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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These waves are tesst at the cable ends so that they then travel toward each other again in the direction of the cable fault. The circuit is shown in the figure at right. But we should use the known length of the cables in this experiment. The bridge is brought to balance by changing the values of R B1 and R B2. This article may rely excessively on sources too closely associated with the subjectpotentially preventing the article from being verifiable and neutral.

This in turn produces two travelling waves diffusing in opposite directions. Water penetrates into the cable sheath and contacts the conductors.

Cable fault location

If the resistance varies according to the temperature, then the balance collapses. Murray loop test employes the principle of wheatstone bridge for locating the fault. From Wikipedia, the free encyclopedia. The waves bblavier 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 due to the burning short circuit results in a reversal of polarity.

By solving the above three equation and eliminating g and y. Fisher Loop Test In this Fisher Loop Testthere must be two healthy sound cables which must have the same length and same blavief sectional area as the faulty cable.

As per the Fig. These methods of cable fault location quickly became established in Western Europe as well.


Then the current circulation through the cable would cause temperature rises due to high voltage or high current. The conventionally used aid in cable fault testing and location is the cable test van. Combination of series and parallel resistances, usually in the form of a wire break. July Learn how and when to remove this template message.

Due to this temperature effect, the resistance of the cable would change.

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

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. This article needs additional citations for verification.

Also it is difficult to set the bridge as balance. This expression gives tes resistance from the sending end to the fault location.

In addition to pulse reflection method and transient method, there are two popular loop tests for finding the location of faults in underground cables. The corresponding distance is calculated by known resistance per unit length of the cable. Cable faults are damage to cables which effect a resistance in the cable. The figure 2 shows that the circuit connection for finding the fault location when the ground fault occurs and the figure 3 shows that the circuit connections for finding the fault location when the short circuit fault occurs.

Languages Deutsch Edit links. The voltage is interrupted, i. 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 shall find out the fault location. 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.

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

So, if L X represents the length between test end to the fault end of the faulty cable and if L represents the total length of the both cables, then the expression for L X is as follows; The above test is only valid when the lengths of the cables are known. Two balancing are necessary as per the two different bllavier.


One end of the faulted cable is connected through a pair of resistors to the voltage source. Connects Facebook Youtube Videos. Cable testing is therefore usually performed first in cable fault location. Thus, the determination of the fault position is not accurate. There would be fractional changes in the bridge arms. If the fault resistance is high, the sensitivity of the Murray bridge is blavirr and the Varley loop may be more suitable.

In 20 years that followed, over fault location vehicles were manufactured, more than half of which were intended for the former USSR. So, the total resistance L is equals to the addition of x and y resistances. Also, the resistance g may be so high that it exerts very little shunting action when y is placed in parallel with it by grounding the far end of the line. This effects a low-resistance short circuit for bavier few milliseconds. Cable fault location is the process of locating periodic faults, such as insulation faults in underground cablesand is an application of electrical measurement systems.

So, we need to apply less blaver or less current to this circuit. A practical difficulty in Blavier’s test is that the resistance to ground g is blacier, being influenced by the amount of moisture present in the cable and the action of the current at the fault condition. In this test, the faulty cable is connected with sound cable bpavier a low resistance wire, because that resistance should not affect the total resistance of the cable and it should be able to circulate the loop current to the bridge circuits without loss.