LV Sensitive Earth Fault Protection
|Funding mechanism||Network Innovation Allowance (NIA)|
|Duration||Mar 2018 - Jun 2019|
|Research area||Low Voltage & 11kV Networks|
The project naturally divides into three workstreams:
- A workstream to test alternative methods to detect contact between a human and a live phase conductor, select the preferred option then produce and test a prototype detection device;
- A workstream to define and test a retrofit device which can act on receipt of a signal to cause mains supply to be quickly removed from an LV feeder;
- A workstream to integrate the prototype supply interruption and detection devices and then test them in the field.
Although safe methods of working on energized LV feeders have been developed and are common practice across all GB DNOs, they cannot prevent accidental contact between workers and live conductors. Such accidents result in injury and can result in death.
The protection typically applied to the LV distribution network, in the form of LV feeder fuses, provides protection against large currents due to short circuits. The fuses avoid rapid heating and physical disruption of network components. This protection therefore can prevent physical injury of people near network components in the event of a network fault. However this protection is not designed to, and is not able to, respond to the low levels of current caused by accidental human contact, which can deliver a fatal electric shock.
Sensitive Earth Fault Protection for LV Feeders. This would be installed as a temporary retrofit before the commencement of any live working and removed after the work has completed. The additional protection would act to help prevent severe injury or death from inadvertent human contact with a live phase conductor during work on an LV feeder.
The protection device that is required must therefore detect that contact has occurred and remove the supply before severe injury or death occurs. Survival from electric shock is dependent on the magnitude and duration of current flow. Therefore, there might be a useful trade-off between the required sensitivity of detection (and hence false negatives) and the speed of action of a device to remove supply.
It is preferable for the device(s) to be easily fitted and removed in a relatively short time so as not to significantly increase the time typically required to carry out work on an LV feeder.
It is preferable for the fitting and removal of the device(s) to not require any supply interruptions.