Schedule

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Schedule
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Introduction
Load Estimation
Terminology
Basic Equipment
Codes and Standards
Power Distribution Final Circuit
Standby Generator and Power Supplies
Protection Cable Wiring
Earthing
Design of Electricity Distribution
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Introduction and Load Assessment

• Date 23 October 2008
• Module Code

Ir. KF Cheung
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Objectives

• To understand the roles and duties of building
  services engineers
• To enable students to design simple power
  distribution systems
• To appreciate various power distribution design

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(No Transcript)
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Question

• Power requirements of HVAC system
• By HVAC engineer?
• By Electrical engineer?

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• 1 Definition
• 2 Load Assessment
• 2.1 Code of Practice (CoP)
• 2.2 Practice At Early Stage
• Detailed Design Stage

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1. DefinitionA) Active Power (Useful Power) - 1

• Active Power Real Power
• Time average of instantaneous power when the
  average is taken over a complete cycle of an A/C
  waveform.
• Expressed in Watt (W)

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1. DefinitionA) Active Power (Useful Power) - 2

• For Single Phase
• P V I cos ø
• For Balanced Three-Phase
• P v3 Vph-ph I cos ø

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1. DefinitionB) Apparent Power

• For Single Phase
• AP VI
• For Three Phase
• AP v3 V(ph-ph) I

Expressed in Volt-ampere (VA)
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1. DefinitionC) Connected Load

• The Sum of all the loads connected to the
  electrical system.
• This is usually expressed in watts.

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1. DefinitionD) Demand Factor

• This is the factor applied to the connected load
  of an installation to assess the maximum demand
  value.
• Demand Factor Maximum demand
• Connected load

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1. Definition(E) Load Factor

• Load Factor is the ratio of the average demand to
  the maximum demand over a defined interval.
• In most commercial building, for example between
  the hours of 900 to 1800 the load factor is
  usually close to unity.

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1. Definition(E) Load Factor
Typical Load Profile for an Office Building
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1. Definition(F) Power Factor

• Power Factor is defined as the ratio of the
  apparent power in a circuit (V.A) to the useful
  power (W) if the voltage and current are
  sinusoidal
• Power Factor kW/ kV.A

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Example - 1

• Calculate the current demand of a residential
  flat (single phase 220V)with
• 6 nos. of 100W light bulbs and 4 nos. of 40W
  fluorescent lights
• 1 no. of 1.5HP and 2 nos. of 1HP Air conditioners
• 1 no. of 3000W Electric Power
• 2 set of 30A Ring Circuits for 13A Socket Outlets

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Example 1Answer
Total Connected Load
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2. Load Assessment

• Fundamental to electric design
• Feasibility of a project
• Cost

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2. Load Assessment

• How to assess Electrical Load?
• COP for the Electricity (Wiring) Regulation
• Practice

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2.1 Load Assessment Current Demand

• The Current rating of a circuit should not be
  less than the current demand of the circuit

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2.1 Load Assessment Determination of Current
Demand

• General
• The information and value given in this CoP for
  determination of current demand are intended for
  general guidance only as it impossible to specify
  the appropriate allowances for diversity for
  every type of electrical installations

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2.1 Load Assessment Determination of Current
Demand

• For circuit supplying non- simultaneous or cyclic
  loads
• For a circuit having non- simultaneous or cyclic
  loads such that only one of these loads can be in
  use at any one time, the greatest of these loads
  should be used in calculating the current demand
  of the circuit.

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2.1 Load Assessment Determination of Current
Demand

• For final circuit
• According with CoP Code 6, current demand of the
  circuit concerned should be the same as the
  rating of overcurrent protective device of the
  circuit

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2.1 Load Assessment Determination of Current
Demand

• For final circuit
• Each socket outlet in a radial final circuit
  should be assumed to demand its rated current
  rating
• Lighting outlets should be assumed to demand the
  connected lad with a minimum of 100W per
  lampholder
• Current using equipment of a rating not greater
  than 5VA may be neglected
• Discharge lighting should assumed to have a
  demand in volt-amperes of the rated lamp wattage
  multiplied by not less than 1.8.
• All other fixed equipment should be assumed to
  demand the rated or normal current

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2.1 Load Assessment Determination of Current
Demand

• Allowance for Diversity - 1
• This table is applicable to installation having a
  current demand not exceeding 400A in each phase.

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2.1 Load Assessment Determination of Current
Demand

• Allowance for Diversity -2

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2.1 Load Assessment Determination of Current
Demand

• Allowance for Diversity -3

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2.1 Load Assessment Determination of Current
Demand

• Allowance for Diversity - 4

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Example 2Applying Diversity Factor
Total Current Demand
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Example - 3

• Calculate the load demand of the shop (3 phase
  380V) with
• 40 nos. of 100W Light Bulbs
• 24 nos. of 60W Fluorescent Lights
• 2 set of 12kW 3 phase machines with 0.87 power
  factor and 90 efficiency
• 3 nos. of 18kW 3 phase electric heaters
• 3 set of 30A ring circuits for 13A socket outlet

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Example 3Answer
Total Current Demand 132.3A
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2.2 Load Assessment - Practice At Early Stage

• At Early Stage
• Statistic
• Historical Data/ Experience
• Type of Buildings

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2.2 Load Assessment - Practice At Early Stage

• Residential Building
• What are the key parameters?

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2.2 Load Assessment - Practice At Early Stage

• Commercial Building
• What are the key parameters?

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2.2 Load Assessment - Practice At Early Stage

• Industrial Building
• What are the key parameters?

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2.2 Load Assessment - Practice At Early Stage

• Purpose Built Plant
• What are the key parameters?

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2.2 Load Assessment - Practice At Early Stage
Minimum design load capacities for lighting and
small power equipment for various types of
building
Measured total maximum demand loads for
representative sample of large office buildings
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2.2 Load Assessment - Practice At Early Stage -
Example

• Calculate the load of a Residential Tower
• 2-bedroom flats (93 nos.)
• (UFA less than 50m2)
• 3-bedroom flats (51 nos.)
• (UFA less than 50-80m2)
• 3-bedroom flats
• (UFA more than 80m2) (4 nos.)
• Lifts (4 nos.)
• General Lighting Power (1 lot)
• Plumbing Drainage System (1 lot)

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2.2 Load Assessment - Practice At Early Stage -
Example

• Calculate the load of a Commercial Tower
• Carpark Lighting Power (13500m2)
• Arcade Lighting (1000m2)
• Escalator (12 nos.)
• Lifts (4 nos.)
• Podium Lighting Power (excluding arcade
  lighting) (1 lot)
• Plumbing Drainage System (1 lot)

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2.3 Load Assessment Practice B) At Detailed
Design Stage

• The electrical load within most commercial
  buildings can be arranged into the following
  broad categories
• Lighting
• Small power and special user equipment
• HVAC equipment
• Lifts and escalators

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2.3 Load Assessment - PracticeB) At Detailed
Design Stage

• Lighting
• Lighting Load between 8 and 18 W/m2 for
  maintained illuminance levels of 350-500lux
• For large office building, lighting load between
  12-20 W/m2 is reasonable
• In some area of a building special-purpose
  lighting is likely to result in higher electrical
  loads greater than this.

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2.3 Load Assessment Practice B) At Detailed
Design Stage

• What is Special-Purpose Lighting?

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2.3 Load Assessment Practice B) At Detailed
Design Stage

• Small Power and Special User Equipment
• Small Power and user equipment generally consists
  of items which are plugged into socket outlets or
  permanently connected.
• Most of this type of equipment is brought into
  the building by the occupants and not selected by
  the building services designer.

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2.3 Load Assessment Practice B) At Detailed
Design Stage

• HVAC
• In modern ventilated and air conditioned building
  the load required for HVAC apparatus can
  represent 40-50 of the total building load.
• Such loads are affected by the nature of the
  building fabric, fresh air requirements and
  internal heat gains from lighting, people and
  equipment.

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2.3 Load Assessment Practice B) At Detailed
Design Stage

• Lift
• The evaluation of lift requirements must be
  undertaken by a lift specialist who, on the basis
  of the building population, should determine
• Number of Lift
• Speed of Lift
• Capacity of Lift
• Start Current of Large Lift motor

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Q A
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The End