In the communication circuit, the wire that can make the neon tube glow after being touched by the electroscope is the phase wire, and the wire that does not shine is the zero wire. But when the zero line is abnormal (such as the zero line is cracked and the load is asymmetric), it is outside.
(2) The unevenness of the differential voltage or the absence of leakage and induced voltage.
The unevenness of the voltage can be estimated according to the strength of the neon tube. The brighter the neon tube, the higher the voltage; the darker the neon tube, the lower the voltage (note: it is difficult to distinguish the light intensity of the neon tube in bright light). For the 380/220V power supply system, if the neon tube is dark, it may be equipment leakage or induced electricity. This kind of difference method can only be compared with the same electroscope (because the ignition voltage of the neon tube of different electroscopes is different), and the inspector needs to have certain experience.
The neon tube is bright, and it is doubtful whether the object is really charged or is leaking and induced electricity. Usually, you should not touch the object with your hands (even if you touch it, you should use the back of your hand, because if there is electricity, the muscles of your hands will be shortened, and you will not be able to touch it. It will catch the conductor and cause an electric shock), but should be checked with a multimeter or a light bulb (the bulb voltage should be the same as the power supply voltage).
(3) Difference between alternating current and direct current.
When measuring the electric current, the base of the neon tube will light up; when measuring the direct current, only one pole of the north and south poles of the neon tube will light up.
(4) Positive and negative grounding defects of different DC systems.
Usually, the DC system of the power station and substation is insulated from the ground. If the neon tube is bright, it means that the system has a grounding phenomenon (the grounding phenomenon cannot be detected when the grounding phenomenon is subtle). If the bright spot is close to one end of the pen tip, it indicates that the positive electrode has a grounding defect; if the bright spot is close to one end of the finger, it indicates that the negative electrode has a grounding defect.
The neon tube should have the following conditions at the same time: ① the measured voltage is higher than the ignition voltage of the neon tube, the communication is 50V, and the DC is 90V; ② the current passing through the neon tube must be greater than a certain value, usually greater than 2μA (the voltage must be kept is selected by the resistance value of a 1~3MΩ current limiting resistor inside the test pen).
