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Hi... I am looking for a explanation in regards to this obsolte product P4 A relay from Multilin. A 225 a breaker is feeding two 100 HP fans with independent soft starters. The application is ventilation fans. The pitch of the fans has been changed, so they are not taking full 90 A as they...

Hi, I have done it quite a few times but now I have an application where I have to go into a bit of detail for specifying a circuit breaker. I know that if I have to operate a molded case breaker or for that matter any type of circuit breaker remotely or external means, I need a shunt trip...

Hi,,, I am researching about the max. allowed cable length from VFD to motor. I spoke to one of the vendors application engineers and his answer was that max. what he has seen is 100 ft. My requirements are 400 m. I was wondering, is there a way instead of just relying on vendor, I can make a...

Hi.... I have asked few questions about this grounding grid and it is still on going. We have decided to use Eric Ground Enhancing Meterial on the periphery of the ground grid. The ground grid is in the middle of the rock. Excavated and backfilled with granular B. I am just wondering, to...

Hi, I was wondering about a practice followed by Utilities of using a disconnet switch to disconnet two grounding grids. I tried many vendors but no success.Could you kindly advise. I have two grounding grids, one of them is under construction and another is an existing remote grid. I want to...

Hi, I am not sure, if I am using a smart approach while trying to accomodate step and touch potential as it does not seems to be economical. My GPR is high approx. 18 KV. but local authority wants us to satisfy Step and touch potential issues. I have reduced the size of meshes to half, I gues...

I have a 225 A molded case thermal magnetic breaker. I beleive it is 80% rated that means it is 185 A continous rating. I have three fans 75HP, 75 HP and 65 HP at 600 V. The total ampacity FLA is 210 A. That means I am overloading this breaker. I am not sure, how this will effect the thermal...

I have exhaustyively studied threads on Motor Contribution and they did not answer my question so I am putting forth my concerns. I am using ETAP for my simulation. I have few observations and would like a confirmation to these mentioned below. " Arcing current is less than the three phase...

Hi, I am kinda doing this for the first time and just worried that I may not be missing some thing big time. I have two hollow steel structures for a substation, where I am putting class solid copper 72 " 3/8" dia air terminals mounted on a copper base plate and then connected to a #4/0 SDBC...

Hi,... we are planning to use this GEM(Ground Enhancing Material) from Erico. As the location is in Northern Ontario near a mine site and is very rocky. There will be grading done to have foundation done for structural work. I guess some soil fill up to two feet. I am just seeking an advise...

Hi, I have this lattice incoming structure terminating a 69 KV line in to a small substation yard. For the lightning and shielding analysis, I want to protect the equipment. Could you advise any link that could just guide me in this direction. the height of the structure is 8 meters and the...

Hi This is my first time designing a small substation. Being an EE, I am not familiar with structural aspect of it. Eventually, this issue will be handled by a structural engineer but I still want some grip over the issue as being an EE, I might have to give them some possible type of structure...

Please correct me if I am wrong. In case of distribution voltages up to 25 KV, utilities use fused cut outs for pad mounted transformer or lateral tap switching. But after 25 KV, A standard load break switch or disconnect is required to do the same job ? I am sure, utilities dont have to abide...

A contractor submitted a test proposal and added a small note: "Please see that if GPR as well as the step and touch potentials cannot be achieved as required, additional on-site testing will be required and the possibility of having a remote ground grid may have to be considered,". I am just...

Hi All, IEEE red book says that a high resistance grouding is not recommended on systems at 15 KV because it requires a very sophisticated relaying. That measn NGR should be set to have a ground fault current of 100 A or more. In todays's world where Digital relays are a trend, Do you guys...

Hi, Utility provided me with a Three phase fault level, zero sequence impedance and 3 Io for a new transformer connection. Why this three with ground fault current. People from utility can put a word. Thanks

Hi All, I might get an opportunity to work in some utility metering related work for the provinical utility. The local utility hires consulting engineers to do this kind of work. I have never done this but I have voluntered for it and am ready to learn it. It will be under the supervision of a...

Hi All, M421 from CSA, Mining electricity code in canada is not that helpful in clarifying grounding grid design for underground mines. It talks about a GPR of 100 V. As per MSHA, it is required to have a Safety grid and a substation ground. The three conductors Phase A, B and C come from the...