In Canadian Electrical Code- does 8-104(4)(b) [8-104(d) reads: With 100% rated circuit breaker, 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3] still apply if we're sizing DLO cable based on Table 12E [Allowable ampacities for...
Is it common that a transformer could be rerated with a new nameplate to a slightly smaller kVA in order to maintain code requirements for cable sizing?
For instance, a 5MVA transformer primary is a few amps more than the ampacity of a smaller cable. To bump up a size would be a ~$20k cost to...
Is it allowed to use a multi-conductor cable using 2 wires for Circuit A: 208V exhaust fan originating from a contactor in a panel, and also use 2 more wires of the same cable for a 120V line voltage thermostat that goes back to the same contactor control circuit? The thermostat switches the...
Canadian application here, but should not be different than NEC. I'm in the middle of a tussle between two very experienced guys here about conductor sizing on a motor branch circuit fed from a MCP and OL.
Example:
On a 50HP/600V motor- FLA=52A as per code table.
Simple Calcs:
52A*1.25=65A...
Hi Guys,
Looking at specing some switchgear bound for Australia. We have zero specs other than they want a Terasaki breaker. I know this is a fairly open-ended question, but I am looking for direction on possible certification requirements for Australia-bound low voltage switchgear.
Am I...
We're driving a gen through a gearbox. I have the value of the engine moment and the generator moment. How would I calculate the combined value of moment of inertia for the genset?
Say we have two groups of 2 generators, each group capable of 4000A output. And we connected the load/utility line to the middle of the bus between each group. Can we get away with sizing each generator switchgear bus to 4000A each, and simply have a middle transition cell with 8000A of bussing...
Looking at ratings on some motor protection circuit breakers, they have ratings for say, 277Y/480 or 347Y/600. If we have a low voltage generator with resistance grounded neutral, it's not considered a delta system really, but we also wouldn't consider it a 277Y/480 correct? So in effect, these...
We have a 1500A utility feeder with 1500:5A protection CTs. We are connecting internal generation that will displace the utility power, but not export power to the utility. We will maintain a minimum import, and when we do, we can have as little as 20A incoming from the utility.
For the purpose...
We have a 4160V to 600V Delta (primary) Wye (secondary) transformer, 1.5MVA.
I had planned to simply ground the neutral on the secondary wye side as the load bank does not require line-neutral load. I understand that this poses a risk for excessive ground fault current to flow.
We have a zero...
I have a 1.5MVA transformer with a 600V secondary. The transformer is a 220 class transformer so 40degC Ambient + 150degC Winding Rise + 30degC Hot Spot = 220degC.
My question is: What temperature ratings do the cables have to be?
If you were to analogously compare a transformer insulation to...
Before anyone says- I've already completed a search on here for info about sheath grounding. Regardless, I still have questions.
Situation: Parallel 480V generators placed 25ft away from switchgear. Some applications have ~400A/phase, some applications have 1800A or 900A/phase in parallel runs...
Hello All,
I am trying to match a IEC current transformer rated at 15VA, Class 10P10, 400/5A. Has a secondary turns of 80. Wondering if anyone has a supplier in Europe that we can order directly from, as none of the North American suppliers are able to help us out by matching exactly that.
It...
We've got a 4160V system with 4 generators FLA=370A (grounded Y) paralleled to a utility transformer. All gens and the util TX have 25A/10s NGRs on the neutral point. All NGRs have relays and monitors. All feeders with motors have zero sequence CTs, are ungrounded.
I understand neutral currents...
Looking to see if anybody has used Alfa Transformers out of Arkansas before.
The cost savings of using Alfa is quite appealing as they would be supplying us a medium voltage, dry type transformer around 1.5MVA. It will be used in an Nema 3RE outdoor enclosure with temperatures from -40degC to...
I am attempting a load flow analysis on the following setup:
I have an oversized generator (550kVA) coupled with a gas-fired turbo engine whose output is 400kW at pf=1. Since the output of the generator is limited by the output of the engine, how is this represented in ETAP.
Specifically, when...
Looking for some indication as to what is a better system to use- having an NGR with a standalone NGR monitor similar to the Littlefuse SE-330 ( http://www.littelfuse.com/products/relays-controls-and-systems/protection-relays/resistance-grounding/se-330/se_330_20_11.aspx ) or utilizing relay...
From what I've seen in the CEC there doesnt seem to be an indication as to how much larger to size a transformer than the load. The code makes great mention of sizing the OCPD or conductors, but not the TX itself.
Particularly, if I have a transformer for a stand alone load bank, with no future...
Does the zone of protection for generator overcurrent and/or differential protection protect a fault on the cable from the generator to the next downstream circuit breaker? Say the cable is 100ft max.
Few questions:
1) If a main or feeder breaker has LSIG functionality, does this remove the need to have 50/51/51G protection in an external solid state relay?
2) If so, is one more desirable over another? Obviously SS is more flexible but breaker LSIG would be more “custom” as it is provided by...
