Are the Blavier test and Fischer test for fault localization also loop tests based on the Wheat stone bridge principle??? Please add a brief explanation about their. Types & causes of Cable Faults, Blavier Test Earth Overlap Test Potential Fall Test Fisher Loop Test Open Circuit Test Murray Loop Test Varley. other faulty cable while in Blavier test you need only faulty cable sample. Apparatus: Blavier test board Portable bridge Connecting wires Circuit Diagram: .

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Water penetrates into the cable sheath and contacts the conductors.

By using this site, you agree to the Terms of Use and Privacy Policy. The conventionally used aid in cable fault testing and location is the cable test van. The necessary connection of the Murray loop test is shown in figure 2 and 3.

In cable identification, the faulty cables are identified from the fault-free cables at the already determined site. The voltage is interrupted, i. But practically, this is not possible. Please help improve it by replacing blabier with more appropriate citations to reliable, independent, third-party sources.

Unsourced material may be challenged and removed. Balance of the bridge is tesr by adjusting the variable resistors. These tet are reflected at the cable ends so that they then travel toward each other again in the direction of the cable fault. In 20 years that followed, over fault location vehicles were manufactured, more than half of which were intended for the former USSR.

This expression gives the resistance from the sending end to the fault location. The blavieg resistor s R 1 and R 2 are forming the ratio arms.


Cable fault location – Wikipedia

Sheath faults are damage of the cable sheath that allows the surroundings contact with the cable screen. The similar Varley loop uses fixed resistors for RB1 and RB2, and inserts a variable resistor in the faulted leg. A practical difficulty in Blavier’s test is that the resistance to ground g is variable, being influenced by the amount of moisture present in the cable and the action of the current at the fault condition.

Thus, we need to apply less current to this circuit to carry out the experiment. If the switch S is in position 2, then again we need to adjust the variable resistance R to balance the bridge circuit.

At this position, the expressions are as follows; By solving the equation 1 and 2Therefore, the unknown resistance R X is, Varley Loop Test is valid only when the cable sections are uniform throughout the loop. The necessary connection of the Varley loop test is shown in figure 4 and 5.

The total resistance of the entire loop of the above circuit is nothing but R 2 — the conductor resistance between sending end and earth by keeping far end earthed.

Route tracing is used to determine where the faulty cable lies and pinpointing is the process of determining the exact position of the cable fault.

The resistance usually lies in the high-ohmic range. Articles needing additional references from July All articles needing additional references Articles lacking reliable references from November All articles lacking reliable references Articles with multiple maintenance issues. Due to this temperature effect, the resistance of the cable would change.

Blavier Test | Murray Loop Test | Varley Loop Test | Fisher Loop Test

The waves are unable to pass the fault because of the arc produced by the short circuit, so they are therefore reflected back again as with the pulse reflection method, which tesg to the burning short circuit results in a reversal of polarity. Thus, this short circuit may have some resistance that is mentioned as g.


Impedance changes at the fault location make measuring more difficult. Let us assume that the new R value as R S2.

Blavier Test | Murray Loop Test | Varley Loop Test | Fisher Loop Test

These methods of cable fault location quickly became established in Western Europe as well. Also it is difficult to set the bridge as balance. Please help improve this article by adding citations to reliable sources. From Wikipedia, the free encyclopedia.

So, the total resistance L is equals to the addition of x and y resistances. There are predominantly two methods for this. Then the current circulation through the cable would cause temperature rises due to high voltage or high current. The van is installed with conventional cable measuring systems for quickly reaching the location of any cable fault. Now, the total resistance of the x and g loop is nothing but R 1 — the conductor resistance between sending end and earth by keeping far end open.

Murray Loop Test This test is used to find the fault location in an underground cable by making one Wheatstone Bridge in it and by comparing the resistance we blavvier find out the fault location. Views Read Edit View history.

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