Scada Dta - GE ALPS Instruction Manual

2 CALCULATION OF SETTINGS
1406: LINEUNIT - Unit Of Length
The ALPS will report the distance to the fault relative to the relay location. Set LINEUNIT equal to MILES if location in miles
is required, otherwise set LINEUNIT equal to KILOMETERS or PERCENT.
1407: CTRATIO - Current Transformer Ratio
The ALPS will report present values in terms of secondary values or primary values as set by General Setting 108: DIS-
PLAYVAL. The ratio of the of the current transformers used to supply the system is used in this procedure. Set CTRATIO
equal to the CT ratio used with the ALPS system.
1408: PTRATIO - Potential Transformer Ratio
The ALPS will report present values in terms of secondary values or primary values as set by General Setting 108: DIS-
PLAYVAL. The ratio of the of the potential transformers used to supply the system is used in this procedure. Set PTRATIO
equal to the PT ratio used with the ALPS system.
An internal DTA (digital to analog) function, standard on the ALPS system, provides the following:
1. An analog output proportional to the distance from the relay to the fault as calculated by the fault-location algorithm.
2. Four contact outputs that provide fault-type information. (Configurable)
The analog output is intended to be wired into an analog port of a SCADA RTU to provide remote indication of distance to
the fault. The four contact output assignments are designated phase A (Index 60), phase B (Index 61), phase C (Index 62),
and neutral (Index 63) and are intended to be wired into four separate RTU ports. A particular contact closes when its
phase (or neutral) is involved in the fault. For a phase B-to-C-to-ground fault, the phase B, phase C, and neutral contacts
close. The contact assignments can be made from the keypad, or by using Xpression Builder.
The DTA provides either a nominal 0 to 1 mA DC output or a nominal 0 to 5 V DC output. The choice of output ranges is
made by a switch located on the Processor Board.
When the fault location is calculated to be 100% of the line length, the DTA output is either 0.8 mA DC or 4.0 V DC. The
DTA output goes to full scale (either 1 mA DC or 5 V DC) when the fault location is calculated to be greater than 110% of
the line length. Consequently, the usable output ranges are 0 to 0.88 mA DC or 0 to 4.4 V DC, which covers the 0 to 110%
fault-location range. The SCADA system should be programmed to recognize a full-scale output as an indication of an
invalid output, resulting from either an out-of-limit fault-location calculation or a DTA reset.
There are two settings associated with the SCADA DTA Interface. FLTLOCK specifies a time period after a fault during
which fault-location calculations resulting from subsequent faults are prevented from updating information stored in the
DTA logic. FLTRESET specifies the time after a fault at which the fault-location information stored in the DTA logic is reset
(output forced to full-scale value) and all fault-type contacts will open.
1501: FLTLOCK - Hold Time
Set FLTLOCK to the time following a fault during which fault location calculations resulting from subsequent faults will not
be updated.
1502: FLTRESET - Fault Location Reset Time
Set FLTRESET to the time following a when the fault location information stored in the DTA module is reset (output forced
to full-scale value) and those fault type contacts that have closed will open. A setting of 0 refers to an infinite time. For
example:
FLTLOCK = 10 seconds
FLTRESET = 5 minutes
With these settings, once the first fault occurs, the DTA module output will not change for subsequent faults that occur
within 10 seconds of the first fault, and the DTA module output will be reset 5 minutes after the last fault that caused the
DTA to produce an output.
GE Power Management ALPS Advanced Line Protection System
2.3 PROTECTION SETTINGS

2.3.17 SCADA DTA

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