23 May 2019

Indian Electricity Rules Regarding Linked Switch And Circuit Breaker ( Rule No. 50 )

Rule No 50 : Supply and Use of Energy

  • The controls of proper capacity to carry and break the current are placed after the commencement of supply.
  • A linked switch with fuses or circuit breaker is placed for low and medium voltage consumers.
  • A linked switch with fuses or circuit breaker for HV consumers for transformer capacity up to 1000 kVA supplied at voltage level of 11 kV and 2500 kVA at voltage level above 11 kV but not exceeding 33 kV.
  • A circuit breaker for HV consumers for transformer capacity above 1000 kVA at voltage level 11 kV and 2500 kVA at voltage supplied above 11 kV but less than 33 kV.
  • A circuit breaker is used for EHV consumer.

Rules For Every Transformer
  • A linked switch with fuses or circuit breaker is provided on the primary side of transformer. The capacity of the linked switch must be carry full load current and to break only the magnetizing current of the transformer.
  • A circuit breaker is provided if the transformer capacity 5000 kVA and above.
  • The provision of the linked switch on the primary side of the transformer shall not apply to the unit auxiliary transformer of the generator.
  • If the transformer capacity 100 kVA and above which transform HV to MV / LV, a linked switch with fuses or circuit breaker is provided. The circuit breaker is capable to carrying and breaking the full load current.
  • If the transformer capacity exceeds 630 kVA and above, a circuit breaker of adequate capacity is provided on the secondary side.
  • The supply of energy to group of motors / each motor/ other apparatus is controlled by suitable linked switch / circuit breaker / emergency tripling device with manual reset of requisite capacity is done by operator.
  • The property of the insulating material should be such that it can withstand against higher ( greater than rated ) temperature and moisture.
  • Precautions shall be taken to ensure that no live parts are exposes to cause danger to anyone.
  • No person interfere service lines and apparatus placed by the supplier on the premises of the consumer.

Rule No : 50A ( Supply and use of energy for multistoried building height more than 15 meters )


  • The supplier / owner of the installation shall provided at the point of commencement of supply , a suitable isolating device with cut out / breaker to operate all the phases except neutral of three phase , four wire system and fixed at 2.75 meters above the ground so as to completely isolate the supply in the case of emergency.
  • The owner of the multistoried building shall ensure the electrical installation in the building is carried out such a manner as to prevent danger due to shock and fire hazard. The electrical installation is carried out by standard code or practices.
  • No other service line shall be taken in the duct provided for laying of power cables. A fire barrier is provided for power cables and other service lines at each floor crossing.

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