- Relay Word Bits and Other Settings Affected
Zone 1 must be less than Zone 2 and Zone 3. The Z1P and ZlG bits in the Relay Word
depend on the Z1 % setting.
Zone 2 Reach Setting (Z2%)
The Zone 2 phase and ground distance elements provide coverage for end-of-section faults.
The time delay allows coordination between the Zone 2 element of this relay and the Zone 1
element of the next relay in the forward direction.
Zone 2 elements should never extend past the Zone 1 reach of the next line terminal. This
prevents race conditions between Zone 2 time delayed elements of the two line terminals.
Typical settings for the Zone 2 distance elements are 120 - 130% of the protected line.
The Zone 2 elements must have adequate reach to detect all phase and ground faults along
Line 2, but cannot overreach the Breaker 5 Zone 1 elements for faults on Line 3.
Zone 2 element settings with a reach of 120% of protected line impedance account for the
effects of infeed. This point must be verified using a fault study to calculate the apparent
ohms at the local terminal for a fault at the remote end of the transmission line. In the
example system, 120% is selected for the Zone 2 elements with assurance that all phase faults
on Line 2 are detectable, even with infeed from the remote terminals.
Assuming Breaker 5 Zone 1 reach is set for 80% of the line impedance of Line 3, verify that
a Zone 2 reach of 120% for Breaker 3 does not overreach the Zone 1 elements at Breaker 5.
When Zone 2 at Breaker 3 has a set reach of 120%, the effective reach is:
Since 97.39
Ω
< 113.62
Ω,
the Zone 2 setting of 120% at Breaker 3 does not overreach the
Zone 1 protection of Line 3. Any effect of infeed tends to increase the apparent ohms seen at
Breaker 3 for faults on Line 3.
The MTA setting applies to all of the distance elements and is the same as the positive-
sequence line angle. Calculate the diameter of the Zone 2 mho circle with the following
equation:
For this example, the Zone 2 mho circle diameter along the MTA becomes:
5-14
Applications
SEL-221F, -1 Instruction Manual
Date Code 921110
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 ...