The document discusses the Petersen coil, which is an arc suppression device connected to the neutral of a high or medium voltage network. It was invented in 1917 by Waldemar Petersen and uses resonance grounding to limit fault currents during earth faults. By choking the fault current below the level of self-extinction, transient faults in overhead networks can be cleared without tripping the feeder. When a phase-to-earth fault occurs in an underground three-phase system, the faulty phase voltage is reduced to earth potential and the other two phase voltages rise by the square root of three. This causes a charging current between the phase-to-earth capacitances.

1. Authorized By:
Muhammad Imran Channa
2012-SECR-45

2. The arc Suppression coil invented in 1917 by Waldemar
Petersen , so that’s why it is referred as Petersen coil.
An arc suppression is device that is connected to the
neutral to limit the capacitive earth fault current
flowing when earth fault occurs in a high or medium
voltage network. This method grounding is called
resonance grounding , it has been used in Central
&Eastern Europe as well as Scandinavian countries for
many decades. The Petersen coil chokes fault current
below the level of self extinction for overhead networks.
By this action all transient faults in overhead networks
can be cleared without tripping the feeder. The basic
principle of Petersen coil remained unchanged since
1917 & it is excellent properties have been mirrored by
low outage rates where it has been used.

3. When a phase-to-earth fault occur in underground 3
phase system , the phase voltage of the faulty phase is
reduced to earth potential as capacitance of faulty line
is discharged at the fault location, the phase-to-earth
voltages of other two phases rises by √3.
A charging current “IC” occurs between these phase
to earth capacitances, which will continue to flow via
the fault path while it remains.
IC is three times the charging current of each phase
to earth.

5. Diagrams
 Circuit Diagram  Vector Diagram

6. When a phase to earth fault occur in underground 3
phase systems, the phase voltage of faulty phase is
reduced to ground potential .
This cause the phase voltage in the other two phase to
rise by √3 times.
This increase in voltage causes a charging current, Ic
between the phase-to-earth capacitances.

7. Advantages:
The Petersen coil is completely effective in preventing any
damagebyanarcing ground.
This coil has the advantages of undergrounded neutral
system.
Disadvantages:
Due to varying operational conditions, the capacitances of
the networks changing from time to time. Therefore
inductance “L” of thePetersencoil required readjustment.
Thelineshould betransposed.