Cable Hipot Test: Safety Assurance of Electrical Installations
Electricity in safe, closed systems brings convenience to modern life. When those systems fail, the consequence may not only be inconvenience, but also harsh electric shock. The electrical industry has developed numerous practices to ensure safety. One such practice is the cable hipot test (high possible test).
This test is a method of testing the integrity of the insulation of electrical cables. It is performed to expose any possible problems in an electrical cable or system that could cause harm or shock.
This kind of testing will expose weaknesses in electrical cables and insulation that may not be seen under normal operating conditions using standard voltage levels. These problems may appear in the cables themselves, in addition as in splices and terminal connections. possible weaknesses include cracked insulation, unattached wires, and conductive contaminants.
In order to find problems in a system, higher than normal voltage is sent by cables during this test. Testing units monitor the excess voltage being introduced by a system while simultaneously measuring the leakage current. Leakage indicates near shorts that leak voltage during the test due to the excessive current being applied. These near shorts can indicate trouble spots, such as poor insulation or installation errors.
There are different types of hipot testing. An insulation resistance test is used for cables to show the resistance of cable insulation. This test uses steady DC current. It is more accurate and safer to use DC current for such a test than to use AC current. In addition, DC testing equipment is more portable and much less expensive than AC testing equipment.
There are two specific situations when cable hipot tests are administered. One is to test new installations, and the other is to test existing systems.
Special consideration is required when testing older electrical systems. Excess current may damage the aging insulation of certain types of cables. This kind of testing is not recommended by the electrical industry for cross-connected polyethelene (XLP) or ethylene propylene rubber (EPR) cables that have been in use for more than five years. However, paper insulated rule covered (PILC) cables with over five years of service may be tested with DC testing units.
By sending excess voltage by electrical cables, it is possible to find possible problems that would not appear during normal operation with standard current levels. The cable hipot test is an highly useful way to give electrical professionals a clear view of the quality and safety of their installations.