小电容试品表面泄漏对测量tgδ的影响分析

An Analysis on Influence of Surface Leakage of Small capacitance Sample on tg δ Measurement

分析了小电容试品用加装屏蔽环的方法来消除瓷裙表面潮湿、脏污等表面泄漏对ｔｇδ测试的影响，在小电容试品瓷套表面加屏蔽环时，由于改变了内部电场分布，ｔｇδ的测试结果误差很大，正接法时结果偏小，倒接法时结果偏大，因此在相对湿度小于８０％时才能测准，湿度过大时应采取表面涂防污涂料等措施。

Methods for small capacitance sample appending with shielding ring to eliminate the influenece on measuring tg δ caused by moisture and dust on the surface of insulator skirt are analysed. With a shielding ring added on the porcelain bushing of the small capacitance sample, the test error of the tg δ will be quite significant. The result will be too low using positve connection method and too high using reverse connection method. The sample surface should be painted with an anti pollution coating when the humidity is over 80%.