10-20 Testing and Troubleshooting Date Code 20080110
SEL-387E Instruction Manual
Step 1.
Purpose: Determine the expected time delay for the restricted earth fault function.
Method: Execute the
SHOWSET
command via the relay front panel or serial port
and verify the element settings (i.e.,
SHO E321 <Enter>
).
Calculate the time delay to pickup (tp). Inverse-time elements are
calculated using three element settings and the operating time equations
shown in
Section 3: Protection Functions
. TD is the time-dial setting,
and M is the applied multiple of pickup current.
For example, 50GP = 0.5 A. The REF curve is type U4, extremely
inverse. The time dial is fixed at 0.5. Only the IRW3 current is used for
the time curve calculation. Setting IRW3 at 1 A represents a multiple of
pickup of M = 2.0. We can use the equation below to calculate the
expected operating time for curve U4 at M = 2, TD = 0.5:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−
+=
1M
67.5
0352.0•TDtp
2
ondssec963.0tp
=
Step 2.
Purpose: Set the Sequential Events Recorder to record the element timing.
Method: Use
SET R SER1 <Enter>
to set SER1 equal to the element pickup and
time-out Relay Word bits (i.e., 50G3, 32IF, and REFP). When prompted,
set SER2, SER3, and SER4 to NA. Save the settings.
Step 3.
Purpose: Connect and apply two single-current test sources to test the REF
element.
Method: Connect two single-current test sources as shown in
Figure 10.6, but with
Source Current 2 connected to one of the Winding 3 inputs (e.g., IAW3).
Set the IAW1 current magnitude to:
1CTR
3CTR
•GP50•21IAW ≥
Using the default CT ratios, IAW1 should be set to at least 2 • 0.5 A •
400/120, or 3.33 A. Set the magnitude of IAW1 to 4 A; set the angle of
IAW1 to 180 degrees.
Set the IAW3 current at 1 A at zero degrees. Since the currents are
opposite in phase, nothing should happen. Verify this as follows:
Execute the
TAR 38
command. Relay Word bits 50G3, 32IR, 32IF, and
REFP are all in this row. With the currents applied as above, 50G3
should be 1, and REFP should remain at 0. Bit 32IR should be 1,
indicating an external (reverse) fault. Bit 32IF should be 0.
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