GE 745 TRANSFORMER MANAGEMENT RELAY User Manual

10-38 745 Transformer Management Relay GE Power Management
10.6 PROTECTION SCHEMES 10 COMMISSIONING
10
7. Check that the TRIP and PICKUP LEDs are on and the following trip message is displayed:
8. Slowly decrease the frequency until the PICKUP indicator and output relays reset. Note the dropout level,
which should be the pickup minus 0.03 Hz. Check that the TRIP indicator is still on. The trip message
remains on if the TARGET setting is
Latched
; if set to
Self-resetting
, the message resets when frequency is
below the setpoint.
9. 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 10–11: FREQUENCY ELEMENT TESTING on page 10–34.
10. Set the voltage to rated VT secondary value, the current to rated CT secondary, and the pre-trigger fre-
quency to the nominal frequency (60 or 50 Hz). The current signal is not required if current sensing has not
been enabled for this element.
11. Set the post-trigger to 0.5 Hz above the setting of the Overfrequency element. If necessary, reset all tar-
gets and relays. Reset the timer.
12. Initiate the frequency step and timer start. The Interval Timer records the operating time of element. Com-
pare this time to setting under:
SETPOINT/S4 ELEMENTS/FREQUENCY/OVERFREQUENCY DELAY
13. 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.
c) CURRENT INPUT FUNCTION (VOLTAGE INPUT DISABLED)
If the voltage input is disabled, the Frequency elements use the A-phase Winding #1 current signal as a
source. Verify the operation of the element using the procedure below.
1. Using the variable-frequency current source connected to terminals H1 and G1, 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 on the relay. The relay display
should remain unchanged with no trip indications.
2. Slowly increase the frequency until the output relay(s) operate. Check that the frequency at which opera-
tion 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 cur-
rent is the minimum operating current selected in the settings.
If current sensing has been disabled for this element, then operation continues down to 0.00 A.
4. Increase the current back to nominal. Check that the relay(s) operate.
5. Check that the TRIP and PICKUP LEDs are on and the following trip message is displayed:
6. Slowly decrease the frequency until the PICKUP indicator and output relays reset. Note the dropout level,
which should be the pickup minus 0.03 Hz. Check that the TRIP indicator is still on. The trip message stays
on if the TARGET setting is
Latched
; if it is
Self-resetting
, the message resets when frequency is below the
setpoint.
yy LATCHED (OPERATED):
yy Overfrequency
yy LATCHED (OPERATED):
yy Overfrequency

GE 745 TRANSFORMER MANAGEMENT RELAY Specifications

General

Brand	GE
Model	745 TRANSFORMER MANAGEMENT RELAY
Category	Relays
Language	English