refer DG / ELECTRICAL SERVICES / SPARE CAPACITY

Conduit diameters to be sized in accordance with the relevant AS and general installation practices.

The follow space factors are recommended.

0-10 metres            50% space factor for single cables

                    40% space factor for multiple cables

10-30 metres          33% space factor

30+ metres            25% space factor

Each 90 degree change of direction is to be considered equivalent to 10 metres of conduit run.

Wherever practicable, run other services in the same trench as the electrical cables with due separation of services, both for safety and to avoid interference.  This limits excavation costs and avoids a network of underground services, which could interfere with future site development.

Refer to DG / COMMUNICATIONS

Underground cable draw-in pits should be installed in suitable locations to minimise damage during initial installation or subsequent replacement of cables.  However, minimise the use of pits as they are expensive, lead to drainage and insulation problems and are subject to damage.

Provide pits under large switchboards to allow entry of large cables and to facilitate turning these cables to enter the switchboard.  Pits are to be drained to the stormwater system via a valve that will prevent surcharging.  In addition, the floor of each cupboard or switchroom containing a pit must drain to the outside of the building.

Acceptable pits include:

• moulded fibre cement (communications type)
• Polymer concrete
• special purpose brick or concrete pits.

Any electrical/communications pit should be:

• dimensioned by the Electrical Engineer
• constructed with adequate drainage and in accordance with the NATSPEC documents.

Care must be taken on a sloping site with conduits entering pits, to prevent the ingress of water via the pits and conduits into switchrooms and EDB cupboards. Effectively seal these conduits at both ends.

Consult with the Architect and Hydraulic Engineer to ensure drainage provisions are made and the pit is included in the Architectural documents.

Pits are not to be used to join cables.

Communication services and security services must be supplied with their own separate pits.

Where the total connected electrical load exceeds 100 amps per phase use one of the following options:

• Custom-built MSB
• A combination of custom-built and proprietary enclosures, with each section controlled by a main switch

The main control on all MSBs shall be a fault make and load break switch, which will be on the load side of the Service Protection Device (SPD) for MSB local isolation. Generally house the MSB in a switch room, external MSB is not to be installed unless approved by the Electrical Engineer representing DoE. 

Refer to DG / ELECTRICAL SERVICES / ROOMS AND CUPBOARDS FOR MSB'S

Include electricity-metering requirements as described elsewhere in the Design Guide and as acceptable to the local electricity DNSP.

Separate metering for the canteen or FSU is required, so provide separate metering within the MSB along with separate submains and an EDB for the canteen or FSU.     

Include metering current transformers and potential fuses within the MSB, but the meter/s may be on a separate panel adjacent to the MSB where it is in a switchroom or switchboard cupboard. Consider an option of locating meter panels externally to the MSB Switchroom/Cupboard, complying with the DNSP’s requirements, for both modified and new main switchboards.

Where the rating of consumer’s mains exceeds 100 amps per phase, include a three-phase digital power meter in the MSB along with associated current transformers and potential fuses.  Indication is required of:

• current in each phase
• 15-minute maximum demand in amps in each phase
• three line to line voltages
• line to neutral voltage of each phase.

Provide a machine engraved label adjacent to meter reading:

METER TO BE RESET BY AUTHORISED PERSONNEL ONLY – BEFORE RESETTING ENTER MAXIMUM DEMAND READINGS IN SCHEDULE.

Provide surge protection devices at the Main Switchboard and for communications equipment as recommended by AS1768.

Provide a point of entry 3 phase shunt diverter for the incoming 415 volt supply. The surge protection shall have an indicator showing surges received.

Point of entry protection shall be mounted within the main switchboard to the detailed recommendations of supplier/manufacturer.

Spare spaces for future circuits - specify to a minimum total of:

• 25% of existing spaces or 6 spare spaces for 3 Phase Circuit Breakers, whichever is greater; plus
• The spare spaces required for known future buildings in other stages.
• Allowance to be made within the MSB’s for a future Lift/essential services control.
• Busbars are required from the Service/consumers mains connection point to the line side of all circuit breakers.
• Provide minimum 20% spare capacity within the busbars for future loads.

Where high numbers of spare spaces for future large circuits are involved (eg. 5 controls greater than 160 amps), specify the switchboard and switchroom space to be suitable for addition of future extension cubicle/s. Provide busbars sized for the anticipated additional load.

Long cable runs are common in schools and, as required by AS/NZS 3000, cable selection needs to address factors additional to current carrying capacity.

One of the factors that must be considered is voltage drop.  Calculate voltage drop using maximum demand determined from the process further outlined. In the case of final subcircuits, consider the circuit carrying a current equal to the rating of the circuit protective device. Refer to Wiring Rules AS3000 for voltage drop permissible where there is a direct connection to a substation.

Note that voltage drop must be considered from the point of supply to the last item on any final subcircuit.  The permissible voltage drop is the sum of the individual drops in (a) the service/consumers mains, (b) any submain/s and (c) each final subcircuit.  The proportioning of the voltage drop across (a), (b) and (c) will vary from site to site to achieve an economic solution.

As a general rule, limit final subcircuit length to servicing loads not more than 25m radius from the EDB. In a heavily loaded building such Science or Materials Technology, the 25m radius criterion may need reducing.  There may, however, be other situations where it is economic to slightly increase final subcircuit cable lengths with a corresponding reduction in the permissible submain/s voltage drop from the originating power source to the EDB (e.g if it avoids duplicating an EDB).

Ensure that the maximum voltage drop allowed by relevant AS will not be exceeded at any point in the installation in the future when the spare capacity is used and future buildings are added. In terms of the future, make due allowance for voltage drop in submains to future buildings, and base the calculation on final subcircuits in future being to the 25m radius criterion.

Cables are to be continuous from the point of supply to the MSB, from the MSB to EDBs and between EDBs.  Cables are not to be joined.  

Embedded conduits displace their own volume in concrete and, depending on their location, number and spacing, could affect the structural performance of a slab or column.

A high concentration of conduits occurs at switchroom and switchboard cupboards.

Exercise caution with embedded conduits in areas where slab penetrations will occur, e.g.:

• Fixing of machinery in Materials Technology spaces to the floor;
• Fixing of timber sprung floors to the slab in the Multi-Purpose Centre.

In the latter case, run conduits around the floor slab, not across it.

All conduit runs in slab and penetrations to structural elements must be approved by the structural engineer prior to installation.

The preliminary maximum demand may be used to enable negotiations with the electricity distributor to begin early in the design process.  However, for more accuracy, use this section in conjunction with requirements of the relevant AS, particularly when detail layouts are available.                                    

Refer to DG / ELECTRICAL SERVICES / PERMANENT SUPPLY TO SITE

For buildings (particularly demountables) being placed on site at the completion of the main project, calculate maximum demand by considering electrical heating figures.   

Socket outlets are not intended to be used in schools for the connection of portable electric space heating or cooling appliances. Permanently installed heating is provided, as is cooling equipment where necessitated by the climate conditions. Interpretation of this needs to be agreed to by the relevant authorities for each site.

Calculate the maximum demand of each building to be constructed or refurbished using AS 3000.

For refurbished buildings, the maximum demand calculation must also deduct the electrical loads being removed or being replaced.

Determine the maximum demand of existing buildings that are being connected to the reticulation system by calculation or by installing temporary data loggers within the switchboards to record the demand for a period of minimum 4-weeks.

Design the reticulation to supply all buildings, include those planned for construction in the future and for planned demountable buildings.

61.21.01 Calculate the final maximum demand using Appendix C of AS/ NZS 3000.

Refer AS/NZS3000

Provide spare capacity in service/consumer mains, submains and distribution boards as follows:

61.23.01 Service/Consumers Mains And Submains

• Allow spare capacity in the service/consumers mains of 15% of the total loadings calculated above or 30A/phase, whichever is the greater.
• Allow spare capacity in each submain of 20% of the total loadings calculated above or 25A/phase, whichever is the greater.
• Allow spare capacity in each submain for future addition of Air Conditioning, with allowances of 60VA/m² of occupied area for air conditioning.

Do not install the cables for future buildings. Install properly sized conduits with draw cords from the appropriate EDB to a point 1m clear of hard surfaces.

61.23.02 Distribution Boards

• Size all EDBs to cater for the total reticulation found in DG / ELECTRICAL SERVICES / CALCULATION OF FINAL MAXIMUM DEMAND. This includes fault-levels.
• Allow sufficient space on the board to feed the new buildings; then add the expansion figures detailed in earlier sections. 

Provide spaces only, not sub-main controls, for future buildings.