Department of Mechanical Engineering

Coursework Assessment Brief Coversheet

Assessment Information

Module Code: MECH0053

Module name: Power Transmission and Auxiliary Machinery Systems

Academic Year: 2025/26

Term: Term 1

Individual/Group: Individual

Word count or page count limit (if applicable): 10 Pages, 750 Words for Q2

% contribution to module: 25%

Submission Date

Please see the submission portal on Moodle for the due date for this assessment.

Word count or page count penalty

Work that exceeds the word/page count by more than 10% will be reduced by 10 percentage points. This must not take the mark below the Pass Mark. Any material in addition to the 10% excess may not be taken into account in grading.

Eligibility for Delayed Assessment Permit (DAP)

This assessment is eligible for Delayed Assessment Permit.

Mitigation available: 5 working days.

Use of Generative AI

This assignment is classified as Category 2: AI tools can be used in an assistive role. Further details outlining what you can and cannot use AI for can be found in the full assessment brief.

Assessment Brief

Use of AI:

Category 2:"AI tools can be used in an assistive role”. Students are permitted to use AI tools to assist with giving feedback on content, or proofreading content and the creation and formatting of figures, but the design and technical content is the student’s responsibility and must be their individual contribution.

If you have used AI in any way, you need to declare it in the report or presentation in the following way:

• Name and version of the generative AI system used, e.g. ChatGPT-3.5

• Publisher (company that made the AI system); e.g. OpenAI

• Brief description (single sentence) of context in which the tool was used.

More details are given here:

https://library-guides.ucl.ac.uk/referencing-plagiarism/acknowledging-genAI

Assessment Criteria

Mark Range                         Expected Standard

80-100

Outstanding submission that demonstrates a deep understanding of a wider range of topics. All calculations are accurate, and values provided to an appropriate level of precision. Parameters and examples are chosen with great insight and fully justified. Presentation is impeccable, of publishable standard: phrasing is concise and precise, and figures are perfectly formatted and labelled, providing information efficiently and in full detail with descriptive informative legends and with cross-reference to the text.

70-79

Excellent work, subjected to a rigorous quality assessment that addresses main concepts and theories. All calculations are accurate, and justification is given for choices of parameters and/or assumptions made. Wider knowledge and understanding of the meaning of the work is demonstrated; discussions are thoughtful, and conclusions are appropriate and fully justified. Text is concise and precise, and figures are clear, fully and accurately labelled and described in the text and legends.

60-69

Good quality work with some exceptions, for example a few minor mistakes in calculations or weak justification for some of the chosen parameters or examples. Values are provided to an appropriate level of precision, final answers are clearly distinguishable, and working is shown, with some attempt at reasoning or justification included. Figures are useful and correct though may benefit from some additional labelling, formatting and/or more-specific description.

50-59

Acceptable submission where the majority of the goals of the assignment have been understood and tackled, demonstrating that some key engineering principles have been applied correctly. Some calculations show minor mistakes, lack of explanation, or are attempted using incorrect methods. Justifications may be weak or missing in the descriptions of engineering decisions, methods, and conclusions.

30-49

Submission showing attempts at answering the assignment but with many gaps in knowledge and only limited understanding being demonstrated through text, figures and calculations. Sections of the assignment may be left unanswered. Many calculations exhibit major mistakes; many methods are incorrect or missing.

0-29

A submission demonstrating major gaps in understanding the assignment, failing to meet the majority of the assignment’s goals. Solutions are largely incomplete and show major mistakes and/or lack of the required knowledge.

General guidance and tips for success

There is an upper limit of 10 pages for this coursework, (excluding a title page and references if required). Pages must be typed and should be numbered, and the font should be no smaller than 11 to make the document easier to read and mark. There is no word limit for Question 1 as it is mainly analytical, but you should not exceed 750 words for Question 2. Do not use valuable space by including any data that has been given to you within this document and the associated data tables. All the information that you require to fully answer the two questions has been provided within the lecture material and documentation and there is no need to reference this information. If you do use external material, then this should be referenced in accordance with UCL requirements. This assignment has a weighting of 25% of the total module mark and is therefore expected to take approximately 7.5 hrs to complete.

It is essential to read and answer the questions and to ensure that all aspects are addressed. Working methods need to be clearly presented so that markers can credit your work even if the answers are not fully correct. Ensure that your work is presented in a professional way and that any figures used are labelled correctly. Ensure that you use all the 10 pages in the most efficient way to ensure that you present all the information that you need to answer the questions.

When answering Question 2, it is important that you don’t stray away too much from the lecture material, even though it may be entirely relevant. This is to ensure a consistent marking review. It is essential that you demonstrate your individual understanding and application of your chosen considerations and how the associated benefits can be derived, using practical examples to enhance your answers. It is important to stress that most of the available marks will be allocated to the production of this deeper understanding and demonstration of your knowledge, rather than just quoting the lecture material.

Question 1   75 Marks

1a   Substation Equipment Systems Engineering [30 Marks]

You are the Electrical Engineering Project Manager for a power upgrade project that involves the installation and commissioning of two new electrical substations that are used to provide a traction supply to an extension to the railway. You have prepared a contract specification, and you have sent this to prospective contractors to tender. These tenders have been returned and the key information associated with the costs, reliability and maintainability are provided on the Substation Systems Engineering Data Table that is allocated to you. This table provides details of four key sub systems in two electrical substations. The four sub systems comprise High Voltage (HV) Switchboards, Electrical Protection Systems, Rectifier Transformers (RTx) and DC Switchboards, types A and B, which come from different suppliers. These systems are connected as shown in Figure 1, with the protection system overlaid over the entire substation. The two substations are connected to two separate Bulk Supply Points (BSP) as shown in Figure 2, which also shows the DC connections to the traction section of the railway. The normal arrangement is to supply the track section from both ends (double end fed) to increase the reliability of the system. However, the system will operate on a single circuit risk, when the DC section is single end fed from one, or other, end. A substation systems engineering data table has been produced and details are available within a separate excel file. The project scope and the equipment list/details are provided in Table 1 below: -

Table 1: Substation Details

The project is in the early assessment stage of its development life cycle and at this stage there are two system choices, from different suppliers, suppliers X and Y. Each of these two choices has a different data profile and the project has a systems engineering budget allocation made up of a combination of dimensions: This information is available in a separate excel spreadsheet.

(a) Design Data

• Unit cost of manufacture (£m) (CAPEX)

• Reliability - Mean Time Between Failures (MTBF) for the chosen solution for each asset, measured in operating hours which can be assumed to be 8000 hours per annum.

• Mean Time to Repair (MTTR) data for each asset, measured in hours

• Mean Time Between Service (MTBS) data for each asset, again measured in hours.

• Labour resources required for breakdown (defect) and service (planned) maintenance.

You should also calculate the following, providing comprehensive details of your calculations that demonstrates how the results are obtained: -

• CAPEX

• Overall MTBF for each substation

• Maintainability (Total Maintenance hours / Operating hours)

• Number of failure (breakdown) hours per annum associated with both substations.

• Number of service (planned maintenance) hours per annum associated with both substations

• Total cost of Maintenance over 40 years (OPEX) [ Breakdown and Planned Maintenance]

1b   Substation Equipment Reliability and Availability Analysis [30 Marks]

You should also calculate the following, providing comprehensive details of your calculations that demonstrates how the results are obtained: -

• Reliability and MTBF of the combined HV supply to each Substation.

• Reliability of the DC supply from each substation, (i.e. combination of HV Supplies, HV Switchboard, Protection system, Rectifier Systems (2oo3) and DC Switchboard) and the estimated traffic hours downtime of each supply.

• Overall DC Supply reliability and MTBF at the DC traction system with both substations in service and an estimation of the total period(s) of cessation of the DC traction supply and the estimated availability of the DC supply over a period of 1 year.

• Service Deficiency Payments (SDPs) associated with the DC Supply over 40 years

• Total Life Cycle Costs (LCC) over 40 years, including CAPEX, OPEX and SDPs

1c   Analysis, discussion and conclusions [15 Marks]

You should generate two system options, one using the equipment from supplier ‘X’ and the other using supplier ‘Y’. You should then compare the results of your calculations against the user specification data provided. Please ensure that all your results are recorded in the results data table that is contained within the excel file that is provided.

You should then discuss the performance of both options compared with the budget systems engineering specification and select your chosen option, along with your reasoning and justification.

As this is a real world problem, it may not be possible to meet the allocated budget in every dimension and this may require some trade-offs, some of which will be over and others under budget. However, all choices should be close to the performance targets. Please note there is no single “textbook answer”. Answers will be judged on the choices made, the quality of the quantification and analysis and the logic supporting your final choice.

You are given the following information and assumptions that you can use to simplify the calculations associated with Question 1.

a. There is a total of 2 Substations.

b. The planned in-service lifetime is 40 years for all the equipment.

c. Each equipment item will remain in service for an average of 8,000 operating hours per year.

d. Total labour rates for maintenance are costed at £150 per hour. These rates include the direct labour cost plus all related overheads and spares and equipment.

e. The cost of installation of the new equipment is included in the capital costs provided.

f. The additional cost of a commissioning engineer to oversee the final testing and commissioning into service is £20k per substation.

g. In order to optimise spares holdings, documentation, familiarisation and training, the same plant options should be applied to both substations.

h. It can be assumed that the substation buildings are provided by a separate contractor.

i. Servicing will be planned to be undertaken during engineering hours (i.e. not operational railway periods) and will therefore not impact on the overall availability of the system. Engineering hours are planned from 01:00 to 05:00 each day.

j. Service Deficiency Penalty (SDP) payments will be due when the DC supply is deficient, i.e. when there is a total cessation of supply. These will be applied at a rate of £50k per hour.

k. It can be assumed that any breakdown that occurs will impact the DC supply, except that associated with a rectifier failure, when a single failure will not impact the dc supply, noting that a 2oo3 calculation as outlined in section 1.1.1 below is applied.

You will need to make other assumptions, for which marks may be awarded. Please detail each assumption and your reasoning. This is particularly the case when you calculate the period of downtime, as there are a number of valid assumptions that can be applied.

1.1   Specific Plant Data

1.1.1   Rectifier Transformers

Typically, Traction Rectifiers are capable of continuous operation at 100% rated capacity, 150% of rated capacity for 2hrs, with superimposed cycles of 5 x 1-minute periods at 300% rated capacity, followed by one period of 450% of rated capacity for 15 seconds. As this is the case, two rectifiers are capable of supplying the system load and it will therefore be necessary to apply a 2oo3 calculation associated with the calculation of overall rectifier reliability.

1.1.2   HV and DC Switchboards

Normally both the HV and DC Switchboards would be separated into a number of separate bus sections. This increases availability and redundancy as sections can be switched out and isolated to allow work to be completed without losing supplies from the substation. In this case these have been removed to make the analysis easier, but it should be noted that this approach provides a more pessimistic solution.

Question 2   Key ‘In-service’ RAM Engineering and Management Actions [25 Marks]

Imagine that you have now been appointed as Operations and Maintenance Manager, responsible for the long-term asset management of the plant associated with Q1. In this role, you are responsible for both the reliability and cost of ownership of your chosen system, throughout its ‘in service’ life.

Select TWO important considerations associated with the practical engineering and your management actions that you propose should be taken during the ‘in-service life, to increase system performance, giving your reasoning for each. Ensure that you cover areas that will impact on in-service reliability and any shortfall in the chosen system’s performance compared with the Systems Engineering budget. This will include measures to improve the reliability and availability of the plant, whilst reducing the cost of operation. Practical examples of how these measures would be implemented along with details of the benefits realised should be provided.

Figure 1 Schematic Arrangement of two Traction Substations supplying a section of the railway

Figure 2 Schematic network arrangement of two Traction Substations supplying a section of the railway