Schneider Electric 4000 manual Types of Waveform Captures, Steady-state Waveform Capture

Chapter 8—Waveform and Event Capture	63230-300-212
Types of Waveform Captures	April 2001

TYPES OF WAVEFORM CAPTURES

Steady-state Waveform Capture

Initiating a Steady-state

Waveform

Disturbance Waveform Capture

Using waveform captures you can monitor power sags and swells that may be produced, for example, when an X-ray machine and an elevator are used at the same time, or more commonly, when lightning strikes the distribution system that feeds the facility. The system’s alarms can be programmed to detect and record such fluctuations, enabling you to determine an appropriate strategy for corrective action.

Circuit monitors use a sophisticated, high-speed sampling technique to simultaneously sample up to 512 samples per cycle on all current and voltage channels. From this sampling, the circuit monitor saves waveform data into its memory. These waveform captures can be graphically displayed using SMS. The circuit monitor has one type of waveform capture that you initiate manually; the other three event captures are associated with and triggered by an event such as a digital input transition or over/under condition. These event recordings help you understand what happened during an electrical event. Using event captures you can analyze power disturbances in detail, identify potential problems, and take corrective action. See Chapter 9—Disturbance Monitoring on page 113 for more about disturbance monitoring. The types of event captures are described in the sections that follow.

The steady-state waveform capture can be initiated manually to analyze steady-state harmonics. This waveform provides information about individual harmonics, which SMS calculates through the 255th harmonic. It also calculates total harmonic distortion (THD) and other power quality parameters. The waveform capture records one cycle at 512 samples per cycle simultaneously on all metered channels.

Using SMS from a remote PC, initiate a steady-state waveform capture manually by selecting the circuit monitor and issuing the acquire command. SMS will automatically retrieve the waveform capture from the circuit monitor. You can display the waveform for all three phases, or zoom in on a single waveform, which includes a data block with extensive harmonic data. See the SMS online help for instructions.

Use the disturbance waveform capture to record events that may occur within a short time span such as multiple sags or swells. The circuit monitor initiates a disturbance waveform capture automatically when an alarm condition occurs (if the alarm is set up to perform the waveform capture). The trigger may be from an external device such as an protective relay trip contact connected to a digital input or voltage sag alarm, or you can also initiate the waveform capture manually from SMS at any time.

In SMS, for the disturbance waveform capture, you select the sample rate and how many cycles and pre-event cycles the circuit monitor will capture (see Table 8–1):

Table 8–1: Available Resolutions for Disturbance Waveform Captures

Samples per Cycle (Resolution)	Max Duration
16	915 cycles
32	457 cycles
64	228 cycles
128	114 cycles
256	57 cycles
512	28 cycles

See the SMS online help for instructions on setting up disturbance waveform captures.

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