Safety Concerns with Medium Voltage Switchgear
There are various regulations and rules that need to be followed when operating medium voltage switchgear. The regulations and rules vary from country to country and even from state/city to state/city. We as operators need to follow these regulations and rules in order for us to be safe, legal, and follow the process correctly. In this article we will cover the basics on medium voltage switchgear safety.
The operation of medium voltage switchgear is one of the most dangerous occupations in the electrical industry. There are five types of hazards associated with the operation of medium voltage switchgear:
- Electrical Shock.
- Electrical Burns (for more information please read this article about Arcing Faults In Switchgears)
- Fire and Explosion.
- Heat Build-Up.
- Mechanical Hazards.
Medium voltage switchgear safety precautions sample list:
A. Personal Protective Equipment (PPE):
Always wear protective clothing, including:
• Safety glasses or goggles (not prescription)
• Safety shoes (not gym shoes)
• Long pants and long-sleeved shirt with sleeves over the elbows
B. Minimum Safe Working Distance:
The distance from the operator to any part of the equipment must not exceed 1 m (3 ft). This includes all metalwork and insulators in contact with live parts of the equipment. The distance between operators should be at least 3 m (10 ft). Where there is no possibility of coming into contact with live parts of the equipment, such as when an operator is working on a manual control panel, the minimum safe working distance may be reduced to 1m if there is no possibility of coming into contact with live parts of the equipment.
C. Using Remote Racking Equipment:
A remote racking unit must be used only when it is necessary to work at a point that exceeds 2 m (7 ft) above ground level or when it is necessary to work at heights greater than 2 m (7 ft). Use only approved remote racking units. If more than one remote racking unit is used, ensure that each has been checked for correct operation
D. Using the Maintenance Slow-Closing Device:
The maintenance slow-closing device is used to automatically stop a switchgear circuit when a fault exists. The device is activated by a time delay that causes the switchgear to shut down after a specific period of time.
E. Precautions for Vacuum Metalclad Switchgear:
Vacuum metalclad switchgear must be equipped with a ground bus section, which is connected to high voltage grounds by means of insulating bushings or bus bars installed in the horizontal and vertical sections of the panel, respectively. The bus bar must be connected directly to an earth return point on each outlet panel, but it may also be connected through a neutral bus bar if this is necessary for safe system operation (see Figure 2). The neutral bus bar should not be used as a ground return unless there are no other possible sources of earth return on the panel (for example, if there are no local power systems). If a neutral bus bar must be connected, its length should not exceed 50% of the length of each side of any one outlet panel.
F. Protection from High Voltage:
1.High voltage equipment should be installed where there are no combustible materials and flames are prevented from coming in contact with the equipment. If a high voltage line passes through any part of your building, it must be protected by insulation or a grounding system to prevent arcing currents from entering the building.
2.If you are installing a new or replacement high voltage line or any variable frequency drive, it is important to consider the hazards of arcing at ground level and install suitable protective devices such as fuses or circuit breakers.
3.If you are installing a new transformer, it is important to consult with an electrician before installing any other electrical equipment in your building. The transformer must be installed so that no person may be injured by its falling over or by objects being thrown against it while in operation.
G. Grounding Bus Sections:
1.(a)The bus of an overhead line must be connected to the grounding electrode system (GSE).
(b)The GSE shall not be interrupted by other conductors except
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