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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Combination of series and parallel resistances, usually in the form of a wire break. The circuit is shown in the figure at right.
The van is installed with conventional cable measuring systems for quickly reaching the location of any cable fault. Impedance changes at the fault location make measuring more difficult. At the balance condition, When the cross section area of the both sound cable and faulty cable are equal, then the resistance of the conductors are directly proportional to their lengths.
This article may rely excessively on sources too closely associated with the subjectpotentially preventing the article from being verifiable and neutral. Articles needing additional references from July All articles needing additional references Articles lacking reliable blavief from November All articles lacking reliable references Articles with multiple maintenance issues.
The necessary connection of the Varley loop test is shown in figure 4 and 5.
Blavier Test | Murray Loop Test | Varley Loop Test | Fisher Loop Test
These waves are reflected at the cable ends so that they then travel toward each other again in the direction of the cable fault. In the fault location, the conductor is shorted to ground, because of fault.
There are various ways to decouple and analyse these transients. Due to this temperature effect, the resistance of the cable would change. Two balancing are necessary as per the two different circuits.
The resistance between the sending end to the fault end is mentioned as x and the resistance blaviet the fault end to the far end is denoted as y.
This expression gives the resistance from the sending end to the fault location. Test sets for cable testing can be connected for either bridge tewt.
This page was last edited on 5 Augustat From Wikipedia, the free encyclopedia. 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 tesg cable and the action of the current at the fault condition.
So, the total resistance L is equals to the addition of x and y resistances. Please help improve this article by adding citations to reliable sources. In this process, mobile shock discharge generators are among the devices used. There are predominantly two methods for this. The two ends faulty cable are mentioned as sending end and boavier end respectively as tset in fig 1.
An insulation test measures the insulation resistance between conductor and screen; from the periodic measurement of resistance you can derive the absorption properties of the insulating material. In Murray Loop Testthe fault resistance is fixed and it may not be varied.
In cable identification, the faulty cables are identified from the fault-free cables at the already determined site.
Connects Lbavier Youtube Videos. 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 blagier the line.
To perform this test, it is necessary to have a sound cable running alongside the faulty cable. Please blqvier improve it by replacing them with more appropriate citations to reliable, independent, third-party sources.
But practically, this is not possible. The similar Varley loop uses fixed resistors for RB1 and RB2, and inserts a variable resistor in the faulted leg. The corresponding distance is calculated by known resistance per unit length of the cable.
Cable fault location
If the fault resistance is high, the sensitivity of the Murray bridge is reduced and the Varley loop may be more suitable. 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. If the switch S is in position 2, then again we need to adjust the variable resistance R to balance the bridge circuit.
In addition to pulse reflection method and transient method, there are two popular loop tests for finding the location of faults in underground cables. Sheath faults are damage of the cable sheath that allows the surroundings contact with the cable screen.
Cable fault location – Wikipedia
G is the galvanometer to indicate the balance. 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. These methods of cable fault location quickly became established in Western Europe as well. Route tracing teat used to determine where the faulty cable lies and pinpointing is the process of determining the exact position of the cable fault.
In the transient method, a breakdown is triggered at the cable fault. This article has multiple issues. Water penetrates into the cable sheath and contacts the conductors. 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.
Now, blafier 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.
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. Then the current circulation through the cable would cause temperature rises due to high voltage or high current.
This effects a low-resistance short circuit for a few milliseconds.