Thedroid,
1- If you have higher than 40 cal/cm2, you will need to shutdown the power and do the work de-energized. Arc Flash PPE is only recommended for up to 40 cal/cm2. Above forty, there will be other hazards (i.e. blast pressure) associated with the arc other than the thermal hazard, which...
A surge protective device is designed to protect the connected equipement against very short period (Micro Second) voltage surge. It is not designed to be a voltage regulator.
Can limiters be put the load side of low voltage power circuit breakers? I have alawys seen them on the line side. Is there an associated standard like NEMA or ANSI for this application. The reason that we want to put the limiters on the load side is because we are doing a retrofill job where...
Make sure to order a resistor with multiple taps to be able to adjust the current to be higher than the capacitive charging current of the system. 5 Amps could be lower than the charging current, so it is recommended to spend some time to come up with the accurate current value for the resistor.
I am thinking 12 pulse. You may want to hook up a fluke 43B on the line side and see what kind of harmonic spectrum you would get. If the dominant harmonics are the 5th and 7th, then this would be six pulse action. If 11th and 13th then 12 pulse.
For ground fault protection on the primary, set the long time pick up to minimum, instantenous greater that four times the self cooled rating of the transformer. Curve shape and time dial to coordiantate with downstream/upstream devices. The intersection point between the curve and the...
It could be a harmonic resonance issue where the LC combination of the PFC bank is sinking all the fifth harmonic coming from the drives (5th and 7th harmonics are normally produced by six pulse drives). Usually the reactor is added to detune the PFC to sink something close to the fifth harmonic...
TestBeforeTouch: I agree with you and I believe the 10 amps value that you have for your resistors is greater than the charging current of the system, and that is why you are not experiencing voltage escalation during ground faults.
To be honest with with you, I think something is wrong with your meter/ meter connections. However:
The 100% THD obviosly is a percent value of the fundemental. For example, you could have 120% THD but the fundemental current is only 3 Amps, the 120% is not a concern in this case due to low...
300 A sounds appropriate. The CT usually sized at 50 % of the resistor rated amps i.e. 150:5
TestBeforeTouch: The resistor amp value should be higher than the capacitive charging current of the system Ic. Otherwise, you will end up with escalating voltages to ground during ground faults. If Ic...
I don't know alot about your system, But I would think that you should be able to detect ground faults on the utility side using a 67N function (directional over current) at the point of common coupling (PCC). In this case, I believe you still need a Y-Y PT only at the PCC for accurate...
I know several years ago Siemens was using the high impedance differential bus protection in thier high voltage substation design. This was implemented as a typical design for the new 400 kV substations that were part of the power interconnection projects between the Middle East and Europe. This...
