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Protection Schemes
NOTE
GE Multilin
5.
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
6.
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 remains on if the
setting is "Latched"; if set to "Self-Resetting", the message resets when
TARGET
frequency is above the setpoint.
7.
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.
8.
Set the current to rated CT secondary value, no voltage connection, and the
pre-trigger frequency to the nominal frequency (60 or 50 Hz).
9.
Set the post-trigger to 0.5 Hz below the Underfrequency 1 setting. If necessary,
reset all targets and relays. Reset the timer.
10. Initiate the frequency step and timer start. The Interval Timer will record the
operating time of element. Compare this time to the
!
UNDERFREQUENCY 1
!"
11. 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.
The blocking from logic input, if enabled, can be tested as described in
earlier tests for other elements.
c) Underfrequency 2
1.
Disable all protection functions except the Underfrequency 2 function.
2.
Verify that settings match in-service requirements. Enter/modify settings and
logic in the
S4 ELEMENTS
3.
Repeat the appropriate steps of Underfrequency 1 on page 7–31 for this
element. The results must be compared to the settings for the Underfrequency
2 element.
d) Overfrequency
Disable all protection functions except Overfrequency. Verify that settings match in-
service requirements. Overfrequency settings are modified in the
FREQUENCY
!"
OVERFREQUENCY
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 fre-
quency to 60.00 Hz (or 50.00 Hz) and the voltage amplitude to the rated VT
secondary voltage. Set the current amplitude to rated CT secondary. Monitor
the appropriate trip and auxiliary relays. Reset all alarms and indications on the
relay. The 745 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 operation took place is the selected frequency setting. As
the frequency is varied, verify that the
actual value indicates the correct value of system frequency.
FREQUENCY
3.
Slowly reduce the voltage. Note the voltage at which the output relay(s) reset.
Check that this dropout voltage is equal to the
OVERFREQUENCY
!"
MINIMUM OPERATING VOLTAGE
level can be set down to 0.00 A, in which case the element remains operated to
a voltage level of approximately 2% of nominal.
http://www.GEindustrial.com/multilin
Transformer Management Relay
setting.
UNDERFREQUENCY 1 DELAY
!"
FREQUENCY
!"
UNDERFREQUENCY 2
settings menu.
A2 METERING
S4 ELEMENTS
voltage level. Note that this
745
UNDERFREQUENCY 1
S4 ELEMENTS
!"
FREQUENCY
setpoints menu.
S4 ELEMENTS
!"
FREQUENCY
SYSTEM
!"
!
!"
FREQUENCY
!"
7–33
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