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Stevenal Thanks That makes lot of sense. 1) NEC has no maintenance clause 2) Although usually applied to utilities. However, I understand that there is mandatory requirement for Safety and protection of operating personnel to have a One line diagram in a substation. Either OSHA, township code...

Shkim2000 You are right about the “ the Motor starter Breaker should open first if the motor developes fault” The coordination expects that the load side motor breaker should sense the fault and act before the switchboard fuse blows. Even if the single fuse in switchboard side (upstream) blows...

Powerproblems Can you elaborate “primary transformers” ? Do you have your own secondary transformers? Do you attribute the failure to lightening, Overvoltage and grounding ? Is the primary side high voltage and Delta? And secondary Wye? Is the secondary Wye 4 wires? Do they have TVSS, Movs...

mc5w You are right Ballasts, UPS , incandescent lamps need to be addressed when overvoltage continues for appreciable time. Not motors. Marvin

dpc Thanks for your reply. 500 volts at no load or light load is expected. What about 510-520 volts at light load for other devices for 2-3 hours everyday? Marvin

Stevenal Thanks. I agree with you. About motors. Motors have good insulation. Also are characterized by Inertia and also there is back emf to match the supply voltage. The speed is not going to be affected by higher voltage. The devices I am worried about are solid state, electronic devices and...

Guys Could anybody please direct me to Appropriate code, practice requiring Uptodate One Line Diagram being displayed in a Medium Voltage Substation showing the incoming, tie, outgoing and feeder breakers. I know of NEC 215.5. Is there other code more eleborate on this subject? NEC, OSHA, IEE...

Truely this a big project. Depending upon the size of the generator and the desired protective functions Differential, Over current, Reverse power, Loss of excitation and what not? Generator is very critical and expensive equipment. Marvin

The simple answer would be 1) Appropriate Resistance is introduced in series with each winding to start. 2) After a suitable time delay the resistance are bypssed and the motor reaches full speed. 3) Alternatively the series resitance is gradually reduced (like a reheostat) and finally the full...

mc5W Thank you for the relevant information. I will visit the link and read the details. I really have to worry about electronic ballasts and other elctronic devices. marvin

Alehman I agree that the 4300 voltage is within 5% . Actually the voltage is 4400 which is above 5 %. First I would like to have the meter calibration cheked and the data electronically recorded for over 3-4 days. Before approaching utility I want to find out if other users had any problem with...

alehman Thank you for your quick and valuable response. The volatge is measured at supply end. Utility supply volatge is also more than 10%. Normal 4160Volts, measured 4300 volts. You are right about cables because cable are rated for 600 volts. marvin

Is it only leading power factor? There could be over voltage, Harmonics as well when Computers and UPS are involved? What is the UPS size / capcity/ Load? Single phase,3 phase 120 volts? marvin

The Power Conditioner maintains the output voltage when the Load changes or the when the supply voltage changes. Like a Voltage regulator. This is one possibility. Marvin

Guys, Did anybody come across any study on the effect of Sustained over voltage in a 3 phase 4 wire 60 Hz electrical system? The actual voltage of the system, when measured, was found to be above 500/290 volts. The nominal rating is 480/277 volts 60 Hz. What long term (3 months, 1 year)...

The breaker with diesel generator is generally designed and set for the protection of the Generator. Beoyond the ATS, existing downstream breakers take care of the fault on load side. You may not need any additional protection.

1)Pneumatic Actuators have been proven for this type of application. It is easy to operate,maintain and test the pneumatic actuators. These can be set for the desired fail safe position. It certainly has a lead over electric actuators. 2)For your application (Power Plant)Relaible supply of...

1) You may have to segregate the 1 MW load in the cement plant and have it fed from utility. (Existing connection). 2)Balance of the load may be fed from new feeder of power plant. 3)Provide a transfer switch to feed 1MW Load. 4) Tarnasfer switch will have Normal feed from Utility and...