GE G30 Instruction Manual page 479

CHAPTER 5: SETTINGS
Third harmonic neutral undervoltage protection that responds to the third harmonic in the voltage at the machine neutral
point is provided as a means of stator ground protection.
This element is configured through its individual setting menu. The
source used to provide current and voltage signals for stator ground fault protection. The third harmonic neutral
undervoltage function is configured as follows:
• Configure phase voltages measured at the terminal of the machine as phase VT banks. The element uses the voltages
to measure the power at the machine terminals for power supervision.
• Configure phase currents measured at the terminal of the machine as phase CT banks. The element uses the currents
to measures the power at the machine terminals for power supervision.
• Configure voltage measured at the neutral of the machine as the auxiliary VT bank. The element extracts the third
harmonic of the auxiliary voltage from the source in order to operate.
5.7.14.2 Third harmonic neutral undervoltage (ANSI 27TN)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  STATOR GROUND  3RD HARM NTRL
UNDERVOLTAGE
 3RD HARM NTRL
 UNDERVOLTAGE
The third harmonic neutral undervoltage function detects a loss of third harmonic voltage at the generator neutral. The
percentage of stator winding covered by this function depends on the pickup setting and the amount of third harmonic
generated by the machine at the time of the fault. A settable window of forward power can supervise this element for
enhanced security. The element is also supervised by positive-sequence voltage measured at the generator output
terminals. This element can be used with either wye or delta connected VTs on the terminal side and requires the machine
neutral voltage to be connected via an auxiliary voltage channel of a relay VT bank.
— This setting specifies the pickup level for the magnitude of the third harmonic of the neutral
3RD HARM NTRL UV PICKUP
voltage. This setting is entered in pu of the nominal auxiliary voltage. Use the
menu to monitor the magnitude of the third harmonic voltage at the neutral point. Measuring the actual value of
GROUND
the operating quantity for a specific machine under variety of load conditions can be helpful when selecting the pickup
threshold for this feature.
3RD HARM NTRL UV MAX POWER
the measured power is below this setting but above the
operate. This setting applies to three-phase power and is entered in pu. The base quantity is three-phase power on the
primary side, which is calculated as
connected VTs and as 3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of wye connected VTs.
G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
3RD HARM NTRL UV

FUNCTION: Disabled
3RD HARM NTRL UV

PICKUP: 0.3000 pu
3RD HARM NTRL UV PKP

DELAY: 0.00 s
3RD HARM NTRL UV MAX

POWER: 0.200 pu
3RD HARM NTRL UV MIN

POWER: 0.200 pu
3RD HARM NTRL UV

VOLT SUPV: 0.500 pu
3RD HARM NTRL UV BLK:

Off
3RD HARM NTRL UV

TARGET: Self-reset
3RD HARM NTRL UV

EVENTS: Disabled
— This setting specifies the maximum active power that inhibits this protection function. If
3RD HARM NTRL UV MIN POWER
3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of delta
setting specifies a signal
STATOR GROUND SOURCE
Range: Disabled, Enabled
Range: 0.0010 to 3.0000 pu in steps of 0.0001
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.000 to 1.250 pu in steps of 0.001
Range: 0.000 to 1.250 pu in steps of 0.001
Range: 0.000 to 1.250 pu in steps of 0.001
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
ACTUAL VALUES  METERING  STATOR
setting, the element does not
GROUPED ELEMENTS
5
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