What are String Performance Alerts?

String Performance Alerts allow users to set value, time, and buffer thresholds to analyze performance at the string level. These alerts work by analyzing  strings relative to the highest-performing string of the same component to highlight underperforming strings. These alerts are available for any component that measures String DC Current.

In order to configure String Performance Alerts, the user must first configure Data Fields for the component.  After configuring Data Fields, String Performance Alerts will show up under Alert Settings in the Config page for the specific component and can be enabled and configured there. 

Data Fields are available under Config for any component that measures String DC Current.  Data Fields allow users to disable (hide) strings that are not being used and to configure Normalized String DC Current. After enabling/disabling strings in the Measured section, the Modeled section allows users to Normalize the strings based on system design.  This allows for relative comparisons of differently sized strings.  The default Normalization factor is 1, which assumes all strings are equal and will show the same value of the Measured DC Current, but the user can enter a ratio based on number of panels per string or DC capacity per string for example.
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Once Data Fields are configured for a particular component, a section for String Performance Alerts will appear in the Alert Settings form under Config.  At least two Normalized String DC Current fields must be enabled in order for this section to appear as this is the data field used to calculate the alert.
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Within the alert settings for String Performance Alerts, users will find the following options:

Enable String Performance Alerts:

This box will show up after Normalized Data Fields have been configured and will allow the user to enable the String Performance Alerts.

String Performance Ratio:

Represents the ratio relative to the highest performing string. For any string performing below this value for the set time threshold, a String Performance Alert will open. Allowed values are 0.0 to 1.0 and the default is set to 0.8, or 80%.  

Time Threshold:

The string performance condition must continue for the time period defined by this threshold before generating an alert. Only daylight hours are considered. Allowed values are 0.25 to 168 hours and the default is set to 2 hours.

DC Current Threshold:

The measured DC Current, in amps, for the highest performing string must exceed this value in order to generate any String Performance Alert.  The default is set to 2 amps.

Sunrise/Sunset Buffer:

This buffer adds additional hours after sunrise and before sunset to ignore alert conditions. Allowed values are 0.0 to 4.0 hours and the default is set to 0.5 hours.

For example:

We set the String Performance Alert to use the default values:  The String Performance Ratio is set to 0.8, the time threshold is set to 2 hours, the Minimum DC Current is set to 2 amps, and the Sunrise/Sunset buffer is set to 0.5 hours.  The String Performance Alert generator runs every 4 hours and analyzes each 5-minute data point from the previous time period to determine whether to open new alerts or close existing alerts.  The alert generator will look at 5-minute Normalized String DC Current to analyze the relative performance of each string compared to the highest-performing string.  For simplicity, let’s say the highest-performing string has a value of 10 and that this is consistent for2 hours.  Any string that consistently measures less than 8 for that 2 hours will generate a String Performance Alert.

Once String Performance Alerts are configured, users can begin to see them throughout the LocusNOC platform.