There would be many vfds on both services. Why would vfds produce voltage spikes at the service? The only voltage spikes I am familiar with vfds producing is on the output side. They wouldn't show up on the source side.
I recently came across a double ended 480 service entance switchboard with both mains closed and the tie open. surge protection is installed on both service entances. Each surge protector is equipped with a surge counter. The surge counter from one substation recorded around 10 surges, the...
The figure seems to be showing the circuit model for a high excitation level, but still below saturation. Basically operating at the high end of its design. Think of a CT with standard burden operating at its nominal current.
There is no typical value for CT accuracy.
Look at the CT saturation curves. If your CTs don't have saturation curves available, get different CTs. You can get an approximation of the error based on the amount of excitation current required for a given operating quantity. You need to know...
The issue is actually surprisingly complicated and getting an accurate maximum inrush current for multiple transformers usually takes specialized software and a great deal of information on the system and transformers.
The issue boils down to the voltage at each transformer's primary terminals...
I should have clarified that I am mostly interested in two winding, 3 phase, 15kV class transformers between 250kVA and 5MVA. Both oil filled and dry type.
Does anyone know whether ANSI constructed transformers have a tolerance associated with the impedance value stamped on the nameplate?
I am aware ANSI standards allow a +/- 7.5% design tolerance and that UL constructed transformers can have an impedance of +/-10% of the value stamped on the...
It is a commercial building with indoor 15kV equipment. With the way they modeled the room, the ground grid is necessary to keep step and touch potentials to an acceptable level but I am not sure that the room was modeled correctly.
I was recently reviewing a ground grid study for an indoor installation and saw something that struck me as odd. The ground grid is installed beneath the basement, air cured, concrete floor of a building. There is steel re-bar inside the concrete slab. Yet the study still lists the resistance...
