The advantages of fully enclosed appliances are: small footprint, high operational reliability, low maintenance workload, long service intervals, metering switch manufacturers are not affected by external environmental conditions, no electrostatic induction and corona interference, low noise level, good seismic performance and strong adaptability. It is particularly suitable for coastal areas, plateaus and heavily polluted areas.

The daily maintenance of the metering switch manufacturer is mainly to inspect the external equipment in operation, mainly including the following items

(1) Check whether the signal indication is correct. Check whether the various status signals in the control cabinet of each standard interval are consistent with the actual status of the components in the interval, i.e. consistent with the on/off indication of each component. Observe from the front whether the pressure value of the system meets the requirements. It mainly refers to the operating oil pressure (air pressure) of the metering switch and the density value of the sulphur hexafluoride in each gas chamber.

(2) The second international survey of operational experience shows that insulation breakdown in metering switchgear manufacturers still accounts for a large proportion of total failures. It is well known that insulation faults develop gradually with each installation and are often accompanied by the sound of discharge. When the equipment is running, the sound of the power station is generally very small and stable. If there is a strange sound in the cylinder, it is likely to be caused by electrical discharge and should be given high priority so that measures can be taken.

(3) Observe whether the terminals in the control cabinet are overcooked and discoloured.

(4) Check whether the fixing screws of the components are loose in normal operation.

(5) Check whether the grounding switch and grounding components are reliably grounded.

The above items are items that need to be checked frequently during each operation. In addition, each manufacturer gives their own requirements according to the characteristics of their products. It is therefore necessary to read the corresponding installation instructions carefully.

In addition to daily operation and maintenance, regular maintenance is also required. Maintenance means stopping operation and carrying out general checks and repairs externally. This cycle can generally be carried out every 3 ~ 5 years, depending on the operation of the equipment. It mainly includes the following 3360 items

(1) Operating characteristics of the components: measurement of the breaking and closing times of the metering switches, measurement of the operating times of the disconnecting and earthing switches and measurement of the breaking and closing speeds of the fast disconnecting and fast earthing switches. If the switch is not operated for a long time, it should be opened and closed manually once a year, especially the spring-operated mechanism. This is because the various locking devices of the spring-loaded mechanism can rust and even cause malfunctioning of the operation if it is not operated for a long time. So regular operation is very necessary.

(2) Cleaning and lubrication of the electric operating mechanism and the spring-operated mechanism.

(3) Measuring the main circuit resistance and the insulation resistance of some components.

(4) Testing of the water content in each air chamber. There are many sealing links in closed combination appliances. Sealing issues are therefore key to the long-term stable operation of enclosed appliances. In particular, the sealed parts of frequently operated components should be checked regularly. A gas leak detector with a sensitivity of not less than 10.3/ can be used for this purpose. Setting the moisture content of each gas in operation is an important indicator. This is especially true for gas chambers where there are products of arc decomposition, such as those of metering switches. This is because the gas decomposes and ionises under the high temperature of the arc and the -' part of it forms low fluoride. When water is present in the gas, very toxic and corrosive substances are produced. Most of these products are absorbed by the adsorbent installed inside the metering switch, but some of them stick to the insulator surface. These adherents can cause severe corrosion to the insulators and significantly reduce their surface resistance. There are significant potential risks to the safe operation of the equipment. Regular measurement of moisture content therefore not only eliminates hidden problems, but also enables early detection of gas leaks. This is because an increase in moisture content is often due to leaks in the equipment. Furthermore, in addition to the above-mentioned maintenance and regular maintenance, there are also problems with ad hoc maintenance during operation. When abnormalities are detected, when certain components have reached a specified number of uses (e.g. the number of times the load current or short-circuit current is switched on and off