GE Multilin 745

Protection Schemes745
Transformer Management Relay
Commissioning
http://www.GEindustrial.com/multilin
7–32
GE Multilin
If voltage supervision is set to 0.0, then the element remains operated until the
voltage is decreased below approximately 2%, the level at which measurements
become unreliable.
6. Slowly increase the voltage and check that the element operates when the
voltage reaches 2% above the supervision level. Return the voltage to nominal
value.
7. Slowly decrease the current until the element resets. Check that this dropout
current level is equal to the
S4 ELEMENTS !" FREQUENCY ! UNDERFREQUENCY 1 !"
MINIMUM OPERATING CURRENT setting:
If current sensing is disabled in the element, it will remain operated with current
reduced to 0.0 A.
8. Slowly increase the current and ensure the element operates when the current
reaches a value just above the setting. Set the current to rated CT secondary.
9. Check that the Trip and Pickup LEDs are on and one of the following trip
messages is displayed:
LATCHED: Underfrequency 1 or OPERATED: Underfrequency 1
10. Slowly increase the frequency until the Pickup LED and output relays reset.
Note the dropout level, which should be the pickup plus 0.03 Hz. Check that the
Trip LED is still on. The trip message will stay on if the
UNDERFREQUENCY 1
TARGET setting is “Latched”; if set to “Self-resetting”, the message will reset
when frequency is above the setpoint.
11. For timing tests, the signal generator must be capable of triggering into step-
wise changing of frequency or ramping down to a pre-selected frequency in only
a few milliseconds. Connect the Signal Source and Timer Start triggers as
shown in FIGURE 7–12: Frequency Element Testing on page 7–31.
12. Set the voltage to rated VT secondary value, the current to rated CT secondary,
and the pre-trigger frequency to the nominal frequency (60 or 50 Hz). If current
sensing is not enabled, it is not necessary to connect the current signal.
13. Set the post-trigger to 0.5 Hz below the setting for Underfrequency 1. Reset all
targets and relays, if necessary. Reset the timer.
14. Initiate the frequency step and timer start. The Interval Timer will record the
operating time of element. Compare this time to the
S4 ELEMENTS !" FREQUENCY
! UNDERFREQUENCY 1 !" UNDERFREQUENCY 1 DELAY setpoint value:
15. Provided that the operate times are not scattered over a wide range, it may be
desirable to repeat this test several times and average the results. If there is a
wide scatter, verify the test setup and ensure the signal source behaves in a
consistent manner.
Current Input Function (Voltage Input Disabled):
If the Frequency elements are using the Winding 1 Phase A current signal as a
source, verify the operation of the element using the instructions below.
1. Using the variable-frequency current source connected to terminals H1 and G1
with no voltage connections, set the frequency to 60.00 Hz (or 50.00 Hz) and
the amplitude to the rated CT secondary current. Monitor the appropriate trip
and auxiliary relays. Reset all alarms and indications. The display should remain
unchanged with no trip indications.
2. Slowly decrease the frequency until the output relay(s) operate. Check that the
frequency at which operation took place is the selected frequency setting.
3. Slowly reduce the current. Note the current at which the output relay(s) reset.
Check that this dropout current is the minimum operating current selected in
the settings.
If current sensing is not enabled, then the element will continue
working all the way down to a current level of 0.02 × CT A.
4. Increase the current back to nominal. Verify that the relay(s) operate.
NOTE
NOTE
NOTE