Table of Contents
Advertisement
10.6 PROTECTION SCHEMES
c) OPERATING TIME
Using a table like the one shown blow, select 3 or 4 values of current multiples at which the timing is to be mea-
sured. Enter the expected operating times from the timing curve applied in the settings. Using Figure 10–9:
GENERAL TEST SETUP on page 10–21 with the Interval Timer enabled, set the current level to the desired
value and apply suddenly by closing the double-pole switch. Record the operate time and compare to the
expected value. Repeat for the all the desired values of current.
CURRENT
MULTIPLE
1.5
3
5
d) RESET TIME
A precise measurement of the reset time requires a relay test set capable of dynamic operation, with three
sequenced stages, each with programmable current levels and time duration, and flexible external contact trig-
gering. To perform such a test, contact GE Power Management for detailed test instructions.
A simple verification of the reset mode selected under:
SETPOINTS/S4 ELEMENTS/GROUND OC/W1 GND TIME OC/W1 GROUND TIME OC RESET
is obtained using the setup in Figure 10–9: GENERAL TEST SETUP on page 10–21. The procedure consists
of repetitive operating time measurements in quick succession. If the reset is selected for Instantaneous , the
operating time always equals the nominal time derived from the selected curve. If the reset is selected as Lin-
ear , the operating time varies as a function of the time between successive applications of the current signal. If
this test is performed at current multiples of 2 to 3 times the pickup level, the variations in operating time are
easier to detect.
e) WINDING 2 OR 3 ELEMENTS
Because the second Ground Time Overcurrent element could be set with completely different parameters than
the element for the first winding, it is necessary to repeat the full set of tests described above for each winding.
To test the second element, disable all protection elements except for the W2 GROUND TIME OVERCURRENT (or
W3 GROUND TIME OVERCURRENT) element. Connect the current signal to X = F12 and Y = E12. Repeat all the
tests described for the Winding 1 Ground Time Overcurrent element in this section.
The blocking from logic input, if enabled, can be tested as described in earlier tests for other
elements.
NOTE
This procedure verifies that the Ground Instantaneous O/C performance matches the in-service settings. Set-
tings for these elements are found under:
SETPOINTS/S4 ELEMENTS/GROUND OC/W1 GND INST OC 1/...
If your relay settings require you to test at current multiples of several times the rated CT secondary value do
not leave the current signal on for more than a few seconds.
10
a) WINDING 1 ELEMENT
10-28
NOMINAL
MEASURED
TIME
TIME
745 Transformer Management Relay
10.6.11 GROUND INSTANTANEOUS OVERCURRENT 1
10 COMMISSIONING
GE Power Management
Advertisement
Table of Contents
