Hi,
Is the Earth Fault loop Impedance and Perceptive Short Circuit Current test on Mains a requirement for a Mains Work Inspection?
I was at a Rural job today where a new portion of Neutral screen Mains had been run to an existing Private Pole. New Neutral Screen was a 25mm 3C NS, but it was joined onto an existing 6mm or 10mm OverHead single x4 (3P&N). The Over heads ran for about 300m to the boundary. So it's pretty obvious that Volt Drop would be an issue, Fault Loop Impedance would be and Issue and PSCC would be an issue. But without being able to Liven, it's hard to confirm.
When livened for testing the Fault loop was 1.4 ohms at Main SwitchBoard with a PSCC of only 100A - Pole mount TX was at the Boundary. Network said they won't liven with those results - which is fair enough.
The Mains Work inspection is only for the new portion of Mains as the Over heads existed and were live previous to this work. But does the Earth Fault Loop Impedance and PSCC need to be confirmed by the Inspector before an RoI can be issued? ie Low PSCC / High EFLI won't have the ability to blow any circuit protection in an Earth Fault, meaning Installation will be unsafe to connect. Or does that responsibility fall on the person issuing the ESC?
Fault loop Impedance and PSCC Inspection requirement or not?
Re: Fault loop Impedance and PSCC Inspection requirement or not?
Inspection is required for mains work done on an installation by an installer.
Provision of short circuit protection and fault protection for mains is not part of that,
because ESR 32 makes it the responsibility of the lines company.
Accordingly, these are not matters we need to look at when inspecting.
Which makes it entirely right that this linesco would refuse connection, eg on grounds that their supply fuse would not operate within required times.
On the other hand, volt drop is the responsibility of the installer, and therefore something an inspector needs to consider.
With mains like that, the FSs within the installation would need to be hugely over-sized to keep volt drop within limits.
There's some flexibility in this, as there are several acceptable methods for establishing max demand.
But taking the most common approach, of MD by limitation;
and assuming the supply fuse is 63 A, then easy to calculate the contribution of mains to total volt drop.
One way to overcome this sort of problem is to install a current limiting device at MSB.
Remember also that while the PEW to be inspected in this case is only the new section of mains,
ESR 13 requires not only that the work done is safe; but also that it has not made the rest of the installation any less safe.
That means looking at the circuit protection of the downstream circuits.
Especially short circuit protection, as in many cases RCDs can take care of fault protection.
Provision of short circuit protection and fault protection for mains is not part of that,
because ESR 32 makes it the responsibility of the lines company.
Accordingly, these are not matters we need to look at when inspecting.
Which makes it entirely right that this linesco would refuse connection, eg on grounds that their supply fuse would not operate within required times.
On the other hand, volt drop is the responsibility of the installer, and therefore something an inspector needs to consider.
With mains like that, the FSs within the installation would need to be hugely over-sized to keep volt drop within limits.
There's some flexibility in this, as there are several acceptable methods for establishing max demand.
But taking the most common approach, of MD by limitation;
and assuming the supply fuse is 63 A, then easy to calculate the contribution of mains to total volt drop.
One way to overcome this sort of problem is to install a current limiting device at MSB.
Remember also that while the PEW to be inspected in this case is only the new section of mains,
ESR 13 requires not only that the work done is safe; but also that it has not made the rest of the installation any less safe.
That means looking at the circuit protection of the downstream circuits.
Especially short circuit protection, as in many cases RCDs can take care of fault protection.
Re: Fault loop Impedance and PSCC Inspection requirement or not?
Looking at table 8.1, they should be able to liven with 40A fuses.
But you still need to check the VD, and determine the point of supply for that.
Historically, the overhead may have been owned by the network and not part of the installation. Now the network has probably changed their ownership model, which has now put the problem onto the owner's side.
But you still need to check the VD, and determine the point of supply for that.
Historically, the overhead may have been owned by the network and not part of the installation. Now the network has probably changed their ownership model, which has now put the problem onto the owner's side.