Topic 1 Plant Planning and Power Demand
description
Transcript of Topic 1 Plant Planning and Power Demand
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BEF 44903 Topic 1
BEF 44903 Industrial Power Systems Topic 1
Outlines
1.1 Plant Distribution Systems
1.2 Voltage and Frequency Considerations
1.3 Types of Plant Distribution Networks
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1.4 Power Demand and Load Estimation
1.5 Transformer Sizing
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BEF 44903 Industrial Power Systems Topic 1
1.1 Overview of Electric Power Systems
Generation System13.8 kV 15.6 kV
Distribution System11 kV 66 kV
Transmission System132 kV 500 kV
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BEF 44903 Industrial Power Systems Topic 1
1.1 Example of Plant Distribution System
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Panelboard Feeding240/415V
Harmonic Loads
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
Power system concept: Analysis Selection of the networkconfiguration Type of connection to ground Technical features
Network calculation: Load flow Short-circuit calculation Energy balance
Rating: Transformers Cables Protective/ switching devices Provisions for redundant supply
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Power system planning
BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
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Source: Siemens
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
An optimum network configuration should particularly meet the following requirements:
Favorable and flexible expansionoptions
1 Simple structure
2 High reliability of supply
3 Low losses
4 Favorable and flexible expansionoptions
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optionsoptions
BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
Example of Industrial Power Networks
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
A distribution system deals with the distribution of electrical energy to its specific loads.
The main purposes of planning are:To make the system economical (cost effective).To minimise power losses and maintain regulation
within permissible limits. Load survey and load forecasting of the area are
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necessary.
BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
Load survey of a particular area is carried out to find out the present load requirement as well as the expected load gro th o er a period of 5 to 15 ears The follo ingload growth over a period of 5 to 15 years. The following basic data should be collected for starting this work:
A detailed map of the area showing important features. The existing number of houses, population and new construction
anticipated in the area. The expected number of shops post offices rural health centres
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The expected number of shops, post offices, rural health centres, etc.
The type of industry and number of industries possible in the area.
Development programmes implemented in the area.
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning Distribution Systems
For the purpose of forecasting load, the prospective consumers may be categorized as under:
1 D ti i id ti l h1. Domestic consumers, i.e. residential houses.2. Commercial consumers, i.e. shops, schools, hospitals, hotels,
and other commercial establishments.3. Industrial consumers:
a. Small industriesb. Medium industriesc. Large industries
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d. Municipal consumers (i.e. street lighting, water works, parks, etc.)e. Agricultural consumersf. Mining industries
BEF 44903 Industrial Power Systems Topic 1
1.1 Layout of Distribution Systems
Sub-transmission Line (66kV 33kV)
132kV/66kV 66kV/11kV
11kV Feeder
11kV Feeder
11kV/415V
3 Phase Consumers
(415V)
Single Phase Consumers
Secondary Substation
Distribution Substation
Primary Substation
66kV Feeder
(66kV or 33kV)
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11kV Feeder
Industrial Consumer
Consumers (240V)
66kV Feeder
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BEF 44903 Industrial Power Systems Topic 1
1.1 Layout of Distribution Systems
The high voltage from transmission line (132 kV) is step-down at the Primary Substation to 66 kV or 33 kV.
From this primary substation power at 66 kV or 33kV is From this primary substation, power at 66 kV or 33kV is carried through sub-transmission lines to different load centres. The length of a sub-transmission line is about 50 km and they carry about 50 MW of power.
It has been found that sending power through sub-transmission lines at 33 kV or 66 kV is economical in terms of losses (i.e. I2R) and the capital cost (i.e. cost of
d i l d )
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conductor, insulators and supports). Most domestic, commercial and small-scale industrial
consumers receive power at low voltage, i.e. 240V or 415V. Large-scale consumers having load in excess of 100 kW buy bulk power at 11 kV and above.
BEF 44903 Industrial Power Systems Topic 1
1.1 Planning for Connection
Supplies at Low Voltages of 240V and 415V Maximum power requirements in kVA Types and number of equipment and its
corresponding connected capacity in kVA Shunt connected reactors and capacitors in kVAr For single-phase 240V motors with rating of greater
than 6kVA and/or three-phase 415V motors with rating greater than 75kVA:rating greater than 75kVA: (i) Rating in HP or KVA, (ii) Types of control equipment, (iii)
Methods of starting and starting current, (iv) Frequency of starting (number/hour), and (v) Rated power factor;
Voltage sensitive loads (indicating sensitivity)
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning for Connection
Supplies at 275kV, 132kV, 33kV, 22 kV, 11kV and 6.6kV For all types of loads:
Maximum Active Power consumption in kW; Maximum Reactive Power consumption in kVAR.
For motor loads: Types of control equipment; Methods of starting;g; Magnitude and duration of the starting current; Frequency of starting (number/hour); Under voltage setting and time; Negative phase sequence protection; Sub-transient and/or locked rotor reactance of the motor.
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning for Connection
For nonlinear loads with harmonic current injections: Harmonic current spectrum including harmonic number and
the corresponding maximum currentthe corresponding maximum current.
For fluctuating loads: The rates of change of Active Power and Reactive Power
consumption in kW/minute and kVAR/minute ,respectively, both increasing and decreasing;
The shortest repetitive time interval between fluctuations for Active Power and Reactive Power in minutes; and
The magnitude of the largest step changes in Active Power and Reactive Power in kW and kVAR respectively, both increasing and decreasing.
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BEF 44903 Industrial Power Systems Topic 1
1.1 Planning for Connection
For voltage sensitive loads: steady-state voltage tolerance limits of the equipment in
percentage of the nominal voltage;percentage of the nominal voltage; intrinsic immunity limits to short duration voltage variation; transient voltage tolerance limits of the equipment in
percentage of the nominal voltage and the corresponding duration;
harmonic current emission limit for equipment. For Shunt Connected Reactors and Capacitors:p
configuration and sizes of individual banks; types of switching and control equipment; and types of harmonic filtering reactors.
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BEF 44903 Industrial Power Systems Topic 1
1.2 Voltage and Frequency Considerations
Voltage Criteria Steady-State Voltage Fluctuation (Normal Condition):
Steady-State Voltage Fluctuation (Contingency Condition)
Voltage level % variation415V and 240V -10% & +5%6.6kV, 11 kV, 22kV,33kV +/- 5%132kV and 275kV -5% & +10
Steady-State Voltage Fluctuation (Contingency Condition)
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Voltage level % variation415V and 240V +/- 10%6.6kV, 11 kV, 22kV,33kV +10 & -10%132kV and 275kV +/- 10%
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BEF 44903 Industrial Power Systems Topic 1
1.2 Supply Voltage Options
Low Voltage: Single-phase, two-wire, 240V, up to 12 kVA maximum
demand Three-phase, four-wire, 415V, up to 45 kVA maximum
demand Three-phase, four-wire, C.T. metered, 415V, up to
1,000 kVA maximum demand
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BEF 44903 Industrial Power Systems Topic 1
1.2 Supply Voltage Options
Medium and High Voltages: Three-phase, three-wire and 11 kV for load of 1,000
kVA maximum demand and above Three-phase, three-wire, 22kV or 33kV for load of
5,000 kVA maximum demand and above Three-phase, three-wire, 66kV, 132kV and 275kV for
exceptionally large load of above 25 MVA maximum demand
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BEF 44903 Industrial Power Systems Topic 1
1.2 Voltage and Frequency Considerations
Frequency Criteria The supply frequency is 50 Hz 1%
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BEF 44903 Industrial Power Systems Topic 1
1.3 Classification of Distribution Systems
The distribution systems may be classified in the following ways:
1 A di t t f t ti1. According to nature of constructiona. Overhead distribution system (cheaper)b. Underground distribution system (in crowded area)
2. According to nature of currenta. DC distribution systemb. AC distribution system
3. According to number of wires2-wire DC system 3-wire DC system 1-phase 2-wire AC system
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2 wire DC system, 3 wire DC system, 1 phase 2 wire AC system,3-phase 3-wire AC system, 3-phase 4-wire AC system
4. According to the scheme of connections(a) Radial system(b) Ring system(c) Inter-connected system
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
The 33/11 kV secondary substation is established where the load requirement is approximately 5 MVA. Since normall a primar distrib tion line is designed to carr anormally a primary distribution line is designed to carry a load of 1-2 MVA, the number of primary distribution lines emanating from a 33/11 kV secondary substation is about 4.
When the load requirement increases and crosses about 8 MVA, the losses in the 33 kV sub-transmission line become large Thus power must fed from a 66 kV sub
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become large. Thus, power must fed from a 66 kV sub-transmission line. The number of primary distribution lines emanating from a 66/11 kV secondary substation is six to ten.
BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
There are 3 different ways in which the primary distribution lines can be laid:1. The radial primary circuit2. The loop primary circuit3. The ring main system (or primary network)
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
Radial Primary CircuitsWhen each circuit coming out of a substation is separate from the other circuits and has no inter-connection with any other circuit, it is called a radial circuit.
Factory having load of 1 MW at 11 kV
Circuit 1 for Factory
Circuit 2 feeding Substation in the city
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Secondary Substation
Circuit 3 for Rural Areas
BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
Advantages of Radial Feeders:i. A heavy load very near the secondary substation.ii I l t d l dii. Isolated loads.iii. An area of low load density such as a village.
Limitations of Radial Feeders:i. When the load demand on the radial feeder increases, the
length of the feeder has to be extended. This results in a greater voltage drop which may cause the voltage towards the tail-end
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voltage drop which may cause the voltage towards the tail end to reach a value below the permissible limit.
ii. When a fault occurs at any point along the length of the feeder, supply to all the consumers beyond this point towards the tail-end gets interrupted.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
Loop Primary CircuitsTo overcome the limitations of the radial feeders, the ,loop primary circuit is taken to use.
Secondary Substation
Distribution Substation 2
Distribution Substation 3
CB4 CB5
11 kV 11 kV
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Distribution Substation 1
Substation 2 Substation 3
CB1CB2
CB3 CB6
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
Two 11 kV feeders emanate from the secondary substation.
In this system, every distribution substation receives supply from two sides.
In case of fault, say at point A, the circuit breaker 1 at distribution substation 1 and circuit breaker 6 at distribution substation 3 will open, thus isolating the faulty section. The supply to the substation 1 and 3 is still
i d d i b i d f h
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uninterrupted and continues to be received from another side.
This system is generally used in towns and cities.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
The reliability of supply in this system has improved in comparison with that in the radial system as it has an alternati e s ppl in case one side failsalternative supply, in case one side fails.
However, it must be realized that the source of supply for the whole loop system is a single secondary substation. If a fault occur in the secondary substation causing a failure of the 11 kV supply source, the whole of the system will suffer power interruption.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
Ring Main or Network SystemA more reliable system is the ring main system.y g y
Secondary Substation A
Distribution Substation 2
Distribution Substation 3
CB4 CB511 kV 11 kV
Secondary Substation B
CB7 CB8 CB9 CB10
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Distribution Substation 1
Substation 2 Substation 3
CB1CB2
CB3 CB6
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BEF 44903 Industrial Power Systems Topic 1
1.3 Primary Distribution Lines (Feeders)
In the ring main system, there are two different sourcesof supply which are indicated as secondary substation Aand Band B.
The ring system has the added advantage from loop system is that should one of the sources of supply fail, say A, the whole system continues to get supply from the other source B.
The ring main system is by far the most reliable for i i f l I i b l l i
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continuity of supply. It gives a better voltage regulationand less feeder losses.
Circuit breakers are used instead of fuses for protecting the transformer in ring main system due to heavier loads.
BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
Distribution substations are a link between feeders and distributors.
The standard voltage transformation at a distribution substation is 11 kV/415V. The declared consumer voltage as per Malaysian
Distribution Substations
11 kV Feeders 415 V Distributors
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declared consumer voltage as per Malaysian Nasional Grid is 415 V between phases and 240 V between phase and neutral with a permissible voltage variation of 5%.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
A consumer at the near-end of the distribution substation may have a voltage as high as 436 V(3-phase) and 252 V (single-phase) during light load hours whereas a consumer at the far-endmay have a voltage as low as 395 kV (3-phase) and 228 V (single-phase) at peak load hours.
The circuits for the secondary distribution
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system are essentially the same as those for primary distribution except that they are on a smaller scale.
BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
When power is supplied to the consumers through the secondary distribution system, one of the following arrangements is used:1. Radial system2. Looped system3. Network system (Banked secondary system)
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
Radial SystemIn this system, the LV distribution lines radiate out from the distribution substation.
I thi t th l i f i l 11 kV f d
11 kV Line220 kVA 11
kV/415V
LV CBRadial Line 1
Radial Line 2
Switch-cum Fuse Units
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In this system, the supply is from a single 11 kV feeder. A fault in the feeder will cause the interruption of supply to all consumers. Circuit breaker and switch-cum fuseunits are used for protection purpose.
BEF 44903 Industrial Power Systems Topic 1
1.3 Expanded Radial Scheme
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
Looped SystemIn this case, the reliability of supply is better than in the radial system. In the case of fault on one line, the load can be fed from the other by connecting switch S.
11 kV Line220 kVA 11
kV/415V
CBS
415/240 V
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However, a fault in the 11 kV feeder will cause the interruption of supply to all consumers. Circuit breaker and the fuse unit provide a protection for the transformer and line respectively.
415/240 V
BEF 44903 Industrial Power Systems Topic 1
Primary Selective Scheme
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
Banked Secondary SystemWhen radial secondary circuits are supplied by a single transformer, high starting currents of motors may cause objectionable voltage drops. One of the most effectiveand economical means of controlling such a voltage drop is the banking of distribution transformers.
11 kV Primary Distribution Line
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415/240 V Secondary Distribution Line
T1 T2 T3 Fuse
BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
Transformers are said to be banked when two or more supplied from the same primary circuit are paralleled to feed into the same secondar mainsfeed into the same secondary mains.
By this arrangement more than one path is provided over which high currents can flow. This results in lowering the extent to which the voltage fluctuates on the line.
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Further advantages of this system:i. More reliable, have alternative supply from other transformer.ii. Better load distribution on each transformer.iii. The voltage drop in the system is reduced.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Distribution Lines (Distributors)
This system is mostly used in areas of low load densities, where a multiple primary and secondary net ork is not j stifiednetwork is not justified.
If a fault occurs within one of the transformers, it will be automatically disconnected from the line by blowing the two secondary line fuses and the primary transformer fuse without interrupting service to any consumer.
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BEF 44903 Industrial Power Systems Topic 1
1.3 Secondary Selective Scheme
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BEF 44903 Industrial Power Systems Topic 1
1.3 Sparing Transformer Scheme
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BEF 44903 Industrial Power Systems Topic 1
1.4 Load Data
Typical range of Industrial Loads: Light Industry 50 kVA to 7000 kVA Heavy Industry 1,000 kVA to 200,000 kVA
Typical Industrial Loads: HVAC Process equipment, pumps, compressors and fans Industrial services such as boiler, water treatment Workshop and laboratory equipment Motor control centre
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BEF 44903 Industrial Power Systems Topic 1
1.4 Initial Maximum Demand Estimation
2 methods to estimate the maximum power demand in feasibility/ conceptual design stage: VA/m2 or W/ ft2 This is normally apply to commercial
building where the typical loads are lighting, general power, and HVAC. Example: 50 100 VA/m2 for non-retail buildings, 60 150 VA/m2 for retail buildings. 0.9 W/ft2 for lighting and 4.7 W/ft2 for Air Condition.
Maximum demand of a similar building/ industry g yApplicable for residential, commercial, and industrial buildings. Example: Plant A having maximum demand of 2 MVA then this figure can be used for a plant of similar capacity.
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BEF 44903 Industrial Power Systems Topic 1
1.4 Detailed Load Estimation
Comprehensive load estimate based on actual load information.
Can be calculated either in kVA or amperes. If the output is given in kW, the kVA can be obtained using following formula:
Future load should be considered as given in)( PFkWkVA
Future load should be considered as given in spare circuits for future use.
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BEF 44903 Industrial Power Systems Topic 1
1.4 Diversity Factor (DF)
For better load estimation, a proper diversity factor should be considered as not all
Types of load/ circuit Recommended DF
equipment/ load operate simultaneously. Definition of diversity factor:
Typical diversity factor values:Load ConnectedDemand Max.DF
Types of load/ circuit Recommended DFLighting load 100%General purpose power circuit 40% - 50%Main switchboard 80% - 90%Intermittent duty loads 50%
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BEF 44903 Industrial Power Systems Topic 1
1.4 Example: Max. Loading for MCC (SB)Load
description3/
1
DutyN or
S
Motorrating(kW)
Ope-ratingmotor power (kW)
PF x = K
Motor input power
Heater 3 load (kVA)
1load
R phase (kVA)
1load
Y phase (kVA)
1load
B phase (kVA)
Cooling tower 1 fan 3 N 15 12 0.7 17.1 17.1
Cooling tower 2 fan 3 S 15 12 0.7 17.1 -
Heater 3 N 5 - - - 5 5
Fan coil 1 N 1.5 1.3 0.6 2.2 2.2
Water pump 3 N 11 9 0.68 13.2 13.2
Extract fan 1 N 1 0.8 0.6 1.3 1.3
Compressor 1 N 1.5 1 0.6 1.6 1.6
Future pump 3 N 5.5 4 0.6 6.7 6.7
Total load 42.0 2.2 1.3 1.6
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Total load on the MCC = 47.1 kVA
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BEF 44903 Industrial Power Systems Topic 1
1.4 Example: Max. Loading for LV Switchboard
Load description
Duty (N/ S) Connected (kW)
Operating load (kW)
K kVA
DB 1 - - - - 30
DB 2 - - - - 78
MCC 1 - - - - 47.1
MCC 2 - - - - 50
Packaging machine - 37 31 0.7 44.3
CO2compressor N 75 68 0.765 88.9
W t 1Water pump 1 N 30 25 0.68 36.8
Water pump 2 S 30 25 0.68 -
Welder N 18 - 0.5 36
Future 50
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Total load on LV Switchboard = 461.1 kVA
BEF 44903 Industrial Power Systems Topic 1
1.4 Old Supply Schemes for various M.D
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BEF 44903 Industrial Power Systems Topic 1
1.4 New Supply Schemes for various M.D
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BEF 44903 Industrial Power Systems Topic 1
1.4 In-Class Practise (1)
A small industrial plant has the following loads: Twenty (20), 200HP motors (only half of them are
running at any given time). Ten (10), 50 HP motors (8 motors are running at the
same time). 500 kW of heating and process loads. Two (2), 50 kVA lighting transformers, and
100 HP of small (mostly fractional HP) motors 100 HP of small (mostly fractional HP) motors.
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TASKSDecide the proper supply voltage (from local utility)
TASKSDecide the proper supply voltage (from local utility)
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BEF 44903 Industrial Power Systems Topic 1
1.5 Common Connection for Transformer
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BEF 44903 Industrial Power Systems Topic 1
1.5 Why Delta Grounded Star
Delta at primary Free of 3rd harmonics of the magnetizing currents and
any possible homopolar current are free to circulatethrough the sides of the delta, without flowing into thenetwork; thus, the magnetic fluxes remain sinusoidalat the secondary.
In case of unbalanced loads at the secondarywinding, the reaction current absorbed by the primaryflows only through the corresponding winding (asshown in the figure) without affecting the other two.
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BEF 44903 Industrial Power Systems Topic 1
1.5 Why Delta Grounded Star
Grounded Star at secondary To make line and phase voltages easily available. For safety reasons, since, in the event of a fault
between the MV and LV sides, the voltage at thesecondary remains close to the phase value, thusguaranteeing higher safety for people and maintainingthe insulation.
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BEF 44903 Industrial Power Systems Topic 1
1.5 Basic Installation of Industrial Plant
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BEF 44903 Industrial Power Systems Topic 1
1.5 Methods of Transformer Installation
Method 1 Substation with a single transformer
In the case where the protection device also carries out switching and isolation functions, an interlock must be provided which allows access to the transformer only when the power supply line of the substation has been
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substation has been isolated.
Installation of the SMV switching and isolation device positioned immediately to the supply side of the transformer.
BEF 44903 Industrial Power Systems Topic 1
1.5 Methods of Transformer Installation
Method 2 Substation with two transformerswith one as a spare for the other
The circuit-breakers on the LV side must be connected with an I interlock whose function is to prevent the transformers from operating in parallel.
Apart from the switching and isolation device on the i i MV li (I ) it i
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incoming MV line (IGMV), it is advisable to provide a switching, isolation and protection device on the individual MV risers of the two transformers (IMV1 and IMV2) as well.
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BEF 44903 Industrial Power Systems Topic 1
1.5 Methods of Transformer Installation
Method 3 Substation with two transformerswhich operate in parallel on the same busbar
Possible to use two transformers with lower rated power.
Operation in parallel of the transformers could cause greater problems in management of the network
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network. When coordinating the
protections, the fact that the overcurrent on the LV side is divided between the two transformers must be taken into consideration.
BEF 44903 Industrial Power Systems Topic 1
1.5 Methods of Transformer Installation
Method 4 Substation with two transformerswhich operate simultaneously on two separatehalf-busbars
Providing a CLV bus-tie and an I interlock which prevents the bus-tie from being closed when both the incoming circuit-breakers from the transformer are closed
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transformer are closed. This management
method allows a lower value of the short-circuit current on the busbar.
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BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (2)
Refer again the problem given in In-Class Practise (1).
TASKDesign a simple power system (one-line diagram)
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BEF 44903 Industrial Power Systems Topic 1
1.5 Transformer Sizing
Transformer sizing is generally based on: Total max. demand of individual/group consumer Installed voltage level (kV) Method of installation or arrangement Short circuit capacity
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BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (3):Transformer Sizing
Lets calculate voltage drop in transformer 1000KVA, 11/0.480 kV, impedance 5.75% due to startingof 300 kW 460V 0 8 po er factor motor code Dof 300 kW, 460V, 0.8 power factor, motor code D(kVA/HP). Motor starts 2 times per hour and theallowable voltage drop at transformer secondary terminalis 10%. Is the transformer size suitable?
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BEF 44903 Industrial Power Systems Topic 1
1.5 Transformer Sizing
Code Letter (KVA per HP) -Locked Rotor CurrentMotor Code Min Max
A 3.15 -B 3.16 3.55C 3 56 4C 3.56 4D 4.1 4.5E 4.6 5F 5.1 5.6G 5.7 6.3H 6.4 7.1J 7.2 8K 8.1 9L 9.1 10M 10.1 11.2
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M 10.1 11.2N 11.3 12.5P 12.6 14R 14.1 16S 16.1 18T 18.1 20U 20.1 22.4V 22.5 -
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BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (4):Transformer Sizing
If the previous motor load is changed to the following:
Total KW of Three Phase Motors: 300 kWTotal KW of Single Phase Motors: 10 kWVolt (L-L) : 460 VoltPower Factor: 0.8Locked Rotor Current: 450% (Max)
Analyse again the suitability of the transformer sizeused.
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BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (5):Transformer Sizing
Short circuit capacity with infinite source
FLA = ?What is %Z?ISCmax = ?kVASC = ?
1000 kVA11kV 415 V
Infinite source
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kVASC ?%Z = 5%kVASC = ?
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BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (6):Transformer Sizing
Short circuit capacity with finite source
MVASC(TX) = ?MVASC(SEC) = ?ISCmax = ?
1000 kVA11kV 415 V
500 MVASC
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%Z = 5%kVASC = ?
BEF 44903 Industrial Power Systems Topic 1
1.5 In-Class Practise (7):Transformer Sizing
Simple transformer-load connection
1000 kVA11kV 415 V%Z = 5.0%kVASC = ?
FLA = ?ISCmax = ?kVASC = ?
Is the given size (1000 kVA) suitable to serve
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M 80% Full loadInrush current = 6 times
)the motor load?