A kind of grounding resistance measuring instrument and resistance measuring method of electric power tower

Abstract

The invention discloses a grounding resistance measuring instrument and a resistance measuring method for an electric tower. The grounding resistance measuring instrument comprises a 60 HZ test voltage source, a current sampling circuit, an A / D switching circuit, a microprocessor, a display screen and a storage, wherein the 60 HZ test voltage source is connected with the microprocessor, and usedfor providing 60 HZ test voltage for an electric tower grounding resistance loop under the control of the microprocessor, and feeding back a voltage valve of the testing voltage to the microprocessor;the current sampling circuit is used for collecting current information in the electric tower grounding resistance loop, an output end of the current sampling circuit is connected with the A / D switching circuit, an output end of the A / D switching circuit is connected with the microprocessor, and the microprocessor is also respectively connected with the display screen and the storage. The 60 HZ test voltage source is used to provide the test voltage for the electric tower loop, before calculating the resistance, the microprocessor first shield an interference signal, and thus the whole resistance measuring instrument has the advantages of small errors and high precision.

Description

technical field [0001] The invention relates to lightning protection of power transmission lines, in particular to a power tower grounding resistance measuring instrument and a resistance measuring method. Background technique [0002] Grounding protection of overhead power line towers is one of the main means to protect transmission line equipment from lightning damage. At present, power construction units mainly evaluate whether the grounding protection system is reliable and effective by measuring the grounding resistance of the tower The accurate measurement of resistance is of great significance to the safety of power transmission equipment. [0003] The main methods of testing the grounding resistance of the tower include: 1. Three-level method: This method is also called the current and voltage pole method. Using grounding shaker, electrode lead, grounding probe and other equipment, the value of the grounding resistance of the grounding device is equal to the ratio o...

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Problems solved by technology

[0003] The main methods of tower grounding resistance detection include: 1. Three-stage method: This method is also called the current voltage pole method. Use grounding meter, electrode lead wire, ground electrode probe and other equipment. The value of the grounding resistance of the grounding device is equal to the ratio of the grounding voltage of the grounding device to the power frequency current flowing into the ground through the grounding device; this test method needs to be tested on site. Arranging tens of meters of electrode leads, the labor intensity of the test work is relatively high, and at the same time, due to the difference in the actual setting distance and angle, the interference to the measurement data and the calculation error are caused, resulting in a large error in the measurement result; 2. Clamp meter method: This method uses the principle of electromagnetic induction to send a constant voltage to the cable under test through the ring formed by the front bayonet of the clamp meter (with an electromagnetic coil inside), and the voltage is applied to the multi-point grounding circuit of the tower. At the same time, the current in the loop can be measured through the front bayonet, and the total resistance in the loop can be calculated according to Ohm's law. The main problem with this method is that the test frequency used by the clamp meter is too high, generally above 100Hz. Some even reach 1kHz. The impedance measured at such a high frequency is obviously far from the impedance of the transmission line at 50Hz. Another disadvantage of the clamp meter is that the measurement accuracy is poor. Generally, it can only be resolved to 0.1Ω. This is due to its The test current is too small to

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