Sag Directivity Answer Module

The Sag Directivity Answer Module® is an optional add-in module for PQView that accepts any device compatible with PQView that provides voltage and current waveform data.

Identifying the Source of Voltage Sags Is Key

Traditionally one of the most common power quality problems, voltage sags, which are also known as voltage dips or rms voltage variations, are capable of causing hours of downtime. For today’s computer-dependent businesses, even the smallest sags can produce substantial problems, from loss of data to disruption of the production line. Because voltage sags can be caused by multiple factors, both by internal events such as the start-up of a large load or by a fault on the power system itself, they have been difficult to address. Key to resolving the problem is identifying the source of the problem — and whether that problem is inside the facility or in the distribution network of the supplier. Within the facility, the Sag Directivity Answer Module can determine where the sag occurred in relation to the monitoring location.

Voltage Sags Are Identified and the Fault is Located

The Sag Directivity Answer Module detects a voltage sag event, identifies its characteristics and determines the direction of its location relative to the monitoring point. The Answer Module is invoked when both waveform samples are present. Using proprietary techniques, the Answer Module compares rms magnitudes computed from both current and voltage waveforms, tracking positive sequence phase angle changes from pre-fault to post-fault. Based on this data, the direction of the fault is determined with a high degree of accuracy, enabling power customers to determine whether the fault occurred upstream or downstream of the monitoring point.

Voltage Sag due to an Upline Transmission FaultVoltage Sag due to a Downstream Distribution Fault 

Details Available in PQView

The details of each rms voltage sag are added to the details of the event and are available in within PQView's reports. Just as important, the information can be shared with colleagues and customers who have access to the Internet. The Voltage Sag Directivity Answer Module does not require users to enter specific setup information, allowing for fast-track startup.

The Voltage Sag Directivity Answer Module employs the same technology available in the Dranetz Signature System® and Encore® Series System.