At a local industrial site they have a set of 30 year old 115 kV single conductor cables terminated using potheads. The shields at the source ends appear to be terminated to ground through a carbon air gap mounted on the cable support structures (see attached photos). Can anyone confirm that the...
Is a generator step up transformer typically specified for hydroelectric generators in the 10 MVA range or is a standard distribution transformer typically applied? I understand that GSU transformers have different specifications for power flow in the reverse direction for large generators but I...
I am struggling on how to address system ground fault currents on load substations connected to 3-wire 44 kV sub-transmission lines with no ground return path (no neutral or overhead ground wire). The utility quotes a zero sequence ground fault current at a point on the line however I am...
We are working on a situation at a remote mine site where four 4160 Volt, 2 MW Caterpillar diesel generators are operated in parallel in an off-grid configuration to provide power for the site. Over the span of many months, several of the generators have been experiencing cracking of the stator...
I am working on completing a ground potential rise and grounding study for a large 10 MW ground mounted PV installation. The site will be interconnected to the utility grid via a 44/12.5kV substation with the substation ground interconnected with the PV module grounding system. The 44kV system...
We are working with a client who is experiencing failures of their single phase air core shunt reactors applied at 7.2 kV. The system consists of extremely long, lightly loaded, underground cable runs along railway corridors. Reactors fairly regularly burn up without necessarily causing an...
Does anyone have a good reference on estimating or calculating power system capacitive charging current in order to apply system ground fault protection in medium voltage applications?
We have a 256 kW, 600 V induction generator coupled to a hydro turbine. We also have a 120 kVAR capacitor bank which switches in step after the generator in online. The unit is connected to a relatively small residential utility distribution system via a 600/4160 volt step up transformer (HV...
I am working with an application where an individual is planning to connect a 256 kW, 600 volt three phase induction generator to the utility grid via a 600/4160 volt step up transformer. The transformer installed is HV wye - LV delta and the desire is to install a 3 conductor armoured 5kV cable...
I have a situation where we need to splice a length of shielded 8kV rated cable to non-shielded 5 kV cable for a failure repair on a 4160 volt system. Does anyone know if the 8kv cable can be treated similarly to the unshielded cable within the splice or will excessive voltage stresses be...
I would like to obtain some suggestions on addressing possible safety hazards associated with making modifications to high voltage (115kV) switchyard buried grounding grids such as when new equipment is planned to be installed and/or the yard expanded. Common sense tells me that any connections...
I have a question regarding remote ground electrode arrays as used for reducing the station ground resistance of high voltage substations installed in difficult grounding conditions such as rock or sand where soil treatment or deep well electrodes are not an option. Some utility installations...
I am attempting to determine the actual 115 kV ground fault current at an industrial substation some 2.5 miles from the main utility 230/115kV transformer station. The fault current has been provided by the utility at the transformer station and the tap line is a wood pole line with two 5/16"...
I am grappling with the issue of supplementary bonding to ground for metallic enclosures. Typically I have seen larger metallic control system enclosures bonded to ground using a separate insulated ground conductor (typically #2/0) presumably to minimize the risk of someone touching the cabinet...
My question concerns system grounding of a 13.8 kV distribution system where there are no qualified electrical maintenance personnel on site. The main incoming transformer is a 25kV/13.8 kV 5000 kVA delta/wye unit where the secondary neutral bushing has been left disconnected. The system...
I am working with a 44kV subtransmission line with delta conected transformers at each end. There is no skywire or counterpoise conductors and no obviously no neutral conductor. The client has installed a zig-zag grounding transformer 3 miles from one of the stations however the line in built in...
I am attempting to model an industrial plant 115/13.8 kV switchyard ground grid using ETAP software. The step down transformer secondary power feed cables (and low voltage control cables) leave the fence enclosed switchyard and connect to the medium voltage switchgear approximately 2000 feet...
I have an application where I need to apply ground fault protection on the HV side of a customer's delta-wye transformer in the event of loss of the HV utility source (which is supplied from a solidly grounded wye connected transormer). There is a generator connected to the LV side of the...
