To calculate the ground distance element reach, first calculate the residual
current compensation factor, K0.
K0 = (Z0 - Z1)/(3 x Z1)
Where:
Z0 = R0 + jX0
Z1 = R1 + jX1
For the example relay settings, K0 is calculated:
K0 = [(41.5 + j248.57) - (13.9 + j79.96)]/[3 x (13.9 + j79.96)]
K0 = 0.70
0.57°
Next, calculate the applied residual current by summing the three phase
currents.
IR = IA + IB + IC
For the test above,
IR = 3.13 A
∠−80.1°
+ 0.0 A
∠
0.0° + 0.0 A
∠0.0°
IR = 3.13 A
∠−80.1°
Zone 1 reach secondary along the MTA,
In primary ohms,
Zone 1 reach primary along the MTA,
primary
Where PTR = 2000 and CTR = 200.
7.
Find two other convenient test points. Consider a square inscribed in a mho
circle with one diagonal being the diameter along the MTA. The two corners
of that square on the other diagonal are reached by increasing the current by a
factor of 1.414 at angles of ±45° from the angle obtained using the ONEBUS
program.
For our Zone 1 AG phase-ground example, the required voltages remain
unchanged. The current magnitudes are (3.13)(1.414) = 4.43 amperes at the
angles listed as follows:
Date Code 920508
Maintenance & Testing
SEL-221F, -1 Instruction Manual
7-27
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Summary of Contents for SEL-221F
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Page 110: ...Example Event Report 2 4 12 Event Reporting SEL 221F 1 Instruction Manual Date Code 930830 ...
Page 158: ...SETTINGS SHEET FOR SEL 221F RELAY PAGE 2 OF 6 DATE Date Code 921110 ...
Page 160: ...SETTINGS SHEET PAGE 4 OF 6 FOR SEL 221F RELAY DATE Date Code 930601 ...
Page 161: ...SETTINGS SHEET PAGE 5 OF 6 FOR SEL 221F RELAY DATE Date Code 961208 ...
Page 229: ...SEL 200 Series Relay Main Board Troubleshooting Test Points and Jumper Locations ...