EFI(Earth Fault Indicator)

1. Concept of the product

In an HV electrical distribution network, when an earth fault occurs, a section of the distribution network trips due to the fault. It is a time consuming process to detect the location of the fault. Deploying an Earth Fault Indicator at strategic locations in the network, reduces the fault detection time considerably.

On-line make Earth Fault Indicator Model: MCEF-03 detects the passage of earth fault current at a point on an under ground HV cable / Overhead HV distribution network.The fault current is sensed using a specially designed
current sensor working on a core balanced principle, and when the current exceed the set point, an electromechanical flag is set to indicate the fault. The fault flag will remain in the set condition even when the mains power is interrupted, and is automatically reset when the power resumes and the fault cleared.

2. Features of MCEF-03

  • There is an electro mechanical flag provided to display the Fault/Healthy conditions. Red Colour indicates the Fault, and White Colour indicates a Healthy state. The Indicator surfaces are made from a reflective material to be visible even in darkness by shining a torch on it.
  • A Test button is provided on the unit to periodically check the healthiness of the unit.
  • Two separate potential free changeover contacts are provided as an out put to connect the unit to any outside system like SCADA.
  • The unit requires an auxiliary supply of 230 VAC (+/- 15 %) (Other voltages available as per users needs). The units Fault flag will remain set even when there is an interruption of the mains supply. The unit will reset automatically when the fault is cleared and the power is resumed back.

3. Specifications:

Earth Fault Indicator

Auxiliary Supply: 230 Volts AC (+/- 15%)
Power On Indication Green LED provided on front for Power On Indication
Fault Current: 40 Amps.
Dimensions: 96 mm(W) X 96 mm(H) X 120 mm(D)
(Cutout 92 mm X 92 mm)
Weight: 1.0 Kg. (approx)
OptionalHousing : The unit is a front panel mounting type with a standard 96mm X 96mm front panel. An optional weather resistant metal enclosure duly powder coated is available to house the unit. It is suitable for both
Output Contacts Indoor and Outdoor applications.
Two potential free change over output contacts are provided and marked as A and B. The contacts are rated at 2 amps @ 240 VAC.

Split Core Current Sesnsor :

Sensing: Core Balanced Principal
Application : To be used with MCEF-03 EFI as a sensor of fault Current.
Mounting: Being a split-core design, it can be mounted easily on existing cable without removing the termination of the cable.
Dimensions: OD : 155 mm . ID : 110 mm. Height : 35 mm
Weight : 1.0 Kg. (approx)

4. Front Display Panel:

The diagram shows the front display panel of the unit.

  • The top window is the Fault Flag Display Window. Under the normal condition the electro mechanical Fault Flag will display WHITE colour, indicating a Healthy status. When an earth fault occurs, the flag mechanism triggers and the Fault Flag turns RED. Even when the auxiliary supply gets disconnected, the flag will remain in the RED condition. This will enable the operator to quickly find the faulty section.
  • When the fault is rectified and power is resumed back, The Fault Flag will automatically reset to its normal WHITE condition.
  • A TEST button is provided to check the healthiness of the operation of the unit. When the TEST button is pressed, a simulated fault signal is generated at the units input, which will trigger the Fault Flag. The flag will reset within 3 seconds and the counter will not increment when the fault is created with TEST button.

Back Panel:

Connect Auxiliary Supply (Phase and Neutral) between terminals 1 and 2.

Connect the wires from the fault sensing Current Sensor to terminals 3 & 4.

Terminals marked A (5,6 & 7) and B (8,9 & 10) are potential free output contacts. It can be used to connect to any external control or display device such as SCADA or external alarms

5. Mounting and Installations:

  • The unit can be mounted at any convenient locations such as walls or on a mounting plate, which can be fitted conveniently on the 11 KV switchgear.
  • The CURRENT SENSOR can be mounted inside the cable box. On an existing installation, the Split Core Current sensor will open out in two sections when you loosen and open the jubilee clip screw. The two section of Current Sensor is reassembled, keeping the power cable in the center and the Jubilee clip is fitted back. This will eliminate the need of decompounding and/or detaching the main cable from its termination. The bolts should be properly tightened to ensure reliable operation of the unit.
  • It must be ensured that the earth fault current path remains OUTSIDE of the Current Sensor. It is preferable to put Current Sensor on the unsheathed portion of the cable. If however the Current Sensor is mounted on the sheathed portion, then the earthing should be looped back from within the Current Sensor and connected to an outside path.

  • The unit can be housed in an optional outdoor duty metal enclosure, or it can be mounted on the panel on any standard 96mm X 96mm (cutout 92mm X 92 mm) slot. On the outdoor metal housing, cable glands are provided for wiring at the bottom. The wiring should be kept in a conduit pipe to avoid nuisance from pests. The front door must be closed properly to avoid dust and rain water entering the unit.
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