Substation Air Switch :
Substation air switches are mechanical switching device that are used for changing the
connections in a circuit. The switches are required to carry normal load current
continuously and short-circuit current for short period of time. Substation air switches
are used for circuit breaker isolation, power transformer isolation, electrical equipment
bypassing, and bus sectionalizing. Figure 3-5, 3-6, 3-7, and 3-8 shows different type of
outdoor air switches.
Figure 3-5: Hook Stick-Operated Disconnecting Switch
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Figure 3-6: Three-Phase Gang-Operated Disconnecting Switch with Horn Gaps and
Grounding Switch
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Figure 3-7: Three-Phase Double Side-Break Disconnecting Switch with Motor Operator
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Dewan Jamir EMGT 835, Spring 2006
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CPM Scheduling, Basic Engineering, and Project Approach for Typical Substation EPC
Project
Figure 3-8: Fused Disconnect
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The operating mechanisms are bonded directly to the operator mat/platform with a 4/0
copper ground conductor to ensure that the operating personnel’s hands and feet will be
maintained at the same potential. Figure 5-22 and 5-23 shows horizontally mounted
double break switch with grounding and horizontally mounted double break switch.
Figure 5-22: Horizontally Mounted Figure 5-23: Horizontally Mounted Double
Double Break Switch with Break Switch
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Grounding Switch
1
Table 4-8 lists the phase spacing of various types of outdoor air switches. The
minimum metal-to-metal clearances should be maintained at all times with the switches
Dewan Jamir EMGT 835, Spring 2006
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CPM Scheduling, Basic Engineering, and Project Approach for Typical Substation EPC
Project
in the open, closed, or anywhere between the open and closed positions.
Table 4-8: Phase Spacing of Outdoor Air Switches
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1. United States Department of Agriculture, “Design Guide for Rural Substations”,
pages 61-62, 155 & 300, 2001.
Dewan Jamir EMGT 835, Spring 2006
