Schweitzer Engineering SEL-387-0, Instruction Manual

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10.18
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Testing and Troubleshooting
Acceptance Testing
Step 6. Purpose: Repeat the test for 51NC1, 51PC2, and 51NC2.
Method:
a. Repeat Step 1 through Step 4 for the other elements.
b. Remember to set the SER for the appropriate elements
and apply current to the appropriate windings.
c. Also remember to disable the pickup of the
complementary element in each set, so that only the
phase or residual element is being tested at one time.
Restricted Earth Fault
(REF) Function
The test for the REF function is similar to that for the combined overcurrent
element–using two current sources to inject current into two different
windings. Small currents are used to demonstrate the sensitivity of the element
to internal ground faults. The test assumes a 5 A relay is being used.
The settings for the REF function are the following:
Set:
E32I = 1 E32I = Enabling SEL
OGIC
control equations
32IOP =
1
32IOP = Winding(s) for obtaining the Operate quantity
Use default setting:
a0 =
0.1
a0 = Positive-sequence restraint factor
50GP =
0.5 A
50GP = Residual current sensitivity level
Recall that the default CT ratio settings are: CTR1 = 120, and CTR4 = 400.
If the ratio CTRmax/CTR4 is greater than 2.0, set 50GP equal to 0.25 A times
the actual ratio of CTRmax/CTR4.
Step 1. Purpose: Determine the expected time delay for the overcurrent
element.
Method:
a. Execute the SHO command via the relay front panel or
serial port and verify the element settings (i.e., SHO
E32I <Enter> ).
b. 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:
Differential, Restricted Earth Fault, Thermal, and
Overcurrent Elements
. 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 IRW4 current is used for the time curve calculation.
Setting IRW4 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:
Equation 10.3
NOTE:
To use the setting 5OGP = 0.5,
be sure that the ratio CTRmax/CTR4
is not more than 2.0, where CTRmax is
the greater of CTR1 or CTR4. Using
the default CT ratio settings,
CTRmax = CTR4, so the ratio
CTRmax/CTR4 =1. Therefore, the
50GP setting can remain at 0.5 A.
tp TD 0.0352
5.67
M
2
1
–
---------------- +
 
 
• =
tp 0.963 seconds
=