Nov 6, 2013

Earth Fault Relay



earth-fault-relay

Types of earth fault relays are the same as over current relays however with just one coil for current within the case of fast, definite time, or inverse time earth fault varieties. One voltage coil is additional within the case of directional earth fault relays.

Instantaneous, Definite Time and Inverse Time Types

Tripping physical characteristics fast Earth Fault, definite time earth fault, or inverse time earth fault relays are the same as the case of over current sort. Totally different associations of current circuits are exist.

  • Current coil is also connected to returning path (neutral) of a current transformer fig shown below.earth-fault-connected-to-neutral-point-CT
  • Current coil is also connected to the secondary of current transformer that is put in at the stare purpose of power transformer as shown in figure below.
earth-fault-connected-in star-point-transformer
  • Current coil is also connected to secondary of ring sort current transformer put in at power cables as shown in figure below.
earth-fault-relay-connected-to-ring-type-CT
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