①Determine the formula of alternating current and direct current
The electric pen judges AC and DC, AC is bright and DC is dark,
The AC neon tube is bright through the whole body, and the DC neon tube is bright at one end.
illustrate:
First of all, let the readers know that before using the low-voltage test pen, it must be tested on a confirmed charged body; it should not be used until the test pen is confirmed to be normal. When judging AC and DC, it is best to make a comparison between the "two powers", so that it is obvious. When measuring alternating current, both ends of the neon tube light up at the same time, and when measuring direct current, only one end of the neon tube is extremely bright.
②The formula for judging the positive and negative poles of direct current:
The electric pen judges the positive and negative poles, and observe the neon tube carefully.
The front bright is negative, the rear bright is positive.
illustrate:
The front end of the neon tube refers to the tip of the test pen, and the rear end of the neon tube refers to the end of the hand. The bright front end is the negative electrode, and vice versa. Pay attention when testing: the power supply voltage is 110V and above; if the person is isolated from the earth, touch either pole of the power supply with one hand, and hold a test pen with the other hand. If it is bright, the measured power supply is the negative pole; if the back end of the neon tube is extremely bright, the measured power supply is the positive pole.
③ Judging whether the DC power supply is grounded or not, the difference between positive and negative grounding
The DC coefficient of the substation, the electric pen does not light up;
If the light is close to the tip of the pen, the positive pole has a ground fault;
If the light is close to the finger end, the ground fault is at the negative pole.
illustrate:
The DC coefficient of power plants and substations is insulated from the ground. People stand on the ground and touch the positive or negative pole with an electroscope. The neon tube should not light up. If it lights up, it means that the DC system is grounded. ; If the light is on the end near the tip of the pen, it is the positive ground; if the light is on the end near the finger, it is the negative ground.
④ Judgment of in-phase and out-of-phase formulas
Judging that the two lines are the same and different, hold a pen in each hand,
The two feet are insulated from the ground, and each of the two brushes touches a line.
Look at a pen with your eyes, if it doesn't shine, it's different.
illustrate:
During this test, remember that both feet must be insulated from the ground. Because most of our country is powered by 380/220V, and transformers generally use the neutral point to be directly grounded, so during the test, the human body and the ground must be insulated to avoid forming a loop to avoid misjudgment; during the test, the two strokes are on and off. The bright display is the same, so just look at one.
⑤ The formula for judging the ground fault of the phase line of the 380/220V three-phase three-wire power supply line
Star connection three-phase line, the electric pen touches two lights,
The remaining one is weak in brightness, and the phase wire has been grounded;
If there is almost no light, the metal grounding fault.
illustrate:
The secondary side of the power transformer is generally connected in a Y shape. In a three-phase three-wire system where the neutral point is not grounded, when the three phase wires are touched with an electroscope, two of them are slightly brighter than usual, while the brightness on the other one is slightly brighter. If it is weaker, it means that the weak phase wire has a grounding phenomenon, but it is not too serious; if two are very bright, and the remaining one is almost invisible, it means that this phase wire has a metal ground fault.
