Abstract
Recently, electrodeless methods of measuring the resistance of grounding devices have appeared, with the help of special clamps. But a large methodological error limits the possibility of their use, especially when rationing low resistances. The article shows the possibility to improve the accuracy of electrodeless measurement methods using commercially available measuring instruments.In electrical installations of telecommunication networks of buildings, structures and industrial enterprises, the form of the AC voltage signal of the industrial supply network (~220V, 50/60Hz) can be differ greatly from the sinusoidal for short periods of time. The causes of distortions are usually associated with a sudden change in the network load [1], for example, when you turn on a powerful electric motor, furnace, welding machine, etc.The occurrence of impulse overvoltages and interference caused by electromagnetic effects (lightning, switching, radio frequency and others) on low-voltage networks, not only leads to failure of electrical installations, cables, switchboards, but also to damage the terminal equipment and malfunction. This is due, primarily, to the saturation of modern buildings and structures with information, telecommunications and other digital equipment, which has a very low level of protection against impulse overvoltages and interference. All this makes it necessary to carry out appropriate protective measures. To reduce interference, it is necessary to perform a separate (working) ground loop, the resistance of which must be measured and periodically monitored.There are devices that allow an electrodeless method to monitor and evaluate the resistance of the ground loop. But these devices have a greater measurement error than devices that measure the resistance of the earth electrode method.The article deals with existing instruments (CA6410, MZC-303E) which can evaluate the resistance of the earth electrode and the possibility of increasing the accuracy of the measurement with the help of special current clamps is shown. Using a predetermined value of neutral impedance, the measurement error of the calculated resistance of the earthing switch can be determined with great accuracy.
Highlights
For these purposes, the world market offers a large selection of devices that guarantee the necessary accuracy of measurements, provided that the user meets certain operating conditions. 2.1
Instruments for measuring the resistance of the grounding device, in addition to the performance of the climatic conditions of operation, require the specific placement of current and. In such cases, reckoning methods are used to determine the resistance of the GD, given the known geometric dimensions of the potential electrodes relative to ground contour under investigation and the known resistivity of the ground
The device is recommended for measurements in electrical installations, networks of buildings, structures and industrial enterprises in which the error caused by neglect of reactive resistance can be of significant significance
Summary
The world market offers a large selection of devices that guarantee the necessary accuracy of measurements, provided that the user meets certain operating conditions. 2.1. Calculate the total earth resistance of the neutral and introduce it as an amendment to the result of the measurement of the ground loop being examined To implement such an option, it is proposed to measure directly on the substation the resistance of the closed electrical circuit formed between the internal ground of the substation transformer and all external earthing switches. The calculated value of the total resistance of the neutral for each transformer should be known and periodically fixed in the transformer's passport This is explained by the figure (Fig.3) where it is indicated: For example, by including a new consumer / equipment in the system that requires grounding of the neutral and observing the small values of the earthing resistance (Fig. 5), knowing the value of the neutral resistance Zr and measuring the resistance using the current clamp-Zx, it is possible to determine the resistance of the equipment ZG with high accuracy. - resistance of the zero wire, which can be determined from geometric data
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