GE G30 Instruction Manual page 353

5 SETTINGS
• 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
menu. Measuring the actual value of the operating quantity for a specific machine under variety of
STATOR GROUND
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
shall not operate. This setting applies to three-phase power and is entered in pu. The base quantity is 3-phase power
on primary side, which is calculated as
delta connected VTs; and 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: This setting specifies the minimum active power that inhibits this protection func-
tion. If the measured power is above this setting but below the
not operate. If the
3RD HARMONIC NTRL UV MIN POWER
power values less than the
This setting applies to three-phase power and is entered in pu. The base quantity is 3-phase power on primary side,
which is calculated as
VTs; and 3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of wye connected VTs.
If the VTs are located on the high-voltage (HV) side of the transformer, then the source should be configured using
CTs that are also on the HV side. Correspondingly, if the VTs are located on the low-voltage (LV) side of the trans-
former, then the source should be configured using CTs that are also on the LV side. In both cases, the CT polarity
NOTE
should produce a positive power measurement when the machine is generating.
Figure 5–97: THIRD HARMONIC NEUTRAL UNDERVOLTAGE SCHEME LOGIC
GE Multilin
3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of
3RD HARM NTRL UV MAX POWER
3 x Phase CT Primary x Phase VT Ratio x Phase VT Secondary in case of delta connected
G30 Generator Protection System
ACTUAL VALUES
3RD HARM NTRL UV MIN POWER
3RD HARM NTRL UV MAX POWER
is set to "0.00 pu", then the element does not operate for all
setting.
5.6 GROUPED ELEMENTS
 
METERING
setting the element
setting the element shall
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