Industrial and CommercialPower Systems

Dr. Mohammad SALAY NADERIRoom EE305

Ph. 9385-5262 Email: m.salaynaderi@unsw.edu.au

The University of New South Wales

School of Electrical Engineeringand Telecommunications

“Building” = Any industrial and commercial installations with substantial internal electrical distribution infrastructure, including:

Commercial high-rise buildings,

Large campuses and factory sites

with electrical supply at up to 11 kV and with possibility of both 11 kV and extensive 415V distribution systems.

Westpac Place

headquarter of Westpac bank in Sydney CBD91,000 sqm, 166m tallhouse 5000 peoplecompleted in 2005cost $627 millions

Westpac Place

commercial office building with retail area 3 substations total load = 10MVA 32 floors with 6 basement levels ~19000 light fittings, mostly fluorescent office equipment (computers, printers, photocopiers etc) air conditioning

.

Petronas Towers

Kuala Lumpur, Malaysia completion: 1998 twin commercial office towers 452m, world tallest then. 88 stories each. Joined half-

way up by 58m long sky bridge 436,000m2 of floor space

Burj Dubai (Khalifa)

The tallest structure in the world (818m).Opening date: 4 January 2010

160 floors, 334,000 m2.Designed to house 35,000 peopleEstimated peak demand = 36 MVA

New teaching building – University of Western Sydney$25 millions project, completed 2006Estimated maximum demand = 550 kVA

Port Kembla Steelworks (Wollongong)Hot strip mill

Syllabus

Electrical supply, regulatory aspects Switchboard design and operation (HV and LV) cabling systems Distribution transformers and switchgear Protection of electrical systems (over-current and surge protection),

lightning protection Electrical lighting systems Equipment operation, condition monitoring of major plant Energy efficiency Power quality and effects of voltage and current harmonics Industrial heating Earthing, electrical safety (personnel protection and fire protection) Effects of 50Hz magnetic fields in building and industrial sites

Relevant materials

Lecture notes Standards

AS/NZS 3000:2007 Wiring Rules Other AS standards IEEE Gray Book

Service and Installation Rules Various books Publications from manufacturers

AS/NZS 3000:2007Electrical Installationsknown as the Australian/New Zealand Wiring Rules

Scope:

“Set out requirements for design, construction and verification of electrical installations, including selection and installation of electrical equipment forming part of such electrical installations.

Requirements are intended to protect persons, and property from electric shock, fire and physical injury hazards that may arise from an electrical installation.”

Check also:

AS/NZS 3008:1.1:1998 Electrical installations – Selection of cables – Cables for AC up to 0.6/1kV

AS/NZS 3017:2007 Electrical installations – Verification guidelines. Provide methods for verifying that electrical installations comply with safety requirements

AS/NZS 3019:2007 Electrical installations – Periodic verification

AS/NZS 4836:2001 Safe working on low-voltage electrical installations

AS/NZS 3018:2001 Electrical installations – Domestic installations

Assessments

Class tests (week 5 and 10) closed book worth 10% each

Group project (due week 12) form your own group of up to 3 worth 10%

Final exam closed book 70% of total marks

Requirements on electrical supply systems:

more energy efficient, better energy management safety (including personnel safety, fire and equipment safety) adequate power quality (harmonics and over-voltages) able to handle modern information technology systems compliant with EMC and EMI regulations (electrical systems )

EMC: Electromagnetic Compatibility EMI: Electro Magnetic Interference

provide monitoring systems to assess condition of installation

1. Overview

Means and requirements on an electrical supply system

May include following features:

Specified voltage levels Limited harmonic content (quality of supply) Method of supply Safety of supply Reliability of supply Maintenance Electrical protection Back-up supply (UPS) DC supply

2. Power Requirements

Power demands must be known before details of supply configuration can be determined and designed.

Obtained by estimation of maximum demand for electrical power. This has 3 components:

manufacturing equipment requirements large motors, arc furnaces, assembly lines, ovens, presses

general fixed wiring infrastructure requirements lighting, heating, lifts

general free-standing mobile equipment supply (GPOs = General Power Outlets)

Maximum demand assessment

calculation using Appendix C (Wiring Rules) to determine demand for domestic and commercial type loads.

when exact load details are unknown, use an estimate technique called ‘After Diversity Maximum Demand’ (ADMD)Based on results from similar installations, typical load

density values (VA/m2) are derived for different types of floor area usage.

Data available for commercial (e.g. offices, shopping centers, hotels, theatres) and light industrial premises

For general estimate, the following gives typical power demand requirements per unit area of floor space:

EnergyAustraliaNS0112 Design standardsfor industrial/commercialdevelopments

In estimation of maximum demand, should make allowance for future growth in power usage. Typically:

residential premises, 10% fully air-cond offices, 15-20% commercial premises, 20-25% shopping centres, light/medium industrial, 25%

Include provision for possible additional switchboard circuits.

Also include in initial consideration selection of transformer capacity and cable sizes for feeder circuits and reticulation of power.

Once incoming supply is specified, requirements can then be detailed for: incoming cable rating main transformer capacity substation size and capacity switchboard size and capacity.

Only when this final design is completed can fault level calculations be performed to determine fuse and switchgear ratings and other protection needs.

Calculation of maximum demandAppendix C AS/NZS 3000:2007

domestic installation (use Table C1) singlemultiple

non-domestic installation (use Table C2) residential type (e.g. hotel, hospital)others (e.g. factory, shop, business office)

Table C1 (AS3000:2007)

Table C1(cont.)

Table C1(cont.)

TableC2

TableC2

(cont.)

Example 1:

Note: Assume supply voltage and equipment rating of 230V

Example 2:

3. Means & Requirementsof Electrical Supply

3.1 Voltage levels3.2 Quality of supply3.3 Method of supply3.4 Type of supply connection3.5 Safety3.6 Reliability of supply3.7 Maintenance3.8 Backup supply3.9 DC supply

3.1 Voltage levels

High voltage:11 kV, 3-phase supply[by cable or overhead line]

Low voltage:(a) 230/400V, 3-phase, 4-wire system(b) single-phase, 230V, 2-wire system[underground/aerial cable, or overhead line]

Supply voltage levels available from electricity distributors for use in commercial and industrial locations in urban areas:

Once power demand and supply requirements determined (by system designer), then contact appropriate electricity distributor. They have additional requirements which must be complied with before they connect supply from their network to the site, e.g. “EnergyAustralia ES1 Customer Connection Information”

Also requirements on a state-wide basis which applies to all distributors in that state, e.g “NSW Service and Installation Rules”.

New regulations allow contestability among utilities in the supply of electricity to consumers. Electricity provider may be different from the actual electricity distributor.

Accredited Service Provider = an entity accredited by the Department of Fair Trading in accordance with the Electricity Supply Regulation 2001.

Three levels:

Level 1: Construction of Transmission and Distribution works. High and low voltage overhead and underground reticulation, including substations

Level 2: Service cables and metering installation. Install underground and overhead service cables being the interface between the network and customer’s premise, and include metering services.

Level 3: Design. Design and preparation of plans for the proposed overhead/underground distribution network including street lighting.

The electricity distributor is of course an accredited Level 1, 2, 3 service provider.

What is an energy distributor?

Distributors own and manage high and low voltage network of 'poles', 'wires' or ‘pipes’ that deliver electricity or gas to your home or business. They are responsible for the quality and reliability of your energy service.

How is that different to an energy retailer?

Energy retailer on the other hand sells you the electricity and gas for your home or business and bills you for what you use.

Energy Retailers for NSW: the three distributors, AGL, Origin Energy, True Energy, etc. Find more information from NSW Department of Water and Energy web site.

Electricity distributors for NSW

Electricity distributors for NSW

For NSW state, three distributors: EnergyAustralia, Integral Energy, Country Energy

Distributor for UNSW is EnergyAustralia

RailCorp is the distributor for installations on railway land within the railway 1500V DC electrified track area.

CountryEnergy covers more than three quarters of NSW and parts of southern Queensland. It includes more than 200,000 km of power lines and 1.4 million poles

EnergyAustralia

Electricity distributor for Sydney, Central Coast and Hunter regions of NSW

Distributes ~ 25,000 GWh of electricity annually, to 1.4 million customers through: More than 1000km of above ground 132kV HV cable Almost 500km of underground 132kV HV cable More than 400km of 66kV cables. More than 2200km of 33kV cables.

Integral Energy

Network area covers:

Sydney’s Greater West, the Southern Highlands, and the Illawarra.

Limits on connection and operation of equipment

Equipment in an installation can cause:

Excessive voltage fluctuations (eg welding machines, starting motors)

Excessive distortion (eg. rectifiers, frequency converters)

Interference with frequency load control system

Customers required to take corrective actions.

Limit on load current changeNSW SIR Sect. 1.10.2.3

Equipment may be restricted by the change in current that occurs when switching on/off or between operation settings.

Limit on motorsNSW SIR Sect. 1.10.2.4

Starting current must not cause voltage dip to exceed 5% for 20ms.

Balancing of load (for three-phase supply)NSW SIR Sect. 1.10.3

maximum current in one phase is no more than 25A above current in any other phase

total current in neutral conductor not to exceed highest simultaneous current in any active conductor.

Protection from prospective short circuit currentsNSW SIR Sect. 1.10.4

maximum current that flows under short-circuit fault is a function of impedance of supply source and cables.

for 230/400V systems and at connection point for service up to 400A:

suburban residential areas: 10kA commercial and industrial areas: 25kA on railway land (RailCorp): 6kA

Power factor

The power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit, and is a dimensionless number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).

Real power is the capacity of the circuit for performing work in a particular time.

Apparent power is the product of the current and voltage of the circuit.

Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power will be greater than the real power.

Power factor

In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred.

The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment.

Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor.

Power factor

Linear loads with low power factor (such as induction motors) can be corrected with a passive network of capacitors or inductors.

Non-linear loads, such as rectifiers, distort the current drawn from the system. In such cases, active or passive power factor correction may be used to counteract the distortion and raise the power factor.

The devices for correction of the power factor may be at a central substation, spread out over a distribution system, or built into power-consuming equipment.

Power factor correction / Capacitor installationNSW SIR Sect. 1.10.11

• Industrial/commercial loads require significant reactive power (kVars), e.g. motors, furnaces, electric discharge lighting

• must maintain p.f. not less than 0.9 lagging

• No restriction on where to install p.f. correction equipment in the circuit

• More details in Section 6 of NSW SIR (Capacitor installations).

Initial designed maximum load on any distributor must not exceed 75% of the distributor’s nominal rating. This is to provide margin for load growth and paralleling requirement.

EnergyAustralia requires:

3.2 Quality of supply

An important consideration because:

increasing use of power electronics has introduced a higher harmonic level into supply

much of equipment now in use (IT) is more susceptible to voltage variation, transient over-voltages and harmonics.

Quality of supply based on consideration of:

frequency of AC supply

voltage level fluctuation

voltage waveform distortion (harmonics)

interference with communications and control equipment

transient over-voltages

3.3 Method of supply Up to ~200 kVA in demand:

incoming supply would commonly be by a low voltage 3-phase, 415/240V, supply obtained directly from distributor’s LV mains

by either overhead or underground connection.

NSW SIR 2009

may need 3-phase for 3-phase loads

Up to 3000 kVA:

utility-owned transformer(s) installed in utility-ownedand maintained substation, located on consumer’s premises.

supply to consumer’s electrical system (at point of attachment to consumer’s terminals) would be at low voltage (415/240V) from secondary of transformer.

transformers: 11kV/415V and 750 – 1000 kVA in power rating.

oil-filled transformers if installed outdoors or dry-type if inside a building. Dry-type units reduce fire hazards within buildings.

Greater than 3000 kVA:

supply to consumer would be at high voltage, most likely 11 kV

consumer provides and owns HV substation and switchgear installation

consumer handles maintenance and switching operations associated with substation

consumer required to employ electrical staff or contractors adequately trained in maintenance and operation of high voltage equipment .

3.4 Type of supply connection

high or low voltage from distributor’s supply, by either: aerial lines (with either bare, covered or bundled conductors) underground cables (either 3 single phase or 1 three-phase cable)

low voltage supply from utility on-site substation, by means of any of: low voltage aerial lines low voltage underground cables low voltage busbar trunking system (> 2000A per phase)

dedicated HV line from utility HV substation. By either overhead line or underground cable, depending on location and requirements.

Supply from overhead distribution mains.Ref.: NSW Service and Installation Rules

Supply from overhead distribution mains.Ref.: NSW Service and Installation Rules

Supply from underground distribution mains.Ref.: NSW Service and Installation Rules

EnergyAustralia supplies 11kV from Randwick (14MVA) and Clovelly (8MVA) zone substations.

Two points of supply, separate Campus network: owned and operated by university, 11kV

underground cables, 20 substations, split into three rings. Mid and lower campus rings fed from Randwick zone; Upper campus

ring fed from Clovelly zone In event of failure of one zone substation, entire campus can be fed

from other zone substation (at reduced capacity).

UNSW

3.5 Safety :

personnel safety

installation required adherence to all relevant Codes and Standards.

electrical hazards (electric shocks, equip-potential areas, anti-static locations).

fire hazards (overheating)

mechanical hazards (rotating machines)

lifts, emergency lighting, fire extinguishing systems, alarm and evacuation systems

3.6 Reliability of supply

Factors to be considered include :

level of reliability required depends on application

supply voltage level (HV supply more reliable than LV)

redundancy in circuits

proper protection design (discrimination, etc)

proper maintenance of equipment

choice of equipment.

3.7 Maintenance Issues:

Moisture control

Ventilation and cooling

Corrosion, wear and tear.

Approaches:

Testing as required

Regular visual inspection and testing

Reliability centered monitoring and testing (most favored method).

3.8 Back-up supply

Many applications require some form of back-up, e.g hospital operating theatre

basic system or maintenance of full supply.

un-interruptible supply systems (UPS) are becoming more common in building services.

use diesel generators or battery operated power electronic inverter systems

3.9 DC supply

Rare.

Required in some industrial locations, e.g for adjustable speed motors, electrolysis etc

Generate DC by modern power electronic converters

Older installations may still use rotating machine DC generators driven by AC motors or even mercury arc rectifier systems.

4. In-houseDistribution System

4.1 Supply system layout options4.2 Substation4.3 Switchboards4.4. Cables, busbars etc4.5 Voltage regulation and power factor

4.1 Supply system layout options

Simple radial system

Expanded radial system

Primary selective system

Primary loop system

Secondary selective system

Secondary spot network

Ring bus system

1. Simple radial system

IEEE-Std 315-1979

Load break fused switchTransformer

Low voltage air C/B(draw-out type)

For small loads. One primary service and distribution supply transformer supplies all feeders. Simplest possible arrangement, no duplication or redundancy. Cheapest, least reliable option.

Medium or high-voltageC/B (draw-out type)

Low voltage air C/B(draw-out type)

Load break fused switch

2. Expanded radial system

Two or more radial systems. For larger loads. Similar advantages / disadvantages as simple radial system.

Air break switch

3. Primary selective system

Alternative supply from two sources on primary side of transformer(s). Improved reliability but at higher cost. Maintenance possible without loss of supply.

4. Primary loop system

Greater reliability in case of primary cable failure. Load can be supplied from either end of cable. Finding cable fault may be difficult or dangerous in some cases (one section may be energized from either end).

5. Secondary selective system

Pair of substations connected through a normally open secondary tie CB. If primary feeder or transformer fails, main secondary feeder CB is opened and tie CB closes. General operation of secondaries is as radial systems. Maintenance is possible. Good reliability. Requires consideration of loading if sustained loss of one circuit.

6. Secondary spot network

Loads supplied from 1 common secondary busbar with parallel primary feeders. Use protectors to each secondary connection. If primary feeder fails, protector CB prevents reverse fault in-feed by opening in such an event. Most reliable system. Expensive. Used extensively for high load density applications such as large commercial buildings. Rarely used in industry.

7. Ring bus system

Will automatically isolate a fault.

No interruption of supply for single faults.

High cost (need more components).

Allows safe maintenance without loss of general supply.

One-line diagram of a large industrial plant.Ref.: Industrial and commercial power system handbook

4.2 Substation

Include following items of equipment

general enclosure,

transformer(s),

HV switchgear,

protection system,

backup battery systems,

monitoring equipment for energy, voltage, current, power factor etc

4.3 Switchboards (switchgear assemblies)

Include following items of equipment

main switchgear unit,

output feeder cabling to various loads (or floors of building) together with their separate switchgear and protection.

internal busbar system with rectangular busbars used to interconnect feeder circuits.

protection: means (relays, fuses, CTs), coordination, internal arcing detection

Quite specific in design.

4.4 Cables, busbars, etc

Important factors to be considered:

current ratings,

insulation ratings

fire performance,

segregation of circuits,

bundling of cables (effect on thermal rating),

magnetic fields and any potential interference effects

IP [Ingress Protection] requirements to prevent contamination ingress.

4.5 Voltage regulation and power factor

For LV supply, nominal voltage is 230/400V +10% -6% at 50Hz (AS 60038-2000 Standard Voltages)

Deviation from nominal voltage can cause problems: equipment overheating, light dimming or flickering etc.

AS3000 requires voltage drop between point of supply and any point in electrical installation not exceed 5% of nominal voltage when conductors are carrying maximum demand.

Voltage drop in utility service line should not exceed 3%of nominal voltage when at maximum demand. This is mainly a requirement applied to distributors and their service cable impedance.

pointof supply main

switchboardMSB distribution

board DB

submainfinal

subcircuit

consumermains

load

load

Voltage drop not to exceed 5% i.e. 1-phase (230V) = 11.5V

3-phase (400V) = 20V

Voltage drop not to exceed 5%

5. Voltage Drop

5.1 Voltage drop determination methods5.2 Determination for supply5.3 Determination for transformers 5.4. Parallel operations

For typical length of 50 Hz building system supply circuits, shunt capacitive reactance of cables is negligible and voltage drop calculations can be done adequately by use of short line approximation represented by equivalent circuit:

For a lagging load

Accurate enough for general use. Used for voltage drop calculations extensively.

Require values of R and X which are constant, and I and φ which can vary.

Regulation is load dependent.

For a leading load

5.3 Voltage drop determinationfor transformers

Use of known data for transformers using impedances

Alternatively:

5.4 Parallel operationof transformers and feeders

Parallel lines or transformers divide loads in inverse proportion to their impedance.

Important for transformers to be matched in impedance when they are operated in parallel.

If not matched, one may be overloaded. Also, voltage difference causes circulating current and core saturation.

When T1 is fully loaded, T2 is loaded at only 50%

Can try to operate T2 on a higher voltage tap position to boost its output current.

6. Substations

Substations

Location should be at load centre if possible, so as to keep voltage drop to minimum and to assist in maintaining voltage regulation within requirements.

In high rise buildings, extensive factory or sites with many buildings, a number of substations may be required to distribute power equitably. Normally connected in a ring main system at high voltage (11 kV).

Supply authority will normally determine type and size of substation requirements for a specific situation.

Types of substations

Pole-mounted substation. Pad-mounted substation. Outdoor (fenced) enclosures. Outdoor (building) enclosure. Outdoor transformer with indoor control gear. Indoor basement or ground-floor substation.

Pad-mountedsubstation

315kVA 22kVpole-mountedtransformer

140MVA 132kVgenerator transformer

Pole-mounted substation

Main component: un-enclosed 11kV/415V oil-insulated transformer, rated up to ~500 kVA for providing supply to the building at 415/240V.

Substation is also equipped with HV fuses of expulsion or high rupturing capacity (HRC) type, surge arresters or arcing gaps, low voltage HRC fuses, and earthing system for connection of transformer neutral.

EA’s pole-mounted transformer ratings are from 16kVA to 63kVA for single-phase, and 25kVA to 400kVA for 3-phase.

Height restriction: 3.6m above ground if location is >0.5m away from kerb, or 5m elsewhere.

EA’s network designed to maximum fault level of 18.4kA at 11kV. At 415V, maximum fault level at a pole-mounted transformer is 13.3kA.

Pad-mounted substation

Metal enclosed kiosk-type cubicles mounted on ground. Main component is again an oil-filled transformer of similar or

possibly higher rating than for pole mount type. Kiosk incorporates similar protection and control-gear to pole-

mounted substation. Voltages are also 11kV/415V and maximum power levels are

typically 1000kVA .

Outdoor (fenced) enclosures

Outdoor fenced enclosure. Transformer may be un-enclosed, with appropriate switches,

protection and control-gear within the enclosure. Voltages are typically 11kV/415 V and power ratings are

1500 – 3000 kVA. In some industrial sites voltages and power levels may be

much higher than the above (primarily applicable to building services only).

Outdoor (building) enclosures Dedicated small building containing transformers and other

usual items of equipment listed above. Voltages are 11kV/415V, power ratings are up to ~5000 kVA.

Outdoor transformer + indoor control gear Consists of an open outdoor transformer with a small building

for other equipment as outlined above. Voltages are 11kV/415V, power ratings are up to ~5000 kVA.

Indoor basement or ground-floor substation As above, but located indoors.

Pole substation

Some substation options from EnergyAustralia

overhead 11kV

HV fuse

transformer 11kV/415V nominalDyn11 winding25kVA up to 400kVA600A/phase (400kVA)LV fuse

LV link

For more substation options, see:NS112 Design standards for industrial/commercial developments, EnergyAustralia

Kiosk substation

Some substation options from EnergyAustralia

underground 11kV radialor closed network feeder

11kV ring main fuse switch unit

transformer 160kVA (200A/phase)315kVA (400A/phase)400kVA (600A/phase)

LV fuse

LV link

J kiosk

400kVA600kVA800kVA1000kVA

L kiosk

Kiosk substation (K type)

Some substation options from EnergyAustralia

underground 11kV radialor closed network feeder

11kV ring main circuit breaker switch unit

transformer 1500kVA (2000A/phase)

current transformer

A chamber substation (two transformers)

Some substation options from EnergyAustralia

bus section link normally open

transformers 2 x 750kVA (1400A/phase) 2 x 1000kVA (1600A/phase)

various LV fuse options up to 1 x 1600A per transformer

City CBD substations(no other types permitted in CBD)

Some substation options from EnergyAustralia

isolating and earthing switch

transformers: up to 3 x 1500kVA (5500A/phase)

various LV options up to 2 x 3000A busbars or cable supplies.

LV air CB

Standard specifications

AS 2067-2008 - Substations and high voltage installations exceeding 1 kV a.c.

Electrical requirements

Methods of neutral earthing

Voltage classification

Current in normal operation

Short-circuit current

Rated frequency

Corona

High-voltage design practice wrt EMF

Overvoltages

Harmonics

AS2067:2008

EXTRA SLIDES(NOT INCLUDED IN PRSENTATION)

Hinchinbrook zone substation

Example 3 solution

Design and

Industry Definition for Electrical Services in AustraliaThe Electrical Services industry consists of establishments mainly engaged in the installation of electrical wiring or fittings in buildings or other construction projects. Electricians or electrical contractors are trained and licensed to install, connect, test, and maintain electrical systems for communications, climate control, security, and other purposes. Establishments in this industry also install and maintain electronic controls for industrial machinery and business equipment, install conduit for carrying wires in buildings and structures, and install coaxial cable and optic fibre cable for computer and communications purposes. Electricians also install low voltage wiring for voice, data and video systems, including telephones, computers, intercoms, fire alarms, and security systems. Electrical contractors are trained and licensed to connect wiring to circuit breakers, transformers and other components and test the connections using equipment such as ohmmeters, voltmeters, and oscilloscopes.

Activities (Products and Services) for Electrical Services in AustraliaThe primary activities of firms in this industry are: Repair or maintenance of electrical wiring (except of electricity

transmission or distribution lines). Electrical wiring on construction projects Installation of closed circuit video surveillance systems Installation of exhaust fans Installation of electric light and power fittings Installation of electrical and communication cabling & switching

systems. Installation of illuminated signs Installation of safety switches Installation of specialist industry-specific equipment (e.g. food

manufacturing industry)

The major products and services in this industry are: Maintenance/repair activity - term contracts and irregular demand Upgrading & renovating existing installations New building installation

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