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Two existing generators feed a 3W MCC equipped with an NGR via a transfer switch. The two gens are now being connected to a 4W sync board. The sync board will new feed the existing 3W MCC and a new MCC that is also a 3W. Questions: 1.Is there any issue with the exiting configuration – 4W ATS...

A supplier tells me that their new 3 MVA substation transformer has in inrush current of 18X FLA. This number looks suspiciously high to me, I am wondering if anyone else has seen this.

So as I understand, the recommended time deference in coordinating electronic relays in series is 0.3 Seconds. I am wondering at what point this time difference should be measure on the TCCs since the delta increases with time due to the log scale. Should it be measure at a particular time?

OK, Thanks. How about the two relays, is it better to have definite time or is current sensing in the instantaneous range sufficient?

I am coordinating a relay associated with a MV breaker with a LV breaker downstream for ground fault. There is an existing relay upstream of the new relay which has an instantaneous setting for ground fault but no definite time setting. My thought was to use instantaneous with definite time to...

I have MV breakers in series: Main breaker to a Feeder breaker – Feeds another gear with a main and feeder breaker. I am wondering the minimum time that should be allowed for coordination. I think IEEE recommends 4ms but I think that was based on the old electromechanical relays, is 1ms...

IEEE C37.102-2006 (Guide for generator protection) says: “Instantaneous unit is set to pick up at 115% of FLA and is used to torque control the time-overcurrent unit” What does this mean when using an electronic relay (Multilin G30)?

G-30 - Looks like they expect a step up/down after generation. I think I should just ignore this setting.

Setting up 2 MVA, 4160 Genset Protection Relay. I notice input settings for a transformer (Not CPT) and the manual makes reference to transformer differential. What transformer information should be entered... utility by chance?

I should mention I have 12-750kcmil (MCM) copper conductors (4 per phase)

How much room do I need for stress cone terminations? I have 5kV gear that was modified for top entry by adding a 12” deep rear extension. Now that I have the busses there and facing upwards, I am wondering if that is enough space for stress cone terminations since the cables coming in are...

We have a 1MW natural gas genset connected to the plant load via a breaker type ATS and to a load bank via a 1600A breaker. It is intended to keep the load bank breaker closed in order to keep the genset loaded to at least 50%. Load bank loads will adjust automatically in steps depending on the...

Hi jrael, you are right in that this rule requires 120V control circuit have 600V insulation if run in the same raceway as the 600V motor leads. I believe the intent of this rule has to do with voltage impression. It prevents having conductors of different voltages getting crossed and...

Canadian Electrical Code Rule 12-904(2) states that no raceway shall contain conductors that are connected to different transformers or other different sources of voltage unless there is a separation barrier or the conductors are used to control remote devices. Question: Can conductors...

We have 3X 4000hp MV motors. The idea was to have 2 VFDs so that the first two motors can be started by the 2 VFDs and if the 3rd is required, one of the already started motors can be placed cross the line and we can use the VFD to run the 3rd. Problem is that utility company is concerned of...

Great Thanks!

Does a VFD provide both overcurrent and Oveload protection? The situation is that I have 125hp motor with a 200hp VFD. I do not want the upsteam breaker to be the limiting factor if it does not have to be... so I would like to size it for 200hp not 125hp. Is the motor still adequately protected?

Hi All – I have now experienced this a few times and have seen some literature on it which does not all match so I thought I would seek clarification. I have a small branch cct Xformer (15kVA) with only primary breaker protection (30A Molded Case). According to ETAP, the secondary bus fault...

Thanks I will investigate. The end user wants to keep both in the event one of the gears is not online - the two serve 2 different and independent operations. I was thinking to do nothing - The only issue I see with this is possibly alarming the fault from one of the gears in the other making...

Hi All; I would not design a system this way but this is the current situation: I have a D-Y X-former with double lugs on the sec. feeding 2 gears. The first gear has a 5A cont. NGR. The second gear also has an NGR (2A cont.). I know I have 2 paths to ground since both are connected to the...