I'm evaluating the overcurrent settings of an ABB REF 543 relay.
I'm using the SKM software.
The 51 element has been set with an extremely inverse characteristic and, looking at the time current diagram, at high currents it should be faster than the 50 element. The SKM software doesn't show that...
I'm evaluating the possibility to join SEL.
I'm based in Europe.
What do you feel about the possibility to sell the SEL relays in the european market? I know their relays quite well from a technical point of view and I think they are impressive. I'm not sure about the commercial side here in...
Hi to everybody,
we should verify the CT dimensioning for a line differential Areva Miccom P521 device. The critical point is the stability for external faults. We are using class PX Cts
Is anybody aware of any special value "suggested" by Areva for the "Ktd" value? We found that Siemens for...
I should set in a industrial plant the 50N elements protecting many motors ranging from 300 kW to 4000 MW.
The system voltage is 11 kV and the ground current is limited to 600 A. The customer decided to use 50/1 cl 1 measurement (!)toroidal CT to feed the relay ground elemnts.
How sensitive can...
To verify the dimensioning of the CTs of a motor differential relay are usually checked both the stability for external faults and the relay trip for internal faults or only the stability?
If the bus bar where the motor is has a very high short circuit level (i.e. 35 kA at 11 KV close to the...
Hi to everybody!
I'm looking for a CT catalog for medium voltage. Do you know if anything is available on Internet?
Basically I would like to be sure that 5P20 30 and 40 VA CT are available for 11 kV systems.
Data regarding the secondary resistance could be interesting too.
Thank you in advance...
We have a 11 kV bus bar with about 14 MVA of loads (90% motors).
We got (customer data) the short circuit current values: 35 kA as Ikss (subtrans I)
I feel such value a bit too high. Also considering the motor contribution I was expecting 12-13 kA.
(assuming a 15 MVA 9% trafo feeding the system...
I was wondering which CT verification formula you are using.
I have to verify the CTs for many substations and I was going to use the formula showed in the attachment.
The "magic" Ktd factor seems to be:
Ktd = 1 for over current relays
Ktd = 1.2 for line differential relays
Ktd = 3 for trasf...
