Pre-commissioning electrical tests for overhead powerlines 1

[KillBill7]

Hello Everyone.. what are the typical re-commissioning electrical tests for overhead powerlines? I understand for long distance HV (230kV and higher) you would normally perform phase sequence/rotation check, sequence impedance tests, conductivity tests and footing resistance tests. My question is there any merit to do all these tests on medium voltage lines like 34.5kV , except footing resistance tests?

 

[Paulsey88]

Not so much recommissioning, but experience with voltage conversions (upping voltage). The eng-tips thread pasted below sums it up well. Typically there is not an electrical test per se. The line is visually expected in detail (ultrazoom camera or drone, binoculars minimum) to verify presence, integrity, and rating of insulators. Verify structures and structure components for integrity or damage. Inspect conductors for damage, missing jumpers, etc.. Check that pole grounds, bonding, etc. are intact and present. Test footing resistance if needed. If arresters are present on the line they should be replaced. Clearances are a big component as well. Visual inspection minimum, LiDAR and checks using PLS-CADD preferable, especially if upping the voltage or recent changes in code/standards dictate greater clearances.
user Marmite in the thread below has a great tip. Energization through a protective device that is fault make/break rated. On distribution voltages the use of a recloser with the ability to soft reclose may be beneficial.

https://www.eng-tips.com/viewthread.cfm?qid=191559

 

[bacon4life]

Definitely check for correct phase rotation and phase sequence before closing any loops or picking up any loads.

I am interested in what kind of sequence impedance checks and conductivity checks you are thinking of. As far as I was aware, measuring sequence impedance is very cutting edge stuff using PMU data from both ends of an energized line.

 

[KillBill7]

I have seen guys doing the conductivity test by shorting the three phases together from one end and then using insulation tester MEGGER to apply 5kV DC between two phases and observe the reading.

 

[Maximillianrichards]

Hi!

Re-commissioning tests on overhead medium voltage (MV) power lines typically include:

[ol 1]
[li]Continuity tests: This test verifies the electrical connectivity of all conductors, including the ground wire.[/li]
[li]Insulation resistance tests: This test measures the resistance between each conductor and ground, which provides an indication of the overall insulation health of the system.[/li]
[li]Ground resistance tests: This test measures the resistance of the ground wire, which is an important safety feature that protects people and equipment from electric shock.[/li]
[li]Line impedance tests: This test measures the impedance of the power line, which helps to identify any potential load balancing or power quality issues.[/li]
[li]Phase balance tests: This test verifies that the voltage and current levels on each phase are balanced, which helps to ensure that the power system is operating efficiently.[/li]
[li]Voltage drop tests: This test measures the voltage drop along the length of the power line, which can help to identify any areas where the voltage may be too low, which could cause equipment to malfunction or fail.[/li]
[li]Power factor tests: This test measures the power factor of the system, which is a measure of how effectively the power is being used. Low power factor can indicate that the system is not operating efficiently, which can lead to increased energy costs.[/li]
[li]Voltage and current waveform tests: This test measures the shape and stability of the voltage and current waveforms, which provides valuable information about the power quality and stability of the system.[/li]
[/ol]

While footing resistance tests are typically not performed on medium voltage power lines, it's important to consult with the power company and relevant standards to determine the appropriate tests for your specific situation.

https://www.asutpp.com/

 

[bacon4life]

Interesting. I had not considered using a 5 kV megger since I have seen way more 5 kV of stray voltage on a sections of de-energized 115 kV lines that were in close proximity to energized 115 kV lines.