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HIGH RESISTANCE NEUTRAL GROUNDING (HGR)

Approximate phase to earth fault current in 240-5000 V networks:

. Solidly grounded systems : 1000-6000 A
. Low resistance grounded systems : 100-1000 A
. High resistance grounded systems : 2-10 A
. Ungrounded (or delta) cable systems : 0,3-2,8 A/km

High Resistance Grounding (HGR) systems are used in power systems where phase to neutral short-circuit current is desired to be limited to zero ampere a few amperes by placing highresistance between neutral point of transformer (or generator) and ground. As it is not possible to locate the fault point in delta connected systems, an artificial neutral point is created and delta connected system can be grounded. This allows a fault current of a few amperes thus locating the fault point becomes easy. When the neutral point is grounded thru high resistance, both continuity of operation is provided during fault condition and sufficient current (between 2A and 10A) flow is provided for ease of locating the fault point.

While locating the ground contact point of phase - neutral fault current that is limited to approximately 2A, generating approximately 10A pulses (approx. 1 second on, 1 second off) provides ease of measurement thus using short time pulses is the common application in HRG systems today.

Generally measurement is performed by analogue and wide clamp ammeters. The clamp ammeter outside the phase cable is traced until the pulse current disappears on the analogue display.

High Resistance Grounding Sstems are economical and practical
choice especially systems under 5000 Volts.

As zero sequence (3Io) currents flow thru neutral point due to line
capacitance of cables, HGR alarm level is set to a point that is
greater than 3Io .

Hilkar HIGH RESISTANCE GROUNDING DEVICE :

  • 0 - 10A analog ammeter and 0 - 250V analog voltmeter with setting on panel
  • Automatic door switch for power shut down.
  • TEST BUTTON to indicate fault.
  • GREEN LIGHT for normal conditions.
  • INTERMITTENT ALARM and RED LIGHT during ground fault.
  • PULSE/NORMAL Selector swith to magnify current and
    intermittent pulse during ground fault.
  • Auxilliary free contacts at PULSE and ALARM position during fault.
  • Dimensions (LxWxH)= 60 x 100 x 200 cm.
  • Suitable for 240....4160V three phase systems.

HGR