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8 COMMISSIONING
6.
The reset level should be 97% of operate level. When the element resets, the Trip and Message LEDs should remain
on if the
W1 RESTD GND FAULT TARGET
WINDING 2 OR 3 ELEMENTS:
Since the second Restricted Ground Fault element can be set with completely different parameters than the first element
winding, it is necessary to repeat the full set of tests described in this section for each winding.
To test the second element, disable all protection elements except for the Winding 2 (or Winding 3 as appropriate)
Restricted Ground Fault element. Connect the ground current signal to Terminals F12 and E12. Repeat all the tests
described for the Winding 1 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 Negative Sequence Time Overcurrent performance matches the in-service settings. Since
these elements can have any one of a multitude of timing curves, a table of expected operating times versus applied cur-
rent should be prepared prior to testing the elements. The negative-sequence element measures the derived negative-
sequence component of the phase current signals connected to the phase input CTs. Refer to Time Overcurrent Curves on
page 5–49 for additional information on timing curves.
If the relay elements are set for "Linear" reset characteristic when measuring the operating times, ensure that there is suffi-
cient time between test current injections for the element to reset fully. Otherwise, erroneous timing measurements will be
obtained. Settings for these elements are found in the
WINDING 1 ELEMENT:
To ensure that only the Negative Sequence Time Overcurrent element operates the trip relays (and any other output relays
selected by the logic) disable all protection features except Negative Sequence Time Overcurrent. Use the general test
setup shown in Figure 8–9: General Test Setup on page 8–18.
Connect the current supply to terminals X = H1 and Y = G1 to test the Winding 1 negative-sequence element. Monitor the
appropriate output relays as per the relay FlexLogic™ settings.
PICKUP LEVEL:
1.
With the interval timer disabled, apply the current signal and slowly increase its magnitude until the trip relay and all
selected auxiliary relays operate. If the relay has a very inverse time characteristic, it is easier and more accurate to
increase the current far above the pickup level until the trip relay operates then reduce the current to just above the
operate level. Then, slowly reduce the current below the operate level and observe for a reset action on the trip relay.
This reset level for the current should be approximately 98% of the pickup level. Once the relay drops out, slowly
increase the current until the trip contact closes. The operate level should correspond to the
OC
W1 NEG SEQ TIME OC
With current applied to a single phase, the negative sequence current component is calculated from:
NOTE
Hence, the phase current will be three times the pickup setting.
2.Check that, when the element operates, the Trip and Pickup LEDs are on and one of the following messages
is displayed:
LATCHED
W1 Neg Seq Time OC
3.
Reduce the current until the element resets. The reset level should be 97% of the operate level. When the element
resets the Trip and Message LEDs should remain on if the
Otherwise only the Trip LED remains on.
Reset indicators and clear messages.
GE Multilin
Courtesy of NationalSwitchgear.com
was selected as "Latched". Otherwise only the Trip LED should remain on.
S4 ELEMENTS
setting.
W1 NEG SEQ TIME OC PICKUP
1
-- -
I
=
neg seq
3
OPERATED
W1 Neg Seq Time OC
745 Transformer Management Relay
8.5 PROTECTION SCHEMES
8.5.11 NEGATIVE SEQUENCE TIME OVERCURRENT
NEG SEQ OC
W1 NEG SEQ TIME OC
×
I
phase
W1 NEG SEQ TIME OC TARGET
settings menu:
S4 ELEMENTS
NEG SEQ
(EQ 8.14)
was selected as "Latched".
8-27
8
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