GE TRANSFORMER MANAGEMENT RELAY 745 Instruction Manual page 268

8.5 PROTECTION SCHEMES
VOLTAGE INPUT FUNCTION (VOLTAGE INPUT ENABLED):
1. Using the variable-frequency voltage/current source connected to terminals C11 and C12 for the voltage signal and H1
and G1 for the current signal, set the frequency to 60.00 Hz (or 50.00 Hz for 50 Hz systems) and the voltage amplitude
to the rated VT secondary voltage.
2. Set the current amplitude to rated CT secondary. Monitor the appropriate trip and auxiliary relays. Reset all alarms and
indications on the relay. The relay display should remain with no trip indications.
3. Slowly decrease the frequency until the output relay(s) operate. Check that the operation took place at the selected
frequency setting.
4. As the frequency is varies, verify that the correct system frequency is displayed by the
SYSTEM FREQUENCY
5. Slowly reduce the voltage and note the voltage at which the output relay(s) reset. Check that this dropout voltage is
approximately the voltage supervision value in the
OPERATING VOLTAGE
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.
NOTE
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
FREQUENCY
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
NOTE
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
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
setting is "Latched"; if set to "Self-resetting", the message will reset when frequency is above the setpoint.
TARGET
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 8–12: Frequency Element Testing on page 8–29.
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.
8
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
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.
8-30
Courtesy of NationalSwitchgear.com
actual value.
setpoint.
UNDERFREQUENCY 1 MINIMUM OPERATING CURRENT
FREQUENCY UNDERFREQUENCY 1
745 Transformer Management Relay
S4 ELEMENTS FREQUENCY
setting:
OPERATED
Underfrequency 1
UNDERFREQUENCY 1 DELAY
8 COMMISSIONING
A2 METERING FREQUENCY
UNDERFREQUENCY 1 MINIMUM
S4 ELEMENTS
UNDERFREQUENCY 1
setpoint value:
GE Multilin