Final report_Internship_ Fadi 5261 _

Electrical Engineering Department

ELEG397

Summer Internship

Final Report

July 2016

Emergency Power Supply at Das Island –

Electrical Distribution system (ASSESS stage)

Operating Company: ADMA-OPCO Division: DIA

OPCO Mentor: Mr. Mohamed Rafic Ali

Mentor Position: Electrical Engineer

Supervisor: Dr. Mahmoud Meribout

Prepared by:

Fadi Al-Zir ID: 5261

Submission date: July 21st, 2016

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Acknowledgement

I’d like to express my gratitude, first and foremost to my mentor at ADMA-OPCO,

Mr. Mohamed Rafic Ali, who did an outstanding job in making sure that the two months

I spend at the company would give me a 150% benefit as a future engineer and as a

person. Furthermore, I’d like to thank everyone at the DIA division for being extremely

friendly and helpful in all possible matters. The workplace atmosphere was truly a

charm to be in. Also, I’d like to thank my supervisor, Dr. Mahmoud Meribout for

providing all the necessary guidance and support. Finally, I’d like to thank ADMA and

PI for this amazing experience.

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Executive Summary

This is a final report for a summer internship program, centered on a project,

namely, Emergency Power Supply at Das Island – Electrical Distribution system. The

purpose of this project is to develop and propose a suitable electrical backup generator

system for the Das Island and all its facilities by either replacing or upgrading the

existing sets.

The project has been developed to include several design options, which are

analyzed and discussed in this report with the use of various decision-making

techniques. A detailed description of the proposed approach is provided along with the

necessary technical documentation (cable sizing, single-line diagrams etc.). Finally,

analysis of system performance and suggestions are provided. This work encloses a full

ASSESS stage of an engineering project at ADMA.

This report provides a detailed description of all the work done in order to complete

the project, as well as an overview my experiences during my stay at ADMA-OPCO.

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Table of Contents

Acknowledgement ..................................................................................................................... ii

Executive Summary ................................................................................................................. iii

Table of Contents ..................................................................................................................... iv

List of Figures ........................................................................................................................... v

List of Tables ............................................................................................................................ vi

1. Introduction ........................................................................................................................... 1

2. Week I ................................................................................................................................... 2

2.1 Introduction to the workplace .......................................................................................... 2

2.2 Technical Background ..................................................................................................... 2

2.3 Review of IAR ................................................................................................................. 5

3. Week II .................................................................................................................................. 8

3.1 Alternative power supply ................................................................................................ 8

3.2 Emergency loads ........................................................................................................... 10

4. Week III, IV & V ................................................................................................................ 12

4.1 Site visits ....................................................................................................................... 12

4.1.1 Core store and Esnaad visit .................................................................................... 12

4.1.2 Denholm Yam & SARB visit ................................................................................. 12

4.1.3 Schlumberger visit .................................................................................................. 12

4.2 Distribution system ........................................................................................................ 13

4.3 Cable Sizing Calculations.............................................................................................. 15

5. Week VI .............................................................................................................................. 21

5.1 Das Island visit .............................................................................................................. 21

5.2 Conclusion and recommendations ................................................................................. 21

6. References ........................................................................................................................... 22

Appendices .............................................................................................................................. 23

v

List of Figures

Figure 1: Emergency Diesel Generator ..................................................................................... 4

Figure 2: Automatic switch in a switch box (left), in a single-line diagram representation

(right) ......................................................................................................................................... 4

Figure 3: Examples of Radial feeder system distribution .......................................................... 4

Figure 4: Parallel feeder system ................................................................................................ 5

Figure 5: Ring mains system ..................................................................................................... 5

Figure 6: Health Indices Diagram ............................................................................................. 6

Figure 7: Umm Shaif LER EDG Risk Matrix ........................................................................... 7

Figure 8: Umm Shaif LER EDG data sheet .............................................................................. 7

Figure 9: Fuel cell stack ............................................................................................................ 8

Figure 10: Fuel cell architecture ................................................................................................ 8

Figure 11: Capstone microturbine ............................................................................................. 9

Figure 12: Gas turbine architecture ........................................................................................... 9

Figure 13: Airport S/S SLD ..................................................................................................... 10

Figure 14: Mobile Generator ................................................................................................... 11

Figure 15: Airport EDG .......................................................................................................... 11

Figure 16: Possible EDG choice.............................................................................................. 13

Figure 17: Das Island Layout .................................................................................................. 13

Figure 18: Civil sector EPS SLD ............................................................................................. 14

Figure 19: Industrial sector EPS SLD ..................................................................................... 15

Figure 20: Civil sector EPS SLD (Radial)............................................................................... 17

Figure 21: EPS layout .............................................................................................................. 20

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List of Tables

Table 1: EPS Start-up time ........................................................................................................ 3

Table 2: Minimum power-supplying time ................................................................................. 3

Table 3: Das Island EDG sets by area ....................................................................................... 6

Table 4: Cable sizing calculations for radial network ............................................................. 17

Table 5: Civil ring cable loading ............................................................................................. 18

Table 6: Cable sizing for civil sector ring ............................................................................... 19

Table 7: Industrial Ring cable loading .................................................................................... 19

Table 8: Cable sizing for industrial sector ring ....................................................................... 19

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1. Introduction

The Abu Dhabi Marine Operating Company (ADMA-OPCO) is a major producer of

oil and gas from the offshore areas of the Emirate of Abu Dhabi. Being a pioneering

petroleum company in this part of the world, ADMA has completed over 50 years of

oil and gas production. It is commonly known that oil & gas production comes from

two major oil fields, Umm Shaif and Lower Zakum, from which crude oil is transferred

to Das Island for processing, storage and export to international markets.

As an intern at ADMA, I have been assigned to Das Island division’s Operations

Technical Support – a team of engineers who are responsible for providing technical

support for the engineers in the field and ensuring that all of the Das assets perform as

intended. During recent integrity assessments of the electrical assets on the island, it

was uncovered that the Emergency Diesel Generator sets are very old and in a bad

condition, thus unreliable and are heavily underperforming. Therefore, a project was

put together in order to develop a suitable and up-to-date replacement for the existing

system. It is a common practice at ADMA-OPCO for project engineers to divide any

project in four general stages:

Assess – where the project is initiated and the problem is assessed through deep

review of all available sources, ideas and approaches are gathered, concepts are

proposed, and possible options are evaluated

Select – a stage, where the aforementioned options are compared using various

decision-making techniques, and the best solution to the problem is chosen

Define – a major step of following the chosen approach and compiling it into

the front-end and detailed engineering designs

Execute – the final step of implementing the design, construction &

commissioning

In this summer internship program, I was entrusted with and guided through

completing the Assess stage of the project. Consequently, I’ve had the following

tasks/objectives lined up to define the course of action:

Review existing DI EGD data sheets and recent Integrity Assessment reports

Collect information on the essential/emergency loads fed from the existing

EDGs

Define possible options and prepare high-level single-line diagrams

Prepare high-level layout, and perform high level EDG set & cable sizing

calculations

Design the distribution system and prepare high level scope of work

Prepare a final report on all the work done

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2. Week I

2.1 Introduction to the workplace

In my first day at ADMA as an intern, after going through the orientation with

the MDD (Manpower Development Dept.), I had a brief introductory session with the

team leader and my coach, Mr. Mohamed, where we, along with the other 4 students

assigned to the Das Island division, got a chance to introduce ourselves in a form of

short interview. Furthermore, the rules and requirements by which an intern at

ADMA-OPCO is expected to comply were outlined.

Later on, my coach explained my project and all of its aspects to me in detail, and

introduced me to his co-workers while taking me on a short tour around the office.

There, I could see that the DI division consists of several teams of engineers of all

disciplines that we study in our university: Mechanical, Chemical, Petroleum and

finally Electrical, that are all committed to a single cause – providing the technical

support & working on complex projects to ensure that everything in Das Island

operates as required.

Finally, each of the students was provided with his own cubicle, where we would

work on our projects for the period of the internship.

2.2 Technical Background

Before starting off on the tasks outlined in my project sheet (Appendix A) it was

vital for me to get acquainted to the basics of mission-critical power systems.

Emergency power has been a vital aspect in any industry, business or facility ever since

the grid electricity was introduced into the common use. The reason being that mains

power loss due to substation malfunctions, blackouts, downed lines or weather is a

commonly occurring event, which in turn can potentially or necessarily lead to loss of

property and capital, as well as endangering human lives. In order to avoid these

negative outcomes, a suitable backup generator system must be always in place and

ready to pick up after a failed mains supply. Emergency power system is defined in

IEEE Std. 446-1995 [1] as “an independent reserve source of electric energy that, upon

failure or outage of the normal source, automatically provides reliable electric power

within a specified time to critical devices and equipment whose failure to operate

satisfactorily would jeopardize the health and safety of personnel or result in damage

to property. “

IEEE classifies backup power systems based on several requirements:

Maximum start-up time (i.e. power restoration time) – Table 1

Minimum operational time (i.e. the minimum time during which the system

will be able to reliably supply the loads without being refueled or recharged)

– Table 2

Installation, performance and maintenance requirements

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Table 1: EPS Start-up time

Type Power restoration time

U Uninterruptible Power Supply (UPS)

10 10 seconds

60 60 seconds

120 120 seconds

Here, it is important to explain the concept of the first type: the Uninterruptible Power

Supply. UPS is an electrical device, which is meant to supply power to the load when

the main power supply fails for a brief period of time (not more than several hours). It

is different from any other type of supply because of its ability to provide instantaneous

protection from input power interruptions for shutdown-sensitive devices. For example,

most businesses rely on powerful computers normally gathered in a server room, to

store information and provide a common platform for company’s software. Hence, in a

case of an unfortunate event, such as a common blackout, these computers would

instantly switch off, at what point some hardware could be damaged, which would

cause a critically harmful loss of data and communications. The UPS is meant to

prevent such consequences, by instantly providing the required power in order to enable

the user to save his work and go through the server shut-down routine safely. In essence,

a common UPS can be considered as a large standby battery unit.

Table 2: Minimum power-supplying time

Type Power supplying period

0.083 5 minutes

0.25 15 minutes

2 2 hours

6 6 hours

48 48 hours

Finally, a power system has two classes based on the criticality of the equipment it

would supply. The first class would refer to the equipment, failure of which could result

in loss of human life, cause serious injuries or heavy capital losses for the user. Hence,

the second class would encompass all other emergency power systems that are

redundant or where the equipment they supply is less mission critical.

Hence, in this project, the considered qualities of the EPS system would be consequent

to the previously present gensets (abb. generator sets): the system would be required to

start in 10 seconds or less, supply power for at least 48 hours, and would belong to the

first class, as it is evident beforehand that any power loss for equipment in Oil & Gas

industry potentially incurs harm to both human life and the company’s welfare.

Furthermore, it is important to outline what comprises an Emergency Power System.

First of all of course, the supply itself, which, as mentioned above can differ by its

application capabilities and finally by its type. The commonly used EPS generators

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include, but not limited to: diesel generators (a most popular and favored option –

Figure 1), flywheel, fuel cell and gas turbine technologies.

Secondly, an EPS includes an appropriate switching device, which must be provided

to correctly and safely switch the critical loads from the normal power source to the

standby source. These have several types based on the specific load requirements:

Automatic transfer switch - self-acting equipment for transferring one or more

load conductor connections from one power source to another (Figure 2) [1]

Circuit breakers – electrically or manually operated

Bypass/isolation switches – these, apart from the main function, are used in

addition to, and in order to bypass the main transfer switch and connect the

source directly to the load, which may be used to bypass UPS, such that a failure

in UPS during normal up-time does not interrupt the power supply to the load.

Static transfer switch – similar equipment, only used in applications, requiring

high-speed operation (i.e. 2-4 ms. Reaction time) applicable in systems, backed

up by UPS.

Finally, EPS, similarly to any electrical system, may have different arrangements,

commonly known as distribution systems/networks. These are mainly concerned with

the connection of the aforementioned elements. Many distribution systems operate

using a radial feeder system (Figure 3). In such fashion, all loads are each fed

separately from a common bus-bar, essentially each having a separate connection to

the supply. Radial feeders are the simplest and the least expensive, in terms of

construction and for their protection system requirements. However, this advantage is

offset by the difficulty of maintaining supply in the event of a fault in the feeder,

which would result in the loss of supply until the fault is located and repaired.

Figure 2: Automatic switch in a switch box (left),

in a single-line diagram representation (right) Figure 1: Emergency Diesel Generator

Figure 3: Examples of Radial feeder system distribution

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To improve the reliability factor here, it may be possible to have the separate sets of

cables follow different routes from the supply. In this case the cost, as well as

reliability, is double that of a radial feeder, however this may be justified by the load

criticality. Furthermore, it maintains the simplicity of the former. Such option can be

provided by a ‘parallel feeder’ system (Figure 4), which, simply put, provides a

second path for the supply in case one of the feeder sets fail, allowing the remaining

feeder to continue the supply of power.

A similar level of reliability at a lower cost can be achieved by using a ring mains

setup (Figure 5). Here, the supply and the load switches comprise a full circuit –

“ring”, which provides means to isolate only the faulty section of the cable, in case

the fault occurs, by the protective action of circuit breakers (denoted as “CB” in the

figure), thus maintaining the supply to all loads by both pathways. Furthermore, this

system provides means for a continuous supply to each load substation, thus reducing

line voltage drops, which affect the whole system and may occur due to a cable fault

which in turn may potentially briefly shut-off several loads, as compared to the

previously discussed distribution arrangements.

Finally, high-voltage transmission and sub-transmission systems require an even

greater level of reliability, because of more severe consequences of cable fault event,

resulting from a higher number of end-loads and substations in such systems. Here,

the so-called “meshed” systems are used. These however, will not be applicable to the

low-voltage (415V loads) project at hand.

This concludes the bulk of the most necessary information needed for the project.

More technical information is, however, provided throughout the report, where

necessary.

2.3 Review of IAR

The first project-related document provided by my coach was a report of an

integrity assessment routine, performed on all Das Island electrical assets by the

specialized “ERA technology” company. ERA has undertaken an integrity and

remaining life assessment of the 11kV and 3.3kV electrical distribution assets

together with LV switchgear panels and emergency generators, with the latter being

Figure 5: Ring mains system Figure 4: Parallel feeder

system

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our sole point of interest. Many of the electrical assets were found to be more than 30

years old and are therefore at or approaching the end of their design lives, which in

turn was the main reason for initiating this project.

The assessment methodology comprised visual inspection, electrical testing

and a review of ADMA maintenance and inspection procedures with health indices

produced for each of the electrical assets. The visual inspection and testing was

carried out during the first half of 2014. The report includes detailed results and health

indices for each asset, which are summarized in the bar graph (Figure 6). The asset

condition is defined numerically on a scale of A to E, where A signifies the best

condition with a remaining life greater than 10 years and E the worst condition

(replace or carry out rectification work immediately).

Here, we can see that out of the total 15 emergency gen-sets, 14 were examined and at

least 8 require replacement or state-rectification as soon as possible. It is also

important to note, that the examined gen-sets also include 5 mobile generators, 3 of

which are recommended to be replaced. However, the focus of this project is only on

the installed static EDG sets, because the replacement of mobile platforms is trivial

and will be done by replacing them with newer models, one-by-one. Finally, out of 10

stationary EDG sets, 2 are new and recently installed, 4 require replacement and the

remaining 4 were in an acceptable condition, but of a similar age of >30 years old,

where their reliability is unacceptably low. Hence, in this project, we had to replace 8

stationary EDG sets, evenly divided by the installation area and denoted by the name

of the substation they back-up (Table 3).

Table 3: Das Island EDG sets by area

Industrial area Rating (kVA) Civilian area Rating (kVA)

Zakum LER 187.5 Airport 187.5

Umm Shaif LER 187.5 Telecom 321

STOREX 328 Hospital 500

CTU LER 80 Sub P 300

Figure 6: Health Indices Diagram

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Here, it was vital to separate the EDG sets by their installation area, because of the

different HSE requirements for either. For example, if we would choose a gas-

supplied generator, it would need a steady pipeline of gas, which would present

additional potential threat to production in the industrial area, requiring extra

protection, which in turn means installation issues and even more expenses. For more

information, refer to the basic Das Island map provided in Appendix B.

Furthermore, the IAR included a detailed technical passport for each of the

evaluated electrical assets. Such passport provides a detailed specification sheet

(Figure 7) along with a summary of the asset evaluation, and the consequent Risk

Assessment matrix (Figure 8) showing the condition of the asset as compared against

the “A to E” criteria discussed before.

In the figures above, we can see an example excerpts from the technical passport of

the Umm Shaif LER EDG set. Here, the risk matrix indicates that the generator has

the highest consequence of failure index, i.e. it is mission-critical and its failure will

result in damage or loss of property, endanger human life & environment and finally

will greatly affect production. Furthermore, its health index is rated as by letter “D”,

which indicates that in its current state, it is recommended to be replaced in under 3

years. On the other hand, the matrix indicates that with due repairs and rectification its

service lifetime may be prolonged. However, due to its high consequence of failure

index, state-rectification is out of consideration, hence this generator needs to be

replaced as soon as possible in order to avoid any unfortunate events.

Finally, the overall report has shown that most of the gen-sets do not have any

maintenance records to them, and hence their maintenance and required checkup may

have been delayed, which may have resulted the current state of the asset. To note, it

is a general rule to run all emergency generators for at least 30 minutes at the end of

each month in order to ensure the reliability of the assets and plan to carry out any

rectification if evidently needed.

Figure 8: Umm Shaif LER EDG data sheet Figure 7: Umm Shaif LER EDG Risk

Matrix

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3. Week II

3.1 Alternative power supply

After reviewing the IAR and collecting the necessary background information,

it has become evident that this project can be easily overlooked with a simple one-to-

one replacement of generators and a most popularly used distribution network. Hence

it was necessary to look further into the new technologies and solutions in mission-

critical power supply systems.

Nowadays, most emergency generators or generators in general consist of a well-

known diesel engine and an alternator, which converts mechanical energy into

electrical. These come in hundreds of different designs, sizes, capabilities and

specifications depending on the client requirements, an example was displayed in

Figure 1. Regardless of its popularity and variations, the design of diesel generators

has about reached its technological “ceiling”, at which point its electrical and fuel

efficiency can hardly be improved [3]. This has allowed for technologies like fuel

cells, flywheel and turbines to occupy a noticeable niche in various industrial

applications in recent years. With regards to the project at hand, however, it was

found that only two of the alternative power supply technologies are applicable: fuel

cells, and a variation of a gas turbine, because the flywheel technology has low

generative capabilities for the required application and is mainly used as UPS.

A fuel cell is defined as a device that generates electricity by means of a chemical

reaction (Figure 9). Every fuel cell has two electrodes, an anode and a cathode. The

reactions that produce electricity take place at the electrodes. Every fuel cell also has

an electrolyte, which carries electrically charged particles from one electrode to the

other, and a catalyst, which speeds the reactions at the electrodes. Most commonly

used fuel is hydrogen. One great appeal of fuel cells is that they generate electricity

with very little pollution: much of the hydrogen and oxygen used in generating

electricity ultimately combine to form a harmless byproduct – water, which

immediately places them above the diesel engines that are known for their high

environmental impact. Furthermore, other types of gases may as well be used with the

new technological advancements in fuel cells, to produce just as little pollutants.

However, a fuel cell by itself is a small device, able to produce about 20W of power,

which is why they are usually assembled into big stacks, which are then capable to

match the productivity of a normal diesel engine. Figure 10 shows an example of such

stack, a fuel cell based 1MW “Energy Server” by BloomEnergy.

Figure 10: Fuel cell architecture Figure 9: Fuel cell stack

9

On the other hand, there is a unique technology of a “microturbine” power supply

devised by Capstone – essentially working by the same principle as a normal gas

turbine (Figure 11-12), albeit the size and the noise levels, while pertaining the high

efficiency and low emissions traits of the former.

Gas turbine is defined as a type of internal combustion engine. It has an upstream

rotating compressor coupled to a downstream turbine, and a combustion chamber in

between. The basic operation of the gas turbine is similar to that of the steam power

plant except that air is used instead of water. Fresh atmospheric air flows through a

compressor that brings it to higher pressure. Energy is then added by spraying fuel

into the air and igniting it so the combustion generates a high-temperature flow. This

high-temperature high-pressure gas enters a turbine, where it expands down to the

exhaust pressure, producing a shaft work output in the process. The turbine shaft work

is used to drive the compressor and other devices such as an electric generator that

may be coupled to the shaft. The energy that is not used for shaft work comes out in

the exhaust gases, so these have either a high temperature or a high velocity. The

purpose of the gas turbine determines the design so that the most desirable energy

form is maximized. Similarly to the fuel cells, these may be configured for various

types of fuel (natural gas, waste gas, landfill, kerosene, diesel, propane, methane,

biogas and many others) depending on the site availability and requirements.

All of the advantages of these alternative generators are often overlooked because of

the higher initial costs as opposed to the diesel generators. However, the latter are

offset by lower long-term running costs, because fuel cells and microturbines require

little (the latter have only one moving part) to no maintenance (fuel cells are only

limited by their 30-year guaranteed life expectancy). Finally, both technologies are

yet to gain the trust of industrial clients, even though both have been recently

successfully integrated in various applications in US and Europe, including Oil &

Gas.

To summarize, both alternative technologies presume a “Clean & Green” approach,

which is a great response to the overall Health, Safety & Environment importance

trend. Furthermore, it would be a great and prestigious technological advancement for

the company, being the first-of-its-kind application in the Gulf region. However, both

require a steady supply of gaseous fuel, which means that the installation would also

require a gas pipeline to be routed through the island, which may in turn present

difficulties due to its dangerous nature.

Figure 12: Gas turbine architecture Figure 11: Capstone microturbine

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After finalizing all possible research on the matter of alternative power supply, I’ve

put together a list of most well-known fuel cell suppliers in the market, their contact

information and the relevant datasheets of their products. Together with Mr.

Mohamed, we composed and dispatched inquiry e-mails to these companies, to find

out more about their products and their experience in Oil & Gas applications, in order

to set up a good ground for any further development of the project in this direction.

Similarly, we have dispatched an inquiry e-mail to Capstone “Microturbines”, who,

unlike the US-based fuel cell companies, have a business branch here in UAE. We

made contact, where a Capstone representative shared an in-depth presentation and

specifications of their products, along with a proposal of a meeting to discuss the

latter.

3.2 Emergency loads

Afterwards, it was essential to proceed on the next important project task,

which is gathering information (i.e. single line diagrams as such) on all the loads in

Das Island that need to be backed-up by an emergency generator. I was able to obtain

the SLD files from ADMA’s internal file system, with the help of my coach.

In all the substation layouts, a certain structure is followed, as may be seen in Figure

13. All of the loads fed from the main sector substation (here – airport s/s) are divided

into [2]:

• Essential - loads that need to be always supplied with power in order to avoid

either stopping production (pumps in a refinery for example) or incurring any HSE

issues and dangers (emergency lights, AC etc.)

• Non-essential - loads, whose switching out is permissible in case of a

blackout, and does not incur any collateral damage or danger (normal lights, sockets

in civilian buildings etc.)

Figure 13: Airport S/S SLD

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In the figure, we can see the bus with the circuit-breakers leading to the switchboards

responsible for their non-essential loads on the right, denoted as the main distribution

board (MDB). This MDB is fed from the main substation power supply, which is then

routed through one of the circuit-breakers towards the essential load distribution

board (shown on the left). Here, as we can see in the top-middle part of the figure, the

connection of the two distribution boards runs through a changeover switch,

essentially a single-pole-double-throw (SPDT) type, where one of the throws is

connected to a standby emergency diesel generator (Figure 14). In this fashion, once

the power from the main supply is cut, the power to the essential loads is drawn from

the gen-set instead. Furthermore, an additional changeover switch (top-left section in

Figure 13) allows for the 3rd supply option, in case during a mains blackout the

backup generator will fail to start. This switch allows for a socket outlet, to which a

mobile backup generator (Figure 15) can be connected to supply the essential loads.

As my coach has advised, it would make sense to simply refer to the old EDG set

capacities (as presented in Table 3) as the maximum load requirements. Here, it is

known that the currently employed generators are not used to their full potential i.e.

about 40% of the available power capacity is left unused. However, it would be

necessary to maintain that allowance while developing a replacement system in order

to accommodate for possible addition of loads in the future. Finally, it was found that

all emergency loads require 415V (or 0.415 kV as per industrial standards) power.

Figure 15: Airport EDG Figure 14: Mobile Generator

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4. Week III, IV & V

These three weeks can mostly be described by a handful of site visits organized by

ADMA, and working on the final tasks of my project.

4.1 Site visits

4.1.1 Core store and Esnaad visit

During our first site visit, we went to the Esnaad premises in Musaffah, where

ADMA is renting a space for their needs. There, we were given a presentation and it

was explained to us that ADMA has three divisions based there: Drilling, Commercial

and Logistics. All these are responsible for supplying ADMA offshore facilities with

the required supplies and tools. We were given a brief lecture on basic structure of the

3 divisions mentioned above, i.e. what they do, how they do it etc. Afterwards we

were taken on a brief bus-tour to take a look at some of the ADMA equipment and

facilities based in Esnaad. Next, we drove to the Musaffah core store, where we were

given an overview about cores, their importance and use. Furthermore, we could

examine a handful of core samples, determine the differences, and look at some under

a microscope. Here, the visit would most correctly be described as geoscience-

oriented.

4.1.2 Denholm Yam & SARB visit

On our second site visit, we went to Denholm Yam Steel Factory, where we

were given two presentations: first about the SARB project, where we were

thoroughly informed about the current state of the project, completed & upcoming

phases, challenges and general information. The second presentation was about the

Denholm Yam company itself, where we were shown a video, describing the current

projects of the company, and were informed about how the company operates,

amongst others, the “Dubai-I” project contribution appeared an amazing effort.

Finally, we were given a brief tour of the premises, the fabrication yard.

4.1.3 Schlumberger visit

We have also visited the Schlumberger training center, where we were given a

long presentation about wired modules used in drilling and exploration, first the

theory of usage, and then the applications and examples of use, available options etc.

Afterwards we were given a brief tour of the premises, the workshop in particular,

where we were shown different types of equipment involved in wired module

operation.

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4.2 Distribution system

Apart from selecting the best possible power supply type for the backup

system, it was also vital to develop a suitable distribution network in order to deliver

the needed power in case of an emergency, considering all of the 8 substations.

As it was mentioned before in 2.2, most commonly used distribution systems are the

radial feeder and the ring mains (Figure 3 & 5 respectively), where the former is

cheaper in terms of cabling and installation but does not provide means for fault

isolation – thus less reliable, while the latter is exactly vice-versa. Consequently, as in

the system at hand, reliability is valued over cost in general, due to it being an

emergency system, hence a ring mains power distribution would be the preferred

choice. However, this will be thoroughly justified in the next section of the report.

It was proposed to provisionally divide the Das Island essential loads by their

location, as it may be seen in Figure 16 (Appendix B), where the separation is marked

with the green dashed line, thus having the top of the island as an industrial area

comprised of plants and refineries, while the bottom half can be considered a civilian

area. Here we can also see the essential loads marked in blue or red, depending on the

area.

Since the development of a new distribution network over the previously employed

can be best described as an optimization process, the first step here would be to cut

down on the number of the emergency power supply sets in favor of bigger, high

capacity units which would be able to simultaneously supply multiple loads,

essentially making the emergency system more centralized and well-structured. In

such layout, the best solution would be to have two generator sets, one per each area

for the respective loads, locations of which are marked with yellow dots in Figure 16.

Moreover, the reliability of the system can be further enhanced by introducing a

redundancy in the genset, also known as “N+1”, where one generator would be the

main emergency supply, while the second, having the exactly the same specifications,

Figure 17: Das Island Layout Figure 16: Possible EDG choice

14

would be on standby in case the former fails. Such behavior would be made possible

by an automatic changeover switch (SPDT type).

This approach will:

Reduce maintenance costs (both technical and manpower)

Reduce the footprint of the system (i.e. total area occupied) – which is an

essential factor when dealing with installments on a constrained area (i.e. an

island in this case)

Reduce the initial costs of the project

In such fashion, we can easily calculate the combined load ratings for the two sets,

based on the load information obtained earlier (Table 3), thus having 783 kVA and

1308.5 kVA for the industrial and civil emergency loads respectively. Finally, keeping

in mind that a slightly bigger-than-required capacity generator must be selected, in

order to allow for possible additional loads in the future, we can, for example, choose

the two generator models provided by “Caterpillar”, 1100kVA (CAT C32 ATAAC)

and 1500kVA (CAT 3512B TA) low-emission diesel generators for industrial and

civil substations (Figure 17 top and bottom respectively).

Afterwards, it was necessary to proceed to designing the layout of the network. First,

a single line diagram was put together for the loads in the civil sector of the island

(Figure 18) depicting the previously discussed decisions.

Here, we can see the two identical emergency power supply units (EPS1 & EPS2)

connected to a SPDT switch, which is then connected to a bus, and then distributed in

a ring network.

Figure 18: Civil sector EPS SLD

15

To note, it is known that an ideal ring mains would have an equal amount of loading

on each side of the ring (if we divide the diagram vertically on cable 3) which would

in turn half the transmitted current. We can see from the diagram that the loading is

well distributed, 621kVA vs. 687kVA for cable 1 and cable 5 respectively, which is

quite close to an ideal case and in turn will be helpful in the next section.

On the other hand, we have the single-line diagram of the distribution network

proposed for the industrial sector in Figure 19. Here, we can see that the structure is

similar to the previously discussed, except of course for the capacities of the

generators and the loads. Furthermore, we can see a similar load split, having 408

kVA at the side of cable 1 and 375 kVA at cable 5.

Finally, it is important to note that in both cases, appropriate protective equipment

(i.e. circuit breakers) must be incorporated into the design.

4.3 Cable Sizing Calculations

After selecting a suitable distribution network, we can proceed to the last step

of the system design, the cable sizing. Essentially, in this step, an electrical engineer

calculates and selects the best possible option for a cable to connect two devices,

choosing from a wide variety of types and sizes. The cable sizing calculations end-

point is obtaining the voltage drop that will occur in the cable between the supply and

the load, which is the essential factor to gauge if the cable choice is correct. The

following voltage drop criteria is normally used in ADMA:

o < 2% for a radial feeder distribution

o < 4% for a ring mains distribution

Based on this, the cable size, essentially the size of its cross-sectional area, is chosen.

Figure 19: Industrial sector EPS SLD

16

Furthermore, the voltage drop in a cable relies on the following:

Cable installation method & location – responsible for a handful of cable

characteristics:

o Cable location:

In ground:

Burial depth

Soil thermal resistivity

Ground temperature

In air

In duct

o Grouping Factor

o Short-circuit rating (only HV and MV applications)

Cable resistance and reactance

Cable length

During the calculations one must remember that in addition to the voltage drop

constraints, it is necessary for the cable de-rated current carrying capacity to be higher

than the full load current. If that is not the case, several runs of same cable should be

introduced to carry the current. Finally, several cables of lesser size can be combined

in parallel runs in order to replace a bigger cable, which is a common practice because

it is easier and cheaper to handle smaller cables.

Now that all the required characteristics were considered, we can move on to the

process of performing the cable sizing calculations step by step.

1. Find the drawn full load current 𝐼𝑓𝑙, using the known load rating in VA and the

Line-to-line voltage (415V in this case) as follows:

𝐼𝑓𝑙 =𝑆

415 ∗ √3 [𝐴]

2. Determine the minimum cross-section of the cable. Assuming a constant LV

fault level: 𝐼𝑠𝑐 = 20 𝑘𝐴, 𝑡 = 1 𝑠

𝑆𝑚𝑖𝑛 = √t ∗ 𝐼sc

144= 139𝑚𝑚2 ≈ 150𝑚𝑚2 (𝑛𝑒𝑥𝑡 𝑐𝑎𝑏𝑙𝑒 𝑠𝑖𝑧𝑒 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒 𝑜𝑛 𝑡ℎ𝑒 𝑚𝑎𝑟𝑘𝑒𝑡)

This minimum size will be applicable to all calculations related to this project.

3. Select an arbitrary cable size referring to the minimum, and find it’s current-

carrying capacity ( 𝐼𝐶𝐶𝐶 ) from the cable manufacturer datasheet (Ducab –

Appendix C)

4. Calculate the de-rated current-carrying capacity 𝐼𝐶𝐶𝐶𝑑𝑒𝑟𝑎𝑡𝑒𝑑 , using a

combination of the cable location factors (Deration factor) as follows:

For the project, the following factors shall be used (as per the datasheet):

Ground temperature (40C) – 0.82

Soil Resistivity (2.5 Km/W) – 0.73

Burial at 0.8m – 0.97

Grouping factor – 1

Deration factor = Gt*SR*B*Gf = 0.58

17

𝐼𝐶𝐶𝐶𝑑𝑒𝑟𝑎𝑡𝑒𝑑 = 𝐼𝐶𝐶𝐶 ∗ 𝐷𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟

5. Calculate the required number of runs with the current cable size as follows:

𝑀𝑖𝑛𝑖𝑚𝑢𝑚 𝑐𝑎𝑏𝑙𝑒 𝑟𝑢𝑛𝑠 =𝐼𝑓𝑙

𝐼𝐶𝐶𝐶𝑑𝑒𝑟𝑎𝑡𝑒𝑑 [𝑟𝑜𝑢𝑛𝑑 𝑡𝑜 ℎ𝑖𝑔ℎ𝑒𝑠𝑡 𝑑𝑖𝑔𝑖𝑡]

6. Calculate the impedance of the cable per Km using the resistance and reactance

values from the datasheet assuming a power factor of 0.8 (i.e. Cos𝟇 = 0.8)

𝑍 = 𝑅 ∗ Cosϕ + 𝐿 ∗ Sinϕ

7. Calculate the voltage drop on the cable using all of the above data as follows:

𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑑𝑟𝑜𝑝 =√3 ∗ Z ∗ 𝐼𝑓𝑙 ∗ 𝑙𝑒𝑛𝑔𝑡ℎ(𝑚)

V(v) ∗ CableRuns ∗ 1000∗ 100 [%]

Since an arbitrary cable size was chosen based on the minimum, once the voltage

drop had been determined, one could go back and change either the size (hence the

impedance) or the number of cable runs to decrease the drop to an acceptable level.

Finally, using the above approach we will be able to perform the cable sizing

calculations.

We can start from a simple step: will size the cables for a case where we would use a

radial feeder distribution, in the civil sector (Figure 20)

Here we can see that there are 4 feeder cables, each corresponding to a separate load.

This means that we will need to calculate the voltage drop on each feeder, and size the

cables such that each would be < 2%. The calculations were performed using all of

the above mentioned formulas to produce the following:

Table 4: Cable sizing calculations for radial network

Load (kVA)

Voltage (V)

FL Current (A)

Length (m) Size (mm2 )

Cable Runs

Voltage Drop (%)

Feeders Airport 187 415 260.16 270 185 2 1.788294382

Telecom 321 415 446.58 200 185 2 2.273885905

Hospital 500 415 695.60 500 240 6 2.479798713

Sub P 300 415 417.36 370 240 3 2.202061257

Figure 20: Civil sector EPS SLD (Radial)

18

As we can see, by appropriately choosing the cable size and the number of runs, the

voltage drop resulted to match the required 2%.

Furthermore, we can summarize the chosen cables for this setup as follows:

Cable 1: 3 Runs of 1 Core x 240mm2 Cu/XLPE/SWA/PVC per phase (Sub P)

Cable 2: 2 Runs of 1 Core x 185mm2 Cu/XLPE/SWA/PVC per phase (Telecom)

Cable 3: 6 Runs of 1 Core x 240mm2 Cu/XLPE/SWA/PVC per phase (Hospital)

Cable 4: 2 Runs of 1 Core x 185mm2 Cu/XLPE/SWA/PVC per phase (Airport)

Here we can see that the feeder cable going to the Hospital substation would be an

expensive installation, because it would need at least 6 runs of 240mm2 XPLE cable.

In turn, we could have chosen a bigger cable to compensate for the number of runs,

but in that case we would have to deal with several runs of a 300mm2 cable, which is

likewise a complicated matter to deal with in terms of installation.

Afterwards, we can proceed to the cable sizing calculations for the ring distribution

networks which were earlier proposed to be used in the project, which we can then

compare to the feeder network cable sizing in order to justify our choice. Starting with

the civil sector (refer to Figure 18) we can see that in this case we would have to

select an appropriate size for 5 cables. To note, in a ring mains, the high full load

current which would have to account for all 4 loads together, hence logically it would

be divided to cables 1 & 5 almost equally. However, the whole principle of this

distribution type is to allow for a redundancy, i.e. if there is any fault on the side of

cable 1 for example, cable 5 would serve as an alternative route for the full current for

all of the loads. Hence we need to calculate the maximum load each of these cables

would experience not only in normal operation, but in case a fault occurs. To note,

maximum current would flow through one main branch only in case the other fails

(i.e. cable 1 or 5):

Table 5: Civil ring cable loading

C2 = 1000kVA C4 = 1121kVA

Cable 5 fails C3 = 687kVA Cable 1 fails C3 = 621 kVA

C4 = 187kVA C2 = 300 kVA

Hence here we will use the highest load values that will give the highest load current

that may pass through each cable (marked in bold in Table 5). Furthermore, we can

note that the length of the cable distance has decreased dramatically, because in this

case the cables run from bus to bus, as opposed to a dedicated cable from supply to

each load. We can see the excerpt of the calculations in Table 6.

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Table 6: Cable sizing for civil sector ring

Furthermore, we can summarize the chosen cable sizes for civil sector as follows:

Cable 1: 7 Runs of 1 Core x 120mm2 Cu/XLPE/SWA/PVC per phase





Here we immediately note that the cable cross-sections have decreased, while the

number of runs has increased. However, in cable sizing, it is known to better have

more runs of smaller cables, than less runs of greater ones, which is directly to

installation costs. Furthermore, here we notice a decrease in cable length, which

further boosts the appeal of a ring mains distribution system.

On the other hand we have the industrial sector with its ring mains distribution

network (as drawn in the schematic in Figure 19). We will use a similar approach by

first calculating the maximum possible loading for each cable in case of a fault. As

before, the highest ratings are marked in bold in Table 7.

Table 7: Industrial Ring cable loading

C2 = 454kVA C4 = 595kVA

Cable 5 fails C3 = 374kVA Cable 1 fails C3 = 408 kVA

C4 = 187kVA C2 = 328 kVA

Table 8: Cable sizing for industrial sector ring

Load (kVA) Voltage (V)

FL Current (A)

Size (mm^2) Runs

Length (m) Voltage Drop (%)

Ring mains Cable 1 1308 415 1819.70 120 7 200 3.573856459

Cable 2 1000 415 1391.21 95 5 170 3.886729569

Cable 3 687 415 955.76 95 3 120 3.141392016

Cable 4 1121 415 1559.54 185 10 550 4.367490202

Cable 5 1308 416 1815.32 120 8 270 4.192737896

Load (kVA) Voltage (V) FL Current (A) Size (mm^2) Runs Length (m) Voltage Drop (%)

Ring mains Cable 1 783 415 1089.31 150 6 350 3.759021338

Cable 2 454 415 631.61 120 4 390 4.233093628

Cable 3 408 415 567.61 185 5 750 4.335259109

Cable 4 595 415 827.77 150 4 300 3.672607055

Cable 5 783 416 1086.70 185 8 600 4.139960475

20

Finally, Table 8 shows the cable sizing calculations for the industrial sector ring. The

proposed choices can be summarized as follows:






In this fashion, two reliable emergency systems are provided, with relevant ease of

installation and optimum costs. On the other hand, the cabling could be further

reduced by increasing the number of gensets. For example, in the industrial sector, we

could install two gensets instead of one, one between Umm Shaif LER and Zakum

LER, and the second between the STOREX and CTU substations, thus heavily cutting

down on the length of the cable, and consequently, on the cross-sectional area, runs,

installation etc. But in the end, there are hundreds of possible system combinations,

and it is all up to the engineering judgement and choice. Finally, the proposed layout

may be seen in Figure 21 below, where the cable routing is denoted by black lines and

is numbered according to the previously provided SLDs.

At this stage, all of the proposed tasks and objectives have been addressed, most

viable solutions proposed, and the project itself can be considered done.

Figure 21: EPS layout

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5. Week VI

5.1 Das Island visit

The only offshore site we visited was the Das Island itself, which was

beneficial for me in particular, because I could examine the place I was working to

improve during my internship.

First, we took an airplane from Al Bateen airport to Das Island. There, we were met

by the company’s representatives, and invited for a brief presentations about safety on

site and the essential information about the island itself. Afterwards, we’ve visited the

central control room, where I could see electrical engineers at work, performing

routine checks and monitoring. Then, we went on a comprehensive tour of the

premises. Then, we were taken to the ADGAS-owned area of the island, and had a

tour of the plant. Finally, we had a lunch at a local restaurant, had a short tour of the

Das Island accommodations and went back to the airport to fly home.

To summarize, this was the only visit that was completely worth the time spent on it,

as we had a chance to see so many machines and plants in real-life environment and

had a chance to see how people work & live at offshore installations

5.2 Conclusion and recommendations

As far as the project is concerned, the following design approach is

recommended: the power supply should be either a fuel cell or a micro-turbine. This

would be a great technological advancement for the company, would address many

HSE issues of the project and would minimize the running costs. Even though the

capital requirements for the new technology is higher as opposed to the conventional

EDG sets, it is balanced out by the fact that the proposed distribution would only

require 4 power supply units in total, with reasonable expenditures on cabling.

Furthermore, I would strongly recommend to look into the maintenance procedures of

the emergency system. As it was evident from the IAR, the maintenance records are

often not taken, which may not necessarily be an evidence of neglected service, but

makes it harder to correctly evaluate the state of the electrical assets and carry out

necessary rectification. Finally, as evident from the report, such approach led to 8

emergency generators on Das Island being in a high risk of failure state, which is

completely unacceptable for an Emergency power system in Oil & Gas industry.

In general, my internship at ADMA-OPCO was a great experience. I’ve had the

chance to see how engineers go about their business, solve problems etc. Furthermore,

I’ve learned a lot of new information, commonly used abbreviations, company and

industry standards and finally I’ve become well-accustomed to the workplace flow

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6. References

[1] IEEE Recommended Practice for Emergency and Standby Power Systems for

Industrial and Commercial Applications, IEEE Std. 446-1995, December 1995.

[2] B. Brown, " Section 10: Emergency and Standby Power Systems", Schneider

Electric assets for engineers, vol. 1, pp. 4-10, 2008.

[3] J. May, "Why are we still using the internal combustion engine?",

Telegraph.co.uk, 2009. [Online]. Available:

http://www.telegraph.co.uk/motoring/columnists/jamesmay/5368889/Why-are-we-

still-using-the-internal-combustion-engine.html. [Accessed: 15- Jul- 2016].

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Appendices

Appendix A: Project Sheet

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Appendix B

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Appendix C

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Documents

Final report_Internship_ Fadi 5261 _