Recent content by JezNZ

It is an economic balancing act between size of distribution to be fed and therefore cost of losses vs cost of equipment. Standardised equipment is cheaper. Lower voltage equipment is cheaper. Higher current equipment is more expensive. Higher fault current equipment is more expensive. Depending...

3 x 100A zero sequence (in phase) which sum in the neutral to give 300A through the resistor.

Hi All, Been a while since I've posted here! Currently working on the design-build of a microgrid being the first to meet regenerative certification criteria (105% generation of consumption) in the locale I am. The microgrid will operate both grid-connected and island-mode and is IBR HEAVY...

Thanks for response, however fyi I found DL 01.04 is much more relevant, specifically section 6.5.1 pretty much covers off the question.

Since this is LV. Use a load-break isolator, not a disconnector (off-load). There's no real purpose to put circuit breakers on both the supply side and at the incomer of a board unless this something like a rising main configuration, where that incomer will also serve other boards.

Unfortunately they tend to put bridges where the road is!

Hi, I am looking for advice on the grounding / earthing of structures beneath transmission lines. The scenario is a 220kV line which crosses a waterway, and a temporary steel bridge structure also crossing the waterway is being installed, directly underneath the lines. Does the NESC Handbook...

According to IEEE Gold Book - Insulated Bus Bars reduces the likelihood of a bus fault by approximately 90%. Depending on your reliability requirements and cost of outage impacts, that may or may not be a significant figure. On a recent project of 100k/hr plant outage we calculated insulating...

3 phases, interconnected via various sources or load impedances etc. In an earthed/grounded system, when one phase or multiple phases are faulted to ground, current will 'flow' in all phases in-phase through the system into the fault. This in-phase current is the zero sequence current. In the...

Hi All, For the purposes of Fault Analysis, I'm modelling in etap an 11kV industrial system that until recently had embedded generation. The system is earthed via a YNd11 12.1kV / 240V open delta transformer with an LV resistor. I can't find a way to model this in etap directly with the LV...

Only speaking for my locale, but industry best practice is to always earth/ground metallic substation fences. The rationale being that unbonded fences overtime often being bonded by accident or as part of any upgrades/additions/maintenance, where the earthing/grounding design has not been...

Hi, I have read up on the use of the intersecting curves method in the Megger earthing guides and some (very old) material by Dr GF Tagg - however the method is not addressed in IEEE80/81. I have also seen a few prior posts in the forum mentioning it. I am curious to understand more detail...

You can get specialist sealing products for this kind of application like these: https://www.hauff-technik.de/en/category/cable-entries-1/press-seals-27 Sealing the cables individually with pressure fit seals is the only way you're likely to get a truly watertight penetration in the...

1. Start with basic functional earthing. 2. Calculate the fault loop impedances. 3. Calculate your earth fault return current. 4. Determine protection operating time. 5. Determine tolerable safety limits. 6. Determine EPR (Earth Fault Return Current x Earth Grid Impedance). 7. If EPR < Safety...

Hi, We have a project on-going where we will design-build a containerised portable substation for 11kV vaccuum switchgear. We have built several in the past but not been directly involved in the design. The feedback from speaking to the project managers involved in these works is that the...