Overview of Frequent Field Tests
Area tests can be broadly grouped into three categories: acceptance, maintenance and fault location testing. Performed on wire or cable after an installation however before putting it into service, an acceptance test detects installation or shipping damage that may have an effect on cable performance. After the cable has been positioned in service, upkeep tests detect in-service deterioration. However, fault location tests pinpoint the exact failure site in a cable. Figuring out exactly the place the cable has failed, permits the Belden Cable Equivalent Manufacturer to be repaired or replaced as necessary. A few of the most typical test methods are described below.
A Megger test makes use of a megohm meter to test the insulation properties of such things as electrical wiring, motor windings and high-energy antenna mounts. Usually performed on 600-volt energy cable for either acceptance or upkeep functions, a megohm meter typically applies 600 to 2,500 V DC for several minutes to the cable. The megohm meter measures the current “leaking” through the insulation and displays the results in models of resistance (i.e., megohms or tens of millions of ohms). A reading less than a hundred megohms signifies a possible cable problem. Despite the fact that Megger is a registered trademark of Megger Limited Group, the time period is broadly used for all related tests regardless of manufacturer.
The hipot (high potential) test is an acceptance or maintenance test and is normally used on cables rated 5 through 35 kV and higher. Just like the Megger test, this gadget applies DC voltage to a cable and measures current leakage by way of the insulation. In contrast to the Megger test, the utilized voltage is considerably higher (as much as sixty five kV for a 15 kV cable, for instance) and the results are displayed in items of microamps (μA). With the hipot test, a high reading (for instance larger than a hundred μA) signifies a attainable problem. Because of the doubtless deadly high voltages concerned, this test must be carried out solely by certified personnel.
The continuity test, which can be used on virtually each type of wire and cable except optical fiber, is probably the easiest and least expensive discipline test available. A handheld multimeter conducts the test by using a resistance setting to check the wire or cable for unintentional contact between copper conductors as a result of damaged or defective insulation. A multimeter can also be used to check for conductors which were broken someplace along the cable’s length. The continuity test can be used for acceptance, upkeep or fault location testing.
A thumper is a fault location gadget that applies a high-voltage pulse to a cable to find out the precise location of a cable failure. It really works by making use of a quick (millisecond) high-energy pulse to the cable. At the level of the cable failure, the injected energy is launched with a loud bang just like that of a firecracker. When the test is carried out on cable buried several toes underneathground, a muffled thump is usually heard above ground. The cable is often thumped several times a minute till someone walking the size of the cable run can find the point of failure.