Production System and Analysis Report On DESCO

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Production System and Analysis Report On DESCO

Executive Summary

Now a day’s electricity has played a vital role for the economic development of the country as well as makes people’s life easy and comfortable. Reliable, uninterrupted, safe and adequate power supply is a pre-requisite for the development of the country. In this report, have described the total procedure about power transmission, distribution, substation operation, controlling and various protection systems.

The transmission voltage of Uttara Substation is 132/33/11kv As 132kv voltage is very high level voltage so it needs proper protection system to continue its operation properly and to make the place riskless. The equipment used for this power transmission purpose in the transmission lines itself without any risk is described in this report. For the operation of substation it also needs step down transformer for step down power from 132kv to 33kv and also step down power from 33kv to 11kv for the distribution substation. The total procedure of electric power supply with related apparatus itself is taken into consideration in this report. The also mentioned the specification and design of the products used in the substation and how to maintain the regular operation of the substation.

This substation will not only play an important role to meet the demand but it will also contribute significantly in reducing overloading of Grid Sub Station, low voltage problem and will ensure quality power supply in the capital city of Bangladesh.

Chapter-1

Introduction Part

1.2 Objective

1.2.1 Broad Objective

The main objective of the report has been done to show the total working procedure of power transmission, distribution, substation operation, controlling and various protection systems.

1.2.2 Specific Objective

The specific objective of this report includes:

• To study operation of 132/33/11KV substation
• To study the process of power transmission and distribution
• To make an analysis of total power consumption, various losses
• To specify the fault and their protection systems

1.3 Scope

The guidance and data in this report paper are intended to be used by operating and maintenance, personnel. It includes operating instructions, standard inspections, safety precautions and maintenance instructions.

1.4 Methodology

The research of this paper has been done with the help of the different sources. During the preparation of the paper several times it was cheeked by the authorized person of the DESCO. The data was chosen accurately throughout the entire period of the session. Although there were several sources but here some are mentioned as for the proper references. The information of this report has been collected from the following sources:

1. Management Manual

2. Operation Manual

3. Maintenance Manual

4. Product Brochure and Catalog

5. Quality Management Manual

6. Environment, Health & Safety Manual

1.5 Limitations

This report has been prepared on the period of practicum. Total paper was covered nicely through the time duration what was allocated for. show the practical implementation of everything. Although it was not expected but several times there were problems with most major equipments. Right here had the opportunity came to check the entire maintenance, operation of the system. Along with the procedure supervisor used to check up the documents by the in charge experts of the company.

Chapter-2

About DESCO

2.1 Company Profile

The electricity supply industry in South Asia started with the commissioning of the first power station in the 1890s. Although a number on small stations were constructed over the next 20 years, these stations were isolated, catering to small distribution networks serving the major urban centers. The first effort to structure a legal framework for the industry came in 1910 with the enactment of the Indian Electricity Act, 1910. This Act sought to regulate the business of industry still based on the old concept of isolated privately owned distribution networks fed by small generation stations & essentially defined the rights of the supplier & consumer.

In 1947, at the time of independence of India & Pakistan, the installed generating capacity in the then East Pakistan was only 21 MW. Electricity was available to only a small elite in the district and sub-divisional headquarters. The distribution networks in these cities were isolated and were fed by coal fired steam power plants or diesel generation. In an effort to expeditiously augment generation capacity to feed a development economy, the then Government of Pakistan issued and ordinance in 1959 creating the East Pakistan Water and Power Development Authority (EWAPDA). The Ordinance essentially provided for the Governments takeover of all generation, Transmission and distribution facilities from the private sector, thereby creating a total Government monopoly in the sector. During 1960 to 1970 the generation capacity of the then East Pakistan rose from 88MW to 475 MW, supplied largely by natural gas and oil fired, steam power and hydro plants.

Shortly after the creation of an independent Bangladesh, in 1972, the first Government of Bangladesh, in an effort to speed up the investment in the sector issued an Ordinance creating the Bangladesh Power Development Board (BPDB) as the successor organization of the power side of EWAPDA. The Ordinance recognized the divergence of energy related issues in development. During 1972 to 1995, BPDB has increased the generating capacity in the country to 2818 MW, and the length of its 230 and 132 KV transmission networks to 419 KM and 2469 KM. For the first time in December 1982, the eastern and western halves of the country were electrically connected through the commissioning of double circuit 230 KV transmission line across the Jamuna river energized at 132 KV between Ishurdi and Tongi called the first East-West Interconnector.

In order to intensify the pace of rural electrification, the Government issued as ordinance in 1977 establishing the Rural Electrification Board (REB), a semi-autonomous agency charged with the responsibility of planning, developing, financing and construction of rural distribution networks, promoting the establishment of Rural Electric Cooperatives (Palli Bidyut Samities), handing over the constructed rural networks to them, assisting the PBSs to operate and maintain the rural networks and monitoring their financial performance. The REB has so far constructed over 46,000 Km of distribution lines and provided over 950,000 consumers connections in the rural areas.

2.2 Our Vision

2.3 Our Mission

2.4 Corporate Philosophy

2.5 Structure of the DESCO

DESCO incorporated under the Companies Act 1994 with its own Memorandum and Articles of Association. The company as a whole owned by Government of Bangladesh and DESA representing government by acquiring 100% shares. DESCO managed by a part time Board of Directors appointed by its shareholders, they are responsible for policy decisions. The Board of Directors appointed managing Director and two full time Directors and they were also members of the Board Directors after appointment. The organizational of the company is as follows:

• The Chairman DESA being the Board of Directors on his nominee till such time DESA owns the majority of the shares in DESCO.
• The Managing Director acts as the Chief Executive Officer of the company and responsible for overall management of the company.
• The Director (Technical) responsible for development planning supply demand management and operation and maintenance of the system.
• The Director (Finance) responsible for all financial matters and commercial operations of the company.

2.6 Top Management

2.7 Projects of DESCO

2.7.1Complete Project

DESCRIPTION OF THE PROJECT (FOR OVERALL DESCO)

• Land Development
• Civil works
• 132 kv overhead line
• 132 kv U/G cable
• 33 kv O/H line
• 33 kv U/G line
• Construction of 132/33/11 KV S/S Construction of 32/11 KV S/S
• 11 KV O/H line
• 11/0.4 KV O/H line
• 400 V O/H line
• 11 KV UIG cable
• Pole Mounted S/S
• L T Meters (Single Phase)
• L T Meters (Three Phase)
• HT Meters (Three Phase) TransportNehicle (Different type)
• 10.85 Acres 17253.00 m2
• 31.00 Ckt. km. 15.00 Ckt. km. 43.00 Ckt. km. 71.50 Ckt. km. 8.00 Nos.
• 16.00 Nos.
• 150.00 Ckt. km. 500.00 Ckt. km. 600.00 Ckt. km. 400.00 Ckt. km. 3,000 Nos.
• 2,00,000 Nos. 34,000 Nos. 1 ,000 Nos. 48 Nos.

2.7.2 Current Project

• Construction of 33/11 KV new S/S
• R & R of existing 33/11 KV S/S 33 KV U/G Cable
• 11 KV Circuit Breaker
• 11 KV O/H line
• 11/0.4 KV O/H line
• 400 Volts O/H line
• 2 Nos. 4 Nos.
• 44 Ckt. km. 46 Nos.
• 120 Ckt. km. 100 Ckt. km. 100 Ckt. km.
• 11 KV UIG Cable
• 11 KV Aerial Cable 100 Volts UIG Cable 400 Volts Aerial Cables Single Phase Meter
• L T Meter (Three Phase) HT Meter
• 20 Ckt. km.
• 5 Ckt. km. 5 Ckt. km. 5 Ckt. km.
• 20,000 Nos. 5,000 Nos. 100 Nos.

2.7.3 Future Plan

The next candidate project of the reform process is the proposed Ninth Power Project financed by the ADB. This project comprises of four components.

1. Transmission lines and substation capacity associated with the first 600 MW development stage of the Meghnaghat combined Cycle Power Project.
2. Construction of National Control Centre and associated communication network.
3. Construction of new and reinforcement of 132 kv, 33 kv, 11 kv and 0.4 kv distribution lines and transformation capacity in Dhaka City.
4. Engineering of the West Zone Combined Cycle Power Project and the East Zone Open Cycle peaking Power Project.

2.8 Principle of Tariff Setting

Being a commercial organization, DESCO will have to charge for electricity it distributes on a “cost plus performance based return” principle to cover its capital costs, operation costs as well as to target a post tax return of 15 percent on its equity. It is therefore proposed that, till the recommendations of the tariff study to be conducted with World Bank financing are available, DESCO charge a “cost – plus-fixed- return” tariff from its consumers.

Calculation of DESCO’s tariff during 1997-2001 will be based on the estimated costs of the assets initially to be transferred to it by DESA, the Ninth Power Project cost and any other doners share However, these calculations, will be for illustrative purposes only and the actual tariffs will be based on the costs actually incurred and the foreign exchange value of the Taka as computed each year

2.9 Fiscal Year Wise System Loss (Graph) up to August 2011

2.10 Fiscal Year Wise Profit Loss (Graph)

2.11 Related Links

2.12 Power Quality

“DESCO’s motto is to supply quality power to its consumers”

On receiving proper voltage at 33KV level the supply voltages is ensured as :

• Single Phase : 230V-10%, 50 HZ:t 2%
• Three Phase : 400V -10%, 50 HZ:t 2%

*** The quality of supply voltage is fully dependent on the supply from the grid of PGCB. DESCO is maintaining overall power factor of 0.96.

2.13 Customer Service

DESCO strives to offer ‘Service Excellence’ to its valued consumers. Still it has to achieve consumer satisfaction.

Any consumer coming to DESCO’s Sales & Distribution office, can get his/her desired service and solution from the ONE POINT SERVICE representatives. It covers:

• New connection
• Load extension
• Service renovation or relocation
• Billing and collection related complaints
• Reconnection of disconnected lines and other related services

2.14 Year Wise Operational Data

2.15 Technical Highlights

2.16 Commercial Highlights

2.17 Performance

2.17.1 Consumer Mix

Category Consumer Number (%)

Residential 393639 88.00

Industrial 5979 02.00

Commercial 36957 08.00

Others 9554 02.00

2.17.2 Consumption Pattern

Category (MKWh) Consumption (%)

Residential 1315.766 49.00

Industrial 1016.295 38.00

Commercial 258.421 10.00

Others 83.205 3.00

2.18 New Services

DESCO introduced decentralized divisional customer service center with each sales and distribution division. From this center any customer can get the following services:

• New connection
• Load extension or revision
• Service or site relocation
• Consumer name change or tariff change
• Meter test, Change etc.
• Bill correction
• Disconnected consumers service reconnection

2.19 Corporate Directory (Bankers)

01. Arab Bangladesh Bank Limited

02. Agrani Bank Limited

03. Al-Arafa Islami Bank Limited

04. Bank Alfalah Limited

05. Bangladesh Krishi Bank

06. Bank Asia Limited

07. Bangladesh Commerce Bank

08. BRAC Bank

09. City Bank N.A.

10. Dutch Bangla Bank Limited

11. Dhaka Bank Limited

12. Eastern Bank Limited

13. First Security Islami Bank Limited

14. IFIC Bank Limited

15. Janata Bank Limited

16. Jamuna Bank Limited

17. Mercantile Bank Limited

18. Mutual Trust Bank Limited

19. National Credit & Commerce Bank Limited

20. National Bank Limited

21. One Bank Limited

22. ICB Islami Bank Limited

23. Pubali Bank Limited

24. Premier Bank Limited

25. Prime Bank Limited

26. Rupali Bank Limited

27. Standard Bank Limited

28. Shahjalal Islami Bank Limited\

Chapter 3

Substation Apparatus

3.1 Introduction

The electric power system can be divided into the following regions:

1. Generating stations
2. Transmission system
3. Receiving station
4. Distribution system
5. Load points

In all these regions need switchgear. Switchgear is a general term covering a wide range of equipment concerned with switching and protection. All equipment associated with the fault clearing processes are converted by the term ‘Switchgear.’ Switchgear is an essential part of a power system and also that of any electric circuit. Switchgear includes switches, fuses, circuit breakers, isolators, relays, control panels, lightning arresters, current transformers and various associated equipments. Switchgear are necessary at every switching point in AC power system. Between the generating station and final load point, there are several voltage levels.

3.2 Substation

A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Electric power may flow through several substations between generating plant and consumer, and its voltage may change in several steps.

A substation that has a step-up transformer increases the voltage while decreasing the current, while a step-down transformer decreases the voltage while increasing the current for domestic and commercial distribution. The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station.

Figure 3.2 Substation

3.3 Types of Substation

3.3.1 Transmission substation

A transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, the substation contains high-voltage switches that allow lines to be connected or isolated for fault clearance or maintenance. A transmission station may have transformers to convert between two transmission voltages, voltage control/power factor correction devices such as capacitors, reactors or static Vary compensators and equipment such as phase shifting transformers to control power flow between two adjacent power systems.

3.3.2 Distribution Substation

A distribution substation transfers power from the transmission system to the distribution system of an area. It is uneconomical to directly connect electricity consumers to the main transmission network, unless they use large amounts of power, so the distribution station reduces voltage to a value suitable for local distribution. The input for a distribution substation is typically at least two transmission or sub transmission lines. Input voltage may be, for example, 115 kV, or whatever is common in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 and 33 kV depending on the size of the area served and the practices of the local utility. The feeders run along streets overhead (or underground, in some cases) and power the distribution transformers at or near the customer premises.

3.3.3 Collector Substation

In distributed generation projects such as a wind farm, a collector substation may be required. It somewhat resembles a distribution substation although power flow is in the opposite direction, from many wind turbines up into the transmission grid. Usually for economy of construction the collector system operates around 35 kV, and the collector substation steps up voltage to a transmission voltage for the grid. The collector substation can also provide power factor correction if it is needed, metering and control of the wind farm. In some special cases a collector substation can also contain an HVDC static inverter plant.

Collector substations also exist where multiple thermal or hydroelectric power plants of comparable output power are in proximity.

3.3.4 Switching substation

A switching substation is a substation which does not contain transformers and operates only at a single voltage level. Switching substations are sometimes used as collector and distribution stations. Sometimes they are used for switching the current to back-up lines or for parallelizing circuits in case of failure. Example therefore are the switching stations at HVDC Inga-Shaba.

There are several ways of classifying substations. However the two most important ways of classifying them are according to

1. Service requirement

2. Constructional features

4.2.1 According to Service Requirement

A substation may be called upon to change voltage level or improve power factor or convert ac power into dc power etc. according to service requirement substation may be classified into:

I. Transformer substation

II. Switching substations

III. Power factor correction substation

IV. Frequency changer substations

V. Converting substations

VI. industrial substations

4.2.2 According to Constructional Features:

A substation has many components which must be housed properly to ensure continuous and reliable service. According to constructional features the substation are classified as:

1. indoor substation

2. outdoor substation

3. underground substation

4. pole mounted substation

3.4 Stations with change of current type

Substations may be associated with HVDC converter plants, traction current, or interconnected non-synchronous networks; formerly where rotary converters changed frequency.

3.5 Switching function

An important function performed by a substation is switching, which is the connecting and disconnecting of transmission lines or other components to and from the system. Switching events may be “planned” or “unplanned”.

A transmission line or other component may need to be deenergized for maintenance or for new construction, for example, adding or removing a transmission line or a transformer. To maintain reliability of supply, no company ever brings down its whole system for maintenance. All work to be performed, from routine testing to adding entirely new substations, must be done while keeping the whole system running. Perhaps more important, a fault may develop in a transmission line or any other component. Some examples of this: a line is hit by lightning and develops an arc, or a tower is blown down by high wind. The function of the substation is to isolate the faulted portion of the system in the shortest possible time.

There are two main reasons: a fault tends to cause equipment damage; and it tends to destabilize the whole system. For example, a transmission line left in a faulted condition will eventually burn down; similarly, a transformer left in a faulted condition will eventually blow up.[1] While these are happening, the power drain makes the system more unstable. Disconnecting the faulted component, quickly, tends to minimize both of these problems

3.5.1 Power System Automation

Early electrical substations required manual switching or adjustment of equipment, and manual collection of data for load, energy consumption, and abnormal events. As the complexity of distribution networks grew, it became economically necessary to automate supervision and control of substations from a centrally attended point, to allow overall coordination in case of emergencies and to reduce operating costs. Early efforts to remote control substations used dedicated communication wires, often run along side power circuits. Power-line carrier, microwave radio, fiber optic cables as well as dedicated wired remote control circuits have all been applied to Supervisory Control and Data Acquisition (SCADA) for substations. The development of the microprocessor made for an exponential increase in the number of points that could be economically controlled and monitored. Today, standardized communication protocols such as DNP3, IEC 61850 and Modbus, to list a few, are used to allow multiple intelligent electronic devices to communicate with each other and supervisory control centers. Distributed automatic control at substations is one element of the so-called smart grid.

3.6 Typical Substation Distribution Schemes

A Substation, consisting of large breakers and towers, is usually located in an area close to the plant. The substation is used as the distribution center where electrical power is supplied to the plant from the outside, and electrical power is sent from the plant. Often there are at least 2 main Buses. Very high voltages (typically 220,000 or 345,000 volts) are present. Gas and oil circuit breakers are used. The gas (e.g. sulfur hexafluoride) or oil is used to extinguish the arc caused when a breaker is opened, either by a control switch or due to a fault. Manually or motor operated disconnects are provided on either side of the breaker to allow the breaker to be electrically isolated so that maintenance work can be performed.

The diagrams below illustrate typical substation distribution schemes.

3.6.1 Layout of Substation

The layout of the substation is very important since there should be a security of supply. In an ideal substation all circuits and equipment would be duplicated such that following a fault, or during maintenance, a connection remains available. Practically this is not feasible since the cost of implementing such a design is very high. Methods have been adopted to achieve a compromise between complete security of supply and capital investment. There are four categories of substation that give varying securities of supply:

• Category 1: No outage is necessary within the substation for either maintenance or fault conditions.
• Category 2: Short outage is necessary to transfer the load to an alternative circuit for maintenance or fault conditions.
• Category 3: Loss of a circuit or section of the substation due to fault or maintenance.
• Category 4: Loss of the entire substation due to fault or maintenance.

Figure: 3.6.1 Single Line Diagram of Uttara 132/33/11KV Grid Substation

3.6.2 Principle of Substation Layouts

Substation layout consists essentially in arranging a number of switchgear components in an ordered pattern governed by their function and rules of spatial separation.

• Earth Clearance: this is the clearance between live parts and earthed structures, walls, screens and ground.
• Phase Clearance: this is the clearance between live parts of different phases.
• Isolating Distance: this is the clearance between the terminals of an isolator and the connections thereto.
• Section Clearance: this is the clearance between live parts and the terminals of a work section. The limits of this work section, or maintenance zone, may be the ground or a platform from which the man works.

3.6.3 Separation of maintenance zones

Two methods are available for separating equipment in a maintenance zone that has been isolated and made dead.

The choice between the two methods depends on the voltage and whether horizontal or vertical clearances are involved.

• A section clearance is composed of a reach of a man, taken as 8 feet, plus an earth clearance.
• For the voltage at which the earth clearance is 8 feet, the space required will be the same whether a section clearance or an earthed barrier is used.

Separation by earthed barrier = Earth Clearance + 50mm for barrier + Earth Clearance

Separation by section clearance = 2.44m + Earth clearance

• For vertical clearances it is necessary to take into account the space occupied by the equipment and the need for an access platform at higher voltages.
• The height of the platform is taken as 1.37m below the highest point of work.

3.6.4 Establishing Maintenance Zones

Some maintenance zones are easily defined and the need for them is self evident as is the case of a circuit breaker. There should be a means of isolation on each side of the circuit breaker, and to separate it from adjacent live parts, when isolated, either by section clearances.

3.6.5 Maintenance Schedules of Substations

3.6.5.1 Transformers

1. Without shut down activities

Shut down activities

Note:

• Insulation resistance measurement tand of winding/ bushings, winding resistance at all taps to be carried out once before expiry of warranty and then to be continued as per schedule.

• Vibration measurement for reactor to be carried out initially after 3 months and 6 months after commissioning and then to continued as per schedule.

• FRA at factory and during pre-commissioning is preferable to serve as base signature.

3.6.5.2 Circuit Breakers

Breaker Operation Checks

Measurement/ testing

Control cabinet

Minimum Oil Circuit Breakers

3.6.5.3 CURRENT TRANSFORMERS

Marshaling box

3.6.5.4 POTENTIAL TRANSFORMERS

3.6.5.5 DISCONNECTORS AND EARTH SWITCHES

Main Contacts

Operating Mechanism

Earth Switch

3.6.5.6 SURGE ARRESTER

3.6.5.7 Bus-bar, Jumpers, Connectors, Clamps, Switchyard Illumination, etc.

3.6.5.8 CAPACITOR

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