Introduction

The playback model is a block used to play wave forms in order to validate the control and protection equipment of power grids. It allows users to play back, on analog or digital channels, arbitrary wave forms originating from files in COMTRADE format.
The COMTRADE (Common Format for Transient Data Exchange) format is a IEEE standard used to facilitate the exchange of digital data from transient phenomena such as power grid faults, test cases or simulation cases. As this format is widespread, the wave forms can originate from different sources, such as:

• a recorder (protection relay, measuring device);
• a digital or analog network simulator;
• a signal processing software (e.g. SCOPEVIEW, SPECTRUM);
• any other device or software exporting digital signals in COMTRADE format.

Main Features

Here is an overview of the system features:

• consists of 32 D/A output channels;
• consists of 32 logical output channels;
• output range is 1 Hz to 20 kHz;
• allows users to play back arbitrary wave forms from COMTRADE files in binary or ASCII format in compliance with the IEEE C37.111-1991 or C37.111-1997 standard;
• allows users to change the gain of analog signals;
• allows users to select output signals;

Control Parameters

The parameters of the PLAYBACK model allow users to change the behavior of the software when wave forms are played. More specifically, these parameters are used to :

• enter the name of the directory and of the COMTRADE file. Activate Load File; the signal in the file will be loaded in the analog/digital output page.
• select the operating mode (transient or steady-state);
• add a number of steady-state cycles at the beginning and end of signals;
• if needed, enable the start/stop button for emergencies;
• select the type of synchronization required: internal with the current HYPERSIM® POW or external with an analog signal or a logic command signal (rising front);
• select a reference signal to measure the first steady-state cycle or to set the frequency of the signal.

Operating Modes

• The software can play back wave forms in two modes: transient or steady-state. In transient mode, the signals are played back entirely.
• In steady-state mode, the software automatically detects a permanent cycle at the beginning of each analog signal and plays back this cycle indefinitely. For digital output, the software takes the first point as reference and plays back this point indefinitely.
• When using the steady-state mode, make sure the signals have at least two steady-state cycles at is beginning.
• The Prefault and Postfault fields allow users to specify the number of steady-state cycles to add at the beginning (Prefault) (before the fault or the transient phenomenon) and the end of the wave forms (Postfault).

Reference Frequency for Steady-State Mode

A parameter allows users to select from a list of analog signals the reference signal used to measure the first steady-state cycle or to set the frequency.
There is no steady-state detection for digital output.

Signal Output Rate

The output rate of signals to play back is based on the execution step of the HYPERSIM® simulation (TimeStep parameters). Hence, if the TimeStep is different from the wave form rate, a resampling
of the original wave forms will take place. The software interpolates or decimalizes the original signal. In both cases, a message warns the user.
Users can launch ScopeView to execute a resampling of their COMTRADE file, according to their needs, in order to play back the file using the same rate as with HYPERSIM®.

Updating Parameter Changes

The Apply button allows users to apply the changes made.
The Cancel button allows users to cancel the changes made and to close the parameter editing window.
The Close button allows users to apply the changes made and to close the parameter editing window.

Playback Synchronization

A parameter in the control panel allows users to select the synchronization mode for the transient mode. The internal synchronization mode operates with the POW and the external synchronization mode with the T input signal.
In the internal playback mode and in the steady state, there is no playback synchronization in the steady-state mode.
But, if the internal mode is selected, the acquisition with ScopeView will launch an internal signal sent to the playback block and the transient mode is then executed using the prefault and the postfault values using also the prefault and the postfault cycle values.
For the external mode, if the input of the T signal changes from 0 to 1 (rising wavefront), the transient mode is then launched immediately.

HYPERSIM® Graphic Interface

Here is an example of a playback can be accessed in HYPERSIM®. In the File menu, click Options. In the Open an Example File section, expand the How To menu and double click COMTRADE_Playback.ecf.

Input/output
Input: T
Output: Aout, Dout

The selected signal connected to the input of the voltage source is sent to the mono phase and the sync out of the POW base on this signal will generate the trigger input for the synchronization of the transient playback.

Parameters

The COMTRADE Playback block provides panels to view of modify General, Analog and Digital parameters.

The Analog tab lets you specify a channel number, the gain to add and whether to enable or disable the channel. Channels can be in any order.

The Analog tab lets you specify a channel number, the gain to add and whether to enable or disable the channel. Channels can be in any order.