Handout # 01

Electrical Power Distribution and Utilization (EE-357)

For TE Electrical (Spring 2015)

Department of Electrical Engineering

NED University of Engineering and Technology

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

Course Notes- Electrical Power Distribution & Utilization (EE-357)

NED University of Engineering and Technology Karachi Department of Electrical Engineering

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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

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.

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

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

Course Notes- Electrical Power Distribution & Utilization (EE-357)

NED University of Engineering and Technology Karachi Department of Electrical Engineering

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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.

Course Notes- Electrical Power Distribution & Utilization (EE-357)

NED University of Engineering and Technology Karachi Department of Electrical Engineering

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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