Protection System Study

There may be several instances where certain un-identified faults may occur per se, and it may not only destroy the equipment of its origin but also may spread in the system and cause total failure ultimately preventing it from operating at all. Our team of experts at Samarth Safety will help you to prevent and observe the following:

  • A great reduction of the line voltages.
  • Damage caused to the root element of the system.
  • Damage to other parts due to overheating.
  • Disturbance to the stability of the system and this may even lead to a complete shutdown of the power system.
  • Reduction in the voltage may fail the pressure coil of the relay.
  • Considerable reduction in the voltage on healthy feeder connected to the system having fault. This may cause either an abnormally high current being drawn by the motor or the operation of no-volt coils of the motors. (Considerable loss of industrial production as the motors will have to be restarted)

We at Samarth Safety will assure you with every piece of advice on the protective system which isolates a faulty element. To fulfill it, we’ll satisfy the four primary requirements of our client:


Reliability is a qualitative term. It can be expressed as a probability of failure.

  • Quality of personnel i.e. mistakes by personnel are most likely causes of failure
  • High contact pressure
  • Dust free enclosures

Our experts will update you with the records to show that the order of likelihood of failure is relays, breakers, wiring, current transformers, voltage transformers and battery.


The property by which only the faulty element of the system is isolated and the remaining healthy sections are left intact. Selectivity is absolute if the protection responds only to faults within its own zone and relative if it is obtained by grading the setting of protections of several zones which may Power System Protection respond to a given fault. The systems of protection which in principle are absolutely selective are known as unit systems. The systems in which selectivity is relative are non-unit system.

Fastness of Operation

Protective relays are required to be quick-acting due to the following reasons:

  • Critical clearing time should not be exceeded.
  • Electrical apparatus may be damaged, if they are made to carry fault currents for a long time.
  • A persistent fault will lower the voltage resulting in crawling and overloading of industrial drives.


  • Protection must be sufficiently sensitive to operate reliably under minimum fault condition for a fault within its own zone while remaining stable under maximum load i.e. a relay should be able to distinguish between a fault and an overload.
  • In the case of transformers, the inrush of magnetizing current may be comparable to the full current, being 5 to 7 times the full load current. The relay should not operate for inrush current.
  • In interconnected systems, there will be power swing, which should also be ignored by the relay.