Substation maintenance is a process of periodic, planned inspection of and, if necessary, repair, and replacement of all switchgear, buildings, and ancillary equipment in substation installations. In simple terms, substation maintenance is a regimen of regular preventative checks and actions carried out to ensure substations are kept in good working order. This process typically consists of a series of stringent visual and physical inspections and actions carried out according to a set schedule. All inspection and actions during substation maintenance should be accurately documented and stored for further reference. Substations are the most critical part of any electrical supply grid. Substation care is one of the most important parts of any electrical department's preventative maintenance schedule. These schedules generally consist of a tiered plan of minor and major maintenance events. Minor maintenance will seldom require any sort of power shut down although major events typically requiring short intervals of supply interruption. Routine or minor substation maintenance is usually carried out on a weekly or bi-weekly basis. It typically consists of visual checks and superficial cleaning only. Major substation maintenance involves more planning and is generally handled on a quarterly basis. In the case of industrial installations, these procedures are often carried out during plant maintenance shutdowns. Ancillary equipment such as amp and volt meters, control circuits, and transformers will also be given individual attention during this review.