GE T60, Instruction Manual

Page: 171 / 796

GE Multilin T60 Transformer Protection System 5-25
5 SETTINGS 5.2 PRODUCT SETUP
5
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.
The
CURRENT CUT-OFF LEVEL
and the
VOLTAGE CUT-OFF LEVEL
are used to determine the metered power cut-off levels. The
power cut-off level is calculated as shown below. For Delta connections:
(EQ 5.3)
For Wye connections:
(EQ 5.4)
(EQ 5.5)
where VT primary = VT secondary
×
VT ratio and CT primary = CT secondary
×
CT ratio.
For example, given the following settings:
CURRENT CUT-OFF LEVEL
: “0.02 pu”
VOLTAGE CUT-OFF LEVEL
: “1.0 V”
PHASE CT PRIMARY
: “100 A”
PHASE VT SECONDARY
: “66.4 V”
PHASE VT RATIO
: “208.00 : 1"
PHASE VT CONNECTION
: “Delta”.
We have:
CT primary = “100 A”, and
VT primary =
PHASE VT SECONDARY
x
PHASE VT RATIO
= 66.4 V x 208 = 13811.2 V
The power cut-off is therefore:
power cut-off = (
CURRENT CUT-OFF LEVEL
×
VOLTAGE CUT-OFF LEVEL
×
CT primary
×
VT primary)/VT secondary
= ( × 0.02 pu × 1.0 V × 100 A × 13811.2 V) / 66.4 V
= 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 and CURRENT CUT-OFF LEVEL with care as the relay accepts lower sig-
nals as valid measurements. Unless dictated otherwise by a specific application, the default settings of “0.02 pu” for
CURRENT CUT-OFF LEVEL and “1.0 V” for VOLTAGE CUT-OFF LEVEL are recommended.
5.2.3 CLEAR RELAY RECORDS
PATH: SETTINGS

PRODUCT SETUP

CLEAR RELAY RECORDS

CLEAR RELAY

RECORDS
CLEAR USER REPORTS:
Off
Range: FlexLogic operand
MESSAGE
CLEAR EVENT RECORDS:
Off
Range: FlexLogic operand
MESSAGE
CLEAR OSCILLOGRAPHY?
No
Range: FlexLogic operand
MESSAGE
CLEAR DATA LOGGER:
Off
Range: FlexLogic operand
MESSAGE
CLEAR ARC AMPS 1:
Off
Range: FlexLogic operand
MESSAGE
CLEAR ARC AMPS 2:
Off
Range: FlexLogic operand
3-phase power cut-off
3
CURRENT CUT-OFF LEVEL
×
VOLTAGE CUT-OFF LEVEL
VT primary
×
CT primary
× ×
VT secondary
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
3-phase power cut-off
3
CURRENT CUT-OFF LEVEL
×
VOLTAGE CUT-OFF LEVEL
VT primary
×
CT primary
× ×
VT secondary
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
per-phase power cut-off
CURRENT CUT-OFF LEVEL VOLTAGE CUT-OFF LEVEL
VT primary × CT primary × ×
VT secondary
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
=
3
NOTE