I agree that you need to check with GE. You can probably upgrade the firmware for the older relay so that both relays are the same. Firmware upgrades are usually quite easy with the GE/Multilin devices.
I looked on the Cutler-Hammer web site and there is a lot of info about the MOR relays. I'm not sure it's what you need, though. Go to the search engine on the C-H site and search for MOR.
Good luck.
Why would you use a 600 volt base to calculate per unit for 69kV cable? Is the cable actually connected to a 600 volt system? If not, I think you are using the wrong base voltage for that cable. Remember that the base MVA stays the same, but base voltages change across transformers.
Do your math again. I used R=2 and X=2 and came up with the parallel combination of Z=1 +j1 which is correct. Be careful of all the j^2 terms in the equation - don't forget that j^2 is -1.
It's not surprising that you are getting those voltages to ground with the connection that you have to the meter. With no reference connection to ground, the entire metering system is floating with respect to ground and the line-to-ground reading will be all over the map, as you are seeing. An...
I have seen both approaches used successfully. The tandem 50% capacity motors has some appeal particularly if there are times when only half the power is required. It can also provide some redundancy at reduced capacity, which may or may not be worthwhile in a sawmill application. With either...
Call Chuck Mozina at Beckwith Electric. The standard 3425 relay is only rated for 600 volts DC, but Beckwith does a lot of custom designs and the price is usually not unreasonable. I'm sure they could come up with a design for 1200 volts.
For a single drive, I don't think it really matters. The only real effect of either the delta-delta or the delta-wye isolation transformer is to provide additional source impedance. The delta-wye connection would provide some shunting of triplen harmonics except that the neutral is normally...
The Yyn connection will phase out OK with the delta-delta connection that you have now, but it will not eliminate the grounding transformer unless the Yyn transformer includes a delta tertiary winding sized to provide an effective ground and to carry the continuous neutral unbalance current.
jghrist -
If the 11-0.44kV transformers are the only load on the 11kV system, then I agree with your comment. I assumed that the 11kV system was a typical 4-wire distribution system that would have single-line-to-neutral loads and a few delta-wye transformers that the original post mentioned...
There are two possible reasons that the 66kV earth fault relay operated under the conditions that you have described.
1. With a YnYn connection on the 66-11 kV transformer, the 11kV system would also see only two energized phases when one of the 66kV phases is open. If there are...
The zero sequence impedance of a three-legged core form transformer will be 85-90 percent of the positive sequence impedance as stated previously. For five-legged core form or shell form or any configuration that has a complete magnetic circuit through the core for zero sequence flux (i.e. no...
Reactance grounding is commonly used where the generator must supply unbalanced line-to-neutral load. Resistance grounding cannot be used in this application because the resistor losses would be prohibitive and the resistor would run quite hot due to the continuous neutral current.
It's not unusual to see some unbalance in the currents during this type of test. It is frequently due to unbalances in the shorting connections. At high current levels, the impedance of the shorting connections is a significant portion of the total circuit impedance and it is difficult to keep...
I never use this feature on the SR745 relays. It's just more trouble than it's worth for the nominal reduction in slope that you could get in the settings. I don't really trust the resistor network to be reliable enough for use in a differential protection scheme anyway.
If you are quite close to the zero sequence source, resulting in a low zero sequence source impedance, then the zero sequence voltage may be very low even though the zero sequence current may be very high. As you move the fault away from the zero sequence source the zero sequence fault current...
I still contend that the 120/208 neutral on the transformer can operate ungrounded with no problem. I have seen this connection many times in utility distribution systems in the midwest, most commonly for 12470-240 volt three phase service with a center tap on one 240-volt leg for 120/240 volt...
