Protection Schemes745
Transformer Management Relay
Commissioning
http://www.GEindustrial.com/multilin
7–24
GE Multilin
c) Pickup Level
1. With the interval timer disabled, apply the current signal and slowly increase its
magnitude until the trip relay (and all the selected auxiliary relays) operate.
2. 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
and 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
S4 ELEMENTS !"
GROUND OC ! W1 GND TIME OC !" W1 GROUND TIME OC PICKUP setpoint.
3. When the element operates, check that the Trip, Ground, and Pickup LEDs are
on and one of the following messages is displayed:
LATCHED a: W1 Gnd Time OC or OPERATED a: W1 Gnd Time OC
4. 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
W1 GROUND TIME OC TARGET was selected as “Latched”.
Otherwise, only the Trip LED should remain on.
5. Reset indicators and clear messages.
d) Operating Time
Using a table like the one shown blow, select three (3) or four (4) values of current
multiples at which the timing is to be measured. Enter the expected operating times
from the timing curve applied in the settings. Using FIGURE 7–9: General Test Setup
on page 7–18 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.
e) 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 triggering. To perform such a
test, contact GE Multilin for detailed test instructions.
A simple verification of the reset mode selected with the
S4 ELEMENTS !" GROUND OC
! W1 GND TIME OC !" W1 GROUND TIME OC RESET setpoint is obtained using the setup
in FIGURE 7–9: General Test Setup on page 7–18. 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.
f) 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.
CURRENT
MULTIPLE
NOMINAL
TIME
MEASURED
TIME
1.5
3
5
To Next Page
Loading...
