Where K = (Z0 - Z1)/(3 x Z1)
and
0.0833 < ¦K¦ < 2.0
47° < MTA
+ ∠Κ
< 113°
Given the impedance settings selected,
K = 0.702
∠0.57°
You should perform a cursory check to be sure the minimum Zone 1, Zone 2, or Zone 3
secondary reaches at MTA are not below the minimum distance element reach setting of
0.125
Ω
secondary or above the maximum setting limit of 64
Ω
secondary.
- Other Settings Affected
Z1%, Z2%, Z3%, MTA
Current and Potential Transformer Ratio Selection
Current transformer ratio (CTR) selection for line protection is often based on the
transmission line current carrying capability. CTR selections also determine the magnitude of
secondary fault current presented to the relay.
Select a current transformer ratio which reduces the likelihood of CT saturation and allows
the current transformer to deliver a reliable secondary representation of the primary current
during a fault condition.
The potential transformer ratio (PTR) setting should be selected to match the primary voltage
ratio (l-n) to approximately 67 V
l-n
.
The synch-check potential transformer ratio (SPTR) setting should be selected to allow the
synch-check voltage input to range between 67 V
l-n
and 120 V
l-n
.
The current transformer ratio selected for this example is 1000/5 or 200:1. This ratio allows
1000 A of load to flow without exceeding five amperes of secondary current, while limiting
the secondary current to well below 50 A for the maximum available fault duty.
The system voltage is 230 kV line-line or 132.8 kV line-neutral. The relay requires a
nominal phase voltage of approximately 66.4 V
l - n
or 115 V
l - l
. The PTR selected for this
example is 2000:1.The synch-check potential transformer uses the same ratio.
5-6
Applications
SEL-221F, -1 Instruction Manual
Date Code 920508
Summary of Contents for SEL-221F
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Page 69: ...Date Code 920508 Specifications SEL 221F 1 Instruction Manual 2 44 ...
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Page 72: ...Date Code 920508 Specifications SEL 221F 1 Instruction Manual 2 47 ...
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 ...