MV Systems

Medium voltage panel board


A medium voltage panel board comprises of Air and Gas insulated switchboard having capacity from 3.3 KV to 36 KV. These switchgears are of many types. They may metal enclosed indoor type, metal enclosed outdoor type, outdoor type without metal enclosure, etc. The interruption medium of this switchgear may be oil, SF6 and vacuum. The main requirement of MV power network is to interrupt current during faulty condition irrespective of what type of CB is used in the MV switchgear system.

This switchgear consisits of


  • Low voltage compartment
  • Circuit breaker compartment
  • Bus bar compartment
  • Cable and CT compartment

Medium voltage circuit breakers which operate in the range of 600 to 15,000 volts should be inspected and maintained annually as said below The main factors for these inspections are


  • temperature
  • mechanical vibration
  • relative humidity
  • salt environment
  • accumulation of dust
  • corrosive atmospheres
  • available load & current harmonics

S.no Description
1 Checking & cleaning of Insulators, Partitions, shrouds & Panel interior
2 Cleaning & Lubrication of drive mechanism as per manual
3 Cleaning & Lubrication of wheel as well as moving parts of breaker truck & Interlocking plate.
4 Cleaning & Lubrication of shutter mechanism, Door hinges and locks
5 Checking the Door, Bkr Truck & Earth Sw./Earthing truck interlocks functional
6 Checking and if required adjust allignment for smooth movement of CB truck
7 Checking Tightness of busbar & cable connection by Torque Wrench (For pnls)
8 Checking Tightness of Bolts in Drive Mechanism & Pole assy by Torque Wrench
9 Checking electrical operation of Tripping and Closing Coils.
10 Checking Tightness of control wiring at Terminals.
11 Checking position of coding pins of control plug, if applicable
12 Checking Mechanical operation of breaker by manual spring charging
13 Checking Draw-out male-female isolating power contact and if required clean & apply grease.
14 Checking healthiness of vaccum & Contact Erosion.
15 Checking healthiness of space heater & Thermostat.
16 Checking status of control fuses.
17 Checking of Earthing connection.
18 Breaker operation counter reading.
19 IR Values of Bkr(isolated)using 5KV megger. - in ON Pos. R-E/Y-E/B-E/R-Y/Y-B/B-R - in OFF Pos. R-R/Y-Y/B-B
20 Visual check of Gaskets.
21 Checking LT chamber illumination lamp
22 General Checking of breaker & panel for any abnormal condition
23 Millivolt Drop Test across Switching Contacts & at draw out contacts
24 Breaker closing & opening timing checks