Hi,
Anyone familar with synchronous motor out-of-step protection relay GTM7111.
This relay has the following settings:
"S" setting which varies from 20% to 80% of Sq root(3)xInxV.
"Time delay" setting of 0.1 to 0.5sec.
Need to understand the concept of the PQ diagram.
Does anyone has articles...
Hi SWN1,
Thanks for the responds.
The recommendation in IEEE62.21 is to ground the shield on the switchgear end to reduce the surge. It was reported the surge can be reduced by 50% especially for long cable (greater than 100m).
This is also new to me... Our practice is also to ground both ends.
Hi,
Every motor should have its design voltage tolerance.
For my factory, our incoming voltage to the switchboard is 433V, but we always purchased motor that is 415V +/-10% voltage tolerance.
This is mainly to cater for voltage drop.
It has been our practise to ground both ends of the shields for 6.6kV motor feeders (i.e ground the shield on the controller or switchgear end as well as on the motor end). Most motor manufacturers will also recommend to ground both ends.
Does anyone know the reasons why we need to ground both...
Hi,
We have nearly one thousand 6.3kV motors. Nearly 95% of these motors use vacuum contactor. Most of the vacuum contactors come from the same vendor.
This is the first time, we have motor winding that fails in less than one year after re-winding.
In the past, we do have winding failure, but...
Hi,
Anyone familar with SKM captor program version 5.
I have a SKM file which contains the single line diagram with relay setting nicely drawn for 5 substations.
One of the substation was recently re-vamped and the single line diagram was drawn separated from the existing file.
Anyone know...
Hi,
I have checked with the vendor for my vacuum contactor.
Vacuum contactor since the 80s used low surge material on the contactor surface which basicially creates very low voltage surge that is very popular for motor starting/switching.
With such low surge, this type of vacuum contactor...
Hi jraef,
Thank U for your respond.
a. This motor is not operating on VFD. It starts on direct on-line starting.
b. We are using vacuum combination starter unit. The contactor rating is 400A whereas our FLA is 181A. Running ampere is approx. 97% (175A).
c. When you mentioned re-striking...
Hi,
Do you have the test voltage(DC) for 3.3kV cable?
I read in some articles which recommended the follow:
Test voltage (DC) = [(3.3kV * 2)+ 1kV] * 1.4
Cheers.
Yeo
Hello to electrical man,
I have a 1.2MW (6.3kV) motor which was re-wound last year (Oct05).
The winding was shorted again this year (Aug06) in less than ONE year after re-wound.
The shorted location is just a little dot near the winding overhung.
This motor did not show sign of overheating and...
