GE G60 Instruction Manual page 108

5.2 PRODUCT SETUP
• VOLTAGE CUT-OFF LEVEL: This setting modifies the voltage cut-off threshold. Very low secondary voltage measure-
ments (at the fractional volt level) can be affected by noise. Some customers prefer these low voltages to be displayed
as zero, while others prefer the voltage to be displayed even when the value reflects noise rather than the actual sig-
nal. The G60 applies a cut-off value to the magnitudes and angles of the measured voltages. If the magnitude is below
the cut-off level, it is substituted with zero. This operation applies to phase and auxiliary voltages, and symmetrical
components. The cut-off operation applies to quantities used for metering, protection, and control, as well as those
used by communications protocols. Raw samples of the voltages available via oscillography are not subject cut-off.
5
The
CURRENT CUT-OFF LEVEL
power cut-off level is calculated as shown below. For Delta connections:
3-phase power cut-off
For Wye connections:
3-phase power cut-off
per-phase power cut-off
where VT primary = VT secondary × VT ratio and CT primary = CT secondary × CT ratio.
For example, given the following settings:
CURRENT CUT-OFF LEVEL
VOLTAGE CUT-OFF LEVEL
PHASE CT PRIMARY
PHASE VT SECONDARY
: "208.00 : 1"
PHASE VT RATIO
PHASE VT CONNECTION
We have:
CT primary = "100 A", and
VT primary =
PHASE VT SECONDARY
The power cut-off is therefore:
power cut-off = (
CURRENT CUT-OFF LEVEL
= (
= 720.5 watts
Any calculated power value below this cut-off will not be displayed. As well, the three-phase energy data will not accumu-
late if the total power from all three phases does not exceed the power cut-off.
Lower the
VOLTAGE CUT-OFF LEVEL
as valid measurements. Unless dictated otherwise by a specific application, the default settings of "0.02
NOTE
pu" for
CURRENT CUT-OFF LEVEL
5-10
and the
VOLTAGE CUT-OFF LEVEL
3 ×
CURRENT CUT-OFF LEVEL
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
=
×
3
CURRENT CUT-OFF LEVEL
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
=
CURRENT CUT-OFF LEVEL
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- -
=
: "0.02 pu"
: "1.0 V"
: "100 A"
: "66.4 V"
: "Delta".
x
PHASE VT RATIO
×
VOLTAGE CUT-OFF LEVEL
3 × 0.02 pu × 1.0 V × 100 A × 13811.2 V) / 66.4 V
and
CURRENT CUT-OFF LEVEL
and "1.0 V" for
G60 Generator Management Relay
are used to determine the metered power cut-off levels. The
× ×
VOLTAGE CUT-OFF LEVEL
VT secondary
× ×
VOLTAGE CUT-OFF LEVEL
VT secondary
× ×
VT primary
VOLTAGE CUT-OFF LEVEL
VT secondary
= 66.4 V x 208 = 13811.2 V
× CT primary × VT primary)/VT secondary
with care as the relay accepts lower signals
are recommended.
VOLTAGE CUT-OFF LEVEL
5 SETTINGS
VT primary × CT primary
(EQ 5.3)
×
VT primary CT primary
(EQ 5.4)
×
CT primary
(EQ 5.5)
GE Multilin