Recently, while performing a reactive test on our generator, our 40-2 loss of excitation relay tripped before we reached our generator capability curve. We backed off the MVAR, the relay cleared. We increased the MVA, and the relay tripped again at approximately the same point (0.828 pu)...
Do small transformers have more resistance than reactance?
I'm trying to calculate the reactance and resistance of my 25KVA generator neutral grounding transformer. There is no nameplate, and the impedance test data shows Impedance Amps = 1.88, Impedance Watts = 230, Impedance Volts = 460...
Are power triangles proportional through per unit?
I'm trying to calculate a neutral grounding transformer's p.u. reactance and resistance. I've been given the amps, watts, and volts from the transformer impedance test, and I know the rated voltage, so I can calculate the p.u. impedance. Since...
I need to run underground cabling from my battery bank to my inverters. My inverters are rated for 6000VA and are 93.5% efficient, so I have calculated that the DC current will be 134A at 48Vdc. I have 2 inverters, but I plan to parallel the battery cables which, if I read the NEC correctly, I...
In our switchyard, we have 1 CCVT for each autotransformers, on B-phase. These CCVT's are called "Bus CCVT's" and are of "metering accuracy." The output from these goes to an autotransformer energized indication, and is also used in synchronization.
One of these CCVT's needs to be replaced...
I am recalculating the reach of a dev. 21 generator protection relay. Included in the previous reach of the device was the step-up transformer and 90% of the transmission line. The transformer is a 22.8/345KV 258/430MVA transformer. From the transformer test report, the impedance is...
While reviewing the motor starting data for a 1750HP, 7.2KV motor, we noticed that B phase starting current was significantly lower (about 50%) than A and C phases. This is not something that has been known to happen in the past. The last 3 starts had the following voltages and currents...
I have a problem with our 7200V system that I want to fix. Our 7200V system is split into 2 busses. While starting a 10,000 HP Induced Draft (ID) fans, we must shut the tie breaker. If we do not, we will drop our 480V power centers on undervoltage. The problem here is that with the tie...
