Fault indicator

Type NG

The earth-fault and short-circuit indicator can be used in radial networks with one input and open-ring networks. For earth-fault detection, the network has to be solidly earthed or low-resistance earthed.
The indication of the short-circuit is done by one LED indicator for each phase and one LED for earth-fault indication. The short-circuit indicator type NG-K and NG-EK can also be used in closed-ring networks. If there is a short-circuit in a closed-ring network, all NG indicators in the ring will indicate the passage of a fault current by a single blink per second. After opening the ring network, the network has to be switched on again.
Now the second short-circuit current in the open-ring network will flow directly to the fault and trip all passed NG indicators a second time. This second fault current is shown by a double blink every second and will lead to the fault location.

The earth-fault indication provides also two indication modes:

Single blink per second: There has been an earth-fault current, but it is not present any more.
Double blink per second: The earth-fault current is still present or there is an asymmetrical current in the network.

The potential-free connections between the short-circuit sensors and the display unit are done by fibre optic cables. The short-circuit sensor can be mounted on screened and unscreened cables. The connection between the earth-fault sensor and the display unit is done by fibre optic cable or by copper cable. The earth-fault sensor must be mounted on screened cables. The sensors are divisible and can be retrofitted on the cable.

The display device is powered by an exchangeable lithium battery. The fault indicators of the NG-Series have a compact design with low installation depth.

The indicators are available in different versions. Depending on the version, the fault indicator type NG-Series consists of:

– Earth-fault and short-circuit indicator type NG-EK with sensor type LK (fibre optical connection) and copper wire sensor type SE (copper cable connection)
– Earth-fault and short-circuit indicator type NG-EK with type LK and type LE (fibre optical connection)
– Short-circuit indicator type NG-K with fi bre optical sensor type LK (fibre optical connection)
– Earth-fault indicator type NG-E with copper cable sensor type SE (copper cable connection)
– Earth-fault indicator type NG-E with fibre optical sensor type LE (fibre optical connection)