GE G60 Instruction Manual page 520

GROUPED ELEMENTS
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.
3RD HARM NTRL UV PICKUP
voltage. This setting is entered in pu of the nominal auxiliary voltage. Use the
5
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.
For example, a setting of 20% for a 200 MW machine, is 0.20 × 200 MW = 40 MW. If 7.967 kV is a primary VT voltage and 10
kA is a primary CT current, the source pu quantity is 239 MVA, and thus, the pu power setting is 40 MW / 239 MVA = 0.167
pu.
3RD HARM NTRL UV MIN POWER
the measured power is above this setting but below the
operate. If the
3RD HARMONIC NTRL UV MIN POWER
less than the
3RD HARM NTRL UV MAX POWER
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
as 3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of wye connected VTs.
5-306
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 pickup level for the magnitude of the third harmonic of the neutral
— This setting specifies the maximum active power that inhibits this protection function. If
x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of delta
— This setting specifies the minimum active power that inhibits this protection function. If
is set to "0.00 pu", then the element does not operate for all power values
setting.
x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of delta connected VTs and
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
3RD HARM NTRL UV MIN POWER
3RD HARM NTRL UV MAX POWER
G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
setting, the element does not
setting, the element does not