Any Multilin 750 guru's out there??? 1

[crank71]

We have a SR750 relay that when tripped activates an 86 lockout relay. Problem being that when the utility experiences a system sag, we go down on undervoltage or loss of phase and have to send an operator out to manually reset the 86. Ideally we want to have the 750 initiate a 86 lockout except when seeing an undervoltage/phase loss condition. In those situations we just want to trip the breaker and allow for remote re-close. Our schematic shows that the 86 coil and the breaker trip coil are in parallel so I think we'll have to change that and possibly assign the undervoltage and phase loss functions to a different 750 output that trips the breaker trip coil only??? and then have all other trips going to the 86 with a set of contacts in the breaker trip coil circuit....any other ideas much appreciated.

 

[dpc]

I'm going to assume the overvoltage trip is coming from the SR-750.

With most digital relays, this would be pretty straightforward, but the SR-750 is a little more primitive and has the TRIP output contact logic pretty well pre-defined. It is not possible to remove the Undervoltage TRIP function from the TRIP output contact if it is enabled.

However, if you change the Undervoltage Function to ALARM instead of TRIP, you should then be able to also implement a parallel tripping function using one of the auxiliary output contacts. This auxiliary contact can then be wired to breaker trip coil instead of the 86 relay.

I think this will work, but you should obviously test it first.

I don't think you should need a second relay.

The configuration software is available for free from the GE website. For each output contact, you can select which functions it is controlled by. The SR-750 manual is also available by section on the GE website.

http://www.geindustrial.com/cwc/products?pnlid=6&famid=31&catid=216&id=750&lang=en_US

Hope that helps.

 

[busbar]

 
Before changes are made that affect trip levels or modify protection logic, it may be wise to test the relay to determine it is operating at assigned values, and determine the original rationale for the features wanting modification.

Will the served equipment’s longer-term performance be affected, or will the connected utility system be impacted by the change? Some relay settings and trip logic are part of contractual obligations.