MODULE TITLE : ELECTRICAL SUPPLY AND DISTRIBUTION SYSTEMS TOPIC TITLE : FAULTS ON THE SUPPLY SYTEM AND PROTECTION SYSTEMS TUTOR MARKED ASSIGNMENT 4 NAME........................................................................................................................................ ADDRESS ................................................................................................................................. ................................................................................................................................................... ................................................................................................................................................... ...................................................... HOME TELEPHONE ..................................................... EMPLOYER.............................................................................................................................. ................................................................................................................................................... ................................................................................................................................................... ...................................................... WORK TELEPHONE...................................................... ESD - 4 - TMA (v1) © Teesside University 2011 THIS BOX MUST BE COMPLETED Student Code No. .................................................................................................... Student's Signature .................................................................................................. Date Submitted ........................................................................................................ Contact e-mail .........................................................................................................Published by Teesside University Open Learning (Engineering) School of Science & Engineering Teesside University Tees Valley, UK TS1 3BA +44 (0)1642 342740 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the Copyright owner. This book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, re-sold, hired out or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser.IMPORTANT Before you start please read the following instructions carefully. 1. This assignment forms part of the formal assessment for this module. If you fail to reach the required standard for the assignment then you will be allowed to resubmit but a resubmission will only be eligible for a Pass grade, not a Merit or Distinction. You should therefore not submit the assignment until you are reasonably sure that you have completed it successfully. Seek your tutor's advice if unsure. 2. Ensure that you indicate the number of the question you are answering. 3. Make a copy of your answers before submitting the assignment. 4. Complete all details on the front page of this TMA and return it with the completed assignment including supporting calculations where appropriate. The preferred submission is via your TUOL(E) Blackboard account: https://eat.tees.ac.uk 5. Your tutor's comments on the assignment will be posted on Blackboard. 1 Teesside University Open Learning (Engineering) © Teesside University 20111. FIGURE 1 shows four generators feeding into a sectionalised busbar with a fault limiting reactor. FIG. 1 Each generator is rated at 11 kV and 30 MVA and has a reactance of 0.2 p.u. Calculate the value of the reactance to limit the fault level on a feeder to 500 MVA. 2. FIGURE 2 shows the sectionalised busbar of a two generator power station connected to the national grid. Calculate, using a 40 MVA base, the fault level for a 3-phase symmetrical short circuit on the 11 kV feeder. B X R Y B Fault Loads A C D 2 Teesside University Open Learning (Engineering) © Teesside University 2011FIG. 2 3. State: (i) The function of a plug bridge on an IDMT electromagnetic protection relay. (ii) Two ways in which the setting of an IDMT electromagnetic relay may be altered. R Y B Fault 2 × 40 MVA 0.14 p.u. 0.31 p.u. on 40 MVA 11 kV Grid-in-feed 1500 MVA 132 kV 2 × 15 MVA 0.12 p.u. 3 Teesside University Open Learning (Engineering) © Teesside University 20114. (a) An 11 kV, single phase system is protected by a scheme using 1000/5 CTs and an IDMT relay having a plug setting of 150% and time multiplier setting of 0.68 (FIGURE 3). Using the standard PSM/time characteristic, find the relay operating time (TMS = 1) for a 236 MVA fault. FIG. 3 (b) The circuit breakers CB1, CB2, CB3 and CB4 are part of a scheme which uses 1000/5 CTs and IDMT relays. If the maximum fault current capability is 6700 amps, clearance of which must be initiated in 2.25 secs, select, using the standard characteristic: (i) plug setting multipliers for CB1 at plug settings of 100% and 50% (ii) the time multiplier setting of each IDMT relay to afford effective discrimination of 0.4 sec at a plug setting of 50%. Fault CB 1 Load A CB 2 CB3 Load B Load C CB 4 4 Teesside University Open Learning (Engineering) © Teesside University 2011Teesside University Open Learning (Engineering) © Teesside University 2011 Question No.