Switchgear assemblies insulation

No derating is applicable in case of insulated switchgear (GI.S) assemblies. 

Insulation levels, power frequency and impulse withstand voltages for metal-enclosed switchgear assemblies... 

Wet test While an indoor type switchgear assembly requires only a dry power frequency voltage withstand test, the outdoor type switchgear assembly also needs a wet test under wet conditions to check the external insulation. For the test procedure refer to lEC 60060-1. 

Table 14.6 Temperature limits for insulating materials as used in a switchgear assembly...

Testing of metal-enclosed switchgear assemblies 14/435 Insulation resistance method... 

The procedure will be the same as that discussed for switchgear assemblies (Section 14.3.3). The test voltage may be applied for one minute as shown in Tables 32.1 (A) or (B) for series I and Table 32.2 for series II voltage systems. Any disruptive discharge or insulation breakdown during the application of high voltage will be considered to be dielectric failure. 

Switchgear and controlgear assemblies 13/345 Table 13.3 Standard insulation (impulse) levels for range II voltage systems (V , > 245 kV)... 

If the insulation resistance is observed to be low the interior of the switchgear or the controlgear assembly should be dried out to attain the required value before energizing it. The procedure to dry the moisture is similar to that for motors and is discussed in Section 9.5.2. In this case during the heating-up period the insulation resistance may first drop and reach its minimum, stabilize at that level and then start to rise gradually. Continue the process until it reaches its required level as shown in Table 14.7. 

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