<p><img alt="" src="https://edupmquestionhelp.s3.ap-south-1.amazonaws.com/hint/uploads/images/16255626991625562699.jpg" style="height:588px; width:800px" /></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px"><u>Example 5:</u> Figure 7.29 shows a single line diagram of a simple interconnected power system network. Relays R<sub>1</sub> to R<sub>4</sub> are directional normal inverse overcurrent relays wired for three overcurrent and one earth-fault units. Overcurrent units have the range 50-200 % of 1 amp in seven equal steps for setting. The ground units have the range 10-40 % of 1 amp in seven equal steps for setting. The loads at both the buses are shown in the figure. Fault currents for faults at F<sub>1</sub> and F<sub>2</sub> are tabulated below:</span></p>

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

<table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none; width:900px">
	<caption>
	<p><strong><span style="font-size:18px">Table 7.11: Fault Currents for Faults at F1 and F2</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:120px">
			<div style="text-align:center"><span style="font-size:28px">CT</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:120px">
			<div style="text-align:center"><span style="font-size:28px">Fault Current for Triple Line Fault at F<sub>1</sub> in Amp</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:120px">
			<div style="text-align:center"><span style="font-size:28px">Fault Current for Triple Line Fault at F<sub>2</sub> in Amp</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:120px">
			<div style="text-align:center"><span style="font-size:28px">Fault Current for L-g Fault at F<sub>1</sub> in Amp</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:120px">
			<div style="text-align:center"><span style="font-size:28px">Fault Current for L-g Fault at F<sub>2</sub> 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:120px">
			<div style="text-align:center"><span style="font-size:28px">CT<sub>1</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">6852</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1910</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:120px">
			<div style="text-align:center"><span style="font-size:28px">7933</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:120px">
			<div style="text-align:center"><span style="font-size:28px">2088</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:120px">
			<div style="text-align:center"><span style="font-size:28px">CT<sub>2</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">1410</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1910</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1633</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:120px">
			<div style="text-align:center"><span style="font-size:28px">2088</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:120px">
			<div style="text-align:center"><span style="font-size:28px">CT<sub>3</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">1410</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1910</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1633</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:120px">
			<div style="text-align:center"><span style="font-size:28px">2088</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:120px">
			<div style="margin-left:48px; text-align:center"><span style="font-size:28px">CT<sub>4</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">1410</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:120px">
			<div style="text-align:center"><span style="font-size:28px">5539</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:120px">
			<div style="text-align:center"><span style="font-size:28px">1633</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:120px">
			<p style="text-align:center"><span style="font-size:11pt">6059</span></p>
			</td>
		</tr>
	</tbody>
</table>

<p>&nbsp;</p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:14px">Assume that 10 % of power generated is used to run the auxiliaries. The phase relays R<sub>1</sub> to R<sub>4</sub> are voltage-controlled overcurrent relays such that their P. S. will reduce to 40 % of set value when voltage collapses below 70 % of rated value. The excitation current of all the CTs is 0.05 amp. Determine the settings of overcurrent and earth-fault units of relays R<sub>1</sub> to R<sub>4</sub>.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px"><strong><u>Solution:</u></strong> The operative direction of directional relays is shown by arrowheads in the figure.</span></p>

<p><span style="font-size:14px">Power-flow analysis: For phase relay R<sub>1</sub>/R<sub>2</sub>, considering single line contingency, the maximum possible load is 600 MW and the generation available is 0.9 ( 210 &times;&nbsp;3) or 567 MW. Hence, plug-setting of R<sub>1</sub>/R<sub>2</sub> is to be decided based on 567 MW.</span></p>

<p>&nbsp;</p>

<p><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;P.S. of R<sub>1&nbsp;</sub>or R<sub>2&nbsp;</sub></span></p>

<p><span style="font-size:14px"><sub>&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;</sub><span class="math-tex">\(=\frac{567\times 10^3\times 100}{\sqrt3\times220\times 0.85\times1500}\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">= 116.70 %. Hence, 125 % is selected.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Similarly, P. S. of R<sub>3</sub>/R<sub>4</sub> is to be decided based on 350 MW load [because the generation 0.9&nbsp;( 210 &times; 2)&nbsp;or 378 MW is more than the load) considering single line contingency.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">P.S. of R<sub>3&nbsp;</sub>or R4&nbsp;</span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(= \frac{350\times10^3\times100}{\sqrt3\times220\times0.85\times1000}\)</span>&nbsp;</span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">= 108.06 %. Hence, 125 %&nbsp;is selected.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<ol start="2">
	<li style="text-align:justify">
	<p><span style="font-size:14px">Fault Current Calculations: These are done and tabulated as given in table 7.11.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Primary-backup pairs: We do not need any computer algorithm to find out primary-backup pairs as it can be very easily seen in the figure. These are tabulated below:</span></p>
	</li>
</ol>

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

<table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none; margin-left:208px; width:900px">
	<caption>
	<p><span style="font-size:18px"><strong>Table 7.12: Primary-Backup pairs of Figure 7.29</strong></span></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:105px">
			<div style="text-align:center"><span style="font-size:28px">Primary Relay</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:103px">
			<div style="text-align:center"><span style="font-size:28px">Back-up Relay</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:105px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>1</sub></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:103px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>4</sub></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:105px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>2</sub></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:103px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>3</sub></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:105px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>3</sub></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:103px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>2</sub></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:105px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>4</sub></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:103px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>1</sub></span></div>
			</td>
		</tr>
	</tbody>
</table>

<p>&nbsp;</p>

<p>&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">It is interesting to note that R<sub>1</sub> and R<sub>4</sub> give back-up to each other. Similarly, R<sub>2</sub> and R<sub>3</sub> give back-up to each other.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<ol start="4">
	<li style="text-align:justify">
	<p><span style="font-size:14px">Calculation of Plug-Settings of Phase Relays: This is carried out at serial number 1 above.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Calculation of Time Settings of Phase Relays: As there is no last relay towards load in this system, we will start with any one relay at random, say relay R<sub>1</sub>. Consider the triple line fault at F<sub>1</sub>. </span></p>
	</li>
</ol>

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

<p style="text-align:justify"><span style="font-size:14px">PSM of R<sub>1&nbsp;</sub><span class="math-tex">\(=\frac{6852}{1.25\times1500\times0.4}\)</span></span></p>

<p style="text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 9.136.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;Top of R<sub>1&nbsp;</sub><span class="math-tex">\(=\frac{3}{log_{10}9.136}\times 0.1\)</span></span></p>

<p style="text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 0.3123 sec.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px">This is because we start with TMS of R<sub>1</sub> as 0.1. Hence, Top of back-up relay R<sub>4</sub> = 0.3123 + 0.25 = 0.5623 sec.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px">PSM of R<sub>4</sub> for fault at F<sub>1</sub></span></p>

<p style="text-align:justify"><span style="font-size:14px">&nbsp;<span class="math-tex">\(=\frac{1410}{1.25\times1000\times 0.4}\)</span>&nbsp; =&nbsp; 2.82.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;TMS&nbsp;of R<sub>4</sub></span></p>

<p style="text-align:justify"><span style="font-size:14px"><sub>&nbsp;</sub><span class="math-tex">\(=\frac{0.5623\times log_{10}2.82}{3}\)</span></span></p>

<p style="text-align:justify"><span style="font-size:14px">&nbsp; = 0.084.</span></p>

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

<p style="text-align:justify"><span style="font-size:14px">Therefore, TMS (R<sub>4</sub>) shall be set at 0.1, according to this calculation. But the setting exercise is yet not complete. One has to check that for fault at F<sub>2</sub>, R<sub>1</sub> backs up R<sub>4</sub> with these settings calculated.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">PSM of R<sub>4&nbsp;</sub>for fault at F<sub>2</sub>&nbsp;</span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp;<span class="math-tex">\(=\frac{5539}{1.25\times1000\times0.4}\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">=&nbsp; 11.078.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;Top of&nbsp;R<sub>4&nbsp;</sub></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(=\frac{3}{log_{10}11.078}\times 0.1\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">= 0.2872 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">PSM of R<sub>1&nbsp;</sub><span class="math-tex">\(= \frac{1910}{1.25\times1500\times 0.4}\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 2.55.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;Top of&nbsp;R<sub>1&nbsp;</sub>=&nbsp;<span class="math-tex">\(\frac{3}{log_{10}2.55}\times 0.1\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 0.7379 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Top of R<sub>1</sub> &ndash; Top of R<sub>4</sub> = 0.4507 sec, which is more than minimum discrimination time margin 0.25 sec. Thus, the setting exercise is through just in first iteration. But in certain networks, more than one iteration is required. This means that if the difference calculated above is less than 0.25 sec, TMS of R<sub>1</sub> will be required to be changed to 0.15, which will change TMS of R<sub>4</sub> also. Thus, after more than one iteration, one will arrive at optimal setting.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">In this example TMS of R<sub>1</sub>/R<sub>2</sub> = 0.1 and TMS of R<sub>3</sub>/R<sub>4</sub> = 0.1.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<ol start="6">
	<li style="text-align:justify">
	<p><span style="font-size:14px">Calculation of Plug-Settings of Ground Relays: We start with plug-setting of all ground relays R<sub>1</sub> to R<sub>4</sub> as 10 %.</span></p>
	</li>
	<li style="text-align:justify">
	<p><span style="font-size:14px">Calculation of Time Settings of Ground Relays: TMS of R<sub>1</sub> = 0.1. Fault current = 7933 amp.</span></p>
	</li>
</ol>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Secondary equivalent of this current = 5.28 amp. Therefore, current through the ground relay is equal to 5.13 amp.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;PSM of R<sub>1&nbsp;</sub><span class="math-tex">\(=\frac{5.13}{0.1}\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 51.3.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;Top of&nbsp;R<sub>1&nbsp;</sub><span class="math-tex">\(=\frac{3}{log_{10}20}\times 0.1\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 0.23 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Therefore, Top of R<sub>4</sub> = 0.48 sec. </span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">PSM of R<sub>4</sub> &nbsp;<span class="math-tex">\(=\frac{\frac{1633}{1000}-0.15}{0.1}\)</span></span></p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 14.83.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px"><span class="math-tex">\(\dot{.\hspace{0.095in}.}\)</span>&nbsp;TMS of&nbsp;R<sub>4&nbsp;</sub><span class="math-tex">\(= \frac{0.48\times log_{10}14.83}{3}\)</span></span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">TMS of R<sub>4</sub> = 0.1873, hence 0.2 is selected. But R<sub>1</sub> should back-up R<sub>4</sub>.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">PSM of R<sub>4</sub> for fault current 6059 amp (for fault at F<sub>2</sub>) = 59.09. Top of R<sub>4</sub> = 0.4611 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">PSM of R<sub>1</sub> for fault at F<sub>2</sub> = 12.42. Top of R<sub>1</sub> = 0.274 sec. Hence, R<sub>1</sub> does not back-up R<sub>4</sub>. Further iteration will improve the situation. Finally, if TMS of R<sub>1</sub> is adjusted at 0.85 and TMS of R<sub>4</sub> at 0.9,</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Top of R<sub>1</sub> for fault at F<sub>1</sub> = 1.9599 sec and Top of R<sub>4</sub> for same fault location = 2.3 sec, (discrimination time margin = 0.34 sec). For fault at F<sub>2</sub>, Top of R<sub>4</sub> = 2.075 sec and Top of R<sub>1</sub> for same fault location will be 2.33 sec, (discrimination time margin = 0.255 sec). Thus, we have achieved the result. But, yet if P. S. of R<sub>4</sub>/R<sub>3</sub> is adjusted at 10 % and P. S. of R<sub>1</sub>/R<sub>2</sub> at 15 %, the faster operating time is possible, yet maintaining the selectivity.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Plug-Setting of R<sub>1</sub>/R<sub>2</sub> = 15 %. Plug-Setting of R<sub>3</sub>/R<sub>4</sub> = 10 %. TMS of R<sub>1</sub>/R<sub>2 </sub>= 0.5. </span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">TMS of R<sub>3</sub>/R<sub>4</sub> = 0.55. Top of R<sub>1</sub> for F<sub>1</sub> = 1.153 sec. Top of R<sub>4</sub> for same fault location = 1.408 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Discrimination time margin is maintained at 0.255 sec. For fault at F<sub>2</sub>, Top of R<sub>4</sub> = 1.268 sec.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify"><span style="font-size:14px">Top of R<sub>1</sub> = 1.633 sec. Discrimination margin = 0.365 sec. It can be appreciated that the relays have operated faster by 0.8 sec by this change in settings. Yet, by trying different plug-settings and time settings of these four relays, the settings can be optimized. But right now, we stop here.</span></p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<table cellspacing="0" class="MsoTableGrid" style="border-collapse:collapse; border:none; margin-left:24px; width:900px">
	<caption>
	<p><strong><span style="font-size:18px">Table 7.13: Summary of Relay Settings of Example 5</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:120px">
			<div style="text-align:center"><span style="font-size:28px">Relay</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:120px">
			<div style="text-align:center"><span style="font-size:28px">P. S. of Phase Relay in % of 1 Amp</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:120px">
			<div style="text-align:center"><span style="font-size:28px">TMS of Phase Relay</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:120px">
			<div style="text-align:center"><span style="font-size:28px">P. S. of Ground Relay in % of 1 Amp</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:120px">
			<div style="text-align:center"><span style="font-size:28px">TMS of Ground Relay</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:120px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>1</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">125</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.1</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:120px">
			<div style="text-align:center"><span style="font-size:28px">15</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.5</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:120px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>2</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">125</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.1</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:120px">
			<div style="text-align:center"><span style="font-size:28px">15</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.5</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:120px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>3</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">125</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.1</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:120px">
			<div style="text-align:center"><span style="font-size:28px">10</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.55</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:120px">
			<div style="text-align:center"><span style="font-size:28px">R<sub>4</sub></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:120px">
			<div style="text-align:center"><span style="font-size:28px">125</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.1</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:120px">
			<div style="text-align:center"><span style="font-size:28px">10</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:120px">
			<div style="text-align:center"><span style="font-size:28px">0.55</span></div>
			</td>
		</tr>
	</tbody>
</table>

<p>&nbsp;</p>

<p>&nbsp;</p>

<p>&nbsp;</p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>

<p style="margin-left:24px; text-align:justify">&nbsp;</p>