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Hello Can a Current Transformer with a ratio of 50/5 be effectively utilized on a 1200A bus or incoming cables? What are the key considerations when using this CT on a higher ampacity application? Also, any recommendations for CTs that can accurately detect 48 Amps?

Hello I have a harmonic current spectrum from a system test performed which could be only loaded 25% of its rated load (the remaining loads are still under construction). All the loads are L-N well distributed. There is no other type of load in this system. To obtain the full load (100%)...

Hello All, Is anyone aware of a manufacturer or firm that makes (pre-fabricated) an enclosure with DC (up to 1000vdc) and AC contactor with 24vdc coil? Will be using this for testing PV inverters. The reason I ask is as pre-fabricated enclosure will be tested and listed as well. Attached is a...

Hello All, Can someone help me with a link to interconnection requirements for California (SCE) when adding Energy Storage and PV to the existing office building? For both Export and Non-Export.

In the attachment, it says "Control power to the Shunt Trip with Lockout must be removed for a minimum of 0.25 seconds before the breaker can be closed". Why wait for 0.25 seconds what is logic behind...

I am working on short circuit calculations for a system. There is an HVAC unit (nameplate attached). I did verify (Unit Power Supply) the cable and upstream protective device do meet the minimum circuit ampacity and max circuit breaker size, respectively. I have the following questions about the...

Is there a REVERSE transfer switch? I have seen a transfer switch that switches a load between two sources. Is there an application or product which operates opposite to a typical transfer - switch between loads instead of sources (A single source with the option to feed a small ampere load vs a...

Hello All, I am looking for any ideas and a sample electrical design if available. A design to feed I want to connect and feed a separate load contactor-based design to switch between different loads when from a source. As shown in the attached picture (it is high level) the generator feeds the...

Hello, I was wondering if anyone can share a sample sequence of operation for generator paralleling switchgear.

Hello All, I am working on my first electrical design project which entails to size breaker, wire, conduit, grounding, etc. In the project, I need to design an electrical layout to have a switchboard which will have DERs (solar, Battery, and windmill) along with utility *& conventional...

I had a question about the CT wiring to the relay shown in the picture. I was wondering is there a reason to show the wiring swapped other than connecting the polarity to the polarity input of the relay.

Hello all, I am working on prepping relay files for SEPAM. I see there is a setting mode of 10I/Is vs TMS (Time Multiplier Settings). In the SKM software, the selection is available to use either mode for curve selection. I was wondering based on experience why use one mode over the other when...

Hello All, I was wondering if anyone has a spreadsheet template of an SEL relay (SEL-751 specifically( one has created with setpoints, I/O mapping and MODBUS mapping which I can use as reference to create one. The reason I ask is to get thoughts on how to present the MODBUS and I/O mapping in a...

In a motor protection application using relays, I have seen the trip circuit having a normally closed contact in the run circuit. What is the reasons to have normally closed contact in this application where is in normal feeder protection the relay contact is programmed as normally open? Is the...

Hello, I need advise on what all to keep in mind when adding distributed generation/microgrid as a second source to the existing Main-Tie-Main. One main is utility service and second main is a spare. If the second main is fed from a distributed generation like PV or fuel cell. What all to keep...

Hello All, Attached is the link of three winding rectifier transformer. It has an impedances shown for two kVA bases (8000 and 10000). Per my understanding, the impedance is higher for higher kVA and lower for lower kVA rating. But the nameplate shows the other way. Why is the impedance for a...

Hello All, I am looking for a control power load calculator (spreadsheet) developed for switchgear control power sizing to ensure the CPT and UPS ARE adequately sized. Any manufacturer spreadsheet would do I can modif the parameters.

Hello All, On a multilin 750, I want to block the second phase instantaneous element. It has an option to block overcurrent function, in the drop down it has different input selections. Based on the attached image: 1. When the voltage is applied/available across the INPUT-1, the contact will...

Hello All, I am an electrical engineer with current job profile related to Power system engineering (Power system study, relay programming and PLC). I was wondering if anyone has done any search or has any advise on what skills are good to learn to develop more on the power systems engineering...

Hello All, Is there a standard provides guideline on what should the 27 (Undervoltage), 59 (Overvoltage), 81 (Under & Over Frequency) and 47 (Phase Sequence) can be set for a Main-Gen-Tie-Gen-Main configuration (480V). It being open transition.