ANSI Fault Analysis
A_FAULT provides fault
calculations in full compliance with the ANSI C37 standards.
It offers separate solutions for
low, medium and high voltage systems and for symmetrical, momentary and
interrupting calculations as defined in the standards.
For medium and high voltage
systems, the momentary and interrupting values may be calculated using
either the E/X or E/Z methods permitted by the standards. Both ac and
dc decrement curves required by the total current rated standard
(C37.5) and the symmetrical rated standard (C37.010) are used by the
- 1. Design safer power systems by calculating
equipment ratings per ANSI standards.
- 2. Save time by automatically applying ANSI C37
and IEEE 141 multiplying factors to generators and motors.
- 3. Increase efficiency with custom data
reporting featuring X/R, E/X or E/Z methods and values for the
application of low, medium, and high voltage
- 4. Communicate effectively with quality reports.
- Reports three-phase, single-line to ground,
line to line, and double line to
ground fault values.
- Reports values for both total current and
symmetrical rated breakers.
- Models transformer primary and secondary taps
and off nominal rated voltages.
- Use either ac/dc, dc only, interpolated or no
ac decay options.
- Reports calculated remote/local status for each
- Interrupting study reports total and
symmetrical 2, 3, 5, 8 and 30 cycle values.
- Complies with ANSI standards and IEEE
- Provides separate network solutions for
reporting X/R values.
- Momentary and interrupting studies can report
E/X or E/Z values.
- Low voltage study complies with ANSI C37.13.
- Momentary and interrupting studies comply with
ANSI C37.010 and C37.5.
- Custom reports using datablocks or crystal
- Display study results on the one-line.
- User defined pre-fault voltage.
A_FAULT Versus DAPPER Traditional
A_FAULT follows ANSI C37 standards
for calculating equipment ratings.
DAPPER follows a traditional Ohm’s
Law calculation for fault current.
For Low voltage systems (600V and
below), the calculations are the same except for two items: 1) A_FAULT
calculates the X/R ratios based on separate X and R networks whereas
DAPPER uses a single complex network.
2) A_FAULT uses the X/R/ ratio to adjust the calculated short circuit
value to compare directly with molded case and power circuit breaker
ratings based on ANSI test power factor. In other words, the calculated
short circuit value is increased if the X/R/ ratio is larger that the
ANSI test power factor.
For Medium and High Voltage systems
(above 600Volts): The momentary calculations are similar. The largest
difference is in Interrupting Calculations: A_FAULT uses the ANSI C37
tables and curves to simulate AC and DC decay for interrupting
calculations, whereas DAPPER accounts for the system DC decay but
ignores the AC machine decay in all cases.