Published by Jonny Carlsson, Unipower AB, Case Study: Example of Frequency Variations causing SlowScan Recording, Date: October 25th, 2011. http://www.unipower.se
In the following examples a Unipower UP2210 Power Quality meter is measuring SlowScan events. The SlowScan trig level is set to 50Hz +- 0.15Hz with a recorder time of 120 seconds.
Example 1:
The voltage level is going up and at the same time the frequency goes up to about 50.17 Hz. In this case additional electrical production may have been connected. After about 20 second the frequency is stabilising.
Example 2:
A frequency change below 49.85 Hz starts the SlowScan recording. After 55 seconds there is a voltage drop lasting for about 8 seconds. After the voltage drop the frequency varies and then stabilise. This is probably caused by a short circuit and tripping of a protection of a large load. During the fault additional electrical production is added which after the clearing of the fault lead to increased frequency.
Example 3:
A rapid frequency change above 50.15 Hz starts the SlowScan recording. After reaching 50.3Hz the frequency varies and then stabilise. This could be caused by a disconnection of a large load.
Example 4:
A rapid frequency drop to about 49.5 Hz starts the SlowScan recording. The drop has duration of about 7.5 second until the frequency start recovering. A high dF/dt of 0.12 Hz/s is measured. A variation in the voltage can also be seen. This is probably a unplanned disconnection of a large electric producer.
Unipower SlowScan
Unipowers unique SlowScan feature allows capturing of Power Quality events with a recording time of up to several minutes and a rms rate of 10-100 times/second. This feature excels at capturing slow events in the grid.
About Unipower: Unipower AB offers a wide range of products for Power Quality measurements and Smart Grid systems.
Originating from a Swedish ABB company in the mid 80’s, Unipower has developed a competitive edge within the field of Power Quality and Smart-Grid solutions. We focus on norm compliance equipment, with a special focus on the requirements for power generation, transmission and distribution.
Our product lines reach from traditional portable PQ analysers to fully integrated and automated Power Quality Management systems for continuous supervision of the energy supply.
Website: unipower.se
Unipower Permanent – UP2210
• The UP-2210 unit works as an advanced power quality meter and at the same time as a fault recorder. All of the power quality parameters can be analyzed in accordance with voltage quality standards such as the EN 50160 or national regulations such as the Swedish EIFS. The UP-2210 unit captures both steady state disturbances (harmonics, flicker etc.) as well as rapid voltage changes (sag/swell events and fast transients). The nodes in the PQ Secure system consist of UP-2210 meters.
• Advanced 3-phase Power Quality and Transient Monitor
• The UP-2210 is a full-featured, norm-compliant power quality monitor capable of detecting any disturbances encountered in a network.
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