Numerical Relays

[elecpl123]

Hi Guys,

In Numerical Relay defining star point what does it means
1.From object or towards object whether it influence protection operation.
2.why star point is also done towards protected equipment.

 

[slavag]

Hi Elecpl123.
We had here thread on the topic, but..don't remember when and where.

1. Star point isn't influence on the protection functionality ( except in the differential protection).
2. From this thread, I remember that lot of us use rule of tumb, star point towards protected object.
3. Reason..CT by temselves also in protected zone.

Best Regards.
Slava.
BTW, in newer relays, you can chenge polirity of each set CT's directly in the protection.

 

[davidbeach]

Relay polarity is important for anything that relies on directionality. Conventional definition of forward is toward the wye point of the CTs; since that is what relays expect and what technicians expect any changes are just asking for trouble.

 

[elecpl123]

Hi Slavag,

Thanks for your response can u explain in detail so that it will help me