comtrade

Python Comtrade

Python Comtrade is a module for Python 3 designed to read Common Format for Transient Data Exchange (COMTRADE) files. These consists of oscillography data recorded during power system outages, control systems tests, validation and tests of field equipment, protective relaying logs, etc. The COMTRADE format is defined by IEEE Standards, summarized in the table below. Some equipment vendors put additional information in proprietary versions of it. This module aims IEEE definitions but may support those proprietary versions.

Standard	Revision
IEEE C37.111(TM)-1991	1991
IEEE C37.111(TM)-1999	1999
IEC 60255-24:2001	2001
IEEE C37.111(TM)-2013 / IEC 60255-24:2013	2013

Installation

pip install comtrade

Or just copy comtrade.py from this repository.

Requirements

• Python 3.6 or newer
• (optional) numpy for speed improvement
• (optional) pandas for data frame support

How to Use

The examples below shows how to open both CFG and DAT files or the new CFF file to plot (using pyplot) analog channel oscillography.

CFG and DAT files (all revisions)

Comtrade files separated in CFG and DAT formats can also be read with load function. A CFG file path must be passed as an argument and, optionally, a DAT file path too (if the file name is not equal of the CFG file).

import matplotlib.pyplot as plt
import comtrade

rec = comtrade.load("sample_files/sample_ascii.cfg", "sample_files/sample_ascii.dat")
print("Trigger time = {}s".format(rec.trigger_time))

plt.figure()
plt.plot(rec.time, rec.analog[0])
plt.plot(rec.time, rec.analog[1])
plt.legend([rec.analog_channel_ids[0], rec.analog_channel_ids[1]])
plt.show()

It will read the contents of additional header (*.hdr) and information (*.inf) files. Their contents are available through Comtrade.hdr and Comtrade.inf properties.

CFF files (2013 revision)

import matplotlib.pyplot as plt
import comtrade

rec = comtrade.load("sample_files/sample_ascii.cff")
print("Trigger time = {}s".format(rec.trigger_time))

plt.figure()
plt.plot(rec.time, rec.analog[0])
plt.plot(rec.time, rec.analog[1])
plt.legend([rec.analog_channel_ids[0], rec.analog_channel_ids[1]])
plt.show()

The module function load must be called with the CFF file path specified.

Comtrade.analog and Comtrade.status lists stores analog and status channel sample lists respectively. These can be accessed through zero-based indexes, i.e., Comtrade.analog[0]. The list Comtrade.time stores each sample time in seconds.

More information can be accessed through Comtrade.cfg object, which stores data such as detailed channel information.

Data of additional sections, such as HDR and INF, can be accessed through hdr and inf properties, respectively.

Data frames

The module supports the use of pandas.DataFrame as a data structure. Use the conveninent function load_as_dataframe or call Comtrade.to_dataframe() function after loading the data.

import comtrade
df = comtrade.load_as_dataframe("sample_files/sample_ascii.cfg")
print(df.head())

# Or, alternatively
rec = comtrade.load("sample_files/sample_ascii.cfg")
df = rec.to_dataframe()
print(df.head())

Features

This module implements some of the functionality described in each of the Standard revisions. The tables below lists some features and file formats and which revision supports it. It also shows whether this module support the feature or the format.

Feel free to pull requests implementing one of these unsupported features or fixing bugs.

Formats	1991	1999	2001	2013	Module Support
CFG file format	x	x	x	x	x
DAT file format	x	x	x	x	x
HDR file format	x	x	x	x	no
INF file format		x	x	x	no
CFF file format				x	x
ASCII data file format	x	x	x	x	x
Binary data file format	x	x	x	x	x
Binary32 data file format				x	x
Float32 data file format				x	x
Schema for phasor data				x	no

Features	1991	1999	2001	2013	Module Support
COMTRADE standard revision		x	x	x	x
Timestamp multiplication factor		x	x	x	x
Time code and local code				x	x
Time quality of the samples				x	x
Analog channel time skew		x	x	x	Partial
Analog channel primary and secondary VT or CT ratio		x	x	x	x
Status channel phase and monitored circuit		x	x	x	x
Multiple sample rates	x	x	x	x	Partial
Nanoseconds scale			x	x	x

Unsupported features

• Nanoseconds time base within Python's datetime objects (such as start_timestamp and trigger_timestamp properties). It warns the user but doesn't use it, truncating the numbers.
• Use of multiple sample rates in time calculations for binary data.

Additional settings and features

Numpy arrays as data structures

The use of numpy.array as a data structure to hold time, analog and status data can be enforced in Comtrade object constructor:

obj = Comtrade(use_numpy_arrays=True)

It may improve performance for computations after loading data.

Replace missing data with float('nan')

Missing analog values are replaced with float('nan'). The value used to represent missing data varies with the Comtrade dat format and revision year. These are listed in the table next.

revision	format	Missing Data Value
1991	ascii	"" (empty string)
1999, 2013	ascii	99999
1991	binary	0xFFFF
1999, 2013	binary	0x8000 or -32768
2013	binary32	0x80000000 or -2147483648
2013	float32	minimum negative float value

File encodings

Specify the encoding as a keyword argument on all load methods as you'd specify for common file loading:

import comtrade
comtrade.load("sample_files/sample_ascii.cff", encoding="iso-8859-1")

Documentation

https://github.com/dparrini/python-comtrade

Support

Feel free to report any bugs you find. You are welcome to fork and submit pull requests.

Development

To run tests, use Python's unittest. From a clone of the GitHub repository, run the command:

python3 -m unittest ./tests/tests.py

License

The module is available at GitHub under the MIT license.