short circuit fault
Concept: Murray loop test: It is the common method to determine location of earth or short circuit fault in cable. It operates on the principle of Wheatstone bridge.
What are the limitations of Murray loop test?
Thus the position of the fault is located. Note that resistance of the fault is in the battery circuit and not in the bridge circuit. Therefore, fault resistance does not affect the balancing of the bridge. However, if the fault resistance is high, the sensitivity of the bridge is reduced.
What are the most common test in UG cables?
The Murray loop test is the most common and accurate method of locating earth fault or short-circuit fault in underground cables.
Which type of fault of UG cable can be located by this loop test?
Varly loop test is a test by which we can locate the earth fault or short circuit fault in the underground cable.
What is Murray loop method?
Murray loop test is the most common and accurate method for locating earth faults and short-circuit faults. To perform the Murray loop test, the alongside sound cable and the faulty cable are shorted with a jumper conductor at the far end. The test side end is connected through a pair of resistors to a voltage source.
How do I find my cable fault?
To find the location of cable fault using the thumping method, a thumper is set to thump repeatedly and then walking along the cable route to hear the thumping sound. The higher the dc voltage applied, the louder will be the resulting thump. This method is useful for relatively shorter cables.
What is 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. But we should use the known length of the cables in this experiment.
What is Murray test?
Murray loop test is the most common and accurate method for locating earth faults and short-circuit faults. This test employs the principle of Wheatstone bridge for fault location. To perform the Murray loop test, the alongside sound cable and the faulty cable are shorted with a jumper conductor at the far end.
What is Fisher 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 instead of calculating it from the known lengths of the cable. The necessary connection of the Varley loop test is shown in figure 4 and 5.
Which test is used for locating cable fault?
1. Blavier Test (For a Single Cable Faults) When a ground fault occurs in a single cable and there is no other cables (without faulty one), then blavier test can be performed to locate the fault in a single cable.
What is the difference between Murray and Varley loop test?
The main difference between Murray and Varley loop test is that in the Murray test we obtain the total loop resistance by the relation R = ρ l/a. But in the case of the Varley test, we have the provision of measuring the total loop resistance instead of using the relation of the resistance.
What is the purpose of bedding insulation of UG cable?
Bedding. Over the metallic sheath is applied a layer of bedding which consists of fibrous material like jute or hessian tape. The purpose of bedding is to protect the metallic sheath against corrosion and from mechanical injury due to armoring.
What is the necessary connection of the Murray loop test?
The necessary connection of the Murray loop test is shown in figure 2 and 3. 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.
What is the necessary connection of the Varley loop test?
The necessary connection of the Varley loop test is shown in figure 4 and 5. The figure 4 shows that the circuit connection for finding the fault location when the ground fault occurs and the figure 5 shows that the circuit connections for finding the fault location when the short circuit fault occurs.
How to perform Fisher loop test for cables?
In this Fisher Loop Test, there must be two healthy sound cables which must have the same length and same cross sectional area as the faulty cable. As per the Fig.6 and 7 circuit diagram, all the three cables are connected by a low resistance wire. In the Fig.6 circuit connection, the bridge connection is connected to ground.
