Load Assessment and Regulations

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MECH3005 – Building Servicesg http://www.hku.hk/bse/mech3005/

Electrical Supply –

Electrical Supply

Load Assessment and Regulations

Dr. Sam C M Hui

Department of Mechanical Engineering Department of Mechanical Engineering

The University of Hong Kong E-mail: cmhui@hku hk

E mail: cmhui@hku.hk

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Basic Terms

Active power

Active power

(useful or real power)

(useful or real power)

• Time average of instantaneous power when the

i k l l f A/C

average is taken over a complete cycle of an A/C waveform, expressed in Watt (W)

• For single phase, P = V I cos ø

• For balanced three phase P √3 V I cos ø

• For balanced three-phase, P = √3 Vph-ph I cos ø

Apparent power

pp

p

• For single phase, AP = V I

h h √

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Basic Terms

Connected load

Connected load

• Sum of all the loads connected to the electrical

ll d i

system, usually expressed in watts

Demand factor

Demand factor

• = Maximum demand / Connection load

Load factor

: ratio of the average demand to

the maximum demand over a defined interval

the maximum demand over a defined interval

• In commercial buildings, between the hours 9:00 to 18:00 the load factor is usually close to unity

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Typical load profile for an office building

M Max.

Average

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Basic Terms

Power factor

Power factor

• The ratio of the apparent power in a circuit (V.A)

h f l (W) if h l d

to the useful power (W) if the voltage and current are sinusoidal

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Load Evaluation

Tenant supply

pp y

– energy consumed by each

gy

y

tenant; monitored by separate energy meter

L dl d

l

Landlord supply

:

• Non-essential supply: plumbing and drainage, pp y p g g passenger lifts, air-conditioning plant, public lightingg g

• Essential supply: fire protection/detection system, fireman’s lifts, essential lighting, PABX system, fireman s lifts, essential lighting, PABX system, building management system, important computer room

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Load Evaluation

Objectives

Objectives

• Ensure loading demands are estimated accurately • What happens if they are “under-estimated”?

• What happens if they are “over-estimated”?

Important factors

• Load research data (from power company)

• Design marginDesign margin

• Checking & monitoring at each design stage

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Load Evaluation

Preliminary stage

Preliminary stage

• Estimate total loading so as to:

• Plan the transformer (Tx) & main switch room

• Apply to power company for supply

• Based on rough info or past experience

I t t t k th l d f th BSE t

• Important to know the loads of other BSE systems

Detail design stage

g

g

• Update the estimate w/ more accurate info

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Load Evaluation

Load evaluation by power company

Load evaluation by power company

• Architect/Engineer/Developer submit application

• For typical categories, planning engineer of power company assesses the load estimation using the p y g

database Load Assessment Programme (LAST)

• Compare the declared load with assessed load

• Compare the declared load with assessed load

• If declared load > assessed load, justification is needed

• After finalising the total load, determine the nos. of transformer and transformer bays

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Assessment Guidelines

General

General

• Usable floor area (UFA)

• Follow Building (Planning) Regulations

• Development informationp

• Floor area usage, public services, any special loads

• Standard load estimation sheet (see handouts)

• Standard load estimation sheet (see handouts)

• Public services

• Assessed independently

• Public lighting, lift, water pump, fire services, lobby air g g, , p p, , y conditioning

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Minimum design load capacities for lighting and small power g p g g p requirement for various types of building

Building type Minimum load capacity

(W/m2) (W/m2) Office 60 School 30 Residential building 30 Hospital 25 Hospital 25 Hotel 25 Church 15

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Assessment Guidelines

After diversity maximum demand (ADMD)

After diversity maximum demand (ADMD)

• Load densities derived by dividing the aggregate

l d b h di UFA fl

load by the corresponding UFA or flat nos.

• Cover most typical cases; for special situation, yp ; p ,

designer/planning engineer may exercise his own discretion to adjust the load estimates

discretion to adjust the load estimates

• ADMD is for planning supply Tx capacity, it may not be suitable for designing customer raising

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Assessment Guidelines

• Load assessment data (see handouts)( ) • Residential development

• Commercial development

• Commercial development

• Industrial development

• Municipal development

• Mixed development diversity factor (MDDF)

• Central air conditioning load

• Other special loadsOther special loads

• Reference (from CLP Power)

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ADMD figures for Residential Development

60.0

50.0

ADMD for UFA < 50m2 ADMD for UFA 50-80 m2 ADMD for UFA > 80m2

30.0 40.0

A

/Flat

ADMD for UFA > 80m2

20.0 30.0 kV A 0 0 10.0 0.0 1 6 11 16 21 26 31 36 41 46 51 No. of Flats

What is the effect of load diversity on the kVA/flat data?

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Assessment Guidelines

Load assessment forms

Load assessment forms

• For central air conditioning load

• For general development

Example of electrical load estimation

Example of electrical load estimation

• Estimation of total electrical loading

• Estimation of essential loads

• Electrical supply arrangement

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Assessment Guidelines

Electrical load within most commercial

Electrical load within most commercial

buildings can be arranged into the following

b

d

i

broad categories:

• LightingLighting

• Small power and special user equipment

• HVAC equipment

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Legal Framework

• Typical legal system in Hong Kong (statutory)yp g y g g ( y) • Ordinance (Laws of Hong Kong)

• Regulations

• Regulations

• Code of Practice

• Supporting documents (non-statutory) • Technical Guidelines

• Technical Notes or Technical Memoranda

• Circular letters

• Circular letters

• Reference standards (usually from other countries)

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Legal Framework

Electricity Ordinance & subsidiary regulations

Electricity Ordinance & subsidiary regulations

• Electricity Ordinance (Cap. 406) * • Electricity (Exemption) Regulations

• Electricity (Registration) Regulations

• Electricity Supply Regulations

Electricity (Wiring) RegulationsElectricity (Wiring) Regulations Most important

• Electricity Supply (Special Areas) Regulations El t i l P d t (S f t ) R l ti

• Electrical Products (Safety) Regulation

• Electricity Supply Lines (Protection) Regulation (* can be read from the website www.justice.gov.hk)

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Legal Framework

• Relevant codes and guides to g statutoryy regulationsg • Code of Practice for the Electricity (Wring) Regulations

• Code of Practice for Minimum Fire Services Installations

• Code of Practice for Minimum Fire Services Installations and Equipments

N l i / d d

• Non-statutory regulations/standards

• IEE Regulations for Electrical Installation, 15th edition and/or 16th edition *

• Supply Rules (from power companies)pp y ( p p )

• British Standards Specifications & Codes of Practice or other equivalent national standards and publications

ot e equ va e t at o a sta da ds a d pub cat o s (* IEE = Institution of Electrical Engineers, now IET)

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Legal Framework

Electrical Contractors and Workers

Electrical Contractors and Workers

• Registered Electrical Contractors (REC)

• Registered Electrical Workers (REW) • Grade A Electrical Work (≤ 400 A)Grade A Electrical Work (≤ 400 A)

• Grade B Electrical Work (≤ 2500 A)

• Grade C Electrical Work (any capacity)

• Grade C Electrical Work (any capacity)

• Grade H Electrical Work (high voltage)

• Grade R Electrical Work (special, e.g. neon sign)

• NS: neon light; WH = water heaters; AC = air-conditioners

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Legal Framework

Registered Electrical Workers (REW)

Registered Electrical Workers (REW)

• Permitted work: code • 0 = any categories

• 1 = only issue design certificate

• 2 = only perform installation & repair works

• 3 = only perform repair works3 only perform repair works

• Example:

• “B0” means REW grade B (≤ 2500 A) who can design, install and repair electrical works

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Legal Framework

Certification (new work, alteration or addition)

(

,

)

• Completion of an installation • Certification on the design

• Certification on the design

• Certification on the installation

W k l i ifi

• Work completion certificates

• Form WR1 – a complete installation

• Form WR1(A) – Part of an installation (e.g. for a repair)

• Periodic test certificates

• Form WR2 – a complete installation

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Figure

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References

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