Flash v1.81
===========

Changes from version 1.8:

1 - Excel front end works on Windows 95/98.

2 - Fixed output of negative actual shield angles.

3 - Fixed calculation of Sargent cone surge impedance.

4 - Warning message if shielding cannot be solved.

Flash v1.8
==========

This is a conversion of Flash 1.7 from MS Basic to C. The
program is no longer menu-driven, but reads input from a
text file. For a better user interface, try the Excel
spreadsheet front end.

Changes from version 1.7 affecting the results
==============================================

1 - An array bounds error was fixed around line 3330 of the
    Basic code, affecting the power frequency voltage phase
    angles.  The percentage of flashovers occuring on the
    outside phases of a flat horizontal line will now be
    equal.  The backflash rates of double-circuit lines will
    also generally decrease, often significantly.

2 - The new formulation of beta has been used for the strike
    distance to ground in the electrogeometric model.  The 
    perfect shielding angle will usually increase by a few 
    degrees, and the shielding failure flashover rate will 
    decrease slightly in cases where it was not zero.

3 - The bundled conductor spacing for English units input
    was improperly converted from inches to meters around
    line 1090 of the Basic code.  It is now properly converted
    from inches to mm.

New Input Options
=================

1 - Ground flash density can be input directly (thunderdays is
    available by entering it as a negative value).  The thunderhour
    input option is no longer available.

2 - A variable number of footing resistances may be entered,
    from 1 to 50 values.  Each ohmic resistance is associated
    with a histogram incidence rate that can be percentage,
    fraction, number of towers, or line segment length.

3 - Blank lines may be included, and comment lines beginning
    with ! or / are also allowed.

Running the Command line Version
================================

The input file is laid out the same as in v1.7, so that any
saved file from previous versions should also run in this
version. Blank or empty lines are allowed, and comment lines 
beginning with ! or / are also allowed. The file "template_old.dat" 
is an annotated version of the "tupox.dat" test case.

The new input options for ground flash density and footing
resistance histogram inputs are illustrated in the file
"template_new.dat".  The program recognizes the GFD input option
from a negative input for thunderdays.  The program recognizes
the new footing resistance histogram from two input values per
line, rather than one.

The program must be run from a Windows 95/98/NT/2000/ME
command prompt. The input file name must be supplied as
a command line argument. One command line switch is supported:

  -b  brief output of line flashover rates and shielding angles

Examples of running the program:

  "flash template_new.dat | more"

  (Runs the case in template_new.dat with a pause after each
  screen of output)

  "flash tupox.dat > tupox.out"

  (Runs the case in tupox.dat and writes the output to the
  file tupox.out. Existing information in tupox.out will
  be lost.)

  "flash -b plano.dat >> summary.out"

  (Runs the case in plano.dat with reduced output, appended to
  the fule summary.out.)

Several test cases are provided with summary solutions in the
file runtests_benchmark.out. The batch file "runtests.bat" runs
all of the test cases with reduced output to the file "runtests.out".

Running the Excel Front End - Flash.xls
=======================================

Microsoft Excel 97 or later is required.  Some of the code is in
Visual Basic for Applications (VBA) and can be viewed or edited
using the Tools/Macro/Visual Basic Editor menu command in Excel.
Macros must be enabled when opening the workbook.

Before clicking the "Run" button, update the paths to the program,
scratch input file, and scratch output file in cells J1 through J3.

Upon clicking "Run", the VBA code writes an input file from the
worksheet values and saves it in the file specified in cell J2.
Then it executes the program from cell J1 with the -b flag, writing
output to the file in cell J3.  Outputs are then placed in the 
worksheet's yellow cells.

If an error message appears in the output file, the worksheet will
display a message box.  This error message may seem cryptic, but
from the surrounding input values it should be possible to identify
the worksheet cell with offending data.