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thanks @palletjack and @7anoter4 for the responses. It sounds like you both are suggesting that leaving one end ungrounded and running a GCC/ECC should be safe. However, what about for fault currents? If the fault current is say 10 kA, wouldn't the voltage stress at that time be 20x the normal...

I have a 100m underground cable run that needs to carry ~500A. We have the option of going with concentric neutral cable or tape shield. Couple of questions in evaluating cable selection and bonding methods: 1. If I go with the concentric neutral cable option, can I unground the one end to get...

During steady state, the voltage is only 106.5% of nominal as the turbines are fed from overhead lines. @cuky2000 how would I check what you are saying? @jghrist I would have to learn a program to do that. Is it something I could pick up with tutorials in the free ATP program? Is a simple...

@davidbeach - it is a solidly grounded wye at the autotransformer secondary that feeds the turbines. The feeder breaker has a fact acting ground switch so you don't lose your wye when the breaker opens. I do have a good ETAP model and will try what you suggest and report back.

Voltage is 34.5 kV (L-L) and the arresters are 24.4 kV MCOV. This has happened twice before and they are elbow type arresters connected to switchgear bushings.

The system is a solidly grounded wye. Not sure how to answer your question about fault resistance.

I have a project involving a sub transmission line with wind turbines interconnected. Surge arresters are all along the pole line and at the base of each turbine in the switchgear with the same sizing. For some reason, the last turbine at the end of the line keeps blowing its arrester at the...

Thanks @davidbeach, but would it be fair to say that no fault current would be generated for a L-G fault on the LV side without the buried delta tertiary corner grounded winding?

I am trying to model a Wye(ungrounded)/Wye(grounded)/buried delta tertiary transformer in ETAP. The HV side is the source of fault current and is ungrounded as specified. When I model it as a two winding transformer, I am able to select a checkbox for buried tertiary. However, when I place a L-G...

Thanks David, that is interesting because I have seen engineers size this as really high CT ratios compared to the phase CTs. We don't have any real intention to use it for protection so was just going to monitor zero sequence currents with it. Perhaps we should just remove this CT then or is...

How does one calculate how much zero sequence will flow in a YYg transformer with a buried tertiary delta winding during normal operation to size the ratio of the CT on the winding? Thanks!

@cranky108 - yes it is the H0 bushing I am talking about and thank you. @argotier - this is interesting and likely why it was done since there are multiple transformers in parallel with the H0 ungrounded but a surge arrester connected to the H0 terminals. Essentially what you both are saying...

In a 230 kV system, what is the thought process for leaving the H0 of a WYE-WYE transformer ungrounded? If the HV bushings are rated at 900 kV BIL, would this make the requirement for the H0 bushing 900 kV BIL as well since it is ungrounded? Thanks in advance!

What are your approaches to modelling transformer primary CLF fuses in arc flash studies? Currently, we do not consider them and I am not sure how to accurately model their affects in ETAP. Thanks!

What is the general thought on lateral ties in duct bank arrangements that encircle the entire group of conduits? Would this cause heating in the duct bank and if so how would one model this in an ampacity calculation?

@7anoter4, I don't think this answers my question. I am aware that grounding both sides of the cable will cause circulating currents and have a play in derating the ampacity but I want to know if a small grounding system is required at the splice box. Thanks

Hi, I have a project that involves splicing an MV cable at an underground splice box. The cable concentric neutrals are going to be grounded at either end. My question is if a ground loop and rods are required at the splice box? My thought is that since the current will flow back through the...

I am doing the grounding design for a small padmount transformer adjacent to a building. The transformer is a delta-wye (27.6 kV-600 V) and it is connected to a 44 kV pole from the Utility with no shield wire. I am not to consider any split factors in my design. My question is, what do I...