Now a days switchboards are built in three ranges:
-Upto 12 kV
-24 kV
-36 kV
Therefore price wise not much difference between 11 kV switchboard and 6.6 or 3.3 kV switchboard.
The difference is in motor price. 3.3 kV cheapest. If the cost of 3.3kV motor. But for one motor 3.3 kV option may be...
In star/delta motor starting the line contactor(i.e. the contactor other than start(which connects the winding in star) contactor and run(which connects the winding in delta) contactor) is connected inside the delta connection. This contactor can also be connected outside the delta connection...
You should not go lower than 0.1 setting. In fact it is good that the relay is not opertaing at 0.1 setting. In my experience this is a borderline setting.
If you have to go lower0.1 sec then something is not right.
But if there is no way and you have to go lower then option is go for...
1. For the kW rating, power factor of the motors appear to be extremely low. Should be around 0.9. You have mentioned pf of about 0.6 which is unsual. Please check. Why do you have to by such a motor?
2. If both the motors are operating simultaneously then the pf compensation could be at the...
Hi I have just done the design for a 300 room hotel. The load can be calculated as follows:
a)For each room:
600 W for lights and general power
1500 W to 2000 w for HVAC if electric heaters are used. If hot water is used then less just the fan load. Please ask the HVAC designer the load for...
No problem in using aluminium provided:
- Size selected is adequate for current capacity and voltage drop
- While instaling lug on the cable a special compound is aplied to reduce oxydation. Similarly while terminating a cable same compound is applied to the contact surfaces. I think the...
The current in the cable produces magnetic field and the armour acts as a conductor loop. A conductor in magnetic field means voltage is produced and current flows. Better method is to use one cable for three phases.
For modern electronic and numerical relays the CT secondaries are always star connected. The relay has inbuilt logic to account for phase shift.
The relay operated correctly because there is unbalance in current between primary and secondary side.
It is not clear where the current was...
Best to run R-Y-B-N together. Thant means three bundles in your case. Each bundle containing one conductor of each phase and one neutral conductor. This arrangement will keep the electomagnetic field to a minimum.
If the transformer and LTC are identical then the circulating current would be momentary. After paralleling there should be no circulating current.
The circulating current during low voltage period will be lower than high load period. Because during low load period the bus voltages on either...
The earth fault relay could operate:
a) due to in rush current as a result of transformer energisation.
b)if the transformers are loaded then unbalanced load currents due to one phase open
c)harmonics. relays are supposed to be immune to harmonics but that is not always the case
Two types of load shedding are used:
-Frequency relays: By power companies. They have sufficient time to shed the load. If your plant has a generator operting in standalone mode then it is possible to use it. This is not a loss of generation load shedding. It is protection for turbine...
1.1.5 times voltage for 5 sec should not cause any damage to alternator because even during an insulation resistance test 5 kV is applied for a minute. The probable damage could be to AVR because during an insulation resistanc test the AVR is disconnected to avoid over voltage.
2. On no load...
Differential protection is selective (it operates only if te fault is within its zone) and therefore is set to operate faster(that means no need to delay). Therefore the fault is cleared quickly and rest of the system can continue to operate normal. Normal o/C and e/f protection is time delayed...
