PERMIT IN ELECTRIC SYSTEM

WHAT IS THE MEANING OF PERMIT ON ELECTRIC EQUIPMENT AND LINES?

PERMIT: Permit in electric system means permission taken for a fix time by authorize person from controlling authority to work on electric equipment and feeders.

OR

Permit on electric system means electric equipment and feeder are in off ( no current flow) position for a fix time and now the feeder and equipment is in safe position to work on it.

WHY AN ELECTRICAL PERMIT IS REQUIRED?

The requirements of permit on electric lines and equipment is given below:

• At the time of attending breakdown of lines (feeders) at the time of fault.
• Schedule maintenance of electric equipment and lines.
• At the time of tree trimming of lines.
• At the time of attending breakdown of feeder, if another feeder cross the faulty feeder or if both the lines (feeder) on same pole.Then permit is also issue on normal feeder, this permit issue on normal feeder for safety purpose.
• At the time of preventive maintenance of equipment and lines.
• For clearing fault of electrical equipment (substation power transformer, circuit breaker etc).
• Some time for new connection of consumers.
• Erection of new feeder (safety purpose).

PROCESS OF ISSUING PERMIT: Mainly permit issues by substation staff (substation operator, substation attendant) to field staff.Substation staff issue permit to authorize person of field staff.

Firstly field staff writes the reason of permit on feeder in massage book and also writes the approximate time of completion of work.After this substation staff and field staff fill a permit that follow permit issue process.After filling the permit book, substation staff issue a permit page to the field staff or issue a Permit To Work (PTW) code (permit page number).The given below image shows the permit format.

Permit Page

Following work should be done after issuing written permit:

• Check the feeder/line circuit breaker panel on which permit issue.
• Wear the safety dress (helmet, gloves, safety shoes etc).
• Trip the circuit with the help of TNC (TRIP - NEUTRAL - CLOSE) switch or mechanically by trip push button in circuit breaker trolley.
• Check the electrical and mechanical indication that shows the breaker in OFF condition.
• Check the load current in all three phases (R - Y - B) of ammeter.
• After this Rack out the trolley of circuit breaker and check the circuit breaker position indicator.The circuit breaker position indicator shows the three position of circuit breaker that is given below.

1. Breaker is in ON position - SERVICE
2. Breaker is in OFF position - SERVICE/INTERMEDIATE
3. Trolley is in RACK OUT position - TEST

• Open the main isolator/G.O. (Gang operated ) switch  of the feeder.It is mainly situated at the first H pole of the feeder near the substation.
• Put the PTW tag on the circuit breaker panel on which permit is issue.

After doing above work, substation operator give fully permit to field staff for the work on line or electrical equipment.

After completing the work by field staff.The following processes should be follow by substation staff and field staff before operating the circuit breaker of the permit issuing feeder.

• Fill the permit book that follow cancellation process.
• Remove the PTW tag from the circuit breaker panel.
• Close the main isolator/G.O. switch.
• RACK IN trolley of circuit breaker and check the circuit breaker position indicator.It shows SERVICE/INTERMEDIATE position.
• Check the D.C. supply (trip circuit healthy) of the circuit breaker.

Before close the circuit breaker once again confirm by field staff, line is clear for operation.

OR

All the staff is away from feeder/line.

• After confirmation by field staff close the circuit breaker by the TNC switch or mechanically by close push button in circuit breaker trolley.
• Check the electrical and mechanical indication that shows the breaker in ON condition.
• Once again check the D.C. supply (trip circuit healthy) of the circuit breaker.
• Check the load current in all three phases (R - Y - B) of ammeter.

The above process should be follow by the substation staff at the time of issuing permit.

PRECAUTIONS AT THE TIME OF PERMIT:

The given below things should not be done at the time of permit:

• Permit should not be issue on mobile phone.
• After issuing permit check the right feeder on which permit is issue.
• Permit should not be cancelled on phone.
• At the time of operation of circuit breaker should not be do any other work (attending phone calls etc).
• Do not take quick action at the time of ON/OFF operation of circuit breaker.

Conclusion: The final conclusion is that permit on line/equipment is very necessary at the time of work.Because after the permit on line/equipment, it is safe to work.So, it is necessary to follow all the above given process at the time of issue permit .Because a small mistake can be cause of a big accident or even a cause of death.