Treatment after secondary open circuit:(1) Try to short-circuit the current transformer for the second time on the nearest test terminal, and then check and deal with the open circuit point. During the short-circuit, the special short-circuit wiring for short-circuit shall be used. The short-circuit shall be proper and reliable. It is forbidden to use fuse or general conductor winding, and it shall be carried out according to the drawing.(2) Pay attention to the phenomenon of short-circuit. If there is spark during short-circuit, the short-circuit is effective. The fault point is in the circuit below the short-circuit contact, which can be further found. If there is no spark during short-circuit, the short-circuit may be invalid. The fault point may be in the circuit before the short contact. The short contact can be changed forward point by point to narrow the range.

(3) When shorting the secondary circuit, the staff must adhere to the operation monitoring system, one person operates and one person monitors. Keep an appropriate safe distance from live equipment. Operators must wear insulating boots, insulating gloves and tools with insulating handles. It is forbidden to carry out any work on the circuit between the current transformer and the short-circuit point.

(4) Within the fault range, check the terminals and components prone to failure, and check the parts of the circuit that have been touched during operation. For the faults detected, those that can be handled by themselves can be handled immediately, and then the exited protection can be put into operation. If the open circuit point is on the wiring terminal of the transformer body, the power shall be cut off for treatment. In case of failure that cannot be handled or found out by yourself, report to the superior and send someone to check and deal with it. At this time, the current transformer shall be short circuited for the second time, or the load shall be transferred and the power shall be cut off.

(5) If the secondary open circuit of current transformer is found, it is necessary to distinguish which group of current circuit the fault belongs to, the phase of the open circuit and whether it has an impact on the protection, report to the dispatcher and remove the possible misoperation protection.Cause of secondary open circuit:(1) When the secondary line terminal connector is not crimped tightly and the current in the circuit is large, it will be heated, burned out or oxidized, resulting in an open circuit.

(2) The outdoor terminal box and junction box are damp, and the terminal bolts and gaskets are excessively rusted, resulting in an open circuit.(3) Due to the defects in structure and quality, the test wiring terminal in AC current circuit has poor contact between screw and copper plate screw hole during operation, resulting in open circuit.(4) For the test terminal pressing plate in the current circuit, because the glue wood is too long, the metal sheet of the rotating terminal is not pressed on the metal sheet of the pressing plate, but is wrongly pressed on the glue Wood sleeve, resulting in an open circuit.

(5) Errors made by the maintenance and test personnel in their work, such as forgetting to connect the internal connector of the relay, could not be found during acceptance.

The current situation of power transformer MMS anti-theft alarm system and the supply of power, especially the safe and reliable supply of power, have always been the focus of society, enterprises, people and the media. Because a safe, stable and reliable power supply is related to the development of the national economy, the construction of a harmonious society and the vital interests of the people. Power grid security has become a sharp sword hanging over power enterprises.Overview

According to statistics, in the first two quarters of 2005, there were more than 550 cases of theft and destruction of power facilities in the system of Sichuan electric power company, with a direct economic loss of more than 2.6 million yuan. According to conservative estimates, in recent years, the direct economic losses caused by the theft of power facilities alone have exceeded 200 million yuan. Power grid security has become a sharp sword hanging over power enterprises. The supply of electricity, especially the safe and reliable supply of electricity, has always been the focus of attention of society, enterprises, people and the media. Because a safe, stable and reliable power supply is related to the development of the national economy, the construction of a harmonious society and the vital interests of the people.

According to the survey, the current maintenance, management and anti-theft of power facilities are summarized as follows:1. Most transformers and other power facilities are located outdoors and scattered in streets, urban-rural fringe, rural areas and other places, which brings a lot of trouble to the safety management of transformers.2. It is impossible for the power department to assign a large number of manpower to monitor each transformer in real time in an artificial way to prevent the equipment from being stolen or damaged.

3. In China, some provinces have also used methods such as infrared, limited distance wireless communication and physical anti-theft card to solve the anti-theft problem of transformer. However, due to the limitations of the principle of these systems or products, false alarm, weak anti-interference ability, and unable to receive the alarm signal in time, resulting in a large waste of human, material and financial resources. At the same time, the wireless transmission mode has high power (energy consumption) and needs to be approved by the management committee, which also has certain restrictions on the promotion of the system and products.

To sum up, the theft of power lines and transformers is relatively serious, and the relevant state departments attach great importance to it. Civil air defense plus technical defense is the most effective method. According to the actual situation, our company has developed a power transformer MMS anti-theft alarm system. This system is mainly used for power transformer anti-theft alarm. Its characteristics are: not limited by distance, quantity and climate. It has the characteristics of practical function, excellent quality and stable and reliable operation. It is suitable for various outdoor environments. It is widely used in the safety protection of all outdoor working equipment such as electric power, petroleum, base station and mine. It is the most advanced MMS alarm system among similar products in China.

The current sampling unit is a sampling circuit that provides the current sampling signal to the single chip microcomputer when the induction cooker works. The single chip microcomputer always detects the change of the input current, and automatically adjusts the PWM signal according to the detected current sampling signal to make the induction cooker do the constant processing of the output power. The single chip microcomputer will also detect the input current of the induction cooker according to the change of the detected current sampling signal, so as to automatically make various actions. When the single chip microcomputer detects the appropriate pulse number of the pot in the synchronous circuit, it will use 0.5 2S to detect the change of the current, and determine whether the material and heating area of the heating pot meet the heating requirements through the difference of the current change. When the current sampling signal changes too much, the single chip microcomputer will judge whether there is no pot. There are two common current sampling unit circuits in the mainstream induction cooker circuits in the market, namely, the current sampling unit using current transformer sampling and the current sampling unit using resistance voltage drop sampling. The working principles of these two sampling circuits will be introduced below.

The current sampling unit is a sampling circuit that provides the current sampling signal to the single chip microcomputer when the induction cooker works. The single chip microcomputer always detects the change of the input current, and automatically adjusts the PWM signal according to the detected current sampling signal to make the induction cooker do the constant processing of the output power. The single chip microcomputer will also detect the input current of the induction cooker according to the change of the detected current sampling signal, so as to automatically make various actions. When the single chip microcomputer detects the appropriate pulse number of the pot in the synchronous circuit, it will use 0.5 2S to detect the change of the current, and determine whether the material and heating area of the heating pot meet the heating requirements through the difference of the current change. When the current sampling signal changes too much, the single chip microcomputer will judge whether there is no pot. There are two common current sampling unit circuits in the mainstream induction cooker circuits in the market, namely, the current sampling unit using current transformer sampling and the current sampling unit using resistance voltage drop sampling. The working principles of these two sampling circuits will be introduced below.

(1) The current sampling unit using current transformer sampling is shown in figure (a) below. The AC voltage secondary measured by current transformer CT1 is rectified by bridge rectifier composed of d10 D13. The DC voltage smoothed by EC5 is sent to the I-A / D port of CPU, and CPU detects the input current of induction cooker according to the change of this voltage signal. The turn ratio of current transformer CT1 is 1:3000. If the turn ratio is large, the induced current is linear when working with high current. VR1 is an adjustable resistance of 0 10K , which is mainly used to adjust the power deviation caused by structural error. It can also change the reference of current detection by adjusting this resistance to achieve the purpose of adjusting the output power of induction cooker. When the VR1 resistance increases, the voltage of the corresponding current detection will increase. When the primary current of CT1 is constant, the voltage induced by the secondary of CT1 will increase accordingly. The program will control accordingly according to the change of analog signal of a / D port. According to the requirements of software constant power, the power will decrease relatively.

Transfer files for [membrane switch] proofing