GE 745 Instruction Manual page 272

PROTECTION SCHEMES
7.5.10.5 Reset Time
7.5.10.6 Winding 2 or 3 elements
Note
NOTE
7–34
 Enter the expected operating times from the timing curve applied in the
settings.
 Using FIGURE 7–9: General test setup on page 7–25 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 Nominal time
1.5
3
5
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 triggering. To perform such a test, contact GEGE
Multilin for detailed test instructions.
A simple verification of the reset mode selected with the
W1 GND TIME OC W1 GROUND TIME OC RESET

FIGURE 7–9: General test setup on page 7–25. 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 "Linear", 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.
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
OVERCURRENT
 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.
CHAPTER 7: COMMISSIONING
Measured time
S4 ELEMENTS
setpoint is obtained using the setup in
(or W3 GROUND TIME OVERCURRENT
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUND OC
 
W2 GROUND TIME
) element.