case module

Module: case.py

Description

Operating-case data model for PyPacity ampacity calculations.

Copyright

License

SPDX-License-Identifier: GPL-3.0-only

Notes

This module is part of the PyPacity project.

References

IEEE Std 738-2012, IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors
CIGRE Technical Brochure 601, Guide for Thermal Rating Calculations of Overhead Lines
CIGRE Technical Brochure 207, Thermal Rating of Overhead Lines

class pypacity.case.case.Case

Bases: object

Environmental and operational inputs for an ampacity study.

Collects all inputs required by the IEEE 738 and CIGRE TB 601/207 solvers and exposes the results once the solver completes. Inputs are set directly on the instance; results are read from the same object after the solver method returns.

Simulation inputs

Attribute	Type	Standard	Description
`NSELECT`	int	Both	Analysis mode: `1` steady-state conductor temperature, `2` steady-state ampacity, `3` transient conductor temperature, `4` transient thermal rating.
`TT`	int	Both	Total simulation time. Units are controlled by `SORM`.
`SORM`	int	Both	Time unit selector: `0` for seconds, `1` for minutes.
`DELTIME`	int	Both	Simulation time step in seconds.
`IORTPRELOAD`	int	IEEE 738	Initial condition mode for transient analyses (`NSELECT = 3` or `4`): `1` computes `TCDRPRELOAD` from `XIPRELOAD` via iteration, `2` uses `TCDRPRELOAD` directly (only valid for `NSELECT = 4`).
`TCDRPRELOAD`	float	Both	Initial or target steady-state conductor temperature in deg C.
`XIPRELOAD`	float	Both	Initial (preload) current in amperes.
`XISTEP`	float	Both	Final step current in amperes.
`TTfromST`	int	CIGRE	Transient start mode: `1` starts from the steady-state temperature, `0` starts from `TCDRinitial`. Defaults to `1`.
`TCDRinitial`	float	CIGRE	Initial conductor temperature in deg C when `TTfromST = 0`.

Environmental conditions

Attribute	Type	Standard	Description
`TAMB`	float	Both	Ambient air temperature in deg C.
`VWIND`	float	Both	Wind speed in m/s.
`DWIND_DEG`	float	Both	Wind direction in degrees (compass bearing).
`WINDANG_DEG`	float	Both	Effective angle between wind direction and conductor axis in degrees. IEEE 738 and CIGRE TB 601 compute it automatically from `DWIND_DEG` and `Z1_DEG`; CIGRE TB 207 reads it directly, so it must already be set when 207 runs standalone.
`CDR_ELEV`	float	Both	Conductor elevation above sea level in meters.
`Z1_DEG`	float	Both	Conductor direction clockwise from north in degrees.
`CDR_LAT_DEG`	float	Both	Conductor latitude in degrees.
`beta`	float	CIGRE	Conductor inclination to the horizontal in degrees. Defaults to `0`.

Solar settings

Attribute	Type	Standard	Description
`SUN_TIME`	float	Both	Solar hour in the range 0-24. Set to `99` (or any value `≥ 24`) to use `SolarRadiation` directly as the solar irradiance instead of computing it from position, date, and time.
`NDAY`	int	Both	Day of year in the range 1 to 365.
`A3`	int	Both	Atmospheric clarity selector: `0` for clear air, `1` for industrial atmosphere.
`Ns`	float	CIGRE	Clearness ratio as defined in CIGRE TB 601. Defaults to `1.0` (clear sky).
`SolarRadiation`	float	Both	Measured solar radiation intensity in W/m2.
`ALBEDO`	float	CIGRE	Ground reflectance coefficient. Defaults to `0.0`.
`SOLAR`	int	CIGRE	Solar source selector: `0` uses `SolarRadiation`, `1` computes solar heat gain from date, time, and location.

Results

Attribute	Type	Standard	Description
`TR`	float	Both	Steady-state thermal rating in amperes. Populated after `NSELECT = 2`.
`TCDRPRELOAD`	float	Both	Also used as a result: steady-state conductor temperature in deg C populated after `NSELECT = 1`.
`XISTEP`	float	Both	Transient thermal rating current in amperes. Populated after `NSELECT = 4`.
`ATCDR`	list	Both	Transient conductor temperature trace in deg C. Populated after `NSELECT = 3` or `4`.
`TIME`	list	Both	Transient time trace in seconds. Populated after `NSELECT = 3` or `4`.
`QS`	float	Both	Solar heat gain rate in W/m.
`QR`	float	Both	Radiative heat loss rate in W/m.
`QC`	float	Both	Convective heat loss rate in W/m.
`QJ`	float	CIGRE	Joule heating rate (I2 x Rac) in W/m.
`RAC`	float	CIGRE	Conductor AC resistance at the operating temperature in ohm/m.
`KTIMEMAX`	int	IEEE 738	Total number of time steps computed. Populated after `NSELECT = 3` or `4`.

Note

The following attributes are internal solver variables used as intermediate working storage during iteration and should not be modified directly: XLO, XHI, W4, R5, Q1, Q2, T3, T4, T5, U1, P1, K1, YC, WINDANG_RAD, NFLAG, AT, TCDR, XIDUMMY, Bstring, and others initialised in __init__.

demo(NSELECT)

Populate the case with sensible default values for a quick-start study.

Provides a baseline configuration drawn from the IEEE 738 standard sample calculations. The defaults can be used as-is with the IEEE 738 solver or overridden by the caller before passing the case to a CIGRE solver. CIGRE-specific attributes (Ns, ALBEDO, SOLAR, beta, TTfromST, TCDRinitial) are not set here and retain their __init__ defaults; override them after calling this method if a CIGRE study requires non-default values. Solar heat input is taken from the measured SolarRadiation value (SUN_TIME = 99) instead of being computed from the Sun’s position. The following base values are set for all modes:

Attribute	Value	Description
`TAMB`	40 °C	Ambient temperature.
`VWIND`	0.61 m/s	Wind speed.
`DWIND_DEG`	90°	Wind direction.
`WINDANG_DEG`	90°	Wind perpendicular to conductor axis.
`CDR_LAT_DEG`	43°	Conductor latitude.
`CDR_ELEV`	0 m	Sea level.
`Z1_DEG`	0°	Conductor direction.
`NDAY`	161	Day of year (June 10).
`SUN_TIME`	99	Use measured `SolarRadiation` as the irradiance instead of computing it.
`A3`	0	Clear atmosphere.
`SolarRadiation`	708.6 W/m2	Used as solar irradiance Q3 when `SUN_TIME = 99`.
`IORTPRELOAD`	1	Preload temperature computed from `XIPRELOAD`.
`TCDRPRELOAD`	101.1 °C	Initial conductor temperature.
`XIPRELOAD`	1000 A	Preload current.
`XISTEP`	1000 A	Step current.
`SORM`	0	Time expressed in seconds.
`TT`	6000 s	Total simulation time (100 min).
`DELTIME`	10 s	Simulation time step.

Parameters:

NSELECT (int) –

Analysis mode. NSELECT = 1 and NSELECT = 2 use only the base values above. NSELECT = 3 and NSELECT = 4 apply the following overrides on top:

3 (transient conductor temperature): XIPRELOAD = 400 A, XISTEP = 1200 A, SORM = 1, TT = 7200, DELTIME = 30 s, HNH = 2.
4 (transient thermal rating): IORTPRELOAD = 2, TCDRPRELOAD = 40 °C, TCDRMAX = 150 °C, SORM = 1, TT = 1800, DELTIME = 60 s, HNH = 2.

Note

The base values listed above are overwritten on this instance. CIGRE-specific attributes and solver state variables retain their __init__ defaults.

print_ver(): Print the module name and release date to standard output.