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Handout # 01
Electrical Power Distribution and Utilization (EE-357)
For TE Electrical (Spring 2015)
Department of Electrical Engineering
NED University of Engineering and Technology
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
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EE 155: 3 Credit Hours: ( 48 Lecture hours and 32 practical hours )
Prerequisite: Basic Electrical Engineering & Instrumentation
Instructors: Dr. Muhammad Ali Memon& Mr. Junaid Ahmed Qureshi Lecturer
Department of Electrical Engineering (Extension (2227),
Objective: To equip students with basic skills required to understand the working
procedures along with efficient electrical power utilization at end users
including heating, illumination and cables. Distribution system automation
and understanding of its working through control drawings is also another
aim of course.
Contents summary: Cables sizing, Cable characteristics, Cable fault localization, Pointed and
uniform AC and DC distributors, Substation location, Equipment and
building layout, Substation earthing, One line diagram of schematic,
Illumination design, Resistance heating, Induction furnace, Eddy current
heating, furnace applications, Electric traction , mechanics of train
movement, speed time curves, traction motor types, characteristics and
controls, Electric Vehicle.
The Course Assessment (Calculating to the Final Grade), will be made up of:
(i) Practical Marks Assessment (50 marks)
(ii) Theory Marks Assessment (100 marks)
Sessional: 30 marks based on
10 marks will be given by DR. Muhammad Ali Memon & 20 Marks will be given by Mr.Junaid
A.Qureshi
20 Marks distribution
a) Quiz: 5 marks
b) Test : 10 marks
c) Assignment ---- 05 marks
End of Semester Examination --- 70 marks
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
3
References:
1) Practical Power Distribution for Industry by Jan de Kock & Jan de Kock
2) Electrical Power Distribution and Transmission
by Faulkenberry & Coffer
3) Electic Power Distribution Systems Engineering by Turan Gonen
4) IEEE Recommended Practices for Electric Power Distribution for industry By IEEE standards
5) Lighting Control Techniques & Applications by Robert S. Simpson
6) Electrical Transmission and distribution Reference book
by Central Station Engineers of Westing-house Electric cooperation
7) Electric Power Distribution Systems Operations by Naval Facilities Engineering Command
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
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Introduction
A typical electrical power network is illustrated in Figure 1. An electrical network
initiates at the point of generation. Electrical power is generated by converting the potential
energy available in certain materials into electrical energy. This is either done by direct
conversion of kinetic energy, e.g. wind- or water turbines, or creating steam to drive the turbines,
e.g. coal- or nuclear boilers. Hence the electric utility system is usually divided into three
subsystems which are generation, transmission, and distribution.
Internationally the voltage levels are classified as
LV for less than 1000 V
MV for 1-36KV
HV for greater than 36KV
About 40% of power system investment is in the distribution system equipment
(40%generation, 20%transmission). So the importance of this course lies in our training of the
engineers in such a manner as to deal with equipments, problem identification and problem
solving strategies employed in the industry for distribution systems. That's why the course would
comprise of different arrangements of distribution system and their associated advantages and
disadvantages. Types of loads and the effects they have on the system. What measures need to be
taken in order to manage them. Substation equipment and design, factors and standards to follow
while designing lighting and heating applications.
For an overall understanding of the power system we need to be familiar with regulatory
authorities and key stakeholders of power system
WAPDA :Pakistans water and power development authority
PEPCO: Pakistan Electric and Power Company
NEPRA: National Electric Power and Regularity Authority
NEPRA's main responsibilities are to:
1. Issue Licences for generation, transmission and distribution of electric power;
2. Establish and enforce Standards to ensure quality and safety of operation and supply of electric power to consumers;
3. Approve investment and power acquisition programs of the utility companies; and
4. Determine Tariffs for generation, transmission and distribution of electric power.
NEPRA has given KESC the license to distribute power in entire Karachi and its suburbs upto
Dhabeji and Gharo in Sindh and over Hub, Uthal, Vindhar and Bela in Baluchistan
NTDC operates and maintains twelve 500 KV and twenty nine 220 KV Grid Stations, 5077 km
of 500 KV transmission line and 7359 km of 220 KV transmission line in Pakistan.
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
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MAIN FUNCTIONS
Central Power Purchasing Agency System Operator Transmission Network Operator Contract Registrar and Power Exchange Administrator
i) Central Power Purchasing Agency (CPPA): As the Central Power Purchasing Agency (CPPA), for procurement of power from GENCOs, Hydel & IPPs on behalf of Distribution Companies (DISCOS), for delivery through 500 kV, 220 kV & 132kV Network.
ii) System Operator: For secure, safe and reliable operation, control and despatch of generation facilities.
iii) Transmission Network Operator: For Operation & Maintenance, Planning, Design and expansion of the 500 kV and 220 kV transmission network.
iv) Contract Registrar and Power Exchange Administrator (CRPEA): As CRPEA, to record and monitor contracts relating to bilateral trading system.
WAPDA was bifurcated into two parts WAPDA and PEPCO in October 2007. WAPDA is
responsible for water and hydropower development whereas PEPCO is responsible for thermal
Power Generation, transmission and distribution and billing. PEPCO manages all
GENCOS,DISCOS and NTDC (National Transmission dispatch company)
KESC Generation fleet: Bin Qasim-1 Power Station, Korangi Combined Cycle Power Plant,
560 MW BQPS II Combined Cycle Power Plant , Korangi Thermal Power Plant, Korangi Gas
Engine Power Plant and Site Gas Engine Power Plant.
Transmission side voltage levels of KESC: 220,132,66KV
Distribution system: Distribution system can be further divided into primary and secondary
distribution. The voltage level of primary distribution system is higher than secondary
distribution system. Secondary distribution system is fed through distribution transformers which
step down primary distribution systems voltage levels to around 400/230V.
Most distribution feeders are three-phase and four-wire. The fourth wire is the neutral wire
which is connected to the pole, usually below the phase wires, and grounded periodically. A
three-phase feeder main can be fairly short, on the order of a mile or two, or it can be as long as
30 miles. Actually, the length of feeders is closely linked with load density at location. For
instance, for an area where the customer load density is strong, primary network will end very
close of consumers and secondary feeders will be short. For a weak load density area, primary
and secondary feeders will be longer
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
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Power Cables
Overhead lines:
Advantages
1) Less expensive for longer distance
2) Easy to locate fault
Disadvatages
1) Susceptible to lighting
2) Not environment friendly
3) Maintenance intensive
4) High level of expertise and specialized equipment needed for installation
Reason: Why Aluminum are often used instead of copper?
Answer: Two factors are considered i.e. weight and current density
Underground cables
Advantages
Minimal visual impact
No corona discharge
No bush fire problems
Minimal lightning problems
High level of personnel and public safety, no fallen lines (France 2000, 19 contact deaths with
OH lines, 0 with UG cables)
Good working conditions
Disadvantages
Outage time, locate fault and repair(OH one day, UG 7-10 days)
Fault location instantaneous, can have longer repair time
Continuous trench required (sensitive areas, directional boring)
Soil thermal conditions modified
Presence of vaults and manholes
Distance limitation 100 km for ac cables
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
7
Classification of Cables & Cable Construction
Cables are usually classified according to the voltages for which they are manufactured, their
classification are as follows:
Types Names Voltages (Volts) Size(mm2) LT cables Low tension 1000 630 HT cables High tension 11000 300 EHT cables Extra High Tension 66000 1200
Conductor: The conducting part of the cable is called core, all cables have one or more number
of cores of stranded copper or aluminum. All sizes of conductors of single or three core cables
are circular compacted.
Conductor Screening: Conductor screening is provided for all cables above 11KV grade in the
form of an extruded layer of semi conducting extrusion or semi conducting tape over the
conductor.
Insulation: To insulate the conducting part of the cable from the surrounding we insulate the
cable. The most commonly used insulating compounds are PVC (Polyvinyl Chloride), XLPE
(Cross-Linked Polyethen) & EPR (Ethylene Propylene Rubber).
For most application PVC & XLPE is used because of economical reasons.EPR are most
expensive,XLPE & EPR have the advantage over PVC is that they permit the conductor to
operate at higher temperature(85 C to 90 C) than those of PVC(70 C)
Insulation Type Abbreviation Voltage range Temp (Degree Centigrade) Poly Vinyl Chloride PVC Upto 6.6 kV 70 Cross-Link Polyethylene XLPE 1000-132kV 85-90 Ethylene Propylene Rubber EPR Upto 35kV 105 Vulcanized Indian Rubber VIR 1000V 50-60 Paper Insulated Lead Covered PILC 66kV 70 Chlorinated Poly Vinyl Chloride
CPVC 6.6kV
Note: 6.35/11 Kv:It means that insulation level between each core and earth is 6.35Kv while
11Kv between phase conductors.
Insulation Screening: The cables rated of 11KV are provided with insulation shielding over the
insulation. The screening is provided with an extruded layer of semi conducting compound.
Metallic Sheeting: Metallic sheet is usually lead or lead alloy to prevent the entry of moisture or
for preventing the cable from chemical attack while buried directly in ground.
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Course Notes- Electrical Power Distribution & Utilization (EE-357)
NED University of Engineering and Technology Karachi Department of Electrical Engineering
8
Bedding: Over the metallic sheet, comes the layer of bedding which consists of paper tape
compound with fibrous material also sometimes jute strands or hessian tape is also used. The
purpose of bedding is to protect the metallic sheet from the mechanical injury from the
armouring. It also protect the metallic sheet from corrosion.
Armouring : Armouring is applied over the inner sheath and normally comprises of Galvanized
Steel Strips for multi core cables and galvanized steel wire can be offered as per customer
requirements. For Mining use and other special applications, double Wire/Strip armoured cables
with Tinned Copper wires can also be used.
DSTA: Double Steel tape armored
SWA: Steel wire armored
Filling:
In three core cables it is necessary to fill the interstial spaces with jute, paper or polyethene bag
for two reasons.
1. To ensure good circularity and dimensional accuracy.
2. To prevent an internal passage within the cable from moisture or flammable gases, when
used in hazardous areas.
Serving (Outer Sheath) : Over the armouring a layer of fibrous material is again provided
which is similar to that of bedding but is called serving or outer sheath. This is provided to
protect the cable against weather elements and corrosion.
Figure 1 Cross-sectional view of Power Cable