number of circuits,
capacity of circuits,
voltage and phase, and
overhead or underground distribution required.
and feeder circuits.
Incoming-Line Switching. Design the substation with a minimum of
incoming-line switching consistent with good maintenance and operation. For
rating of equipment, refer to MIL-HDBK-1004/3, Switchgear and Relaying. Also,
consider the methods described in paras 184.108.40.206 through 220.127.116.11.
interrupting or relaying requirements do not allow the use of switches.
Provide a disconnect and bypass switching features where drawout circuit
breakers cannot be utilized.
18.104.22.168 Switches. Switches are covered in Section 2 of this handbook. For
voltages of 15 kV or less, load interrupter or disconnect switches are
available. Load interrupter switches disconnect circuits under fully loaded
conditions and are therefore usually the most desirable choice. Use
disconnect switches only to interrupt transformer exciting currents. The use
of disconnect switches is not recommended, except for primary incoming lines
do not open disconnect switches under load, either by interlocking with load
switching equipment or by operating procedures.
are covered in Section 2. They are generally inappropriate for substation use
where metal-enclosed or metal-clad switchgear for 15-kV applications provides
a more desirable design.
For ratings and selection of equipment,
refer to MIL-HDBK-1004/3.
22.214.171.124 600 V and Less.
For load circuits below 600 V, select from one of
reliability and the longer withstand rating period are desirable; or
be further defined as to tripping and interrupting currents and whether fully-
rated capability or other features are desirable. The use of the term
"insulated case" conveys no minimum requirements in accordance with any
recognized industry specification and should not be used.