Metal oxide arrester installation error analysis - Power Circuit - Circuit Diagram

With the general development of urban and rural power grid reconstruction, metal oxide surge arresters (hereinafter referred to as MOA) have been widely used in 10 ~ 500kV power grids. MOA has low residual voltage, no freewheeling, simple structure, small size, light weight, installation and operation. Many advantages such as easy maintenance. However, during our contact with some users, some units were found to have improper installation when using MOA, which made MOA not protect it properly, and even prone to accidents, threatening the safe operation of the grid. The correct installation method is illustrated below.

1 pillar type base installation method is wrong

In the installation method shown in Figure 1, there is no insulating pad above the connecting plate on the base. The running current flowing through the MOA is directly grounded without the counter or the online monitor, so that the counter or the online monitor can not record the MOA action times or monitor the MOA. The role of running current.

The installation method shown in Figure 2 adds an insulating pad above the connecting plate on the base. The running current flowing through the MOA is grounded by a counter or an online monitor, which can accurately record the MOA action times or monitor the MOA operating current. The correct installation method.

2 Counter or online monitor installation error comparison

In the installation method shown in Figures 3 and 4, the high and low voltage terminals of the counter or the online monitor are connected at the same potential of the MOA, and no current flows through the counter or the online monitor, so that they do not function properly. And the MOA is not grounded, and it does not protect the power system. The installation method shown in Figure 5 is the correct installation method.

3 MOA high voltage wiring method is wrong

Due to the different degrees of emphasis, the safety distance is considered in the MOA wiring of voltage levels above 110kV, while the MOA of the voltage level of 35kV and below pays insufficient attention to the safety distance problem, especially the MOA installed indoors. Distance problem. As shown in Figure 6, the wiring method is not enough (the power line is connected), which is very harmful:

1 It is easy to cause damage to the human body or nearby equipment. 2 The high voltage lead is easy to discharge the flange of the MOA, causing a ground fault or overvoltage.

Figure 7 shows the correct installation method (up to the power line) to ensure a sufficient safety distance.

The above is a description of the more common MOA error installation methods. The main purpose is to remind the user to use the manual in the actual application. Please read the instruction manual provided by the manufacturer in detail to avoid accidents or other failures that should not occur due to improper installation. For MOA, in addition to the correct installation method, the unit must be inspected and maintained during operation. The MOA prophylactic test is conducted before the annual thunderstorm season to check whether the components of the MOA are good and the parameters meet the requirements. Also install the counter or online monitor to check if it is working properly.

As long as the user has correctly mastered the MOA installation method and operation and maintenance method, MOA can exert excellent protection and contribute to the safe and stable operation of the power system.

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