scope:

Develop a recommended practice for a file format suitable for exchanging power quality-related measurement and simulation data in a vendor-independent manner. Appropriate definitions and event categories to be developed by other task forces under the IEEE Standards Coordinating Committee 22 (SCC-22) on Power Quality and the IEEE 1159 Working Group on Power Quality Monitoring.

Purpose

A variety of simulation, measurement, and analysis tools for power quality engineers are now available from many vendors. Generally, the data created, measured, and analyzed by these tools are incompatible between vendors. The proposed file format will provide a common ground that all vendors could export to and import from to allow the end user maximum flexibility in choice of tool and vendor.

There are two "layers" to this Power Quality Data Interchange Format (PQDIF): the physical layer and the logical layer. The physical layer describes the physical structure of the file without regard to what will actually be stored in it. It uses tags to identify particular elements of the file. This is similar in concept to tagged image file format (TIFF), used for storing images.

The logical layer uses the structure defined by the physical layer; it specifies specific tags to use when building up elements in the file.

The physical layer is based on

- Specific "physical" data types (e.g., INT1, INT2, INT4, REAL4, REAL8, etc.) for portability and a specific list of IDs for physical representation (e.g., ID_SERIES_PHYS_TYPE_INTEGER1, etc.)

- 4 byte alignment for efficient processing

- Little endian byte ordering (least significant byte stored first, ordering used in PCs)

- Tags, using globally unique identifiers (GUIDs), for unique identification of elements (hereafter called "tags")

The logical layer is based on

- Specific lists of tags to identify elements of a file

- A hierarchy of tags and expected physical types

- Extensibility using user-defined tags for private data

- Extensibility of the standard format using tags defined in the future

To keep things simple, many elements in the logical layer are based on an explicit list of enumerated IDs, such as

- Phase (ID_PHASE_AN, ID_PHASE_BN, etc.)

- IEEE 1159 disturbance category (ID_1159_TRANSIENT, ID_1159_SHORTDUR, etc.)

- High-level quantity type (ID_QT_WAVEFORM, ID_QT_RMS, etc.)

- Series quantity units (ID_QU_TIMESTAMP, ID_QU_VOLTS, ID_QU_AMPS, etc.)

- Series value type (ID_SERIES_VALUE_TYPE_MIN, ID_SERIES_VALUE_TYPE_MAX, etc.)

Once you understand the physical and logical formats of PQDIF, you will still need some guidelines on how to use it to represent real-world data. Please refer to Annex A and Annex B for details on how to represent various types of data. Also, third parties have created PQDIF tools and development kits to facilitate getting up to speed on PQDIF. The IEEE 1159 working group web site (http://grouper.ieee.org/groups/1159/3/doc.html) has public domain example data files, programs, and source code. Annex C documents a commonly implemented disk directory structure for containing multiple PQDIF files.