Date post: | 16-Feb-2017 |
Category: |
Documents |
Upload: | fadi-al-zir |
View: | 20 times |
Download: | 2 times |
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
ii
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.
iii
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.
iv
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
vi
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
1
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
10
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
11
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
12
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.
13
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.
19
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
Cable 2: 5 Runs of 1 Core x 95mm2 Cu/XLPE/SWA/PVC per phase
Cable 3: 3 Runs of 1 Core x 95mm2 Cu/XLPE/SWA/PVC per phase
Cable 4: 10 Runs of 1 Core x 185mm2 Cu/XLPE/SWA/PVC per phase
Cable 5: 8 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:
Cable 1: 6 Runs of 1 Core x 150mm2 Cu/XLPE/SWA/PVC per phase
Cable 2: 4 Runs of 1 Core x 120mm2 Cu/XLPE/SWA/PVC per phase
Cable 3: 5 Runs of 1 Core x 185mm2 Cu/XLPE/SWA/PVC per phase
Cable 4: 4 Runs of 1 Core x 150mm2 Cu/XLPE/SWA/PVC per phase
Cable 5: 8 Runs of 1 Core x 185mm2 Cu/XLPE/SWA/PVC per phase
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
21
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
22
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].
23
Appendices
Appendix A: Project Sheet
24
Appendix B
25
Appendix C
26