Coordination time interval for electronically-controlled reclosers 2

[Mario53]

Hi there. I am trying to coordinate two electronically-controlled reclosers (e.g. ABB PCD2000). My question is what would be the minimum Coordination Time Interval for two electronically controlled reclosers considering that the downstream recloser curve already contains the manufacturer's maximum interrupting time and the upstream recloser curve is only the relay minimum response time?. I have used CTI>12 cycles for hydraulic reclosers as recommended by Cooper, but I haven't found any reference about equation-based reclosers.

In addition, if you could provide any reference I would appreciate it.

 

[cranky108]

What's wrong with 12 cycles? Do you believe the devices will be more or less likely to operate in the time outlined by the curves?

Besides, would you look to Cooper to make recommendations for a device made by ABB?

Or just ask ABB for the recommendation.

 

[Mario53]

Thanks for answer cranky. So when I said cooper I basically referred to the Electric Power Distribution Handbook, where 12 cycles are recommended. What I have seen in some literature is that a specific CTI range (or guideline) is recommended for hydraulic reclosers in spite of the manufacturer. What I want to know is if there is some sort of CTI or any criteria for coordinating two electronically controlled reclosers (forget about the manufacturer). Maybe I should not have mentioned ABB, but asked as a general question.

 

[protoslash]

between two relay response time, 200ms is recommended as general rule of thumb, if things are tight i wouldn't go below 150ms.

if you just compare downstream clearing time vs upstream response time, then 100ms should be good.

I agree with asking ABB for their maximum clearing time.

 

[Mario53]

Thanks, Protoslash. 100ms (6 cycles) sounds more reasonable for electronic reclosers.

 

[Fuse4]

I agree with protoslash, with the time of 150 ms, verify that opening mechanism is equal in both recloser and has the good opening speed conditions to avoid miscordination (low bateries produce slow opening conditions). In primary tests include the time of the relay and the mechanism and is a good measure of the total operation time

 

[RRaghunath]

150ms is the minimum recommended between fuses (downstream fuse to upstream fuse). This is in standard protection text books.
For electronic reclosers, can it be any lower than that for fuses??
I won't be comfortable with any thing lower than 200ms.

 

[protoslash]

then you need to find a better textbook.

"Maximum clearing time of the protecting link is no greater than 75% of the minimum melting time of the protected link"
-Electrical Distribution System Protection by Cooper Power System

see fuse coordination table here: Link
A 80K fuse can coordinate with 50K fuse up to 1250A. The margin between these two fuse at 1250A is less than 50ms yet it coordinates. This works because the higher the current the faster the fuse link melts, fuse do not have a constant time to melt thus no need for a constant margin.

A recloser is different because regardless of fault current, it takes a constant amount of time for the switch contact mechanism to open, therefore you need a constant margin like 200ms between devices. As modern reclosers get better, you can definitely go under a bit. see specs from G&W viper recloser, they advertised total clearing time of 46ms
Link

 

[Mario53]

Thank you all. Indeed I am considering the relay response time as outlined by the protection curve time plus 3 cycles (42 ms) as the provided manufacturer's maximum interrupting time for the downstream device. The resulting curve should reflect the overall clearing.

 

[davidbeach]

Last I checked 3 cycles was 50ms.

 

[RRaghunath]

Thanks for correcting me Protoslash.
About fuse coordination, you are right.
I meant Relay-to-fuse coordination margin of minimum 150ms (and not fuse-to-fuse).
Thanks once again.