How to do a short-circuit or earth leakage test on a line with a multimeter
The use of a multimeter to measure the short circuit is very convenient, with a multimeter to measure the grounding is not so accurate, in fact, should be used to shake the meter is the most reasonable, the following to give you an introduction to how to use a multimeter to check the line when the short circuit or grounding.
First to say to you about the short circuit: in fact, the problem itself is problematic, we know that the line of the short circuit refers to the normal operation of the power system outside of the phase and the phase between, phase and the ground between the connection; so the phase line of the grounding is also considered a short-circuit one, the zero line if the grounding of the leakage current will be generated, leakage protector tripped, so the question is not very rigorous, personal understanding of the question he wanted to ask the line of the short-circuit and leakage of power how to Detection.
1. How to use a multimeter to detect a short circuit in the line
(1) first power off, the multimeter function switch to the buzzer gear, the multimeter two pens on the two terminals to be measured bai test, if short-circuit will have a beeping sound, and shows a small on-state voltage value, this time between the two points to be measured short-circuit.
(2) using a multimeter to measure the line insulation can know whether the line is short-circuited. For example, measuring single-phase ground insulation, if the insulation value is zero (metallic grounding) or very low (non-metallic grounding), you can judge this phase of the line grounded. If it is not grounded, the insulation value is high. Then measure the insulation between phases, if the insulation between phases is zero, it means that this two-phase line is a short circuit between.
(3) to ensure that there is no electricity in the line, the resistance file (pointer meter put RX10 file, digital meter will call the on and off file), the two meter stick contact to measure the two points (or two lines), the pointer meter does not move is a circuit breaker, the fullness of the dump over is a short-circuit; digital meter circuit breaker digital no change, there is no sound, the short-circuit will be called, or the number of zeros.
(4) will be separated from the two ends of the wire core, do not touch each other, and then the multimeter hit and above the position, the pen were hitched to the two different colours of the line, if the measured value is above 0.5 megohm, or show infinity, then the insulation of the line is not a problem, that is, the line does not exist leakage; if the measured value of the results is 0.5 megohm or less, then the line insulation is unqualified If the measurement result is below 0.5 megohm, then the line insulation is not qualified, and there is leakage. Find all the joints and junction boxes in the line after this air open, whether the joint insulation is not good, and then resistance measurement method at each joint and junction box with a multimeter check. The reason is that the short-circuit moment generates a high current air switch automatically tripped, the line will not burn out how much general situation in the joints or junction boxes to resistance measurement method is able to determine the location of the short circuit. 2.
2. how to detect a short circuit or grounding
But I still press in the absence of circuit breakers and leakage circuit breakers under the protection of the gate switch distribution line how to detect is a short circuit or grounding to answer the question; (in fact, the gate switch distribution if there is a short circuit on the line; the consequences of its either burned off the wire is burned out of the gate switch, nevertheless; I am still according to the principle of detection to answer the question).
(1) the power distribution line at the beginning of the power switch off, all the load switch on the line disconnected, including plugged in the socket plug load separation, with a multimeter resistance × 100 gear measurement of the power switch out of the end of the two wires out of the resistance, if it is measured to the multimeter resistance is very small (i.e., the pointer to the right swing almost the end of the end), then prove that there is a short-circuit phenomenon between the phase line and the zero line, or else it is not a short-circuit. Otherwise, there is no short circuit. The same test method to measure the phase line to the protective ground (zero) line, zero line to the protective ground (zero) line whether there is a short-circuit phenomenon.
(2) If you exclude the phase line to the zero line, phase line to the protective grounding (zero) line, zero line to the protective grounding (zero) line no short-circuit phenomenon, you can test the phase line and the zero line whether the grounding phenomenon.
Detect grounding if you have a clamp meter on hand is best to use a clamp meter to detect grounding current. Detection method is: first disconnect the power switch, the distribution of zero line from the power switch from the end of the line removed (and mark), and then close the power switch, with a clamp meter clamp measurement of the phase line with or without grounding current (clamp meter first dialled to the 100A file such as the current can not be detected and then slowly dialled to the smaller current gear) if still not measured grounding current; can be excluded from the phase line grounding. After testing the phase line, disconnect the power switch to remove the phase line, connect the zero line to the power switch on the phase line out of the contact point, close the power switch with the above clamp meter to measure the phase line method of testing the zero line.
