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We all know that the electroscope is a basic safety tool commonly used in substations, often used in distribution rooms, construction sites, live working areas, etc. Of course, it can also be used to identify the positive or negative charge of a charged body. For example, first touch the electroscope with a positively charged body to make the gold leaves positively charged and open at a certain angle. Then, bring the charged body to be identified near the disc. If the charged body is positively charged, the opening angle increases; otherwise, it decreases.
The upper part of the electroscope is a metal plate or metal ball, which is connected to a metal rod. The metal rod passes through a rubber stopper, and its lower end hangs two extremely thin metal leaves, sealed inside a glass bottle. During testing, touch the object to the metal plate. If the object is charged, part of the charge transfers to the two gold leaves. Since the metal leaves carry the same type of charge, they repel each other and open. The more charge they carry, the larger the opening angle. If the object is uncharged, the metal leaves remain still. When it is known that an object is charged, to identify the type of charge it carries, first touch the charged body to the metal ball to make the gold leaves open. Then, touch the metal ball of the electroscope with a known object carrying sufficient positive charge. If the opening angle of the metal leaves increases, it indicates that the charged body has a positive charge; conversely, if the opening angle decreases, or first closes and then opens, it indicates that the charged body has a negative charge.
How should the electroscope be used correctly?
1. Before using the electroscope, you must wear high-voltage insulating gloves and insulating shoes, and be supervised by a dedicated person.
2. The electroscope put into use must be one that has passed electrical tests. High-voltage electroscopes must be tested regularly to ensure their good performance. It should also be tested on live equipment of the corresponding voltage level to verify correct alarm before being used to test for voltage on equipment that needs grounding. It is forbidden to use an electroscope with a mismatched voltage level for testing, to avoid incorrect judgments during on-site testing.
3. Testing for voltage on lines should be carried out phase by phase. When testing circuit breakers, disconnectors, or other equipment under maintenance for voltage, test each phase on both the incoming and outgoing sides.
4. When testing for voltage on multi-layer power lines erected on the same tower, test the low voltage first, then the high voltage; test the lower layer first, then the upper layer.
5. When testing for voltage on capacitor banks, wait until they are fully discharged before proceeding.
6. During voltage testing, gradually bring the metal working contact at the top of the electroscope close to the live part until the neon bulb glows or an audible alarm sounds. Do not directly touch the live parts of electrical equipment. The electroscope should not be affected by nearby live bodies, which could cause false signals.
7. If a ladder is needed during voltage testing, use a sturdy ladder made of insulating material and take necessary anti-slip measures. It is forbidden to use metal ladders.
8. After completing the voltage test with the electroscope, immediately proceed with grounding. If the grounding is interrupted and not carried out in time after the test, and continued operation is needed, the voltage test must be repeated.
