After a power or distribution transformer is disconnected from the power grid or when DC current is applied, such as when a routine winding resistance measurement test is performed, the transformer core is likely to have some remnant magnetism. This remnant magnetism will increase the magnitude of the already high inrush over current levels seen when a transformer is energized. …
Advancements in the Industry — Acceptance and Maintenance Testing for Medium-Voltage Electrical Power Cables — Part 3 of 3
In Part 2 of our three-part series on acceptance and maintenance testing for medium-voltage electrical power cables, we explored high-potential testing techniques, including tests performed with direct current (DC) and alternating current (AC) performed at power frequency and at very low frequency (VLF). We also explored diagnostic testing and reviewed dissipation factor (tan delta) testing. In Part 3, we …
Advancements in the Industry: Acceptance and Maintenance Testing for Medium-Voltage Electrical Power Cables — Part 2 of 3
In Part 1 of our three-part series on acceptance and maintenance testing for medium voltage electrical power cables, we reviewed cable construction and cable aging characteristics and started our discussions on cable testing options and philosophies. In Part 2 of this article, we move away from undervoltage testing and explore high potential testing techniques. HIGH POTENTIAL TESTING PERFORMED WITH DIRECT …
Acceptance and Maintenance Testing for Medium-Voltage Electrical Power Cables – Part 1 of 3
As time progresses and a cable system ages, the system’s bulk dielectric strength degrades. During this aging process, artifacts such as water trees, delamination, voids, and shield corrosion raise the local stress placed on the cable during normal operation. The exact way in which the strength of a device degrades will depend upon many factors including voltage, thermal stresses, maintenance …
Advancements in the Industry: Who Is Qualified and Who Isn’t When It Comes to Electrical Safety?
Electricity is a powerful force that can cause serious injury and death. When it comes to electrical job tasks, it only takes an instant to turn a momentary mistake into a life-altering event or even fatality. Therefore, qualified electrical workers must understand the hazards presented by exposed energized parts and know how to protect themselves using safe electrical work practices. …
Acceptance and Maintenance Testing Medium-Voltage Electrical Power Cables
As time progresses and a cable system ages, the system’s bulk dielectric strength degrades. During this aging process, artifacts such as water trees, delamination, voids, and shield corrosion raise the local stress placed on the cable during normal operation. The exact way in which the strength of a device degrades depends upon many factors including voltage, thermal stresses, maintenance practices, …