<p style="text-align:justify"><img alt="" src="https://edupmquestionhelp.s3.ap-south-1.amazonaws.com/hint/uploads/images/16257236801625723680.jpg" style="height:453px; width:800px" /></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px">Figure 7.42 shows a single line diagram of portion of a power system network. The table below gives the magnitude of the earth-fault current for L-g fault at different buses.</span></p>

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<p style="text-align:justify">&nbsp;</p>

<p style="margin-left:48px; text-align:center">&nbsp;</p>

<table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none; margin-left:189px; width:900px">
	<caption>
	<p><strong><span style="font-size:18px">Table 7.18: Fault Currents for L-g Fault at Buses</span></strong></p>
	</caption>
	<tbody>
		<tr>
			<td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:136px">
			<div style="text-align:center"><span style="font-size:28px">Bus</span></div>
			</td>
			<td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:1px solid black; vertical-align:top; width:148px">
			<div style="text-align:center"><span style="font-size:28px">Fault Current for L-g Fault in Amp</span></div>
			</td>
		</tr>
		<tr>
			<td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:136px">
			<div style="text-align:center"><span style="font-size:28px">A</span></div>
			</td>
			<td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:148px">
			<div style="text-align:center"><span style="font-size:28px">2320</span></div>
			</td>
		</tr>
		<tr>
			<td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:136px">
			<div style="text-align:center"><span style="font-size:28px">B</span></div>
			</td>
			<td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:148px">
			<div style="text-align:center"><span style="font-size:28px">1504</span></div>
			</td>
		</tr>
		<tr>
			<td style="border-bottom:1px solid black; border-left:1px solid black; border-right:1px solid black; border-top:none; vertical-align:top; width:136px">
			<div style="text-align:center"><span style="font-size:28px">C</span></div>
			</td>
			<td style="border-bottom:1px solid black; border-left:none; border-right:1px solid black; border-top:none; vertical-align:top; width:148px">
			<div style="text-align:center"><span style="font-size:28px">2173</span></div>
			</td>
		</tr>
	</tbody>
</table>

<p style="margin-left:48px; text-align:justify">&nbsp;</p>

<p style="margin-left:48px; text-align:justify">&nbsp;</p>

<p style="margin-left:48px; text-align:justify"><span style="font-size:14px">The other data required is as follows:</span></p>

<p style="margin-left:48px; text-align:justify">&nbsp;</p>

<p style="margin-left:48px; text-align:justify">&nbsp;</p>

<ul>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Each relay group R<sub>1</sub>, R<sub>2</sub> and R<sub>3</sub> is wired for three overcurrent and one earth-fault protection scheme.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Ground relays R<sub>1</sub>, R<sub>2</sub> and R<sub>3</sub> are normal inverse IDMT overcurrent relays with in-built instantaneous high-set units. The setting range for IDMT unit is 10-40 % of 1 amp in seven equal steps and that for instantaneous unit is 400-2000 % of 1 amp in steps of 50 %.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">P. S. and TMS of R<sub>3</sub> are 10 % and 0.1 respectively.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">% overreach of instantaneous high-set unit is 10 %.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Instantaneous time of operation of high-set unit is 0.06 sec.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Time of operation of a relay beyond PSM equal to 20 is definite and constant as 2.3 seconds at TMS equal to 1.0.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Excitation current of all CTs is 0.03 amp.</span></p>
	</li>
</ul>

<p>&nbsp;</p>

<p><span style="font-size:14px"><strong>&nbsp;TMS of ground relay R<sub>2</sub> shall be set at</strong></span></p>

<p style="margin-left:48px; text-align:justify">&nbsp;</p>

<p style="text-align:justify">&nbsp;</p>

<p style="margin-left:168px; text-align:justify">&nbsp;</p>