SEL 351S Relay 67 versus 32 Element
SEL 351S Relay 67 versus 32 Element
(OP)
Folks,
SEL 351S Relay Settings started to confuse me, they use the 67 Directional Overcurrent element and the 32 Reverse Power element backward, in my opinion.
Have any of you worked or dealt with setting this kind of relay. My application is for dual-feed industrial substation and I want to set the Directional Element for that purpose but it is confusing me!!
If I only want to monitor the Direction of the current (not power) flow and trip in a pre-determined direction. Which one should I use and what about all these Reverse and Forward Impedance values they require?!
Any Insight, please.
SEL 351S Relay Settings started to confuse me, they use the 67 Directional Overcurrent element and the 32 Reverse Power element backward, in my opinion.
Have any of you worked or dealt with setting this kind of relay. My application is for dual-feed industrial substation and I want to set the Directional Element for that purpose but it is confusing me!!
If I only want to monitor the Direction of the current (not power) flow and trip in a pre-determined direction. Which one should I use and what about all these Reverse and Forward Impedance values they require?!
Any Insight, please.






RE: SEL 351S Relay 67 versus 32 Element
I'm not sure what you mean by the reverse and forward impedance values. Are you trying to set the load encroachment logic? This introduces a whole other set of complications.
Power elements (with Firmware Version 7) are designated with PWR and can be used for reverse power protection.
RE: SEL 351S Relay 67 versus 32 Element
The whole thing is very, very confusing!!
RE: SEL 351S Relay 67 versus 32 Element
The directional can be derived in several ways, Negative sequence, zero sequence current, or zero sequence voltage. You should choose on or more and make the settings that match (the relay won't ask for settings on things you turn off).
Z1F, and Z2F are thresholds which should not overlap. The book should have a recommend setting, or call SEL for help.
RE: SEL 351S Relay 67 versus 32 Element
RE: SEL 351S Relay 67 versus 32 Element
If it's any consolation, you're not alone. The SEL-351 is one of more difficult relays to work with - due to the odd SEL terminology used, the "rich feature set", and inconsistencies when compared with other SEL products.
It's a very capable relay and we use them quite a bit, but it is not easy to work with.
"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller
RE: SEL 351S Relay 67 versus 32 Element
The 67 elements are directional when E32 is enabled, and non-directional when not. The difference between a 67 element and the corresponding 50 element can be found in the logic diagram in the instruction manual. Make sure you note how LOP plays in.
Also, please understand that the directional logic is intended for looking at the direction of a fault (primarily reactive). Reverse real power flow under un-faulted conditions is a whole different matter entirely, and the directional elements may not be suitable.
RE: SEL 351S Relay 67 versus 32 Element
Thanks again and best regards to all
RE: SEL 351S Relay 67 versus 32 Element