Time Dial Setting

[devilskm]

Greetings

In the attached image I have set the time dial as 3 for the chiller relay curve. In Order to keep the Transformer curve (Transformer which is feeding this chiller), I have kept the time dial above the Chiller's. But the problem is that the settings I got from utility, the time dial is 0.65 for that. If I reduce the time dial for chiller, the curve comes below and to the left of starting curve.
How I can move the curve up and down with reduced time dial.I tried it with "Time Multiplier" but for any value other then 1 It takes the current markers out of TCC.

 

[cranky108]

Assumption 1: the utility is using a solid state relay.
Why is the utility providing this curve? Is this the curve they are using, or one they are expecting you to use?

Did you look at different familys of curves?
Is there a problem with your software?
What relay are we looking at?

We need more information.

 

[devilskm]

I am using VAMP-40 for Chiller feeder. The point which I want to make here, for chiller relay curve, the Time Dial is 3. The Low Voltage (380V) Switchgear for the chiller is fed by a Transformer (13.8kV/380V). For Pri and Sec side of this transformer, I am using VAMP-230. Since chiller is the largest load (525kW) for the Low Voltage Switchgear, so I have to coordinate it with the Incoming Transformer. In order to keep the Transformer LV side curve above and to the right of the Chiller's curve, I choosed a Time Dial of 3 for the Transformer LV side with VAMP-230. Again in order to keep the 13.8kV side curve of the transformer to the right and above of LV side, I choosed Time Dial of 5.
After I completed this study, I received the settings of incoming utility feeders. I am OK with the current setting of the Utility, but due to Time Dial of 0.65 for SEPAM1000 relay, the utility curve is below my Transformer 13.8kV side relay curve. What I should do to manage this?

 

[cranky108]

Working for a utility, it is common to see customers wanting curves very high, so this looks common. This should be an agreement between you and the utility. You squeese your curves, and they squeese theres to make this work.

The theory is that you have several transformers and load deversity. Or said another way, you won't have all your loads, or inrush conditions at the same time.

This condition becomes worse when devices are over sized with protection to match the device and not the real load expectation.

 

[jghrist]

I can't get the curves to open, but I assume that you are keeping the high side overcurrent relay above the low side. Is this necessary? Would you lose any selectivity if you made the high side overcurrent relay trip at the same time as the low side?

 

[devilskm]

How Important it is to do the relay settings manually before going for coordination on the software?
Secondly, In one of the document, I have, they recommend the type of curve for the equipments, e.g for Transformer they recommend Very inverse Curve. Does it really depends on the type of equipment or we can choose any type of curve?