GE Multilin g60

GE Multilin G60 Generator Protection System 5-207
5 SETTINGS 5.6 GROUPED ELEMENTS
5
c) THIRD HARMONIC NEUTRAL UNDERVOLTAGE
PATH: SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  STATOR GROUND  3RD HARM NTRL UNDERVOLTAGE
The third harmonic neutral undervoltage function detects a loss of third harmonic voltage at the generator neutral. The per-
centage of stator winding covered by this function depends on the pickup setting and the amount of third harmonic gener-
ated 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: This setting specifies the pickup level for the magnitude of the third harmonic of the
neutral voltage. This setting is entered in pu of the nominal auxiliary voltage.
The magnitude of the third harmonic voltage at the neutral point is monitored in the
ACTUAL VALUES  METERING 
STATOR GROUND menu. Measuring the actual value of the operating quantity for a specific machine under variety of
load conditions may be helpful when selecting the pickup threshold for this feature.
• 3RD HARM NTRL UV MAX POWER: This setting specifies the maximum active power that inhibits this protection
function. If the measured power is below this setting but above the
3RD HARM NTRL UV MIN POWER setting the element
shall not operate. This setting applies to three-phase power and is entered in pu. The base quantity is 3  VT pu
base  CT pu base.
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: This setting specifies the minimum active power that inhibits this protection func-
tion. If the measured power is above this setting but below the
3RD HARM NTRL UV MAX POWER setting the element shall
not operate. If the
3RD HARMONIC NTRL UV MIN POWER is set to “0.00 pu”, then the element will not operate for all power
values less than the 3RD HARM NTRL UV MAX POWER setting.
This setting applies to three-phase power and is entered in pu. The base quantity is 3  VT pu base  CT pu base.
 3RD HARM NTRL
 UNDERVOLTAGE
3RD HARM NTRL UV
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
3RD HARM NTRL UV
PICKUP: 0.3000 pu
Range: 0.0000 to 3.0000 pu in steps of 0.0001
MESSAGE
3RD HARM NTRL UV PKP
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
3RD HARM NTRL UV MAX
POWER: 0.200 pu
Range: 0.000 to 30.000 pu in steps of 0.001
MESSAGE
3RD HARM NTRL UV MIN
POWER: 0.200 pu
Range: 0.000 to 30.000 pu in steps of 0.001
MESSAGE
3RD HARM NTRL UV
VOLT SUPV: 0.500 pu
Range: 0.000 to 1.250 pu in steps of 0.001
MESSAGE
3RD HARM NTRL UV BLK:
Off
Range: FlexLogic™ operand
MESSAGE
3RD HARM NTRL UV
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
3RD HARM NTRL UV
EVENTS: Disabled
Range: Disabled, Enabled