7–28 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION SCHEMES CHAPTER 7: COMMISSIONING
Reduce the current until the element resets.
The reset level should be 97% of the operate level. When the element
resets, the Trip and Phase LEDs should remain on if the
W1 PHASE INST
OC 1 TARGET was selected as Latched. Otherwise, only the Trip LED
should stay on.
Reset indicators and clear messages.
7.5.5.4 Operating Time
Using the setup shown in FIGURE 7–9: General test setup on page 7–
25 and the Interval Timer enabled, set the current level to 1.5 times the
operating level of the element.
Apply current suddenly by closing the double-pole switch.
Record the operate time and compare it to the
S4 ELEMENTS PHASE
OC
W1 PHASE INST OC 1 W1 PHASE INST OC 1 DELAY setpoint
value.
7.5.5.5 Phase B and C Elements
If the phase A element performed correctly and met specifications, repeat the pickup level
portion of the above test for phases B and C of winding 1. For phase B, X = H2 and Y = G2.
For phase C, X = H3 and Y = G3. The displayed message should change to indicate the
correct phase, winding, and element that operated.
7.5.5.6 Winding 2 and 3 elements
Because the winding 2 and 3 elements can be set with completely different parameters
than the winding 1 elements, it is necessary to repeat the full set of tests described above
for each winding.
7.5.6 Phase Instantaneous Overcurrent 2
The phase instantaneous overcurrent 2 elements are identical to the phase instantaneous
overcurrent 1 elements. As such, the same test procedure can be used to verify their
correct operation. Disable all protection features except the phase instantaneous
overcurrent 2 elements and follow the steps in the previous section, making the
appropriate changes for the display indications and output relays which are operated by
the phase instantaneous overcurrent 2 elements.
Note
The blocking from logic input, if enabled, can be tested as described in earlier tests for
other elements.
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