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Hello, One client is requesting for the incomer of a MV gas insulated metal enclosed switchgear (arc resistant), to include two grounding switches: one in the incoming cable connection side and another one being the usual 3-position-disconnector/grounding switch that is located between the...

Hello, I need to send the secondary 110Vac/sqrt(3)of a HV metering PT, to a remote location at around 5 km. I have found analogue to digital converters and signal transmission through fiber optic. However, for the remote end, I require also a 110Vac/sqrt(3) output, and I am only able to find...

Hello, NEMA MG1 is specifying a maximum 5% frequency variation during normal operation and also during starting: "Medium motors shall start and accelerate to running speed a load which has a torque characteristic and an inertia value not exceeding that listed in 12.54 with the voltage and...

Hello, If my understanding is correct, a motor with an insulation class F with a temperature increase B has a 25ºC margin for operating continously without affecting its design life. If this is correct, one could use a motor purchased as F/B with no risk at F/F. My question is: if the rated...

Dear all, For the design of 6.6kV cabinets, an engineering subcontractor is recommending to add a cabinet with an earthing switch so that in case that maintenance work has to be done in the cabinets, the busbars can be earthed before performing the Works. Cabinets are metalclad type and all...

Good afternoon, A question has arisen among my workmates about piping racks foundations or supports sizing when carrying also for example ladder-type cable trays. Do the dynamic effects of short-circuits in cables need to be taken into account for sizing the supports? I usually only used...

Hello, I have a ST Generator (15.75kV) connected directly to a GSU Transformer by IPBs, and then in the HV side of the GSU Transformer is a circuit-breaker (33 kV). As usually transformer manufacturers specify in their commissioning manuals that the transformer must be energized with no load...

Hello, I have seen a tender for a power plant where the single-line diagram shows Generator + GCB + GSU Transformer + 2 UAT. The only way of feeding generator auxiliaries is through the UAT, as no station transformers of MV lines are available. The connection between Generator + GCB + GSU...

Hello, I would like to know which are the differences between cast iron and aluminium squirrel cage motors in terms of performance, environment withstand,... When should be a cast iron motor used and not an aluminium motor? Thanks.

Hello, I am trying to calculate which would be the total injected current harmonics spectrum of some VFDs connected in paralell to the same MCC. I have the harmonics spectrum of the individual VFDs. My problem is when calculating the total harmonics in the MCC as there seem not to be the...

Hello, I am trying to find some type of diagram or table for dry-type transformer overloading. I have found some diagrams for oil-inmersed type transformers but no luck with dry-type ones. I need a 110 kVA dry-type transformer which will be loaded for 30 seconds max (it will be a grounding...

Hello, I have some questions that I think are related to thread238-289927 but it is closed. squasher, In your first post, shouldn't it be used Ith instead of Ik for short-time withstand current in 3 seconds? It is a question I have about IEC 60909 because if Ith should be used, then I do not...

Hello, I am looking for supliers of grounding gransformers, wye-open delta for high resistance grounding (10 A) of a 11 kV busbar. I have contacted different suppliers and have not been able to obtain anyone. Does anybody now about suppliers in Europe for this type of transformer? Thanks.

Hello, I have mainly seen MV synchronous generators connected to a generator transformer where the transformer generator side is in delta and the HV side in wye. Why not put the generator side of the transformer in grounded wye? Does anybody know of books or papers that discuss this topic...

Hello, I know that NEC 2011 explicitly forbids using the ground grid as an equipment grounding conductor while in NESC 2007 it is not explicitly covered. Let's say you have a large power plant where you have buried a mesh type grounding grid so that you have only one earth for both HV, MV and...

Hello, I am looking for 480 V 60 hz ac induction motor technical catalogues with the following data for different rated powers: efficiency, power factor, starting current, speed (rpm), starting torque vs rated torque, max torque vs rated torque, inertia, starting power factor,... I have some...

Hello, I need information about how to calculate the minimum distances between current transformers, voltage transformers, surge arresters, power transformers and circuit breakers in outdoor 220 kV substations. I have done an insulation coordination study and have the minimum phase-to-earth...

Hello, I have calculated the grounding grid of a power plant for one phase to earth faults and now I am concerned with the double phase to earth faults on isolated phase buses between generators and transformers. I have come across two pages of ABB about it but I have many concerns. -Should...

Hello, I have been asked if in a parabollic-through thermal solar plant, the solar field containing only parabollic-through collectors should be protected against lightning according to NFPA 780. I am not familiar with USA regulations, it could be the first plant to be built there. I have just...

Hello, When calculating the thermal rating for grounding conductors, Tm (maximum allowable temperature) must be entered in ecuation 41 of IEEE 80-2000. The standard gives fusing temperatures of different materials (for example 1084 degrees Celsius for soft-drawn copper). I asked some...